木质素的催化加氢转化

木质素是来源于木质纤维素的一种重要的可再生生物质资源,可用于制备化学品和燃料。由于木质素本身结构的复杂性和稳定性使其难以有效利用。目前大量的制浆和造纸工业的木质素没有得到有效利用,大部分用于燃烧供能,并且造成了一定程度的环境污染。为了保护环境、实现可持续发展,催化转化木质素制备高附加值化学品成为了研究的热点。木质素转化的研究众多,但是进展依然相对缓慢。目前主要的转化方法包括碱催化解聚、酸催化解聚、热化学转化、加氢处理解聚、氧化解聚等。由于加氢处理解聚木质素可以获得低聚木质素、酚类等有价值的化学品和制备烃类燃料,是目前研究的热点和最有效的方法之一。但是,催化剂失活和解聚产物产率不高等依然是需要进一步解决的问题。基于此,梳理了近年来木质素加氢处理主要的催化体系和相关结果,提出了尚待解决的问题,以期为今后建立有效的木质素解聚体系并实现其高值化利用的相关研究提供参考。     

木质素制备生物液体燃料进展

木质素中含有丰富的芳环结构,可以作为可持续再生的原料用于生产高值能源及化工品。但由于木质素结构复杂,现阶段用于制备生物液体燃料仍处于探索阶段。本文首先介绍了木质素通过催化热解、催化氢解、催化氧化3种解聚方式制备生物液体燃料的进展,分析了当前解聚产物存在低碳原子数、高氧含量的不足而导致其难以投入生产使用的现状,指出应通过C—C偶联方法（包括羟醛缩合、烷基化反应、寡聚反应以及Diels-Alder 反应）增加产物碳原子数、使用加氢脱氧（hydrodeoxygenation, HDO）工艺以降低产物氧含量,从而实现由木质素制备高密度生物液体燃料。最后对当前木质素制备高密度燃料所面临的挑战以及未来研究趋势进行了总结与展望,指出构建高效催化体系,耦合解聚、C—C偶联和HDO过程,将是该领域未来研究重点。     

木质素催化解聚的研究进展

木质素是一种芳环结构来源丰富且价格低廉的可再生资源。从木质素出发催化解聚制备单酚类高附加值精细化学品和芳香烃烷烃等高品位生物燃料,可以部分替代以化石燃料为原料的生产过程,是生物质资源全组分高效综合利用的重要组成部分。在木质素催化解聚方法中,催化氢解可以直接将木质素转化为低氧含量的液体燃料,在生物燃料利用方面展现出巨大的潜力。本文详细总结了木质素的催化解聚方法,从催化剂类型、溶剂种类、反应机理及催化剂循环使用性等方面介绍了国内外的主要研究进展,着重阐述了木质素催化氢解方法。最后总结了当前木质素催化解聚过程中存在的难题,并对未来的技术发展提出了建议和展望。     

木质素氧化解聚制备芳香醛研究进展

木质素作为自然界最丰富的芳香族化合物资源，通过可控的氧化解聚方式得到小分子芳香醛类化合物是实现木质素高附加值利用的重要途径。芳香醛作为重要的食用及日化香料、医药中间体、大宗化学品，目前主要通过石油化工产业链生产，以木质素生产芳香醛是具有重要研究意义和应用潜力的可再生资源利用途径。本文综述了国内外有关木质素制备芳香醛的最新研究进展，包括化学氧化解聚、电化学解聚、光催化解聚和生物催化解聚；对不同方法制备芳香醛的转化率和产率进行了对比，基于不同的解聚工艺与催化体系的特点进行评述与分析，展望未来木质素生产芳香醛的研究方向，以实现木质素的高值化利用。得出多方法耦合催化是可能进一步提高木质素生产芳香醛转化率与选择性的有效策略。     

木质素催化解聚的研究进展

木质素是一种芳环结构来源丰富且价格低廉的可再生资源。从木质素出发催化解聚制备单酚类高附加值精细化学品和芳香烃烷烃等高品位生物燃料,可以部分替代以化石燃料为原料的生产过程,是生物质资源全组分高效综合利用的重要组成部分。在木质素催化解聚方法中,催化氢解可以直接将木质素转化为低氧含量的液体燃料,在生物燃料利用方面展现出巨大的潜力。本文详细总结了木质素的催化解聚方法,从催化剂类型、溶剂种类、反应机理及催化剂循环使用性等方面介绍了国内外的主要研究进展,着重阐述了木质素催化氢解方法。最后总结了当前木质素催化解聚过程中存在的难题,并对未来的技术发展提出了建议和展望。     

