Using brewing waste diatomite activated by ball milling to simple and sustainable synthesis of nano-H-ZSM-5 aggregates

Abstract

Brewing waste diatomite (BSDT) from the beer industry is a highly productive silica-aluminate solid waste and realizing the resource utilization of BSDT is the key to achieving the circular economy. Synthesis of zeolites from BSDT is a high value-added utilization method, but using BSDT to synthesize zeolites via “silica-alumina homologation” is difficult because of its high SiO2/Al2O3 ratio and low chemical activity. Further, using BSDT to synthesize high-quality nano-zeolites on a large scale through a simple and green method is a huge challenge. In this study, we propose a facile and scalable strategy to utilize BSDT as the only Si-Al source to prepare high-quality nano-H-ZSM-5 aggregates with hierarchical structures in a single templating agent system by solid-like transformations. The activation of BSDT was achieved by mechanical ball milling. Crystallite size and hierarchical structures are controlled by decoupling the crystal nucleation and growth processes. Due to the “silica-alumina homologation” system, aluminum species enter the zeolite framework along with the dynamic crystallization process and provide uniform acidic sites. In the methanol conversion reaction, the obtained catalysts showed longer lifetime (172.5 h) and higher light olefin selectivity (62.5%) compared to commercial catalysts. This strategy is simple, economical, and scalable, and can be extended to the synthesis of other framework-type zeolites with high SiO2/Al2O3 ratios.