Modified Ferrites As Catalysts for High Temperature Water Gas Shift Reaction

In recent years, a large number of studies (feasibility, computational and real time analyses) have been performed on water gas shift (WGS) reaction in membrane reactors. The WGS reaction in a membrane reactor (MR) is potentially capable of completing the CO conversion and achieving simultaneous H₂/CO₂ separation in a single stage operation. A membrane for this reaction typically operates at 450 ^oC to 550 ^oC temperatures and pressures ranging from 1-20 bar. Development of catalysts for membrane reactors operating at these high pressures and temperatures have to meet stringent requirements. The present study is aimed at developing various modified ferrite catalysts for high temperature WGS membrane reactor applications. The idea was to stimulate the ferrite formation via doping with certain foreign cations and to promote the Fe³⁺ « Fe²⁺ redox couple. The WGS feed condition were chosen to mimic conditions found in a membrane reactor. For this purpose, various doped modified ferrite catalysts were prepared using ammonia assisted coprecipitation method. The prepared catalysts were characterized by using TPR, Raman, XRD, Mossbauer and X-ray photo electron spectroscopic techniques and evaluated for WGS reaction in the temperature region 400-550 ^oC and at a stream to CO ratio 3.5 and 1.5 which the conditions used in our membrane reactor. The WGS activity observed was found to be determined by the nature and amount of dopant used in a given case. Our structural and surface characterization results show that dopants exhibit different structural effect in the bulk and on the surface of the ferrite. These results will be presented in this study.