U.S. patent application number 12/227804 was filed with the patent office on 2009-07-02 for microreactor process for making biodiesel.
Invention is credited to Ahmad Al-Dhubabian, Goran Nadezda Jovanovic, James Parker, Brian Kevin Paul.
Application Number | 20090165366 12/227804 |
Document ID | / |
Family ID | 38802019 |
Filed Date | 2009-07-02 |
United States Patent
Application |
20090165366 |
Kind Code |
A1 |
Jovanovic; Goran Nadezda ;
et al. |
July 2, 2009 |
Microreactor Process for Making Biodiesel
Abstract
Embodiments of a method for using a microreactor to produce
biodiesel. For example, the method may comprise flowing a first
fluid comprising an alcohol and a second fluid comprising an oil to
the microreactor. Alcohols typically, but not necessarily, are
lower aliphatic alcohols, including methanol, ethanol, amyl alcohol
or combinations thereof. Biodiesel production can be under
supercritical conditions, where such conditions typically are
determined relative to the alcohol component. Suitable sources of
oil products include soy, inedible tallow and grease, corn, edible
tallow and lard, cotton, rapeseed, sunflower, canola, peanut,
safflower, and combinations thereof. Catalysts can be used to
facilitate biodiesel production, such as metal oxides, metal
hydroxides, metal carbonates, alcoholic metal carbonates,
alkoxides, mineral acids and enzymes. Oil conversion to biodiesel
typically increases with increasing mean microreactor residence
time. Certain embodiments of the present invention can include
blending biodiesel produced by the method with petroleum-based
products.
Inventors: |
Jovanovic; Goran Nadezda;
(Corvallis, OR) ; Paul; Brian Kevin; (Corvallis,
OR) ; Parker; James; (Corvallis, OR) ;
Al-Dhubabian; Ahmad; (Jeddah, SA) |
Correspondence
Address: |
KLARQUIST SPARKMAN, LLP
121 SW SALMON STREET, SUITE 1600
PORTLAND
OR
97204
US
|
Family ID: |
38802019 |
Appl. No.: |
12/227804 |
Filed: |
May 30, 2007 |
PCT Filed: |
May 30, 2007 |
PCT NO: |
PCT/US07/12763 |
371 Date: |
November 26, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60810569 |
Jun 1, 2006 |
|
|
|
Current U.S.
Class: |
44/308 ;
44/388 |
Current CPC
Class: |
C10G 2300/1011 20130101;
B01J 2219/00959 20130101; Y02E 50/10 20130101; Y02P 30/20 20151101;
B01J 2219/00837 20130101; B01J 2219/00891 20130101; B01J 2219/00984
20130101; C11C 3/003 20130101; Y02E 50/13 20130101; B01J 2219/00905
20130101; B01J 2219/00835 20130101; C10L 1/19 20130101; C10L 1/026
20130101; B01J 2219/00907 20130101; B01J 2219/00783 20130101; B01J
2219/00788 20130101; B01J 2219/00844 20130101; B01J 2219/0086
20130101; B01J 19/0093 20130101 |
Class at
Publication: |
44/308 ;
44/388 |
International
Class: |
C10L 1/19 20060101
C10L001/19 |
Claims
1. A method for producing biodiesel, comprising: providing a
microreactor; flowing a first fluid comprising an alcohol and a
second fluid comprising an oil to the microreactor; and using the
microreactor to produce biodiesel.
2-5. (canceled)
6. The method according to claim 1 where the alcohol is methanol,
ethanol, propanol, butanol, amyl alcohol or combinations
thereof.
7. (canceled)
8. The method according to claim 1 where the oil is derived from
soy, inedible tallow and grease, corn, edible tallow and lard,
cotton, rapeseed, sunflower, canola, peanut, safflower, and
combinations thereof.
9. The method according to claim 1 further comprising using a
catalyst to produce the biodiesel, where the catalyst is a metal
oxide, metal hydroxide, metal carbonate, alcoholic metal oxide,
alcoholic metal hydroxide, alcoholic metal carbonate, an alkoxide,
a mineral acid, an enzyme, or combinations thereof.
10-11. (canceled)
12. The method according to claim 9 where the catalyst is sodium
hydroxide, potassium hydroxide, sodium alkoxide, potassium
alkoxide, or combinations thereof.
13-14. (canceled)
15. The method according to claim 1 further comprising blending
biodiesel produced by the method in an amount greater than zero
weight percent petroleum product to less than 100 weight percent
with petroleum-based products.
16. (canceled)
17. The method according to claim 1 comprising a
transesterification process.
18. The method according to claim 1 performed at supercritical
conditions.
19. The method according to claim 18 where the alcohol is
supercritical.
20. The method according to claim 1 where the oil is a triglyceride
having a formula ##STR00009## where R.sub.1, R.sub.2 and R.sub.3
independently are fatty acids.
21. The method according to claim 20 where the fatty acids have
carbon chain lengths ranging from at least as few as 10 carbon
atoms to at least as many as 20 carbon atoms.
22. (canceled)
23. The method according to claim 20 where the fatty acids are
selected from lauric acid, palmitic acid, stearic acid, oleic acid,
linoleic acid and linolenic acid.
24. The method according to claim 20 where the fatty acid includes
at least one site of unsaturation other than a carbon-carbon double
bond.
25. The method according to claim 1 further comprising providing at
least a 3:1 molar ratio of alcohol-to-triglycerides.
26. The method according to claim 1 where a temperature at which a
transesterification reaction is conducted is within a range of from
about 25.degree. C. to less than about 350.degree. C.
27. (canceled)
28. The method according to claim 1 further comprising providing
plural microreactors.
29. The method according to claim 1 where oil and alcohol fluid
layers have fluid layer thicknesses in the microreactor of from
about 10 .mu.m to about 500 .mu.m.
30. The method according to claim 1 where surface-to-volume ratio
of microreactor microchannels is from about 10,000 m.sup.2/m.sup.3
to about 50,000 m.sup.2/m.sup.3.
31. (canceled)
32. The method according to claim 1 where the microreactor includes
at least one manifold for distributing fluid flow to individual
microchannels.
33. (canceled)
34. The method according to claim 1 where the oil is soybean oil,
the alcohol is methanol or ethanol, and the method further
comprises using a metal hydroxide catalyst.
35. The method according to claim 34 where metal hydroxide catalyst
is used in an amount of about 1.0 weight % of the soybean oil used
for transesterification.
36. The method according to claim 1 where oil and alcohol fluids
are pumped to the microreactor using a pump volume flow rate ratio
of oil:alcohol of about 3.4.
37. The method according to claim 1 where oil and alcohol fluids
are used at a molar ratio of oil-to-alcohol of about 1:7.2.
38. The method according to claim 1 further comprising separating
two phases produced by the reaction using a distillation process, a
centrifugation process, or combinations thereof.
39-40. (canceled)
41. The method according to claim 1 comprising using a microreactor
microchannel having a 100 .mu.m thickness, soybean oil, and a
transesterification processing temperature at or about ambient, and
where conversion of soybean oil to biodiesel ranges from about 12%
at about 0.4 MRT to about 91% at 10 minutes MRT.
42. The method according to claim 1 comprising using a microreactor
microchannel having a 100 .mu.m thickness, soybean oil, and a
transesterification processing temperature at or about ambient, and
where total methyl ester concentration ranges from about 0.3 mol/l
at about 0.4 minute MRT to about 2.5 moles/l at about 10 minutes
MRT.
43. The method according to claim 1 comprising using a microreactor
microchannel having a 200 .mu.m thickness, soybean oil, and a
transesterification processing temperature at or about ambient.
44. The method according to claim 43 where conversion of soybean
oil to biodiesel ranges from about 4% at about an 0.4 MRT to about
86% at about 10 minutes MRT.
45-64. (canceled)
65. A method for producing biodiesel comprising: providing a
microreactor; flowing a first fluid to the microreactor comprising
a lower aliphatic alcohol; flowing a second fluid comprising an oil
to the microreactor, the oil comprising a triglyceride having a
formula ##STR00010## where R.sub.1, R2 and R.sub.3 independently
are fatty acids having hydrocarbon chain lengths ranging from at
least as few as 10 carbon atoms to at least as many as 20 carbon
atoms; providing a reaction catalyst selected from the group
consisting of metal oxides, metal hydroxides, metal carbonates,
alcoholic metal oxides, alcoholic metal hydroxides, alcoholic metal
carbonates, alkoxides, mineral acids, enzymes, or combinations
thereof; using the microreactor to produce biodiesel; and blending
biodiesel produced by the method with petroleum-based products in
an amount greater than zero weight percent petroleum product to
less than 100 weight percent petroleum product.
66. The method according to claim 65 performed at supercritical
conditions.
67. The method according to claim 65 where the alcohol is
supercritical.
68. The method according to claim 65 further comprising providing
plural microreactors.
69. The method according to claim 65 further comprising using a
cosolvent.
70. The method according to claim 69 where the cosolvent is carbon
dioxide.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/810,569, filed on Jun. 1, 2006. The entire
disclosure of the provisional application is considered to be part
of the disclosure of the following application and is hereby
incorporated by reference.
FIELD
[0002] The present disclosure concerns embodiments of a process for
making biodiesel, particularly a process that utilizes at least one
microreactor device.
BACKGROUND
A. Biodiesel Generally
[0003] Biodiesel is registered with the U.S. Environmental
Protection Agency as a pure fuel or as a fuel additive, is a legal
fuel for commerce, and meets clean diesel standards established by
the California Air Resources. Its physical and chemical properties
as they relate to operation of diesel engines are similar to
petroleum-based diesel fuel as per the ASTM fuel tests shown in
Table 1.
TABLE-US-00001 TABLE 1 ASTM Fuel Tests on # 2 Diesel Fuel and
Methyl Soyate ASTM # 2 Ref Methyl Soyate Test Property Method no.
Diesel fuel (Biodiesel) Viscosity @ 40.degree. C. (cSt) D-445 2.39
4.08 Specific gravity @ 15.6.degree. C. -- 0.847 0.884 Higher
heating value (MJ/KG) D-240 45.2 39.8 Cetane no. D-613 45.8 46.2
Distillation 90% .degree. C. D-86 296 342 Pour point (.degree. C.)
