U.S. patent application number 12/048028 was filed with the patent office on 2008-09-18 for methods for producing triol ethers by reactive distillation.
This patent application is currently assigned to ENDICOTT BIOFUELS II, LLC. Invention is credited to William Douglas Morgan.
Application Number | 20080228011 12/048028 |
Document ID | / |
Family ID | 39760037 |
Filed Date | 2008-09-18 |
United States Patent
Application |
20080228011 |
Kind Code |
A1 |
Morgan; William Douglas |
September 18, 2008 |
Methods for Producing Triol Ethers by Reactive Distillation
Abstract
This invention relates to methods for preparing alkyl ethers
from glycerin by reactive distillation. For example, the present
invention provides a method for the preparation of mono-, di- and
tri-ethers of glycerin, either in the presence or absence of fatty
acids, contaminants by reactive distillation using solid catalysts.
Specific desirable final products according to the reactive
distillation method provided herein include glycerin ethers and
fatty acid esters of C.sub.4-C.sub.5 alcohols, such as for example,
isobutanol, tert-butanol, and isoamyl alcohol.
Inventors: |
Morgan; William Douglas;
(Richmond, CA) |
Correspondence
Address: |
KING & SPALDING, LLP
1100 LOUISIANA ST., STE. 4000, ATTN.: IP Docketing
HOUSTON
TX
77002-5213
US
|
Assignee: |
ENDICOTT BIOFUELS II, LLC
Houston
TX
|
Family ID: |
39760037 |
Appl. No.: |
12/048028 |
Filed: |
March 13, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60894724 |
Mar 14, 2007 |
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60894726 |
Mar 14, 2007 |
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60894730 |
Mar 14, 2007 |
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Current U.S.
Class: |
568/671 |
Current CPC
Class: |
C11C 3/003 20130101;
Y02P 20/127 20151101; C07C 41/09 20130101; Y02P 20/10 20151101;
Y02E 50/13 20130101; Y02E 50/10 20130101; C10L 1/026 20130101; C07C
41/09 20130101; C07C 43/13 20130101; C07C 41/09 20130101; C07C
43/135 20130101; C07C 41/09 20130101; C07C 43/10 20130101 |
Class at
Publication: |
568/671 |
International
Class: |
C07C 41/01 20060101
C07C041/01 |
Claims
1. A process for the production of glycol ethers by reactive
distillation, comprising: continuously introducing an alcohol vapor
feedstream to a distillation column; continuously introducing a
glycol feedstream to the distillation column; catalytically
reacting the alcohol and glycol feedstreams in a reaction zone
within the distillation column to form; stripping water from the
reaction zone with the alcohol vapor; separating the water from the
alcohol vapor and recycling the alcohol to the bottom of the
distillation column; collecting the mono-, di- and tri-glycol ether
products.
2. The process of claim 1 wherein the alcohol is selected from
isobutanol, isoamyl alcohol and tert-butanol.
3. The process of claim 1 wherein the reaction zone includes a
solid ion exchange catalyst, said catalyst including SO.sub.3H and
CO.sub.2H reactive groups.
4. The process of claim 1 wherein the reaction zone includes
trays.
5. The process of claim 1 wherein the reaction zone includes
structured packing.
6. The process of claim 1 wherein the alcohol is introduced to the
bottom of the distillation column.
7. The process of claim 1 wherein the glycerin is introduced to the
top of the distillation column.
8. A process for the preparation of tert-butyl triol-ethers,
comprising: continuously introducing tert-butanol to the bottom of
a reactive distillation column; continuously introducing glycerin
to the top of said distillation column; heating the alcohol to form
a stripping vapor; reacting said glycerin and said stripping vapor
in a reaction zone, said reaction zone located between the top and
bottom of the distillation column; collecting said stripping vapor
from the top of the distillation column; recycling said stripping
vapor to the distillation column; and collecting a triol-ether
product from the bottom of said distillation column.
