Kinetics study on non-isothermal thermochemical liquefaction of corncobs in ethanol-water solution: Effect of Na_2CO_3 catalyst concentration

摘要

Modeling of the non-isothermal liquefaction kinetics of corncobs in ethanol-water solution was studied. The actual reactions are quite complex and involved many organic compounds. For the sake of simplification, the kinetic models were developed based on four lump products of reactions, i.e. bio-oil, gas, solid and volatile. Three possible kinetics models were developed and compared. The unknown kinetic parameters of each model were calculated by a nonlinear least square method. Model 2 was found to be the best one closely matching with the experimental yield data obtained from liquefaction of corncobs. In model 2 the reaction mechanism was assumed that biomass (corncobs) first decomposed into bio-oil, followed by decomposition of bio-oil into volatile products and finally volatile products decomposed into gaseous products. The batch liquefaction of corncobs in the ethanol-water solution experimentally conducted in the 150 mL autoclave reactor equipped with magnetic stirrer. It was found that the concentration of sodium carbonate catalyst significantly increased the yield of bio-oil. The highest bio-oil yield of 53.5% achieved experimentally with the ethanol concentration of 20% and the sodium carbonate catalyst concentration of 10% by weight of biomass at 8 MPa and 280°C. However, the catalyst concentration of 5% by weight of biomass is preferred for economic reasons.