Study On Mechanism And Purification Of Oligosaccharides In Pre-hydrolysis Liquor Of The Dissolving Pulp From Poplar Slab

The pre-hydrolysis kraft cooking process is currently the main method for preparing dissolving pulp. Most of the hemicelluloses are dissolved in the pre-hydrolysis liquor together with lignin, it was burned in alkali recovery process, or was put into the wastewater treatment plant,which leds to the waste of biomass resources. Based on the concept of biorefinery, priority pre-hydrolysis, prehydrolyzed materials are used for pulp production. The pre-hydrolysis liquid (PHL)contains high value oligosaccharides, lignin, furfural, acetic acid, etc. In this paper, preparation dissolving pulp from poplar slab, its pre-hydrolysis liquid was analyzed at the same time, and using different purifying agent purified the PHL in order to improve lignin removal rate and oligosaccharides retention rate. The main conclusion are as follo wings:(1)The dissolving pulp from poplar slab was prepared with the pre-hydrolysis, kraft cooking and Op-Q-P three stage bleaching process. The PHL(water pre-hydrolysis liquor, sulfuric acid pre-hydrolysis liquor) were analyzed. It was found that sugars (monosaccharides and oligosaccharides) and lignin were the main components in PHL. Monosaccharides content was 14.383mg/ml, its oligosaccharides content was 13.338lmg/ml in water pre-hydrolysis liquor. In sulfuric acid pre-hydrolysis liquor monosaccharides content was 17.0369mg/ml. Its oligosaccharides content was 0.1113mg/ml.Lignin content was 9.1618g/L in water pre-hydrolysis liquor; lignin content was 10.67g/L in sulfuric acid pre-hydrolysis liquor.(2)The existence of lignin may affect subsequent utilization of oligosaccharides in the PHL. In this paper, p-DADMAC,PAC,Al2(SO4)3 were used to purify PHL, by measuring lignin removal rate and monosaccharide retention rate, and obtained the optimum amount. When water hydrolysis liquor was treated, p-DADMAC flocculation was relatively good for lignin removal rate and monosaccharide retention rate. The optimum amount of p-DADMAC was 150ppm, lignin removal rate was 52.73%, while monosaccharide retention rate were 92.04%; in dealing with sulfuric acid pre-hydrolysis liquor, Al2 (SO4)3 was better. The optimum amount of Al2 (SO4)3 was 120ppm, lignin removal rate was 13.96%, monosaccharide retention rate was 86.42%.(3) When the PH of sulfuric acid pre-hydrolysis liquor was adjusted to 6.01, lignin removal rate can reach 20.04%; when laccase dosage was 3u/ml, lignin removal rate increased from 13.96% to 53.89%.When laccase dosage of water pre-hydrolysis liquid was 2u/ml, lignin removal rate can increase from 52.73% to 71.07%.