Pulse reaction studies of gallium modified H-ZSM5 catalysts with propane

Abstract

H-ZSM5 zeolites were impregnated with gallium amounts of 2 and 3 wt.%, and were activated by two reduction-oxidation cycles, respectively by hydrogen and air. Propane conversion and hydrogen production were followed at 703 K in a pulse reaction system coupled to a quadrupole mass spectrometer. Hydrogen, methane, ethylene, propene and minor amounts of ethane, benzene and toluene were detected as products. Propane consumption and hydrogen, methane, ethylene and propene production increased with number of pulses to a steady-state value. The rise in propane conversion, in hydrogen production and in the H2/C3H8 ratio clearly indicates that active sites for the dehydrogenation reaction are produced upon exposure to propane. The amount of hydrogen evolved in the first pulse was very small as compared to propane conversion, which indicates that probably the active sites are generated by gallium reduction with hydrogen atoms from propane. © 2008 Elsevier B.V. All rights reserved.