U.S. patent application number 11/560960 was filed with the patent office on 2007-06-28 for process for the direct production of methanol from methane.
Invention is credited to Timothy A. Brandvold, Joseph A. Kocal.
Application Number | 20070149833 11/560960 |
Document ID | / |
Family ID | 38189147 |
Filed Date | 2007-06-28 |
United States Patent
Application |
20070149833 |
Kind Code |
A1 |
Brandvold; Timothy A. ; et
al. |
June 28, 2007 |
PROCESS FOR THE DIRECT PRODUCTION OF METHANOL FROM METHANE
Abstract
A process for the production of methanol from methane has been
developed. The process involves reacting methane with an oxidant
such as oxygen or a peroxide in the presence of a catalyst and a
solvent in a reaction zone to produce an effluent stream comprising
a methanol product. The effluent stream is next separated into a
gaseous stream comprising unreacted methane and carbon dioxide and
a liquid stream comprising the methanol product and solvent. Next
the gaseous stream is further separated to provide a methane stream
which is recycled to the reaction zone. Finally, a methanol stream
is isolated and a solvent stream is recycled to the reaction
zone.
Inventors: |
Brandvold; Timothy A.;
(Arlington Heights, IL) ; Kocal; Joseph A.;
(Glenview, IL) |
Correspondence
Address: |
HONEYWELL INTELLECTUAL PROPERTY INC;PATENT SERVICES
101 COLUMBIA DRIVE, P O BOX 2245 MAIL STOP AB/2B
MORRISTOWN
NJ
07962
US
|
Family ID: |
38189147 |
Appl. No.: |
11/560960 |
Filed: |
November 17, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60753205 |
Dec 22, 2005 |
|
|
|
Current U.S.
Class: |
568/910 |
Current CPC
Class: |
C07C 29/095 20130101;
C07C 67/035 20130101; C07C 29/80 20130101; C07C 29/48 20130101;
C07C 67/035 20130101; C07C 69/63 20130101; C07C 29/48 20130101;
C07C 31/04 20130101; C07C 29/095 20130101; C07C 31/04 20130101;
C07C 29/80 20130101; C07C 31/04 20130101 |
Class at
Publication: |
568/910 |
International
Class: |
C07C 29/03 20060101
C07C029/03 |
Claims
1. A process for converting methane to methanol comprising: a)
flowing a methane and an oxidant stream to a methane oxidation
reactor and contacting the methane and oxidant with a catalyst and
a solvent at oxidation conditions to provide an effluent stream
comprising methanol or a methanol adduct; b) flowing the effluent
stream to a separation zone operated at conditions to provide an
overhead gaseous stream comprising methane and carbon dioxide and a
bottom stream comprising methanol or a methanol adduct, solvent and
byproducts; c) flowing the bottom stream to a second separation
zone operated at conditions to provide a purified product stream
comprising methanol, and a solvent stream which is recycled to the
oxidation reactor; and d) flowing the overhead gaseous stream to a
third separation zone operated at conditions to provide a methane
stream which is recycled back to the oxidation reactor and a waste
stream comprising carbon dioxide.
2. The process of claim 1 where the catalyst is a heterogeneous
catalyst.
3. The process of claim 1 where the catalyst is a homogeneous
catalyst.
4. The process of claim 1 where the solvent is selected from the
group consisting of trifluoro-acetic acid, trifluoroacetic
anhydride, pentafluoro-proprionic acid, supercritical carbon
dioxide and mixtures thereof.
5. The process of claim 1 where the oxidation conditions comprise a
pressure of about 103 kPa (15 psi) to about 6,895 kPa (1,000 psi),
a temperature of about 25.degree. C. to about 250.degree. C. and a
contact time of about 30 minutes to about 30 hours.
6. The process of claim 1 where prior to step (c), the bottom
stream is flowed to a hydrolysis zone operated at hydrolysis
conditions thereby hydrolyzing at least a portion of the methanol
adduct to methanol and regenerated solvent.
7. The process of claim 6 where the hydrolysis conditions comprise
a temperature of about 20.degree. C. to about 200.degree. C. and a
pressure of about 103 kPa to about 1030 kPa.
8. The process of claim 1 where the methane and oxidant streams are
first mixed and then flowed to the oxidation reactor.
9. The process of claim 3 where the homogeneous catalyst comprises
a compound dissolved in a solvent, the compound having an empirical
formula of M.sub.xX.sub.m where M is selected from the group
consisting of palladium, copper, manganese, mercury, silver,
cobalt, vanadium, platinum, lead, gold, niobium chromium,
molybdenum, tungsten, cerium and mixtures thereof and X is an anion
selected from the group consisting of acetate, trifluoroacetate,
sulfate, carbonate, halide, nitrate, perchlorate, propionate,
pentafluoropropionate, acetylacetonate, hexafluoroacetylacetonate,
"m" is the oxidation state of M, and "x" is the anion valence of
X.
