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The following quote was obtained by the news editors from the background information supplied by the inventors: "The present invention presents a method based on chemical vapor deposition reactions, particularly an enclosed-channel reactor system and a method to manufacture catalysts or support materials on the basis of atomic layer deposition (ALD).
"Catalysts are typically applied to increase reaction rate in various processes with less energy consumption, such as fuel cells and hydrogen production by water splitting. Improving the surface area between gas phase and catalyst would be a key factor to improve the reaction rate. Therefore, to obtain well-dispersed and nanoscaled catalysts with large specific area is crucial for catalytic reactions.
"The catalytic reaction can be depicted as shown in FIG. 1(a). With the help of catalyst, reactant A will be transformed to product B in a faster and energy-efficient way. In order to prevent the participation of unwanted elements, the catalytic reaction is typically contained in the enclosed-channel reactor as shown in FIG. 1(b), where the reactant A will flow through. Accordingly, the catalyst should be coated on the inner surface of channel for the catalytic reaction, as shown in FIG. 1©. Furthermore, a thermally stable nanoscaled support, shown in FIG. 1(d), would be needed to prevent the clustering of nanoscaled catalyst, at elevated temperature, leading to reduction of surface area for catalytic reaction.
"Conventionally, nanoscaled catalyst or support can be prepared by injecting liquid precursor into channels by compressed air, followed by heating at elevated temperatures. However, it is difficult to uniformly deposit the catalyst or support on channel surface with good dispersion due to restriction of channel shape or size and poor precursor liquidity. Powder metallurgy is an alternative to prepare catalyst and support by co-sintering the liquid precursor. However, only a limited amount of catalyst on the surface is available for catalytic reaction so that the utilization efficiency of catalyst is low. Therefore, it would be helpful to deposit well-dispersed nanoscaled catalyst or support on the channel surface.
"Vapor deposition is considered to deposit catalyst or support material on the channel surface with a better dispersion. As shown in FIG. 2, the gaseous precursor would, however, tend to transport through peripheral path Q1 of a reactor body 12 rather than inner path Q2 due to the difference of gas conductance. The catalyst or support would tend to deposit on the surface along the outside path, which cannot serve as reaction area. Therefore, the utilization efficiency of catalyst grown by a conventional vapor deposition process would be low. Uses of extended injection duration and high concentration may lead to a thicker coating along path Q2, but the cost would increase significantly. Therefore, it is crucial to improve the coating of catalyst or support on the inner path Q2 with less consumption of precursor."
In addition to the background information obtained for this patent application, VerticalNews journalists also obtained the inventors' summary information for this patent application: "To improve coating uniformity with less consumption of precursors, the present invention utilizes vapor deposition technique with a capping mechanism to force the precursors and purge gas to flow through the inner path of an enclosed-channel reactor.
"The present invention is intended to use chemical vapor deposition for preparation of catalyst, support or their mixture in an enclosed-channel reactor. Precursors of catalyst or support are injected into the channels of the reactor body through the inlet cap and removed from the outlet cap. Nitrogen, hydrogen or inert gas (helium, neon, or argon) is typically applied as a carrier gas to transfer less-volatile precursors into the channels. The precursors will transform to catalyst or support under adequate reaction temperature, working pressure, and gas concentration.
"The present invention is also intended to use atomic layer deposition for preparation of catalyst, support material or their mixture in an enclosed-channel reactor. The first and second precursors of catalyst or support are separately and alternatively injected into the inlet cap and removed from the outlet cap, between which a large amount of nitrogen, hydrogen or inert gas (helium, neon, or argon) is introduced as a purge gas to remove unreacted precursor and byproduct. The first and second precursors are called A and B, respectively, while the purge gas is called P. The sequential injection of A-P-B-P steps compose an ALD cycle. By repeating the ALD cycles, precursors will transform to catalyst or support under adequate reaction temperature, working pressure and gas concentration.
