Combined sorbent and catalyst material for sorption enhanced reforming of methane under cyclic regeneration in presence of H2O and CO2

Abstract

An investigation on an innovative calcium‑nickel Combined Sorbent and Catalyst Material (CSCM) for Sorption Enhanced Reforming (SER) of methane is presented in this paper. After hydrothermal synthesis, a nominal 30 wt% CaO-based sorbent supported on mayenite was physically mixed with a commercial reforming catalyst and granulated to obtain bifunctional particles of 200–300 μm. Materials were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller surface analysis (BET) and Mercury- intrusion prosimetry (Hg-porosimetry). A novel thermo-gravimetric analysis (TGA) approach was employed for investigating SER activity, particularly the materials performance during multicycling methane reforming and sorbent carbonation followed by regeneration in oxidative atmosphere – either in the presence of steam or CO2 at high temperature. When regeneration is carried out in 100 vol% CO2 at 925 °C, an intermediate reduction step between cycles was crucial to maintain the catalytic activity of the CSCM for 100 consecutive sorption-regeneration cycles. In spite of a stable catalytic activity, the initial sorption capacity of the CSCM sorbent function (~16gCO2/100gCSCM) declined progressively with cyclic runs and stabilized at ~10gCO2/100gCSCM from cycle 90 onwards. This decline in capacity has been related to CaO depletion by solid phase reaction with the catalyst support.