U.S. patent application number 12/252919 was filed with the patent office on 2009-08-06 for pretreatment of coal.
This patent application is currently assigned to IOWA STATE UNIVERSITY RESEARCH FOUNDATION, INC.. Invention is credited to Robert A. DOWNEY, Reed E. OSHEL, John G. VERKADE.
Application Number | 20090193712 12/252919 |
Document ID | / |
Family ID | 40930268 |
Filed Date | 2009-08-06 |
United States Patent
Application |
20090193712 |
Kind Code |
A1 |
VERKADE; John G. ; et
al. |
August 6, 2009 |
PRETREATMENT OF COAL
Abstract
The present invention is directed toward a method of
solubilizing coal. The method includes providing coal and providing
an oxoacid ester of phosphorus or a mixture of an oxoacid of
phosphorus and an alcohol. A blend of the coal, the oxoacid ester
of phosphorus or the mixture of the oxoacid of phosphorus and
alcohol is formed. The blend is then treated under conditions
effective to solubilize the coal.
Inventors: |
VERKADE; John G.; (Ames,
IA) ; OSHEL; Reed E.; (Des Moines, IA) ;
DOWNEY; Robert A.; (Centennial, CO) |
Correspondence
Address: |
NIXON PEABODY LLP - PATENT GROUP
1100 CLINTON SQUARE
ROCHESTER
NY
14604
US
|
Assignee: |
IOWA STATE UNIVERSITY RESEARCH
FOUNDATION, INC.
Ames
IA
CIRIS ENERGY, INC.
Centennial
CO
|
Family ID: |
40930268 |
Appl. No.: |
12/252919 |
Filed: |
October 16, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61025187 |
Jan 31, 2008 |
|
|
|
Current U.S.
Class: |
44/620 |
Current CPC
Class: |
C10L 9/10 20130101; C10L
1/326 20130101 |
Class at
Publication: |
44/620 |
International
Class: |
C10L 1/26 20060101
C10L001/26 |
Goverment Interests
[0002] The subject matter of this application was made with support
from the United States Government under Department of Energy, Grant
No. DE-AC02-06CH11358. The U.S. Government has certain rights.
Claims
1. A method of solubilizing coal comprising: treating coal with at
least one of an oxoacid ester of phosphorus, a mixture of an
oxoacid of phosphorus and an alcohol, or a thioacid ester of
phosphorous, or a mixture of a thioacid of phosphorus and an
alcohol under conditions effective to solubilize at least a portion
of the coal.
2. The method of claim 1, wherein the coal is treated with an
oxoacid ester of phosphorus.
3. The method of claim 2, wherein the oxoacid ester of phosphorous
is formed by mixing an oxoacid of phosphorus and an alcohol.
4. The method of claim 2, wherein the coal is fully solubilized as
a result of said treating.
5. The method of claim 2, wherein the coal is partially solubilized
as a result of said treating.
6. The method of claim 2, wherein the coal is selected from the
group consisting of lignite, brown coal, sub-bituminous coal,
bituminous coal, anthracite, and combinations thereof.
7. The method of claim 2, wherein said treating is carried out at a
temperature of 0 to 200.degree. C.
8. The method of claim 2, wherein said treating is carried out at a
temperature of 80 to 100.degree. C.
9. The method of claim 2, wherein said treating is carried out at a
pH range of 6 to 9.
10. The method of claim 2, wherein the oxoacid ester of phosphorus
is selected from the group consisting of esters of phosphorous
acid, phosphoric acid, hypophosphorous acid, polyphosphoric acid,
and mixtures thereof.
11. The method of claim 3, wherein the oxoacid of phosphorus is
selected from the group consisting of phosphorous acid, phosphoric
acid, hypophosphorous acid, polyphosphoric acid, and mixtures
thereof.
12. The method of claim 3, wherein the alcohol is selected from the
group consisting of methanol, ethanol, ethylene glycol, propylene
glycol, glycerol, pentaerythritol, trimethylol ethane, trimethylol
propane, trimethylol alkane, alkanol, polyol, and mixtures
thereof.
13. The method of claim 3, wherein the mixing has a ratio of the
oxoacid of phosphorus to the alcohol of from 10:1 to 1:10.
