A comparison between the structural and catalytic properties of supported W{sub 2}C, WC and WC{sub 1{minus}x}
- Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Chemical Engineering
A series of {gamma}-Al{sub 2}O{sub 3} and SiO{sub 2} supported tungsten carbides was synthesized by the temperature programmed reaction of supported tungstates with CH{sub 4}/H{sub 2} mixtures. The three known phases, W{sub 2}C, WC and WC{sub 1{minus}x}, were evaluated as butane dehydrogenation catalysts. The microstructure and composition of the supported carbides depended on the loading and final synthesis temperature. The low and medium loaded materials were x-ray amorphous suggesting highly dispersed carbide domains on the support. The high loaded materials possessed small crystallites of W{sub 2}C, WC or WC{sub 1{minus}x}. The supported carbides were as active as a commercial dehydrogenation catalyst with comparable selectivities in several cases. The butane conversion activity decreased in the following order: W{sub 2}C > WC > WC{sub 1x}. The dehydrogenation selectivity decreased as the activity increased. The results suggest that there were two different types of sites, those catalyzing the selective dehydrogenation of butane and those capable of butane hydrogenolysis. The activity of these latter sites declined significantly with time on stream. The authors believe the hydrogenolysis activity was due to acid sites on the supported carbides.
- OSTI ID:
- 571940
- Report Number(s):
- CONF-961202--; ISBN 1-55899-358-4
- Country of Publication:
- United States
- Language:
- English
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