U.S. patent application number 15/295336 was filed with the patent office on 2017-04-06 for production of partially refined waste glycerol.
The applicant listed for this patent is REG Life Sciences, LLC. Invention is credited to Myong Ko, Simon LI, Perry LIAO, Fernando Sanchez-Riera.
Application Number | 20170096379 15/295336 |
Document ID | / |
Family ID | 55347704 |
Filed Date | 2017-04-06 |
United States Patent
Application |
20170096379 |
Kind Code |
A1 |
Ko; Myong ; et al. |
April 6, 2017 |
PRODUCTION OF PARTIALLY REFINED WASTE GLYCEROL
Abstract
The disclosure relates to a novel glycerol purification process
that produces partially refined waste glycerol for a variety of
industrial applications. The disclosure encompasses a
salt-containing partially refined glycerol composition that is
suitable as a fermentation grade glycerol.
Inventors: |
Ko; Myong; (San Mateo,
CA) ; LIAO; Perry; (Daly City, CA) ; LI;
Simon; (San Francisco, CA) ; Sanchez-Riera;
Fernando; (San Carlos, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
REG Life Sciences, LLC |
Ames |
IA |
US |
|
|
Family ID: |
55347704 |
Appl. No.: |
15/295336 |
Filed: |
October 17, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14463635 |
Aug 19, 2014 |
9469586 |
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15295336 |
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61867473 |
Aug 19, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C07C 31/225 20130101;
C11D 19/00 20130101; C07C 29/86 20130101; C07C 31/225 20130101;
C07C 29/86 20130101 |
International
Class: |
C07C 29/86 20060101
C07C029/86; C07C 31/22 20060101 C07C031/22 |
Claims
1.-28. (canceled)
29. A partially refined waste glycerol produced by a process
comprising: subjecting crude glycerol to a hydrophobic solvent to
produce a mixture of crude glycerol and hydrophobic solvent, and
separating the mixture of crude glycerol and hydrophobic solvent to
produce a deoiled (DO) glycerol and a phase containing hydrophobic
solvent and organic impurities.
30.-31. (canceled)
32. The partially refined waste glycerol of claim 29, wherein said
partially refined waste glycerol comprises reduced salt and organic
impurities as compared to a crude glycerol.
33. The partially refined waste glycerol of claim 32, wherein said
partially refined waste glycerol comprises a sodium chloride
content from between about 0.05 percent to about 8.2 percent.
34. The partially refined waste glycerol of claim 32, wherein said
partially refined waste glycerol comprises a sodium chloride
content from between about 0.05 percent to about 3.5 percent.
35. The partially refined waste glycerol of claim 32, wherein said
partially refined waste glycerol comprises a sodium chloride
content from between about 0.05 percent to about 2.0 percent.
36. The partially refined waste glycerol of claim 32, wherein said
partially refined waste glycerol comprises a sodium chloride
content from between about 0.05 percent to about 1.0 percent.
37. The partially refined waste glycerol of claim 32, wherein said
partially refined waste glycerol is a fermentation grade
glycerol.
38.-55. (canceled)
Description
FIELD
[0001] The disclosure relates to a novel glycerol purification
process that produces partially refined waste glycerol for a
variety of industrial applications. Herein, the disclosure
encompasses a salt-containing partially refined glycerol
composition that is suitable as a fermentation grade glycerol.
BACKGROUND
[0002] Biodiesel is a natural and renewable domestic fuel
alternative for diesel engines made from vegetable oils and fats.
Because it is nontoxic and biodegradable it has become a promising
alternative to fuels made from petroleum. Biodiesel burns clean.
Thus, it results in a significant reduction of the types of
pollutants that contribute to smog and global warming. Biodiesel
emits up to 85 percent fewer cancer-causing agents and is the only
alternate fuel approved by the Environmental Protection Agency
(EPA). It has passed every Heath-Effects Test of the Clean Air Act
and meets the requirements of the California Air Resources Board
(CARB). Although, biodiesel is still relatively costly to make, the
utilization of its co-product glycerol is one of the promising
options for off-setting the biodiesel production cost.
[0003] Glycerol has more than 1500 known applications in many
different industries ranging from foods, pharmaceuticals, and
cosmetics (i.e., USP grade glycerol) to paints, coatings and other
industrial types of uses (i.e., technical grade glycerol). It is
the most versatile and valuable by-product created during biodiesel
production. One gallon of biodiesel generates about 1.05 pounds of
crude glycerol. A 30-million-gallon-per-year plant generates about
11,500 tons of 99.9 percent pure glycerol. It is speculated that
the world market will generate approx. 37 billion gallons of
biodiesel by 2016, suggesting a production of 4 billion gallons or
16.5 million metric tons of crude glycerol. This is believed to
create too much of a crude glycerol surplus which may negatively
impact the refined glycerol market (Yang et al. (2012)
Biotechnology for Biofuels 5:13). According to the EPA, this impure
form of glycerol must be disposed of within a certain period of
time, leading to high disposal fees for companies that produce
glycerol as a by-product. Hence, the development of sustainable
methods for utilizing raw organic glycerol is desirable while it is
equally desirable not to offset the balance of crude to refined
product.
[0004] Most biodiesel productions use homogeneous alkaline
catalysts such as sodium methylate. The transesterification of
triacylglycerides with methanol creates a methyl-ester phase and a
glycerol phase. Impurities, including catalyst, soap, methanol and
water are usually concentrated in the glycerol phase. The glycerol
phase is generally neutralized with acid and the cationic component
of the catalyst is incorporated as a salt. Thus, it is not uncommon
that glycerol, as a by-product of the biodiesel production, has a
salt content of 5 to 7 percent. This high salt content makes
conventional purification techniques cost intensive. There are
various methods for purifying crude glycerol, including fractional
distillation, membrane technology employing a series of NF and RO
membrane stages (NF/RO membrane), electro-dialysis membrane
technology (electro-dialysis membrane), bipolar membrane technology
(bi-polar membrane), and ion-exchange resin adsorption technology
(ion-exchange resin adsorption). Fractional distillation is the
most commonly practiced method. It results in high purity glycerol
at high yields, however, it is also capital-, labor-, and
energy-intensive. Glycerol has a high heat capacity and, thus,
requires a high-energy input for vaporization. Another common
technique for glycerol purification is the classical ion-exchange
method. But the higher salt content of glycerol as a result of
biodiesel production makes classical ion-exchange an uneconomical
choice. Particularly, the chemical regeneration cost for the resins
becomes too high when the salt content in glycerol approaches 5 to
7 percent.
[0005] Most methods that are used to purify glycerol are based on
aqueous technologies that use crude glycerol water, i.e., they use
glycerol that contains about 60 to 70 percent water as a feed.
Fractional distillation refines glycerol by using crude glycerol
that contains about 6 to 8 percent water that has gone through
methanol rectification and water evaporation. Amongst all the
available technologies, the electro-dialysis membrane, bi-polar
membrane and ion-exchange resin adsorption are mainly desalting
processes. They all require separate deoiling (i.e., de-oiling)
process steps and generate large amounts of waste water. The
ion-exchange resin adsorption method is mainly used for low salt
polishing applications. The NF/RO membrane uses a multi-stage
membrane unit for the glycerol refining process that is capable of
both desalting and deoiling the glycerol.
[0006] There are also hybrid systems for purifying crude glycerol.
For example, a hybrid system for purifying glycerol can employ a
membrane technology as a main process and distillation as a minor
process, wherein both can recover glycerol in so-called concentrate
and permeate streams. In that type of system, the concentrate
stream contains dirty glycerol water while a permeate stream
contains cleaner glycerol water. The glycerol contained within the
concentrate streams can be recovered or discharged as a loss. Each
stage that contains a permeate stream in a process that applies any
of the membrane technologies (i.e., a membrane process) contains
glycerol-water intermediates with reduced salt and reduced
organics. Each stage that contains a concentrate stream in a
membrane process contains glycerol, water, concentrated salt and
concentrated organic impurities. Fractional distillation can also
be used in a hybrid system. Fractional distillation is similar to a
membrane system in that it is capable of desalting and deoiling the
glycerol but it relies on continuous salt removal under high
vacuum. A hybrid system employing fractional distillation recovers
glycerol in the concentrate stream of the membrane process.
[0007] Although, both fractional distillation and NF/RO membrane
produce glycerol suitable for fermentation, the high production
cost creates a down side. Currently, the majority of large
industrial commercial processes employ fractional distillation. The
equipment cost of fractional distillation of crude glycerol is high
due to the need of continuous salt removal under high vacuum (see,
e.g., Glycerine a Key Cosmetic Ingredient, Cosmetic Science and
Technology Series (1991) by Marcel Dekker, Inc; and Bailey's
Industrial Oil and Fat Products, Sixth Edition, Six Volume Set
(2005) by John Wiley and Sons, Inc.).
[0008] Purified or refined glycerol (i.e., USP grade glycerol) has
numerous applications from fragrances to cosmetics to
pharmaceuticals and is a valued commercial product. The production
of purified glycerol is costly because the majority of existing
methods of purification employ fractional distillation (supra).
However, USP grade glycerol is not suitable for all applications
because it is simply too costly to manufacture and unnecessarily
pure for industrial applications (e.g., paints, coats, adhesives,
etc.). Technical grade glycerol is more suitable for industrial
applications but its production also relies on fractional
distillation and it is therefore not a cost-effective alternative.
Thus, a method is needed that produces a form of technical grade
glycerol at a low enough cost that is acceptable for industrial
applications. In addition, there is a need for a new form of
technical grade glycerol with characteristics that meet the
specifications required for renewable methods and bio-degradable
products that reach beyond those that rely mostly on refined or
crude glycerol. The present disclosure addresses this need.
SUMMARY
[0009] One aspect of the disclosure provides a process of producing
partially refined waste glycerol by refining crude glycerol
containing organic impurities, wherein the process includes
deoiling using a hydrophobic solvent to extract the organic
impurities; dewatering by drying at an elevated temperature; and
desalting using a polar solvent to precipitate salt.
[0010] Another aspect of the disclosure provides a process of
producing partially refined waste glycerol by refining crude
glycerol containing organic impurities, wherein the process
includes subjecting the crude glycerol to a hydrophobic solvent to
produce a mixture of crude glycerol and hydrophobic solvent; and
separating the mixture of crude glycerol and hydrophobic solvent to
produce a deoiled (DO) glycerol and a phase containing hydrophobic
solvent and organic impurities. In one aspect, the process further
includes the step of drying the DO glycerol to produce a deoiled
and dewatered (DOW) glycerol. In another aspect, the process
further includes the steps of subjecting a polar solvent to the DOW
glycerol to produce a mixture of polar solvent and DOW glycerol and
precipitating salt from the mixture of polar solvent and DOW
glycerol; and separating the mixture of polar solvent and DOW
glycerol into a light phase containing a deoiled, dewatered and
desalted (DOWS) glycerol and the polar solvent and a heavy phase
containing the salt. In another aspect, the process further
includes the step of removing the polar solvent from the light
phase to produce a purified DOWS glycerol. In another aspect, the
process further includes the step of partially evaporating the DOW
glycerol before subjecting it to the polar solvent. In one
embodiment, the DOWS glycerol is fermentation grade glycerol. In
another embodiment, the fermentation grade glycerol is
salt-containing glycerol. In another embodiment, the hydrophobic
solvent is selected from triacylglyceride, alkane, alkene, acetate,
and/or fatty acid alcohol ester. In still another embodiment, the
triacylglyceride is vegetable oil. In still another embodiment, the
acetate is butyl acetate. In yet another embodiment the alkane is
hexane. In another embodiment the process includes organic
impurities that are oil-soluble. In one embodiment, the DO glycerol
includes less than about 195 ppm oil-soluble organic impurities. In
another embodiment, the DOW glycerol includes less than about 0.5
percent water. In another embodiment, the polar solvent is alcohol.
In one embodiment, the alcohol is isopropanol or butanol. In
another embodiment, the step of removing the polar solvent is done
by flash evaporation.
[0011] Another aspect of the disclosure provides a process of
producing partially refined waste glycerol by refining crude
glycerol containing organic impurities, wherein the process
includes subjecting the crude glycerol to a hydrophobic solvent to
produce a mixture of crude glycerol and hydrophobic solvent; and
separating the mixture of crude glycerol and hydrophobic solvent to
produce a deoiled (DO) glycerol and a phase containing hydrophobic
solvent and organic impurities. In one aspect, the process further
includes the steps of subjecting a polar solvent to the DO glycerol
to produce a mixture of polar solvent and DO glycerol and
precipitating salt from the mixture of polar solvent and DO
glycerol; and separating the mixture of polar solvent and DO
glycerol into a light phase containing a deoiled and desalted
glycerol and the polar solvent and a heavy phase containing the
salt. In another aspect, the process further includes the step of
drying said deoiled and desalted glycerol to produce a deoiled,
desalted and dewatered (DOWS) glycerol. In one embodiment, the DOWS
glycerol is fermentation grade glycerol. In another embodiment, the
fermentation grade glycerol is salt-containing glycerol. In another
embodiment, the hydrophobic solvent is selected from
triacylglyceride, alkane, alkene, acetate, and/or fatty acid
alcohol ester. In still another embodiment, the triacylglyceride is
vegetable oil. In still another embodiment, the acetate is butyl
acetate. In yet another embodiment the alkane is hexane. In another
embodiment the process includes organic impurities that are
oil-soluble. In one embodiment, the DO glycerol includes less than
about 195 ppm oil-soluble organic impurities. In another
embodiment, the DOW glycerol includes less than about 0.5 percent
water. In another embodiment, the polar solvent is alcohol. In one
embodiment, the alcohol is isopropanol or butanol. In another
embodiment, the step of removing the polar solvent is done by flash
evaporation.