14. The method of claim 2 further comprising: regulating the water
content of the blend before or during said treating.
15. The method of claim 14, wherein said regulating the water
content comprises removing water.
16. The method of claim 15, wherein said removing water comprises
molecular sieving.
17. The method of claim 15, wherein said removing water comprises
distillation.
18. The method of claim 15, wherein said removing water comprises
adding a dehydrating agent to the blend.
19. The method of claim 1 further comprising: sonicating the blend
during or after said treating.
20. The method of claim 1 further comprising: treating the coal
with a bioconversion agent.
21. The method of claim 20, wherein the bioconversion agent is a
methanogen.
22. The treated product produced by of the method of claim 1.
23. The bioconverted, treated product of the method of claim
20.
24. A composition comprising solubilized organophosphorus ester
derivatives of coal.
25. The method of claim 1 wherein the coal is present in a
subterranean coal deposit.
26. The method of claim 25 wherein treated coal in said coal
deposit is bioconverted with a bioconverting agent.
27. The method of claim 26 wherein the bioconversion agent is a
consortium of bacteria.
28. The method of claim 27 wherein the consortium includes
methanogens.
29. The method of claim wherein 28 a bacteria consortium is added
to the coal deposit as a bioconversion agent.
30. The method of claim 28 wherein the coal deposit includes a
consortium of bacteria.
31. The method of claim 28 wherein the coal is treated with at
least one oxoacid ester of phosphorous.
32. The method of claim 31 wherein an aqueous solution containing
at least one oxoacid ester of phosphorous is introduced into the
coal bed.
33. The method of claim 32 wherein said oxoacid ester of phosphorus
is produced in said solution from the corresponding oxoacid of
phosphorus and the corresponding alcohol.
34. The method of claim 31 wherein the solution contains a
phosphite ester.
35. The method of claim 34 wherein the phosphite ester is a
diester.
36. The method of claim 34 wherein the phosphite ester is a
monoester.
37. The method of claim 34 wherein the solution contains a
phosphite monoester and a phosphite diester.
Description
[0001] This application claims benefit of the priority date of U.S.
Provisional Patent Application Ser. No. 61/025,187, filed Jan. 31,
2008, which is hereby incorporated by reference in its
entirety.
FIELD OF THE INVENTION
[0003] The present invention relates to solubilization of coal.
BACKGROUND OF THE INVENTION
[0004] In the study of coal structure, organic solvents are often
used to extract coal components. These solvents include carbon
disulfide, N-methyl-2-pyrrolidinone, pyridine, tetrahydrofuran, and
tetracyanoethylene which are used separately or in combination
(Shui, H. et al., Fuel, 85: 1798 (2006) and references therein;
Larsen, J. Energy & Fuels, 4:107 (1990) and references therein;
Takanohashi, T. et al. Energy & Fuels, 9: 788 (1995) and
references therein; Liu, H.-T. et al. Energy & Fuels, 7: 1108
(1993) and references therein). The extraction of coals with
pyridine is also an operation frequently used in the coal
industry.
[0005] Early in the coalification process, formation of low-grade
coals, such as lignite occurs. These coals have relatively high
contents of partially coalified plant lignins compared with higher
grade coals such as bituminous, sub-bituminous and anthracite coals
which have higher carbon and lower oxygen contents.
[0006] Lignite deposits frequently harbor methanogenic bacteria
which are able to convert the coal to methane. As is typical with
bacterial processes, however, the production of methane is slow. It
is desirable, therefore, that a solvent system be developed to
solubilize coal in such a manner as to allow methanogenic bacteria
greater access to the coal material, without causing significant
toxicity to the bacteria.
[0007] Methods for the degradation of cellulosic materials to
oligosaccharides and sugar alcohols aimed at facilitating ethanol
production continue to be the subject of wide and intense interest.
Such methods include cellulose treatment with enzymes, mainly
cellulases and hemicellulases (Demain, A. L., et. al., Microbiol.
