A Continuous Hydrothermal Saccharification Approach of Rape Straw Using Dilute Sulfuric Acid

The fossil fuel crisis in the world has raised much concern on developing biomass energy. Fermentable sugars are an important product which can be converted to bioethanol. Although sulfuric acid saccharification is a good method for breaking lignocellulose biomass, efficiency is not well-promoted in dilute acid, as many fermentation inhibitors are co-produced. A continuous saccharification approach was established in this study to reach high saccharification efficiency and low toxicity of reducing sugar (RS). The dilute H2SO4 was taken as flow phase in this process with temperature gradient elevation. Each sample of 250 ml was taken when temperature elevated from 60 to 230 A degrees C (temperature interval 20-30 A degrees C). Under optimum conditions, the maximum RS yield ratio reaches 53.4 %. Furfural is detected in the hydrolysate, with a concentration less than 1.06 g/l. The optimized saccharification conditions were achieved at a flow rate of 25 ml/min and with H2SO4 concentration at 1.0 %. Operation parameters were investigated including acid flow rate and acid concentration. The composition of rape straw is analyzed, and the material balance is studied in the optimized conditions. In addition to SEM, FT-IR analysis techniques are used, and the results show that the hemicellulose and cellulose in the rape straw can be fully converted to RS, while the change in lignin amount is negligible. This method is a novel and promising technique for high yield of RS, as it is accompanied with a low content of bio-inhibitor.