D-97 -23 -1 Cloud point (.degree. C.) D-2500 -19 2 Flash point
(.degree. C.) D-93 78 141 Sulfur (% mass) D-129 0.25 0.01 Corrosion
D-130 1-a 1-a Ash (% mass) D-482 0.025 <0.01 Color (ASTM color
code) D-1500 L2.0 L2.0
Biodiesel can be used most effectively as a supplement for other
energy liquid fuels such as diesel fuel. It is biodegradable and
non-toxic, has low pollutant emission and therefore is
environmentally beneficial.
[0004] Biodiesel has been considered as a fuel or fuel additive
since the late 1970's. The oil embargo by the Organization of
Petroleum Exporting Countries of 1973 resulted in significant
biodiesel research by various universities, government agencies,
and research organizations. The general conclusion is that
biodiesel is a technically acceptable substitute, replacement, or
blending stock for conventional petroleum diesel. It can be used at
a 100-percent level (B100) or mixed with diesel in any proportion.
The most common mixtures are B2 containing 2 percent biodiesel and
B20 containing 20 percent biodiesel.
[0005] In 1999, only one million gallons of biodiesel were
produced. In 2002, 25 million gallons of biodiesel were produced.
Furthermore, biodiesel is the renewable fuel of choice in the
European Union. Nearly 40 percent of the cars in Europe have diesel
engines. Some cars are even fueled by B100, pure biodiesel. Germany
uses the most biodiesel: 200 million gallons in 1991; 500 million
gallons in 2001; and an estimated 750 million gallons in 2002. Most
of Germany's biodiesel is made from rapeseed oil.
[0006] In 2000, biodiesel become the only alternative fuel to have
successfully completed the EPA-required Tier I and Tier II healthy
effects testing under the clean air act. These independent tests
conclusively demonstrated biodiesel's significant reduction of
virtually all regulated emissions and showed that biodiesel does
not pose a threat to human health. Biodiesel contains no sulfur or
aromatics, and using biodiesel in a conventional diesel engine
substantially reduces unburned hydrocarbons, carbon monoxide and
particulate matter. The EPA has surveyed biodiesel emissions
studies and compared them with the testing results obtained in
major studies of conventional fuels. The results are shown in Table
2.
TABLE-US-00002 TABLE 2 Average Biodiesel Emissions Compared to
Conventional Diesel, According To EPA (Source, National Biodiesel
Board) Emission Type B100 B20 Regulated Type Total Unburned
Hydrocarbons -67% -20% Carbon Monoxide -48% -12% Particulate Matter
-47% -12% No.sub.x +10% +2% Non-Regulated Sulfates -100% -20%* PAH
(Polycyclic Aromatic Hydrocarbons)** -80% -13% nPAH (nitrated
PAH's)** -90% -50%*** Ozone potential of speciated HC -50% -10%
*Estimated from B100 result **Average reduction across all
compounds measured ***2-nitroflourine results were within test
method variability
[0007] In 2000, the EPA released its new diesel regulations, which
require over 90% reductions in both NO.sub.x and particulate matter
emissions from diesel engines beginning in the year 2007.
After-treatment technologies (largely NO.sub.x catalysts,
particulate traps with catalysts, and exhaust gas re-circulation)
dramatically reduce diesel emissions only if the sulfur level in
the fuel is significantly reduced. The EPA has mandated that the
sulfur level in on-road diesel fuel be reduced from the current 500
ppm maximum to 15 ppm maximum (97% reduction) beginning in 2006.
However, the increased removal of sulfur from diesel fuel has the
unintended consequence of removing other components responsible for
the fuel's lubricity. Decreased fuel lubricity results in increased
engine wear, repair expense, and idle-time. Lubricity additives
will have to be added to this new ultra-low sulfur diesel fuel to
provide satisfactory protection for engines and high-pressure fuel
injection equipment. Using biodiesel as a blending stock may help
refineries meet future sulfur specifications. Biodiesel also has
excellent lubricity characteristics and improves lubricity, even
with a blend as low as 2% in conventional diesel fuel.
B. Biodiesel Production Methods
[0008] Biodiesel has been produced in different ways, including
microemulsification, pyrolysis and transesterification.
Microemulsification (forming a colloidal equilibrium dispersion of
optically isotropic fluid microstructure with dimensions generally
in the 1-150 nm range) reduces the high viscosity of vegetable oils
by mixing them with solvents, such as methanol, ethanol and ionic
or nonionic amphiphiles. Microemulsions form spontaneously from two
normally immiscible liquids. Short term performances of both ionic
and nonionic microemulsions of aqueous ethanol in soybean oil were
found to be similar to # 2 diesel fuel, in spite of the lower
cetane number and energy content. In longer term testing (200
hours), no significant deteriorations in performance were
observed.
[0009] Pyrolysis converts one substance into another using heat, or
heat and a catalyst, typically in the absence of air or oxygen.
SiO.sub.2 and Al.sub.2O.sub.3 are typical pyrolysis catalysts.
Animal fats can be pyrolyzed to produce many smaller chain
compounds, and fat pyrolysis has been investigated for over a
hundred years, especially in regions that lack petroleum deposits.
Thermal decomposition of triglycerides produces compounds of
several classes, including alkanes, alkenes, alkadienes, carboxylic
acids, aromatics and small amounts of gaseous products. Pyrolyzed
oils are unacceptable in terms of ash content, carbon residues, and
pour point. Additionally, oxygen removal during thermal processing
eliminates any environmental benefits of using an oxygenated
fuel.
[0010] Transesterification (also called alcoholysis) is the
reaction of a fat or oil with an alcohol to form esters and
glycerol. The physical properties of chemicals related to the
transesterification reaction are summarized in Table 3.
TABLE-US-00003 TABLE 3 Physical Properties of Chemicals Related to
Transesterification Sp. gr., g/milliliter Melting point Boiling
Solubility Name (.degree. C.) (.degree. C.) point (.degree. C.)
(>10%) Methyl 0.875 (75) 18.8 -- -- Myristate Methyl 0.825 (75)
30.6 196.0 Acids, benzene, Palmitate EtOH, Et.sub.2O Methyl 0.850
38.0 215.0 Et.sub.2O, chloroform Stearate Methyl 0.875 -19.8 190.0
Et OH, Et.sub.2O Oleate Methanol 0.792 -97.0 64.7 H.sub.2O, ether,
EtOH Ethanol 0.789 -112.0 78.4 H.sub.2O, ether Glycerol 1.26 17.9
290.0 H.sub.2O, EtOH
[0011] Biodiesel also has been produced using supercritical
methanol [350.degree. C. and 45 MPa] to produce methyl esters
(biodiesel) by transesterification without using any catalyst. A
study of rapeseed oil transesterification in supercritical methanol
found that transesterification proceeds very effectively and
produces the same methyl esters as those obtained in the
conventional method using an alkali catalyst. Furthermore, the
methyl ester yield in the supercritical methanol reaction is higher
because the free fatty acids contained in crude oils and fat also
are efficiently converted to methyl esters. According to kinetic
analyses of the reactions in supercritical methanol, a reaction
temperature of 350.degree. C. and a methanol-to-rapeseed oil molar
ratio of 42:1 produced the best reaction conditions. Increasing the
reaction temperature increased ester conversion, but thermal
degradation of hydrocarbons occurred at a temperature above
400.degree. C.
SUMMARY
[0012] Embodiments of a method for producing biodiesel are
disclosed. One embodiment of the method comprise providing a
microreactor, and then using the microreactor to produce biodiesel.
Reactants suitable for producing biodiesel are flowed to the
microreactor. For example, the method may comprise flowing a first
fluid comprising an alcohol and a second fluid comprising an oil to
the microreactor. A person of ordinary skill in the art also will
appreciate that other process steps, such as purification of
products produced, can be accomplished "on chip" using a
microseparator, for example, or "off chip," such as by using
conventional purification techniques, such as precipitation,
crystallization, distillation, chromatography, etc., and any and
all combinations of such techniques.
[0013] Alcohols useful for producing biodiesel typically, but not
necessarily, are lower aliphatic alcohols, such as alcohols having
10 or fewer total carbon atoms and including alkyl, alkenyl or
alkynyl alcohols. Specific examples of suitable alcohols include
methanol, ethanol, propanol, butanol, amyl alcohol or combinations
thereof. Suitable sources of oil products include soy, inedible
tallow and grease, corn, edible tallow and lard, cotton, rapeseed,
sunflower, canola, peanut, safflower, and combinations thereof.
[0014] Catalysts can be used to facilitate biodiesel production.
Examples of suitable catalysts include metals, such as Pt, Pd, Ag,
Ni, Zn, Fe etc., metal oxides, such as FeO, Fe.sub.2O.sub.3,
Fe.sub.3O.sub.4, NiO, ZnO, SnO etc., metal hydroxides, metal
carbonates, alcoholic metal oxides, alcoholic metal hydroxides,
alcoholic metal carbonates, alkoxides, mineral acids and enzymes.
Any and all combinations of such catalysts also can be used.
Working embodiments typically used Group I metal hydroxides or
alkoxides as catalysts, such as sodium or potassium hydroxides or
alkoxides.
[0015] The conditions used to produce biodiesel can vary. For
example, pressure and temperature both can be substantially ambient
conditions, or can be elevated. For example, the temperature useful
for producing biodiesel according to disclosed embodiments
typically varies from about ambient (e.g. about 25.degree. C.) to
about the degradation temperature of either reactants or products,
which typically is less than about 350.degree. C., more typically
less than about 250.degree. C. Likewise pressure can be
substantially ambient, or can be substantially greater than
ambient. Particular working embodiments for producing biodiesel
also can be conducted at supercritical conditions, typically
supercritical conditions relative to any alcohol component used.
These conditions will vary, as will be understood by a person of
ordinary skill in the art, based on the reactants used. Relative
reactant amounts also can be varied, but reactants typically were
used in at least a 3:1 molar ratio of alcohol-to-oil, and more
typically a larger excess of alcohol.