木质素解聚和液相催化降解研究进展

木质纤维生物质作为地球上最丰富的可再生资源, 不仅储量巨大而且在利用过程中具有碳平衡的显著优势, 已逐渐成为最具发展前景的可再生能源之一。木质纤维中的木质素是自然界最大且唯一的可再生芳香族化合物原料, 在生物质燃料转化, 尤其是解聚生产苯系化工产品等领域具有极为重要的作用和意义。本文在简述木质素化学结构的基础上, 综述了近年来木质素高温热解聚, 生物酶解聚, 催化热解聚, 光催化解聚和溶剂热解聚等解聚方法, 深入分析了液相催化过程中酸、碱催化体系, 加氢和氧化催化体系的机理及优缺点, 总结了现阶段木质素解聚方法中存在的问题, 并对未来的发展方向进行了展望。     

木质素类生物质催化热解制备精细化学品研究进展

能源和环境是当今世界的两大挑战,将生物质转化为燃料和化学品是应对该挑战的低碳方案。其中,催化热解木质素获得燃料和化学品是低碳方案的重要部分。本文以能源和环境问题为出发点,阐述了木质素催化热解制备燃料和化学品的可行性和必要性,并对催化裂解行为、催化裂解过程和催化产物等方面的国内外研究现状进行了系统介绍。文章首先对木质素的结构和转化过程进行了概述;然后从催化热解行为、催化热解产物以及催化剂的研究现状等方面进行了系统阐述,并对现有的催化木质素热解过程的机理研究进行了讨论。通过对木质素催化热解制备燃料和化学品的发展前景、技术瓶颈以及逻辑方面进行评估表明,木质素转化为燃料和化学品过程中提高产品的产率和能量效率是今后的总体目标,而原料供给和生产、催化剂开发、产品分离纯化、反应机理和动力学以及计算模拟等方面将是深入研究木质素高效利用的重要研究内容。     

木质素结构及其催化转化方法的研究进展

木质素是自然界目前唯一由芳香结构组成的最丰富的可再生能源,其化学结构使得木质素非常适合生产芳香类化合物。目前,对木质素的研究主要集中于利用催化转化方法生产高附加值的化学品和生物油方面。本文介绍了木质素的基本结构及其催化转化制备化学品的方法及研究现状。最后,指出目前催化转化过程中存在的一些问题,并对未来发展进行了展望。     

合肥研究院在生物质催化转化方面取得进展

正近期,中国科学院合肥物质科学研究院固体物理研究所环境与能源纳米材料中心在生物质催化转化方面取得新进展。随着化石能源危机日益严峻,开发绿色可再生能源已经刻不容缓,生物质作为一种储量丰富的可再生资源,已成为代替化石能源的"宠儿",但是由于其含氧量较高,不能直接代替化石燃料。在化学工业上,加氢脱氧被公认为是提高生物质燃料品质及获取高附加值化学品最有效的方法。香兰素作为木质素中一种重要的芳香单体,将其转化为含氧量更低的高附加值化学品     

木质素水热解聚研究进展

木质素是由苯丙烷单元通过C-C键和醚键连接而成的天然高分子材料,结构中含有大量的芳香基以及甲氧基、酚羟基、醇羟基、羰基、醛基等基团,是自然界唯一能提供可再生芳香化合物的非石油资源,其如何被有效利用一直受到人们的关注,尤其是通过化学解聚的方法将木质素转化为化工单体:以代替石油基产品是近年来木质素开发利用的研究热点。基于木质素的结构,从木质素的水热解聚出发,综述了木质素在酸催化水热解聚、碱催化水热解聚及其它介质中水热解聚的研究进展,对其存在问题和解决方法进行了合理分析,并对未来木质素水热解聚的发展方向进行了展望。     

High-Value Chemicals from Electrocatalytic Depolymerization of Lignin: Challenges and Opportunities

Lignocellulosic biomass is renewable and one of the most abundant sources for the production of high-value chemicals, materials, and fuels. It is of immense importance to develop new efficient technologies for the industrial production of chemicals by utilizing renewable resources. Lignocellulosic biomass can potentially replace fossil-based chemistries. The production of fuel and chemicals from lignin powered by renewable electricity under ambient temperatures and pressures enables a more sustainable way to obtain high-value chemicals. More specifically, in a sustainable biorefinery, it is essential to valorize lignin to enhance biomass transformation technology and increase the overall economy of the process. Strategies regarding electrocatalytic approaches as a way to valorize or depolymerize lignin have attracted significant interest from growing scientific communities over the recent decades. This review presents a comprehensive overview of the electrocatalytic methods for depolymerization of lignocellulosic biomass with an emphasis on untargeted depolymerization as well as the selective and targeted mild synthesis of high-value chemicals. Electrocatalytic cleavage of model compounds and further electrochemical upgrading of bio-oils are discussed. Finally, some insights into current challenges and limitations associated with this approach are also summarized.     

