Selective recovery of light olefins from polyolefin catalyzed by Lewis acidic Sn-Beta zeolites without Brønsted acidity

Abstract

Recovering valuable products from waste materials has been critical in saving limited fossil resources. This study investigated the effects of the acid type in zeolites on the yields of light olefins during the catalytic cracking of polyolefins. Brønsted acid sites in zeolites promote the oligomerization of olefins via protonation, decreasing the light olefin yield. We prepared Lewis acidic Sn-Beta zeolites without Brønsted acids using a dealumination procedure. Sn-Beta zeolites exhibited a higher yield of light olefins (45%) than the pristine Beta zeolite (24%) on low-density polyethylene cracking. Our experiments revealed that Lewis acid sites promote light olefin production, and the absence of Brønsted acid sites dramatically inhibited the consecutive reactions, thereby increasing the light olefin yields. This study provides a new guideline for controlling the product distribution of polyolefin catalytic cracking.