U.S. patent application number 12/845519 was filed with the patent office on 2012-02-02 for methods for producing phase stable, reduced acid biomass-derived pyrolysis oils.
This patent application is currently assigned to UOP LLC. Invention is credited to Timothy A. Brandvold, Mark B. Koch.
Application Number | 20120023809 12/845519 |
Document ID | / |
Family ID | 45525262 |
Filed Date | 2012-02-02 |
United States Patent
Application |
20120023809 |
Kind Code |
A1 |
Koch; Mark B. ; et
al. |
February 2, 2012 |
METHODS FOR PRODUCING PHASE STABLE, REDUCED ACID BIOMASS-DERIVED
PYROLYSIS OILS
Abstract
Methods for producing phase stable, reduced acid biomass-derived
pyrolysis oils are provided. Biomass-derived pyrolysis oil having a
determined water content no greater than about 30% by weight is
provided. A base is mixed with the biomass-derived pyrolysis oil to
produce reduced acid biomass-derived pyrolysis oil. A base is
selected from an inorganic base or a nitrogen-containing base.
Inventors: |
Koch; Mark B.; (Mount
Prospect, IL) ; Brandvold; Timothy A.; (Arlington
Heights, IL) |
Assignee: |
UOP LLC
Des Plaines
IL
|
Family ID: |
45525262 |
Appl. No.: |
12/845519 |
Filed: |
July 28, 2010 |
Current U.S.
Class: |
44/307 |
Current CPC
Class: |
Y02P 30/20 20151101;
C10L 1/04 20130101; C10L 1/02 20130101 |
Class at
Publication: |
44/307 |
International
Class: |
C10L 1/10 20060101
C10L001/10 |
Claims
1. A method for producing phase stable, reduced acid
biomass-derived pyrolysis oil comprising the steps of: providing a
biomass-derived pyrolysis oil having a determined water content no
greater than about 30% by weight; and mixing a base with the
biomass-derived pyrolysis oil.
2. The method of claim 1, wherein the step of mixing comprises
selecting the base comprising an inorganic base selected from the
group consisting of a metal oxide, a metal hydroxide, a metal
alkoxide, and a metal carbonate of the alkali and alkaline earth
metals, alkali and alkaline earth exchanged zeolites, a mixed metal
oxide, and combinations thereof.
3. The method of claim 2, wherein the step of mixing comprises
selecting the metal oxide from the group consisting of calcium
oxide, magnesium oxide, and combinations thereof.
4. The method of claim 2, wherein the step of mixing comprises
selecting a metal hydroxide from the group consisting of LiOH,
NaOH, KOH, RbOH, CsOH, Mg(OH).sub.2, Ca(OH).sub.2, Sr(OH).sub.2,
Ba(OH).sub.2, and combinations thereof.
5. The method of claim 2, wherein the step of mixing comprises
selecting a metal alkoxide from the group consisting of sodium
ethoxide, potassium tert-butoxide, and combinations thereof.
6. The method of claim 1, wherein the step of mixing comprises
selecting a nitrogen-containing base comprising an amine, a
tetraalkylammonium hydroxide, or combinations thereof.
7. The method of claim 6, wherein the step of mixing comprises
selecting the amine from the group comprising a dialkyl amine, a
trialkyl amine, or combinations thereof.
8. The method of claim 7, wherein the step of mixing comprises
selecting an amine from the group consisting of pyrrolidine,
morpholine, piperidine, N-methyl pyrrolidine, and NR.sup.1R.sup.2X
wherein: R.sup.1, R.sup.2 are selected from the group consisting of
methyl, ethyl, propyl, isopropyl, n-butyl, sec. butyl, pentyl,
hexyl, cyclohexyl, and benzyl; and X is selected from the group
consisting of hydrogen, R.sup.1, and R.sup.2.
9. The method of claim 6, wherein the step of mixing comprises
selecting the tetraalkylammonium hydroxide from the group
consisting of tetraethylammonium hydroxide, tetramethylammonium
hydroxide, tetrapropylammonium hydroxide, and combinations
thereof.
10. The method of claim 1, further comprising the step of
dissolving a solid base in an organic solvent to produce a base
solution with the total organic solvent concentration in the base
solution comprising about 40 to about 95% by volume, the organic
solvent selected from the group consisting of methanol, ethanol,
and combinations thereof.
