Umit OZKAN
Catalyst
http://www.chbmeng.ohio-state.edu/people/ozkan.html
Umit OZKAN
Contact: Umit Ozkan, (614) 292-6623; Ozkan.1@osu.edu
http://researchnews.osu.edu/archive/biohydro.htm
A BETTER WAY TO MAKE HYDROGEN FROM BIOFUELS
by Pam Frost Gorder
COLUMBUS, Ohio -- Researchers here have found a way to convert ethanol and other biofuels into hydrogen very efficiently.
A new catalyst makes hydrogen from ethanol with 90 percent yield, at a workable temperature, and using inexpensive ingredients.
Umit Ozkan, professor of chemical and biomolecular engineering
at Ohio State University, said that the new catalyst is much
less expensive than others being developed around the world,
because it does not contain precious metals, such as platinum or
rhodium.
Umit Ozkan
"Rhodium is used most often for this kind of catalyst, and it costs around $9,000 an ounce," Ozkan said. "Our catalyst costs around $9 a kilogram."
She and her co-workers presented the research Wednesday, August 20 at the American Chemical Society meeting in Philadelphia.
The Ohio State catalyst could help make the use of hydrogen-powered cars more practical in the future, she said.
"There are many practical issues that need to be resolved before we can use hydrogen as fuel -- how to make it, how to transport it, how to create the infrastructure for people to fill their cars with it," Ozkan explained.
"Our research lends itself to what's called a 'distributed production' strategy. Instead of making hydrogen from biofuel at a centralized facility and transporting it to gas stations, we could use our catalyst inside reactors that are actually located at the gas stations. So we wouldn't have to transport or store the hydrogen -- we could store the biofuel, and make hydrogen on the spot."
The catalyst is inexpensive to make and to use compared to others under investigation worldwide. Those others are often made from precious metals, or only work at very high temperatures.
"Precious metals have high catalytic activity and -- in most cases -- high stability, but they're also very expensive. So our goal from the outset was to come up with a precious-metal-free catalyst, one that was based on metals that are readily available and inexpensive, but still highly active and stable. So that sets us apart from most of the other groups in the world."
"Whenever a process works at a lower temperature, that brings energy savings and cost savings," Ozkan said. “Also, if the catalyst is highly active and can achieve high hydrogen yields, we don’t need as much of it. That will bring down the size of the reactor, and its cost”.
The new dark gray powder is made from tiny granules of cerium oxide -- a common ingredient in ceramics -- and calcium, covered with even smaller particles of cobalt. It produces hydrogen with 90 percent efficiency at 660 degrees Fahrenheit (around 350 degrees Celsius) -- a low temperature by industrial standards.
"Whenever a process works at a lower temperature, that brings energy savings and cost savings," Ozkan said. “Also, if the catalyst is highly active and can achieve high hydrogen yields, we don’t need as much of it. That will bring down the size of the reactor, and its cost”.
The process starts with a liquid biofuel such as ethanol, which is heated and pumped into a reactor, where the catalyst spurs a series of chemical reactions that ultimately convert the liquid to a hydrogen-rich gas.
One of the biggest challenges the researchers faced was how to prevent "coking" -- the formation of carbon fragments on the surface of the catalyst. The combination of metals -- cerium oxide and calcium -- solved that problem, because it promoted the movement of oxygen ions inside the catalyst. When exposed to enough oxygen, the carbon, like the biofuel, is converted into a gas and gets oxidized; it becomes carbon dioxide.
At the end of the process, waste gases such as carbon monoxide, carbon dioxide and methane are removed, and the hydrogen is purified. To make the process more energy-efficient, heat exchangers capture waste heat and put that energy back into the reactor. Methane recovered in the process can be used to supply part of the energy.
Though this work was based on converting ethanol, Ozkan's team is now studying how to use the same catalyst with other liquid biofuels. Her coauthors on this presentation included Ohio State doctoral students Hua Song and Lingzhi Zhang.
