【作者】 李江；

【导师】 傅尧；

【作者基本信息】 中国科学技术大学 ， 可再生洁净能源， 2014， 博士

【摘要】 化石燃料的使用带来的环境危机和能源危机亟需研究人员开发替代化石能源的新能源。生物质是目前新能源领域中唯一能替代化石能源中碳来源的可再生资源。将其转化为液体燃料和化学品是目前国内外研究的热点。本论文着眼于研究利用生物质尤其是自然界中存在的木质纤维生物质制备一些燃料平台分子和化学品。论文的第一章首先对生物质的概念进行了简介,引出了生物质平台分子的概念并强调了羧酸类化合物是生物质平台分子中的主要成员。随后对所研究的三个羧酸分子：乙酰丙酸,甲酸和乙酸进行了简介。乙酰丙酸是生物质平台分子中重要的一员,本文主要对其工业生产工艺和进一步转化为先进液体燃料和燃料添加剂的研究进行了简介。其次,本文简要介绍了甲酸作为工业大宗化学品的用途,并对近期甲酸与二氧化碳,氢气间的可逆转化进行了简介,并预期以甲酸为中间体的生物质产氢过程可能是未来生物质转化的重要研究之一。最后,本文简要介绍了乙酸这种工业大宗化学品的用途,工业生产工艺以及其中存在的问题,为发展从生物质制备乙酸的工业生产工艺提供了指导意义。针对目前生物质制备甲酸过程存在的反应条件苛刻,需要额外碱的加入等问题,在第二章中,我们使用钒掺杂的杂多酸,首次实现了温和条件下生物质基碳水化合物氧化制备甲酸的过程。该过程具有以下的优点：(1)在373K的反应温度下,以葡萄糖作为反应原料,使用空气或氧气,即可实现52%的甲酸最高产率；(2)H5PV2Mo10040型杂多酸可以作为双功能催化剂催化纤维素降解为甲酸,在443K的反应温度下,空气作为氧化剂时,甲酸的产率最高可达35%。反应中间体的筛选过程证明了醛基是产生甲酸过程不可或缺的官能团,而所用杂多酸催化剂的活性中心为钒原子。随后,针对目前由生物质生产乙酰丙酸的路线中乙酰丙酸质量产率较低的问题,我们首次提出了在四氢呋喃和盐水的双相体系中,全转化木质纤维生物质中的碳水化合物生产乙酰丙酸的路线。本工作不仅通过模型反应证明了反应体系的可行性,还对真实生物质原料的转化进行了研究。THF和水的双相体系首先成功实现了生物质原料中六碳糖和五碳糖成分的一步水解,水解产率与前人报道结果相当。随后,一步减压蒸馏过程不仅可以有效地将由木质素和胡敏素组成的固体残余物与水解产物分离,还成功将水解产物中糠醛,甲酸与乙酰丙酸分离,从而便于进一步考察利用水解副产物甲酸还原糠醛的过程。使用Ru基催化剂不仅实现了甲酸还原糠醛的模型反应,反应体系还可以用于生物质水解液中副产物甲酸还原糠醛的过程。最终,所提出的集成策略获得了目前报道最高的由生物质原料生产乙酰丙酸的质量产量,与单水解六碳糖相比,乙酰丙酸的产率最多提高了68.9%,证明了本工作所提出的由生物质原料生产乙酰丙酸的集成策略具有很高的应用前景。最后,我们发展了一种生物质高选择性高产率制备乙酸的方法。反应过程只需要使用硫酸作为酸催化剂,氧气作为氧化剂,多种生物质原料可以被转化到乙酸,乙酸的最高质量收率为21.3%,且液体产物中乙酸的选择性高达90%。随后,关于生物质原料各组分转化到乙酸过程的研究证明了碳水化合物尤其是六碳糖,是乙酸的主要来源,乙酰丙酸是反应的重要中间体。最终,我们着重研究了反应工艺中催化剂回收使用,乙酸的纯化过程,从而对乙酸工业生产过程进行了初步探索。更多还原