[0016] The method may result in forming two phases. Thus, the
method can include separating two phases produced by the reaction,
such as by using a distillation process, a centrifugation process,
or combinations thereof.
[0017] Working embodiments for making biodiesel typically involved
a transesterification process using an alcohol and a triglyceride
having a formula
##STR00001##
where R.sub.1, R.sub.2 and R.sub.3 independently are fatty acids.
Suitable fatty acids typically have carbon chain lengths ranging
from at least as few as 10 carbon atoms to at least as many as 20
carbon atoms, and more typically chain lengths range from about 12
carbon atoms to about 18 carbon atoms. Examples of particular fatty
acids include, without limitation, lauric acid, palmitic acid,
stearic acid, oleic acid, linoleic acid and linolenic acid. These
fatty acids can be saturated or unsaturated, and can include at
least one site of unsaturation other than a carbon-carbon double
bond.
[0018] An important feature of the present invention is using
microreactors for the production of biodiesel. Various microreactor
structures are suitable for making biodiesel according to the
present invention, and the structures described herein are
exemplary. For example, microreactors can be used that vary the oil
and alcohol fluid layer thicknesses, such as thicknesses that range
from about 10 .mu.m to about 500 .mu.m. Likewise, microreactors
having microchannels with variable surface-to-volume ratios can be
used, such as microchannels having surface-to-volume ratios that
range from about 10,000 m.sup.2/m.sup.3 to about 50,000
m.sup.2/m.sup.3. Microreactors having a single microchannel might
be used to make biodiesel, but increasing output may require using
(1) devices having plural microchannels, (2) plural microreactors,
or (3) both. Typical working embodiments of microreactors had
plural laminae with at least one lamina defining at least one
microchannel for receiving fluid. Microreactors useful for
producing biodiesel also can include a manifold, or manifolds, for
distributing fluid flow to individual microchannels. Commercial
implementations of the disclosed method likely will use plural
microreactors to provide suitable quantities of biodiesel.
[0019] Biodiesel can be blended with other materials. As a result,
certain embodiments of the present invention include blending
biodiesel produced by the method with petroleum-based products. For
example, the biodiesel produced by the method can be blended with
greater than zero weight percent petroleum product to less than 100
weight percent petroleum product.
[0020] A particular embodiment of the disclosed method for
producing biodiesel comprises first providing a microreactor. A
first fluid comprising a lower aliphatic alcohol is flowed to the
microreactor, as is a second fluid comprising a triglyceride having
a formula
##STR00002##
where R.sub.1, R.sub.2 and R.sub.3 independently are fatty acids. A
reaction catalyst is then provided, such as an alcoholic solution
comprising a reaction catalyst selected from the group consisting
of metal oxides, metal hydroxides, metal carbonates, alcoholic
metal oxides, alcoholic metal hydroxides, alcoholic metal
carbonates, alkoxides, mineral acids, enzymes, or combinations
thereof. The microreactor is then used to produce biodiesel, which
is blended with petroleum-based products in an amount greater than
zero weight percent petroleum product to less than 100 weight
percent petroleum product.
[0021] A person of ordinary skill in the art will appreciate that
reactants and reaction conditions suitable for making biodiesel are
variable. For example, working embodiments include using soybean
oil, methanol or ethanol, and the method further comprises using a
metal hydroxide catalyst, such as a metal hydroxide catalyst used
in an amount of about 1.0 weight % of the soybean oil used for the
transesterification reaction. Oil and alcohol fluids have been
pumped to the microreactor using a pump volume flow rate ratio of
oil:alcohol of about 3.4, which resulted in a molar ratio of
oil-to-alcohol of about 1:7.2.
[0022] Oil conversion to biodiesel typically increases with
increasing mean microreactor residence time. So, for working
embodiments that used a microchannel having a 100 .mu.m thickness,
soybean oil, and a transesterification processing temperature of
about 25.degree. C., conversion of soybean oil to biodiesel ranged
from about 12% at about 0.4 MRT to about 91% at 10 minutes MRT, and
total methyl ester concentration ranged from about 0.3 mole/l at
about 0.4 minute MRT to about 2.5 moles/l at about 10 minutes MRT.
For working embodiments using a microchannel having a 200 .mu.m
thickness, soybean oil, and a transesterification processing
temperature of about 25.degree. C., conversion of soybean oil to
biodiesel ranged from about 4% at about an 0.4 MRT to about 86% at
about 10 minutes MRT, and total methyl ester concentration ranged
from about 0.1 mole/l at about 0.43 minute MRT to about 2.4 moles/l
at about 10.6 minutes MRT.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a schematic diagram of one embodiment of a
microreactor used to produce biodiesel according to the present
invention.
[0024] FIG. 2 is an exploded schematic view of a microreactor used
in working embodiments of a process for making biodiesel.
[0025] FIG. 3 is a digital image showing a plate patterned to
define microchannels and apertures for receiving fluid flow.
[0026] FIG. 4 is a digital image showing plural plates of FIG. 3
positioned adjacent end plates used to construct a working
embodiment of the present invention.
[0027] FIG. 5 is a schematic perspective drawing illustrating
positioning plural plates defining microchannels to collectively
define one embodiment of a microreactor for producing
biodiesel.
[0028] FIG. 6 is digital image of a working embodiment of a system
comprising a microreactor useful for making biodiesel according to
the present invention.
[0029] FIG. 7 is a digital image of one embodiment of a
disassembled microreactor useful for making biodiesel according to
the present invention adjacent a penny for size comparison.
[0030] FIG. 8 is a digital image providing a front perspective view
of one embodiment of a microreactor useful for making biodiesel
according to the present invention adjacent a penny for size
comparison.
[0031] FIG. 9 is a digital image providing a perspective view of
one embodiment of an end plate, adjacent a penny for size
comparison, used in one embodiment of a microreactor useful for
making biodiesel according to the present invention.
[0032] FIG. 10 is a digital image providing a side perspective view
of one embodiment of a microreactor useful for making biodiesel
according to the present invention adjacent a penny for size
comparison.
[0033] FIG. 11 is a digital image providing a top perspective view
of dual syringe pump used with one embodiment of a microreactor
useful for making biodiesel according to the present invention.
[0034] FIG. 12 is a schematic diagram illustrating methanol and
soybean oil flow through a microchannel.
[0035] FIG. 13 is a cross sectional schematic drawing illustrating
a microchannel without a catalyst and a microchannel having
catalyst disposed therein.
[0036] FIG. 14 is a schematic cross sectional drawing illustrating
a microchannel having two fluids flowing therethrough.
[0037] FIG. 15 is a graph of fluid layer thickness (m) versus
velocity (m/s) comparing fluid flow velocities of methanol and
soybean oil in a microchannel.
[0038] FIG. 16 is a graph of soybean oil conversion (%) versus mean
microchannel residence time (minutes) using a microreactor having a
100 .mu.m microchannel thickness.
[0039] FIG. 17 is a graph of ester concentration (mol/l) versus
mean microchannel residence time (minutes) using a microreactor
having a 100 .mu.m microchannel thickness.
[0040] FIG. 18 is a graph of methyl ester concentration (mole/l)
versus mean microchannel residence time (minutes) using a
microreactor having a 100 .mu.m microchannel thickness.
[0041] FIG. 19 is a graph of soybean oil conversion (%) versus mean
microchannel residence time (minutes) using a microreactor having a
200 .mu.m microchannel thickness.
[0042] FIG. 20 is a graph of methyl ester concentration (mole/l)
versus mean microchannel residence time (minutes) using a
microreactor having a 200 .mu.m microchannel thickness.
[0043] FIG. 21 is a graph of methyl ester concentration (mol/l)
versus mean microchannel residence time (minutes) using a
microreactor having a 200 .mu.m microchannel thickness.
[0044] FIG. 22 is a graph of soybean oil conversion (%) versus time
(minutes) providing a survey of the work of others, as reported by
Noureddini & Zhu, (1997), showing that the conversion of
soybean oil to methyl esters in a batch reactor is a reaction
process with changing mechanisms reflected in a sigmoidal
conversion curve for soybean oil conversion.
[0045] FIG. 23 is a graph of soybean oil conversion (%) versus time
(minutes) comparing batch reactors to microreactors.
[0046] FIG. 24 is a graph of soybean oil conversion (%) versus time
(minutes) comparing batch reactors to microreactors.
[0047] FIG. 25 is a graph of soybean oil conversion (%) versus time
(minutes) comparing microreactors having 100 .mu.m and 200 .mu.m
microchannels.
[0048] FIG. 26 is a graph of methyl ester concentration (mol/l)
versus time (minutes) comparing microreactors having 100 .mu.m and
200 .mu.m microchannels.
[0049] FIG. 27 is a graph of methyl ester concentration (mol/l)
versus mean residence time (minutes) comparing microreactors having
100 .mu.m and 200 .mu.m microchannels.
[0050] FIG. 28 is a graph of soybean oil conversion (%) versus mean
residence time (minutes) comparing production results to modeling
results for a 100 .mu.m microchannel.
[0051] FIG. 29 is a graph of soybean oil conversion (%) versus mean
residence time (minutes) comparing production results to modeling
results for a 200 .mu.m microchannel.
DETAILED DESCRIPTION
I. Biodiesel, Fats, Oils and Alcohols
[0052] Biodiesel is defined as a mixture of mono alkyl esters of
long chain fatty acids derived from renewable lipid sources. Fats
and oils, also referred to as triglycerides, are primarily
water-insoluble, hydrophobic substances in the plant and animal
kingdom comprising one mole of glycerol and three moles of fatty
acids. Natural vegetable oils and animal fats are extracted or
pressed to obtain crude oil or fat. These usually contain free
fatty acids, phospholipids, sterols, water, odorants and other
impurities. Even refined oils and fats may contain small amounts of
free fatty acids and water. Vegetable oils generally are liquids at
room temperature while fats typically are solids at room
temperature because they contain a larger percentage of saturated
fatty acids. Table 4 summarizes the fatty acid compositions found
in common sources of vegetable oils and fat.
