Solvent Liquefation Of Alkali Lignin For Bio-oil And Monomeric Phenols

Lignin with aromatized structure has great potential to produce high value-added chemicals.Lignin reacts at 300-400? to form small free radical fragments,hydrogen donor solvents can supply hydrogen radicals to stabilize lignin fragments,which is expected to obtain higher yields of bio-oils or phenols without any catalyst.In this paper,alkaline lignin was liquefied in a hydrogen donor solvent without molecular hydrogen and catalyst.The effects of temperature,time and mass ratio of solvent to lignin on lignin conversion,bio-oil yield and monomeric phenol distribution were evaluated.The conversion rate and hydrogen supply of the reaction solvent were investigated.Combined with a variety of instrumental analysis methods,including GC and GC-MS,the solid-liquid-gas products after lignin reaction was analyzed and quantified.Elemental analysis and Fourier transform infrared spectroscopy are used to perform preliminary structural analysis on the residual char after lignin reaction.The main conclusions were following as:1.9,10-dihydroanthracene significantly increased the yield of monophenols.When the mass ratio of 9,10-dihydroanthracene to lignin is 2:1,it is enough to supply hydrogen.Guaiacol is the main substance in the monophenol products,which is the intermediate product of lignin depolymerization,Its methoxy side chain is easy to break at high temperature.Under the reaction conditions of 350?,8 min and 1:2 AL-DHA mass ratio,the yield of monophenols reached the maximum value of 7.59 wt.%,and the conversion rate of hydrogen solvent was 55.72%.2.When 9,10-dihydrophenyl was used as the hydrogen solvent,the reaction condition was that the added amount of the hydrogen solvent was twice that of lignin,the reaction time was 10 min,the reaction temperature was 350?,and the yield of monophenol was 5.27 wt.%.The liquid yield was 28.85 wt.%,the gas yield was 2.56 wt.%,the solid yield was 68.58 wt.%,and the conversion rate of hydrogen solvent was 20.98%.3.When 1,2,3,4-tetrahydrocarbazole was used for hydrogen solvent,the mass of the hydrogen solvent was 2 times that of lignin,,the reaction time was 8 min,the reaction temperature was 350?,the yield of monophenol was 6.81 wt.%,the yield of liquid was 31.38 wt.%,the yield of gas was 3.02 wt.%,and the yield of solid residue was 65.50 wt.%.4.A structural analysis of the lignin residual char during the reaction revealed that prolonging the reaction time and increasing the amount of hydrogen donor solvent added,the H and O content in the lignin residual char decreased,and the C content increased,1600 cm-1(Car=Car)absorption peak increases,the absorption peak at 1520 cm-1(Car-Car)decreases,the degree of condensation of lignin increases,the bond between aromatic compounds breaks,and it transforms into small molecules.