11. The method of claim 1, wherein the step of providing comprises:
determining the water content of the phase stable, reduced acid
biomass-derived pyrolysis oil; and removing at least a portion of
the water from the biomass-derived pyrolysis oil, the base, or both
the biomass-derived pyrolysis oil and the base.
12. The method of claim 11, further comprising removing additional
water upon phase separation of the reduced acid biomass-derived
pyrolysis oil.
13. A method for producing phase stable, reduced acid
biomass-derived pyrolysis oil from water-containing biomass-derived
pyrolysis oil, the method comprising the steps of: selecting a base
comprising either an inorganic base or a nitrogen-containing base;
removing at least a portion of the water from the water-containing
biomass-derived pyrolysis oil, the base, or both; and adding the
base to the water-containing biomass-derived pyrolysis oil to
produce reduced acid biomass-derived pyrolysis oil.
14. The method of claim 13, wherein the step of selecting a base
comprises selecting the inorganic base from the group consisting of
metal oxides, metal hydroxides, metal alkoxides, metal carbonates
of the alkali and alkaline earth metals, alkali and alkaline earth
exchanged zeolites, mixed metal oxides, and combinations
thereof.
15. The method of claim 14, wherein the step of selecting a base
comprises selecting the metal oxide from the group consisting of
calcium oxide, magnesium oxide, and combinations thereof; the metal
hydroxide from the group consisting of LiOH, NaOH, KOH, RbOH, CsOH,
Mg(OH).sub.2, Ca(OH).sub.2, Sr(OH).sub.2, Ba(OH).sub.2, and
combinations thereof; and the metal alkoxide from the group
consisting of sodium ethoxide, potassium tert-butoxide, and
combinations thereof.
16. The method of claim 13, wherein the step of selecting a base
comprises selecting the nitrogen-containing base comprising an
amine, a tetraalkylammonium hydroxide, or combinations thereof,
wherein the amine is selected from the group consisting of a
dialkyl amine, a trialkyl amine, and combinations thereof,
pyrrolidine, morpholine, piperidine, N-methylpyrrolidine, and
NR.sup.1R.sup.2X wherein: R.sup.1, R.sup.2 are selected from the
group consisting of methyl, ethyl, propyl, isopropyl, n-butyl, sec.
butyl, pentyl, hexyl, cyclohexyl, and benzyl; and X is selected
from the group consisting of hydrogen, R.sup.1, and R.sup.2.
17. The method of claim 13, further comprising removing additional
water from the reduced acid biomass-derived pyrolysis oil upon
phase separation thereof
18. A method for producing phase stable, reduced acid
biomass-derived pyrolysis oil, the method comprising the steps of:
providing water-containing biomass-derived pyrolysis oil; selecting
a base adapted to be added to the water-containing biomass-derived
pyrolysis oil to produce reduced acid biomass-derived pyrolysis
oil; determining a water content of the reduced acid
biomass-derived pyrolysis oil; wherein if the reduced acid
biomass-derived pyrolysis oil is determined to have a water content
greater than about 30 wt %, removing at least a portion of the
water from the water-containing biomass-derived pyrolysis oil, the
base, or both; and adding the selected base to the water-containing
biomass-derived pyrolysis oil.
19. The method of claim 18, wherein the step of selecting a base
comprises selecting a solid base, the method further comprising
dissolving the solid base in an organic solvent.
20. The method of claim 18, further comprising the step of removing
additional water from the reduced acid biomass-derived pyrolysis
oil upon phase separation thereof.
Description
FIELD OF THE INVENTION
[0001] The present invention generally relates to methods for
producing biofuels, and more particularly relates to methods for
producing phase stable, reduced acid biomass-derived pyrolysis
oils.
DESCRIPTION OF RELATED ART
[0002] Fast pyrolysis is a thermal process during which solid
carbonaceous biomass feedstock, i.e., "biomass", such as wood
waste, agricultural waste, etc., is rapidly heated to pyrolysis
temperatures of about 300.degree. C. to about 900.degree. C. in the
absence of air using a pyrolysis reactor. Under these conditions,
solid and gaseous pyrolysis products are formed. A condensable
portion (vapors) of the gaseous pyrolysis products is condensed
into biomass-derived pyrolysis oil.
