麦草催化热化学液化产物的组成分析

ANALYSIS ON CONSTITUENTS OF LIQUEFIED PRODUCTSFROM WHEAT STRAW

麦草和纤维素、木质素等原料分别在乙二醇反应介质中,以浓硫酸/苯酚为催化剂进行液化反应。分析了液化产物组成,探讨了液化过程中各成分的液化情况。实验表明:麦草中木质素组分在酸性条件下酚化降解,生成一系列单体、二聚体和多聚体,纤维素则最终降解生成乙二醇缩 2 羰基戊酸乙酯。元素分析显示,麦草、碱木质素液化残渣主要成分为灰分,且灰分中主要成分为SiO2。残渣中碳的含量比原料有显著增加,显示原料在反应条件下发生了炭化。测定了产物的相对分子质量分布,发现随着反应的进行,降解和缩合同时发生,从而导致相对分子质量分布变宽。

Liquefactions of wheat straw,soda lignin and cellulose were conducted respectively in ethylene glycol in the presence of sulfuric acid and phenol as catalyst.Suitable wheat straw/phenol ratio and proper sulfuric acid concentration were 7∶3 and 3% (by mass) respectively.The minimum residue content was 4.6% obtained at 160 ℃ and 70 min.Mw and the Mn of the liquefaction products obtained at 60 min were 3 050 and 1 270 respectively.Relative molecular mass distribution became broader as the reaction was prolonged,indicating condensation occurred simultaneously with degradation of lignin.Addition of phenol suppressed the recondensation of lignin fragment formed during liquefaction procedure. Liquefaction products of cellulose and soda lignin were characterized by IR,13C NMR and ESIMS respectively.It was found that lignin was phenolated in acidic medium and degraded to monomers,dimers and oligomers.Cellulose was finally converted into 1,3dioxolane ethyl valerate.Major component of liquefaction residue was ash,especially SiO2.