TABLE-US-00004 TABLE 4 Typical Fatty Acid Composition of Common Oil
Sources Fatty acid composition, % by weight Vegetable Lauric
Myristic Palimitic Stearic Oleic Linoleic Linolenic Oil & Fat
12:00 14:00 16:00 18:00 18:01 18:02 18:03 Soybean 0.1 0.1 10.2 3.7
22.8 53.7 8.6 Cottonseed 0.1 0.7 20.1 2.6 19.2 55.2 0.6 Palm 0.1
1.0 42.8 4.5 40.5 10.1 0.2 Lard 0.1 1.4 23.6 14.2 44.2 10.7 0.4
Tallow 0.1 2.8 23.3 19.4 42.4 2.9 0.9 Coconut 46.5 19.2 9.8 3.0 6.9
2.2 0.0
[0053] General chemical structural formulas and chemical schemes
involving triglycerides and exemplary fatty acids are provided
below.
##STR00003##
With reference to this general triglyceride formula, R.sub.1,
R.sub.2 and R.sub.3 independently are fatty acids. Fatty acids vary
in carbon chain length and in the number of sites of unsaturation.
For example, the fatty acids may have carbon chain lengths ranging
from at least as low as 10 carbon atoms to at least 20 carbon
atoms, and more typically about 12 carbon atoms, such as with
lauric acid, up to at least 18 carbon atoms, such as with stearic,
oleic, linoleic or linolenic acid. Sites of unsaturation typically
are double bonds, although compounds having different sites of
unsaturation, such as triple bonds, also potentially are useful
fuel sources. Numerical indications used herein adjacent fatty
acids, e.g. 18:2 for linoleic acid, indicate the number of carbon
atoms (18 in this example), and the number of sites of unsaturation
(2, in this example). Examples of saturated fatty acids include,
but are not limited to:
##STR00004##
[0054] Examples of unsaturated fatty acids include, but are not
limited to:
##STR00005##
[0055] The primary sources of oils and fats for use in biodiesel
production are soy, inedible tallow and grease, corn, edible tallow
and lard, cotton, sunflower, canola, peanut, rapeseed and
safflower. Soy oil accounts for about 58% of the total oil and fat
production, and is by far the largest available product for
biodiesel production. Much of the research and promotion for
biodiesel production has come from national and state soybean
associations.
[0056] Scheme 1 illustrates one embodiment of a method for making
biodiesel according to the present invention. This embodiment
involves transesterification of vegetable oil or animal fat with an
alcohol. Transesterification can be accomplished according to the
present invention using a microreactor and any suitable process,
such as by using a catalyst or not, and/or using supercritical
conditions, to yield glycerin and biodiesel according to Scheme
1.
##STR00006##
[0057] Scheme 1 also illustrates the use of an alcohol, ROH, for
transesterification. Any alcohol suitable for performing the
transesterification reaction can be used to practice embodiments of
the present invention. The alcohol generally is a lower aliphatic
alcohol, i.e. an alcohol having 10 or fewer total carbon atoms.
Thus, R typically is a C1-C10 aliphatic chain, more typically an
alkyl, alkenyl and/or alkynyl group. Specific examples of suitable
alcohols include, but are not limited to, methanol, ethanol,
propanol, butanol and amyl alcohol. Methanol and ethanol are used
most frequently. Ethanol is a useful alcohol, at least in part,
because it is derived from agricultural products, is renewable and
less environmentally objectionable than other commonly used
alcohols. However, methanol is primarily used because of its low
cost and its physical and chemical advantages (polar and shortest
chain alcohol). Methanol quickly reacts with triglycerides, and
typical catalysts, such as metal hydroxides, are more readily
soluble in methanol than other alcohols.
[0058] Theoretically, to complete a transesterification reaction
stoichiometrically, a 3:1 molar ratio of alcohol-to-triglycerides
is needed. In practice, this ratio needs to be higher to shift the
equilibrium to product side to provide maximum ester yield. A
higher molar ratio results in a greater ester conversion in a
shorter time. Many oils, including soybean, reach their highest
conversions (93-98%) at a 6:1 alcohol/triglyceride molar ratio.
[0059] A catalyst may be used to improve the reaction rate and
yield. Any suitable catalyst can be used. Exemplary classes and
species of catalysts include metals, such as Pt, Pd, Ag, Ni, Zn, Fe
etc.; metal oxides, such as FeO, Fe.sub.2O.sub.3, Fe.sub.3O.sub.4,
NiO, ZnO, SnO etc.; alkaholic metal hydroxides and carbonates,
particularly methanolic or ethanolic NaOH or KOH; sodium and
potassium alkoxides, such as sodium methoxide, which is more
effective than sodium hydroxide, although sodium hydroxide is
cheaper; zeolites; Lewis bases generally; acidic catalysts, such as
sulfuric acid (H.sub.2SO.sub.4); enzymatic catalysts; and
combinations thereof. Alkali-catalyzed transesterification proceeds
approximately 4,000 times faster than that catalyzed by the same
amount of an acidic catalyst; thus, alkali-catalyzed
transesterification is a preferred embodiment. However, if a
triglyceride has a higher free fatty acid content (>0.5%) and
more water, acid-catalyzed transesterification is preferred. For an
alkali-catalyzed transesterification, the triglycerides and alcohol
must be substantially anhydrous to avoid soap production, which
lowers the yield of esters. Furthermore, separating ester and
glycerol, and the water washing steps, are performed with
difficulties. The product stream of the transesterification
reaction consists mainly of esters, glycerol and traces of alcohol,
catalyst and tri-, di-, and monoglycerides.
[0060] Transesterification can occur at different temperatures,
depending on the oil. Typically, higher temperatures increase the
reaction rate and yield of esters. Thus, the temperature at which
the transesterification reaction is conducted can vary from at
least as low as ambient (about 25.degree. C.) to at least as high
as the degradation temperature of reactants and/or products,
typically less than about 400.degree. F., more typically less than
about 350.degree. F., and even more typically less than about
250.degree. F., and any temperature within this range.
[0061] Certain embodiments also can be conducted at supercritical
conditions relative to the alcohol component. For example,
transesterification can be conducted using supercritical methanol
at a temperature of about 350.degree. C. A person of ordinary skill
in the art will appreciate that pressure also can influence
supercritical conditions, and further that there is a relationship
between the temperature and pressure and whether a fluid is
supercritical. For methanol the pressure can be at least as high as
45 MPa. A person of ordinary skill in the art also will appreciate
that the conditions resulting in supercritical fluid depend on the
fluid itself. Hence if an alcohol other than methanol is used for
supercritical fluid transesterification, then the supercritical
conditions will be other than that stated for methanol to exemplify
this process. Supercritical conditions can be determined by
consulting a phase diagram for particular compounds.
II. Microreactors
[0062] Microreactors are usually defined as miniaturized reaction
vessels fabricated, at least partially, by methods of
microtechnology and precision engineering. The characteristic
dimensions of the internal structure of microreactor fluid channels
can vary substantially, but typically range from the sub-micrometer
to the sub-millimeter range. Microreactors most often are designed
with microchannel architecture. These structures contain a large
number of parallel channels, often with common inlet/outlet flow
regions. Each microchannel is used to convert a small amount of
material. Increased fluid throughput using microreactors is
facilitated usually by a numbering-up approach, rather than by
scale-up approach, although both numbering up and/or scale up
processes can be used to increase throughput. Numbering-up
guarantees that desired features of a basic unit remain unchanged
when increasing the total system capacity.
[0063] The benefits of miniaturized systems, designed with
dimensions similar to microreactors, compared to a large-scale
process include, but are not limited to: large-scale batch process
can be replaced by a continuous flow process; smaller devices need
less space, fewer materials, less energy and often shorter response
times; cost per device can be kept low by parallel microfabrication
and automated assembly; and system performance is enhanced by
decreasing the component size, which allows integration of a
multitude of small functional elements. Smaller linear dimensions
of microreactors increase the respective gradient for a given
difference in some important physical properties in the chemical
reactor such as temperature, concentration, density and pressure.
Consequently, microreactors significantly intensify heat transfer,
mass transport, and diffusional flux per unit volume or unit area.
Typical thickness of the fluid layer in a microreactor can be set
to few tens of micrometers (typically from about 10 to about 500
.mu.m) in which diffusion plays a major role in the mass/heat
transfer process. Due to a short diffusional distance, the time for
a reactant molecule to diffuse through the interface to react with
other molecular species is reduced to milliseconds and, in some
cases, to nanoseconds. Therefore, the conversion rate is
significantly enhanced and the chemical reaction process appears to
be more efficient. Diffusion is no longer a rate determining step.
Also, a decrease in fluid layer thickness increases the
surface-to-volume ratio of microchannels to the range of 10,000 to
50,000 m.sup.2/m.sup.3, whereas typical laboratory and production
vessels do not usually exceed 1000 m.sup.2/m.sup.3 and 100
m.sup.2/m.sup.3, respectively. Other potential benefits of
microreactors include earlier production start at lower costs and
safer operation; easier production scale-up; smaller plant size for
distributed production; lower transportation, materials and energy
costs; and more flexible response to market demands.
[0064] Coinventor, Dr. Brian Paul, also is a coinventor named on
several United States patents and applications concerning devices,
including microreactors, that are made using microlamination
technology. Embodiments of these devices can be used to practice
embodiments of the present invention for making biodiesel. These
patents and applications include U.S. Pat. No. 6,672,502 and No.
6,793,831, application Ser. Nos. 11/086,074 and 11/243,937, as well
as PCT application No. PCT/US2004/035452. Each of these patents and
applications is incorporated herein by reference.
[0065] A particular working embodiment of a microreactor system 110
used to produce biodiesel according to the present invention is
illustrated schematically in FIG. 1. System 110 includes a fluid
delivery system 112 and a microreactor system 114. Certain working
embodiments of the present invention used a dual syringe pump 116
for fluid delivery to microreactor system 114, such as mechanical
syringe pump model 975 from Harvard Apparatus Company. This pump
has a 30-speed mechanical gear box with a positive locking
mechanism. The pump's syringe holder can hold either one or two
syringes of any size from 5 milliliters to 100 milliliters. System
110 has been used to deliver an alcohol and soybean oil to
microreactor system 114. For these embodiments, a first syringe
118, typically a 10 milliliter syringe, was used to deliver
alcohol, and a second syringe 120, typically a 60 milliliter
syringe, was used to deliver soybean oil. Alcohol was delivered by
syringe 118 to the microreactor system 114 through a fluid conduit
122 having an in-line stop valve 124. Similarly, soybean oil was
delivered by syringe 120 to the microreactor system 114 through a
fluid conduit 126 having an in-line stop valve 128.