Description
[0001] This application claims priority under 35 U.S.C. 119(e) to
U.S. provisional application 60/894,724, filed Mar. 14, 2007, U.S.
provisional application 60/894,726, filed Mar. 14, 2007, and U.S.
provisional application 60/894,730, filed Mar. 14, 2007. The
contents of each of the above-listed applications are incorporated
by reference.
FIELD OF THE INVENTION
[0002] This invention relates to methods for preparing alkyl ethers
from glycerin by reactive distillation.
BACKGROUND
[0003] Glycerin (propane-1,2,3-triol, also known as glycerol), is a
product of the splitting of triglycerides from fats as the
triglycerides are separated into component fatty acids and
glycerin. During transesterification of triglycerides (typically
conducted in the presence of basic catalysts), large amounts of
crude glycerin are produced. For example, in the
transesterification of triglyceride oil, such as for example, that
obtained from soybeans, with methanol, approximately 20% of crude
glycerin is generated for which applications must be found.
Purification of glycerin obtained from transesterification for
commercial application is difficult and expensive, even to obtain
poor quality product of questionable value. One major constituent
of crude glycerin is fatty acid from the original triglyceride
oil.
[0004] Currently, the relatively high price of biodiesel compared
to diesel oils derived from petroleum is one obstacle to the
complete commercial acceptance of biodiesel as an alternative fuel
source. Additionally, use of biodiesel fuels is frequently limited
in practice, due in part to inferior physical properties at low
temperatures. For example, the cloud point of soya biodiesel (the
lowest temperature at which a fluid can remain as a fluid without
becoming turbid or beginning to crystallize) is near zero degrees
centigrade (0.degree. C.), whereas the cloud point of
petroleum-derived diesels is typically around -16.degree. C.
Similarly, freezing points for biodiesel oils are around -2.degree.
C., compared with -27.degree. C. for petroleum-derived diesel oils.
These inferior physical properties of the biodiesel compared to
conventional petroleum based diesels cause problems at low
temperatures. A viable new use for crude glycerin byproduct
improves the economics of the transesterification of triglycerides.
It further benefits the biodiesel producer if the product formed
from the glycerin can be used to improve physical properties of
biodiesel.
[0005] One viable candidate for such glycerin based products
includes alkyl ethers of glycerin. Production of glycerin ethers
from an alcohol such as isobutanol yields mono-, di-, and tri-
(tertiary) butyl ethers of glycerol.
[0006] A further advantage in the production of alkyl ethers of
glycerin is that the same class of acid catalysts such as for
example, Amberlyst resins and the like catalyze both the
etherification of glycerin and the esterification of fatty acids
that will most likely contaminate glycerin produced during
Biodiesel production.
[0007] Because of reaction equilibrium constraints, the
etherification of glycerin readily achieves high conversions when
conducted simultaneously with vapor liquid equilibrium stage
operations. Those skilled in the art refer to the combination of
reaction and vapor liquid equilibrium stage operations as "reactive
distillation".
[0008] Therefore, procedures to transform glycerin by itself, or in
admixture with the fatty acids that normally contaminate it, into
compounds that can be mixed with biodiesel to improve the biodiesel
properties have been investigated. Specifically, the production of
compounds to improve biodiesel properties at low temperature and to
improve combustion is an objective of great technical and
commercial value.
SUMMARY
[0009] The present invention provides a method for the preparation
of mono-, di- and tri-ethers of glycerin, either in the presence or
absence of fatty acids, contaminants by reactive distillation using
solid catalysts. Specific desirable final products according to the
reactive distillation method provided herein include glycerin
ethers and fatty acid esters of C.sub.4-C.sub.5 alcohols, such as
for example, isobutanol, tert-butanol, and isoamyl alcohol.
[0010] The process includes continuously introducing an alcohol
vapor feedstream and a glycerol feedstream to a distillation
column. Preferably, the alcohol feedstream is introduced to the
bottom of the distillation column as a vapor and often to the top
as a liquid, while the glycerin feedstream, which may include fatty
acids, is introduced to the top of the distillation column. The
alcohol and glycerin, as well as any fatty acids, are catalytically
reacted in the combination reaction/distillation zone of the
column. The vapor liquid equilibrium stages ensure that water
produced by the production of ethers and esters is removed from the
reaction phase as it is formed, thereby favoring a higher
conversion than permitted by the reaction equilibrium when the
water is allowed to remain in the reaction phase.