[0003] Biomass-derived pyrolysis oil can be burned directly as fuel
for certain boiler and furnace applications, and can also serve as
a potential feedstock in the production of biofuels in petroleum
refineries or in stand-alone process units. Biomass-derived
pyrolysis oil has the potential to replace up to 60% of
transportation fuels, thereby reducing the dependency on
conventional petroleum and reducing its environmental impact.
However, biomass-derived pyrolysis oil is a complex, highly
oxygenated organic liquid having properties that currently limit
its utilization as a fuel/biofuel, particularly for diesel
applications. For example, conventional biomass-derived pyrolysis
oil has high acidity (with a low pH and high total acid number
(TAN)) making it corrosive to storage, pipes, and downstream
equipment, with low energy density and susceptibility to increased
viscosity over time. Conventional biomass-derived pyrolysis oil
typically has a pH of <3 and a TAN >150. The high acidity and
low energy density of the biomass-derived pyrolysis oil is
attributable in large part to oxygenated hydrocarbons in the oil,
particularly carboxylic acids such as formic acid, acetic acid,
etc. "Oxygenated hydrocarbons" as used herein are organic compounds
containing hydrogen, carbon, and oxygen. The oxygenated
hydrocarbons in the oil are derived from oxygenated hydrocarbons in
the gaseous pyrolysis products produced during pyrolysis.
[0004] While the direct titration of a base to the biomass-derived
pyrolysis oil reduces its acidity (as measured by an increase in
pH), phase instability of the biomass-derived pyrolysis oil
results. "Phase stability" as used herein means the ability of the
oil to resist changes in chemical composition and maintain
homogeneity. Phase instability results in phase separation,
viscosity increases, and often, solids formation. Such phase
instability reduces utilization of the biomass-derived pyrolysis
oil as a biofuel.
[0005] Accordingly, it is desirable to provide methods for
producing phase stable, reduced acidity biomass derived pyrolysis
oils. It is also desirable to produce phase stable, reduced acid
biomass-derived pyrolysis oils having increased energy density.
Furthermore, other desirable features and characteristics of the
present invention will become apparent from the subsequent detailed
description of the and the appended claims, taken in conjunction
with the accompanying drawings and this background of the
invention.
SUMMARY OF THE INVENTION
[0006] Methods are provided for producing phase stable, reduced
acid biomass-derived pyrolysis oil from biomass-derived pyrolysis
oil. In accordance with one exemplary embodiment, a method for
producing phase stable, reduced acid biomass-derived pyrolysis oil
comprises providing a biomass-derived pyrolysis oil having a
determined water content no greater than about 30% by weight. A
base is mixed with the biomass-derived pyrolysis oil.
[0007] Methods are provided for producing phase stable, reduced
acid biomass-derived pyrolysis oil from water-containing
biomass-derived pyrolysis oil, in accordance with yet another
exemplary embodiment of the present invention. The method comprises
selecting a base comprising either an inorganic base or a
nitrogen-containing base. At least a portion of the water is
removed from the water-containing biomass-derived pyrolysis oil,
the base, or both. The base is added to the water-containing
biomass-derived pyrolysis oil to produce reduced acid
biomass-derived pyrolysis oil.
[0008] Methods are provided for producing phase stable, reduced
acid biomass-derived pyrolysis oil in accordance with yet another
exemplary embodiment of the present invention. The method comprises
providing water-containing biomass-derived pyrolysis oil. A base
adapted to be added to the water-containing biomass-derived
pyrolysis oil to produce reduced acid biomass-derived pyrolysis oil
is selected. The water content of the reduced acid biomass-derived
pyrolysis oil is determined. If the reduced acid biomass-derived
pyrolysis oil is determined to have a water content greater than
about 30 wt %, at least a portion of the water is removed from the
water-containing biomass-derived pyrolysis oil, the base, or both.
The selected base is added to the water-containing biomass-derived
pyrolysis oil.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The present invention will hereinafter be described in
conjunction with the following drawing figures, wherein like
numerals denote like elements, and wherein:
[0010] FIG. 1 is a flow chart of a method for producing phase
stable, reduced acid biomass-derived pyrolysis oils, according to
exemplary embodiments of the present invention.
DETAILED DESCRIPTION
[0011] The following detailed description of the invention is
merely exemplary in nature and is not intended to limit the
invention or the application and uses of the invention.