This research was funded by the Department of Energy.
http://www.technologynewsdaily.com/node/10180
Technology News ( 08/22/2008 )
Hydrogen From Biofuels
Researchers at Ohio State University have found a way to convert ethanol and other biofuels into hydrogen very efficiently. A new catalyst makes hydrogen from ethanol with 90 percent yield, at a workable temperature, and using inexpensive ingredients. Umit Ozkan, professor of chemical and biomolecular engineering at Ohio State University, said that the new catalyst is much less expensive...
Researchers at Ohio State University have found a way to convert ethanol and other biofuels into hydrogen very efficiently.
A new catalyst makes hydrogen from ethanol with 90 percent yield, at a workable temperature, and using inexpensive ingredients.
Umit Ozkan, professor of chemical and biomolecular engineering at Ohio State University, said that the new catalyst is much less expensive than others being developed around the world, because it does not contain precious metals, such as platinum or rhodium.
"Rhodium is used most often for this kind of catalyst, and it costs around $9,000 an ounce," Ozkan said. "Our catalyst costs around $9 a kilogram."
She and her co-workers presented the research Wednesday, August 20 at the American Chemical Society meeting in Philadelphia.
The Ohio State catalyst could help make the use of hydrogen-powered cars more practical in the future, she said.
"There are many practical issues that need to be resolved before we can use hydrogen as fuel -- how to make it, how to transport it, how to create the infrastructure for people to fill their cars with it," Ozkan explained.
"Our research lends itself to what's called a 'distributed production' strategy. Instead of making hydrogen from biofuel at a centralized facility and transporting it to gas stations, we could use our catalyst inside reactors that are actually located at the gas stations. So we wouldn't have to transport or store the hydrogen -- we could store the biofuel, and make hydrogen on the spot."
The catalyst is inexpensive to make and to use compared to others under investigation worldwide. Those others are often made from precious metals, or only work at very high temperatures.
"Precious metals have high catalytic activity and -- in most cases -- high stability, but they're also very expensive. So our goal from the outset was to come up with a precious-metal-free catalyst, one that was based on metals that are readily available and inexpensive, but still highly active and stable. So that sets us apart from most of the other groups in the world."
The new dark gray powder is made from tiny granules of cerium oxide -- a common ingredient in ceramics -- and calcium, covered with even smaller particles of cobalt. It produces hydrogen with 90 percent efficiency at 660 degrees Fahrenheit (around 350 degrees Celsius) -- a low temperature by industrial standards.
"Whenever a process works at a lower temperature, that brings energy savings and cost savings," Ozkan said. “Also, if the catalyst is highly active and can achieve high hydrogen yields, we don’t need as much of it. That will bring down the size of the reactor, and its cost”.
The process starts with a liquid biofuel such as ethanol, which is heated and pumped into a reactor, where the catalyst spurs a series of chemical reactions that ultimately convert the liquid to a hydrogen-rich gas.
One of the biggest challenges the researchers faced was how to prevent "coking" -- the formation of carbon fragments on the surface of the catalyst. The combination of metals -- cerium oxide and calcium -- solved that problem, because it promoted the movement of oxygen ions inside the catalyst. When exposed to enough oxygen, the carbon, like the biofuel, is converted into a gas and gets oxidized; it becomes carbon dioxide.
At the end of the process, waste gases such as carbon monoxide, carbon dioxide and methane are removed, and the hydrogen is purified. To make the process more energy-efficient, heat exchangers capture waste heat and put that energy back into the reactor. Methane recovered in the process can be used to supply part of the energy.