[0066] The illustrated microreactor 110 had three channels in a
rectangular cross section--one 100 mm wide by 0.8 mm deep, another
100 mm wide by 1.7 mm deep, and the third 135 mm wide by 135 mm
deep. Alcohol and soybean oil were mixed in the microreactor for
varying mean residence times, as discussed further below in the
working examples. Transesterification produced biodiesel and
glycerol, collected in cold trap 132, which allowed effective
separation of the two phases.
[0067] FIG. 2 is a schematic, exploded view of one embodiment of a
microreactor 210 used in working embodiments of the present
invention for making biodiesel. FIG. 2 also illustrates that the
microreactors typically are assembled using plural laminae that,
when appropriately assembled, collectively define the working
microreactor. Certain components used to make microreactor 210 were
purchased from International Crystal Laboratories (Garfield, N.J.).
For example, microreactor 210 includes a front plate 212 and a back
plate 214. Working embodiments of plates 212 and 214 were sealed
liquid cells (model SL-3) having two 304 stainless steel plates
(front plate 212 and back plate 214). Plates 212 and 214 allow
accurate visual alignment of the other cell (microreactor)
components. Each plate 212, 214 has an inlet 216a (inlet 216b of
plate 214 is not shown) and an outlet 218a, 218b having lure type
connectors.
[0068] Microreactor 210 also includes two gaskets 40 and 42. A
working embodiment of microreactor 210 included two viton gaskets
220, 222, each 38.5.times.19.5.times.4 mm. Gaskets 220 and 222
cushion and form seals with metal and optic components.
[0069] Microreactor 210 also includes two optic windows 224 and
226. A working embodiment of microreactor 210 included two polished
crystal optics (CAF2), each 38.5.times.19.5.times.4 mm, which serve
as windows.
[0070] Microreactor 210 also includes spacers 228 and 230. A
working embodiment included two teflon spacers, each
38.5.times.19.5 mm. Each spacer 228, 230 had different thicknesses
(50 .mu.m or 100 .mu.m each). Spacers 228, 230 create space between
windows 220, 224 of the microreactor 210 for the reactant liquids
and to enable assembly of microreactor 210 with accurate
pathlengths.
[0071] FIGS. 3-6 are digital images illustrating microchannels
formed in individual lamina. For example, FIG. 3 is an end
perspective view of a single lamina 300 having plural microchannels
302 extending axially along the long axis of the lamina. Plural
fluid ports 304 also are illustrated, with each microchannel 302
having a fluid port through which fluid, such as an alcohol or an
oil, flows for reaction in the microreactor 300.
[0072] FIG. 4 is a digital image illustrating a dissembled view of
a microreactor 400 comprising plural laminae 402, each of which
defines plural fluid microchannels 404 and plural fluid ports 406
for delivering fluid to the microchannels, as described for the
single lamina illustrated by FIG. 3. FIG. 4 also indicates that
plural such laminae can be used, each having the same
microfeatures, so that increased fluid throughput, and hence
increased biodiesel production, is realized by a numbering up
approach, as opposed to a feature-size scale up approach. FIG. 4
also illustrates two end plates 408, 410 positioned adjacent the
plural microchannel laminae 402. The two end plates 408, 410 also
include a manifold portion 412 formed therein for distributing
fluid flow to the individual microchannels 404.
[0073] FIG. 5 is a schematic perspective exploded view illustrating
positioning plural laminae, each defining microchannels, to
collectively define one embodiment of a microreactor 510 for
producing biodiesel as with the embodiment of FIG. 4. Microreactor
510 includes end plates 512 and 514, and plural laminae 516, 518,
520, 522 and 524, each defining plural microchannels. Microreactor
510 also includes plural manifolds, such as manifolds 526 and 528
for end plate 512, and manifolds 530 and 532 in end plate 514.
Fluids enter and exit the manifolds through fluid ports. For
example, fluids may enter or exit manifold 532 through fluid port
534.
[0074] FIGS. 6-12 are digital images of working embodiments of
microreactor systems useful for making biodiesel according to the
present invention.
[0075] A person of ordinary skill in the art will appreciate that
microreactors suitable for biodiesel synthesis can operate with and
without solid catalysts. Furthermore, the reaction conditions can
be operated either under subcritical or supercritical operating
conditions. The reaction also can be accomplished using cosolvents.
For example, microreactors can be used that operate at
supercritical conditions with addition of a cosolvent. One example,
without limitation, of a suitable cosolvent for supercritical
conditions is CO.sub.2. CO.sub.2 is added as co-solvent to mediate
the temperature and/or pressure of the reaction mixture, whereas
the supercritical conditions otherwise are determined by the
alcohol component used in the reaction mixture.
[0076] FIG. 13 illustrates a first microchannel 1300 and a second
microchannel 1302 having a single phase reaction mixture 1304,
either under subcritical or supercritical conditions, therein.
Microchannel 1300 does not include a catalyst. As an alternative
embodiment, microchannel 1302 does include a catalyst 1305
positioned effectively for catalyzing the production of biodiesel.
Microchannel 1302 includes both a first wall 1306 and a second wall
1308. The illustrated embodiment includes catalyst 1305 associated
with both walls. For example, the catalyst 1305 may be deposited at
the reactor walls for use in subcritical or supercritical operating
conditions. Moreover, the illustrated embodiment of microchannel
1302 has catalyst substantially uniformly distributed along the
length of walls 1306, 1308. A person of ordinary skill in the art
will appreciate that it may not be necessary to have catalyst
associated with both walls of a microchannel, nor that the catalyst
be substantially uniformly distributed on a wall, or walls.
[0077] Oil and alcohol are hydrophobic/hydrophilic respectively to
each other and are immiscible for all practical purposes. One way
to control the interface between oil and alcohol in a reaction
mixture is to use inserts that have a relative small size, such as
from about 20 .mu.m to about 60 .mu.m thick with micrometer size
openings. This interface material can be made from a variety of
materials, such as polymers, metals, and combinations thereof.
Wicking material, woven fabrics or otherwise mashed fiber-like
materials also can be used for this purpose. Without being limited
to a theory of operation, such interface materials use natural
surface tension effects to create a stable interface.
[0078] FIG. 14 is a schematic drawing of a microchannel 1400.
Microchannel 1400 has a first oil phase 1402 and a second alcohol
phase 1404 flowing therethrough. Microchannel 1400 also includes an
interface supporting material 1406. Interface mesh 1406 can also
serve as a substrate for solid catalyst. Mesh material, for example
metals, with stainless steel being one example, can be coated with
solid catalyst materials, such as catalysts particularly useful for
supporting biodiesel synthesis. These materials typically are used
as relatively small particles, such as nanometer-scale particles.
Also the mesh material may have nanoparticles incorporated into its
structure even before the mesh is produced.
III. Biodiesel Production
[0079] A. Simulation
[0080] FIG. 15 illustrates the velocity profile of the two
immiscible reactants, such as methanol and soybean oil, in a
microchannel. As a result of the different physical properties of
these reactants, the thickness of each fluid layer depends on the
volumetric ratio and the ratio of viscosities of the two
substances. The thickness of the oil layer may be important for
modeling and for determining process rate.
[0081] Several assumptions were made to construct the model,
including, the system is under steady state conditions, velocity in
the z direction (u.sub.z) and y direction (u.sub.y) are equal to 0,
velocity in the x direction (u.sub.x) is not 0, and is only a
function of y, the gravity (g) in the x and z directions is equal
to zero (g.sub.x=g.sub.z=0.0); and pressure drop along the x
direction is constant [.DELTA.P=P (x=L)-P (x=0)]. Using these
assumptions, the following equations were derived.
u A = V A , x = m [ 1 + ( b 2 - a aB a ( 1 + b ) ) y - ( a + b aB a
B b ( b + 1 ) ) y 2 ] ( 4 ) u B = V B , x = m [ 1 + ( b 2 - a B a (
1 + b ) ) y - ( a + b B a B b ( b + 1 ) ) y 2 ] Where m = .DELTA.
PB a B b 2 .mu. B L ( 1 + b a + b ) ( 5 ) ##EQU00001##
[0082] Starting with these equations for soybean oil/methanol, the
laminar velocity profile and the definition of the volumetric rate
are:
Q A = w .intg. 0 Ba u A y Q A w = .intg. 0 Ba u A y Q B = - w
.intg. 0 - Bb u B y Q B w = - .intg. 0 - Bb u B y Q A w = m .intg.
0 Ba [ 1 + ( b 2 - a aB a ( 1 + b ) ) y - ( a + b aB a B b ( 1 + b
) ) y 2 ] y Q A wm = B a [ 1 + ( b 2 - a 2 a ( 1 + b ) ) - ( a + b
3 a ( 1 + b ) ) b ] ( 6 ) Q B w = - m .intg. 0 - Bb [ 1 + ( b 2 - a
B a ( 1 + b ) ) y - ( a + b B a B b ( 1 + b ) ) y 2 ] y Q B wm = B
b [ 1 - ( b 2 - a 2 b ( 1 + b ) ) - ( a + b 3 b ( 1 + b ) ) ] ( 7 )
##EQU00002##
After dividing Eq (6) with Eq (7) we obtain,
Q A Q B = b [ 1 + ( b 2 - a 2 a ( 1 + b ) ) - ( a + b 3 a ( 1 + b )
) b 1 - ( b 2 - a 2 b ( 1 + b ) ) - ( a + b 3 b ( 1 + b ) ) ] ( 8 )
##EQU00003##
The thickness layer ratio "b" is calculated by replacing the
viscosity ratio "a" and appropriate values of "b" into equation
(8). Since the equation is nonlinear and implicit, a trial and
error method was used to determine "b," which will yield the
correct ratio of
Q A Q B = 3.4 : ##EQU00004##
Soybean oil (.mu..sub.A)=5.825*10.sup.-2 PaS (25.degree. C.)