Furthermore, there is no intention to be bound by any theory
presented in the preceding background of the invention or the
following detailed description of the invention.
[0012] Various exemplary embodiments of the present invention are
directed to a method for producing phase stable, reduced acid
biomass-derived pyrolysis oils. It should be appreciated that while
the oil produced according to exemplary embodiments of the present
invention is generally described herein as a "reduced acid
biomass-derived pyrolysis oil", this term generally includes any
oil produced having a lower acidity than the conventional
biomass-derived pyrolysis oil from which it is derived. As noted
previously, "phase stability" as used herein means the ability of
the oil to resist changes in chemical composition and maintain
homogeneity. Phase instability results in phase separation,
viscosity increases and often, solids formation. In addition, the
phase stable, reduced acid biomass-derived pyrolysis oil has higher
energy density than conventional biomass-derived pyrolysis oil.
"Higher energy density" as used herein means that the phase stable,
reduced acid biomass-derived pyrolysis oil has an increased heat of
combustion as compared to conventional biomass-derived pyrolysis
oil. An increased heat of combustion increases the suitability of
the oil as fuel and biofuel.
[0013] Referring to FIG. 1, a method 10 for producing phase stable,
reduced acid biomass-derived pyrolysis oil begins by providing
conventional biomass-derived pyrolysis oil from a source such as a
feed tank or other source operative to provide such oil (step 100).
Biomass-derived pyrolysis oil is available from, for example, Ensyn
Technologies Inc., of Ontario, Canada. The composition of
biomass-derived pyrolysis oil is somewhat dependent on feedstock
and processing variables. The biomass-derived pyrolysis oil may be
produced, for example, from fast pyrolysis of wood biomass in a
pyrolysis reactor. However, virtually any form of biomass can be
considered for pyrolysis to produce biomass-derived pyrolysis oil.
In addition to wood, biomass-derived pyrolysis oil may be derived
from biomass material such as bark, agricultural wastes/residues,
nuts and seeds, algae, grasses, forestry residues, cellulose and
lignin, or the like. The biomass-derived pyrolysis oil may also be
obtained by different modes of pyrolysis, such as fast pyrolysis,
vacuum pyrolysis, catalytic pyrolysis, and slow pyrolysis (also
known as carbonization) or the like. Biomass-derived pyrolysis oil
typically contains about 20-33% by weight water with a high acidity
(TAN >150). The water content in the starting water-containing
biomass-derived pyrolysis oil may be measured, for example, by Karl
Fischer Reagent Titration Method (ASTM D1364), as known to one
skilled in the art. In this regard, biomass-derived pyrolysis oil
may alternatively be referred to herein as "water-containing
biomass-derived pyrolysis oil."
[0014] Still referring to FIG. 1, method 10 continues by selecting
a base to neutralize the carboxylic acids in the water-containing
biomass-derived pyrolysis oil, thereby reducing the acidity of the
water-containing biomass-derived pyrolysis oil (step 200). As used
herein, "neutralization" is a chemical reaction whereby the acids
in the water-containing biomass-derived pyrolysis oil and the
selected base react to form water and a salt. In an aqueous
solution, solvated hydrogen ions (hydronium ions, H.sub.3O.sup.+)
react with hydroxide ions (OH.sup.-) formed from the base to make
two molecules of water. A salt is also formed. In non-aqueous
reactions, water is not always formed; however, there is always a
donation of protons. Neutralization in accordance with exemplary
embodiments raises the pH and lowers the TAN of water-containing
biomass-derived pyrolysis oil. In one embodiment, the target pH
levels are in the range of about 4.5 to about 4.9. The base may be
in an aqueous solution or a solid base. The selected base is
adapted to be added to the water-containing biomass-derived
pyrolysis oil as hereinafter described.
[0015] The base comprises either an inorganic base or a
nitrogen-containing base. The inorganic bases are strong bases. A
strong base is a basic chemical compound that is able to
deprotonate weak acids in an acid-base reaction. Compounds with a
pK.sub.a of more than about 13 are considered strong bases. Very
strong bases are even able to deprotonate very weakly acidic C--H
groups in the absence of water. Suitable exemplary inorganic bases
include metal oxides, metal alkoxides, metal carbonates of the
alkali and alkaline earth metals, alkali and alkaline earth
exchanged zeolites (e.g., Ca--X zeolite), mixed metal oxides (e.g.,
hydrotalcite), metal hydroxides, and combinations thereof.
