Microwave/Chemistry Pretreatment For Fermentable Reducing Sugar From Straw

With the intensification of oil shortage, the researches of renewable fuels and chemical resources have received much attention. Cellulosic ethanol based on agricultural straw lignocellulose is considered as one of the most promising fuels due to its low cost, relative detergency, easy storage and transportation. Compared with other methods of lignocellulose hydrolysis, the enzymatic hydrolysis possesses the advantages of mild reaction conditions, no corrosion and environmental friendliness, so it is applied widely. However, the main difficulty is the low accessibility of enzymes to the cellulose due to the complex structure of lignocellulose. Therefore, pretreatment of lignocelluloses materials, to improve hydrolysis efficiency by removing some components from lignocellulose, is a critical process in the production of cellulose ethanol. Large removal ratio of lignin benefits to enzymolysis reaction.Microwave/NaOH/Na₂S, microwave/organic acid and microwave/NaHCO₃ were investigated in the paper. The influence of solid-to-liquid ratio, irradiating time, microwave intensity, treated agent and catalyst concentration on the removal ratio of lignin was discussed. And three kinds of optimal conditions were obtained. After pretreatment, the product was further hydrolyzed by cellulase. Scanning electron microwave, spectrophotometer, and High Performance Liquid Chromatography were adopted for the research of micro-morphology, reducing sugar productivity and category. Enzyme hydrolysis dynamic model of lignocellulose pretreated was setted up by enzyme hydrolysis dynamic experiment.The results indicated that rice straw of Microwave/NaOH/Na2S pretreatment was treated better under optimal conditions (0.5%～1%treated agent, 385W microwave intensity, 5min irradiating time, and 0.1%～0.2% catalyst concentration), and the optimum reducing sugar concentration was 51.52g/L; the optimum reducing sugar concentration of microwave/propionic acid and microwave/acetic acid was 44.37g/L and 39.57g/L under optimal conditions (25% treated agent, 1: 15 solid-liquid ratio, 230W microwave intensity, 5min irradiating time, and 1.2% catalyst concentration); the optimum reducing sugar concentration of microwave/propionic acid and microwave/acetic acid was 44.37g/L and 39.57g/L under optimal conditions (25% treated agent, 1: 15 solid-liquid ratio, 230W microwave intensity, 5min irradiating time, and 1.2% catalyst concentration); the optimum reducing sugar concentration of microwave/NaHCO₃ was 49.17g/L under optimal conditions (3% treated agent, 1: 20 solid-liquid ratio, 540W microwave intensity, 4min irradiating time, and 1.2% catalyst concentration). SEM images reveal that the surface of rice straw changed noticably when the three kinds of pretreatment method was adopted; parameters and expressions of enzyme hydrolysis dynamic were determined and built.