Methanol (.mu..sub.B)=5.47*10.sup.-4 PaS (25.degree. C.) Where
[0083] a = .mu. A .mu. B = 106.5 ##EQU00005##
TABLE-US-00005 TABLE 5 Soybean oil/Methanol Phases Thickness Ratio
(b) Thickness Layer Ratio "b" Q.sub.A/Q.sub.B 1 0.062 2 0.349 3
0.933 4 1.797 5 2.883 5.43 3.402 The obtained thickness layer ratio
is b = 5.43 For a 100 .mu.m .mu.-channel thickness: B.sub.a = 84.4
* 10.sup.-6 m (84.4 .mu.m) and B.sub.b = 15.6 * 10.sup.-6 m (15.6
.mu.m). For a 200 .mu.m .mu.-channel thickness, B.sub.a = 168.75 *
10.sup.-6 m (168.75 .mu.m), and B.sub.b = 31.25 * 10.sup.-6 m
(31.25 .mu.m).
[0084] B. Chemical Reactions
[0085] Production of biodiesel by transesterification reactions,
such as transesterification of soybean oil (A) with methanol (B),
consists of several consecutive, reversible reactions. Without
being limited to a particular theory of operation, one reaction
pathway involving consecutive reversible reactions is shown below.
The first proposed step is converting soybean oil, which is a
triglyceride, to diglycerides (DG). This conversion is then
followed by conversion of diglycerides to monoglycerides (MG), and
finally by conversion of monoglycerides to glycerol (GL). After the
conversions, three moles of methyl esters (M) are obtained for each
triglyceride reacted.
Triglyceride (A)+Methanol (B) Diglyceride (DG)+Methyl ester (M)
Diglyceride (DG)+Methanol (B) Monoglyceride (MG)+Methyl ester
(M)
Monoglyceride (MG)+Methanol (B) Glycerol (GL)+Methyl ester (M)
Step Reactions:
##STR00007##
[0086] Overall Reaction:
##STR00008##
[0087] EXAMPLES
[0088] The following examples are provided to exemplify particular
features of working or hypothetical examples. A person of ordinary
skill in the art will appreciate that the invention is not limited
to the specific features recited in these examples.
Materials
[0089] Refined, bleached, and deodorized soybean oil (Crisco Brand)
was obtained from J. M. Smucker Company (Orrville, Ohio). Reference
standards, such as methyl linoleate, methyl linolenate, methyl
stearate, methyl palmitate, and methyl oleate, having a minimum
purity of 99%, were purchased from Sigma-Aldrich Company (Saint
Louis, Mo.). Analytical grade methanol was purchased from EMD
Chemicals Inc. (Canada). Sodium Hydroxide Pellets, 99% pure, were
purchased from Mallinckrodt Baker, Inc. (Paris, Ky.).
Example 1
[0090] This example concerns transesterification of soybean oil at
room temperature (25.degree. C.) and at atmospheric pressure using
a working embodiment of a microreactor as described above. A
10-milliliter syringe was filled with a stock solution comprising
dried sodium hydroxide dissolved in 10 milliliters of methanol. Two
steps were required to prepare a stock solution of methanolic
sodium hydroxide (NaOH). First, the amount of NaOH required for the
transesterification reaction had to be calculated. Second, NaOH was
dried before being dissolved in methanol. The amount of NaOH used
for transesterification represented 1.0 wt % of the soybean oil
used for the transesterification reaction. The amount of sodium
hydroxide to be used was calculated according to the following
formula:
Na O H amount ( g ) = 1 % * volume of soybean oil in 60 milliliter
syringe * sp gr . = 0.01 * 34 milliliters * 0.885 = 0.3 g to be
dissolved in each 10 milliliters of methanol ##EQU00006##
1.8 grams of NaOH were dried for a few hours at a temperature of
about 106.degree. C. After drying, NaOH was dissolved in 60
milliliters of methanol. This stock solution was filtered to remove
small particles that potentially might obstruct flow in the
microreactor. For the transesterification reaction, a 10 milliliter
syringe was filled with methanolic NaOH stock solution.
[0091] A second 60-milliliter syringe was filled with 34
milliliters of soybean oil. The soybean oil/methanol molar ratio
calculation was performed using the following data: soybean oil
molecular weight=872.4; specific gravity of soybean oil=0.885
g/milliliter; methanol molecular weight=32, methanol specific
gravity=0.792 g/milliliter; the weight of one mole of soybean
oil=1*872.4=872.4; the volume of one mole of soybean
oil=872.4/0.885=985.76 milliliters. The pump volume flow rate ratio
for a 60 milliliter syringe and a 10 milliliter syringe of soybean
oil/methanol is 3.4. This value was used to calculate the methanol
volume from the soybean oil volume.
Volume of methanol = 985.76 3.4 = 290 milliliters ##EQU00007##
Weight of methanol = 290 * 0.792 = 229.7 g ##EQU00007.2## Moles of
methanol = 229.7 32 = 7.2 moles ##EQU00007.3##
As a result, the molar ratio of soybean oil/methanol provided by
using a 60 milliliter syringe and a 10 milliliter syringe was
1:7.2.
[0092] Both the 10-milliliter and the 60-milliliter syringes were
installed in the syringe pump. The syringe pump delivered the two
solutions to the microreactor at a constant volumetric flow rate
ratio of soybean oil-to-methanol of 3.4:1, which corresponds to the
calculated 1:7.2 soybean oil/alcohol molar ratio. Six syringe pump
flow positions were used. Flow position numbers 20, 22, 24, 26, 28
and 30 were used for the 100 .mu.m .mu.-channel thickness. These
flow positions correspond to the following mean residence times
(MRT): 0.41, 0.79, 1.69, 3, 5.3, and 10 minutes. Flow position
numbers 18, 20, 22, 24, 26 and 28 were used for the 200 .mu.m
.mu.-channel thickness, which correspond the following MRT: 0.43,
0.82, 1.58, 3.37, 6.05, and 10.63 minutes. In both cases the MRT
was based on the soybean oil phase since it had a higher flow rate
than the methanol. Syringe pump flow rates are summarized below in
Table 6.
TABLE-US-00006 TABLE 6 Syringe Pump Flow Rate 60 milliliter syringe
10 milliliter Syringe Pump Flow flow Rate Flow Rate Flow rate
Position (Q.sub.A, milliliter/min) (Q.sub.B, milliliter/min) Ratio
(Q.sub.A/Q.sub.B) 18 0.107 0.032 3.34 20 0.0559 0.0164 3.4 22
0.02915 0.0085 3.42 24 0.01363 0.00394 3.46 26 0.00760 0.0022 3.45
28 0.004328 0.0013 3.33 30 0.002314 0.0006615 3.49 Average 3.4
Ratio
[0093] Fluids from both syringes were pumped into a microreactor
.mu.-channel, where they formed two layers with different
thicknesses as shown in the soybean oil/methanol laminar velocity
profile, FIG. 15. The layer thicknesses of the soybean oil and
methanol inside the microreactor were determined by their
viscosities and flow rate ratios as calculated above. The
microreactor reaction channel dimensions were 2.33 cm length, 1.05
cm width, and 100 or 200 .mu.m in height, depending on the spacer
thickness used.
[0094] Fluid flowed out of the microreactor as a two-phase stream
and was collected in a cold trap (0.degree. C.), mainly to stop any
further reaction in the test tube. The two phases in the test tube
were further separated by centrifuge. The volumes of both phases
were recorded and then parts of both phases were stored in vials
for methyl esters analysis by gas chromatography (GC). Gas
chromatographic HP model 5890 Series II was used to determine
methyl ester concentrations. A Nukol capillary column (30
m.times.0.53 mm ID, 1.0 .mu.m film) with an operating temperature
limitation (60.degree. C. to 200.degree. C.) was used, along with a
pre-installed flame ionization detector (FID). Liquid samples (1
.mu.l each) were injected using a splitless injection method. Data
was collected using the HP Integrator model 3396 Series II.
[0095] Five compounds were used as methyl ester standards: methyl
palmitate, methyl stearate, methyl oleate, methyl linoleate, and
methyl linolenate. These standards were used to identify biodiesel
(methyl ester) peaks in the recorded chromatographs.
Identifications were established by comparing retention times of
both reference standards with eluted sample peaks. The biodiesel
peaks were eluted in the following retention times: methyl
palmitate (9 minutes), methyl stearate (16.3 minutes), methyl
oleate (17.5 minutes), methyl linoleate (20.5 minutes), methyl
linolenate (25.3 minutes).
[0096] Four steps were required to calculate the soybean oil
conversions. First, Relative Response Factors (RRFs) were
determined for each methyl ester standard. Second, the methyl ester
moles at the biodiesel phase in the experimental sample were
determined. Third, the soybean oil reacted from the total methyl
esters moles existing at the biodiesel phase of the experimental
sample were calculated. Fourth, the soybean oil entered in the
transesterification reaction was calculated. Each step is explained
in detail in the following paragraphs.
[0097] To determine the RRF of each methyl ester standard, five
methyl ester concentrations were prepared from standard methyl
ester samples having a minimum purity of 99%. 5 .mu.l or equivalent
weight from each methyl ester standard was diluted into 6,000 .mu.l
of hexane to give a 0.000833 .mu.l mole ester/.mu.l hexane
concentration. These five methyl ester standards were analyzed in
the GC twice, before and after running the biodiesel samples, to
check for any inconsistencies or shifts over the duration of the
analysis. The differences in the GC standard areas for both runs
(before and after analyzing the experimental samples) ranged from
1% to 4.7%. The RRF (concentration over GC standard area) for each
methyl ester standard was calculated and was used to determine the
corresponding methyl ester concentration in the biodiesel phase.
RRFs are provided below in Table 7.