Chemical modification of lignins: Towards biobased polymers

Lignins are now considered as the main aromatic renewable resource. They represent an excellent alternative feedstock for the elaboration of chemicals and polymers. Lignin is a highly abundant biopolymeric material that constitutes with cellulose one of the major components in structural cell walls of higher vascular plants. Large quantities of lignin are yearly available from numerous pulping processes such as paper and biorefinery industries. Lignin extraction from lignocellulosic biomass (wood, annual plant) represents the key point to its large use for industrial applications. One of the major problems still remains is its unclearly defined structure and its versatility according to the origin, separation and fragmentation processes, which mainly limits its utilization. While currently often used as a filler or additive, lignin is rarely exploited as a raw material for chemical production. However, it may be an excellent candidate for chemical modifications and reactions due to its highly functional character (i.e., rich in phenolic and aliphatic hydroxyl groups) for the development of new biobased materials. Chemical modification of lignin has driven numerous efforts and researches with significant studies during the last decades.     

Role of lignin in a biorefinery: separation characterization and valorization

Lignin, a major component of the cell wall of vascular plants, has long been recognized for its negative impact and treated as a by‐product in a biorefinery. This highly abundant by‐product of the biorefinery is undervalued and underdeveloped due to its complex nature. The development of value‐added products from lignin would greatly improve the economics of the biorefinery. The inherent properties of lignin significantly affect the productivity of the biorefinery processes and its potential applications. Although the structure and biosynthetic pathway of lignin have been studied for more than a century, they have not yet been completely elucidated. In this mini‐review, the primary obstacles to elucidating the structure of native lignin, including separation and characterization, are highlighted. Several classical methods for separation and various NMR techniques, especially 2D HSQC NMR, for characterization of lignin are reviewed. Some potential applications of lignin are introduced. It is believed that a knowledge of the method to separate lignin from the cell wall and structural features of the lignin polymer from lignocellulosic materials will help to maximize the exploitation of lignocelluloses for the biorefinery as well as the utilization of lignin for novel materials and chemicals. © 2012 Society of Chemical Industry     

A review on lignin-based polymeric,micro- and nano-structured materials

Next to cellulose, lignin is the second most abundant biopolymer, and the main source of aromatic structures on earth. It is a phenolic macromolecule, with a complex structure which considerably varies depending on the plant species and the isolation process. Lignin has long been obtained as a by-product of cellulose in the paper pulp production, but had rather low added-value applications. Changes in the paper market have however stimulated the need to focus on other applications for lignins. In addition, the emergence of biorefinery projects to develop biofuels, bio-based materials and chemicals from carbohydrate polymers should also generate large amounts of lignin with the potential for value addition.These developments have brought about renewed interest in the last decade for lignin and its potential use in polymer materials. This review covers both the topics of the direct use of lignin in polymer applications, and of the chemical modifications of lignin, in a polymer chemistry perspective. The future trend toward micro- and nanostructured lignin-based materials is then addressed.     

木质素基功能材料的制备与应用研究进展

木质素是植物中含量第二大的天然有机高分子聚合物,以来源于制浆造纸和生物质炼制中的工业木质素为原料,制备具有特殊功能的高附加值材料,对木质素进行资源化高效利用、解决化石资源日趋紧缺及环境污染等问题具有重要意义。近年来,研究人员利用各种技术制备了许多种类的木质素基功能材料,如载药微胶囊、防紫外剂、抗老化剂、光催化剂载体、炭电极材料等。本文介绍了木质素基功能材料的国内外最新研究进展,总结了木质素基功能材料的不同制备工艺和应用领域,评述了木质素微观结构及制备工艺对材料结构特性和应用性能的影响。指出木质素基功能材料的研究是涉及多个学科交叉的前沿课题,但如何高效制备结构规整可控且性能优异的木质素基功能材料仍然是一个具有挑战性的课题。今后的研究应加强对木质素微观结构及其调控机理的研究,以便可以更好地利用其自身的三维网状结构和大量芳香结构等特性制备基于木质素特性的功能材料。     