10. The process of claim 2 where the catalyst is an oxide of a
metal selected from the group consisting of manganese, cobalt,
palladium, molybdenum, chromium, vanadium, copper and mixtures
thereof.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from Provisional
Application Ser. No. 60/753,205 filed Dec. 22, 2005, the contents
of which are hereby incorporated by reference in its entirety.
FIELD OF THE INVENTION
[0002] The invention relates to a process for converting methane to
methanol. The process involves either co-feeding or alternately
feeding methane and an oxidant to a reactor containing a catalyst
at oxidation conditions to convert the methane to methanol. The
effluent from this oxidation reactor is separated into a gaseous
stream comprising unreacted methane and a bottom stream comprising
methanol or a methanol adduct. The gaseous stream is further
separated to provide a methane stream which is recycled to the
reactor, while the bottom stream is separated into a methanol
stream and a solvent stream which is also recycled to the
reactor.
BACKGROUND OF THE INVENTION
[0003] Today, both chemical and energy industries rely on petroleum
as the principal source of carbon and energy. Methane is
underutilized as a chemical feedstock, despite being the primary
constituent of natural gas, an abundant carbon resource. Factors
limiting its use include the remote locations of known reserves,
its relatively high transportation costs and its thermodynamic and
kinetic stability. Methane's main industrial use is the production
of synthesis gas or syngas via steam reforming at high temperatures
and pressures. Syngas in turn can be converted to methanol also at
elevated temperatures and pressures. The production of methanol is
important because methanol can be used to produce important
chemicals such as olefins. The above two step process for the
production of methanol is expensive and energy intensive with
corresponding environmental impacts.
[0004] Selective oxidation of methane has been studied for over 30
years by individual, academic and government researchers with no
commercial success. The key challenges to a commercial direct
methane oxidation process are the inertness of methane relative to
intermediates and oxygenate products and designing a catalytic
process for direct gas phase reaction with high conversion and
selectivity. For example, Sen et al. in New J. Chem, 1989, 13,
755-760 disclose the use of Pd (O.sub.2C Me).sub.2 in
trifluoroacetic acid for the oxidation of methane to
CF.sub.3CO.sub.2Me. The reaction is carried out for 4 days at a
pressure of 5516-6895 kPa (800-1000 psi). E. D. Park et al. in
Catalysis Communications, Vol. 2 (2001), 187-190, disclose a Pd/C
plus Cu (CH.sub.3COO).sub.2 catalyst system for the selective
oxidation of methane using H.sub.2/O.sub.2. L. C. Kao et al. in J.
Am. Chem. Soc., 113 (1991), 700-701 disclose the use of palladium
compounds such as Pd (O.sub.2CC.sub.2H.sub.5).sub.2 to oxidize
methane to methanol in the presence of H.sub.2O.sub.2 and using
trifluoroacetic acid as the solvent. U.S. Pat. No. 5,585,515
discloses the use of catalysts such as Cu(I) ions in
trifluoroacetic acid to oxidize methane to methanol.
[0005] Applicants have developed a process which efficiently
produces a methanol stream from methane. Generally, the process
comprises reacting methane and an oxidant in the presence of a
catalyst at oxidation conditions. The resultant product mixture is
next processed to give a purified methanol stream and recycle
methane and solvent streams.
SUMMARY OF THE INVENTION
[0006] One embodiment of the invention is a process for converting
methane to methanol comprising: [0007] a) flowing a methane and an
oxidant stream to a methane oxidation reactor and contacting the
methane and oxidant with a catalyst and a solvent at oxidation
conditions to provide an effluent stream comprising methanol or a
methanol adduct; [0008] b) flowing the effluent stream to a
separation zone operated at conditions to provide an overhead
gaseous stream comprising methane and carbon dioxide and a bottom
stream comprising methanol or a methanol adduct, solvent and
byproducts; [0009] c) flowing the bottom stream to a second
separation zone operated at conditions to provide a purified
product stream comprising methanol, and a solvent stream which is
recycled to the oxidation reactor; and [0010] d) flowing the
overhead gaseous stream to a third separation zone operated at
conditions to provide a methane stream which is recycled back to
the oxidation reactor and a waste stream comprising carbon
dioxide.
[0011] This and other objects and embodiments will become clearer
after a detailed description of the invention.
