Liquefaction Of Woody Biomass By Two Steps And Utilization Of The Liquefied Residue

Biomass is a kind of environmental and renewable resource,which can be converted to liquid fuel and raw chemical materials through liquefaction.In this paper,poplar sawdust was liquefied by two steps with some solvents,and the liquefied residue of the first step was used to synthesize carboxymethylcellulose sodium(CMC)with low viscosity.(1)According to the liquefaction ratio of poplar sawdust and the cellulose content of the liquefied residue,the reaction conditions of the first step liquefaction(such as catalyst,liquefacients,temperature,pressure,etc.)were optimized.When the sawdust liquefaction ratio was 40.8%,the cellulose content in the liquefied residue was 81.7%,which accounted for 95.9% in the total cellulose content of poplar sawdust,it's clear that the cellulose could be kept in the first step,while the lignin and hemicellulose were liquefied of high levels.The liquefied residue and the liquefied products were characterized by FT-IR,XRD and GC-MS.The results proved that the main component of the liquefied residue was cellulose,also contained a small amount of benzene ring and carbonyl functional groups structure through the analysis of FT-IR;and crystallinity of cellulose basically not changed after the first step liquefaction,which was maintaining the structure of the cellulose in poplar sawdust;the liquefied products contained a large amount of free phenol and phenol derivatives,a small amount liquefaction products of cellulose.(2)Using ?-cellulose as the model compound of the first step liquefied residue and isooctanol as the liquefacient to investigate the effect of reaction conditions on the second step liquefaction.With the optimum conditions,the liquefaction ratio of ?-cellulose was 99.1%;the liquefaction ratio of the first step liquefied residue was 96.4%.By the analysis of FT-IR,the possible reason for the slightly lower liquefaction rate of the latter one was that the polycondensation reaction of liquefied fragments of lignin and semicellulose of the first step liquefied residue with cellulose into solid residue which was hard to liquefied.By the analysis of TG-DTG,cellulose has been basically liquefied after the second-step liquefaction.The second-step liquefied products mainly were know as esters,ethers,heterocyclic compounds by the analysis of GC-MS.(3)The optimized reaction conditions of the synthetic of carboxymethylcellulose sodium(CMC)was studied with ?-cellulose as raw material,the degree of substitution of the CMC which was synthesized with ?-cellulose was 0.38,and the viscosity was 16.9 mPa·s;the degree of substitution of the CMC which was synthesized with the first step liquefied residue was 0.63,and the viscosity was 24.8 mPa·s.The degree of substitution of the latter one was slightly higher,inferred that the lignin fragments connected on the hydroxyl functional groups of the cellulose through the first step liquefaction,and lignin fragments were easily replaced by sodium chloroacetate after alkalization and etherification.