Low-cost and efficient synthesis of SSZ-35 zeolite through a seed-assisted approach

Abstract

A low-cost and process-intensified synthesis approach of SSZ-35 zeolite via a seed-assisted method is presented. This approach involves the development of a relatively inexpensive template and the application of seeds to minimize crystallization time and template consumption. Herein, N-Ethyl, N-methyl 2,6-cis-dimethylpiperidinium hydroxide (EMDMPOH) is selected as a template to synthesize SSZ-35 zeolite, and a simplified and optimized scheme for the preparation of such a template is proposed. Specially, the high-purity EMDMPOH is prepared by a sequential alkylation of 2,6-dimethylpiperidine with iodoethane and iodomethane, followed by ion exchange. By employing a seed-assisted strategy, the synthesis process of SSZ-35 zeolite is intensified, resulting in a significant reduction in crystallization time from 7 d to 75 h. Systematic characterizations reveal that the synthesized SSZ-35 zeolite has smaller crystals and larger specific surface area in comparison with the reference sample, leading to enhanced selectivity in n-octane hydroisomerization. Moreover, the cost accounting analysis shows a notable decrease in the synthesis cost of SSZ-35 zeolite by using the synthesis route that combines the simplified process for preparing the template and the reduced amount of template.