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

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.