Study On Liquefaction Of Woody Biomass In γ-valerolactone/1-Octanol

The extensive use of fossil fuels has led to increasingly serious environmental pollution problems.The clean energy and high value-added chemicals obtained from green renewable biomass resources has received much attention and liquefaction is one of the important and effective methods for the thermochemical conversion of biomass.However,the traditional liquefaction technology has some defects,such as the strong corrosiveness of inorganic acid catalyst,the high toxicity of the liquefaction solvent phenol,the long time and high energy consumption,which does not meet the development requirements of green chemical industry.In this paper,a new green liquefaction technology of sawdust was studied from three aspects of liquefaction solvent,catalyst and enhancement of heat and mass transfer using fir sawdust as a model compound of woody biomass.The research aim is to provide a theoretical basis and some practical experiences for the effective utilization of biomass resources.The main contents and results are as follows:1.The liquefaction process of sawdust heated in oil bath（interway heating）was investigated inγ-Valerolactone（GVL）/1-Octanol solvent using sulfuric acid as catalyst.The experimental results showed that under the optimum conditions of catalyst concentration,0.6 mol·L^-1;reaction temperature,150℃;sawdust/solvent mass ratio,1:6;reaction time,60 min;GVL/1-Octanol=4:6,the liquefaction rate reaches the highest value of 76.07%.The addition of GVL to the liquefaction process can promote the decomposition and degradation of woody biomass to a certain extent,but also improve the liquefaction ratio of raw materials and the generation of high added-value phenolic compounds.2.The effect of ultrasonic-microwave（UW-MW）on sawdust liquefaction was investigated by using UW-MW technology instead of mechanical stirring and interwall heating.The experimental results showed that under the optimum conditions,the liquefaction yield of sawdust is 81.17%.The reaction time is reduced by 53.33%compared with the interwall heating liquefaction process.The assistance of UW-MW technology can remarkably enhance the heat and mass transfer in biomass liquefaction.3.Using the six kinds of synthesized acid ionic liquids instead of H₂SO₄ catalysts,the sawdust liquefaction asssted with UW-MW technology was studied in GVL/1-Octanol=4:6 mixed solution.The results indicated that the order of catalytic activity of ionic liquids is[HSO₃-p TEA][CF₃SO₃]>[HSO₃-b TEA][CF₃SO₃]>[HSO₃-p TEA][HSO₄]>[HSO₃-b TEA][HSO₄]>triethylamine trifluoromethanesulfonic acid>triethylamine sulfuric acid.The ionic liquid[HSO₃-p TEA][CF₃SO₃]exhibited the best catalytic performance and the highest liquefaction ratio reaches 75.96%that slightly lower than that of sulfuric acid.4.The liquefaction mechanism of woody biomass in GVL/1-Octanol mixed solution was studied by using microcrystalline cellulose,xylene and alkali lignin as the model compounds of cellulose,hemicellulose and lignin,respectively.The results showed that the main degradation paths of cellulose and hemicellulose liquefaction are:polysaccharide polymers→small molecular carbohydrate compound→furfural→esters,carboxylic acids;the main path of lignin liquefaction are:lignin macromolecular polymers→phenylpropane compound→aromatics,aldehydes,alcohols,etc.In addition,GVL can effectively improve the liquefaction of woody biomass,cellulose and lignin.