Modified zeolite membrane reactor for high temperature water gas shift reaction

A porous alpha-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/CO2 perm-selectivity of 68.3 with H-2 permeance of 2.94 x 10(-7) mol/m(2) s Pa at 550 degrees 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 degrees C. The WGS reaction results demonstrate that the zeolite membrane reactor is effective for enhancing CO-conversion (chi co) at kinetically favorable high temperatures especially when high space velocity (WHSV) and low steam-to-CO ratios (R-H2O/O) are used. At 550 degrees C with a WHSV of 60,000 h(-1) and a R-H2O/CO of 1.0, the MR achieved xco of 81.7% which was significantly higher than the xco obtained in the traditional packed-bed reactor, which was 62.5%, and well above the equilibrium conversion (chi(CO,e) = 65%) as well. The results also suggest that, at high temperature (i.e. >500 degrees C), further enhancement of CO-conversion to near completion requires both membrane improvement and high-pressure operation. (C) 2010 Elsevier B.V. All rights reserved.