[0011] The reaction column is operated such that water and excess
alcohol exit as a vapor from the top of the column. Water may be
separated from the excess alcohol and the alcohol may be recycled
to the reaction column. Product mono-, di- and tri-triol ethers
along with any fatty acid esters formed exit the column from the
bottom as a liquid.
[0012] In one embodiment, the alcohol is selected from isobutanol,
tert-butanol, and isoamyl alcohol. In one embodiment, the reaction
zone includes a solid ion exchange catalyst, wherein the catalyst
includes SO.sub.3H and CO.sub.2H reactive groups.
[0013] In a preferred embodiment, isobutanol and/or tert-butanol is
supplied to the bottom of a distillation column in vapor form and
liquid glycerol (with or without fatty acid contamination) is
supplied to the top of the distillation column in liquid form. It
may also be desirable under certain conditions to supply liquid
butanols to the top of the column along with the vapor to the
bottom of the column. The isobutanol and/or tert-butanol proceed
counter currently with the glycerin and fatty acids and through the
vapor liquid equilibrium stages simultaneously reacting to their
respective ethers and esters. The equilibrium stages are designed
to hold a solid catalyst, preferably an ion exchange resin having
either --SO.sub.3H or --CO.sub.2H functional groups present, in
such a way that the catalyst is exposed to liquid containing
alcohol and either glycerin or fatty acid or both. Water is removed
from the reaction phase as it is created. The tert-butanol,
isobutanol and water are subsequently separated using any of a wide
range of separation technologies such that the alcohols may be
recycled to the bottom of the distillation column as a vapor and to
the top of the column as a liquid, if desired. Mono-, di- and
tri-tert-butyl ethers of glycerin, and the tert-butyl esters of
fatty acids if present in the feed glycerin, are collected from the
bottom of the distillation column.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 shows an embodiment for the production of triol
ethers by reactive distillation.
[0015] FIG. 2 shows an embodiment for the production of triol
ethers by reactive distillation with alcohol recycle.
[0016] FIG. 3 shows an embodiment for the production of biodiesel
fuel containing a triol ether additive.
[0017] FIG. 4 shows an embodiment for the production of triol
ethers by reactive distillation with
pre-etherification/esterification and alcohol recycle.
DETAILED DESCRIPTION
[0018] According to the present invention and with reference to the
accompanying drawings, a continuous process for the production of
glycerol ethers by reactive distillation of glycerin, potential
fatty acid contaminants, and alkanols with a heterogeneous catalyst
is provided. The catalyzed reaction of glycerin and alkanol occurs
in a reaction column equipped with vapor liquid equilibrium
affecting devices. The glycerin ether and fatty acid ester products
of the reaction find use as additives that can be used to improve
cloud-point, viscosity, pour-point, and cold flow plugging point of
biodiesel.
Etherification by Reactive Distillation
[0019] As shown in FIG. 1, glycerol (1,2,3-propane triol) 1 is fed
via line 2 to the upper portion of and optionally via line 18 to
the upper portion of reaction column 5. Similarly, alkyl alcohol 3
is introduced via line 4 to the lower portion of the column 5.
Preferably, the glycerol 1 is introduced above the reaction zone 6,
and the alcohol 3 is introduced below reaction zone 6. The alcohol
is present as a vapor and flows counter-current to the liquid
glycerol, which is preferably present in the reaction as a
liquid.
[0020] As noted herein, any suitable C.sub.1-C.sub.6 straight or
branched alcohol may be used, most preferably tert-butanol,
isobutanol or mixtures thereof.
[0021] Reaction of the alcohol and glycerin produces a mono-ether
and water. Subsequent reaction of the mono-ether produces the
di-ether and water, and further reaction of the di-ether produces
the tri-ether and water.