BRIEF DESCRIPTION OF THE DRAWING
[0012] The FIGURE is a flow diagram showing one embodiment of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The present invention relates to the selective oxidation of
methane to methanol using a catalyst. The methane or feedstream can
either be a pure methane stream or can be diluted with an inert gas
such as nitrogen, helium, neon, argon, etc. Another element of the
invention is an oxidant which will react with the methane. The
oxidant can be oxygen, hydrogen peroxide or an organic
hydroperoxide. Non limiting examples of organic hydroperoxides
include tert-butyl hydroperoxide, cumene hydroperoxide, etc. It is
also within the scope of the invention that a blend of hydrocarbons
such as gasoline, straight run diesel, light cycle oil, vacuum gas
oil, fuel oil and crude oil can be oxidized to give a mixture of
organic hydroperoxides. One process for producing these
hydroperoxides is disclosed in U.S. Pat. No. 7,038,090 B1 which is
incorporated by reference in its entirety.
[0014] The oxidant stream and methane are now flowed into an
oxidation reactor or oxidation zone where they are reacted in the
presence of a catalyst to produce methanol. The oxidant and methane
streams can either be introduced into the oxidation zone in an
alternate arrangement or they can be combined into one stream and
than flowed into the oxidation zone. The oxidation zone will
contain a catalyst for promoting the oxidation of methane to
methanol and a solvent. The catalyst can either be a heterogeneous
catalyst or a catalytic metal compound which is dissolved in the
solvent, i.e. a homogeneous catalyst.
[0015] The metal compounds which can be used have an empirical
formula of M.sub.xX.sub.m where M is selected from the group
consisting of palladium, copper, manganese, mercury, silver,
cobalt, vanadium, platinum, lead, gold, niobium, chromium,
molybdenum, tungsten, cerium and mixtures thereof, X is an anion;
examples of which include but are not limited to acetate,
trifluoroacetate, sulfate, carbonate, halide, nitrate, perchlorate,
propionate, pentafluoropropionate, acetylacetonate, and
hexafluoroacetylacetonate, "m" is the oxidation state of M, and "x"
is the anion valence of X. The compounds described above are
readily available from commercial suppliers, can be prepared by
known methods or in certain cases can be prepared in situ by
dissolving the corresponding metal oxide in the reaction solvent.
For example, copper oxide can be dissolved in trifluoroacetic acid
to provide copper trifluoroacetate.
[0016] Another component of the invention is a solvent in which the
metal compounds described above are soluble. Non limiting examples
of solvents are trifluoroacetic acid, trifluoroacetic anhydride,
pentafluoropropionic acid, acetic acid, supercritical carbon
dioxide and mixtures thereof with trifluoroacetic acid being
preferred. The amount of compound which is added to the solvent can
vary widely, but is usually from about 0.01 weight % to about 2
weight % of M as the metal.
[0017] Non limiting examples of heterogeneous catalysts include the
oxides of metals such as manganese, cobalt, palladium, molybdenum,
chromium, vanadium and copper, and composite materials where one or
more of these oxides is supported on silica, alumina, zirconia,
magnesia, carbon, silicon carbide and other supports known in the
art. The catalyst may also include additional non-catalytically
active components which act as catalyst modifiers including but not
limited to lithium, sodium, potassium, tin, germanium, sulfur,
boron, chlorine. The heterogeneous catalyst can be present as a
fixed bed or can be used in a riser/regenerator reactor. In the
case of a homogeneous catalyst, the reactor can be a continuous
autoclave or the process can be carried out in a batch mode.
Regardless of what type of reactor is employed, the oxidation
conditions include a pressure of about 103 kPa (15 psi) to about
6,895 kPa (1,000 psi) and preferably from about 4,137 kPa (600 psi)
to about 6,895 kPa (1,000 psi). These pressures are sufficient to
ensure that the methane is dissolved in the liquid phase and the
reaction is a liquid phase reaction. Of course if the oxidant is
oxygen, it will be in the gas phase in the reactor. The reaction
temperature varies from about 25.degree. C. to about 250.degree. C.
and preferably from about 60.degree. C. to about 100.degree. C. The
contact time can vary considerably, but is usually from about 30
minutes to about 24 hours. The product mixture will contain either
methanol or a methyl ester formed from the methane and an adduct
from the solvent. Additional components of the product mixture will
include unreacted methane (the reaction is carried out with the
oxidant as the limiting reagent), CO.sub.2 (which results from the
degradation of the solvent) and higher molecular weight alcohols
which are byproducts from the organic hydroperoxide which may be
used as the oxidant.
[0018] The product stream or effluent stream from the oxidation
reactor or oxidation zone is now flowed to a separation zone which
is operated at conditions to provide an overhead gaseous stream and
a liquid bottom stream. The overhead stream will comprise methane
and carbon dioxide while the liquid bottom stream will comprise
methanol, solvent, water and byproducts. The separation conditions
in this separation zone include a temperature of about 50.degree.
