Decomposition of ethane and its reaction with CO{sub 2} over Rh/ZSM-5 catalyst
- Attila Jozsef Univ., Szeged (Hungary). Inst. of Solid State and Radiochemistry
The interaction of ethane with Rh/ZSM-5 and its decomposition and reactions with CO{sub 2} on Rh/ZSM-5 have been investigated. Methods used were Fourier-transform infrared spectroscopy and temperature-programmed desorption and reaction (TPD and TPR). The decomposition of ethane and its reaction with CO{sub 2} have been studied in a fixed-bed continuous-flow reactor. IR measurements showed that ethane interacted strongly with the highly dispersed Rh above 206 K and gave rise to the formation of ethylidyne surface species very likely through the transient formation of ethylene. At 523--573 K, the decomposition of ethane produces hydrogen, methane, and propane. Above 623 K ethylene became the main product, but benzene and toluene were also detected. Independent of the temperature, the rate of the decomposition decayed after 5--10 min to a very low level (1--2% conversion), but it did not cease completely even after several hours (673 K). The reactivities of surface carbon formed at different temperatures toward H{sub 2}, O{sub 2}, and CO{sub 2} have been examined. Carbon exhibited the highest reactivity with O{sub 2} and less reactivity with CO{sub 2}. The peak temperatures of its reaction in TPR shifted to a higher temperature with the temperature of its production in all the three cases. Carbon formed at 773 K in the ethane decomposition reacted with CO{sub 2} at maximum rate at 973 K. The reaction between C{sub 2}H{sub 6} and CO{sub 2} occurred rapidly above 700 K to give mainly H{sub 2} and CO with a ratio of 0.3--0.6. In contrast with the CH{sub 4} + CO{sub 2} reaction on the same catalyst, a significant deactivation of the catalyst occurred at the stoichiometric CO{sub 2}/C{sup 2}H{sub 6} ratio. This feature is attributed to the low reactivity of hydrocarbon fragments formed by the decomposition of ethane compared to those produced by CH{sub 4} dissociation. Deactivation can be decreased or almost ceased by using a large excess of CO{sub 2}.
- OSTI ID:
- 687739
- Journal Information:
- Journal of Catalysis, Vol. 186, Issue 2; Other Information: PBD: 10 Sep 1999
- Country of Publication:
- United States
- Language:
- English
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