[0022] The column is preferably configured for reactive
distillation using a solid catalyst. Such columns employ one or
more vapor liquid equilibrium affecting devices that serve to hold
the catalyst. As used herein, a vapor liquid equilibrium stage can
also be described as a tray or plate. General commercial examples
of stages, trays, and plates include bubble cap trays, valve trays,
sieve trays, random packing, and structured packing. Regardless of
the specific design employed by a given manufacturer, the
objectives are to affect vapor liquid equilibrium in a stage-wise
fashion and to hold solid catalyst. An exemplary column and several
vapor liquid equilibrium stage/catalyst supporting means suitable
for use herein are described in U.S. Pat. No. 5,536,856 (Harrison,
et al.). A specific, long term commercial product known as Katapak
consistent with the some of the designs of the vapor equilibrium
stages described in U.S. Pat. No. 5,536,856 is described in U.S.
Pat. No. 5,831,120 (Watson et al).
[0023] Generally, of the two or three reaction components, the
reactant with the lower boiling point is introduced at the bottom
of the distillation column and is present in the reaction as a gas,
while the reactant with the higher boiling point is introduced at
the top of the distillation column and is present as a liquid. The
alcohol vapor serves as a stripping vapor, aiding in the removal of
water from the reaction vessel, as the majority of the water is
exits the distillation column out the top of the vessel with the
alcohol effluent.
[0024] Reaction zone 6 includes a solid catalyst for the
etherification of glycerol. A variety of solid catalysts may be
used. Preferably, the catalyst is an ion exchange resin which
includes sulfonic acid (--S(O).sub.2OH) or carboxylic acid
(--C(O)OH) reactive groups, or a mixture thereof. Suitable
arrangement is made for holding the catalyst in the region where
vapor liquid equilibrium is taking place. A synthetic zeolite or
other type of mixed or singular oxide ceramic material with
sufficient acidity could also be employed. In columns employing
multiple incidents of catalyst zones, several different catalysts,
or multiple different concentrations of catalyst, may be
employed.
[0025] In the reactive distillation process according to Harrison
(as described in U.S. Pat. No. 5,536,856), the distillation column
includes a plurality of vapor liquid equilibrium stage devices that
also hold catalyst called "trays", the number of which may be
determined according to the desired volume of the reactor, the
boiling points of the reactants, and the desired product (i.e., the
mono-, di- or tri-ether). In the reactive distillation process
according to Watson (as described in U.S. Pat. No. 5,831,120), the
equilibrium stages are called "packing" and may include porous
catalyst supports and flow channels for affecting vapor liquid
equilibrium and contacting the liquid phase with the catalyst.
[0026] The alcohol, having the lower boiling point, exits the
distillation column overhead via line 7. Because of the vapor
liquid equilibrium stage action of the column and its stages,
excess alcohol and water from the etherification reaction exits the
column as a vapor from the top. The water/alcohol mixture exiting
via line 7 may be separated by known separation processes 8, such
as for example, by distillation, and the alcohol may preferably be
recycled to the distillation column via lines 11 and 18. Waste
water exits the water/alcohol separation process via line 10.
[0027] The glycerin ether and fatty acid ester products exit
distillation column 5 as a liquid via line 9. The product stream
may include mono-, di- and tri-triol ethers, and may also include
unreacted glycerol as well as esters of any fatty acids introduced
with the glycerin feed.
[0028] In order to generate the vapor phase necessary for the vapor
liquid equilibrium action of the column, a reboiler (not shown) may
be employed. Alternatively, the alcohol fed to the bottom is
vaporized by external means.
[0029] As shown in FIG. 2, product stream 9, which may include
mono-, di- and tri-ethers of glycerol as well as esters of fatty
acids may be introduced to a separation process 12. Separator 12
includes means known in the art, such as for example a distillation
column, and may preferably be used to produce a product stream 14
rich in di- and tri-ethers of Triol and a recycle stream 13 rich in
mono-ethers of Triol and unreacted Triol. Recycle stream 13 may
then be combined with feed stream 2, or optionally be introduced
separately, to distillation column 5.