TABLE-US-00007 TABLE 7 Standard Methyl Ester Relative Response
Factors (RRFs) Methyl Ester Methyl Standard GC Methyl Name
Concentration Standard Area RRFs Methyl palmitate 0.000833 2278422
3.656e-10 Methyl stearate 0.000833 2290152 3.637e-10 Methyl oleate
0.000833 2225547 3.743e-10 Methyl linoleate 0.000833 2272309
3.666e-10 Methyl linolenate 0.000833 2304266 3.615e-10
[0098] To determine the methyl ester moles at the biodiesel phase
in a typical analysis, 5 .mu.l of the biodiesel phase experimental
sample at each MRT was diluted with a solvent (hexane). The amount
of solvent (1,000 to 4,000 .mu.l) used depended on the biodiesel
concentration in the sample. One .mu.l of the diluted sample was
injected into the GC to obtain the chromatographic record. To
calculate the concentration of each methyl ester in one .mu.l of
the diluted sample, the peak area obtained in the chromatograph was
multiplied by the corresponding RRF of the standard methyl ester.
Once the concentration of each methyl ester was determined, the
moles of each methyl ester in the biodiesel phase sample was
calculated.
[0099] The overall transesterification reaction showed that three
moles of methyl esters were obtained for each soybean oil
(triglyceride) milliliter reacted. To calculate the amount of
soybean oil reacted at each MRT, the total moles of methyl esters
in the biodiesel phase were divided by three to get the moles of
soybean oil reacted.
[0100] To calculate the soybean oil moles entered in the reaction
at each MRT, 77.27% of the total product sample volume (biodiesel
phase+glycerol phase) was assumed to be originally soybean oil and
the rest to be methanol. This assumption was based on the syringes'
flow rate volume ratio of soybean oil-to-methanol, which was 3.4:1
or 77.27%:22.72%. The conversion of soybean oil in the
transesterification reaction was calculated by dividing the reacted
soybean oil by the soybean oil which entered the reaction.
Example 2
[0101] This example concerns biodiesel production using a
microreaction process, and one embodiment of a microreactor having
an adjustable .mu.-channel thickness (100 .mu.m or 200 .mu.m) as
previously described. To show that biodiesel production is feasible
in the microreaction process, two sets of soybean oil
transesterification procedures were performed in the microreactor.
A first production run used a microreactor having a 100 .mu.m
.mu.-channel thickness (spacers) and the other run was with a 200
.mu.m .mu.-channel thickness (spacers). This was done to assess the
effect of .mu.-channel thickness on biodiesel production. Both
production runs were conducted at the same operating conditions:
7.2:1 methanol/soybean oil molar ratio; 1.0 wt % (with respect to
oil) NaOH catalyst; room temperature (25.degree. C.); atmospheric
pressure; and substantially the same mean residence times
(MRT).
[0102] A 10-milliliter syringe was filled with a stock solution of
dried sodium hydroxide dissolved in methanol. Another 60-milliliter
syringe was filled with 34 milliliters of soybean oil. The syringe
pump delivered the two solutions from both syringes to the
microreactor at a constant volumetric flow rate ratio. The ratio of
the flow rates of soybean oil to methanol was 3.4:1 which
corresponds to a 1:7.2 molar ratio.
[0103] The reaction products flowed from the microreactor in two
phases: a biodiesel phase and a glycerol phase. Both phases were
collected in a single container. Part of the biodiesel phase was
diluted and injected into the GC to obtain peak records of the
methyl esters. Using the methyl esters standards, the recorded
chromatographic values were converted into methyl esters
concentrations at different MRT.
[0104] For production runs using the microreactor with a 100 .mu.m
thickness, six volumetric flow rates (0.0559, 0.02915, 0.01363,
0.00760, 0.004328, 0.002314 milliliter/min) were used. These
volumetric flow rates corresponded to MRTs of 0.41, 0.79, 1.69, 3,
5.3, and 10 min. Each experiment corresponds to one MRT.
[0105] FIG. 16 shows that soybean oil conversion increases with
MRT. Soybean oil conversion ranges from 12.33% at 0.41 MRT to 91.1%
at 10 minutes MRT. Remaining unconverted reactant is not pure
soybean oil but it instead contains some intermediate reactants,
such as diglycerides and monoglycerides. However, the remaining
percentage was considered to be pure soybean oil due to lack of an
analytical method useful for measuring the concentrations of these
intermediates. Therefore, the conversions of soybean oil in reality
may be higher than stated.
[0106] FIG. 17 provides the total methyl ester concentration as a
function of MRT. The methyl esters concentration ranges from 0.355
mol/l at 0.41 minute MRT to 2.56 moles/l at 10 minutes MRT.
[0107] FIG. 18 shows individual methyl ester concentrations at
different MRTs. The differences in the concentration of each methyl
ester at a given MRT depend on the original composition of fatty
acids in the soybean oil.
[0108] For production runs using the microreactor having a 200
.mu.m thickness, six volumetric flow rates (0.107, 0.0559, 0.02915,
0.01363, 0.00760 and 0.004328 milliliter/min) were used. These
volumetric flow rates corresponded to MRTs of 0.43, 0.82, 1.58,
3.37, 6.05 and 10.63 min. Each production run corresponds to one
MRT.
[0109] FIG. 19 shows that soybean oil conversion increases with the
MRT. For the disclosed working embodiments, the soybean oil
conversion ranged from 4.75% at 0.43 MRT to 86.36% at 10.63 minutes
MRT.
[0110] FIG. 20 shows that the total methyl esters concentration is
a function of MRT. The methyl esters concentration ranges from
0.136 mol/l at 0.43 minute MRT to 2.45 moles/l at 10.63 minutes
MRT.
[0111] FIG. 21 shows individual methyl ester concentrations at
different MRTs. The differences in the concentration of each methyl
ester at a given MRT depend on the original composition of fatty
acids in soybean oil. t-test statistic of the mean difference for
the experimental data obtained for soybean oil conversion in both
thicknesses (100 and 200 .mu.m) establish that the two sets of
experimental data are statistically different.
[0112] A survey of the work of other researchers, as reported by
Noureddini & Zhu, (1997), shows that the conversion of soybean
oil to methyl esters in a batch reactor is a reaction process with
changing mechanisms. These mechanisms are reflected in a sigmoidal
conversion curve for the soybean oil conversion as shown in FIG.
22, which illustrates transesterification reaction mechanisms in a
batch reactor using a stirrer operating at 300 rpm and 50.degree.
C. using a 6:1 molar ratio (methanol:soybean oil).
[0113] The transesterification reaction process in the batch
reactor clearly exhibits three different rates: a) an initial
mass-transfer-controlled region (slow rate) followed by b) a
kinetically controlled region (fast rate) and c) a final slow
region when equilibrium is approached. In a batch reactor, soybean
oil and methanol are not miscible and form two liquid phases upon
their initial introduction into the reactor. The reaction process
is diffusion-controlled. Slowly diffusing reactants in two
different phases results in a slow reaction rate. Mechanical mixing
increases the contact between the reactants, resulting in an
increase in the mass transfer rate. The duration of the slow rate
region decreases as the mixing intensity increases. The mixing
effect is most significant during the slow rate region of the
reaction. As a single phase is established, increased mixing
intensity becomes insignificant and the reaction rate primarily is
influenced by the reaction temperature.
[0114] One benefit of using a microreactor for producing biodiesel
is the mass transfer intensification. Eliminating the mass
transfer-controlled regime in the transesterification reaction
process is one of the main reasons for applying microreactor
technology to biodiesel production. Setting the thickness of
soybean oil and methanol layers in a microreactor to a few tens of
micrometers (100 .mu.m and 200 .mu.m in disclosed working
embodiments) allows diffusion to play a major role in the mass
transfer-controlled region. Because there is a short diffusion
distance, the time required for a reactant molecule to diffuse
through the interface to react with other molecular species is
reduced to seconds and in some cases to milliseconds. The
conversion rate therefore is significantly enhanced and the
transesterification reaction process appears to be more efficient.
The diffusion-controlled region is no longer a rate-determining
step.
[0115] FIGS. 23 and 24 compare the soybean oil conversions obtained
in a microreactor (100 .mu.m and 200 .mu.m; 25.degree. C.) and the
conversions obtained in a batch reactor (30.degree. C., 50.degree.
C. and 70.degree. C.) as reported by Noureddini & Zhu, 1997.
Noureddini, H. (University of Nebraska); Zhu, D. Kinetics of
transesterification of soybean oil, JAOCS, Journal of the American
Oil Chemists' Society, V. 74, n 11, November, 1997, p 1457-1463. In
the batch reactor, 90% conversion is achieved after 90 minutes at
70.degree. C. This conversion decreases to 80% and 65% as the
reaction temperature decreases to 50.degree. C. and 30.degree. C.,
respectively. In working embodiments of microreactors having 100
and 200 .mu.m thicknesses, 91% and 86% conversions, respectively,
were obtained in a 10 minute period at 25.degree. C. This confirms
that the microreactor-based process produces biodiesel much more
efficiently than a batch process. For industrial applications,
changing the production technology and reducing process times and
temperatures would result in substantial cost reduction, increased
production capacity and lower maintenance.
[0116] Improvement in the overall process performance is achieved
when the microreactor (.mu.-channel) thickness is reduced from 200
.mu.m to 100 .mu.m. Reducing the diffusion distance improves mass
transfer and reduces diffusion time for reactant molecules to react
with each other. FIGS. 25 and 26 show these process improvements.
The soybean oil conversion increases from 86% to 91% and total
methyl esters concentrations increase from 2.45 to 2.59
moles/l.
[0117] FIG. 27 shows the increase in concentrations for each methyl
ester between 100 .mu.m and 200 .mu.m. Again, this emphasizes the
advantage of the microreaction process in processes requiring
mechanical mixing to improve mass transfer. The microreactor
process is faster than processes performed in conventional reactors
if mass transfer is an important step in the chemical process
rate.