Molec. Biol. Rev. 69: 124 (2005); Fan, L. T., et. al., Cellulose
Hydrolysis, Springer, Berlin (1987); Zhang, Y. P., et al.,
Biotechnol. Bioeng., 88: 797 (2004)), mineral acids (Mok. W. S.,
et. al., Ind. Eng. Chem. Res., 31: 94 (1992)), bases (Ishida, M.,
et. al., J. Chem. Technol. Biotechnol., 80: 281(2005)),
supercritical water (Sasaki, M., et. al., Ind. Eng. Chem. Res. 39:
2883 (2000)), hot water in the presence of a strongly acidic cation
exchange resin (Kim, Y. M., et. al., BIOT-323, Abstracts of Papers,
225.sup.th ACS national Meeting, New Orleans, La., Mar.
23-27(2003); and Ladisch, M. R., et. al., AGFD-103, Abstracts of
Papers, 225.sup.th ACS national Meeting, New Orleans, La., Mar.
23-27, 2003)), hot water solutions of lanthanide salts (Japanese
Patent application JP 2002085100), and, more recently, platinum or
ruthenium-supported catalysts that accomplish conversion to sugars
(Fukuoka, A., et. al., Angew. Chem. Int. Ed,. 45: 5161(2006)).
[0008] Approaches to simple disruption of the hydrogen bonds in
cellulose have also been described. Examples include hot water
treatment (Kobayashi, N., et. al., World Congress of Chemical
Engineering, 7.sup.th, Glasgow, United Kingdom, Jul. 10-14, 2005),
pH controlled hot water treatment (Mosier, N., et. al., Biores.
Technol., 96: 6, 673-686 (2005); and Mosier, N. S., et. al., Appl.
Biochem. & Biotech., 125: 77-85 (2005)), extrusion/explosion
processing of ammonia-impregnated fibers (AFEX) (Dale, B. E., et.
al., Appl. Biochem. Biotechnol. 77-79 (1999); and Liu, N., et. al.,
"Research Progress of Converting Lignocellulose to Produce Fuel
Ethanol", 25: 3, 19-22 (2005)), steam explosion (Sun, X. F., et.
al., Carbohyd. Res., 340: 97-106 (2005); Josefsson, T., et. al.,
Holzforsch, 56: 3, 289-297(2002); Jain, R. K., et. al., CELL-041,
Book of Abstracts, 218.sup.th ACS National Meeting, New Orleans,
Aug. 22-26, 1999; and Wu, M. M., et. al., Appl. Biochem.
Biotechnol., 77-79 (1999)), ultrasound treatment (Yang, K., et al.,
Biotechnol. Prog., 20:1053 (2004)), and dissolution in ionic
liquids (Zhu, S., et al., Green Chem. 8: 325 (2006)). The use of
mixtures of electron-donor solvents with nitrogen oxides, lithium
chloride, triethylamine oxide, methylmorpholine oxide,
trifluoroacetic acid, orthphosphoric acid, and aqueous solutions of
zinc chloride for dissolving cellulose, has been reviewed (see
Grinshpan, D. D. B., "Novel Processes for Production and Processing
of Cellulose Solutions", Editor: Sviridov, B. B. Khimicheskie
Problemy Sozdaniya Novykh Materialov I Tekhnologii, 87, Belorusskii
Gosudarstvennyi Universitet, Minsk (1998)).
[0009] In addition to dissolution of cellulosic materials in some
of the aforementioned media, some chemical derivatization can and
probably does occur, as in the cases of trifluoroacetic and
orthphosphoric acids to form trifluoroacetate and phosphate esters,
respectively. Dissolving cellulose in an acid anhydride can lead to
regioselectively functionalized polymers (El Seoud, O. A., et. al.,
Adv. Polymer Sci., 186: 103 (2005)), and regioselective
esterification and etherification of glucose has been demonstrated
to influence the processing and use of these products (Burkart, P.,
et. al., Polym. News, 21: 155 (1996)). The synthesis of cellulose
sulfonates (e.g., tosylates and mesylates) provides polymers with
interesting properties as well as intermediates to new cellulosic
products (Siegmund, G., et. al., Polym. News, 27: 84 (2002)). Fatty
acid esters of cellulose lead to novel bioplastics and films (Song,
L., et. al., Gaofenzi Cailiao Kexue Yu Gongcheng, 18: 11 (2002);
and Satge, C., et. al., Comptes Rendus Chimie, 7:135 (2004)). Such
esters also open new synthetic possibilities for introducing
functional groups into cellulose providing pathways to cellulose
esters and ethers and their derivatives, as well as biologically
active molecules covalently bound to cellulose (Bojanic, V., et.