Though this work was based on converting ethanol, Ozkan's team is now studying how to use the same catalyst with other liquid biofuels. Her coauthors on this presentation included Ohio State doctoral students Hua Song and Lingzhi Zhang.
http://www.guardian.co.uk/environment/2008/aug/21/biofuels.travelandtransport ( Thursday August 21 2008 09:57 )
New Catalyst Boosts Hydrogen as Transport Fuel
http://domesticfuel.com/2008/08/24/turning-ethanol-into-hydrogen/
Turning Ethanol Into Hydrogen
http://www.thaindian.com/newsportal/south-asia/new-method-enables-conversion-of-biofuels-into-hydrogen-more-efficiently_10086918.html
Thaindian News ( 08/21/2008 )
New Method Enables Conversion of Biofuels into Hydrogen more Efficiently
http://www.greencarcongress.com/2008/08/new-low-cost-no.html
Green Car Congress ( 08/20/2008 )
New Low-Cost Non-noble Metal Catalyst for Hydrogen Production from Biofuels
http://thomasfortenberry.net/?p=3552 ( 08/20/2008 )
A Better Way to Make Biofuel Hydrogen
http://www.thehindu.com/seta/2008/08/21/stories/2008082150971600.htm ( 08/21/2008 )
Extracting More Hydrogen from Ethanol
http://feeds.bignewsnetwork.com/index.php?sid=397111
Big News Network.com ( 08/21/2008 )
New Method Enables Conversion of Biofuels into Hydrogen More Efficiently
http://www.theengineer.co.uk/Articles/Article.aspx?liArticleID=307647
The engineer ( 08/21/2008 )
Efficient Conversion
http://www.enn.com/sci-tech/article/37976
ENN ( 08/20/2008 )
A Better Way to Make Hydrogen from Biofuels
http://www.physorg.com/news138450335.html
Physorg ( 08/20/2008 )
A Better Way to Make Hydrogen from Biofuels
http://www.newswise.com/articles/view/543567/?sc=rssn
Newswise ( 08/20/2008 )
A Better Way to Make Hydrogen from Biofuels
http://www.sciencedaily.com/releases/2008/08/080820163111.htm
Science Daily ( 08/20/2008 )
A Better Way To Make Hydrogen From Biofuels
US Patent Application 20070110651
Ozkan; Umit S., et al.
( May 17, 2007 )
Multi-Stage Catalyst Systems and Uses Thereof
Abstract
Catalyst systems and methods provide benefits in reducing the content of nitrogen oxides in a gaseous stream containing nitric oxide (NO), hydrocarbons, carbon monoxide (CO), and oxygen (O.sub.2). The catalyst system comprises an oxidation catalyst comprising a first metal supported on a first inorganic oxide for catalyzing the oxidation of NO to nitrogen dioxide (NO.sub.2), and a reduction catalyst comprising a second metal supported on a second inorganic oxide for catalyzing the reduction of NO.sub.2 to nitrogen (N.sub.2).
Inventors: Ozkan; Umit S.; (Worthington, OH) ; Holmgreen; Erik M.; (Columbus, OH) ; Yung; Matthew M.; (Columbus, OH)
FIELD OF THE INVENTION
[0002] The present invention is generally directed to systems and methods of catalytic removal of pollutants in a gaseous stream, and is specifically directed to systems and methods of catalytic removal of pollutants via catalyst systems comprising oxidation and reduction catalysts.
BACKGROUND OF THE INVENTION
[0003] Nitrogen oxides (NO, NO.sub.2, N.sub.2O) contribute to several environmental hazards including global warming, smog, ground level ozone formation, and acid rain. Emission reduction is possible through modification of combustion parameters, but reducing NO.sub.x emissions to acceptable levels requires effective aftertreatment technologies. Current catalytic NO.sub.x reduction control technologies include three-way catalysts and ammonia-based selective catalytic reduction. While these methods are highly effective for current combustion technologies, they are unsuitable for the next generation of high efficiency lean-burn natural gas engines. Three-way catalysts are inactive in oxygen rich environments, while the large size and expense of ammonia SCR installations make them an impractical solution in a distributed energy context.
