High-temperature ethane dehydrogenation in microporous zeolite membrane reactor: Effect of operating conditions

Abstract

Ethylene is the largest base chemical for the chemical industry and produced either by cracking or dehydrogenation of light alkanes. The increasing demand for ethylene has stimulated substantial research into the development of new processes to reduce energy consumption. The ethane dehydrogenation reaction (EDH) using a membrane reactor is an attractive solution because the equilibrium limit can be overcome in favor of ethylene by selective removal of H2. The process intensification of EDH reaction was studied in packed-bed membrane reactors (PBMR) operating with a Pt/Al2O3 catalyst. The effects of MFI-type zeolite PBMR and operating conditions on ethane conversion, ethylene selectivity, and ethylene yield were investigated. MFI membrane reactors allowed the equilibrium limit of ethane conversion to be surpassed at high temperatures. It was demonstrated that medium-pore MFI membranes with moderate H2/C2H6 selectivity can effectively improve ethane conversion at high operation temperature by timely removal of H2 through the membranes. The experiment results showed that using MFI zeolite membrane with separation factor of 3.3 for H2/C2H6 and H2 permeance of 1.2×10−7molm−2s−1Pa−1 at 600°C helped in enhancing the ethane conversion, ethylene selectivity and ethylene yield from 12%, 86%, and 10% for the packed bed reactor (PBR) to 24%, 90% and 22% for the PBMR respectively. The model calculations have shown that near-completion ethane conversion >98% may be achieved under practically meaningful operating temperature, pressure, and space velocity even for membranes with moderate H2 selectivity and permeance.