Recent progress in the development of solid catalysts for biomass conversion into high value-added chemicals

Abstract

In recent decades, the substitution of non-renewable fossil resources by renewable biomass as a sustainable feedstock has been extensively investigated for the manufacture of high value-added products such as biofuels, commodity chemicals, and new bio-based materials such as bioplastics. Numerous solid catalyst systems for the effective conversion of biomass feedstocks into value-added chemicals and fuels have been developed. Solid catalysts are classified into four main groups with respect to their structures and substrate activation properties: (a) micro- and mesoporous materials, (b) metal oxides, (c) supported metal catalysts, and (d) sulfonated polymers. This review article focuses on the activation of substrates and/or reagents on the basis of groups (a)–(d), and the corresponding reaction mechanisms. In addition, recent progress in chemocatalytic processes for the production of five industrially important products (5-hydroxymethylfurfural, lactic acid, glyceraldehyde, 1,3-dihydroxyacetone, and furan-2,5-dicarboxylic acid) as bio-based plastic monomers and their intermediates is comprehensively summarized.     

木质纤维素类生物基材料研究进展

木质纤维素类生物质作为重要的可再生资源,不仅可以转化为能源及化工品,还可以合成相关的生物基材料。本文综述了以木质纤维素类生物质各组分为原料合成的生物基材料的种类、方法和应用,发现生物质是很好的化石材料替代品。直接将生物质各组分进行生物基材料合成会缩小其应用范围,运用化学改性方法对生物质各组分进行化学改性后再合成生物基材料,可以优化材料的一些性能,其中,基于生物质绿色、可降解和无污染的天然特性,在污水处理和替代相关石油基材料的原料方面其将发挥更重要的作用。     

炭材料负载金属催化剂在活化过硫酸盐中的应用进展

近年来,基于硫酸根自由基的高级氧化技术在环境污染治理中的应用受到越来越广泛的关注,而炭材料负载金属催化剂在活化过硫酸盐去除环境污染物方面展示出巨大的优势。全面总结了炭材料负载金属离子、金属单质、金属氧化物等而制备的不同催化剂在活化过硫酸盐中的作用机制以及对污染物的降解效果等方面的研究进展,并指出了该类催化剂在活化过硫酸盐氧化中的应用前景与未来的研究方向。     

Sustainable Carbonaceous Materials Derived from Biomass as Metal‐Free Electrocatalysts

Although carbon is the second most abundant element in the biosphere, a large proportion of the available carbon resources in biomass from agriculture, stock farming, ocean fisheries, and other human activities is currently wasted. The use of sustainable carbonaceous materials as an alternative to precious metals in electrocatalysis is a promising pathway for transforming sustainable biomass resources into sustainable energy‐conversion systems. The development of rational syntheses of metal‐free carbonaceous catalysts derived from sustainable biomass has therefore become a topic of significant interest in materials chemistry. However, great efforts are still required to develop methods that are low cost, scalable, and environmentally friendly and which afford carbonaceous materials having an electrocatalytic performance comparable to, or even better than, existing precious metal catalysts. Herein, recent achievements in developing metal‐free carbonaceous catalysts based on biomass are reviewed and discussed and the critical issues which still need to be addressed are highlighted. The focus is on representative synthesis and optimization strategies applicable to different kinds of biomass, as well as studies of the physicochemical structure and electrochemical performance of the resulting metal‐free carbonaceous catalysts. Finally, some guidelines for the future development of this important area are provided.     

非贵金属/碳氮复合材料电催化析氧反应的研究进展

析氧反应(OER)是一种复杂的四电子转移反应,其动力学缓慢、所需能量高,制约了电解水制氢等新型能源技术的发展.近年来,非贵金属复合材料因其优异的催化活性以及相比于贵金属基催化剂的成本优势而受到广泛关注.本文概述了这一研究领域的最新进展,首先简要介绍析氧反应的机理以及材料催化性能的评价方法,重点关注非贵金属/碳氮复合材料...     

New Strategies for the Preparation of Sinter‐Resistant Metal‐Nanoparticle‐Based Catalysts

Supported metal nanoparticles are widely used as catalysts in the industrial production of chemicals, but still suffer from deactivation because of metal leaching and sintering at high temperature. In recent years, serious efforts have been devoted to developing new strategies for stabilizing metal nanoparticles. Recent developments for preparing sinter‐resistant metal‐nanoparticle catalysts via strong metal–support interactions, encapsulation with oxide or carbon layers and within mesoporous materials, and fixation in zeolite crystals, are briefly summarized. Furthermore, the current challenges and future perspectives for the preparation of highly efficient and extraordinarily stable metal‐nanoparticle‐based catalysts, and suggestions regarding the mechanisms involved in sinter resistance, are proposed.     

