Catalytic behaviors of alkali metal salt involved in homogeneous volatile and heterogeneous char reforming in steam gasification of cellulose

Abstract

The current study aimed to investigate catalytic behaviors of alkali metal salt participating in homogeneous steam-volatile and heterogeneous steam-char reforming reactions in steam gasification of cellulose. The results indicate that the temperature is a key parameter which significantly influenced both yield and composition of gas and tar and catalytic performances of KCl. Externally added steam had negligible effect on cracking/reforming of macromolecules volatiles at the temperature of 700 and 900 °C without KCl, whereas in the presence of KCl, it would be activated and further reacted with low reactivity macromolecules volatiles, leading to an increase in gas yield and a decrease in tar yield. KCl was notably involved in homogeneous steam-volatile reactions, and enhanced the water gas shift reaction and tar reforming reactions. However, KCl had little promotion effect on thermal cracking/reforming of levoglucosan in homogeneous steam-volatile reforming process at 500 °C. Its inhibition effect on levoglucosan formation mainly acted during the primary pyrolysis reactions. KCl could also enhance heterogeneous in situ char-steam reaction resulting in a higher H2 yield. The general pathway of KCl involved in homogeneous/heterogeneous reactions in steam gasification of biomass was eventually proposed.