Hydrogen-permeable DDR zeolite membrane packed with Zn/HZSM-5 catalyst for methane co-aromatization with ethylene

Abstract

Co-aromatization of methane (CH4) and ethylene (C2H4) over a membrane reactor (MR) using hydrogen-permeable DDR zeolite membrane packed with Zn/HZSM-5 catalyst was studied for the first time. The adopted DDR zeolite membrane showed high H2 selectivity for separations of binary H2/CH4 and trinary H2/CH4/C2H4 mixtures. Typically, the selectivities for H2/CH4 and H2/C2H4 were 40 and 29 for trinary mixture separation at room temperature, respectively. The effects of reaction temperature, methane-ethylene feed ratio, space velocity and H2 removal on the membrane reaction performance were investigated systematically. The membrane reactor can achieve 8.43% methane conversion with BTX selectivity of 80.68% within 1 h under the optimal reaction conditions (reaction temperature 450 °C, methane-ethylene feed ratio 3:2, weight hourly space velocity (WHSV) 800 mL/(gcat h), sweep helium flow rate 15 mL/min). Compared to a fixed-bed reactor (FBR) with similar reaction condition, the achieved methane conversion and BTX yield were improved by ∼42% and ∼10%, respectively, due to the timely removal of H2 from the reaction system. The membrane also showed good stability, and the methane conversion maintained at about 7% for about 30 h. After burning the coke formed on the catalyst, the initial reaction performance can be restored, showing a good regeneration ability.