The influence of CO2 on biomass fast pyrolysis at medium temperatures

Abstract

In order to increase the economic potential, the pyrolysis gas product of CO2 was recycled as carrier gas for biomass fast pyrolysis at medium temperatures. Distribution and characterization of products were investigated under five CO2 concentrations (0%, 10%, 20%, 50%, and 100%). It was found that CO2-containing atmospheres resulted in higher yields of char and oil while lower gas yield. The CO2 atmosphere inhibited H-containing and O-containing functional groups removing from char to volatiles by reacting with the char active center. CO2 can react with the volatiles promoting the generation of CO. Phenols were the most part in bio-oil, and the carrier gas CO2 could promote more oxygen converting into liquid products at a temperature higher than 550 °C. For rape straw, corn stalks, and camphor wood, CO2 has a similar effect on the pyrolysis products, promoting the generation of char and CO, while inhibiting the production of H2 and CH4 in gas.