Study On Cellulose Saccharification In Supercritical Water

At present, under the background of the reserves of the petrochemical energy getting smaller, as well as the environmental pollution and food crisis, more and more experts suggest that the energy structure of the world should be changed from the petrochemical energy to the renewable energy urgly. According to a large of documents domestic and abroad, this paper operate a series of experiments, followed by the straw saccharification in the supercritical water(SCW) with the instruments self-made. The theoretical analysis was given for the phenomena and results.Firstly, the ratios of ash, celloluse, hemicellulose and lignin in the straw were tested in chemical ways. To stduy the effects of the pressure, temprature and the ratio of water and the straw during the reaction, the straw was saccharificated in a series of pressure, temprature and the mass ratio of liquid to solid in SCW. The result of the better condition was at 23 MPa, 410℃and mass ratio of liquid to solid of 80.00:6.00.Secondly, the straw was pretreated with NaOH solution with diferenet concentration, followed by the chemical analysis of components and the scanning electron microscope (SEM), as well as X-Ray Diffraction Analysis to study the ratios of ash, cellulose, hemicellulose and lignin, the micro-morphology and the crystallization. Then the straw pretreated was saccharificated in the supercritical water. The results suggested that while the concentrations of the NaOH solution rise, the concentrations of reducing sugar first rise and then drop as well as conversion of cellulose. After the pretreatment of 3% NaOH solution, the straw saccharification in the supercritical water got a glucose concentration of 1.08g/L, while the saccharification ratio reached 2.65%.Moreover, to study the effect of catalyst on the straw saccharification in the supercritical water, the sulfuric acid, sodium hydroxide, sodium carbonate, copper sulphate, alumina, calcium carbonate and magnesium sulfate were used as catalysts during the reaction. The results showed that diferent catalysts caused diferent distribution of reducing sugar. The quantities of the reduced sugar were changed. When the quantities of H₂SO₄ increased, the quantities of glucose increased. When the quantities of H₂SO₄ reached 0.8g, The glucose got a concentration of 0.11g/L, the while the saccharification ratio reached 0.46%. It showed that while the H⁺ increased, the saccharification of cellusoe got easier. The additions of the NaOH and Na₂CO₃ cause the concentrations of reducing sugar rise and then drop. after the additions of the CuSO₄, the glucose was not found in the water-soluble after straw saccharificating, while a small number of the fructose was found. It suggested that the isomerization from glucose to fructose had occurred.