Encapsulation of phosphine-palladium complex in USY zeolite for hydroesterification of ethylene to methyl propionate

With the development of green chemistry, researchers are eager to develop separable and recyclable catalyst for methyl propionate production through ethylene hydroesterification. Herein, a novel zeolite-encapsulated Pd complex was developed for ethylene hydroesterification with CO and methanol to methyl propionate. The introduced Pd component is coordinated with 1, 2-bis (di- tert -butyl phosphinomethyl) benzene ligand to form Pd complex, which is encapsulated in USY zeolite. This scheme solves the challenge of coupling phosphine-palladium complexes with acid promoters as heterogeneous catalysts. It was found that the increasing density of Brønsted acid sites on USY zeolite favors the ethylene hydroesterification. Furthermore, the influences of catalyst preparation and reaction conditions on the catalytic performance were assessed. As a result, the ethylene conversion could reach 99 % with MP selectivity of 100 % under the optimal condition. In addition, the catalytic heterogeneity and stability of zeolite-encapsulated Pd complex were investigated.