[0012] The disclosure further contemplates a process as described
above (supra) that further includes the step of tailoring the salt
content of a fermentation grade glycerol. In one embodiment, the
process includes tailoring the salt content of a fermentation grade
glycerol to between about 0.05 to about 8.2 percent salt. In
another embodiment, the process includes tailoring the salt content
of a fermentation grade glycerol to between about 0.05 to about 3.5
percent salt. In another embodiment, the process includes tailoring
the salt content of a fermentation grade glycerol to between about
0.05 to about 1.0 percent salt.
[0013] Another aspect of the disclosure provides a process of
producing partially refined waste glycerol by refining crude
glycerol containing organic impurities, wherein the process
includes subjecting the crude glycerol to a hydrophobic solvent to
produce a mixture of crude glycerol and hydrophobic solvent; and
separating the mixture of crude glycerol and hydrophobic solvent to
produce a deoiled (DO) glycerol and a phase containing hydrophobic
solvent and organic impurities. In one embodiment, the separation
occurs by at least one of gravity decantation, hydrocyclone
separation, and/or centrifugal separation. In one aspect, the
process further includes the step of heating the mixture of crude
glycerol and hydrophobic solvent. In one embodiment, the process
includes the step of heating the mixture of crude glycerol and
hydrophobic solvent to between about 20.degree. C. to about
95.degree. C. In another embodiment, the process includes the step
of heating the mixture of crude glycerol and hydrophobic solvent to
between about 55.degree. C. to about 65.degree. C. In another
aspect, the process further includes the step of mixing the mixture
of crude glycerol and hydrophobic solvent. In one embodiment, the
process includes the step of mixing the mixture of crude glycerol
and hydrophobic solvent for between about 5 minutes to about 30
minutes.
[0014] Another aspect of the disclosure provides a process of
producing partially refined waste glycerol by refining crude
glycerol containing organic impurities, wherein the process
includes subjecting the crude glycerol to a hydrophobic solvent to
produce a mixture of crude glycerol and hydrophobic solvent; and
separating the mixture of crude glycerol and hydrophobic solvent to
produce a deoiled (DO) glycerol and a phase containing hydrophobic
solvent and organic impurities. In one aspect, the process further
includes the step of drying the DO glycerol to produce a deoiled
and dewatered (DOW) glycerol. In one embodiment, the drying occurs
at between about 60.degree. C. to about 130.degree. C.
[0015] The disclosure further contemplates a product produced by
the above described processes (supra). In one aspect, the
disclosure provides a product produced by a process of producing
partially refined waste glycerol by refining crude glycerol
containing organic impurities, wherein the process includes
deoiling using a hydrophobic solvent to extract the organic
impurities; dewatering by drying at an elevated temperature; and
desalting using a polar solvent to precipitate salt. In another
aspect, the disclosure provides a product produced by a process of
producing partially refined waste glycerol by refining crude
glycerol containing organic impurities, wherein the process
includes subjecting the crude glycerol to a hydrophobic solvent to
produce a mixture of crude glycerol and hydrophobic solvent; and
separating the mixture of crude glycerol and hydrophobic solvent to
produce a deoiled (DO) glycerol and a phase containing hydrophobic
solvent and organic impurities. In another aspect, the disclosure
provides a product produced by a process of producing partially
refined waste glycerol by refining crude glycerol containing
organic impurities, wherein the process includes subjecting the
crude glycerol to a hydrophobic solvent to produce a mixture of
crude glycerol and hydrophobic solvent; separating the mixture of
crude glycerol and hydrophobic solvent to produce a deoiled (DO)
glycerol and a phase containing hydrophobic solvent and organic
impurities; and drying the DO glycerol to produce a deoiled and
dewatered (DOW) glycerol. In another aspect, the disclosure
provides a product produced by a process of producing partially
refined waste glycerol by refining crude glycerol containing
organic impurities, wherein the process includes subjecting the
crude glycerol to a hydrophobic solvent to produce a mixture of
crude glycerol and hydrophobic solvent; separating the mixture of
crude glycerol and hydrophobic solvent to produce a deoiled (DO)
glycerol and a phase containing hydrophobic solvent and organic
impurities; drying the DO glycerol to produce a deoiled and
dewatered (DOW) glycerol; subjecting a polar solvent to the DOW
glycerol to produce a mixture of polar solvent and DOW glycerol and
precipitating salt from the mixture of polar solvent and DOW
glycerol; and separating the mixture of polar solvent and DOW
glycerol into a light phase containing a deoiled, dewatered and
desalted (DOWS) glycerol and the polar solvent and a heavy phase
containing the salt. In another aspect, the disclosure provides a
product produced by a process of producing partially refined waste
glycerol by refining crude glycerol containing organic impurities,
wherein the process includes subjecting the crude glycerol to a
hydrophobic solvent to produce a mixture of crude glycerol and
hydrophobic solvent; separating the mixture of crude glycerol and
hydrophobic solvent to produce a deoiled (DO) glycerol and a phase
containing hydrophobic solvent and organic impurities; drying the
DO glycerol to produce a deoiled and dewatered (DOW) glycerol;
subjecting a polar solvent to the DOW glycerol to produce a mixture
of polar solvent and DOW glycerol and precipitating salt from the
mixture of polar solvent and DOW glycerol; separating the mixture
of polar solvent and DOW glycerol into a light phase containing a
deoiled, dewatered and desalted (DOWS) glycerol and the polar
solvent and a heavy phase containing the salt; and removing the
polar solvent from the light phase to produce a purified DOWS
glycerol.
[0016] The disclosure further encompasses as partially refined
waste glycerol derived from the processing of natural fats and
oils, wherein the partially refined waste glycerol has reduced salt
and/or organic impurities as compared to a crude glycerol. In one
embodiment, the partially refined waste glycerol includes a sodium
chloride content from between about 0.05 percent to about 8.2
percent. In another embodiment, the partially refined waste
glycerol includes a sodium chloride content from between about 0.05
percent to about 3.5 percent. In another embodiment, the partially
refined waste glycerol includes a sodium chloride content from
between about 0.05 percent to about 2.0 percent. In still another
embodiment, the partially refined waste glycerol includes a sodium
chloride content from between about 0.05 percent to about 1.0
percent. In another embodiment, the partially refined waste
glycerol is a fermentation grade glycerol.
[0017] Another aspect of the disclosure provides a process of
producing partially refined waste glycerol by refining crude
glycerol containing organic impurities, wherein the process
includes drying the crude glycerol to produce a dewatered glycerol;
subjecting the dewarered glycerol to a hydrophobic solvent to
produce a mixture of dewatered glycerol and hydrophobic solvent;
and separating the mixture of dewatered glycerol and hydrophobic
solvent to produce a deoiled dewatered (DOW) glycerol and a phase
containing hydrophobic solvent and organic impurities. In one
aspect, the process further includes the steps of subjecting a
polar solvent to the DOW glycerol to produce a mixture of polar
solvent and DOW glycerol and precipitating salt from the mixture of
polar solvent and DOW glycerol; and separating the mixture of polar
solvent and DOW glycerol into a light phase containing a deoiled,
dewatered and desalted (DOWS) glycerol and the polar solvent and a
heavy phase containing the salt.
[0018] Another aspect of the disclosure provides a process of
producing partially refined waste glycerol by refining crude
glycerol containing organic impurities, wherein the process
includes drying the crude glycerol to produce a dewatered glycerol;
subjecting a polar solvent to the dewatered glycerol to produce a
mixture of polar solvent and dewatered glycerol and precipitating
salt from the mixture of polar solvent and dewatered glycerol; and
separating the mixture of polar solvent and dewatered glycerol into
a light phase containing a dewatered and desalted glycerol and the
polar solvent and a heavy phase containing the salt. In one aspect,
the method further includes the steps of subjecting the dewatered
and desalted glycerol to a hydrophobic solvent to produce a mixture
of dewatered and desalted glycerol and hydrophobic solvent; and
separating the mixture of dewatered and desalted glycerol and
hydrophobic solvent to produce a dewatered, desalted, and deoiled
(DOWS) glycerol and a phase containing hydrophobic solvent and
organic impurities.
[0019] Another aspect of the disclosure provides a process of
producing partially refined waste glycerol by refining crude
glycerol containing organic impurities, wherein the process
includes subjecting a polar solvent to the crude glycerol to
produce a mixture of polar solvent and crude glycerol and
precipitating a salt from the mixture of polar solvent and crude
glycerol; and separating the mixture of polar solvent and crude
glycerol into a light phase containing desalted glycerol and the
polar solvent and a heavy phase containing the salt. In one aspect,
the process further includes the steps of subjecting the desalted
glycerol to a hydrophobic solvent to produce a mixture of desalted
glycerol and hydrophobic solvent; and separating the mixture of
desalted glycerol and hydrophobic solvent to produce a deoiled
desalted glycerol and a phase containing hydrophobic solvent and
organic impurities. In another aspect, the process further includes
the step of drying the deoiled desalted glycerol to produce a
desalted, deoiled, and dewatered (DOWS) glycerol.
[0020] The disclosure further contemplates a process of refining
crude glycerol, including combining crude glycerol with a
hydrophobic solvent to remove organic impurities and produce a
deoiled (DO) glycerol; drying the DO glycerol to produce a deoiled
and dewatered (DOW) glycerol; and subjecting a polar solvent to the
DOW glycerol to precipitate salt and produce a deoiled, dewatered
and desalted (DOWS) glycerol.
[0021] Another aspect of the disclosure provides a process of
producing partially refined waste glycerol by refining crude
glycerol containing organic impurities, wherein the process
includes subjecting a crude glycerol to a hydrophobic solvent to
produce a mixture of crude glycerol and hydrophobic solvent;
separating the mixture of crude glycerol and hydrophobic solvent to
produce a deoiled (DO) glycerol and a phase containing hydrophobic
solvent and organic impurities; drying the DO glycerol to produce a
deoiled and dewatered (DOW) glycerol; subjecting a polar solvent to
the DOW glycerol to produce a mixture of polar solvent and DOW
glycerol and precipitating a salt from the mixture of polar solvent
and DOW glycerol; and separating the mixture of polar solvent and
DOW glycerol into a light phase containing a deoiled, dewatered and
desalted (DOWS) glycerol and the polar solvent and a heavy phase
containing the salt. In another aspect, the process further
includes partially evaporating the DOW glycerol before subjecting
it to the polar solvent. In another aspect, the process further
includes the step of evaporating the polar solvent from the DOWS
glycerol to produce a purified DOWS glycerol. In one embodiment,
the evaporation is flash evaporation. In one embodiment, the DOW
glycerol has less than about 0.5 percent water. In another
embodiment, the DOWS glycerol is a fermentation grade glycerol. In
still another embodiment, the fermentation grade glycerol is
salt-containing glycerol.
[0022] The disclosure further encompasses a process of refining
crude glycerol, including combining crude glycerol with a
hydrophobic solvent to remove organic impurities and create a
deoiled (DO) glycerol; drying the DO glycerol to create a deoiled
and dewatered (DOW) glycerol; partially evaporating about 75
percent of the DOW glycerol as a glycerol distillate without salt;
recovering a remaining portion of said DOW glycerol in an
evaporation discharge bottom; and adding a polar solvent to the
evaporation discharge bottom to precipitate salt and create a
deoiled, dewatered and desalted (DOWS) glycerol. In one embodiment,
the polar solvent is IPA.
[0023] Another aspect of the disclosure provides a process of
producing partially refined waste glycerol, including combining
crude glycerol with a hydrophobic solvent to remove organic
impurities and create a deoiled (DO) glycerol, wherein the DO
glycerol encompasses partially refined waste glycerol. In one
embodiment, the process further includes drying the DO glycerol to
create a deoiled and dewatered (DOW) glycerol. In another
embodiment, the process further includes adding a polar solvent to
the DOW glycerol to precipitate salt and create a deoiled,
dewatered and desalted (DOWS) glycerol. In one embodiment, the DOWS
glycerol includes fermentation grade glycerol. In further
embodiments, the order of the deoiling process steps, the
dewatering process steps, and the desalting process steps differ
from the above described process of DO.fwdarw.DOW.fwdarw.DOWS. In
yet another embodiment, the hydrophobic solvent includes, but is
not limited to, triacylglyceride, alkane, alkene, acetate, fatty
acid alcohol ester. In one embodiment, the triacylglyceride is
vegetable oil or fat. In another embodiment, the hydrophobic
solvent is acetate. In another embodiment, the acetate is butyl
acetate, or ethyl acetate. In yet another embodiment, the alkane is
hexane. In still another embodiment, the organic impurities are
oil-soluble. In another embodiment, the oil-soluble organic
impurities are removed through liquid-liquid extraction with the
hydrophobic solvent. In another embodiment, the DO glycerol
includes less than about 195 ppm oil-soluble organic impurities. In
another embodiment, the DOW glycerol includes less than about 0.5
percent water. In yet another embodiment, the polar solvent is an
alcohol. In one embodiment, the polar solvent is isopropanol or
butanol. In another embodiment, the salt is precipitated through
extraction with the polar solvent. In another embodiment, the
process further includes partial glycerol evaporation prior to the
extraction with the polar solvent. In another embodiment, the
process further includes evaporation of the polar solvent from the
mixture of glycerol and solvent and desolventizing the wet
precipitated salt. In one embodiment, the evaporation is flash
evaporation. In another embodiment, the fermentation grade glycerol
is salt-containing glycerol. In another embodiment, the
fermentation grade glycerol includes a tailored salt content from
about 0.05 to about 8.2 percent salt. In another embodiment, the
fermentation grade glycerol includes a tailored salt content from
about 0.05 to about 3.5 percent salt. In still another embodiment,
the fermentation grade glycerol includes a tailored salt content
from about 0.05 to about 2.0 percent salt. In one embodiment, the
fermentation grade glycerol includes a tailored salt content from
about 0.05 to about 1.0 percent salt.
