Modified zeolite membrane reactor for high temperature water gas shift reaction

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 H2/CO2 perm-selectivity of 68.3 with H2 permeance of 2.94 × 10−7 mol/m2 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 (χCO) at kinetically favorable high temperatures especially when high space velocity (WHSV) and low steam-to-CO ratios (RH2O/CO)RH2O/CO are used. At 550 °C with a WHSV of 60,000 h−1 and a RH2O/CORH2O/CO of 1.0, the MR achieved χCO of 81.7% which was significantly higher than the χCO obtained in the traditional packed-bed reactor, which was 62.5%, and well above the equilibrium conversion (χCO,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.