[0004] NO.sub.x, trap systems have received attention as a possible solution for lean NO.sub.x removal. These traps rely on bifunctional materials to store and reduce NO.sub.x under different engine cycles. Under lean conditions NO.sub.x is `trapped` on alkali metal oxides, and the engine is then periodically run under rich conditions to accomplish reduction over precious metals. These changes in engine operating conditions would necessitate additional engine controls. Additionally, current trap materials such as Ba and Pt are susceptible to sintering and SO.sub.2 poisoning.
[0005] The use of hydrocarbons as reducing agents in NO removal has attracted significant attention. The presence of hydrocarbons in current engine exhaust streams would make them a readily available and cost effective choice. However, hydrocarbon combustion, particularly in oxygen rich environments, may block NO reduction reactions.
[0006] As demands increase for methods of removing pollutants, the need arises for improved systems and methods of pollutant removal, especially systems operable to offset the hydrocarbon combustion in oxygen rich environments.
SUMMARY OF THE INVENTION
[0007] According to a first embodiment of the present invention, a catalyst system for reducing the content of nitrogen oxides in a gaseous stream containing nitric oxide (NO), hydrocarbons, carbon monoxide (CO), and oxygen (O.sub.2) is provided. The catalyst system comprises an oxidation catalyst comprising a first metal supported on a first inorganic oxide for catalyzing the oxidation of NO to nitrogen dioxide (NO.sub.2), and a reduction catalyst comprising a second metal supported on a second inorganic oxide for catalyzing the reduction of NO.sub.2 to nitrogen (N.sub.2).
[0008] According to a second embodiment of the present invention, a catalyst system for reducing the content of nitrogen oxides in a gaseous stream containing nitric oxide (NO), hydrocarbons, carbon monoxide (CO), and oxygen is provided. The catalyst system comprises an oxidation catalyst comprising cobalt on a zirconia support for catalyzing the oxidation of nitric oxide (NO) to nitrogen dioxide (NO.sub.2), and a reduction catalyst comprising palladium on a sulfated zirconia or tungstated zirconia support for catalyzing the reduction of NO.sub.2 to nitrogen (N.sub.2).
[0009] According to a third embodiment of the present invention, a method of reducing the level of pollutants in a gaseous stream is provided. The method comprises providing a catalyst system comprising an oxidation catalyst and a reduction catalyst, and feeding a gaseous stream comprising nitric oxide (NO), hydrocarbons, carbon monoxide (CO), and oxygen (O.sub.2) to the catalyst system. Additionally, the method comprises oxidizing the NO to nitrogen dioxide (NO.sub.2) in the presence of the oxidation catalyst, and reducing the NO.sub.2 to nitrogen (N.sub.2) by reacting with hydrocarbons in the presence of the reduction catalyst to form a treated gaseous stream.
[0010] Additional features and advantages provided by embodiments of the present invention will be more fully understood in view of the following detailed description.
DETAILED DESCRIPTION
[0011] In accordance with one embodiment of the present invention, a catalyst system for reducing the content of nitrogen oxides in a gaseous stream containing nitric oxide (NO), hydrocarbons, carbon monoxide (CO), and oxygen (O.sub.2) is provided. The catalyst system comprises an oxidation catalyst comprising a first metal supported on a first inorganic oxide for catalyzing the oxidation of NO to nitrogen dioxide (NO.sub.2). The oxidation catalyst may comprise any combination of metals with inorganic oxides, which are suitable to accelerate the reaction of NO with oxygen to produce NO.sub.2. The first metal may include, but is not limited to, cobalt, silver, or combinations thereof, and the first inorganic oxide may include, but is not limited to, titania, zirconia, alumina, or combinations thereof. In one exemplary embodiment, the oxidation catalyst may comprise cobalt on a zirconia support, wherein the oxidation catalyst comprises from about 1 to about 10% by weight of cobalt. The oxidation reaction may convert about 50% to about 90% by weight of the NO to NO.sub.2, and, in one embodiment, may produce a conversion of between about 70% to about 90% by weight. The temperature of the oxidation may vary based on the components of the gaseous stream and the catalysts. The oxidation generally occurs at a temperature of about 200 to about 500.degree. C. In a further embodiment, the above conversions may be achieved at a temperature of about 300.degree. C.