[0024] Another aspect of the disclosure contemplates a partially
refined waste glycerol derived from the processing of natural fats
and oils, wherein the partially refined waste glycerol includes
reduced salt and/or organic impurities as compared to crude
glycerol. In one embodiment, the partially refined waste glycerol
has a sodium chloride content. In another embodiment, the partially
refined waste glycerol includes a sodium chloride content from
about 0.05 percent to about 8.2 percent. In another embodiment, the
partially refined waste glycerol includes a sodium chloride content
from about 0.05 percent to about 3.5 percent. In another
embodiment, the partially refined waste glycerol includes a sodium
chloride content from about 0.05 percent to about 2.0 percent. In
yet another embodiment, the partially refined waste glycerol
includes a sodium chloride content from about 0.05 percent to about
1.0 percent. In still another embodiment, the partially refined
waste glycerol is a fermentation grade glycerol.
[0025] Another aspect of the disclosure provides a process of
refining crude glycerol, including: combining crude glycerol with a
hydrophobic solvent to remove organic impurities and create a
deoiled (DO) glycerol; drying the DO glycerol to create a deoiled
and dewatered (DOW) glycerol; and adding a polar solvent to the DOW
glycerol to precipitate salt and create a deoiled, dewatered and
desalted (DOWS) glycerol. In one embodiment, the DO glycerol
comprises partially refined waste glycerol. In another embodiment,
the DOWS glycerol further includes fermentation grade glycerol. The
hydrophobic solvent includes, but is not limited to,
triacylglyceride, alkane, alkene, acetate, fatty acid alcohol
ester, and the like. In one embodiment, the triacylglyceride is
vegetable oil. In another embodiment, the acetate is butyl acetate.
In another embodiment, the alkane is hexane. In yet another
embodiment, the organic impurities are oil-soluble. In yet another
embodiment, the oil-soluble organic impurities are removed through
liquid-liquid extraction with the hydrophobic solvent. In one
embodiment, the DO glycerol includes less than about 195 ppm
oil-soluble organic impurities. In another embodiment, DOW glycerol
includes less than about 0.5 percent water. In other embodiment,
the polar solvent is an alcohol such as isopropanol or butanol. In
another embodiment, the salt is precipitated through extraction
with a polar solvent. In another embodiment, the process further
includes partial glycerol evaporation prior to said extraction with
said polar solvent. In still another embodiment, the process
includes evaporation and desolventizing with said polar solvent. In
a further embodiment, the process includes evaporation that is
flash evaporation. In yet another embodiment, the fermentation
grade glycerol is salt-containing glycerol.
[0026] The present disclosure further encompasses a process of
refining crude glycerol, including: combining crude glycerol with a
hydrophobic solvent to remove organic impurities and create a
deoiled (DO) glycerol; drying the DO glycerol to create a deoiled
and dewatered (DOW) glycerol; partially evaporating about 75
percent of the DOW glycerol as a glycerol distillate without salt;
recovering a remaining portion of the DOW glycerol in an
evaporation discharge bottom, wherein the remaining portion of the
DOW glycerol is about 25 percent; and adding a polar solvent to
said evaporation discharge bottom to precipitate salt and create a
deoiled, dewatered and desalted (DOWS) glycerol. In one embodiment,
the polar solvent is isopropyl alcohol (IPA).
[0027] Another aspect of the disclosure contemplates a process of
producing or precipitating salt, including combining crude glycerol
with a hydrophobic solvent to remove organic impurities and create
a deoiled (DO) glycerol; drying the DO glycerol to create a deoiled
and dewatered (DOW) glycerol; and adding a polar solvent to the DOW
glycerol to precipitate salt and create a deoiled-, dewatered- and
desalted (DOWS) glycerol, wherein the precipitated salt is produced
as a by-product. The precipitated salt includes, but is not limited
to, sodium chloride (NaCl), sodium sulfate (Na.sub.2SO.sub.4),
sodium phosphate (Na.sub.3PO.sub.4), sodium nitrate (NaNO.sub.3),
sodium acetate (C.sub.2H.sub.3NaO.sub.2), sodium carbonate
(Na.sub.2CO.sub.3), sodium formate (HCOONa), sodium lactate
(C.sub.3H.sub.5NaO.sub.3), sodium gluconate
(C.sub.6H.sub.11NaO.sub.7), sodium citrate
(C.sub.6H.sub.5Na.sub.3O.sub.7), sodium methanesulfonate
(CH.sub.3NaO.sub.3S), potassium chloride (KCl), potassium sulfate
(K.sub.2SO.sub.4), potassium phosphate (K.sub.3PO.sub.4), potassium
nitrate (KNO.sub.3), potassium acetate (CH.sub.3CO.sub.2K),
potassium carbonate (K.sub.2CO.sub.3), potassium formate
(CHKO.sub.2), potassium lactate (C.sub.3H.sub.5KO.sub.3), potassium
gluconate (C.sub.6H.sub.11KO.sub.7), potassium citrate
(C.sub.6H.sub.5K.sub.3O.sub.7), and potassium methanesulfonate
(CH.sub.3KO.sub.3S).
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The present disclosure is best understood when read in
conjunction with the accompanying figures, which serve to
illustrate the embodiments. It is understood, however, that the
disclosure is not limited to the specific embodiments disclosed in
the figures.
[0029] FIGS. 1A and 1B (FIG. 1A and FIG. 1B) depict block flow
diagrams showing five differing embodiments of the process for
producing partially refined waste glycerol from crude glycerol.
[0030] FIG. 2 (FIG. 2) is a block flow diagram showing one
embodiment of the present disclosure. Herein, FIG. 2 depicts a
block diagram of a production cycle for making partially refined
waste glycerol, including salt-containing fermentation grade
glycerol, wherein the steps encompass deoiling, dewatering and
desalting glycerol. The process includes hydrophobic solvent
liquid-liquid extraction through the use of triacylglycerides
(TAG); moisture drying; polar solvent extraction, polar solvent
evaporation, and polar solvent desolventizing. Isopropanol (IPA) is
shown as the polar solvent, which is reused in this process.
[0031] FIG. 3 (FIG. 3) is a block flow diagram showing another
embodiment of the present disclosure. Herein, FIG. 3 depicts a
block diagram of a production cycle for making partially refined
waste glycerol, including salt-containing fermentation grade
glycerol, wherein the steps encompass deoiling, dewatering and
desalting glycerol. The process includes hydrophobic solvent
liquid-liquid extraction through the use of alkanes, alkenes,
alcohol esters or acetates (hexane is shown here), wherein the
hydrophobic solvent is evaporated (e.g., through flash evaporation)
and reused; moisture drying, polar solvent extraction, polar
solvent evaporation, and polar solvent desolventizing. IPA is shown
as the polar solvent, which is reused in this process.
[0032] FIG. 4 (FIG. 4) is a block flow diagram showing another
embodiment of the present disclosure. Herein, FIG. 4 depicts a
block diagram of a production cycle for making partially refined
waste glycerol, including salt-containing fermentation grade
glycerol, wherein the steps encompass deoiling, dewatering and
desalting glycerol. The process is a hybrid process that includes
hydrophobic solvent liquid-liquid extraction through the use of
triacylglycerides (TAG), moisture drying, optional glycerol
evaporation, polar solvent extraction, polar solvent evaporation,
and polar solvent desolventizing. Here, glycerol is optionally
evaporated to reduce processing volume in the polar solvent
extraction step before the polar solvent is added. IPA is shown as
the polar solvent, which is reused in this process.
[0033] FIG. 5 (FIG. 5) is a block flow diagram showing another
embodiment of the present disclosure. Herein, FIG. 5 depicts a
block diagram of a production cycle for making partially refined
waste glycerol, including salt-containing fermentation grade
glycerol, wherein the steps encompass deoiling, dewatering and
desalting glycerol. The process is a hybrid process that includes
hydrophobic solvent liquid-liquid extraction through the use of
alkanes, alkenes, or acetate (hexane is shown here), wherein the
hydrophobic solvent is evaporated (e.g., through flash evaporation)
and re-used; moisture drying, optional glycerol evaporation, polar
solvent extraction, polar solvent evaporation, and polar solvent
desolventizing. Here, glycerol is optionally evaporated before the
polar solvent is added. IPA is shown as the polar solvent, which is
reused in this process.
[0034] FIG. 6 (FIG. 6) is a graph showing another embodiment of the
present disclosure. Herein, FIG. 6 depicts a graph that shows an
IPA to glycerol ratio per weight (IPA:glycerol) vs. the salt
concentration of NaCl that remains in the resulting DOWS
glycerol.
DETAILED DESCRIPTION
Brief Overview
[0035] The disclosure provides an efficient and cost-effective
process to produce partially refined waste glycerol, including
salt-containing fermentation grade glycerol. In an industrial
setting, glycerol is a by-product of biodiesel production and other
fat-splitting processes that include methods for making bio-fuels
and bio-hydrocarbons. Crude glycerol derived from biodiesel and
fat-splitting processes has organic impurities (i.e., oil-soluble
and water-soluble impurities) as well as inorganic impurities such
as salts including sodium chloride (NaCl), potassium chloride
(KCl), sodium sulfate (Na.sub.2SO.sub.4), potassium sulfate
(K.sub.2SO.sub.4) and others; heavy metals; and inorganic boiler
chemicals depending on the source of the glycerol and the process
employed. The impurities in crude glycerol as a source material or
feedstock can affect performance of any particular end product in
industrial applications. For fermentation applications, the
performance includes yield, productivity and titer. Thus, the
present disclosure provides a process of purifying crude glycerol
where organic and inorganic impurities in glycerol are
substantially reduced without yet meeting the purity standard of
USP glycerol, resulting in partially refined waste glycerol,
including salt-containing fermentation grade glycerol, which can be
used in many industrial applications.
DEFINITIONS
[0036] The terms "glycerol" and "glycerin" and "glycerine" are used
interchangeably herein and refer to a molecule that is covered by
the chemical formula CH.sub.2(OH)CH(OH)CH.sub.2OH. Glycerol is also
referred to as a trihydric alcohol; propane-1,2,3-triol;
1,2,3-propanetriol; 1,2,3-trihydroxypropane; glyceritol; glycerine;
and/or glycyl alcohol, all of which are encompassed herein.
[0037] The term "crude glycerol" refers to a substance that is
composed of mostly glycerol and impurities, including but not
limited to, methanol, water, both polar and non-polar organics
and/or salts. In one embodiment, crude glycerol contains methanol,
water, soaps, and salts and has a glycerol content of about 40 to
about 89 percent. In another embodiment, crude glycerol as starting
material contains about 0 to about 90% water, salts and/or organic
materials. In another embodiment, crude glycerol is a by-product of
a transesterification process. In still another embodiment, crude
glycerol is a by-product from the manufacture of biodiesel. Crude
glycerol derived from the manufacture of biodiesel contains between
about 70% to about 80% triglycerides and between about 20% to about
30% total impurities including organic and inorganic impurities
(see, e.g., Table 1A). In another embodiment, crude glycerol is a
by-product of a fat-splitting process. In another embodiment, crude
glycerol is a by-product of a soup making process.
[0038] A "partially refined waste glycerol" refers to a glycerol
that is produced by the purification process described herein. In
some embodiments, it is derived from the processing of natural fats
and oils. In other embodiments, it encompasses reduced salt and
reduced organic impurities as compared to crude glycerol. As such,
it may typically contain trace levels of oil-soluble organic
impurities and salts (e.g., NaCl, KCl, Na.sub.2SO.sub.4,
K.sub.2SO.sub.4, etc.) and may have a purity standard that ranges
from about 90 percent to about 99 percent, more commonly from about
95 percent to about 99 percent, and most commonly from about 97
percent to about 99 percent, depending on salt concentration. The
salt concentration in partially refined waste glycerol may range
from 0 percent to about 8.2 percent. In one embodiment,
salt-containing partially refined waste glycerol contains NaCl or
KCl or Na.sub.2SO.sub.4 or K.sub.2SO.sub.4 or a combination
thereof. In another embodiment, salt-containing partially refined
waste glycerol contains NaCl or KCl or Na.sub.2SO.sub.4 or
K.sub.2SO.sub.4 or sometimes more than one of these salts or any
other salt(s) that result from neutralizing of a homogeneous base
catalyst used in a biodiesel reaction with acid(s). The base
catalysts may be monovalent cationic oxides (e.g., Na.sub.2O,
K.sub.2O), cationic hydroxides (e.g., NaOH, KOH), and/or cationic
methylates and ethylates (e.g., NaOCH.sub.3, NaOC.sub.2H.sub.5,
KOCH.sub.3, KOC.sub.2H.sub.5) that are soluble in a biodiesel
reaction mixture. The acid(s) may be either inorganic or organic
acid(s). Examples of inorganic acid(s) are HCl, SO.sub.3,
H.sub.2SO.sub.4, H.sub.3PO.sub.4, HNO.sub.3, and others. Examples
of organic acids are H.sub.2CO.sub.3, acetic acid, formic acid,
lactic acid, gluconic acid, citric acid, succinic acid, and others.
Examples of the resulting salts are listed in Table 1B (infra).
Partially refined waste glycerol is suitable as an aid or component
in many industrial and/or commercial applications including, but
not limited to, paints, coats, adhesives, textiles, woods, metals,
detergents, soaps, coolants, cleaners, paper, and others.
[0039] A "fermentation grade glycerol" is an example of a
salt-containing partially refined waste glycerol that has a
specific salt content that ranges from about 0.05 percent salt to
less than about 8.2 percent salt (e.g., NaCl, KCl,
Na.sub.2SO.sub.4, K.sub.2SO.sub.4) and more particularly, from
about 0.05 percent salt to about 2.0 percent salt. Typically,
fermentation grade glycerol contains mostly NaCl or KCl or
Na.sub.2SO.sub.4 or K.sub.2SO.sub.4 or sometimes more than one of
these salts or other salts (see Table 1B, infra) or combinations of
other salts (see Table 1B, infra). Fermentation grade glycerol is
particularly suitable as a feedstock for fermentation procedures.
