Zeolite Membrane Reactor for High-Temperature Water-Gas Shift Reaction: Effects of Membrane Properties and Operating Conditions

摘要

Modified MFI-type zeolite membranes were investigated as high-temperature water-gas shift (WGS) membrane reactors (MRs) in combination with a nanocrystaliine Fe/Ce WGS catalyst. The effects of the MR operating conditions and the membrane separation performance on the CO conversion (x_(co)) were studied experimentally and by calculations using a simple one-dimensional plug-flow reactor (PFR) model The experimental results showed that, at high temperatures (e.g., ＞500 ℃), the zeolite MR with moderate H_2 selectivity (e.g., α_(H_2/CO_2) ～ 31, and α_(H_2/co) ～ 25) and permeance (P_(m,H_2) ～ 0.9 × 10~(-7) mol s~(-1) m~(-2) Pa~(-1)) was capable of overcoming the limit of equilibrium CO conversion and x_(co) of the MR could be further enhanced by increasing the reaction pressure while keeping the permeate pressure unchanged. At high temperatures and high reaction pressures, CO is rapidly consumed by a fast reaction that minimizes the membrane permeation of unreacted CO; meanwhile, the efficiency of H_2 removal is improved as a result of the increased H_2 partial pressure difference across the membrane. The model calculations have indicated that the current membrane has the potential to achieve high CO conversion of x_(co) ＞ 99% under practically meaningful operating conditions.