al., Hemisjska Industrija, 52:191(1998)). The reaction kinetics of
the production of cellulose ethers (e.g., methyl,
hydroxyethylmethyl and hydroxyethyl) have also been reviewed (see
Doenges, R., Brit. Polym. J., 23: 315-26 (1991).
[0010] As a percentage of the approximately 89% dry matter in
Distillers Dry Grains and Solubles (DDGS) obtained from Big River
Resources, LLC, Burlington, Iowa, cellulose and starch
(polyglucoses) comprise ca 16 and 5%, respectively, and the
hemicelluloses (polypentoses) xylan, and arabinan comprise a total
of about 13.5%.
[0011] None of these polysaccharides have appreciable solubility in
water, and so it is desirable to develop reasonably mild methods
for degrading and/or derivatizing these materials in such a way as
to solubilize them in water, since water is the solvent of choice
for the commercial production of ethanol by enzymatic means. Thus,
water solubilization of these polysaccharides and
heteropolysaccharides facilitate access to them by cellulases and
fermentation enzymes. A recent review (Mosier, N., et. al., Biores.
Technol., 96(6): 673-686 (2005)) describes desired traits in a
pretreatment, including its effect on biomass surface area,
cellulose crystallinity, and hemicellulose and lignin
processability. A review of current pretreatment technologies is
also given (Mosier, N. S., et. al., Appl. Biochem. &
Biotechnol., 125: 77-85 (2005)). A coordinated effort to develop
leading pretreatment technologies was also reported (Wyman C. E.,
et al., Biores. Technol., 96: 1959-1966 (2005)).
[0012] Phosphitylation has been developed in recent years as a
technique for derivatizing carbohydrates, nucleosides, and
nucleotides (Dabkowski, W., Chem. Nucl. Acid Comp.: Collect. Symp.
Series, 7: 39-46 (2005); Dabkowski, W., et. al., N. J. Chem., 29:
11 (2005); Laneman, Scott A., Spec. Chem. Mag., 25(1): 30-32
(2005); Ahmadibeni, Y., et. al., J. Org. Chem., 70(3): 1100-1103
(2005); Oka, N., et. al., J. Am. Chem. Soc., 125(27): 8307-8317
(2003); and Parang, K., et. al., Org. Letters, 3(2): 307-309
(2001), although this technique has been known longer for simple
alcohols (Dabkowski, W., Chem. Nucl. Acid Comp.: Collect. Symp.
Series, 7: 39-46 (2005); Dabkowski, W., et. al., N.J. Chem., 29: 11
(2005); and Watanabe, Y., et. al., Tetrahed. Letters, 31(2): 255-6
(1990)).
[0013] The present invention is directed to overcoming these and
other deficiencies in the art.
SUMMARY OF THE INVENTION
[0014] One aspect of the present invention is directed toward a
method of solubilizing coal. The method includes providing coal and
providing an oxoacid ester of phosphorus or a mixture of an oxoacid
of phosphorus and an alcohol. A blend of the coal and the oxoacid
ester of phosphorus or the mixture of the oxoacid of phosphorus and
alcohol is formed. The blend is then treated under conditions
effective to solubilize the coal.
[0015] Another aspect is directed toward a method of solubilizing
coal. The method includes treating coal with a mixture of (i) water
and (ii) at least one member selected from the group consisting of
an oxoacid ester and a thioacid ester of phosphorous under
conditions effective to solubilize the coal.
[0016] Another aspect of the present invention is directed toward a
method of solubilizing coal. The method includes treating coal with
at least one of an oxoacid ester of phosphorus, a mixture of an
oxoacid of phosphorus and an alcohol, or a thioacid ester of
phosphorus or a mixture of an thioacid of phosphorus and an alcohol
under conditions effective to solubilize at least a portion of the
coal.