Exemplary suitable metal oxides comprise calcium oxide, magnesium
oxide, and combinations thereof. Exemplary suitable metal alkoxides
comprise sodium ethoxide, potassium tert-butoxide, and combinations
thereof. Exemplary suitable metal carbonates comprise potassium
carbonate (K.sub.2CO.sub.3), sodium carbonate (Na.sub.2CO.sub.3),
and calcium carbonate (CaCO.sub.3). Exemplary suitable metal
hydroxides comprise lithium hydroxide (LiOH), sodium hydroxide
(NaOH), potassium hydroxide (KOH), rubidium hydroxide (RbOH),
caesium hydroxide (CsOH), magnesium hydroxide (Mg(OH).sub.2),
calcium hydroxide (Ca(OH).sub.2), strontium hydroxide
(Sr(OH).sub.2), barium hydroxide (Ba(OH).sub.2), and combinations
thereof. The metal hydroxides generate water when neutralizing
carboxylic acids, with the essential reaction being the combination
of hydrogen ions with hydroxyl ions to form water. The maximum
amount of water produced during neutralization with a metal
hydroxide comprises 1 mole eq water to 1 mole eq of neutralized
acid. The exact amount of the water produced depends on the
selected base.
[0016] The nitrogen-containing base can be a tetraalkylammonium
hydroxide, an amine, or combinations thereof. Suitable
tetraalkylammonium hydroxides include tetraethylammonium hydroxide,
tetramethylammonium hydroxide, tetrapropylammonium hydroxide, and
combinations thereof. Amines suitable for use herein include
dialkyl amines, trialkyl amines, or combinations thereof. The amine
may also comprise pyrrolidine, morpholine, piperidine,
N-methylpyrrolidine, and NR.sup.1R.sup.2X wherein R.sup.1 and
R.sup.2 are selected from the group consisting of methyl, ethyl,
propyl, isopropyl, n-butyl, sec. butyl, pentyl, hexyl, cyclohexyl,
and benzyl groups; and X is selected from the group consisting of
hydrogen, R.sup.1, and R.sup.2. Neutralization with non-hydroxyl
bases do not generate water.
[0017] In accordance with an exemplary embodiment, the phase
stable, reduced acid biomass-derived pyrolysis oil has a water
content no greater than about 30 weight percent (wt. %). The terms
"about 30 weight percent" and "about 30% by weight" as used herein
means +/-3 weight percent of 30 weight percent. In this regard,
referring to FIG. 1, prior to adding the selected base to the
water-containing biomass-derived pyrolysis oil, the water content
of the reduced acid biomass-derived pyrolysis oil after the
selected base is added to the water-containing biomass-derived
pyrolysis oil, is determined (the "determined water content") (step
300). If the water content of the reduced acid biomass-derived
pyrolysis oil to be produced is determined to be less than about 30
wt. % (hereinafter, the "threshold value"), the selected base is
added to the water-containing biomass-derived pyrolysis oil to
produce reduced acid biomass-derived pyrolysis oil. However, if the
water content of the reduced acid biomass-derived pyrolysis oil to
be produced is determined to be greater than about 30 wt. %, at
least a portion of the water is removed from the water-containing
biomass-derived pyrolysis oil, the base, or both.
[0018] The water content is determined by the following equation
(I) (which takes into account the water in the water-containing
biomass-derived pyrolysis oil and the water associated with the
base (water in the base and the water produced during
neutralization)):
x=((a*b)+(f*d)+g)/(a+f) (I)
wherein:
[0019] x=the concentration of water in the phase stable, reduced
acid biomass-derived pyrolysis oil expressed as g H.sub.2O/g
oil;
[0020] a=the amount of the starting water-containing
biomass-derived pyrolysis oil to be treated in grams;
[0021] b=the concentration of water in the starting
water-containing biomass-derived pyrolysis oil expressed as g
H.sub.2O/g starting oil (as determined by Karl Fischer Reagent
Titration Method (ASTM D1364), as noted previously);
[0022] c=the concentration of carboxylic acids in the starting
water-containing biomass-derived pyrolysis oil expressed as mol
acid/gram oil (determined by the method as hereinafter
described);
[0023] d=the concentration of free water in the neutralizing base
in gH.sub.2O/gram of base (as determined, for example, by Karl
Fischer Reagent Titration Method (ASTM D1364);
[0024] e=the concentration of neutralizing base in mol base/gram as
provided by the manufacturer or determined using methods known by
those skilled in the art (i.e., dilution of a more concentrated
base solution and/or titration against a standard acid); and
[0025] f=the amount of base needed to neutralize the
water-containing biomass-derived pyrolysis oil acidity in
grams=(a*c)/e.
