Modified zeolite membrane reactor for high temperature water gas shift reaction

Abstract

A porous α-alumina tube supported MFI-type zeolite membrane was modified by depositing molecular silica species in the zeolitic channels via in situ catalytic cracking of methyl diethoxysilane at a limited number of active sites. The modified zeolite membrane exhibited a H 2/CO 2 perm-selectivity of 68.3 with H 2 permeance of 2.94 × 10 −7 mol/m 2 s Pa at 550 °C. The modified zeolite membrane tube was packed with a cerium-doped ferrite catalyst for water gas shift (WGS) reaction in a temperature range of 400–550 °C. The WGS reaction results demonstrate that the zeolite membrane reactor is effective for enhancing CO-conversion ( χ CO) at kinetically favorable high temperatures especially when high space velocity (WHSV) and low steam-to-CO ratios R H 2 O / CO are used. At 550 °C with a WHSV of 60,000 h −1 and a R H 2 O / CO of 1.0, the MR achieved χ CO of 81.7% which was significantly higher than the χ CO obtained in the traditional packed-bed reactor, which was 62.5%, and well above the equilibrium conversion ( χ CO, e = 65%) as well. The results also suggest that, at high temperature (i.e. >500 °C), further enhancement of CO-conversion to near completion requires both membrane improvement and high-pressure operation.