Preparation Of Phenolic Compounds By Liquefaction Of Lignin In Supercritical Methanol

Because of the increasing depletion of fossil energy and the deteriorated environmental pollution.we need alternate sources to meet our demands and to produce chemicals that are not only renewable and sustainable but also environmental friendly.Lignin is the only natural renewable resources which can directly provide aromatic ring structure.If lignin can be degrade into small molecule phenolic compounds and has similar chemical activity and solubility as phenol,lignin can be used as a substitute for phenolic resin in the synthesis of phenolic resin.This thesis first discussed optimized liquefaction process of lignin.Then studied the mechanism of liquefaction of lignin in the supercritical methanol to provide theoretical guidance for industrial production of phenolic.The research of single factor of lignin by using Ce-modified Cu-Zn-Al as catalyst was conducted in supercritical methanol.Results showed that the liquefaction rate of lignin increased with the increase of reaction temperature,the increase of reaction time and the increase of initial pressure.The liquefaction products of lignin were analyzed.The research showed that increasing the reaction temperature favorseds the formation of phenolic compounds,but the secondary reaction of phenols at 340?resulted in a decrease in phenolic yields.Increasing the reaction time did not significantly increase the yield of phenols.The coupling effect of lignin was studied by the ratio of different lignin and cellulose and hemicellulose.It was found that the liquefaction conversion of cellulose and hemicellulose to lignin in supercritical methanol can be obtained by superposition.The liquefaction product analysis showed that cellulose and hemicellulose had no significant effect on phenolic formation.The determination of typical cellulose biomass components was measured using elemental analysis,industrial analysis,and component analysis.Results show that sawdust was easier to degrade than walnut shells.The liquefaction products of sawdust and walnut shell were mainly phenols,alcohols,ketones and aldehydes,and a small amount of furan.The alcohols,ketones and aldehydes are mainly produced by the reaction of cellulose and hemicellulose in the biomass,while the phenols are liquefied by lignin.Though the increase in temperature is favorable for the degradation of lignin,the higher reaction temperature and longer reaction time will decrease the yield of the phenolic.The catalytic liquefaction was carried out under the optimum conditions using phenol,guaiacol,2,6-dimethoxyphenol and guaiacol glycerol-p-guaiacyl ether as the materials.The results showed that Ce-modified Cu-Zn-Al catalyst was selective for the cleavage of methoxy bonds.In the absence of catalyst,guaiacol and 2,6-dimethoxyphenol could only react with a small amount of methanol.Adding the catalyst the methoxy bond and the guaiacol and 2,6dimethoxyphenol reacted with methanol to get polymethyl phenol.The catalyst promoted the dehydration condensation reaction of phenil with methanol.The ?-O-4 bond and branched chain of Guaolin-based glycerol-?-guaiacyl ether ruptured in the reaction and transformed to methyl phenol and other phenolic products.