[0017] Yet another aspect of the present invention is directed
toward a composition comprising solubilized organophosphorus ester
derivatives of coal.
[0018] A further aspect of the present invention is directed toward
a bioconversion method. The method includes providing the
composition as described above and providing a bioconversion agent.
The composition is treated with the bioconversion agent under
conditions effective to bioconvert the composition.
[0019] The solubilizing solvent system of the present invention
could be injected into the coal bed, thus avoiding conventional
mining costs. For example, in a process for bioconverting coal by
bacterial bioconversion, partially "etching" away the coal surfaces
in coal bed cracks would expose relatively huge coal surface areas
for methanogenic bacteria to multiply, thereby considerably raising
the volume of bioconversion per unit time.
[0020] Relatively deep coal mines can have temperatures near the
boiling point of water. The solvent systems of the present
invention would be very compatible with such temperatures, since
the solubilizing agent operates well at elevated temperatures.
DETAILED DESCRIPTION OF THE INVENTION
[0021] One aspect of the present invention is directed toward a
method of solubilizing coal. The method includes providing coal and
providing an oxoacid ester of phosphorus or a mixture of an oxoacid
of phosphorus and an alcohol. A blend of the coal and the oxoacid
ester of phosphorus or the mixture of the oxoacid of phosphorus and
alcohol is formed. The blend is then treated under conditions
effective to solubilize the coal.
[0022] In certain embodiments, the oxoacid ester of phosphorus is
provided. In some embodiments, the mixture of the oxoacid of
phosphorus and the alcohol is provided. The coal may be fully
solubilized or may be partially solubilized as a result of the
treating.
[0023] The coal may be lignite or any form or rank of coal, ranging
from brown coal to anthracite.
[0024] The treating step may be carried out at a temperature of 0
to 200.degree. C., preferably at a temperature of 80 to 100.degree.
C.
[0025] The treating step may be carried out at any pH, preferably
in the range of 6 to 9. The treating step may be carried out at any
pressure ranging from with a vacuum to greater than 5,000 psig.
[0026] The oxoacid ester of phosphorus may be an ester of
phosphorous acid, phosphoric acid, hypophosphorous acid,
polyphosphoric acid, or mixtures thereof.
[0027] The oxoacid of phosphorus may be phosphorous acid,
phosphoric acid, hypophosphorous acid, polyphosphoric acid, or
mixtures thereof.
[0028] Suitable alcohols include methanol, ethanol, ethylene
glycol, propylene glycol, glycerol, pentaerythritol, trimethylol
ethane, trimethylol propane, trimethylol alkane, benzyl alcohol,
resorcinol, phenol, catechol, alkanol, polyol, or mixtures thereof.
In a preferred embodiment the ester is a mono-acid and/or di-ester
of an acid of phosphorous.
[0029] The blend may have any ratio of the oxoacid of phosphorus to
the alcohol. Preferably, the ratio of the oxoacid of phosphorus to
the alcohol is from 10:1 to 1:10.
[0030] The methods of the present invention can include regulating
the water content of the blend before or during treating.
Regulation of the water content can be carried out by removing
water. Suitable techniques for doing so include molecular sieving,
distillation, or adding a dehydrating agent to the blend.
[0031] The methods of the present invention may also include
sonicating the blend during or after the treating. The methods of
the present invention may also include adding a bioconversion agent
to the blend after treating. Suitable bioconversion agents include
methanogens.
[0032] Another aspect is directed toward a method of solubilizing
coal. The method includes treating coal with a mixture of (i) water
and (ii) at least one member selected from the group consisting of
an oxoacid ester and a thioacid ester of phosphorous under
conditions effective to solubilize the coal.
[0033] The oxoacid or thioacid ester of phosphorous may be formed
in situ from a mixture of the appropriate acid and alcohol, i.e.,
alcohol and acid in the appropriate amounts are added to water to
produce the ester and used for the treatment.
[0034] In certain embodiments the member is an oxoacid ester of
phosphorus. In some embodiments the mixture includes an oxoacid of
phosphorus and an alcohol.
[0035] The method of the present invention can include sonicating
the mixture during or after said treating. The method of the
present invention can also include bioconverting solubilized
coal.