"The present invention of an enclosed-channel reactor system comprises a reactor body as well as an inlet cap and an outlet cap. The reactor body with a cylindrical or polygonal contour has a plurality of channels inside, which act as the surface for catalytic reaction. The inlet cap connects with the reactor body at the upstream side of gas flow and has conduit linking to the channels. The outlet cap has conduit linking to the channels at the downstream side of gas flow and connects to a vacuum pump. Both contacts of inlet and outlet caps with the reactor body are sealed with an elastomer O-ring to achieve isolation from the atmosphere.
"The present invention of an alternative enclosed-channel reactor system comprises a reactor body as well as a reactor enclosure and a reactor cap. The reactor body with a cylindrical or polygonal has a plurality of channels inside, which act as the surface for catalytic reaction. The reactor enclosure that externally encloses the reactor body is connected to a reactor cap which is either at the upstream side or downstream side of gas flow. The contact between inlet and outlet caps is sealed with an elastomer O-ring to achieve isolation from the atmosphere.
"In the present invention, inner channels in each of the above reactors can be coated with catalyst, including noble metals, such as platinum, palladium, rhodium, ruthenium, iridium and osmium, or transition metals, such as iron, silver, cobalt, nickel and tin; or support materials, including silicon oxide, aluminum oxide, zirconium oxide, cerium oxide, wherein the support materials are capable of resisting high temperature; or refractory metals, which can be chromium, molybdenum, tungsten, or tantalum.
"Based on the above enclosed-channel reactors, the present invention also refers to a method for preparing catalyst or support material by using an ALD super cycle comprising two different ALD cycles. In the first ALD cycle, the first and second precursors of catalyst or support are separately and alternatively injected into the reactor, between which a large amount of nitrogen, hydrogen or inert gas (helium, neon, or argon) is introduced to remove unreacted precursor and byproduct. The first ALD cycle is composed of sequential injection of A-P-B-P steps. In the second ALD cycle, the first precursor A is replaced by a third precursor A'. The second ALD cycle is therefore composed of sequential injection of A'-P-B-P steps.
"In the present invention, both of the first and second ALD cycles can be used to grow catalyst, including noble metals, such as platinum, palladium, rhodium, ruthenium, iridium and osmium, or transition metals, such as iron, silver, cobalt, nickel and tin; or support materials, including silicon oxide, aluminum oxide, zirconium oxide, cerium oxide; or refractory metals which can be chromium, molybdenum, tungsten, or tantalum.
"In the above mentioned method using an ALD super cycle, the A-P-B-P and A'-P-B-P ALD cycles are repeated N and M times, respectively, to form an alloy catalyst or support. Furthermore, the composition can be controlled by using an optimum ratio, N/(N+M), under adequate reaction temperature, working pressure and gas concentration.
"These features and advantages of the present invention will be fully understood and appreciated from the following detailed description of the accompanying Drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
"FIG. 1 is (a) an illustration of catalytic reaction, (b) a schematic view of enclosed-channel reactor and enlarged views of channel surface with © catalyst and (d) support/catalyst.
"FIG. 2 is a schematic view of a deposition chamber for deposition of catalyst or support material on the channel surface of a conventional enclosed reactor.
"FIG. 3 is a schematic view of the present invention of an enclosed-channel reactor system.
"FIG. 4A is a schematic view of the present invention of an enclosed-channel reactor system.
"FIG. 4B is a schematic view of the present invention of an enclosed-channel reactor system.
"FIG. 5 is a schematic view illustrating an ALD cycles.
"FIG. 6 is a schematic view illustrating a super ALD super-cycles."
URL and more information on this patent application, see: Kei, Chi-Chung; Liu, Bo-Heng; Lin, Chien-Pao; Hsiao, Chien-Nan; Hsueh, Yang-Chih; Perng, Tsong-Pyng. Enclosed-Channel Reactor System and Method to Manufacture Catalysts Or Support. Filed
Keywords for this news article include: Neon, Argon, Gases, Helium, Elements, Hydrogen, Nitrogen, Nanotechnology, Inorganic Chemicals, Emerging Technologies, Atomic Layer Deposition, Chemical Vapor Deposition,
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