Preparation of a novel structured catalyst based on aligned carbon nanotube arrays for a microchannel Fischer-Tropsch synthesis reactor
A novel catalyst microstructure based on aligned multiwall carbon nanotube arrays was synthesized. Its advanced heat and mass transport characteristics coupled with high surface area led to superior performances for Fischer-Tropsch synthesis in a microchannel chemical reactor. The fabrication of such a novel catalyst structure first involved metalorganic chemical vapor deposition (MOCVD) growth of a dense Al2O3 thin film over FeCrAlY foam substrate to enhance adhesion between catalyst layer and metal substrate. Aligned arrays of multiwall carbon nanotubes were grown over the substrate by catalytic decomposition of ethylene. These nanotube bundles were directly attached to the FeCrAlY substrate through a thin layer of oxide thin film. When the outer surfaces of nanobundles were coated with a catalyst layer, a unique hierarchical catalyst structure with nanoporous interstitials between the bundles was created. Thus, engineered catalysts based on such a novel hierarchical structure minimizes mass transfer encountered in the gas-liquid-solid three phase reactions. In addition, high thermal conductivity of carbon nanotube and the direct attachment of these nanobundles to the metal foam allow efficient heat removal from catalytic sites. The advanced heat and mass transfer on this novel structured catalyst was demonstrated in Fischer-Tropsch synthesis in a microchannel fixed bed reactor. The presence of carbon nanotube arrays improved dispersion of active metals and reduced mass transfer limitation, leading to a factor of four enhancement of Fischer-Tropsch synthesis activity. The improved temperature control with the carbon nanotube arrays also allows the Fischer-Tropsch synthesis being operated at temperatures as high as 265 C without reaction runaway favoring methane formation.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 876932
- Report Number(s):
- PNWD-SA-7010; 6696; TRN: US200621%%894
- Journal Information:
- Catalysis Today, 110(1-2):47-52, Journal Name: Catalysis Today, 110(1-2):47-52
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
CARBON
CATALYSTS
CHEMICAL REACTORS
CHEMICAL VAPOR DEPOSITION
FISCHER-TROPSCH SYNTHESIS
INTERSTITIALS
MASS TRANSFER
MICROSTRUCTURE
NANOTUBES
PACKED BEDS
SURFACE AREA
TEMPERATURE CONTROL
THERMAL CONDUCTIVITY
THIN FILMS
Fischer-Tropsch synthesis
carbon nano tube
engineered catalyst
microchannel reactor
Environmental Molecular Sciences Laboratory