[0012] Furthermore, the catalyst system also comprises a reduction catalyst comprising a second metal supported on a second inorganic oxide for catalyzing the reduction of NO.sub.2 to nitrogen (N.sub.2). The reduction catalyst may comprise any combination of metals with inorganic oxides suitable to accelerate the reaction of NO.sub.2 with hydrocarbons in the gaseous stream to produce N.sub.2. In some embodiments, the second metal may comprise palladium, and the second inorganic oxide may comprise titania, zirconia, alumina, or combinations thereof. The palladium may comprise about 0.1 to about 0.5% by weight of cobalt; however, other amounts are contemplated depending on the catalytic requirements of the reduction reaction. In one exemplary embodiment, the reduction catalyst comprises palladium on a sulfated zirconia support. The reduction reaction may convert about 50% to about 80% by weight of the NO.sub.2 to N.sub.2, and, in a further embodiment, may produce a conversion of between about 60% to about 80% by weight.
[0013] The high degree of conversion in the reduction step is due, in large part, to the initial oxidation step. NO.sub.2 is more easily reduced than NO in a gaseous stream that includes both oxygen and hydrocarbons. For NO reduction, the combustion reaction of hydrocarbon in the presence of oxygen dominates over the reduction reaction of NO to N.sub.2. By oxidizing NO to NO.sub.2 and then reducing the NO.sub.2, the conversion to N.sub.2 is greatly enhanced, because the NO.sub.2 reduction reaction is not substantially blocked by the hydrocarbon combustion, which is the case for NO reduction.
[0014] In the gaseous stream, the hydrocarbons may comprise various compounds known to one skilled in the art. These hydrocarbon compounds may include, but are not limited to, methane, ethane, propane, or combinations thereof. The oxygen in the gaseous stream may be fed in excess to overcome any thermodynamic limitations of the oxidation reaction. In one embodiment, the gaseous stream may comprise about 2 to about 15% O.sub.2.
[0015] The catalyst system may comprise various configurations known to one skilled in the art. In one embodiment, the oxidation catalyst and the reduction catalyst are disposed on a catalyst bed. In a few exemplary embodiments, the catalyst bed may define a mixed bed, a monolith bed structure having oxidation and reduction catalysts embedded therein, or a bed comprising alternating layers or sections of oxidation and reduction catalysts. The catalysts can be combined in the system in several ways: physically mixing of catalyst powders, layering the catalyst powders, impregnating a single monolith support with both catalysts, or alternating sections of impregnated monolith support. The following catalyst production methods provide exemplary procedures for producing the oxidation and reduction catalysts of the present invention.
[0016] An oxidation catalyst comprised of cobalt supported on either titania or zirconia may be produced through incipient wetness or sol-gel techniques. The catalyst may contain between 1% and 10% cobalt by weight. The incipient wetness catalyst is prepared by first calcining the support (titania or zirconia) at 500.degree. C. for 3 hours. Cobalt is then added to the support by the addition of a cobalt nitrate in water or ethanol solution, in amount equal to the pore volume of the support. The sample is then dried at 100.degree. C. overnight. After drying the catalyst sample is calcined in air at temperatures between 300-600.degree. C. for 3 hours. Based on final desired weight loading of cobalt several additions of cobalt nitrate solution may be used. The catalyst can be prepared either by drying, or by calcining the catalysts between cobalt nitrate solution additions. The sol-gel prepared catalysts are synthesized in a single step. A solution of titanium isopropoxide or zirconia propoxide (depending on the desired support material) in isopropyl alcohol is hydrolyzed with a solution of cobalt nitrate in water. The water is added under stirring, and once complete the resulting gel is dried in air overnight and then calcined at between 300-600.degree. C. for 3 hours in air.
