Gasification of biomass model compounds in supercritical water

Gasification of cellulose, hemicellulose, lignin and their mixtures with K₂CO₃ as catalyst in supercritical water was conducted at 450°C and 27.5 MPa in a high-pressure batch autoclave. The experimental results showed that the gasification performance was in the order of cellulose > hemicellulose > lignin, which could be explained by the difference in molecular framework. The existence of lignin in the mixture could inhibit the generation of hydrogen and methane but had little effect on the generation of carbon dioxide. The inhibition effect weakened with decreasing amount of lignin. The reason might be associated with the hydrogenation of lignin in the course of hydrolysis. The interaction between cellulose and hemicellulose was so week that it could be ignored. In addition, equations to predict gas yield were developed. The results showed that the estimated values thus calculated agreed well with the values from actual gasification experiments and the deviation of prediction from experiment for hydrogen and methane was 5.77% and 4.74% respectively.