Hierarchically nano porous nano crystalline ZSM-5 for improved alkylation of benzene with bio-ethanol

Abstract

In an attempt to realize enhanced textural properties of nano crystalline ZSM-5 such as high surface area, porosity and easy accessibility of active sites, a nano crystalline ZSM-5 (∼20nm) exhibiting hierarchical nano pores has been hydrothermally synthesized (SNZ) from sodium-free gel mixture and readily explored to ethyl benzene production through alkylation of benzene with bio-ethanol. A micrometer range crystal size ZSM-5 (SMZ) processing same Si/Al ratio was also prepared by traditional hydrothermal method and tested toward the same reaction so as to assess any differences in the conversion and product patterns and their ultimate effect on the time-on-stream performance of the catalyst. The materials have been thoroughly characterized by XRD, FTIR, SEM, TEM, surface area, pore volume, pore size distribution and acidity. The SNZ exhibited high surface area, external surface area along with significant increase in pore volume especially contributed by the nano size pores. The sample also exhibited superior catalytic activity in terms of conversion, ethyl benzene yields at all the reaction temperatures studied. Detailed studies were conducted on the SNZ catalyst such as the effect of reaction WHSV, benzene: ethanol ratio, time-on-stream activity and regenerability performance of the catalyst. The catalyst exhibited constant activity within the 36h reaction run up to the 5 reaction-regeneration cycles studied.