Preparation And Structure-Performance Relationship Of Bifunctional Catalysts For Sorption-Enhanced Steam Methane Reforming

A series of Ni/CaO-AbO3catalysts with varying CaO/Al2O3mass ratios were prepared by a sol-gel method and applied to the sorption-enhanced steam methane reforming process (SESMR). The structural properties of fresh and used catalysts were characterized detailedly by various techniques. The reduced bifunctional catalysts consisted mainly of Ni, CaO and Ca5Al6O14. The structure of catalyst depended strongly on the CaO/Al2O3mass ratio, which in turn considerably affected the CO2capture capacity and the catalytic performance. Among all the bifunctional catalysts, the catalyst with a CaO/Al2O3mass ratio of6or8possessed the highest surface area, the smallest Ni particle size and the uniform distribution of Ni, CaO and Ca5Al6O14. Both powder and pelletized bifunctional catalysts were evaluated for reactivity and stability, and the structure-property relationship of the catalysts was explored. For the catalyst with a CaO/Al203mass ratio of no higher than6, its CO2capture capacity was well maintained during50carbonation-calcination cycles. Moveover, during50consecutive SESMR cycles with a lower steam/methane molar ratio of2, the powder catalyst with a CaO/Al2O3mass ratio of6showed high activity and stability, but the corresponding pellet catalyst exhibited decreased activity and stability after20consecutive SESMR cycles due to coke deposition. In addition, the CaO utilization efficiency of the bifunctional catalyst for CO2capture was higher than that of mode in which catalyst and sorbent were used individually.