Herein, fermentation grade glycerol is suitable for a wide variety
of microbes that are employed in fermentation cultures as
production hosts. Examples of such microbial hosts, include, but
are not limited to organisms from the genus Escherichia, Bacillus,
Lactobacillus, Rhodococcus, Synechococcus, Synechoystis,
Pseudomonas, Aspergillus, Trichoderma, Neurospora, Fusarium,
Humicola, Rhizomucor, Kluyveromyces, Pichia, Mucor, Myceliophtora,
Penicillium, Phanerochaete, Pleurotus, Trametes, Chrysosporium,
Saccharomyces, Stenotrophamonas, Schizosaccharomyces, Yarrowia, or
Streptomyces. In one embodiment, the microbial host is Escherichia
coli. In other embodiments, the microbial host is Bacillus lentus,
Bacillus brevis, Bacillus stearothermophilus, Bacillus
licheniformis, Bacillus alkalophilus, Bacillus coagulans, Bacillus
circulans, Bacillus pumilis, Bacillus thuringiensis, Bacillus
clausii, Bacillus megaterium, Bacillus subtilis, and/or Bacillus
amyloliquefaciens. In other embodiments, the microbial host is
Synechococcus sp. PCC7002, Synechococcus elongatus PCC 7942,
Synechoystis sp. PCC 6803, Synechococcus elongatus PCC6301,
Prochlorococcus marinus CCMP1986 (MED4), Anabaena variabilis
ATCC29413, Nostoc punctiforme ATCC29133 (PCC73102), Gloeobacter
violaceus ATCC29082 (PCC7421), Nostoc sp. ATCC27893 (PCC7120),
Cyanothece sp. PCC7425 (29141), Cyanothece sp. ATCC51442, and/or
Synechococcus sp. ATCC27264 (PCC7002). In other embodiments, the
microbial host is Trichoderma koningii, Trichoderma viride,
Trichoderma reesei, Trichoderma longibrachiatum, Aspergillus
awamori, Aspergillus fumigates, Aspergillus foetidus, Aspergillus
nidulans, Aspergillus niger, Aspergillus oryzae, Humicola insolens,
Humicola lanuginose, Rhodococcus opacus, Rhizomucor miehei, and/or
Mucor michei. In other embodiments, the microbial host is
Actinomycetes. In yet other embodiments, the microbial host is
Streptomyces lividans and/or Streptomyces murinus. In other
embodiments, the microbial host is Saccharomyces cerevisiae.
[0040] The term "hydrophobic solvent" refers to a compound that
does not mix with water and readily partitions and/or is miscible
with a substance having hydrophobic characteristics. Examples of a
hydrophobic solvent include, but are not limited to, acetates
(e.g., butyl acetate, ethyl acetate), fatty acid alcohol esters
(e.g., fatty acid methyl ester (FAME), fatty acid ethyl ester
(FAEE), and fatty acid isopropyl ester), triacylglycerides (e.g.,
vegetable oil), alkanes (e.g., hexane, isohexane, and octane), and
alkenes (e.g., hexene, and octene).
[0041] The term "polar solvent" means, for the purpose of the
specification and claims, a compound that is readily miscible with
glycerol, can solubilize salt to only low levels if at all, and has
a lower boiling point than glycerol. Examples of such polar
solvents are alcohols, including but not limited to, isopropanol or
isopropyl alcohol (IPA), 1-propanol, 1-butanol, 2-butanol,
tert-butanol, ethanol, and methanol. Another example of a polar
solvent is phenol.
[0042] The term "DO glycerol" means, for the purpose of the
specification and claims, a form of glycerol that has been
partially refined by virtue of deoiling it. In one embodiment, DO
glycerol contains fewer oil-soluble organic impurities than crude
glycerol, i.e., oil-soluble organic impurities have been mostly
removed and are present below than about 195 ppm.
[0043] The term "DOW glycerol" means, for the purpose of the
specification and claims, a form of glycerol that has been deoiled
and dewatered in any order. DOW glycerol is the result of drying DO
glycerol such that most of the water has been removed. In one
embodiment, DOW glycerol contains less than about 0.5 percent
water.
[0044] The term "DOWS glycerol" means, for the purpose of the
specification and claims, a form of glycerol that has been deoiled,
dewatered, and desalted in any order. DOWS glycerol is the result
of desalting DOW glycerol such that most of the salt has been
removed. In one embodiment, DOWS glycerol for fermentation
application contains about 0.05 percent to about 2.0 percent
salt.
[0045] Glycerol
[0046] Glycerol is a trihydric alcohol, i.e., it is made up of
three alcohol groups. The chemical structure of glycerol is
CH.sub.2(OH)CH(OH)CH.sub.2OH. It is a clear, odorless, viscous
liquid with a naturally sweet taste. The terms glycerol and
glycerin are often used interchangeable, although glycerol is the
principle component of glycerin, e.g., about 96 percent glycerol
may be glycerin. Glycerol has a high boiling point and can be
dissolved by water and alcohol but not usually by oils. Crude
glycerol is a natural by-product from the processing of fats and
oils. For example, it is produced during transesterification of
biodiesel production processes (supra). In comparison, USP Grade
Glycerol (USP glycerol) is considered a pharmaceutical grade
glycerol that is highly pure. The abbreviation USP stands for
United States Pharmacopeia (i.e., a document that was first
published in 1820 and used as a standard reference by physicians).
Today, the USP includes chemical descriptions, identifying tests,
and purity tests for mostly active ingredients. All materials
listed in the USP are considered subject to the U.S. Food and Drug
Administration (FDA) requirements. Thus, labeling a product or a
substance as USP, as in USP glycerol, implies that it conforms to
the requirements of the FDA. USP glycerol has to meet specific
purity guidelines because it is used for pharmaceuticals, foods,
personal care, cosmetics, fragrances and other specialty
applications. The composition for USP glycerol on a dry basis must
meet a 99.7 to 100 percent purity standard and any trace amounts of
impurities must meet the USP specifications. This is a high
standard for a product and reflected in the cost of production. USP
grade glycerol is primarily produced by fractional distillation
(supra). Another category of glycerol is technical grade glycerol,
which must not meet the same purity standards as USP grade glycerol
but it must be cleaner than crude glycerol in order for it to be
suitable for use in industrial products (e.g., paints, coats, gels,
adhesives, etc.). Technical grade glycerol is typically purified
(e.g., about 80 to about 97 percent pure) with most of its
contaminants removed (i.e., no methanol, no soaps, no salts, etc.).
As a result, technical grade glycerol is expensive to make because
similar to USP grade glycerol, it is primarily produced by
fractional distillation (supra).
[0047] Partially Refined Waste Glycerol
[0048] The present disclosure provides a new form of glycerol, such
as a partially refined waste glycerol. Partially refined waste
glycerol has a novel composition that is cleaner than crude
glycerol but is not as highly purified as USP glycerol or technical
grade glycerol, in particular, it can contain trace levels of
oil-soluble organic impurities and/or salt. In one embodiment, a
partially refined waste glycerol contains some salt. In another
embodiment, a partially refined waste glycerol is salt free. In
another embodiment, partially refined waste glycerol can encompass
a tailored salt concentration that is adjusted to the use of the
glycerol product. In one embodiment, partially refined waste
glycerol is cleaner than crude glycerol but contains trace levels
of oil-soluble organic impurities. In another embodiment, partially
refined waste glycerol is cleaner than crude glycerol but contains
trace levels of oil-soluble organic impurities and salt. In yet
another embodiment, partially refined waste glycerol is cleaner
than crude glycerol but contains salt. In one embodiment, partially
refined waste glycerol has a salt concentration of 0 percent to
about 8.2 percent. Fermentation grade glycerol is an example of
partially refined waste glycerol. In one embodiment, fermentation
glycerol has a salt concentration of about 0.05 percent to less
than about 8.2 percent, including from about 0.05 percent to about
2.0 percent. In another embodiment, fermentation grade glycerol
that is particularly suitable for the use in fermentation cultures
where living organisms are used as production hosts (see, e.g.,
U.S. Pat. Nos. 8,372,610; 8,323,924; 8,313,934; 8,283,143;
8,268,599; 8,183,028; 8,110,670; 8,110,093; and 8,097,439, all of
which are incorporated herein by reference).
[0049] Fermentation Grade Glycerol
[0050] Fermentation grade glycerol is an example of partially
refined waste glycerol, where the salt content of the glycerol
composition can be tailored to the need of the organism that is
used in a fermentation method. Microorganisms can be used as
production hosts in fermentation cultures in order to produce
desired chemicals (e.g., fatty acids, fatty alcohols, fatty esters,
fatty alkanes, fatty alkenes, organic acids, diacids, terpenoids,
monomers, polymers, and others). These microorganisms or host cells
use a carbon source or feedstock as a form of food and energy
(e.g., host cells that produce fatty acid derivatives during a
fermentation process when a carbon source including glycerol is
used as a feedstock, see, e.g., U.S. Pat. Nos. 8,372,610;
8,323,924; 8,313,934; 8,283,143; 8,268,599; 8,183,028; 8,110,670;
8,110,093; and 8,097,439, all of which are incorporated herein by
reference).
[0051] In a natural environment, each microorganism has a certain
set tolerance for salt, i.e., each microorganism requires a
particular level of salt in order to satisfy its mineral nutrient
requirements (e.g., sodium chloride, phosphates, etc.). Nature
generally supplies enough salt to microbes. Conversely, if salt
levels are too high they become toxic and the microorganism
eventually turns inactive or dies. Biodiesel crude glycerol has a
salt content of about 6 to 8 percent, which exceeds the tolerance
level of many microorganisms. Thus, when the salt content of
glycerol as a feedstock in a fermentation broth is too high the
microbes become inactive. This explains why microbes that are used
in fermentations are generally fed with feedstock that meets a
higher purity standard or does not normally contain high salt or
other impurities (e.g., corn syrup, cane juice, USP glycerol, etc).
Conversely, when the salt content of glycerol as a feedstock in a
fermentation broth is too low (i.e., it falls below a certain
level) the microbes can no longer function as efficiently. For
example, marine organisms grow well at about 3.5 percent salt in a
fermentation broth while E. coli prefer about 0.5 to about 1.0
percent and generally tolerate no more than about 2 percent in a
fermentation broth. Raising the salt concentration of a
fermentation broth can increase the productivity of the microbes to
levels that are expected. This is typically accomplished by adding
extra salt during the fermentation run as needed, because when
glycerol is used as a feedstock it is usually a high purity
glycerol that cannot itself contribute to the salt content.
However, when fermentation glycerol was used it was unnecessary to
add additional salt to the fermentation broth (see Examples, Tables
3 and 4 (infra) and FIG. 6). Without wanting to the bound by
theory, it is suggested that fermentation grade glycerol may be
well tolerated because it supplies the microorganisms with just the
right amount of salt they need in order to function optimally. It
is well known that microorganisms can grow in a broad range of salt
concentrations, but the majority of microorganisms that have
industrial significance require a certain osmolarity in the growth
media, which is mostly provided by the addition of salts. The
beneficial osmolarity range is in general between about 25 to about
500 mOsmol per liter (mOsmol/L). Any fermentation that uses
microorganisms that require salt for optimal performance would
benefit from fermentation grade glycerol because it is neither too
toxic nor completely devoid of salt. Thus, a fermentation grade
glycerol is desirable, particularly a composition where the salt
content can be tailored to the need of the specific microorganism
in culture.
[0052] In one embodiment, the present disclosure provides a
glycerol composition that is a fermentation grade glycerol
composition with a tailored salt content. In another embodiment,
the present disclosure provides a fermentation grade glycerol
composition that includes a tailored salt content that ranges from
about 0.05 percent to about 2 percent salt content. In another
embodiment, the present disclosure provides a fermentation grade
glycerol composition that includes a tailored salt content that
ranges from about 0.06 percent to about 2 percent salt content. In
another embodiment, the present disclosure provides a fermentation
grade glycerol composition that includes a tailored salt content
that ranges from about 0.07 percent to about 2 percent salt
content. In yet another embodiment, the present disclosure provides
a fermentation grade glycerol composition that includes a tailored
salt content that ranges from about 0.08 percent to about 2 percent
salt content. In still another embodiment, the present disclosure
provides a fermentation grade glycerol composition that includes a
tailored salt content that ranges from about 0.09 percent to about
2 percent salt content. In another embodiment, the present
disclosure provides a fermentation grade glycerol composition that
includes a tailored salt content that ranges from about 0.1 percent
to about 2 percent salt content. In further embodiments, the
present disclosure provides a fermentation grade glycerol
composition that includes, but is not limited to, a tailored salt
content that ranges from about 0.2 percent to about 2 percent salt
content; from about 0.3 percent to about 2 percent salt content;
from about 0.4 percent to about 2 percent salt content; from about
0.5 percent to about 2 percent salt content; from about 0.6 percent
to about 2 percent salt content; from about 0.7 percent to about 2
percent salt content; from about 0.8 percent to about 2 percent
salt content; from about 0.9 percent to about 2 percent salt
content; from about 1 percent to about 2 percent salt content; and
from about 1.1 percent to about 2 percent salt content. In further
embodiments, the present disclosure provides a fermentation grade
glycerol composition that includes, but is not limited to, a
tailored salt content that ranges from about 1.2 percent to about 2
percent salt content; from about 1.3 percent to about 2 percent
salt content; from about 1.4 percent to about 2 percent salt
content; from about 1.5 percent to about 2 percent salt content;
from about 1.6 percent to about 2 percent salt content; from about
1.7 percent to about 2 percent salt content; from about 1.8 percent
to about 2 percent salt content; and from about 1.9 percent to
about 2 percent salt content. In a separate embodiment, the present
disclosure provides a fermentation grade glycerol composition that
includes a tailored salt content that ranges from about 0.05
percent to less than about 8.2 percent salt content. In another
embodiment, the present disclosure provides a fermentation grade
glycerol composition that includes, but is not limited to, a
tailored salt content that ranges from about 0.05 percent to about
3.5 percent salt content; from about 0.05 to about 3 percent salt
content; from about 0.05 to about 2.8 percent salt content; and
from about 0.05 to about 2.5 percent salt content.