[0026] g=amount of water in grams produced by neutralization of the
pyrolysis oil acids. This is dependent on the nature of the
neutralizing base such that for:
Hydroxide bases (sodium hydroxide, tetraethylammonium hydroxide):
g=a*c*18.0 Oxide and carbonate bases (Calcium oxide, sodium
carbonate: g=(a*c*18.0)/2 Amine and alkoxide bases (triethylamine,
sodium ethoxide): g=0
[0027] The concentration of carboxylic acids in the starting
water-containing biomass-derived pyrolysis oil ("c" in equation (I)
above), is determined by the following method adapted from Dence,
C. W., Determination of carboxyl groups [in lignin], Methods Lignin
Chem. (1992), p. 458-464: A solution of 0.05N tetra-n-butylammonium
hydroxide solution (TnBAH) is prepared by diluting 50.0 milliliters
(mL) of 1.0N TnBAH (Aldrich, SAP#1014519, 100 mL) solution to 1.00
liters (L) in isopropanol. The solution is mixed thoroughly before
transferring the solution to a Dosimat bottle. 1 mL of concentrated
HCl is added to 100 mL of deionized water and mixed thoroughly. 4
mL of this solution is added to about 140 mL of DMF
(N,N-dimethylformamide) (available from, for example, Burdick &
Jackson of Muskegon, Mich. (USA)) for titration of samples. To
standardize the titrant, 0.15-0.20 g of dried benzoic acid is
weighed into a titration beaker and the weight recorded to the
nearest 0.1 mg. 120 mL of the DMF solution is added to the benzoic
acid and titrated with the TnBAH solution. The standardization
should be done in duplicate. The Normality is calculated to three
significant figures and the standardization repeated every three
hours.
N = g Benzoic Acid ( mL titrant ) ( 0.12212 ) ##EQU00001##
To titrate the samples, and prior to the first sample analysis,
0.05-0.08 g of p-hydroxybenzoic acid is weighed into a titration
beaker. The DMF/HCl solution is added to the p-hydroxybenzoic acid.
The resultant solution is titrated through the 3.sup.rd inflection.
This is the blank used to calculate the HCl correction, and can be
used as a QC for the phenolic hydroxyl titrations. Next, 0.3-0.4 g
of lignin and 0.05-0.08 g of p-hydroxybenzoic acid are weighed into
a titration beaker. The DMF/HCl solution is added to the titration
beaker. The titration beaker is blanketed with nitrogen and stirred
for 5 minutes before titration. The solution is titrated with 0.05N
TnBAH to the 3.sup.rd inflection. The theoretical titer of the
internal standard used in the blank or sample titration is
calculated according to the following equation:
a ( mL ) = g pHBA 0.13812 ( N ) ##EQU00002##
To calculate the HCl interference from the blank,
c (mL)=[(measured volume to reach 2.sup.nd inflection of
blank)-(measured 1.sup.st inflection)]-(a (mL, calculated
above))
then,
mEq carboxyl / g sample = [ ( y ) - ( x ) - ( c ) - ( a ) ] N w
##EQU00003## mEq phenolic hydroxyls / g sample = [ ( z ) - ( y ) -
( a ) ] N w ##EQU00003.2##
wherein: x=mL at first inflection point y=mL at second inflection
point z=mL at third inflection point
[0028] As noted above, if the water content of the reduced acid
biomass-derived pyrolysis oil to be produced is determined to be
less than about 30 weight percent, the selected base is added to
the water-containing biomass-derived pyrolysis oil to produce
reduced acid biomass-derived pyrolysis oil (step 400). The amount
of the selected base (f in equation (I) above and equation (II)
below) to be added to the water-containing biomass-derived
pyrolysis oil to neutralize the starting carboxylic acid content is
determined according to the following equation (II):
f=(a*c)/e (II)
wherein, as noted previously:
[0029] a=the amount of the starting water-containing
biomass-derived pyrolysis oil to be treated in grams;
[0030] c=the concentration of carboxylic acids in the starting
water-containing biomass-derived pyrolysis oil expressed as mol
acid/gram oil (as determined above); and
[0031] e=the concentration of neutralizing base in mol base/gram as
provided by the manufacturer or determined using methods known by
those skilled in the art (i.e., dilution of a more concentrated
base solution and/or titration against a standard acid).
