Extra-framework cations promoted zeolite-encaged cobalt catalysts towards efficient ethylbenzene dehydrogenation

Abstract

The transformation of ethylbenzene to styrene through direct dehydrogenation is essential process in chemical industry, indispensable for the synthesis of polymers and plastics. Herein, faujasite zeolite encaged cobalt catalyst with potassium ion as the extraframework cations, namely K-Co@Y, is reported to be a robust catalyst for ethylbenzene direct dehydrogenation, showing ethylbenzene conversion of ∼45 % and styrene selectivity of ∼95 % simultaneously under employed conditions. The superior performance of K-Co@Y in comparison with Na-Co@Y is attributed to the effective modulation of zeolite-encaged Co2+ species by extraframework K+ ions, which increases the electron density of cobalt sites and facilitates CH bond activation. Although coke deposits cause gradual deactivation, the structural integrity of K-Co@Y can be well preserved during the dehydrogenation reaction and the performance can be full restored via a simple calcination regeneration step, making K-Co@Y an eligible catalyst for long-term running in the continuous regeneration mode. This study highlights the vital role of extraframework cations in zeolite-encaged single-site catalysts for target chemical transformations and opens up a new way to modulate the performance of zeolite catalysts.