[0053] In many industrial applications (i.e., where USP glycerol is
currently used because crude glycerol is not clean enough), an
alternative version of a cleaner glycerol would be desirable
because the purity standard does not necessarily have to be close
to 99 percent. Partially refined waste glycerol, including
fermentation grade glycerol can meet the 90 to 99 percent purity
standard that is desirable for many industrial applications while
being produced at a much lower cost. Typically, partially refined
waste glycerol has a purity of about 90 percent to about 99 percent
(e.g., about 91 percent to about 99 percent, about 92 percent to
about 99 percent, about 93 percent to about 99 percent, about 94
percent to about 99 percent, about 95 percent to about 99 percent,
about 96 percent to about 99 percent, or about 97 percent to about
99 percent, or about 98 percent to about 99 percent), depending on
salt concentration and water content. Allowing higher amounts of
crude glycerol to be converted to partially refined waste glycerol
including fermentation grade glycerol may prevent a surplus of
crude glycerol on the world market since higher amounts of crude
glycerol are expected to be produced with the rise of biodiesel
products. It may further eliminate the high cost of toxic waste
disposal for crude glycerol and may create a new profit margin for
biodiesel plant owners.
[0054] Glycerol in Fermentation
[0055] Fermentation procedures employ living organisms that cannot
survive under toxic conditions. The fermentation environment has to
be adjusted to support the growth of the microbes in culture. Since
glycerol is used as a feedstock in fermentation procedures it must
be suitable for microbial consumption and should be mostly free of
toxic by-products. The present disclosure provides a process for
glycerol purification or refinement that includes organic
extraction and salt precipitation, where toxic impurities in
glycerol are reduced to support microbial growth while still
leaving enough salt for the microbes to thrive. In one embodiment,
the process allows for removal of oil-soluble organic impurities
from glycerol. In another embodiment, the process allows for
removal of some inorganic impurities from glycerol. In one
embodiment, impurities are removed through an extraction or
deoiling technique by using a hydrophobic solvent such as, for
example, an acetate (e.g., butyl acetate, ethyl acetate), a fatty
acid alcohol ester (e.g., fatty acid methyl ester (FAME), fatty
acid ethyl ester (FAEE), and fatty acid isopropyl ester), a
triacylglyceride (TAG) (e.g., vegetable oil), an alkane (e.g.,
hexane, isohexane, and octane), an alkene (e.g., hexene, and
octene) or the like. As a result, the toxicity of glycerol is
substantially reduced and any potential contamination during
fermentation is minimized. The extraction of impurities as
described herein may be a high-throughput process that functions in
a low cost operating environment.
[0056] In another embodiment, the process allows for fine-tuning
the salt content in glycerol in order to produce partially refined
waste glycerol, including fermentation grade glycerol. As such, the
process allows for tailoring the final salt content in the glycerol
composition as an end product. The ability to tailor the salt
content of partially refined waste glycerol is desirable because
each microorganism in a fermentation broth has a certain set
tolerance for salt, i.e., if the salt concentration in the broth
becomes too high the microorganism may eventually become inactive
and die (supra). Conversely, each microorganism may require a
certain level of salt in order to satisfy its mineral nutrient
requirements and grow optimally in a fermentation broth. Thus, if
the salt content in glycerol as a feedstock is too high or too low
then the microorganism can no longer function properly (e.g.,
microbial hosts that produce fatty acid derivatives during a
fermentation process when glycerol is used as a feedstock, see,
e.g., U.S. Pat. Nos. 8,372,610; 8,323,924; 8,313,934; 8,283,143;
8,268,599; 8,183,028; 8,110,670; 8,110,093; and 8,097,439, all of
which are incorporated herein by reference). In one embodiment, the
salt content in fermentation grade glycerol is adjusted to be
between about 0.05 and less than about 8.2 percent in a
fermentation broth, which may benefit microbial organisms that are
used as hosts in fermentation cultures. In one embodiment, the salt
content in fermentation grade glycerol is adjusted to be between
about 0.05 and about 2.0 percent in a fermentation broth, which may
benefit microbial organisms that are used as hosts for production
in fermentation cultures. In another embodiment, the salt content
in fermentation grade glycerol is adjusted to be between about 0.05
and about 1.0 percent in a fermentation broth, which may benefit
microbial organisms that are used as hosts for production in
fermentation cultures. In yet another embodiment, the salt content
in fermentation glycerol is adjusted to be between about 0.05 and
about 3.5 percent in a fermentation broth.
[0057] In one embodiment, the present method can reduce the salt
level (e.g., NaCl, KCl, Na.sub.2SO.sub.4, K.sub.2SO.sub.4) in crude
glycerol by precipitating the existing salt using an alcohol (e.g.,
isopropyl alcohol (IPA), 1-pantanol, 1-butanol, etc.), followed by
evaporation of alcohol; and then fine-tune the salt level in
fermentation grade glycerol by further extraction and evaporation.
Herein the salt removal can be controlled and specifically tailored
to the specific microorganism and based on the desired end product
(i.e., various fermentation grade glycerol compositions having a
certain salt content). The desalting and evaporation steps may be
part of the high throughput processing, adding to the overall low
operating cost of this method. Hence, fermentation grade glycerol
with its tailored salt content and reduced oil-soluble organic
impurities can be made from crude glycerol following the specific
processing steps (i.e., deoiling, dewatering and desalting steps)
as discussed herein (infra).
[0058] In another embodiment, crude glycerol contains about 0.1
percent to about 3 percent of organic impurities overall; about 7
percent to about 9 percent of salt (e.g., on a dry basis, from a
biodiesel process) or about 3 percent of salt (e.g., on a dry
basis, from a fat-splitting process); and trace levels of heavy
metals. Table 1A below shows an example of a crude glycerol
composition (as a by-product of a biodiesel production) with its
organic and inorganic contaminants and impurities. Most of the
impurities listed in Table 1A have a higher boiling point than
glycerol. Some of them, such as 3-monochloropropane-1,2-diol
(3-MPCD), which is an organic boiler chemical, have a boiling point
similar to glycerol. Organic and inorganic acids as well as
methanol and low molecular weight diacetyl ketone (DAK) have lower
boiling points than glycerol and water.
TABLE-US-00001 TABLE 1A Example of a Crude Glycerol Composition
Potential Contaminants and Impurities in Type Crude Glycerol
derived from Biodiesel Organics Methanol Monoacylglycerides (MAG),
Diacylglycerides (DAG), Triacylglycerides (TAG) and Free Fatty
Acids (FFA) Fatty Acid Methyl Esters (FAME) Poly-Aromatic
Hydrocarbons (PAH) Dioxins And Dioxin Like Poly-Chlorinated
Biphenyl (PCBS) Mycotoxins, Diacetyl Ketone (DAK) Pesticides
3-Monochloropropane-1,2-Diol (3-MPCD) Mineral Oils Organic Boiler
Chemicals Inorganics Salt (e.g., NaCl, Na.sub.2SO.sub.4, KCl,
K.sub.2SO.sub.4, sodium acetate, potassium acetate, etc.) Heavy
Metals Inorganic Boiler Chemicals
[0059] The salt content in crude glycerol (e.g., about 3 to about 9
percent) exceeds the salt tolerance of many living microorganisms.
In addition, crude glycerol contains contaminants and impurities,
including heavy metals (see Table 1A, supra). Hence, crude glycerol
is not suitable as feedstock for most industrial microbial hosts.
For example, if crude glycerol is fed to E. coli in a fermentation
broth that produces fatty acid methyl esters (FAME) E. coli
activity ceases within 48 hours (see Table 4, infra). Conversely,
when oil soluble organic impurities and salts are reduced and the
cleaner fermentation grade glycerol is used as feedstock, the
performance of fermentation improved (see Table 4, infra). This
shows that the levels of oil-soluble organic impurities and salt in
glycerol can affect fermentation performance of living organisms
when glycerol is used as feedstock. In one embodiment, glycerol
contains about 1 to about 2 percent of salt so that good recovery
of product can be achieved via a fermentation culture. For example,
when glycerol contained about 1 percent of salt, ester production
via E. coli in culture was noticeably improved (see Table 3 and
Example 10, infra).
[0060] In many microbial organisms, growth starts to be inhibited
at salt concentrations above 2 percent, and growth inhibition is
more or less affected depending on the microbe, the additional
media components and the environmental conditions. Marine organisms
(halophiles) are exceptions and are able to grow in salt
concentrations above that of sea water (about 3.5 percent). In one
embodiment, when glycerol contains about 2 to 3 percent of salt,
fatty acid derivative production via halophiles in culture would be
improved. Some microbes can grow at salt concentrations up to 20 to
25 percent, although such a high salt content would not be suitable
for most industrial applications and/or fermentation cultures.
[0061] Process of Producing Partially Refined Waste Glycerol
[0062] The disclosure provides a new and clean process for
producing high yields of partially refined waste glycerol at a
minimum cost to the environment. The process entails organic
extraction and salt precipitation. The aim of this new process is
to produce partially refined waste glycerol that can be used in
various industrial applications including, for example, chemical
production via fermentation, animal feeds, green automobile
coolants, and the like. One advantage of this process is that
partially refined waste glycerol is produced in a high-throughput
capacity, which is less expensive than conventional fractional
distillation methods (supra). Another advantage of this process is
that it creates fewer waste products because it proceeds with a
relatively minor loss of glycerol and reuses hydrophobic and polar
solvents, thereby reducing the impact on the environment. FIGS. 1
through 5 depict flow diagrams of the process of producing
partially refined waste glycerol. In one embodiment, the process
may be carried out via mixing tanks, liquid-liquid separators, and
desolventizers as known in the art. In another embodiment, the
process includes hydrophobic solvent liquid-liquid extraction
through the use of a hydrophobic solvent such as, for example,
triacylglycerides (TAG), moisture drying, polar solvent extraction,
polar solvent evaporation, and polar solvent desolventizing (see
FIG. 2). In another embodiment, the process includes hydrophobic
solvent liquid-liquid extraction through the use of a hydrophobic
solvent such as, for example, butyl acetate, moisture drying, polar
solvent extraction, polar solvent evaporation, and polar solvent
desolventizing. In another embodiment, the process includes
hydrophobic solvent liquid-liquid extraction through the use of a
hydrophobic solvent such as, for example, FAME, moisture drying,
polar solvent extraction, polar solvent evaporation, and polar
solvent desolventizing. In another embodiment, the process includes
hydrophobic solvent liquid-liquid extraction through the use of
alkanes (e.g., hexane) or alkenes (e.g., hexene) or acetates (e.g.,
butyl acetate, ethyl acetate), wherein the hydrophobic solvent is
evaporated (e.g., through flash evaporation) and re-used; moisture
drying, polar solvent extraction, polar solvent evaporation, and
polar solvent desolventizing (see FIG. 3). In another embodiment,
the process includes hydrophobic solvent liquid-liquid extraction
through the use of a hydrophobic solvent (e.g., triacylglycerides
(TAG)), moisture drying, optional glycerol evaporation, polar
solvent extraction, polar solvent evaporation, and polar solvent
desolventizing (see FIG. 4). Herein, glycerol is optionally
evaporated before the polar solvent is added. In another
embodiment, the process includes hydrophobic solvent liquid-liquid
extraction through the use of alkanes (e.g., hexane) or alkenes
(e.g., hexene) or acetate (e.g., ethyl acetate) or fatty acid
alcohol esters (e.g. FAME, FAEE and fatty acid isoprophyl esters),
wherein the hydrophobic solvent is evaporated (e.g., through flash
evaporation) and re-used; moisture drying, optional glycerol
evaporation, polar solvent extraction, polar solvent evaporation,
and polar solvent desolventizing (see FIG. 5). Similarly, glycerol
is optionally evaporated before the polar solvent is added. As can
be seen in FIGS. 3 and 5, hydrophobic solvent evaporation allows
for the reuse of the solvent back into the system and further
separates out oil-soluble organic impurities. In one embodiment,
the hydrophobic solvent is TAG. In another embodiment the
hydrophobic solvent is hexane. In another embodiment, the polar
solvent is isopropanol (IPA), which can be reused in this
process.
[0063] In order to utilize crude glycerol (e.g., from biodiesel and
fat-splitting processes) and produce partially refined waste
glycerol, crude glycerol can be deoiled, dewatered and desalted in
any order. In the flow diagrams of FIGS. 2-5, deoiling glycerol
encompasses hydrophobic solvent liquid-liquid extraction;
dewatering glycerol encompasses moisture drying; and desalting
glycerol encompasses optional glycerol evaporation, polar solvent
extraction, polar solvent evaporation, and polar solvent
desolventizing. Since both hydrophobic and polar solvents can be
reused in this system not much waste product is generated. There is
minor loss of glycerol and the process can be carried out in a
biodiesel facility by using triacylglycerides (TAG), butyl acetate,
ethyl acetate, FAME, FAEE, fatty acid isopropyl ester, hexane, or
the like as a hydrophobic solvent. In addition, any oil-soluble or
organic impurities can be reused as boiler fuel. Hence, the process
is recyclable, cost effective, and green.