C. to about 200.degree. C. and a pressure of about 103 kPa (15 psi)
to about 6895 kPa (1000 psi).
[0019] The liquid bottom stream is now flowed to a second
separation zone operated at conditions to provide a purified
methanol product stream, a solvent stream and a byproduct greater
than or equal to C2 alcohol stream. The second separation zone can
utilize any method known in the art including distillation and
adsorptive separation. For separation by distillation typical
conditions include a temperature of 20-240.degree. C., and a
pressure of 103 kPa (15 psi) to about 1030 kPa (150 psi). However,
if the liquid bottom stream contains methyl ester adducts, the
stream must first be passed to a hydrolysis zone where the methyl
ester is hydrolyzed to methanol and regenerate the solvent.
Hydrolysis conditions include a temperature of about 20.degree. C.
to about 200.degree. C. and a pressure of about 103 kPa (15 psi) to
about 1030 kPa (150 psi). A co-solvent and/or catalyst, well-known
in the art, may also be introduced to the reactor to facilitate
hydrolysis. Once the methyl ester adduct is hydrolyzed, it is now
flowed to the second separation zone and treated as described
above. The solvent stream is now recycled to the oxidation reactor,
but since there may have been degradation of the solvent, makeup
solvent may be added to this stream prior to introducing it back
into the oxidation reactor. The methane feedstream and the methane
recycle stream (as described below) can also be added to the
solvent stream which is than either directly flowed into the
oxidation reactor or combined with the oxidant stream and than
flowed into the oxidation reactor.
[0020] The overhead gaseous stream is now flowed to a third
separation zone which is operated at conditions to provide a
methane stream and a waste stream comprising carbon dioxide. The
methane stream is recycled back to the oxidation reactor by flowing
it into the recycle solvent stream.
[0021] Referring now to the FIGURE, methane or a methane/inert gas
stream is introduced via line 12 which may be combined with recycle
methane from line 26 and than in turn combined with the recycle
solvent stream 36 flowed into line 16 and into reactor 10. The
oxidant is flowed through line 14 into the valve connecting it with
line 36 containing solvent and methane which in turn is flowed into
line 16 and then into reactor 10. The valve joining lines 14 and 36
can be operated in such a way that both the methane solvent stream
and oxidant stream are joined together or the methane solvent
stream is first flowed into the reactor and then followed by the
oxidant stream with the two streams being alternately fed into
reactor 10. Reactor 10 contains either a heterogeneous catalyst
present as a catalyst bed or a homogeneous catalyst compound
dissolved in the solvent. If the catalyst is a homogeneous
catalyst, reactor 10 is charged with the homogeneous catalyst and
heated tip to operating temperature prior to flowing oxidant and
methane into the reactor. Once the methane and oxidant are
contacted for a sufficient time (as described above) in order to
convert the methane to methanol, the effluent or product mixture is
flowed out the reactor via line 18 and into reactor 20. Reactor 20
is a separation reactor or zone where the gaseous components of the
effluent stream are separated from the liquid components. The
gaseous components will comprise methane and carbon dioxide which
form an overhead gaseous stream which is removed via line 22. This
overhead gaseous stream is now flowed to a separation zone 30 which
separates methane from the carbon dioxide. The methane is removed
via line 26 and recycled to line 12 while the carbon dioxide is
vented via line 38.
[0022] If the product from reactor 10 comprises a methyl ester,
than the liquid bottom stream from reactor 20 is removed via line
24 and flowed into hydrolysis zone 40. Water is introduced, along
with any catalysts and co-solvents, to the hydrolysis zone via line
44. In the hydrolysis zone, the liquid bottom stream is hydrolyzed
to give methanol and regenerate the solvent. The effluent stream
from the hydrolysis zone is now flowed via line 28 into separation
zone 50. If methanol is the direct product from reactor 10, then
the liquid bottom feed from reactor 20 is flowed directly via line
24 and 28 into separation zone 50. In separation zone 50, a
purified methanol stream is separated and collected via line 32
while water, co-solvents from the hydrolysis zone, any higher
molecular weight alcohols and other liquid by-products are removed
via line 34 and the solvent is removed via line 36 and recycled
back to reactor 10. Since some solvent degradation occurs and thus
solvent is lost, additional solvent may need to be added via line
42.
[0023] While the invention has been described with what are
presently considered the preferred embodiments, it is to be
understood that the invention is not limited to the disclosed
embodiments, but it is intended to cover various modifications and
equivalent arrangements included within the scope of the appended
claims.
* * * * *