[0017] In producing the reduction catalyst comprising palladium supported on a sulfated zirconia support, the sulfated zirconia support is first prepared by pore volume addition of ammonium sulfate in water solution to a zirconia support. After the addition step, the treated support is dried at 100.degree. C. overnight, then calcined in air at 500.degree. C. for 3 hours. Palladium is added through pore volume additions of a palladium chloride and water solution. Small amounts of hydrochloric acid may be used to dissolve the palladium chloride. After adding the palladium chloride solution, the catalyst sample is dried at 100.degree. C. overnight and then calcined in oxygen at 500.degree. C. for 3 hours.
[0018] In addition to the removal of nitrogen oxides (NO.sub.x), the catalyst system may also be operable to oxidize carbon monoxide and/or hydrocarbons. In one embodiment, the CO in the gaseous stream may be oxidized to carbon dioxide (CO.sub.2) in the presence of the oxidation catalyst. In yet another embodiment, the catalyst system may also be operable to oxidize the hydrocarbons in the gaseous stream in the presence of the oxidation catalyst. Oxidizing the hydrocarbons may reduce the amount of unoxidized hydrocarbons, which may enhance the reduction of NO.sub.2 to N.sub.2. Thus, in a further embodiment, the catalyst system may comprise an additional oxidation catalyst, e.g. oxidation catalyst bed, to oxidize unreacted hydrocarbons after the reduction step. In an exemplary embodiment, a hydrocarbon feed comprising 85% methane/10% ethane/5% propane may be oxidized in the presence of an oxidation catalyst, wherein the ethane and propane are substantially oxidized at a temperature of about 275 to about 325.degree. C. and the methane is substantially oxidized at a temperature of about 425 to about 450.degree. C.
[0019] The present invention has numerous applications for pollutant removal from gaseous streams. In one embodiment, the catalyst system may be incorporated in a lean exhaust pollutant removal system. The lean exhaust removal system, which is applicable for lean burn engines, e.g. natural gas fuel engines, comprises an exhaust outlet in communication with the catalyst system and configured to deliver the gaseous stream to the catalyst system. To minimize costs, the lean exhaust removal system eliminates the need for the injection of additional hydrocarbon reducing agent in the reduction of NO.sub.2. The system relies on the unburned hydrocarbon fuel remaining in exhaust. The lean exhaust removal system, as described herein, may also be applied to other devices, such as diesel engines and advanced gas reciprocating engines.
[0020] It is noted that terms like "preferably," "generally", "commonly," and "typically" are not utilized herein to limit the scope of the claimed invention or to imply that certain features are critical, essential, or even important to the structure or function of the claimed invention. Rather, these terms are merely intended to highlight alternative or additional features that may or may not be utilized in a particular embodiment of the present invention.
[0021] For the purposes of describing and defining the present invention it is noted that the term "substantially" is utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. The term "substantially" is also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.
[0022] Having described the invention in detail and by reference to specific embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims. More specifically, although some aspects of the present invention are identified herein as preferred or particularly advantageous, it is contemplated that the present invention is not necessarily limited to these preferred aspects of the invention.
Novel Catalyst Systems and Uses Thereof
Abstract
A method of carbon monoxide (CO) removal comprises providing an oxidation catalyst comprising cobalt supported on an inorganic oxide. The method further comprises feeding a gaseous stream comprising CO, and oxygen (O.sub.2) to the catalyst system, and removing CO from the gaseous stream by oxidizing the CO to carbon dioxide (CO.sub.2) in the presence of the oxidation catalyst at a temperature between about 20 to about 200.degree. C.
Inventors: Ozkan; Umit S.; (Worthington, OH) ; Holmgreen;
Erik M.; (Columbus, OH) ; Yung; Matthew M.; (Columbus, OH)
Correspondence Name and Address:
DINSMORE & SHOHL LLP
ONE DAYTON CENTRE, ONE SOUTH MAIN STREET SUITE
1300 DAYTON OH 45402-2023 US
U.S. Current Class: 423/247
U.S. Class at Publication: 423/247
Intern'l Class: B01D 53/62 20060101 B01D053/62
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional Application Ser. No. 60/674,992 filed on Apr. 26, 2005, and incorporates the application in its entirety.
