Microwave assisted synthesis of MTT-TON intergrowth crystals for the catalytic conversion of naphtha to olefins

Abstract

We present herein, the microwave assisted synthesis of SSZ-54, an intergrowth of MTT and TON frameworks using novel dual templates and the ability of the synthesized zeolites in the cracking of hexane to produce propylene was examined. SSZ-54 zeolite was successfully synthesized in a shorter time of 12 h via microwave heating as compared to 6–9 days by conventional oven. To tackle the inherent diffusion resistance in one-dimensional zeolite, we further reduced mass transfer limitation in the synthesized SSZ-54 zeolite by employing desilication and subsequent dealumination using a mixture of NaOH and TEAOH (for desilication) and nitric acid (for dealumination). N2 sorption of modified SSZ-54 samples presented improved mesopore volume, about 30% increment, with zero loss in micropore volume when compared to the parent sample. Furthermore, modified SSZ-54 zeolite showed enhanced catalytic activity and improved resistance to deactivation during hexane conversion. Parent and hierarchical zeolites displayed appreciable conversion for 10 h time on stream, with desilicated and dealuminated sample (DSA-50) showing the highest conversion of ca. 90% during the first 1 h and ca.60% selectivity to light olefins.