Deactivation mechanism of acetone to isobutene conversion over Y/Beta catalyst

Abstract

The conversion of acetone derived from biomass to isobutene has attracted extensive attentions. In comparison with Brønsted acidic catalyst, Lewis acidic catalyst could exhibit a better catalytic performance with a higher isobutene selectivity. However, the catalyst stability remains a key problem for the long-running acetone conversion and the reasons for catalyst deactivation are poorly understood up to now. Herein, the deactivation mechanism of Lewis acidic Y/Beta catalyst during the acetone to isobutene conversion was investigated by various characterization techniques, including acetone-temperature-programmed surface reaction, gas chromatography-mass spectrometry, in situ ultraviolet-visible, and¹³C cross polarization magic angle spinning nuclear magnetic resonance spectroscopy. A successive aldol condensation and cyclization were observed as the main side-reactions during the acetone conversion at Lewis acidic Y sites. In comparison with the low reaction temperature, a rapid formation and accumulation of the larger cyclic unsaturated aldehydes/ketones and aromatics could be observed, and which could strongly adsorb on the Lewis acidic sites, and thus cause the catalyst deactivation eventually. After a simple calcination, the coke deposits could be easily removed and the catalytic activity could be well restored.