[0064] More specifically, two interchangeable process routes were
developed to treat crude glycerol in order to produce partially
refined waste glycerol, including salt-containing fermentation
grade glycerol. The first process route includes deoiling crude
glycerol through a hydrophobic solvent liquid-liquid extraction
step (e.g., via TAG, butyl acetate, ethyl acetate, FAME, FAEE,
fatty acid isopropyl ester or hexane) and dewatering the deoiled
glycerol through moisture drying. The deoiled and dewatered
glycerol undergoes desalting through a polar solvent-based salt
precipitation step (e.g., via IPA) (see FIGS. 2 and 4). The
ordering of the basic process steps of deoiling, dewatering, and
desalting is interchangeable (see FIGS. 1A and 1B). The second
process route includes deoiling crude glycerol through a
hydrophobic or hydrophobic solvent liquid-liquid extraction step
(e.g., via TAG, butyl acetate, ethyl acetate, FAME, FAEE, fatty
acid isopropyl ester or hexane), dewatering the deoiled glycerol
through moisture drying; and evaporating the deoiled and dewatered
glycerol, followed by a polar solvent-based salt precipitation step
(e.g., via IPA) of the evaporation bottom (see FIGS. 3 and 5).
Similarly, the ordering of the basic process steps of deoiling,
dewatering, and desalting is interchangeable (see FIGS. 1A and 1B).
Both process routes result in partially refined waste glycerol that
has fewer oil soluble organic impurities and a lower salt content
then crude glycerol. The salt concentration of the final glycerol
product can be tailored to produce a partially refined waste
glycerol that contains a desirable concentration of salt, making it
a suitable feedstock for many industrial applications including
fermentation. In addition, the salt content of partially refined
waste glycerol can be fine-tuned, resulting in a particularly
suitable feedstock for fermentation (i.e., fermentation grade
glycerol) that requires a specific salt-content due to its
production hosts. In one embodiment, salt reduction, salt tailoring
and/or salt fine-tuning can be achieved by employing both process
routes. Thus, both process routes can be employed
interchangeably.
[0065] For example, adding no polar solvent to glycerol would lead
to about 8.2 percent salt in the final glycerol product. On the
other hand, adding polar solvent to glycerol at a weight ratio of
about 2.1 would lead to about 2 percent salt in the final glycerol
product. Similarly, adding polar solvent to glycerol at a weight
ratio of about 3.3 would lead to about 1 percent salt in the final
glycerol product. Thus, the process can effectively tailor and
fine-tune the final salt concentration in the glycerol end product
(see Example 8, infra). The final yield of partially refined waste
glycerol produced by this process usually ranges from about 97
percent to about 99 percent, depending on salt concentration.
[0066] The present disclosure provides a process for glycerol
purification that further encompasses a hybrid process step for
desalting glycerol (see FIGS. 4 and 5). For example, it is shown in
FIGS. 4 and 5 that optional glycerol evaporation (i.e., partial
glycerol evaporation) can lead to treated glycerol recovery without
salt precipitation. This is accomplished by subjecting about 75
percent of glycerol (as a glycerol distillate) to partial
evaporation, and then recovering the remaining approximately 25
percent glycerol in the evaporation discharge bottom, which is then
further desalted by precipitating it via a polar solvent such as
IPA. Thus, the system allows for clean glycerol to be recovered
directly through partial evaporation leading to partially refined
waste glycerol that is salt-free and between about 97 percent and
about 99 percent pure. Herein, the partial glycerol evaporation
produces about 75 percent clean and salt-free glycerol, while the
rest of the remaining glycerol mixture is salt-saturated and
subject to polar solvent (e.g., IPA) extraction. The clean glycerol
derived from evaporation can be fed back into the system (or
optionally used as a final product). Salt-saturating glycerol
before IPA extraction allows the salt content of the final glycerol
composition to be tailored and fine-tuned.
[0067] I. Deoiling Crude Glycerol
[0068] In various embodiments of the disclosure as shown in FIGS. 1
through 5, the crude glycerol is first subjected to a deoiling step
for removal of the organic impurities. In other embodiments,
however, the deoiling step may be performed after the dewatering
step, or after the desalting step, or after the completion of the
dewatering and desalting step. Deoiling may occur as either the
first step, second step or final step in the process as shown in
FIGS. 1A and 1B.
[0069] Crude glycerol contains about 80 percent to about 88 percent
glycerol, about 6 percent to about 10 percent water, about 6
percent to about 8 percent salt (e.g., NaCl, KCl, Na.sub.2SO.sub.4,
K.sub.2SO.sub.4), about 0.1 percent to about 3 percent organics and
less than about 0.3 percent methanol. The organic oil-soluble
impurities and contaminants that are contained within crude
glycerol may include toxins that can inactive or pollute industrial
processes that employ glycerol. Most of these contaminants are
hydrophobic. The present method uses hydrophobic solvents such as,
for example, hexane, TAG, butyl acetate, ethyl acetate, FAME, FAEE,
fatty acid isopropyl ester, or the like to remove most of these
organic contaminants from crude glycerol via solvent extraction.
Some contaminants may have a more polar nature. For example,
oxidized color bodies have polar characteristics in that they are
not soluble in pure hexane but at least partially soluble in TAG,
FAME, FAEE and fatty acid isoprophyl esters, and are highly soluble
in butyl acetate and ethyl acetate. In one embodiment, a less
expensive hexane is a hydrophobic solvent for deoiling crude
glycerol containing medium to low levels of polar organic
impurities. In another embodiment, butyl acetate or ethyl acetate
is a hydrophobic solvent for deoiling crude glycerol containing
higher levels of polar organic impurities.
[0070] In one embodiment, the hydrophobic solvent is nonvolatile
and/or has a lower boiling point (bp) than oil-soluble organic
impurities, has a low heat of vaporization (.DELTA.Hv) and has a
low heat capacity (Cp). Examples of a hydrophobic solvent include,
but are not limited to, TAG which has nonvolatile characteristics
(see FIGS. 2 and 4); alkanes with C.sub.6 to C.sub.10 hydrocarbon
chain-length or mixtures thereof (e.g., hexane; see FIGS. 3 and 5);
alkenes with C.sub.6 to C.sub.10 hydrocarbon chain-length or
mixtures thereof (e.g., hexene); and acetates such as, for example,
ethyl acetate or butyl acetate, and fatty acid alcohol esters such
as, for example, FAME, FAEE or fatty acid isopropyl esters. In one
embodiment, the solvent is hydrophobic in nature. In another
embodiment, the solvent is non-polar or polar in nature and is not
miscible with water and glycerol. In another embodiment, the
solvent has a lower boiling point and a lower heat of vaporization
than water. In still another embodiment, the solvent has a higher
boiling point than the oily organic impurities found in crude
glycerol. In another embodiment, the solvent has a density that is
lower than glycerol. The extraction efficiency of any of the
hydrophobic solvents can be enhanced by the presence of about 6
percent to about 10 percent water in crude glycerol. Most
oil-soluble impurities and contaminants presented in the crude
glycerol are removed from the glycerol via solvent extraction
regardless of the boiling points of the various contaminants.
[0071] One embodiment of the present disclosure is shown in FIG. 2
which provides a process for purifying crude glycerol wherein
removal of oil-soluble impurities and contaminants is carried out
via a hydrophobic solvent liquid-liquid extraction in order to
produce deoiled (DO) glycerol. In one embodiment, partially refined
waste glycerol encompasses DO glycerol. The amount of solvent used
depends on the amount of oil-soluble impurities that are present in
the crude glycerol. If deoiling is carried out in a biodiesel
facility, TAG can be one of the solvents, because spent TAG can be
re-used as biodiesel feed after the deoiling extraction has been
completed (see FIGS. 2 and 4). The spent TAG contains TAG and
extracted TAG soluble organic impurities. This generates fewer
waste products during the glycerol purification process. In one
embodiment, about 5 percent to about 20 percent of TAG (e.g.,
refined vegetable oil such as corn oil) can be used to prepare DO
glycerol. In another embodiment, the solvent extraction can be
carried out at about 20 to 95.degree. C. In another embodiment, the
solvent extraction can be carried out at about 20 to 95.degree. C.
and more preferably at about 40 to 80.degree. C. from about 5
minutes to about 30 minutes under vigorous mixing. In another
embodiment, the solvent extraction can be carried out at about 55
to 65.degree. C. In another embodiment, the solvent extraction can
be carried out at about 55 to 65.degree. C. from about 5 minutes to
about 30 minutes under vigorous mixing. In another embodiment, the
solvent extraction can be carried out at about 60.degree. C. In
another embodiment, the solvent extraction can be carried out at
about 60.degree. C. from about 5 minutes to about 30 minutes under
vigorous mixing. In another embodiment, solvent extraction is
followed by gravity decantation, hydrocyclone separation, and/or
low speed liquid-liquid centrifugal separation.
[0072] If deoiling is carried out at a facility remote from or
unrelated to a biodiesel facility, or if the use of a differing
solvent is desired for the purposes of increasing the purity of
crude glycerol containing low levels of polar organic impurities,
another hydrophobic solvent available for use is alkane. In one
embodiment, the hydrophobic solvent is an acetate such as butyl
acetate. In another embodiment as shown on FIG. 3, a useful
hydrophobic solvent is hexane. Hexane has a boiling point of
69.degree. C., 145 btu/lb heat of vaporization (.DELTA.Hv), and
0.53 btu/lb .degree. C. heat capacity (Cp). In one embodiment,
about 5 percent to about 20 percent of hexane can be used to
prepare DO glycerol. The amount of hexane required for extraction
depends on the amount of oil-soluble impurities (e.g., polar and/or
non-polar oil-soluble impurities) that are present in crude
glycerol. Oil-soluble impurities that have been extracted can be
removed through flash evaporation of the hydrophobic solvent as an
evaporator bottom. For example, when about 5 percent hexane is used
for deoiling crude glycerol, then recovery of hexane through flash
evaporation requires about 22,000 btu/mt of crude glycerol. Along
those same lines, when about 10 percent hexane is used for deoiling
crude glycerol, then recovery of hexane through flash evaporation
requires about 44,000 btu/mt of crude glycerol.
[0073] The density of hexane, vegetable oil and glycerol are 0.659
g/ml, 0.88 g/ml and 1.26 g/ml, respectively. When the hydrophobic
solvent is combined with glycerol in order to remove the
oil-soluble impurities and contaminants, the resulting mixture is
separated into a DO glycerol phase and a hexane/contaminants phase
by low g-force gravity separation. The hexane solvent is then
recovered from a hexane/contaminant stream by flash evaporation. In
one embodiment, a low g-force gravity separation is used to
separate the hydrophobic solvent part containing oil-soluble
organic impurities and contaminants from the crude glycerol part.
Due to the larger density difference between the solvent part (that
contains the impurities and contaminants) and the glycerol part, a
low g-force is sufficient to effectively separate the two parts. In
one embodiment, the density separation is carried out at about 10
to about 1000 g-force. In another embodiment, the density
separation is carried out at about 25 g-force. In still another
embodiment, the density separation is carried out at about 20
g-force (e.g., via a hydrocyclone). In some embodiments, a gravity
decantation, a hydro-cyclone, and/or a low speed liquid-liquid
centrifugal separator (e.g., CINC L-L separator) can be used for
this type of separation. After the density separation, the
hydrophobic solvent is recovered through flash evaporation. The
recovered solvent is then recycled for reuse. The oil-soluble
organic impurities and contaminants can be used as a boiler fuel.
This step generates few to no waste products.
[0074] II. Dewatering Deoiled Glycerol
[0075] In various embodiments of the disclosure as shown in FIGS. 1
through 5, the dewatering step immediately follows the deoiling
step. In other embodiments, however, the dewatering step may be
performed as the initial step. Dewatering may occur as either the
first step, second step or final step in the process as shown in
FIGS. 1A and 1B.
[0076] The DO glycerol produced above (supra) may still contain
some water. In one embodiment, it contains about 6 percent to about
10 percent water. DO glycerol can be dewatered through moisture
drying (e.g., evaporation) in order to produce deoiled and
dewatered (DOW) glycerol. In one embodiment, partially refined
waste glycerol encompasses DOW glycerol. In another embodiment, DO
glycerol is dewatered at about 60 to about 130.degree. C. In
another embodiment, DO glycerol is dewatered at about 90.degree. C.
and about 20 to about 60 ton resulting in less than about 0.5
percent moisture content. In one embodiment, DO glycerol is
dewatered at about 90.degree. C. and about 60 ton resulting in less
than about 0.5 percent moisture content. In another embodiment, DO
glycerol is dewatered at about 110.degree. C. and about 60 torr
resulting in less than about 0.5 percent moisture content. In still
another embodiment, DO glycerol is dewatered at about 130.degree.
C. and about 60 ton resulting in less than about 0.5 percent
moisture content. During dewatering of DO glycerol, shown as the
moisture drying step in FIGS. 2 through 5, impurities that have a
low boiling point as well as trace levels of methanol are removed.
Any water evaporator can be used herein as equipment for moisture
drying, wherein optimal moisture drying conditions are determined
by following the manufacturer's suggestions (e.g., ASPEN modeling).
The evaporated water is cooled and captured as condensate water.
The condensate water contains methanol and small amount of
hydrophobic solvent. The hydrophobic solvent, which is not miscible
in water, is recovered by gravity decantation. The waste water
containing methanol in the bottom layer of the decanter is about 6%
to about 10% of crude glycerol.
[0077] III. Desalting Deoiled and Dewatered Glycerol
[0078] In various embodiments of the disclosure as shown in FIGS. 1
through 5, the desalting step is the final process operation
performed in the production of the products--the partially refined
waste glycerol or the fermentation grade glycerol. In other
embodiments, however, the dewatering step may be performed as the
initial step or following the initial step in the process.
Desalting may occur as either the first step, second step or final
step in the process as shown in FIGS. 1A and 1B.
[0079] The DOW glycerol produced above (supra) contains about 88
percent to about 91 percent glycerol, about 0.5 percent water, and
about 7 percent to about 9 percent salt (e.g., NaCl) and trace
amounts of organics. After deoiling and dewatering the crude
glycerol, desalting of DOW glycerol can be carried out in two
different ways that are interchangeable, including desalting of the
DOW glycerol via a polar solvent (e.g., via alcohols such as IPA or
butanol; or via phenols) (also shown in FIGS. 2 and 3); or optional
partial evaporation of the DOW glycerol followed by desalting of
the evaporation bottom via a polar solvent (e.g., via alcohols such
as IPA or butanol; or via phenols) in order to produce deoiled,
dewatered and desalted (DOWS) glycerol (shown in FIGS. 4 and 5).