[0036] In certain embodiments, the bioconverting is effected with a
bioconversion agent. The bioconversion agent can be a
methanogen.
[0037] Another aspect of the present invention is directed toward a
method of solubilizing coal. The method includes treating coal with
at least one of an oxoacid ester of phosphorus, a mixture of an
oxoacid of phosphorus and an alcohol, or a thioacid ester of
phosphorus or a mixture of an thioacid of phosphorus and an alcohol
under conditions effective to solubilize at least a portion of the
coal.
[0038] In certain embodiments, the coal is treated with an oxoacid
ester of phosphorus. In certain embodiments, the oxoacid ester of
phosphorous is formed by mixing an oxoacid of phosphorus and an
alcohol.
[0039] In certain embodiments, the coal is partially or fully
solubilized as a result of the treating.
[0040] In certain embodiments, the coal is selected from the group
consisting of lignite, brown coal, sub-bituminous coal, bituminous
coal, anthracite, and combinations thereof.
[0041] In certain embodiments, the treating is carried out at a
temperature of 0 to 200.degree. C. In a preferred embodiment, the
treating is carried out at a temperature of 80 to 100.degree.
C.
[0042] In certain embodiments, the treating is carried out at a pH
range of 6 to 9.
[0043] In certain embodiments, the oxoacid ester of phosphorus is
selected from the group consisting of esters of phosphorous acid,
phosphoric acid, hypophosphorous acid, polyphosphoric acid, and
mixtures thereof. In certain embodiments, the oxoacid of phosphorus
is selected from the group consisting of phosphorous acid,
phosphoric acid, hypophosphorous acid, polyphosphoric acid, and
mixtures thereof. In certain embodiments, the alcohol is selected
from the group consisting of methanol, ethanol, ethylene glycol,
propylene glycol, glycerol, pentaerythritol, trimethylol ethane,
trimethylol propane, trimethylol alkane, alkanol, polyol, and
mixtures thereof.
[0044] In certain embodiments, the mixing has a ratio of the
oxoacid of phosphorus to the alcohol of from 10:1 to 1:10. In
certain embodiments, the methods include regulating the water
content of the blend before or during said treating. In a preferred
embodiment, the regulating of the water content comprises removing
water. The water may be removed, for example, by molecular sieving,
distillation, or addition of a dehydrating agent.
[0045] In certain embodiments, the methods include sonicating the
blend during or after said treating.
[0046] In certain embodiments, the methods include treating the
coal with a bioconversion agent. The bioconversion agent may be a
methanogen.
[0047] Certain embodiments of the invention are treated product
produced by of the methods described herein. Certain embodiments
provide a composition comprising solubilized organophosphorus ester
derivatives of coal.
[0048] In certain embodiments, the coal is present in a
subterranean coal deposit.
[0049] In certain embodiments, the treated coal in the coal deposit
is bioconverted with a bioconverting agent. The bioconversion agent
is a consortium of bacteria, the consortium may include
methanogens.
[0050] In certain embodiments, an aqueous solution containing at
least one oxoacid ester of phosphorous is introduced into the coal
bed. In certain embodiments, the oxoacid ester of phosphorus is
produced in the solution from the corresponding oxoacid of
phosphorus and the corresponding alcohol. The solution may contain
a phosphite ester. The phosphite ester may be a diester or a
monoester. In certain embodiments, the solution contains a
phosphite monoester and a phosphite diester.
[0051] Yet another aspect of the present invention is directed
toward a composition comprising solubilized organophosphorus ester
derivatives of coal.
[0052] A further aspect of the present invention is directed toward
a bioconversion method. The method includes providing the
composition as described above and providing a bioconversion agent.
The composition is treated with the bioconversion agent under
conditions effective to bioconvert the composition to hydrocarbons
and carbon dioxide. Useful bioconversion agents include
methanogens. Suitable bioconversion includes formation of
hydrocarbons such as methane, ethane, propane, and others, as well
as carbon dioxide.
[0053] A further aspect of the present invention is directed toward
solubilizing the coal as part of a process for bioconverting coal.
Suitable bioconversion includes formation of hydrocarbons such as
methane, ethane, propane, and others, as well as carbon dioxide.
