生物质加压液化制备甲基糖苷与酚类物质

以甲醇为液化剂、浓硫酸为催化剂,对竹子、杨木、松木和桉木四种生物质原料的加压液化进行了实验研究。结果表明,在200℃下反应30 min后,这些生物质原料可转化得到气体、固体残渣和液体生物油三种产品,且竹子的液化率最高。将竹子液化产物进一步分级处理,得到烷基多糖苷和木素解离多酚两类化学品。其中,多糖苷产品的主要成分为己糖苷类化合物,占83.38%(质量分数);多酚类产品的主要成分为4-乙基-2-甲氧基苯酚、丁香酚和3,4-二甲氧基苯酚等,占65.79%(质量分数)。同时,根据原料的物质构成和液化油的组成结构分析,提出了液化反应的机理:纤维类生物质中的纤维素和半纤维素在酸性条件下发生醇解反应生成甲基糖苷,小部分甲基糖苷进一步转化生成乙酰丙酸甲酯;原料中的木质素在降解过程中,由于酚羟基和甲氧基的供电子效应,使Cα-Caromatic键发生断裂,生成苯酚、愈创木酚等酚类物质。

Preparation of methyl glucosides and phenols through the liquefaction of biomass with methanol under high pressure

The liquefaction of ligno-cellulosic biomass materials of bamboo, poplar, pine and eucalyptus woods was investigated in methanol under high pressure with H₂SO₄ as catalyst. The results indicated that the biomass materials are converted into bio-gas, solid residue and bio-oil after reaction at 200 ℃ for 30 min. The bio-oil can be further separated into a variety of high value-added products such as alkyl polyglycosides, levulinate acid esters, and polyphenols. Alkyl polyglycosides is the main component of the liquefied products and accounts for 83.38% by weight; besides, phenolic products are mainly composed of 4-ethyl-2-methoxyphenol, eugenol and 3, 4-dimethoxyphenol, which account for about 65.79% by weight. Considering the molecular structure of lingo-cellulosic materials, it was proposed that cellulose and hemicellulose are transformed to alkyl glucoside, levulinate esters, etc. with methanol catalyzed by sulfuric acid under high pressure. Due to electron donating effects of phenolic hydroxyl and methoxy groups, guaiacol, phenol and a series of phenolic compounds are formed through the cleavage of C-C bond of guaiacyl units in lignin.