CO2CH4 reforming over NiO/γ-Al2O3 in fixed/fluidized-bed multi-switching mode

CO2 reforming of methane over NiO/γ-Al2O3 catalyst was investigated in a fixed/fluidized-bed multi-switching mode at 1073 K, 1 atm, a GHSV of 93,750 h−1 and a fixed ratio of CO2/CH4 = 1.5. When the mode-switching reforming test was carried out in the following mode order: fixed-, fluidized-, fixed-bed again, and finally fluidized-bed, the CH4 conversion alternated between low and high (48, 92, 75, 89%). The form and amount of carbon deposited on the spent catalysts recovered from the mode-switching experiments that ended at different times of the different modes were evaluated by TG, TPO and XPS analyses. The results showed that not only was less carbon formed in the fluidized-bed reforming, but gasification of the carbon, especially the CC species, was also more significant under the fluidized-bed operation. Furthermore, the H2-TPR, H2-TPD and XPS analyses of the spent catalysts showed that fluidizing the catalyst particles in the bed under the reforming reaction conditions is favorable to improve the reduction extent of the catalyst and to increase the surface area of active metallic nickel. Possible reasons for all these observations were explored and are discussed in this paper.