Regulation of partial oxidation in biochar-catalyzed tar reforming for hydrogen upgrading in syngas: The effect of oxygen concentration

Abstract

Effective methods for maintaining catalyst activity in tar reforming have been a major focus during the development of biomass gasification technology. The role of partial oxidation in regulating the catalytic efficiency of biochar in tar reforming was investigated using a fluidized bed/fixed bed reaction system. The physico-chemical structures of biochar were characterized by FTIR, Raman, nitrogen adsorption and thermosgravimetry analysis. The tar characterization was analyzed by GC–MS and the production of gas components was monitored on-line with synthetic gas analyzer. The results reveal that partial oxidation regulation (0.2 % – 0.4 % O2) can potentially maintain the biochar’s catalytic efficiency and facilitates the production of hydrogen in gas. The addition of oxygen effectively inhibits the coke deposition on biochar. As the O2 concentration is increased to 0.4 %, the total conversion of tar increasing to a maximum of 0.056 g/g, an increase of 27 % compared to the absence of oxygen. The H2 yield is also increased to a maximum of 0.523 L/g. When the O2 concentration is further enhanced (∼0.6 %), more H2 is consumed by oxygen, the H2 yield is reduced and the tar conversion capacity of biochar is significantly weakened. Partial oxidation regulation maintains the pore structures of the biochar, but there is a conversion of microporous pores to meso-macroporous pores. Partial oxidation regulation effectively inhibits the loss of O-containing structures on biochar, but also contributes to its increased graphitization.