Catalytic Pd0.77Ag0.23 alloy membrane reactor for high temperature water-gas shift reaction: Methane suppression

Abstract

Abstract A catalytic membrane reactor was constructed using inner coated Pd0.77Ag0.23 (mass fraction) alloy membrane on Al2O3 hollow fiber substrate, prepared by electroless plating method and packed with Ni-Phyllosilicate catalyst for high temperature water gas shift (WGS) reaction. The performance of the ultra-thin ∼1\u202fµm membrane was evaluated in a temperature range of 300–500\u202f°C and hydrogen partial pressure of 50–200\u202fkPa. The membrane showed high hydrogen permeance of 5.11\u202f×\u202f10−4\u202fmol.m−2\u202fs−1\u202fPa−0.65 at 100\u202fkPa pressure and 500\u202f°C. WGS reaction was carried out using the membrane reactor at temperature range of 400–500\u202f°C, the effect of pressure, steam to carbon ratio and GHSV on CO conversion and methane formation were evaluated. Results showed increase in H2 permeation with increase in temperature and pressure, which eventually helps surpass the thermodynamic equilibrium CO conversion at high temperatures. H2 recovery and CO conversion decreased with increase in GHSV from 2896\u202fh−1 to 11008\u202fh−1. In this study, the shifting of equilibrium conversion and suppressed methane formation is also demonstrated at a temperature range of 400–600\u202f°C. WGS reaction was performed in a catalytic membrane reactor at 600\u202f°C for 100\u202fh and it was found to be stable in terms of CO conversion and H2 recovery for the entire range of investigation. Finally, the membrane was tested for its performance using a reformate gas mixture similar to the gasification plant without any diluents and the conversion was found to be enhanced by 28% in terms of CO conversion at 500\u202f°C using a membrane reactor.