[0030] As shown in FIG. 3, product stream 14, preferably rich in
di- and tri-ethers of Triol, may be added to a mixing process to
which biodiesel (preferably fatty acids of methyl esters) is added
via line 16. Depending on the biodiesel feedstock, the amount of
Triol ether may be adjusted. Preferably, the resulting
biodiesel-additive product 17 includes at least 2%, at least 3%, at
least 4%, at least 5%, at least 6%, at least 7%, at least 8%, at
least 9% or at least 10% by weight Triol ether additive. Any fatty
acid esters formed as a result of the presence of fatty acids in
the glycerin will have desirable low temperature properties that
will compliment the effect of the glycerin ethers when added in
combination.
[0031] Optionally, the triol ether fuel additive can be directed
added to a biodiesel or petroleum based diesel fuel, without
further reaction or purification (not shown). Due to the use of an
ion exchange resin or structured packing, residual catalyst
typically does not have to be removed from the product material.
Additionally, prior to addition of the additive, it may be
optionally dried by known means, such as for example, by passing
through a drying agent (e.g., calcium sulfate).
[0032] As shown in FIG. 4, at times it is preferable to perform a
portion of the etherification and esterification in a fixed bed
reactor containing a charge of catalyst upstream of the reaction
column. This helps ensure high conversion, while at the same time
reducing the number of stages and amount of catalyst required in
the reaction column. As shown in FIG. 4, glycerin stream 2, with or
without fatty acids, can be mixed with recovered alcohol stream 24
and introduced to pre-reactor 19. Prereactor 19 can be charged with
a catalyst similar to that used in the reaction column. Following
the reaction in pre-reaction 19, wherein at least a portion of the
glycerin has been etherified and some of the fatty acids have been
esterified, the stream 20 is supplied to flash drum 21. The flash
drum 21 separates the reaction mixture into a liquid stream 22 and
a vapor stream 23, each of which can be fed to the top of the
reaction column 5.
Glycerin
[0033] As shown in FIG. 4, at times it is preferable to perform a
portion of the etherification and esterification in a fixed bed
reactor containing a charge of catalyst upstream of the reaction
column. This helps ensure high conversion, while at the same time
reducing the number of stages and amount of catalyst required in
the reaction column. As shown in FIG. 4, glycerin with or without
fatty acids are mixed with recovered alcohol from stream 14 and
sent to pre-reactor 2. Prereactor 2 is charged with a catalyst
similar to that used in the reaction column. Following the reaction
in pre-reaction 2, some of the glycerin has been etherified and
some of the fatty acids have been esterified. The product of
prereactor 2 is sent by stream 3 to a flash drum, 4, for separation
of liquid and vapor streams with both being fed to the top of the
reaction column, the vapor stream being fed higher.
[0034] As shown in FIG. 4, at times it is preferable to perform a
portion of the etherification and esterification in a fixed bed
reactor containing a charge of catalyst upstream of the reaction
column. This helps ensure high conversion, while at the same time
reducing the number of stages and amount of catalyst required in
the reaction column. As shown in FIG. 4, glycerin with or without
fatty acids are mixed with recovered alcohol from stream 14 and
sent to pre-reactor 2. Prereactor 2 is charged with a catalyst
similar to that used in the reaction column. Following the reaction
in pre-reaction 2, some of the glycerin has been etherified and
some of the fatty acids have been esterified. The product of
prereactor 2 is sent by stream 3 to a flash drum, 4, for separation
of liquid and vapor streams with both being fed to the top of the
reaction column, the vapor stream being fed higher.
Catalyst
[0035] The solid catalysts, capable of catalyzing both the desired
etherification and esterification suitable for use in the
invention, range from acidic zeolites and other silicas, alumina,
and titanias, to granular ion exchange resin containing sulfonyl
acid (--SO.sub.3H) and/or carboxylic acid (--COOH) groups.