FIELD OF THE INVENTION
[0002] The present invention is generally directed to systems and methods of catalytic removal of pollutants in a gaseous stream, and is specifically directed to systems and methods of catalytic removal of pollutants at low temperatures.
BACKGROUND OF THE INVENTION
[0003] Air pollution continues to be a serious global problem. The present industrial plants and automobiles burn fossil fuels and emit a staggering amount of gaseous pollutants, principally unburned or partially burned fossil fuels, carbon monoxide, nitrogen oxides, and sulfur dioxide. Thus, there is a high demand for air purification methods, which remove these pollutants, such as carbon monoxide.
[0004] Numerous technologies have been developed; however, many of these technologies are costly and/or inefficient. As a result, there is a continuing desire to develop systems and methods to effectively remove carbon monoxide from gaseous streams at minimal cost.
SUMMARY OF THE INVENTION
[0005] In a first embodiment of the present invention, a method of carbon monoxide (CO) removal is provided. The method comprises providing an oxidation catalyst comprising cobalt supported on an inorganic oxide. The method further comprises feeding a gaseous stream comprising CO, and oxygen (O.sub.2) to the catalyst system, and removing CO from the gaseous stream by oxidizing the CO to carbon dioxide (CO.sub.2) in the presence of the oxidation catalyst at a temperature between about 20 to about 200.degree. C.
[0006] In a second embodiment of the present invention, another method of CO removal is provided. The method comprises providing an oxidation catalyst comprising cobalt on a titania or a zirconia support, feeding a gaseous stream comprising carbon monoxide (CO), and oxygen (O.sub.2) to the catalyst system, and oxidizing the CO to carbon dioxide (CO.sub.2) in the presence of the oxidation catalyst at a temperature between about 100 to about 200.degree. C.
[0007] Additional features and advantages provided by embodiments of the present invention will be more fully understood in view of the following detailed description.
DETAILED DESCRIPTION
[0008] In accordance with one embodiment of the present invention, a method of carbon monoxide (CO) removal is provided. The method comprises providing an oxidation catalyst comprising cobalt supported on an inorganic oxide. The inorganic oxide, when used in combination with the cobalt, may comprise any material effective at oxidizing CO to carbon dioxide (CO.sub.2). The inorganic oxide may include, but is not limited to, titania, zirconia, or combinations thereof. In one embodiment, the catalyst comprises from about 1 to about 10% by weight of cobalt.
[0009] The method further comprises feeding a gaseous stream comprising CO, and oxygen (O.sub.2) to the catalyst system. The gaseous stream may comprise up to about 3% CO, or in a further embodiment, from about 600 ppm to about 3% CO. The gaseous stream may comprise less than about 10% H.sub.2O, or in a further embodiment, less than about 2% H.sub.2O. In one embodiment, the gaseous stream may comprise up to about 15% O.sub.2, or in a further embodiment, about 2% to about 10% O.sub.2.
[0010] The method then includes removing CO from the gaseous stream by oxidizing the CO to CO.sub.2 in the presence of the oxidation catalyst at a temperature between about 20 to about 200.degree. C. In a further embodiment, the temperature ranges from between about 100 to about 200.degree. C. It is further contemplated to conduct the oxidation at higher temperatures, for example, up to about 500.degree. C. At temperatures above 100.degree. C., there is less likelihood of catalyst deactivation. In one embodiment, the oxidation of CO to CO.sub.2 defines a conversion of about 90% to substantially about 100%. In a further embodiment, the conversion of CO to CO.sub.2 is maximized at temperatures between about 100 to about 200.degree. C.
[0011] Oxidizing the CO at low temperatures, for example, at room temperature, benefits the system. For instance, minimizing the temperature may minimize the heating and/or electric costs required. Moreover, at temperatures below 200.degree. C., the combustion of hydrocarbons present in the gaseous stream is minimal, and thus does not affect the reaction kinetics of other reactions, for example, the CO oxidation.
