Acid-base catalysis advanced sciences and spreading applications to solutions of environmental, resources and energy issues: ABC-7, 7th International Symposium on Acid–Base Catalysis, Tokyo, May 12–15, 2013

Abstract

MCM-68 (MSE topology) with three-dimensional 12–10–10-ring channel system was focused on, expecting the hybrid character of ZSM-5 (MFI topology) and beta (*BEA topology), as a solid acid catalyst for hexane cracking reaction. The proton form of MCM-68 without dealumination having Si/Al ratio around 12 was deactivated rapidly during the reaction due to heavy coke formation, whereas dealuminated MCM-68 exhibited sufficient catalytic activity and durability to coke formation for hexane cracking at the reaction temperatures from 450 to 600 °C. The dealuminated MCM-68 also had higher propylene selectivity of 45–50% in comparison with other zeolite catalysts such as ZSM-5, mordenite and beta at the reaction temperatures of 450 to 600 °C. Both the MCM-68 catalysts before and after dealumination were regenerated after the reaction at 600 °C to exhibit almost the same performance as the initial catalyst. At higher reaction temperature such as 650 °C, the catalyst was deactivated rapidly mainly due to coke formation again. In order to avoid this deactivation, modification of MCM-68 with lanthanum oxide simply by impregnation was performed. The La-modification mainly deactivated the active site on the external surface and was found to be an effective way for avoiding heavy coke formation to maintain catalytic activity and selectivity to propylene.