Thus, the second way contemplates a hybrid process step for
desalting glycerol. In one embodiment, partially refined waste
glycerol encompasses DOWS glycerol.
[0080] More specifically, the first way of desalting includes (1)
polar solvent precipitation of salt from the DOW glycerol, (2)
density separation of salt at a low g-force and (3) flash
evaporation of the polar solvent from the polar solvent-glycerol
mixture and from the solvent salt mixture. The second way of
desalting includes (1) partial evaporation of the DOW glycerol, (2)
polar solvent precipitation of the evaporation bottom, (3) density
separation of salt at a low g-force and (4) flash evaporation of
the polar solvent from the polar solvent-glycerol mixture and from
the solvent salt mixture. The polar solvents that can be used are,
for example, alcohols such as IPA or butanol, and phenols. FIGS. 4
and 5 provide block flow diagrams that show differing embodiments
wherein the hybrid process step for desalting DOW glycerol is
utilized.
[0081] In the first method as shown in FIGS. 2 and 3, the DOW
glycerol is added to the polar solvent that acts as a solvent to
precipitate super-saturated salt from the resulting polar
solvent-glycerol mixture. This is carried out at a temperature that
ranges from about 20 to about 100.degree. C., and more particularly
at a temperature that ranges from about 40 to about 80.degree. C.
In another embodiment, the temperature ranges from about 50 to
about 70.degree. C. In one embodiment, the DOW glycerol is added to
the polar solvent that acts as a solvent to precipitate
super-saturated salt from the resulting polar solvent-glycerol
mixture at 60.degree. C. In one another, the polar solvent is IPA.
In another embodiment, the polar solvent is butanol. In yet another
embodiment, the polar solvent is a phenol. In one embodiment, the
density separation is carried out at about 10 to about 50 g-force.
In another embodiment, the density separation is carried out at
about 25 g-force. In still another embodiment, the density
separation is carried out at about 20 g-force. In some embodiments,
a gravity decantation, or a hydrocyclone can be used for this type
of separation, with the light phase containing the glycerol and the
heavy phase containing precipitated salt. In one embodiment, the
polar solvent-glycerol solution saturated with salt (the light
phase) is then flash evaporated at about 80.degree. C. and about 60
torr to recover the polar solvent. In another embodiment, the polar
solvent-glycerol solution saturated with salt is flash evaporated
at about 90 to about 100.degree. C. and at ambient pressure to
recover the polar solvent.
[0082] One embodiment involves the initial process steps of
deoiling followed by desalting. Another embodiment involves the
initial process steps of desalting and deoiling. In either of these
embodiments, it is unnecessary to perform a separate dewatering
step. This occurs as a result of the need to separate the polar
solvent such as IPA which operates to precipitate the salt from the
mixture. The process of separating the polar solvent from the
mixture after salt precipitation utilizes heat at or above the
boiling point of the polar solvent, for example 80.degree. C., and
altered pressure, for example, 60 ton, to effectively boil off the
solvent. In sum, the effective temperature may be altered by the
alteration of the pressure at which vaporization occurs. In those
embodiments as shown in FIG. 1B, where the dewatering step is not
performed prior to the desalting step, the process of solvent
removal by distillation wherein heat is applied to vaporize the
solvent which also operates to vaporize the water in the glycerol
thereby effectively removing the water from the product stream. In
order to reuse the solvent, however, an additional step is
necessary to separate the water from the solvent stream recovered
by condensing the mixture vaporized from the glycerol.
[0083] The resulting evaporator bottom phase is salt reduced DOW
glycerol. As noted above, the salt reduced glycerol that is also
deoiled and dewatered is referred to as DOWS glycerol (i.e.,
deoiled, dewatered/dried, and desalted glycerol). The salt content
in DOWS glycerol depends on the ratio of polar solvent to glycerol
(supra). Thus, the salt content of DOWS glycerol can be tailored
and fine-tuned as needed.
[0084] In the second method as shown in FIGS. 4 and 5, the DOWS
glycerol is produced by subjecting about 75 percent of the DOW
glycerol (as a glycerol distillate) to evaporation, and then
recovering the remaining approximately 25 percent glycerol in the
evaporation discharge bottom (which is then further desalted by
precipitating it via a polar solvent as shown in the first method,
supra). This is a hybrid process and the evaporated glycerol is
generally free of salt. The salt content in the
polar-solvent-desalted glycerol composition can then be tailored by
applying the appropriate ratio of glycerol to IPA in order to
produce a partially refined waste glycerol or fermentation grade
glycerol as an end product. The glycerol distillate is an
evaporated material containing mostly glycerol, about 0.5 percent
water, and some trace levels of organic materials.
[0085] The two interchangeable desalting steps (i.e., with or
without partial glycerol evaporation) provide the basis for the two
different processes. Both processes include (1) deoiling, (2)
dewatering and (3) desalting steps in any order. Since residual oil
soluble organic impurities end-up in the evaporation bottom after
deoiling, any oil-soluble organic impurities that remain at the end
of the two processes are the same. The loss of glycerol yield
employing any of the two interchangeable desalting steps is less
than 1%. The loss of yield is low because any residual glycerol
that is left with the polar solvent, which is contained in the salt
matrix after polar solvent precipitation, can be further recovered
by a polar solvent wash. Any residual polar solvent in the salt
phase can be recovered through de-solventization and reused. This
step generates few to no waste products.
[0086] The desalting step or salt removal can be used to collect
the removed salt as a useful by-product which is nearly free from
organic impurities and glycerol. The removed salt can be re-used in
other processes. For example, the salt can be collected for use in
industrial processes or for the use of industrial products. As
such, various salts are contemplated herein including NaCl, KCl,
Na.sub.2SO.sub.4, K.sub.2SO.sub.4, and others (see, e.g., Table 1B
below). In one embodiment, NaCl is collected for use in animal
nutrition, water softening, de-icing, and others. In another
embodiment, KCl or K.sub.2SO.sub.4 is collected for use as
agricultural fertilizer.
TABLE-US-00002 TABLE 1B Examples of Salt Produced as By-Product
after De-salting Homogeneous Base Catalyst Neutralizing Acids Salts
sodium oxide (Na.sub.2O), hydrochloric acid (HCl), Sodium chloride
(NaCl), sodium hydroxide (NaOH), sulfuric acid (H.sub.2SO.sub.4),
sodium sulfate (Na.sub.2SO.sub.4), sodium methoxide (NaOCH.sub.3),
phosphoric acid (H.sub.3PO.sub.4), sodium phosphate
(Na.sub.3PO.sub.4), sodium ethoxide (NaOC.sub.2CH.sub.5) nitric
acid (HNO.sub.3) sodium nitrate (NaNO.sub.3) acetic acid
(C.sub.2H.sub.4O.sub.2), sodium acetate (C.sub.2H.sub.3NaO.sub.2),
carbonic acid (H.sub.2CO.sub.3), sodium carbonate
(Na.sub.2CO.sub.3), formic acid (CH.sub.2O.sub.2), sodium formate
(HCOONa), lactic acid (C.sub.3H.sub.6O.sub.3), sodium lactate
(C.sub.3H.sub.5NaO.sub.3), gluconic acid (C.sub.6H.sub.12O.sub.7),
sodium gluconate (C.sub.6H.sub.11NaO.sub.7), citric acid
(C.sub.6H.sub.8O.sub.7), sodium citrate
(C.sub.6H.sub.5Na.sub.3O.sub.7), methanesulfonic acid sodium
methanesulfonate (CH.sub.4O.sub.3S) (CH.sub.3NaO.sub.3S) boric acid
(H.sub.3BO.sub.3) sodium borate (Na.sub.2B.sub.4O.sub.7) potassium
oxide (K.sub.2O), hydrochloric acid (HCl), potassium chloride
(KCl), potassium hydroxide (KOH), sulfuric acid (H.sub.2SO.sub.4),
potassium sulfate (K.sub.2SO.sub.4), potassium methoxide
(KOCH.sub.3), phosphoric acid (H.sub.3PO.sub.4), potassium
phosphate (K.sub.3PO.sub.4), potassium ethoxide (KOC.sub.2CH.sub.5)
nitric acid (HNO.sub.3) potassium nitrate (KNO.sub.3) acetic acid
(C.sub.2H.sub.4O.sub.2), potassium acetate (CH.sub.3CO.sub.2K),
carbonic acid (H.sub.2CO.sub.3), potassium carbonate
(K.sub.2CO.sub.3), formic acid (CH.sub.2O.sub.2), potassium formate
(CHKO.sub.2), lactic acid (C.sub.3H.sub.6O.sub.3), potassium
lactate (C.sub.3H.sub.5KO.sub.3), gluconic acid
(C.sub.6H.sub.12O.sub.7), potassium gluconate
(C.sub.6H.sub.11KO.sub.7), citric acid (C.sub.6H.sub.8O.sub.7),
potassium citrate (C.sub.6H.sub.5K.sub.3O.sub.7), methanesulfonic
acid potassium methanesulfonate (CH.sub.4O.sub.3S)
(CH.sub.3KO.sub.3S) boric acid (H.sub.3BO.sub.3) potassium borate
(K.sub.2B.sub.4O.sub.7) guanidine (CH.sub.5N.sub.3) hydrochloric
acid (HCl), guanidine hydrochloride (CH.sub.5N.sub.3.cndot.HCl),
sulfuric acid (H.sub.2SO.sub.4), guanidine sulfate
(2(CH.sub.5N.sub.3).cndot.H.sub.2SO.sub.4), phosphoric acid
(H.sub.3PO.sub.4), guanidine phosphate
(2(CH.sub.5N.sub.3).cndot.H.sub.3PO.sub.4), acetic acid
(C.sub.2H.sub.4O.sub.2), guanidine acetate
(CH.sub.5N.sub.3.cndot.C.sub.2H.sub.4O.sub.2), carbonic acid
(H.sub.2CO.sub.3), guanidine carbonate
(CH.sub.5N.sub.3.cndot.H.sub.2CO.sub.3), citric acid
(C.sub.6H.sub.8O.sub.7), guanidine citrate
(CH.sub.5N.sub.3.cndot.C.sub.6H.sub.8O.sub.7), methanesulfonic acid
guanidine methanesulfonate (CH.sub.4O.sub.3S)
(CH.sub.5N.sub.3.cndot.CH.sub.4O.sub.3S)
[0087] Uses of Partially Refined Waste Glycerol
[0088] The present disclosure provides partially refined waste
glycerol, including salt-containing partially refined waste
glycerol that can be employed in industrial applications. The salt
content of the partially refined waste glycerol can be tailored to
various uses. In one embodiment, a partially refined waste glycerol
with no salt content can be used in various industrial
applications. In another embodiment, a partially refined waste
glycerol with a specific salt content in the range from about 0.05
percent to about 8.2 percent can be used in various industrial
applications. In another embodiment, a partially refined waste
glycerol with a specific salt content in the range from about 0.05
percent to about 3.5 percent can be used as fermentation grade
glycerol in fermentations that employ microbial hosts with a higher
salt tolerance (e.g., marine organisms). In another embodiment, a
partially refined waste glycerol with a specific salt content in
the range from about 0.05 percent to about 2 percent can be used as
fermentation grade glycerol in fermentations that employ microbial
hosts with a lower salt tolerance (e.g., E. coli). In yet another
embodiment, a partially refined waste glycerol with a specific salt
content in the range from about 0.05 percent to less than about 8.2
percent can be used as fermentation grade glycerol in fermentations
that employ microbial hosts with a higher salt tolerance. In yet
another embodiment, a partially refined waste glycerol with a
specific salt content in the range from about 0.05 percent to less
than about 8.2 percent can be used as fermentation grade glycerol
in fermentations that employ microbial hosts (e.g., E. coli) that
have been altered such that they can tolerate a higher salt
concentration than their native counterparts.
[0089] In another embodiment, partially refined waste glycerol can
be used as a humectant, emulsifier and plasticizer and it is
compatible with a wide variety of materials and mixes. In another
embodiment, partially refined waste glycerol can be used as an
adhesive such as with plasticizing and penetrating properties. In
another embodiment, partially refined waste glycerol can be used
for agriculture such as for sprays, dips and washes. In another
embodiment, partially refined waste glycerol can be used as green
antifreeze or automobile coolant. In another embodiment, partially
refined waste glycerol can be used as a cleaner or polisher such as
in the home, office and automobile market. In another embodiment,
partially refined waste glycerol can be used to treat or alter
materials such as leather (e.g., tanning and finishing) and
textiles (e.g., facilitating printing and dying; lubricating and
snag-proofing; antistatic-, antishrink-, and anticrease treatments;
water-proofing; flame-proofing). In another embodiment, partially
refined waste glycerol is used to process metals such as pickling,
quenching, stripping, electroplating, galvanizing, and soldering.
In still another embodiment, partially refined waste glycerol can
be used to treat paper such as acting as a humectant, plasticizer,
softening agent, and barrier agent (e.g., against grease and
solvents). In another embodiment, partially refined waste glycerol
can be used in photography as wetting and plasticizing agent. In
another embodiment, partially refined waste glycerol can be used as
resin, including ester gums, polyurethanes, and epoxies. In yet
another embodiment, partially refined waste glycerol can be used in
detergents.
EXAMPLES
[0090] The following examples further illustrate the disclosure but
should not be construed in any way as limiting its scope.
[0091] In order to utilize crude glycerol that is derived from
biodiesel production and other fat-splitting processes, it must be
cost-effectively deoiled, dewatered and desalted in order to
produce partially refined waste glycerol that is suitable for many
industrial applications. The examples below describe the process
that was developed in order to produce partially refined waste
glycerol. The examples also show how salt-containing glycerol was
made.
