Study on the Deactivation of the MCM-22 Catalyst in Liquid Phase Cyclopentene Hydration

Abstract

Abstract The deactivation of MCM-22 zeolite was found to occur gradually during the direct hydration of cyclopentene to cyclopentanol in the liquid phase. When the catalyst was re-used in the next batch hydration cycle, the reaction rate reached only half of original value. The high selectivity to cyclopentanol was retained even the re-used catalyst was employed in the hydration reaction. The deactivation of MCM-22 zeolite is caused by carbonaceous deposit settled down in catalyst pores. Crystallinity and structure of zeolite did not change either during the zeolite exposition in hydration cycle or during the catalyst reactivation at 823 K. The zeolite fast deactivation is caused by cyclopentadiene, which is impurity contained in commercial starting raw material, but the significant catalytic activity decrease was also observed, when the cyclopentene free of dienic impurities was used as a raw material. Therefore, carbonaceous deposit settled down in catalyst pores had to be generated although by acid catalysed reaction of olefinic cyclopentene. Only partial restoration of catalyst activity is possible, when MCM-22 is reactivated either using calcination under temperature programme 1 K.min-1/823 K/+8 hours or using hydrogen peroxide as oxygenation agent.