A comparative study of O 42− /ZrO 2 and zeolite beta as catalysts for the isomerization of n-butane and the alkylation of isobutane with 2-butene

Abstract

The activity, selectivity, and decay behavior of SO 2−/ ZrO 2 (SZ) and zeolite Beta (Hβ) catalysts are compared for two acid catalyzed demanding reactions, i.e., the isomerization of n-butane, and the alkylation of isobutane with 2-butene. The superacidity present in the SZ sample makes this catalyst active for both reactions at lower temperatures than the zeolite. For the isomerization of n-butane the reaction pathway leading to isobutane was seen to be different for both catalysts. A similar decay behavior was observed on the two catalysts, but the SZ sample gave a much higher selectivity to isobutane. For the alkylation reaction, the SZ catalyst is much more selective to TMP's than Hβ at low reaction temperatures. The lower selectivity to TMP's obtained on Beta zeolite is mainly due to the formation of DMH's by dimerization of butenes, while undesirable cracking reactions leading to C 5-C 7 products occur to a higher extent on the superacid SZ catalyst. The latter deactivates much faster than the zeolite. The acid strength distribution, and hydrogen transfer activity were seen to determine the changes in product distribution with time-on-stream obtained on both catalysts.