【作者】 唐仕荣；

【导师】 宗志敏；

【作者基本信息】 中国矿业大学 ， 化学工艺， 2009， 博士

【摘要】 目前能源和环境问题已成为全球关注的焦点,而生物质以其产量巨大、可储存和碳循环等优点已引起全球的广泛关注,开展生物质的高效转化利用对减少环境污染、减轻对化石燃料的依赖以及促进经济的可持续发展等方面具有积极的意义。以玉米秆为原料,在超临界甲醇解聚工艺研究的基础上,对解聚产物采用“分级蒸馏—分级萃取—高速逆流色谱制备分离—GC/MS分析”的方法进行了系统的分离与分析,以期为玉米秆的高效转化和产物的资源化利用提供理论依据。通过单因素和正交试验对解聚工艺中溶剂种类、反应温度、反应时间、溶剂用量及高压釜内残存空气除去方式等因素进行了探讨,确定了最佳解聚工艺:5 g玉米秆加20 mL甲醇,采用N2置换方式除去高压釜内残存的空气,300°C下反应1 h,残渣率最低26.9%。解聚液体产物的FTIR和GC/MS分析表明其成分非常复杂,含酯、酚、酮、烃及醚等类化合物,甲醇解聚产物中38.8%的甲酯类化合物,乙醇解聚产物中42.7%的乙酯类化合物和丙酮解聚产物中22.0%酮类化合物等信息揭示了溶剂直接参与了玉米秆的解聚反应。通过分级蒸馏实现了解聚产物的简单分级,轻质馏分为pH值接近中性的均相体系,物种信息比较简单,以低碳链的甲酯、酮、酚和醚等类化合物为主,总热值与解聚原液的总热值相近,表明轻质馏分可以作为燃料使用。稳定性实验表明,各馏分中的物种信息随时间而不断增多。正己烷、四氯化碳、苯、甲醇和丙酮的分级萃取实现了蒸馏残渣的初步分离,正己烷萃取物中含大量的轻质弱极性酯类化合物,四氯化碳萃取物中含较多的杂环类化合物;苯萃取物中富含芳烃和烷烃等类化合物,甲醇和丙酮萃取物中无GC/MS可检测信息。将高速逆流色谱技术应用于解聚产物的分离与分析,通过HPLC确定了氯仿-四氯化碳-甲醇-水(1:3:3:2,v/v)、正己烷-乙酸乙酯-甲醇-水(3:5:3:5,v/v)、乙酸乙酯-正丁醇-水(4:1:5,v/v)和乙酸乙酯-正丁醇-水(4:1:5,v/v)溶剂体系分别为蒸馏剩余液体、残渣的正己烷、四氯化碳和苯萃取物HSCCC制备分离的起始溶剂,采用步进方式洗脱,分别得到了12、6、12和12个逆流峰,HPLC和GC/MS分析表明各组分得到了明显富集,物种数量显著减少,所有样品的GC/MS可检测物种数比直接分析多很多,分别检测到159、222、207和125种,以酯、酮、酚和烃类化合物为主,但存在明显的种类差异。GC/MS分析纯度较高的化合物有11种,包括4种酮,4种酯,2种酚和1种酰胺。这些丰富的物种信息和较纯的化合物为从重质组分中获取高附加值化学品提供了一条潜在的途径。建立的“分级蒸馏—分级萃取—高速逆流色谱制备分离—GC/MS分析”适用于从轻质组分到中等重质组分,从弱极性组分到中极性组分的分离与分析的研究方法,丰富了生物质解聚产物中有机组分的分离与分析的研究方法。更多还原

【Abstract】 At present, energy crisis and environmental issues have become the focus of global concern, while the biomass caused widespread concern around the world for its advantages of great production, storage and carbon cycle. It has positive significance to research in efficient conversion of biomass for decreasing environmental pollution, dependence on the fossil fuel and promoting the economic sustainable development.On the bases of the research on depolymerization technology of cornstalk powders in supercritical methanol, the depolymerization product was separated and analyzed systematically by the way of“graded distillation-fractional extraction-separation with high-speed countercurrent chromatography-GC/MS analysis”with a view to providing a theoretical basis for efficient conversion of cornstalk and utilization of product.Effects of solvent species, reaction temperature, reaction time, solvent amount and methods of removing air in the autoclave on depolymerization of cornstalk were investigated by single factor and orthogonal test. The optimum conditions were identified as the follows: 5 g cornstalk with 20 mL methanol was conducted at 300°C for 1h with substitute mode of nitrogen to remove any trapped air, and the residue rate decreased to 26.9%. The depolymerization product was analyzed with FTIR and GC/MS. The results showed that its components were quite complex, and there are a majority of oxygen-containing organic compounds which include esters, phenols, ketones, hydrocarbons, aethers and other compounds in the depolymerization product. The relative content of methyl esters was 38.8% in the depolymerization product of supercritical methanol, the relative content of ethyl esters was 42.7% in the product of supercritical ethanol, while the content of ketones was 22.0% in the product of supercritical ketone. These facts indicate that solvents involve in the depolymerization of the cornstalk powders respectively.The depolymerization product was fractioned by fractional distillation. The light fractions were a homogeneous system with proper caloric value and pH values near neutrality. The species information was relatively simple and these compounds mainly include methyl esters, ketones, phenols, and aethers. The total calorific value of all light fractions was little less than the value of the depolymerization initial sample, so the light fractions could be used as fuel while the remaining liquid could not suitable for fuel. The stability experiment revealed that the species information of the fractions increased gradually as time.The distillation residue was sequentially extracted with n-hexane, carbon tetrachloride, benzene, methanol and acetone in a Soxhlet extractor. Lots of light low-polar esters, heterocyclic compounds, aromatics and alkanes were identified in the fractions of n-hexane, carbon tetrachloride and benzene,respectively, while none were detected in the extracts of methanol and acetone by the GC/MS.The extracts were further separated with a high speed countercurrent chromatography (HSCCC) and then analyzed with HPLC and GC/MS. The original solvent systems of HSCCC established by HPLC were chloroform/carbon tetrachloride/methanol/water(1:3:3:2, v/v), n-hexane/ethyl acetate/methanol/water(3:5:3:5, v/v), ethyl acetate/n-butanol/water(4:1:5, v/v)and ethyl acetate/n-butanol/water (4:1:5, v/v) for distillation residual liquid, extractable fractions with n-hexane, carbon tetrachloride and benzene from distillation residue, respectively. A stepwise elution mode was introduced in the separation and purification and 12, 6, 12 and 12 chromatographic peaks were obtained, respectively. The results of analysis by HPLC and GC/MS showed that the components of every fraction were simple significantly and the number of species decreased markedly. Compared with the direct analysis to the four fractions, there are significant increases in the species number of compounds detected by GC/MS, which was 159, 222, 207 and 125. These compounds were mainly esters, ketones, phenols and hydrocarbons, but there was an obvious difference in type. 11 compounds with high purity were separated successfully from the four fractions, and 4 ketones, 4 esters, 2 phenols and 1 acid amide.These abundant compounds messages and high purity compounds was significant valuable for investigating the comprehensive utilization of the depolymerization products and the depolymerization mechanism of biomass. This result displays a possibility of production of fine chemicals from heavy components through separation approach. The study system of separation and analysis of“graded distillation-fractional extraction-separation with HSCCC-GC/MS analysis”was suitable for separation and analysis of the fractions from light to medium heavy components and the fractions from low polar to medium polar components, and also enriched the study methods of separation and analysis of the organic compounds in the biomass depolymerization products.更多还原