Low temperature deoxidization of biomass and its release characteristics of gas products

With a first attempt of extension for torrefaction temperature aiming to reducing more oxygen, low temperature deoxidization of cellulose, hemicellulose, lignin, corn stalk and cotton stalk were performed at various temperatures (200, 230, 260, 290, 320, 350 and 390 °C) respectively. The deoxidization properties of both solid and gas products were investigated. As could be inferred from the results obtained that the main deoxygenation temperature range of cellulose, xylan, corn stalk and cotton stalk were 290-320 °C, 230-260 °C, 260-390 °C and 260-350 °C respectively. The deoxidation effect of lignin was not obvious during 200-390 °C, only 14.80% oxygen was removed at 390 °C. At lower temperature (200-320 °C), the oxygenated gas products dominated by CO2 and H2O were mainly from hemicellulose. In the high temperature range (350-390 °C), cellulose deoxidation was mastery reaction and CO2 was the main product. The release kinetic analysis of CO2 and CO during 200-390 °C had been performed for the first time, and as could be inferred from the results obtained that the activation energies for CO2 and CO release of cellulose, lignin, cotton stalk, corn stalk during low temperature deoxidization were 61.32, 38.41, 43.38, 38.62 kJ/mol and 120.62, 60.55, 83.24, 72.27 kJ/mol, respectively. The release activation energies of hemicellulose in the temperature ranges of 200-290 °C and 320-390 °C were 63.32 and 10.21 kJ/mol for CO2 and 115.75 and 20.65 kJ/mol for CO respectively.