[0118] Derived mathematical models and production data of soybean
oil conversion using the microreactor having 100 .mu.m thickness
were used to estimate the reaction rate constants (k.sub.1). Finite
Element Method Laboratory (FEMLAB) Software was used to solve the
mathematical model numerically. The reactions rate constants
(k.sub.1 to k.sub.6) were estimated by fitting the experimentally
obtained conversions to the predicted model conversions. The
published values of the reaction rate constants obtained in a batch
reactor for soybean oil transesterification reactions, as reported
by Noureddini & Zhu, 1997, were first used to estimate reaction
rate constants in the microreactor. Rate constants obtained in the
batch reactor were most probably impacted and determined under the
influence of mass transfer caused by a mechanical stirrer. The mass
transfer influence is particularly swaying in two-phase systems.
Conventional stirring techniques have definite limitations as to
the characteristic minimum droplet size of the dispersed phase in
the two-phase system. Stirring typically produces a wide range of
droplet distribution, thus causing a wide range of pathlength
diffusion and characteristic diffusion times. More importantly, in
any stirring process a mixing regime is reached when additional
increases in stirring intensity does not significantly change the
droplet size distribution of the dispersed phase. Under these
conditions most investigators who use conventional batch reactors
conclude that mass transfer influence is eliminated from the
process and that the observed process kinetics can be credited
completely to chemical reaction kinetics. For all practical
purposes, this approach is sufficiently correct as any industrial
size process typically operates with mixing power input several
orders of magnitude smaller than those achieved under laboratory
conditions.
[0119] However, in microchannel reactors, the characteristic
diffusion length may be reduced to a size that is often much
smaller than the characteristic droplet size attained in a
conventional mixing. For certain working embodiments of the present
invention, the characteristic diffusion length is approximately 100
.mu.m, which is the thickness of the film obtained in the
microreactor. Furthermore, this diffusion length is maintained
approximately uniformly throughout the reactor, and it is achieved
without mixing or power consumption. These conditions are much more
favorable to the chemical reaction process and the reaction rate
process therefore likely will increase. Regardless of the fact that
the rate constants obtained in the batch reactor were determined
under the influence of mass transfer caused by a mechanical
stirrer, their equilibrium constants were much less influenced by
mass transfer contribution. Therefore, these equilibrium constants
are preserved by increasing the rate constants simultaneously at
all MRTs until a good fitting was achieved.
[0120] The best estimated reaction rate constant (k.sub.1) values
for the microreactor with 100 .mu.m are shown in Table 8.
TABLE-US-00008 TABLE 8 Microreactor Rate Constants k.sub.1 k.sub.2
k.sub.3 k.sub.4 k.sub.5 k.sub.6 Values 4.37e-6 9.62e-6 1.88e-5
1.074e-4 2.117e-5 9.0e-7 (m.sup.3 milliliter second)
[0121] For the microreactors with 100 and 200 .mu.m thicknesses,
FIGS. 28 and 29, respectively, show good correlation of production
and model results for soybean oil conversions at different MRTs
using the estimated reaction rate constants (k.sub.1) values. The
microreactor type used for certain working embodiments may be used
to predict soybean oil conversion and biodiesel concentration under
a variety of operating conditions.
[0122] The present disclosure clearly establishes that
microreactors can be used to produce biodiesel, such as by
transesterification of soybean oil. Reducing microreactor
(.mu.-channel) thickness from 200 .mu.m to 100 .mu.m improved the
overall process performance. In the microreactor with a 100 .mu.m
thickness (spacers), a 91% soybean oil conversion (2.59 moles/l
biodiesel concentration) was achieved. In the microreactor with a
200 .mu.m thickness, an 86% conversion (2.45 moles/l biodiesel
concentration) was achieved.
Example 3
[0123] This examples concerns determining microreactor residence
time based on the oil phase since it had higher flow rate than
methanol. Residence time was calculated according to the following
equation:
Residence time ( min ) = microreactor chanal volume ( cm 3 ) 60 ml
syringe flow rate through mircoreactor ( cm 3 / min )
##EQU00008##
[0124] A. 100 Micron Microreactor Thickness Residence Time
[0125] The microreactor channel area includes a rectangular area
and a triangle area. The channel volume therefore has been
calculated according to the following definition:
Microreactor channel volume=channel area
(rectangular+triangle)*thickness of oil phase (B.sub.a)
where the rectangular area was 2.3.times.1.05=2.415 cm.sup.2, the
triangular area was 0.5.times.1.05.times.0.6=0.315 cm.sup.2, and
the microreactor channel volume was
(2.415+0.315).times.(84.4/10000)=0.023 cm.sup.3. Table 9 provides
the residence time for a 100 .mu.m microreactor thickness.
TABLE-US-00009 TABLE 9 Pump 60 milliliter syringe Microreactor
Residence Flow flow Rate (Q.sub.A, Channel Time Position
milliliter/min) Volume (cm.sup.3) (min) 20 0.0559 0.023 0.41 22
0.02915 0.023 0.79 24 0.01363 0.023 1.69 26 0.00760 0.023 3 28
0.004328 0.023 5.3 30 0.002314 0.023 10
Table 10 provides the residence time for a 200 .mu.m microreactor
thickness, where the microreactor channel volume was
(2.415+0.315).times.(168.75/10000)=0.046 cm.sup.3.
TABLE-US-00010 TABLE 10 Pump 60 milliliter syringe Microreactor
Residence Flow flow Rate (Q.sub.A, Channel Time Position
milliliter/min) Volume (cm.sup.3) (min) 18 0.107 0.046 0.43 20
0.0559 0.046 0.82 22 0.02915 0.046 1.58 24 0.01363 0.046 3.37 26
0.00760 0.046 6.05 28 0.004328 0.046 10.63
Example 4
[0126] This example concerns determining the amount of soybean
conversion using one embodiment of a microreactor process according
to the present invention. Methyl ester ratio factors were
determined using the following formula:
Ratio factor = methyl standard concentration G C methyl standard
area ##EQU00009##
Table 11 provides standard methyl ester relative response factors
(RRFs)
TABLE-US-00011 TABLE 11 Methyl Ester Methyl Standard GC Methyl Name
Concentration Standard Area RRFs Methyl palmitate 0.000833 2278422
3.656e-10 Methyl stearate 0.000833 2290152 3.637e-10 Methyl oleate
0.000833 2225547 3.743e-10 Methyl linoleate 0.000833 2272309
3.666e-10 Methyl linolenate 0.000833 2304266 3.615e-10
[0127] Performing this calculation first involved analyzing a 5
.mu.l sample of the biodiesel phase in the experimental sample. The
total methyl esters at biodiesel phase of the sample were then
calculated. Finally, the amount of soybean oil reacted and entered
in the transesterification reaction were calculated. The 5 .mu.l
taken from biodiesel phase was diluted using 4,000 .mu.l of hexane.
One .mu.l of the diluted solution was injected into a GC. The
resulting GC areas for each of the methyl esters were multiplied by
the corresponding Relative Response Factors (RRFs) to determine the
concentration of each methyl ester in 1 .mu.l. The concentration of
each methyl ester was multiplied by 4,000 .mu.l of hexane to
determine the concentration in a 5 .mu.l biodiesel sample. The
moles of each methyl ester were calculated in 5 .mu.l followed by
calculating the moles of each methyl ester in the biodiesel phase
of the sample.
[0128] The reacted soy bean oil was calculated by dividing the
total moles of methyl esters in the biodiesel phase by three. The
soybean oil moles entered in the reaction was calculated by
assuming 77.27% of the total products sample volume (biodiesel
phase+glycerol phase) was originally soybean oil and the rest was
methanol. This assumption was based on the syringe flow rate volume
ratio of soybean oil to methanol, which is 3.4:1 or 77.27%:22.72%.
The percent conversion of soybean oil in the transesterification
reaction was calculated by dividing the amount of soybean oil
reacted by the soybean oil entering the reaction. Table 12 provides
the areas of methyl esters sample analysis, 100 .mu.m thickness,
with a 1-minute mean residence time.
TABLE-US-00012 TABLE 12 Retention Residence Methyl Ester Time Time
Type (min) (min) GC Area methyl palmitate 9 10 325323 methyl
stearate 16.3 10 136429 methyl oleate 17.6 10 695992 methyl
linoleate 20.5 10 1619204 methyl linolenate 25.3 10 216570
TABLE-US-00013 TABLE 13 Summary of Experimental Results and
Analysis for Microreactor with 100 .mu.m Thickness Experimental
Sample Volume (milliliter)/ Mean Biodiesel Hexane Residence Phase
GC Areas of Methyl esters in 1 .mu.m Injected Sample Dilution Time
Volume Methyl Methyl Methyl Methyl Methyl Amount Conversion (min)
(milliliter) Palmitate Stearate oleate linoleate linolenate (.mu.m)
(%) 0.41 7.7/6.3 191215 69582 365751 854369 120111 1000 12.33 0.79
8.5/7.4 484809 201420 1045391 2425050 255002 1000 36.98 1.69
5.6/5.2 203395 81272 454879 1032176 132451 4000 66.56 3 6.8/6.3
253044 100467 570985 1319497 178556 4000 84.48 5.3 5/4.3 239830
87929 546143 1269683 169773 4000 74.96 10 4.7/3.8 325323 136429
695992 1619204 216570 4000 91.1
TABLE-US-00014 TABLE 14 Summary of Experimental Results and
Analysis for Microreactor with 200 .mu.m Thickness Experimental
Sample Volume (milliliter)/ Mean Biodiesel Hexane Residence Phase
GC Areas of Methyl esters in 1 .mu.m Injected Sample Dilution Time
Volume Methyl Methyl Methyl Methyl Methyl Amount Conversion (min)
(milliliter) Palmitate Stearate Oleate Linoleate Linolenate (.mu.m)
(%) 0.43 5.6/4.6 74967 23600 140556 331087 43463 1000 4.75 0.82
6.2/4.9 305350 122218 598454 1387648 195037 1000 19.41 1.58 5.5/4.6
247056 102669 541407 1260741 171289 3000 54.85 3.37 5.7/4.8 249555
104971 545144 1274116 163123 4000 74.07 6.05 5.2/4.4 276830 114604
601475 1404626 191850 4000 82.47 10.63 5.8/4.8 300559 123772 651132
1506251 190634 4000 86.36
[0129] The present invention has been described with reference to
particular embodiments. A person of ordinary skill in the art will
appreciate that the invention is not limited to those features
exemplified.
* * * * *