【Abstract】 Economic and geopolitical factors (high oil prices, environmental concerns, and supply instability) have certainly played a role in reviving interest in renewable resources. Biomass is currently the only renewable carbon source in the field of new energy. Therefore, the generation of liquid fuels and chemicals from it is currently a hot research topic. This paper focuses on the study of the utilization of biomass, especially lignocellulosic biomass to generate a number of commodity chemicals and biofuel platform molecules. In the first chapter, we first introduce the concept of biomass and biomass platform molecules, and we emphasize carboxylic acids is a key member of biomass platform molecules. Then we briefly introduce three carboxylic acids, levulinic acid, formic acid and acetic acid. Levulinic acid maybe is the most important biomass platform molecules. We primarily state the industrial technology for its generation, and then its conversion into liquid fuels and advanced fuel additives. Secondly, we briefly describe the industrial commodity chemical, formic acid. The reversible transformation of formic acid and carbon dioxide, hydrogen has emerged a hot area for fuel cell, and we propose that the production hydrogen from biomass with formic acid as intermediate is an important process in the future. Finally, we describe the industrial bulk chemical, acetic acid. Introduce the problems existing in the industrial generation of acetic acid will assist us developing industrial production of acetic acid from biomass.Currently, generation of formic acid from biomass needs harsh reaction conditions and/or the additional use of base. In the second chapter, for the first time, we achieve the generation of formic acid from biomass-derived carbohydrates under mild reaction conditions by the use of H5PV2Mo10O40. The highest yield of formic acid for glucose oxidation was55%when oxidized by oxygen and52%when oxidized by air. The X-ray photoelectron spectra and reactions of possible intermediates indirectly revealed the reaction mechanism to be electron and oxygen transfer processes. H5PV2Mo10O40can also be used as a bifunctional catalyst for the conversion of cellulose into FA at443K in9h with35%yield when using air as the oxidant.Then we reported the integrated conversion of lignocellulosic biomass to levulinic acid in a biphasic system consisting of THF and NaCl aqueous solution. The one-step hydrolysis of C6and C5carbohydrates in the lignocellulosic biomass was firstly achieved to give a product solution that contained furfural, formic acid, levulinic acid and lignin, and the hydrolysis process was operated with both model substrates and biomass raw materials. The yields of the hydrolysis products are comparable to values obtained in the literature using a mixed solvent of GVL and water. In contrast to processes using the high boiling point solvent GVL, the utilization of THF allowed a one-step distillation of the product solution into three fractions:furfural and formic acid; levulinic acid; lignin. This separation step not only removed the solid residue from the desired product effectively, but it also let us investigate the hydrogenation of furfural with by-product formic acid without any interference. The hydrogenation process was eventually achieved and the product furfuryl alcohol was finally hydrolyzed to levulinic acid to achieve the integrated conversion of lignocellulosic biomass to levulinic acid. The highest mass yield of levulinic acid was27.7%, which was promoted by68.9%with the additional conversion of the hemicellulose fraction. Thus, the utilization of a lower boiling point solvent, THF, not only achieves the simultaneous hydrolysis of C6and C5carbohydrates in lignocellulosic biomass, but as compared to GVL, it also offers an alternative operation procedure for the integrated conversion of biomass to levulinic acid.Finally, we develop a method for preparing a high yield with high selectivity of acetic acid from lignocellulosic biomass. While using sulfuric acid as the acid catalyst, oxygen as the oxidant, a variety of biomass materials can be converted to acetic acid with a highest mass yield of21.3%and highest liquid product selectivity of90%. The transformation of the components of the biomass feedstock demonstrated that the carbohydrates, especially hexoses are the main source of acetic acid, and levulinic acid is the main intermediate. Ultimately, we focus on the recycle of catalyst and the purification of acetic acid which are important factors in industrial processes for acetic acid production.更多还原