Production Of Reducing Sugars From Biomass Hydrolyzation By Two-steps Method Of Sub-critical And Supercritical Water Process

Energy crisis and environmental problems become increasingly severe.Development and utilization of renewable energy and clean energy has been focused on by foreign scholars. Biomass as a renewable energy have great development value. Carbohydrates of biomass hydrolyzed by chemical or biological technology convert into Reducing sugar, followed by fermenting into fuels ethanol which is the most promising clean fuel.In this paper. In order to obtain reducing sugar.rice straw and corn stalks as raw materials were put into two kinds of batch reaction equipment respectively. The hydrolysis conduct of two raw materials under the conditions of supercritical/subcritical water were studied exploratory. The effect of reaction temperature, reaction time on reducing sugar production and liquefaction rate were studied mainly. The effect of solid-liquid ratio on the hydrolysis behavior wasstudied also. We designed a sub-critical low-temperature and supercritical high-temperature two-step hydrolysis process route.and Compared with supercritical one-step hydrolysis process route. Use 3,5-dinitrosalicylic acid colorimetry (DNS method) to analyze yield of reducing sugar.Experimental phenomena and results were analyzed in theory.This two raw materials hydrolyzed in low-tempreture(180-230℃.0-60min) shew Similar regularity When it comes to reducing sugar production and liquefaction rate.if investigated tne effect of reaction temperature. reaction time on hydrolysis. Maximum sugar yield all occurred at 190℃.40min under low-temperature..obtaining maximum sugar yield of rice straw and corn stalks above 21% and 24% respectively. At a fixed temperature and reaction time (190℃. 20.40.60min) increasing solid-liquid ratio to 1:40. obtain the same reducing sugar production both 20 min and 40min.In addition increasing solid-liquid ratio reduced the wastage of water. Therefore, increasing the ratio of solid is useful to cut down the energy consumption of hydrolysis.At 380℃,20s rice straw residues and corn stalk residue which abtained from Low-temperature hydrolysis as raw materials of high-temperature hydrolysis have been hydrolyzed and got the maximum yield of reducing sugar 24% and 34% respectively. Residue abtained from low-temperature hydrolysis is cellulose-rich material. Hydrolysis rate of cellulose near the critical point increases rapidly, preponderating over hydrolysis rate of oligosaccharides and monosaccharide.Accordingly hydrolyzate was accumulated. and higher yield of reducing sugar was obtained at 380℃.Rice straw and corn stalks hydrolyzed by supercritical one-step hydrolysis process route. obtained yeild of reducing sugar 32%(380℃.40s)and 41%(380℃.20s) respectively; hydrolyzed by sub-critical low-temperature and supercritical high-temperature two-step hydrolysis process route yeild of reducing sugar are 45% and 58% respectively. As compared with supercritical one-step hydrolysis process route. the total yield of reducing sugar significantly increase 13% and 17% respectively. After a low-temperature hydrolysis. the content of cellulose of raw materials increased. the crystal structure of cellulose was destruct and porosity augmented.Compared with one-step high-temperature hydrolysis a larger yeild of sugar was obtaind by two-step high-temperature hydrolysis in a short time.Based on earlier experiments.we studied the impact of CO2 on rice straw hydrolysis. Reaction system was mixed in 5.5MPa CO2 at room temperature. Raw materials are processed under the conditions at 190℃.0-50min.The results showed increased sugar production and low power consumption after the introduction of CO2. compared with pure water treatment.