Suitable bioconversion includes formation of hydrocarbons such as
methane, ethane, propane, and others, as well as carbon
dioxide.
[0054] In one aspect, as known in the art, coal may be bioconverted
by an appropriate consortium of bacteria that includes for example,
methanogens and acetogens. Such consortium may be inherently
present in the coal deposit and/or may be added to the coal seam.
In addition, appropriate nutrients may be provided to the coal seam
to promote the growth the bacteria present and/or added to the
coal.
[0055] Thus, in accordance with an aspect of the invention, the
solubilization solvent used in the invention is injected into a
coal bed as part of the overall procedure for bioconverting
coal.
[0056] The method of the present invention is useful in treating
coal which renders the water-soluble product suitable, for example,
for further processing such as bioconversion including formation of
methane.
[0057] As used herein, coal refers to any of the series of
carbonaceous fuels ranging from lignite to anthracite. The members
of the series differ from each other in the relative amounts of
moisture, volatile matter, and fixed carbon they contain. Of the
coals, those containing the largest amounts of fixed carbon and the
smallest amounts of moisture and volatile matter are the most
useful to humans. The lowest in carbon content, lignite or brown
coal, is followed in ascending order by subbituminous coal or black
lignite (a slightly higher grade than lignite), bituminous coal,
semibituminous (a high-grade bituminous coal), semianthracite (a
low-grade anthracite), and anthracite.
[0058] While not wishing to be bound by theory, transesterification
can be driven by the release of a more volatile alcohol as in
reaction 1 (below), where R is larger than an ethyl group. However,
it has been observed that phosphite esters are also capable of
dissolving coal to varying degrees (depending on the source) via
conversion of at least some of the hydroxyl groups to phosphite
ester groups in a phosphitylation reaction (e.g., reaction 2,
below).
##STR00001##
##STR00002##
[0059] There are two independent variables at work in the
technology, namely, coal solubility and the degree of CO--H bond
cleavage in the coal matrix. The first depends in large measure on
how well the phosphite ester system cleaves the relatively weak van
der Waals interactions and London forces operating to bind carbon
layers together, and the second depends on how well the phosphite
ester system cleaves CO--H chemical bonds for better methanogenic
bacterial access. The harsher conditions proposed will be generated
by employing high-power sonication, a technique increasingly used
in industry.
[0060] It is well known that hydrolysis equilibria are reversible
for many chemicals. Phosphite esters are no exceptions (see Scheme
1 for an example). Thus, this process can proceed from left to
right in each equilibrium step starting with P(OEt).sub.3 and
water, or from right to left starting from phosphorous acid and
ethanol at the lower right of the Scheme. Starting with 3
equivalents of EtOH and an equivalent of phosphorous acid and then
removing the water (e.g., with molecular sieves) produces mainly
P(OEt).sub.3.
##STR00003##
[0061] It is possible to start with phosphorous acid and the
required alcohol to make a mixture of the first hydrolysis product
and the second hydrolysis product for use as the active
pretreatment medium or to start with the first hydrolysis product,
and by adding the correct amount of water, make the same mixture as
starting with phosphorous acid and the required alcohol.
[0062] It is generally possible to proceed in either direction of
an equilibrium or sequence of equilibria. This process is governed
by Le Chatelier's Principle.
[0063] It has been shown that the non-toxic first and second
hydrolysis products of the toxic bicyclic phosphite
P(OCH.sub.2).sub.3CEt are the active species for effectively
solubilizing lignins in a wide range of lignocellulosics (e.g.,
cellulose itself, corn stover, pine and poplar shavings, kenaf, and
Distillers Dry Grains and Solubles (DDGS, which comes from the dry
mill corn-to-ethanol process)).
[0064] The alcohols (see Table 1, below) from which A, (ethanol), B
(ethylene glycol), C (propylene glycol), and D
(2,2-dimethylpropylene-1,3-diol) are commercially inexpensive, are
manufactured in large volumes, and are of very considerable
industrial importance.