[0012] The catalyst system may comprise various configurations known to one skilled in the art. In one embodiment, the oxidation catalyst may be disposed on a catalyst bed. In some exemplary embodiments, the catalyst bed may define a powder bed, or a monolith bed structure having the cobalt embedded in the inorganic oxide support. The catalyst can be combined in the system in several ways: producing a bed of powdered catalyst, or impregnating a single monolith support with the oxidation catalyst. The following catalyst production methods provide exemplary procedures for producing the oxidation catalyst of the present invention.
[0013] An oxidation catalyst comprised of cobalt supported on either titania or zirconia may be produced through incipient wetness or sol-gel techniques. The catalyst can contain between 1% and 10% cobalt by weight. The incipient wetness catalyst is prepared by first calcining the support (titania or zirconia) at 500.degree. C. for 3 hours. Cobalt is then added to the support by the addition of a cobalt nitrate in water solution, in amount equal to the pore volume of the support. The sample is then dried at 100.degree. C. overnight. After drying, the catalyst sample is calcined in air at temperatures between 300-600.degree. C. for 3 hours. Based on the final desired weight of cobalt, several additions of cobalt nitrate solution may be used. The catalyst can be prepared either by drying, or by calcining the catalysts between cobalt nitrate solution additions. The sol-gel prepared catalysts are synthesized in a single step. A solution of titanium isopropoxide or zirconia propoxide (depending on the desired support material) in isopropyl alcohol is hydrolyzed with a solution of cobalt nitrate in water or ethanol. The water is added under stirring, and once complete the resulting gel is dried in air overnight and then calcined at between 300-600.degree. C. for 3 hours in air.
[0014] The method has numerous pollutant removal applications, for example, in respiratory and environmental pollution control processes. The method may be applicable for use in sealed environments, for example, a submarine or a spacecraft. In addition, these catalysts could be used for gas purification in closed-cycle CO.sub.2 lasers, and CO gas sensors. Furthermore, the method may be applicable for selectively oxidizing CO in steam reforming reactions, and for fuel cell applications in which CO must be removed from the gas feed to prevent poisoning of the electrodes. This method can also be used to remove CO from indoor air, which would help to prevent bodily harm/death from carbon monoxide poisoning. Furthermore, it can be used to purify exhaust gases from combustion processes.
[0015] It is noted that terms like "preferably," "generally," "commonly," and "typically" are not utilized herein to limit the scope of the claimed invention or to imply that certain features are critical, essential, or even important to the structure or function of the claimed invention. Rather, these terms are merely intended to highlight alternative or additional features that may or may not be utilized in a particular embodiment of the present invention.
[0016] For the purposes of describing and defining the present invention it is noted that the term "substantially" is utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. The term "substantially" is also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.
[0017] Having described the invention in detail and by reference to specific embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims. More specifically, although some aspects of the present invention are identified herein as preferred or particularly advantageous, it is contemplated that the present invention is not necessarily limited to these preferred aspects of the invention.
CATALYST FOR HYDROGEN PRODUCTION FROM WATER GAS SHIFT
REACTION
EP1901844
Inventor: OZKAN UMIT S (US); WANG XUEQIN (US); ZHANG LINGZHI (US); NATESAKHAWAT SITICHAI (US)
Also published as: WO2006138485 (A1) // EP1901844 (A0) // AU2006259326 (A1)
Abstract --- Fe-Al-Cu catalysts have numerous industrial applications, for example, as catalysts in a water gas shift reactor. A method of producing a Fe-Al-Cu catalyst comprises the steps of providing an organic iron precursor, dissolving the organic iron precursor in a solvent solution, adding an aqueous solution comprising aluminum nitrate and copper nitrate to the organic iron precursor-solvent solution, precipitating a gel comprising Fe-Al-Cu by adding a base, and drying the gel to form the Fe-Al-Cu catalyst.