Study On The Directional Liquefaction And Process Simulation Of Model Compound Of Cello-polysaccharides Catalyzed By Ferric Phosphate

Energy shortage and environmental pollution is an increasingly prominent contradiction in sustainable development at present.So that it is impotant to find renewable resources,which could partially replace fossil resources,and to achieve CO₂ emission reduction and green development.Lignocellulosic biomass resources have the advantages of being clean,green,rich in reserves,and renewable.For the reasons,the high efficient conversion of lignocellulosic biomass resoureces to produce fuels and high value-added chemicals has become a current research focus.The research could effectively solve the existing problems in the conversion of lignocellulosic biomass,including,the uncontrollable conversion process by thermochemistry,complex product components and difficulty to high value use.Meanwhile,it has important significance to the high-value utilization from forestry residue resources and CO₂ emission reduction.In this paper,cellulose and xylan were used as model compounds.This article studied the process of conversion of celllulose and xylan to levulinate esters and furfural in green and efficient style.Through Aspen plus software,it provided a feasible industrial solution for the separation and purification of levulinate esters and furfural,in order to provide a theoretical basis and technical support for the industrialization of lignocellulosic biomass.The main research contents are as follows:1.Using cellulose as raw materials,this part of research was exploring the target product of liquefaction conversion under different reaction conditions in a methanol/water mixed solvent system.Through the single factor analysis method,explore the influence of various factors on the conversion effect of cellulose liquefaction,mainly including the type of catalyst,reaction temperature,reaction time,the amount of catalyst and the ratio of mixed solvent methanol/water to the yield of main and by-products.The results showed that the optimal reaction conditions for producing methyl levulinate by directional liquefaction of cellulose were:the reaction temperature and time of 220℃and 2h,the water/methanol volume ratio of1:19,and the dosage of Fe PO₄ of 75%.At this time,the conversion rate of cellulose was 82.5%,the yield of methyl levulinate,levulinic acid,furfural and methyl glucoside were 52.9%,9.3%,7.6%,and 5.8%,respectively.In the study of the liquefied solid residue,crystalline Fe PO₄ was found.It shows that after the liquefaction reaction,solid Fe PO₄ was separated from the solvent system in the form of recrystallization.Therefore,the separation efficiency of catalyst reached more than 80%.2.This part investigated the law of liquefaction conversion of xylan into furfural under different reaction conditions in a tetrahydrofuran/water（volume ratio 3:1）mixed solvent system containing 0.087 5 g/m L Na Cl.Through the single factor analysis method,various factors affected the result of liquefaction conversion including:catalyst type,reaction temperature,reaction time,and the amount of catalyst.The consequents showed that the optimal reaction conditions for the produce of furfural by the directional liquefaction of xylan were:the reaction temperature of 180℃,the reaction time of 1h and the dosage of Fe PO₄ of 50%.At this time,the conversion rate of xylan was 88.3%,the yield of furfural was 82.1%and the selectivity of furfural was 92.9%.After the liquefaction reaction,Fe PO₄ was separated and then we studied the stability of cycling catalyst.In spite of repeated using for 5 times,the conversion rate,furfural yield and selectivity of xylan were reduced by 5.5%,9.3%and 3.9%,respectively.3.In this part,we designed the process simulation for the processing of methyl levulinate,levulinic acid and furfural with glucose and xylose as raw materials,using Aspen plus software.The process route aimed to achieve the separation of main and by-products,such as levulinic acid,methyl levulinate,furfural,methyl glucoside.At the same time,the reaction solvent of methanol and the extractant of trichloroethylene involved in the process should be purified and recycled efficiently,for the purpose of reducing costs.In the end,the simulated process route included three parts:reaction and pretreatment section,methyl levulinate refining section,and furfural refining section.Through the process production of levulinic acid and methyl levulinate constructed by Aspen plus,material balance calculation and calorie balance were carried out,and the final annual output（calculated by 330 days）of levulinic acid and methyl levulinate was412.07 t（purity 99.9%）,furfural was 35.52 t（purity 98.9%）.In addition,by-product the methyl glucoside was 58.81 t（purity 99.9%）.At the same time,the methanol（99.99%）and the trichloroethylene（96.31%）were basically recovered.