TABLE-US-00001 TABLE 1 H(O)P(OEt).sub.2 ##STR00004## ##STR00005##
##STR00006## A B C D EtOP(OEt).sub.2 ##STR00007## ##STR00008##
##STR00009## E F G H H(O)POH(OEt) ##STR00010## ##STR00011##
##STR00012## I J K L
[0065] In Schemes 2, 3, and 4 (below), the polyols from which N, R,
and V in these schemes are made are glycerol, trimethylol propane,
and pentaerythritol, respectively (see Table 1, above). These
polyols are very cheap and are made in large volumes (i.e. glycerol
is an overly abundant byproduct of the biodiesel industry,
trimethylol propane is used in polyurethane manufacture, and
pentaerythritol is made in over 100 million pound quantities per
year, most of which is used in alkyd resins and lubricants).
Although the parent bicyclic phosphite M in Scheme 2 is known, it
would not form in the proposed reaction of glycerol and phosphorous
acid, because of its strained bonds and the fact that its formation
would require the presence of a catalyst. A catalyst is also
required for the analogous formations of the toxic parent phosphite
Q in Scheme 3 and the non-toxic parent phosphite U shown in Scheme
4. It should be noted that neither first nor second hydrolysis
products for the phosphite esters in Schemes 2-4 are commercially
available nor are there reports of their isolation to date.
##STR00013##
##STR00014##
##STR00015##
[0066] Synthesis of parent phosphite esters for subsequent
hydrolysis (to make the desired ratio of first to second hydrolysis
products) requires expense, time and energy, which can be avoided
by starting with phosphorous acid and the desired alcohol, diol,
triol or tetraol, followed by removing the appropriate amount of
water. Note that the parent phosphite esters by themselves are
ineffective solubilizing agents. The mixture of active solubilizing
agents is created by proceeding from the final hydrolysis products
and working toward parent phosphites but not actually synthesizing
them.
[0067] The first hydrolysis products A-D of the parent phosphites
E-H, respectively, are effective solubilizing agents for coal.
Compounds A, B, and D are commercially available, but C can be
synthesized. It should be noted that A-D by themselves are also
effective in the presence of some water to make a mixture of first
and second hydrolysis products I-L.
[0068] One skilled in the art would recognize that thiophosphoryl
compounds, those bearing the P.dbd.S functionality, may be
substituted for related phosphoryl derivatives. Such substitution
of a sulfur for one or more oxygens in a phosphorous oxoacid,
oxoacid ester, a phosphoric oxoacid, or phosphoric acid ester would
be possible as thiophosphorous and thiophosphoric compounds are
well known. However, such sulfur containing compounds could be more
expensive and pose environmental problems.
[0069] In one aspect of the present invention, coal is treated with
an oxoacid or thioacid ester of phosphorous as part of a process
for bioconverting the coal to produce one or more hydrocarbons, and
in particular methane. Although the present invention is not
limited thereby, it is believed that such treatment results in a
more effective bioconversion as a result of (i) the breaking of
bonds in the coal matrix resulting in chemical breakdown of
portions of the coal and/or (ii) cleaving of bonds holding carbon
layers together. Thus, the solubilization of the coal may involve
one or more of a chemical break-down of the coal and/or cleaving of
coal bonds. The coal that is treated and bioconverted may be part
of a subterranean deposit, in which case, a solution containing the
oxoacid and/or thioacid ester of phosphorus is introduced into such
deposit through a suitable well. The bacterial consortia used in
the bioconversion may be present in such deposit and/or added to
the deposit. As previously indicated, the ester used in the
treatment may be produced in the solution from the corresponding
alcohol and acid.
EXAMPLES
Example 1
Solubility of Lignite in P(OCH.sub.2).sub.3CEt
[0070] Lignite was mixed in a solution of
P(OCH.sub.2).sub.3CEt/water and reacted at 150 deg C. The sample
was found to be 66% soluble in P(OCH.sub.2).sub.3CEt/water compared
to a similar sample that was found to be only 12% soluble in
pyridine.
[0071] Although preferred embodiments have been depicted and
described in detail herein, it will be apparent to those skilled in
the relevant art that various modifications, additions,
substitutions, and the like can be made without departing from the
spirit of the invention and these are therefore considered to be
within the scope of the invention as defined in the claims which
follow.
* * * * *