Macroreticular resins of this type are preferred. Examples of
suitable resins are those sold under the trade marks "Amberlyst",
"Dowex", "Dow" and "Purolite" such as AMBERLYST 13, AMBERLYST 66,
DOW C351, and PUROLITE C150. The same catalyst can be employed at
multiple stages or different catalysts can be used at different
stages.
[0036] Preferably, the catalyst employed is stable at the
temperatures at which the reaction is run. For example, if any of
methanol, ethanol, n-propanol, isopropanol, n-butanol or isobutanol
are used as the alcohol, then the catalyst (as an ion exchange
resin) must be able to be operate at temperatures between
120.degree. C. and 140.degree. C.; preferably having only a
moderate activity loss at this temperature range. When alcohols
having higher boiling points are employed, the catalyst similarly
must be able to operate, and must have only a moderate activity
loss, at higher temperatures which correspond to the boiling point
of the alcohol being used.
[0037] When the distillation column includes trays, the charge of
solid particulate or granular etherification catalyst on an
equilibrium stage should typically be sufficient to provide a
catalyst:liquid ratio on that tray corresponding to a resin
concentration of at least 0.2% w/v, for example a resin
concentration in the range of from about 2% w/v to about 20% w/v,
preferably 5% w/v to 10% w/v, calculated as dry resin. Sufficient
catalyst should be present to enable equilibrium or near
equilibrium conditions to be established on the tray or in the
packing within the selected residence time at the relevant
operating conditions. However, the amount of catalyst should be
maintained such the upflowing vapor entering the tray from below
can sufficiently agitate the catalyst on the tray. For a typical
resin catalyst a resin concentration in the range of from about 2%
v/v to about 20% v/v, preferably 5% v/v to 10% v/v may be used.
[0038] In another embodiment, the catalyst may be a fixed-bed
catalyst. In this case, the reaction column may be operated as a
trickle column of which about 30 to 60 vol %, preferably
approximately 50 vol % are utilized by the stripping gas as free
gas space, whereas 30 to 50 vol %, preferably approximately 40 vol
% of the column is occupied by solid substance, i.e. the fixed-bed
catalyst. The remaining reaction space, preferably approximately 10
vol % or less, may be occupied by the trickling liquid.
[0039] The residence time of the liquid phase in the distillation
column can be adjusted by the stripping gas velocity. With higher
gas velocities, the residence time of the liquid phase is typically
high. Generally, the stripping gas throughput can be adjusted over
a wide range without having an adverse effect on the course of
process.
[0040] While many acid catalysts suitable for performing
etherifications can be used, in an effective amount and an
effective concentration, solid catalysts having acidic functional
groups are preferred. Solid catalysts are preferred mainly because
of the minimization of purification steps required in processing
the product stream. Examples of suitable acids may include, but are
not limited to, hydrochloric acid, hydrobromic acid, sulfuric acid,
and nitric acid. Preferably, the acid catalyst is a strong acid,
more preferably sulfuric acid.
Alcohols
[0041] Alcohols suitable for use in the present etherification
reaction can include any C.sub.1-10 straight, branched, or cyclic
alcohols. Preferably, the alcohol is a C.sub.4 or C.sub.5 alcohol,
such as for example, tert-butanol, isobutanol, and/or isoamyl.
Anhydrous alcohols are preferred, although because of the use of a
reactive distillation column, any water which is present in the
reaction mixture is typically removed by the stripping action of
the alcohol vapor. Alcohol will typically be employed in excess to
that required stoichiometrically.
[0042] Modifications and variations of the present invention
relating to a fuel additive composition and an alternative fuel
derived from the composition are encompassed in the foregoing
detailed description of the invention. Such modifications and
variations are intended to come within the scope of the appended
claims. Similarly, the drawings are diagrammatic and additional
equipment, such as for example, reflux drums, pumps, vacuum pumps,
temperature sensors, pressure sensors, pressure relief valves,
control valves, flow controllers, level controllers, holding tanks,
storage tanks, and the like may be required in a commercial
plant.
* * * * *