Conversion of Propane Using H-ZSM-5 and Ga/H-ZSM-5 in the Presence of Co-fed Nitric Oxide, Oxygen, and Hydrogen

Article abstract of DOI:10.1006/jcat.1995.1005

The conversion of propane to propene and aromatic hydrocarbons has been studied using cofed NO, O2, and H2 to probe the reaction mechanism with H-ZSM-5 and Ga2O3/H-ZSM-5 physical mixtures as catalysts.NO co-feeding with H-ZSM-5 causes a decrease in the conversion of propane and in the yields of methane and aromatic products.These effects are reversible on the removal of NO, but there is a significant delay that is dependent on the duration of the NO co-feeding, indicating that the effects are due to poisoning of active sites.Although propane conversion decreases, NO does not affect the yield of propene.Similar effects are observed when NO is co-fed using Ga2O3/H-ZSM-5 as catalyst.O2 co-feeding with H-ZSM-5 leads to an increase in propane conversion, propene yield, and deactivation rate, whereas, as observed with NO, the yields of methane and aromatic products are decreased.Co-feeding of excess H2, which is a major product from the aromatization of propane, has very little effect on the conversion of propane over H-ZSM-5, although the selectivities to alkanes are increased.For Ga2O3/H-ZSM-5 physical mixtures containing 10-90percent Ga2O3, H2 co-feeding leads to a significant decrease in propane conversion and in the yield of aromatic products.For Ga2O3 alone, the co-feeding of H2 gives a significant increase in propane conversion with only limited effects on the product selectivities.A series of experiments that use a physical mixture of Ga2O3 powder and pelleted H-ZSM-5 with and without co-fed H2 in which the mixture is separated by sieving after reaction for 3 h at 600 deg C is described.The results are interpreted in terms of a mechanism in which propane is activated at the interface between the gallium oxide and the zeolite.