[0032] As neutralization reactions are often exothermic, the base
is added at an effective rate to maintain the temperature of the
mixture at less than about 40.degree. C. The base is added at a
temperature from about 20.degree. C. to about 40.degree. C. A solid
base may be dissolved in an organic solvent (thereby producing a
base solution) prior to addition of the base to the
water-containing biomass-derived pyrolysis oil. Suitable exemplary
organic solvents comprise methanol, ethanol, and combinations
thereof. The addition of the solvent (about 40% to about 95% by
volume) allows the base to be added gradually in a controlled
manner, without raising the water content of the resultant phase
stable, reduced acid biomass-derived pyrolysis oil above the
threshold value. In addition, the solvent raises the solubility of
the components in the mixture. Less solvent is needed when the
water produced in the titration (during neutralization) does not
exceed the solubility level of the biomass-derived pyrolysis oil.
If an excess of base is added, a precipitate may form that may be
removed by filtration.
[0033] If the water content of the reduced acid biomass-derived
pyrolysis oil to be produced ("x" in equation (I) above) is
determined to be greater than about 30 weight percent, at least a
portion of the water is removed from the water-containing
biomass-derived pyrolysis oil, the base, or both (step 500) prior
to addition of the selected base as described above (step 400).
Water may be removed from the water-containing biomass-derived
pyrolysis oil, the base, or both by methods known to one skilled in
the art, for example, distillation, evaporation, or the like. It is
to be understood that a base may be selected specifically because
it does not generate water during the neutralization reaction, for
example, the non-hydroxide bases and the nitrogen-containing bases,
and therefore little or no water may have to be removed to produce
the reduced acid biomass-derived pyrolysis oil with a water content
below the threshold value, i.e., a phase stable, reduced acid
biomass-derived pyrolysis oil. Similarly, if the water-containing
biomass-derived pyrolysis oil has a water content below the
threshold value and the selected base does not generate water
during neutralization, the removal of water from the reduced acid
biomass-derived pyrolysis oil is unnecessary to produce a phase
stable, reduced acid biomass-derived pyrolysis oil because the
water content thereof has been maintained below the threshold
value.
[0034] Referring again to FIG. 1, the reduced acid biomass-derived
pyrolysis oil may be inspected (step 600) to verify that there is
no phase separation. Phase separation typically occurs, if at all,
within 48 hours after the base is added to the water-containing
biomass-derived pyrolysis oil. If phase separation occurs,
additional water may be removed from the reduced acid
biomass-derived pyrolysis oil (step 700) by methods known to one
skilled in the art, for example distillation and evaporation, until
no phase separation is observed on inspection.
[0035] From the foregoing, it is to be appreciated that the phase
stable, reduced acid biomass-derived pyrolysis oil having a water
content no greater than about 30 wt % is substantially homogenous,
with an acidity (as measured by pH) reduced from that of
conventional biomass-derived pyrolysis oil. In addition, the energy
density of the phase stable, reduced acid biomass-derived pyrolysis
oil is higher than that of conventional biomass-derived pyrolysis
oil. The increased pH, phase homogeneity, and higher energy density
of the phase stable, reduced acid biomass-derived pyrolysis oil
produced in accordance with exemplary embodiments as described
herein improve its suitability as a fuel and biofuel.
[0036] While at least one exemplary embodiment has been presented
in the foregoing detailed description of the invention, it should
be appreciated that a vast number of variations exist. It should
also be appreciated that the exemplary embodiment or exemplary
embodiments are only examples, and are not intended to limit the
scope, applicability, or configuration of the invention in any way.
Rather, the foregoing detailed description will provide those
skilled in the art with a convenient road map for implementing an
exemplary embodiment of the invention, it being understood that
various changes may be made in the function and arrangement of
elements described in an exemplary embodiment without departing
from the scope of the invention as set forth in the appended claims
and their legal equivalents.
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