分子筛分步催化降解碱木素制备芳香化学品

本研究采用分步催化的方式对碱木素进行降解,即先利用氢型β分子筛(H-BEA)催化液化碱木素,再采用氢型超稳Y分子筛(H-USY)对液化后的产物进行催化降解。结果表明,相较于非催化条件下的直接降解,分步催化降解将产物中芳香化学品含量从30.6%提升到51.2%。质谱分析(MALDI-TOF)结果表明,降解途径是碱木素中的芳香五聚体被液化为三聚体再进一步降解为芳香二聚体和单体。1H NMR结果表明,第1步催化液化过程破坏了大部分C—O键,而第2步催化降解过程主要以破坏C—C键为主。气相色谱检测到的芳香单体占芳香化学品的16.2%。其中,H-BEA分子筛在液化阶段催化部分酚类烷基化,使得酚羟基的邻位或对位活性降低,防止酚类在第2步催化过程中发生缩合。

毛竹水解渣木质素氢解制备芳香化学品

以毛竹水解渣为原料,分别采用过氧化氢法和甲醇法提取木质素,在相同的反应条件下对比了两种木质素转化及产物分布的结果,并进一步优化了过氧化氢法提取的木质素的氢解转化最优条件。研究结果表明:温度为220℃,反应时间60min时,过氧化氢木质素可以全部转化为可溶物,单体收率为14.85%;甲醇法提取的甲醇木质素,转化产物中可溶物收率为96.8%,单体收率为7.13%。过氧化氢法木质素通过氢解法制芳香族化学品的效率高于甲醇木质素,此外氢解过程可以使过氧化氢木质素六元环非共轭碳氢重新还原成苯环结构,单体芳香产物中的侧链以羰基、羧基、醛基和烷烃取代基为主。

芳香化学品合成研究进展

综述了生物基呋喃衍生物转化制备多种芳香化学品的研究进展,主要包括由呋喃转化为苯、苯甲酸和邻苯二甲酸酐,由2-甲基呋喃合成甲苯和3-甲基邻苯二甲酸酐,由2,5-二甲基呋喃合成对二甲苯和3,7-二甲基邻苯二甲酸酐以及由5-羟甲基糠醛合成对苯二甲酸二甲酯。本文旨在发展从生物基平台分子制备芳香化学品提供指导意义。

木材腐朽真菌定向降解木质素为苯系芳香类化学品

对2种木材腐朽真菌降解木质素为一系列苯系芳香类化学品进行了初步研究,并与黄孢原毛平革菌进行了比较。从木材腐朽土壤样品中分离获得具有降解木质素活性的真菌11株,将其中活性最强的菌株ZS1与ZSH用于降解工业碱木质素与中性木质素。通过发酵条件的优化、降解产物种类与浓度的HPLC分析,结果发现,在初始底物浓度1.0~20.0g/L变化时,ZS1对碱木质素的降解率达到40.7%,比ZSH的大;而ZSH对中性木质素的降解率为32.3%,与黄孢原毛平革菌的降解能力相当,但比ZS1的大些。木质素能被定向降解为香草酸、苯甲酸、香草醛、苯酚、紫丁香醛、苯、对甲基苯甲醚、对甲基苯乙醚、甲苯与对二甲苯等芳香类化学品,而且不同真菌降解不同木质素的产物种类数量与浓度有所差异。这说明不同真菌对木质素的降解具有一定的底物依赖性,底物结构差异影响了降解率不同与产物种类差异,而且不同真菌降解木质素具有一定的产物定向选择性。

Sell a dummy: Adjacent functional group modification strategy for the catalytic cleavage of lignin β-O-4 linkage

The world relies on nonrenewable fossil resources, which provide various fuels, chemicals and materials. Biomass is an-other storage form of carbon and solar energy that has attract-ed great interest, mainly because of its potential as a sustaina-ble source of chemicals and fuels [1,2]. Lignin is an attractive biomass feedstock. As shown in Fig. 1, three phenylpropane units assemble into lignin with a complex three-dimensional structure and different linkages in plants [3].

Supported noble metal nanoparticles as photo/sono-catalysts for synthesis of chemicals and degradation of pollutants

This review summarizes the utilization of supported noble metal nanoparticles (such as Au/TiO2, Au/ZrO2, Ag/AgCl) as efficient photo/sono-catalysts for the selective synthesis of chemicals and degradation of environmental pollutants. Supported noble metal nanoparticles could efficiently catalyze the conversion of solar energy into chemical energy. Under UV/visible light irradiation, important chemical transformations such as the oxidation of alcohols to carbonyl compounds, the oxidation of thiol to disulfide, the oxidation of benzene to phenol, and the reduction of nitroaromatic compounds to form aromatic azo compounds, are effectively achieved by supported noble metal nanoparticles. Under ultrasound irradiation, supported noble metal nanoparticles could efficiently catalyze the production of hydrogen from water. Moreover, various pollutants, including aldehydes, alcohols, acids, phenolic compounds, and dyes, can be effectively decomposed over supported noble metal nanoparticles under UV/visible light irradiation. Under ultrasound irradiation, pollutant molecules can also be completely degraded with supported noble metal nanoparticles as catalysts.