木质素氢解反应溶剂与催化剂研究进展

木质素是由三种苯丙烷单元随机键合形成的复杂大分子物质,是自然界中唯一可直接提供芳环的可再生能源。以木质素为原料制取高品位液体燃料和高附加值化学品,特别是木质素氢解是国内外关注的热门研究领域之一。梳理了近年木质素催化氢解研究进展,针对木质素氢解过程中溶剂体系（水溶剂以及醇类溶剂）和催化剂体系（均相催化剂以及非均相金属催化剂）对木质素氢解效率、产物分布的影响机理,做了较全面的概述和分析。最后,针对木质素催化氢解领域目前尚存在的问题提出建议,期望为木质素高值化利用相关研究提供参考。     

Customized Utilization Strategies of Industrial Lignin to Produce Adsorbents and Flocculants Based on Fractionation and Adequate Structural Interpretation

Lignin, a by-product of pulping and biorefinery, has great potential to replace petrochemical resources for wastewater purification. However, the defects of lignin, such as severe heterogeneity, inferior reactivity and poor solubility, characterize the production process of lignin-based products by high energy consumption and serious pollution. In this study, several lignin fractions with relatively homogeneous structure were first obtained by organic solvent fractionation, and their structures were fully deciphered by various characterization techniques. Subsequently, each lignin component was custom-valued for wastewater purification based on their structural characteristics. Benefiting from the high reactivity and reaction accessibility, the lignin fraction (lignin-1) refined by dissolving in ethanol and n-butanol could been used as a raw material to produce cationic lignin-based flocculant (LBF) in a copolymerization system using green, cheap and recyclable ethanol as solvent. The lignin fraction (lignin-2) extracted by methanol and dioxane showed low reactivity and high carbon content, which was used to produce lignin-based activated carbon (LAC) with phosphoric acid as activator. Moreover, the influences of synthetic factors on the purification capacity were discussed, and the LBF and LAC produced under the optimal conditions showed distinguished purification effect on kaolin suspension and heavy metal wastewater, respectively. Furthermore, the corresponding purification mechanism and external factors were also elaborated. It is believed that this cleaner production strategy is helpful for the valorization of lignin in wastewater resources.     

Organosolv lignin depolymerization with different base catalysts

BACKGROUND: Revalorization of lignin is one of the key economical requirements for the development of cost‐effective biorefinery processes. The lignin polyphenolic structure is ideally suited to transformation catalytically into lower molecular weight compounds such as phenols, aromatic acids, esters, ethers, etc., replacing those obtained from petroleum. RESULTS: Lignin was subjected to base catalyzed depolymerization paying attention to the base effect on the oil yield and composition. The oil yields and compositions varied (5–20%) strongly depending on the base used, suggesting that the reactions took place via different mechanisms. As a result, the monomeric compounds obtained were different (catechol, cresols, syringol, guaiacol). Residual lignin contents were high for most of the experiments (up to 45%), and repolymerization reactions were proved to be one of the main reasons for this behavior. CONCLUSION: The results showed that lignin depolymerization produced phenolic compounds that can be introduced into existing petrochemical industries. The base selection will govern the nature of the products obtained. Repolymerization was proved to take place and to be the reason for the limitation on oil production. Copyright © 2012 Society of Chemical Industry     

Applications of process synthesis: Moving from conventional chemical processes towards biorefinery processes

Concerns about diminishing petroleum reserves, enhanced worldwide demand for fuels and fluctuations in the global oil market, together with climate change and national security have promoted many initiatives for exploring alternative, non-petroleum based processes. Among these initiatives, biorefinery processes for converting biomass derived carbohydrates into transportation fuels and chemicals are now gaining more and more attention from both academia and industry. Process synthesis, which has played a vital role for the development, design and operation of (petro) chemical processes, can be predicted to play a significant role in the design and commercialization of sustainable and cost-effective biorefinery processes. The main objective of this perspective paper is to elucidate the potential opportunities that biorenewables processing offers to optimal synthesis; challenges and future directions in this field are also concisely discussed. An attempt is made with this perspective to stimulate more and more efforts to optimally synthesize and design biorenewable conversion process to accelerate the commercialization of the biorefinery technology and further reduce the heavily reliance on petroleum-derive fuels.