Comparison Of Various Biomass Oriented Dismantling Processes And Study On Products Utilization

Biomass energy is considered as an ideal substitute for fossil energy due to its advantages of renewable energy and abundant resources.Broadleaf wood and gramineous plants are common raw materials of biomass energy.Reasonable and high-value development and utilization of biomass energy is conducive to reducing the global energy crisis.The premise of its efficient development and utilization is to disassemble and separate its cellulose,hemicellulose and lignin green and efficiently.P-toluenesulfonic acid(p-TsOH)can effectively separate lignin from biomass under mild conditions,so it is expected to improve the utilization efficiency of biomass in the process of biomass fractionation.In this paper,poplar,eucalyptus and rice straw were used as raw materials,the pretreatment methods including p-TsOH pretreatment,ethylene glycol collaborative p-TsOH pretreatment,steam blasting and ethylene glycol,p-TsOH co-treatment,were used to explore the high efficiency and green pretreatment process of biomass under mild conditions,and to explore the influence of structural differences of different biomass on the pretreatment effect.At the same time,the separation products of biomass were used rationally.The main research contents and results are as follows:The pretreatment effect of p-TsOH concentration,temperature and time on the three kinds of biomass was investigated by using p-TsOH under 100℃.It was found that the concentration of 70-75%,the temperature of 80-90℃,and the time of 80-90 min,the three kinds of raw materials have good component separation effect.The differential degradation of hemicellulose by p-TsOH pretreatment was found for the first time.After pretreatment,the hemicellulose removal rates of poplar and eucalyptus reached 71.61%and 75.88%,respectively,while the hemicellulose removal rate of straw was only 18.46%,and the cellulose retention rate of the three raw materials reached more than 90%.The lignin removal rate was above 75%.According to the results of enzymolysis experiment,the saccharification rate and sugar recovery rate of pretreatment straw was 86.99%and 77.00%,respectively,which were much higher than those of poplar and eucalyptus.SEM,XRD,FTIR,XPS,EA and 2D-HSQC NMR were used to analyze the structural composition of hemicellulose and lignin in the three raw materials before and after pretreatment,and the fractionation mechanism of biomass was analyzed.Compared with poplar and eucalyptus,the hemicellulose structure of straw has less side chain structure.Moreover,it has a high content of lignin carbohydrate(LCC),which makes it difficult to be removed in the pretreatment process.Ethylene glycol coordinated p-TsOH and steam blasting combined with ethylene glycol p-TsOH were used to pretreat poplar wood.The effects of mass fraction of ethylene glycol p-TsOH,pretreatment time and pretreatment temperature on the pretreatment effect were investigated.The optimal process conditions of ethylene glycol coordinated p-TsOH pretreatment were obtained as follows:20%EG-PTSA,temperature 90℃,pretreatment time 4 h.Under these conditions,the lignin removal rate was 88.51%,the cellulose retention rate was 77.43%and the hemicellulose removal rate was 75.47%.Temperature had the greatest effect on lignin removal,followed by mass fraction,and time had the least effect.After the steam blasting combined with EG-PTSA pretreatment process was introduced,the optimal conditions were obtained:blasting pressure 1.6 MPa,pressure holding time 80 s,10%EG-PTSA,temperature 90℃ and pretreatment time 100 min,and The hydrolysis rate of solid residue increased from 20.26%to 72.47%.The morphology,structure and crystallinity of the raw material and the pre-treated solid residue were characterized by SEM,XRD and FTIR.The results showed that ethylene glycol combined with p-toluenesulfonic acid pretreatment and steam blasting combined with ethylene glycol and p-toluenesulfonic acid pretreatment are efficient and green dismantling and separation methods,which mainly removes lignin and hemicellulose from poplar fiber,and has little damage to cellulose,which can improve the availability of cellulase and increase the efficiency of subsequent enzymatic hydrolysis.Nanocellulose was prepared by enzymolysis assisted ultrasonic crushing method,and 200-300 nm nanocellulose was prepared by cellulase using the separation residue product obtained in the pretreatment process.The lignin nanoparticles were prepared by glycol and acid precipitation.The nanometer cellulose and lignin nanoparticles were analyzed and characterized by laser nanoparticle size analyzer,zeta potentiometer and SEM to ensure the size controllability and stability,which provided a feasible scheme for high-value utilization of pretreatment resolution products.