Study On The Mechanism Of Pyrolysis Liquefaction Of Biomass-based Cosolvents Based On Components

Biomass pyrolysis is a valid way to convert biomass into liquid fuel "bio-oil". It is one of the advanced technologies in respect of biomass utilization. However,the industrial utilization is quite limited due to the complex composition and the unstable properties of generated bio-oil, which are ascribed to the lack of sufficient understanding of the related reaction mechanisms. Based on the multi-components of biomass, an integrated research of co-solvent pyrolysis mechanism of biomass was presented in this paper.Using cellulose, hemicelluloses and lignin as raw material, the co-solvent pyrolysis behavior and reaction kinetics in polyhydric alcohols (PEG 400 or glycerol) was studied by TG-FTIR. Compared with co-solvent pyrolysis process, final residues of biomass pyrolysis were higher, which indicates the co-solvent pyrolysis process is more beneficial for biomass degradation,and the efficiency was better when using glycerol as solvent.Based on Starink and Malek methods, kinetic parameters and mechanism functions of biomass co-solvent pyrolysis were obtained. And a consistent conclusion was drawn.The product composition and distribution of biomass co-solvent pyrolysis was investigated by using an analytical pyrolyzer coupled with Gas Chromatography and Mass Spectrometer (Py-GC/MS). The results showed that the main products of cellulose co-solvent pyrolysis were composed of furans,esters,alcohols and pyrans. The reasons of the difference of product distribution of cellulose co-solvent pyrolysis assisted by the two different polyhydric alcohols (PEG 400 or glycerol) were analyzed,and the results showed that the generated bio-oil has higher quality when using PEG 400 as solvent. The main products of xylan were composed of furans, esters, alcohols and ethers. In comparison with co-solvent pyrolysis process in glycerol, the xylan produced more ketones,aldehydes and fewer esters when using PEG 400 as solvent. The main products of lignin co-solvent pyrolysis assisted by the two polyhydric alcohols were phenols,esters, alcohols and ethers. In contrast to the co-solvent pyrolysis associated by glycerol,the pyrolysis process of lignin in PEG 400 generated more phenols and fewer esters.From the perspective of liquid fuel, the biological bio-oils obtained from lignin co-solvent pyrolysis assisted by glycerol are of higher quality. But the phenols generated when using PEG 400 as solvent, are also potential resources for novel materials.Based on the simplex lattice method,synthesized biomass samples were prepared by mixing the three main components. The DTG curve of each component of biomass co-solvent pyrolysis has no evident characteristic. But they showed the inneglectable interactions between the components. The synergistic effect of three-components of biomass is correlated with the reaction temperature and proportion of each component.Then typical proportions were selected and synthesized samples were prepared accordingly. The product composition and distribution of synthesized samples co-solvent pyrolysis assisted by PEG 400 was investigated by Py-GC/MS. The main products were composed of more phenols, esters, alcohols but fewer acids, ketones and furans. The comparison study of single component and synthesized biomass co-solvent pyrolysis indicated that higher percentage of lignin in synthesized biomass promotes the formation of acids,and the production of ketones and furans were also influenced by the mixing ratio of three-components. The existence of cellulose and hemicellulose restrains the yield of phenols during lignin co-solvent pyrolysis. More esters were obtained from synthesized samples co-solvent pyrolysis, different proportion of three-components promote the formation of esters.