In this paper, we present the design, fabrication, and performance of novel ceramic microchannel reactors in heat-exchanger and fuel-reforming applications. Reactor design is based on the results of computational fluid mechanics simulations so that uniform fluid flow and thermal gradients are observed across the reactor body. Reactors are fabricated by CoorsTek, Inc. as four-layer Pressure Laminated Integrated Structures using 94% Al2O3 materials. The cost-effective PLIS fabrication produces a single ceramic body with internal microchannels and manifolding. High-temperature performance of the ceramic microchannel reactor is measured through non-reactive heat-exchanger experiments. After coating rhodium catalyst materials over two of the four reactor layers, use of the ceramic microchannel reactor in fuel-processing applications is demonstrated through catalytic partial oxidation of butanol. While significant syngas formation is demonstrated, further work is necessary to improve reforming conditions, increase the selectivity to hydrogen and carbon monoxide, and integrate the microchannel reactor with a tail-gas combustor.
Hexaaluminate catalysts offer excellent high-temperature stability compared to the equivalent metal-based catalysts. Their stability also lends well to use as a catalyst support. However, use of novel hexaaluminates is limited in fuel processing for fuel-cell applications. In this paper, we report on the performance of hexaaluminates as a catalyst support in the steam reforming of methane. The hexaaluminates are synthesized by a metal-exchange process using alumoxane precursors that enable a wide range of metal substitutions. Performance is evaluated using a unique stagnation-flow reactor that enables detailed probing of the boundary layer above the catalyst-impregnated stagnation surface. Experimental results are compared with models to understand fundamental reaction kinetics and optimize catalyst performance. RhSr-substituted hexaaluminates with a Rh impregnation are shown to yield the best performance. Scanning- and Transmission-Electron Microscopy are used to characterize the different types of hexaaluminates, and to examine the effect of aging on catalyst structure.
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