Research Of Circulation-enhanced Hot-water Pre-hydrolysis Of Eucalyptus

Based on the idea of the integration of biorefinery with pulp and paper,in order to take advantage of the catalytic action of the acidic compositions in the hot-water pre-hydrolysate to separate hemicelluloses from wood more efficiently and make full use of biomass resources,the eucalyptus powder was taken as raw material to discuss the extraction effectiveness of each chemical component of eucalyptus powder during the circulation-enhanced pre-hydrolysis for which the hot-water pre-hydrolysate was mixed with water according to different circulation rate to produce pre-hydrolysis media.The production of each monosaccharide,oligosaccharides,organic acids,furfural,HMF and acid soluble lignin in the circulation-enhanced pre-hydrolysate and changes of the each monosaccharide,lignin and acetyl groups of eucalyptus powder before and after pre-hydrolysis had been discussed.The recycling of the circulation-enhanced pre-hydrolysate and circulation of thus produced pre-hydrolysate had been simple studied and the positive and negative effects brought by the repeatedly recycling of pre-hydrolysate had been assessed.In this study the primary work are as follows:The hot-water pre-hydrolysis temperature was optimized under the conditions of holding time of 60 minutes and liquor to wood powder ratio of 6:1.The result showed that the total content of each saccharide reached the maximum in the hot-water pre-hydrolysate at 190?.But the extraction rates of each saccharide increased with the increasing of pre-hydrolysis temperature from solid phase analysis.This showed that the degradation rate of each saccharide increased obviously when the pre-hydrolysis temperature was higher than 190?.So the optimum pre-hydrolysis temperature was 190? and the concentration of xylose in the hot-water pre-hydrolysate was 22.21 g/L at the temperature.The first circulation-enhanced pre-hydrolysis in which the hot-water pre-hydrolysate made in different holding times was mixed with water according to different circulation rate to produce pre-hydrolysis media for the corresponding time pre-hydrolysis under the optimum pre-hydrolysis temperature of 190? and the liquor to wood powder ratio of 6:1 had been studied.The result showed that the content of organic acids especially acetic acid in the circulation-enhanced pre-hydrolysate could promote the extraction of each chemical component of eucalyptus powder and the degradation rate of extracted saccharides at the same time increased with the increasing of holding time and circulation rate.The extraction of galactose,glucose and Klason lignin was also affected by the inhibition of complexation reaction between H and the OH of acid soluble lignin and other substances.In the holding time of 60min,the content of xylose reached the maximum at each circulation rate and it could reach 31.35g/L at circulation rate of 60%,so the optimum holding time was 60min.The first circulation-enhanced pre-hydrolysis in which the hot-water pre-hydrolysate made at different pre-hydrolysis temperature was mixed with water according to different circulation rate to produce pre-hydrolysis media for pre-hydrolysis at the corresponding temperature in the optimum holding time of 60min and liquor to wood powder ratio of 6:1 had also been studied.The result showed that the content of organic acids in the circulation-enhanced pre-hydrolysate also increased with the increasing of pre-hydrolysis temperature and circulation rate,and the extraction of each chemical component of eucalyptus powder increased obviously.The extraction of galactose,glucose and xylose was also affected by the inhibition of complexation reaction between H and the hydroxyl,so it increased firstly and then decreased during the circulation-enhanced pre-hydrolysis process with the circulation rate increasing at each pre-hydrolysis temperature.The total content of each saccharide in the circulation-enhanced pre-hydrolysate increased with the increasing of pre-hydrolysis temperature and circulation rate.When the pre-hydrolysis temperature was higher than 170?,the total content of xylose was relatively higher,so it was favorable for the separation and purification and its further use.The recycling of the first circulation-enhanced pre-hydrolysate and thus produced second circulation-enhanced pre-hydrolysate had been studied too.The result showed that the extraction of each chemical component of eucalyptus powder increased with the increasing of circulation times.Each chemical componens in pre-hydrolysate had certain accumulation effect,but the effect of accumulation was unobvious.The extraction rate of sugars derived from hemicelluloses reduced with the increasing of tannin dosage in pre-hydrolysis media,while the decomposition rate of pentose and hexose reduced in the meanwhile.