The interactions of lower alkanes and alkenes with H-ZSM-5 and Ga-H-ZSM-5 were studied between 373 and 923 K applying carrier-gas free pulsing of the hydrocarbons (1015-1017molecules/pulse) by means of the Temporal Analysis of Products (TAP) method. Ethane was reversibly adsorbed on H-ZSM-5 below 673 K, interaction was not observed above 673K. Ethane was adsorbed on the gallium species of Ga-H-ZSM-5 above 573K, selective dehydrogenation to ethylene occurred at 873 K and above. At low pulse intensities, the adsorption of ethylene on H-ZSM-5 could be studied without interfering reactions like oligomerization, cyclization, or aromatization. At higher pulse intensities, ethylene was converted to benzene via the consecutive formation of butenes and C6alkenes. The existence of 1-hexene and 3-methyl-1-pentene as intermediates is not likely, since they were predominantly cracked, in comparison to 1,5-hexadiene, which showed a higher rate of aromatization. © 1994, Elsevier Science B.V.
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