Effect of volatiles interaction during pyrolysis of cellulose, hemicellulose, and lignin at different temperatures

Secondary reactions, including those caused by the interaction of volatiles, are unavoidable during biomass pyrolysis. This study investigated the interactions of the volatiles from cellulose, hemicellulose, and lignin in a two-stage fixed bed reactor without a pre-mixed feedstock. The yield distribution of the products and gases, and the composition of liquids were all affected by the interaction of the volatiles. The interactions increased the gas yield but inhibited the liquid yield. However, when temperature increased, the interactions weakened in the presence of cellulose but increased when hemicellulose and lignin were used. Independent of feedstock, the interactions also generated CO2 and H-2 at 400-700 degrees C and inhibited the generation of CH4 and phenols below 500 degrees C and 400-700 degrees C, respectively. However, several feedstock-dependent interactions were also observed: 1) CH4 generation increased at temperatures above 600 degrees C in the presence of lignin volatiles; 2) both hemicellulose and lignin volatiles resulted in significant amounts of cellulose-derived sugars at temperatures above 500 degrees C; and 3) hemicellulose volatiles increased decomposition of cellulose volatiles, while the latter inhibited the decomposition of lignin volatiles, when the temperature was below 500 degrees C.