Example 1: Process of Producing Deoiled (DO) Glycerol Using
Vegetable Oil as Hydrophobic Solvent
[0092] Crude glycerol (see Table 2, infra) was deoiled through a
liquid-liquid extraction of oil-soluble impurities using
triacylglycerides (TAG) as solvent. Vegetable oil (corn oil) was
tested as the hydrophobic solvent since it is abundant at many
biodiesel facilities. This separation was based on the large
density difference between the hydrophobic solvent (0.88 g/ml for
corn oil) and glycerol (1.26 g/ml) at a reduced glycerol viscosity
(81.3 cp at 60.degree. C.). Corn oil was combined with the crude
glycerol (5:95 vol/vol) in a tank mixer, and thoroughly mixed at
60.degree. C. for 5 minutes. The resulting crude glycerol-corn-oil
mixture was separated into an oil phase and a deoiled glycerol
phase by centrifugation at 20 g-force with a bucket centrifuge for
5 minutes at 40.degree. C. This g-force was chosen because it is
similar to what can be achieved by a hydro-cyclone. A low speed
liquid-liquid centrifugal separator (CINC L-L) having about 1000
g-force may provide a similar or effective separation. As shown in
Table 2 below, the organic impurities were significantly reduced in
the resulting DO glycerol (from 394 ppm to 192 ppm).
TABLE-US-00003 TABLE 2 Characteristics of Glycerol Stages While
Comparing Crude Glycerol to Partially Refined Waste Glycerol (DO-,
DOW-, DOWS Glycerol) Crude DOWS-2 Unit Glycerol DO Glycerol DOW
Glycerol Glycerol Glycerol Refining None Deoiled Deoiled and
Deoiled, Dried Process Dried and Desalted Glycerol Content % 81.99
82.0 92.66 97.94 NaCl % 6.42 6.42 7.25 2.0 Water % 11.56 11.56 0.07
0.12 Organic Impurities ppm 342 192 222 222
Example 2: Process of Producing Deoiled (DO) Glycerol Using Hexane
as Hydrophobic Solvent
[0093] Hexane can be used as an alternative hydrophobic solvent for
deoiling of crude glycerol as shown in Example 1. Hexane has a
boiling point of 69.degree. C., 145 btu/lb heat of vaporization
(.DELTA.Hv), and 0.53 btu/lb.degree. C. heat capacity (Cp).
Deoiling is achieved via hydrophobic solvent liquid-liquid
extraction using a low volume of hexane and a flash evaporator
unit. Hexane is thoroughly mixed with the crude glycerol at
5:95-20:80 (vol/vol) at ambient temperature for 5-30 minutes. The
resulting mixture is then separated into an organic light phase and
a glycerol heavy phase using a hydro-cyclone or a low-speed
liquid-liquid centrifugal separator. Hexane is recovered from the
extracted organic impurities by flash evaporation and recycled. The
evaporator bottoms containing the organic impurities can be used as
fuel for value recovery and reduction of waste. The DO glycerol is
expected to have a decrease in organic impurities similar to or
better than that achieved using vegetable oil.
Example 3: Process of Producing Deoiled and Dewatered (DOW)
Glycerol by Dewatering DO Glycerol
[0094] DO glycerol (from Example 1) contained about 12% water. In
order to remove this water, a moisture drying process was carried
out at 100.degree. C. and 60 ton, using a lab scale glass
evaporator. A shown in Table 2 (supra), the resulting deoiled and
dewatered (DOW) glycerol contained less than 0.5% moisture content
(water). While not determined, trace levels of methanol and low
boiling point species are expected to be reduced along with water
from the glycerol during the dewatering process. The DOW glycerol
still contained about 7.25% salt.
Example 4: Process of Producing Deoiled, Dewatered and Desalted
(DOWS) Glycerol by Desalting DOW Glycerol Via IPA Precipitation
[0095] As shown in Table 2 (supra), DOW glycerol contained 7.25%
NaCl. In order to decrease the concentration of NaCl, desalting was
carried out by isopropanol (IPA) precipitation and density
separation. IPA was thoroughly mixed with DOW glycerol in a mixing
tank at 3.2:1 IPA:DOW glycerol (wt/wt) at 60.degree. C. for 30
minutes, and the resulting super salt saturated mixture was
agglomerated for 30 minutes at 60.degree. C. This temperature
(60.degree. C.) was selected because it permitted almost complete
salt precipitation at a temperature 22.3.degree. C. below the
boiling point of IPA while supporting a favorable viscosity of the
resulting mixture for rapid settling of crystallized NaCl,
including fine crystals. The solids were then removed by density
separation, using a bucket centrifuge at 20 g-force for 5 minutes
at 40.degree. C. The liquid glycerol-IPA mixture was decanted, and
the IPA was removed by evaporation at 80.degree. C. and 60 torr. As
shown in Table 2 (supra), the resulting deoiled, dewatered, and
desalted (DOWS) glycerol contained significantly less NaCl (1.94%)
than DOW glycerol (7.25%). The sample in Table 2 is referred to as
DOWS-2 glycerol (i.e., glycerol containing about 2% salt), where
the 1.94 refers to the concentration (wt/wt) of NaCl in the DOWS
glycerol.
Example 5: Process of Producing Deoiled, Dewatered and Desalted
(DOWS) Glycerol by Desalting DOW Glycerol Via IPA Precipitation and
Partial Glycerol Evaporation
[0096] An alternative way of decreasing the salt concentration of
DOW glycerol by IPA precipitation is to evaporate a majority of the
glycerol in DOW glycerol, and then remove the salt remaining in the
evaporation bottom by IPA precipitation as shown in Example 4. In
this way a smaller volume of IPA needs to be used in the
precipitation, a salt free glycerol can be recovered through
evaporation, and the salt content of the final partially refined
waste glycerol can be adjusted by appropriate blending of
evaporated glycerol with IPA precipitated DOW glycerol. DOW
glycerol was first treated at 152.3.degree. C. vapor temperature at
5 torr until 75% of the glycerol had evaporated. As shown in Table
3 below the evaporated glycerol (DOWS-0 glycerol) (i.e., DOWS
glycerol containing about 0% salt) was significantly purified and
contained only 0.023% NaCl. The super salt saturated glycerol
evaporation bottom was thoroughly mixed with IPA at 5.7:1 IPA: DOW
glycerol evaporation bottom (wt/wt) in a mixing tank at 60.degree.
C. for 5 minutes, and the resulting mixture was agglomerated for 30
minutes at 60.degree. C. The solids were removed by density
separation in a bucket centrifuge by applying 20 g-force for 5
minutes at 40.degree. C. The liquid IPA glycerol supernatant was
decanted, and the IPA was recovered by flash evaporation (supra).
As shown in Table 3 below (infra), the resulting glycerol in the
evaporation bottom contained 0.97% (wt/wt) NaCl, and this sample is
referred to as DOWS-1 glycerol (i.e., DOWS glycerol containing
about 1% salt).
TABLE-US-00004 TABLE 3 Fatty Acid Methyl Ester (FAME) Production
with DOWS Glycerol Compositions as Feedstock USP Units Grade DOWS-0
DOWS-0.1 DOWS-0.5 DOWS-1 Glycerol Feed Glycerol Content % 99.5 99.5
99.7 99.2 98.8 NaCl % N/A 0.023 0.1 0.5 0.97 Organics ppm N/A 60
110 240 639 Water % 0.5 0.46 0.21 0.29 0.15 Methanol % N/A N/A N/A
N/A N/A Fermentation Fermentation Yield % 24.2 20.4 22.5 22.2 26.5
Fermentation Productivity g/l/hr 1.33 1.08 1.20 1.16 1.45
Fermentation Titer g/kg 95.4 77.2 86.2 83.4 103.9 Harvest
Centrifugation Yield % 54.2 43.2 69.2 60.3 87.0 Crude FAME Acid No.
mg KOH/g 3.49 4.63 4.46 4.18 3.23 Carbonyl ppm 3026 2794 2079 2377
2239 Moisture % 2.23 2.01 2.23 2.43 1.63
Example 6: Process of Desalting Crude Glycerol
[0097] In order to evaluate the quality of desalted crude glycerol
that was not deoiled, crude glycerol was directly desalted by IPA
precipitation as shown in Example 3. As shown in Table 4 below the
resulting desalted (DS) glycerol contained 2% (wt/wt) NaCl (see
DS-2).
TABLE-US-00005 TABLE 4 Fermentation Comparison for FAME Production
USP Crude Unit Glycerol Glycerol DO glycerol DS-2 DOWS-2 Glycerol
Feed Glycerol % 99.5 82.0 92.66 96.97 97.92 Oil-Soluble ppm 0 533
191 570 222 Organics Salt (NaCl) % 0 6.4 7.25 2.0 2.0 Water % 0.5
11.56 0.07 1.03 0.12 Fermentation Fermentation hr 72 48 72 72 72
Time Yield % 21.9 16.4 19.8 19.2 19.5 Productivity g/l/hr 1.158
0.478 0.519 0.873 0.938 Titer g/kg 83.7 35.9 44.0 62.9 67.5
Example 7: Process for the Preparation of a DOWS Composition that
was Salt-Tailored with NaCl by Blending Different Refined Glycerol
Samples
[0098] Since different applications for partially refined waste
glycerol exist, glycerol can benefit from having different salt
concentrations. Various DOWS glycerol compositions with a NaCl
content ranging from 0 to 7.25% were made. These compositions were
prepared by controlling the ratio of the IPA to glycerol in the IPA
precipitation step. IPA was thoroughly mixed with DOW glycerol at
varying ratios, and the samples were processed as described in
Example 3 (supra). As shown in FIG. 6, at lower ratios, higher salt
concentrations result, while at higher ratios lower salt
concentrations result.
Example 8: Process for the Preparation of a DOWS Composition that
was Salt-Tailored with NaCl by Controlling the Ratio of IPA to
Glycerol in the IPA Precipitation Process
[0099] Since different applications of partially refined waste
glycerol may benefit from different salt concentrations in the
glycerol, DOWS glycerol compositions containing NaCl ranging from 0
to 1% were prepared by blending the evaporated glycerol (DOWS-0)
with DOWS-1. Various samples were prepared by using this method as
shown in Table 5 (infra).
TABLE-US-00006 TABLE 5 Examples of Salt-Tailored Glycerol
Compositions DOWS-0 DOWS-0.1 DOWS-0.5 DOWS-1 No Salt 0.1% Salt 0.5%
Salt 1.0% Salt NaCl % in DOWS 0.023% 0.1% 0.5% 0.97 Glycerol Blend
Ratio 1:0 9:1 1:1 0:1 (DOWS No Salt:DOWS 1.0% Salt)
Example 9: Testing Various Forms of Glycerol in a Fame
Fermentation
[0100] This example compares the use of crude glycerol, DO
glycerol, DS-2 glycerol (desalted to 2% salt), DOWS-2 glycerol
(containing about 2% salt), and USP glycerol, as the sole carbon
source in fermentation using an organism that does not tolerate
crude glycerol well. As a representative example, the fermentation
chosen was one to produce fatty acid methyl esters (FAME) using an
engineered E. coli biocatalyst. Each sample was prepared as
described above, and the specifications of each glycerol sample and
how they performed as a carbon source in fermentations are shown in
Table 4 (supra). These data demonstrate that partial refining of
crude glycerol using the methods described herein significantly
improve its ability to support efficient fermentation. In
particular both the decrease in organic and salt impurities
increase fermentation performance in comparison to crude
glycerol.
Example 10: Testing Salt-Tailored DOWS Glycerol Compositions in a
Fame Fermentation
[0101] This example investigates the feasibility of salt-tailored
DOWS glycerol in fermentations, wherein the DOWS glycerol
compositions contain a specifically tailored salt content and
reduced oil-soluble organic impurities. DOWS 0, 0.1, 0.5, and -1
glycerol were made from crude glycerol as described above and in
Example 8 and shown in Table 5.
[0102] In the fermentation evaluation, the DOWS glycerol samples
supported comparable FAME yield, productivity and titer (YPT) and
produced similar quality of FAME product as compared to USP grade
glycerol. However, as shown in Table 3 (supra), DOWS-1 surprisingly
out-performed the USP glycerol in these fermentations. These data
suggest that partially refined glycerol is superior to USP glycerol
as a fermentation feedstock and that salt tailored DOWS is a useful
tool for the production of high performance fermentation feedstocks
from waste glycerol. Indeed, these data demonstrate that the salt
impurities in waste glycerol that traditionally are considered an
inhibitor to fermentation can be leveraged to improve
fermentation.
Example 11: Evaluation of the Impact of Salt Tailored DOWS on the
Recovery of FAME from Fermentation Broths
[0103] Impurities in feedstocks can influence the efficiency of
product recovery from fermentation broths. In order to evaluate the
impact of different DOWS of tailored salt concentration on FAME
recovery from fermentation broths, oil was recovered from each
fermentation described in Example 10. The broth from each of the
fermentation described in Table 3 (supra) was gravity separated
using a bucket centrifuge at 5000 g-force for 15 minutes at
40.degree. C., and the light oil phase containing the FAME from
each sample was recovered by decantation. The efficiency of FAME
recovery from the broth is reported as the percent of FAME
recovered as compared to the total FAME in the broth before
centrifugation. As shown in Table 3 (supra), recovery was most
efficient from the fermentation broth of DOWS-1 followed by those
that had salt. Recovery was least efficient from USP and DOWS-0.
This data suggests that tailoring the level of impurities remaining
in partially refined waste glycerol can provide a benefit on
fermentation and product recovery processes and that DOWS-1 is a
good fermentation feedstock.
[0104] As is apparent to one with skill in the art, various
modifications and variations of the above aspects and embodiments
can be made without departing from the spirit and scope of this
disclosure. Such modifications and variations are within the scope
of this disclosure.
* * * * *