Light alkane aromatization over modified Zn-ZSM-5 catalysts: characterization of the catalysts by hydrogen/deuterium isotope exchange
The selectivity obtained in the aromatization of propane over Zn-ZSM-5-based catalysts (Si/Al nominal ratio = 35) increased from about 69% (carbon basis) to 74–91% when a second transition metal ion is introduced into the catalyst. The effect, previously reported for the case of Fe3+ ions, has now been shown to be more general and is seen also for the ions of chromium, cobalt or manganese. It is likely that these ions are present under aromatization conditions in a partially reduced state. H2/D2 isotope exchange rates show large enhancements on the reduced Fe-Zn/ZSM-5 and Co-Zn/ZSM-5 samples. This aspect of aromatization catalysis has not been reported before.
KeywordsAromatization Alkanes Zinc-zeolites Transition metal ions H2/D2 exchange
One of us (LML) thanks the National Research Foundation and the Molecular Sciences Institute of the School of Chemistry, University of the Witwatersrand, Johannesburg, for financial support. The authors are indebted to ERACHEMISTRY for partial financial support (grant # 75009) and for OTKA grants (NNF 78837 and NNF2 85631). The research was coordinated by Hungarian—South-African intergovernmental S & T co-operation program.
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