Morphology controlled synthesis of ZSM-5 and enhanced catalytic activity in polypropylene hydrocracking

Abstract

ZSM-5 zeolite has emerged as an outstanding catalyst in converting waste plastics into high-value chemicals. Constructing hierarchical micro-mesoporous ZSM-5 can significantly enhance diffusion characteristics and consequently improve catalytic cracking performance. The morphology of ZSM-5 plays a crucial role in altering its catalytic hydrocracking efficiency in plastic degradation, but the reasons behind this is not clear. Herein, by precisely adjusting the structure-directing agent (SDA) ratio to control nucleation dynamics, we have developed a morphology-controlled synthesis strategy for ZSM-5 zeolites. Two distinct hierarchical ZSM-5 catalysts were successfully fabricated: plate-shaped n-ZSM-5 and quasi-spherical s-ZSM-5. And, increasing the SDA content was worked in promoting nucleation kinetics, facilitating the incorporation of active components into the zeolite framework, and increasing surface acid site density. The plate-shaped n-ZSM-5 exhibited exceptional catalytic performance in polypropylene hydrocracking with a liquid yield of 57.3 ​%, and proved to maintain effective activity for the actual conversion of plastic waste. The catalytic mechanism reveals that the morphology engineering can effectively regulate mass transport within catalyst pores, provide a novel approach for tailoring zeolite catalyst properties. This work offers fundamental insights into structure-performance relationships for advanced plastic upcycling catalysts.