Metal‐Organic Frameworks for CO2 Chemical Transformations

Carbon dioxide (CO₂), as the primary greenhouse gas in the atmosphere, triggers a series of environmental and energy related problems in the world. Therefore, there is an urgent need to develop multiple methods to capture and convert CO₂ into useful chemical products, which can significantly improve the environment and promote sustainable development. Over the past several decades, metal‐organic frameworks (MOFs) have shown outstanding heterogeneous catalytic activity due in part to their high internal surface area and chemical functionalities. These properties and the ability to synthesize MOF platforms allow experiments to test structure‐function relationships for transforming CO₂ into useful chemicals. Herein, recent developments are highlighted for MOFs participating as catalysts for the chemical fixation and photochemical reduction of CO₂. Finally, opportunities and challenges facing MOF catalysts are discussed in this ongoing research area.     

An overview of biorefinery-derived platform chemicals from a cellulose and hemicellulose biorefinery

Until recently, most of energy and industrially produced chemicals were derived from fossil fuel-based resources. This along with the continued depletion of finite fossil resources and their attributed adverse environmental impacts, alternatively sourced and more sustainable resources are being pursued as feedstock replacements. Thus, biomass has been identified as an alternate renewable and more sustainable resource as a means to reduce this sector’s dependence on fossil fuel-based resources and to alleviate their environmental impacts. As such, lignocellulosic biomass has been further identified and demonstrated as an abundant renewable resource for the production of biofuels, platform chemicals, and their respective value-added products. This review article provides an overview of the techniques developed for the valorization of biomass in the production of platform chemicals within a biorefinery and the status for commercialization.     

硅胶固载酸功能化离子液体催化剂的制备和应用

将带有酸官能团的离子液体固载到具有高表面积的硅胶上,制备的硅胶固载酸功能化离子液体可作为催化剂用于多种有机反应。该新型催化剂具有高效、高选择性、离子液体用量少、产品易分离和催化剂易回收等优点,因有望用于化工过程的固定床反应器而受到关注。     

Robust Catalysis on 2D Materials Encapsulating Metals: Concept,Application, and Perspective

Great endeavors are undertaken to search for low‐cost, rich‐reserve, and highly efficient alternatives to replace precious‐metal catalysts, in order to cut costs and improve the efficiency of catalysts in industry. However, one major problem in metal catalysts, especially nonprecious‐metal catalysts, is their poor stability in real catalytic processes. Recently, a novel and promising strategy to construct 2D materials encapsulating nonprecious‐metal catalysts has exhibited inimitable advantages toward catalysis, especially under harsh conditions (e.g., strong acidity or alkalinity, high temperature, and high overpotential). The concept, which originates from unique electron penetration through the 2D crystal layer from the encapsulated metals to promote a catalytic reaction on the outermost surface of the 2D crystal, has been widely applied in a variety of reactions under harsh conditions. It has been vividly described as “chainmail for catalyst.” Herein, recent progress concerning this chainmail catalyst is reviewed, particularly focusing on the structural design and control with the associated electronic properties of such heterostructure catalysts, and also on their extensive applications in fuel cells, water splitting, CO₂ conversion, solar cells, metal–air batteries, and heterogeneous catalysis. In addition, the current challenges that are faced in fundamental research and industrial application, and future opportunities for these fantastic catalytic materials are discussed.     

Current advances in precious metal core–shell catalyst design

Precious metal nanoparticles are commonly used as the main active components of various catalysts. Given their high cost, limited quantity, and easy loss of catalytic activity under severe conditions, precious metals should be used in catalysts at low volumes and be protected from damaging environments. Accordingly, reducing the amount of precious metals without compromising their catalytic performance is difficult, particularly under challenging conditions. As multifunctional materials, core–shell nanoparticles are highly important owing to their wide range of applications in chemistry, physics, biology, and environmental areas. Compared with their single-component counterparts and other composites, core–shell nanoparticles offer a new active interface and a potential synergistic effect between the core and shell, making these materials highly attractive in catalytic application. On one hand, when a precious metal is used as the shell material, the catalytic activity can be greatly improved because of the increased surface area and the closed interfacial interaction between the core and the shell. On the other hand, when a precious metal is applied as the core material, the catalytic stability can be remarkably improved because of the protection conferred by the shell material. Therefore, a reasonable design of the core–shell catalyst for target applications must be developed. We summarize the latest advances in the fabrications, properties, and applications of core–shell nanoparticles in this paper. The current research trends of these core–shell catalysts are also highlighted.     

Metal Organic Framework Derived Materials: Progress and Prospects for the Energy Conversion and Storage

Exploring new materials with high efficiency and durability is the major requirement in the field of sustainable energy conversion and storage systems. Numerous techniques have been developed in last three decades to enhance the efficiency of the catalyst systems, control over the composition, structure, surface area, pore size, and moreover morphology of the particles. In this respect, metal organic framework (MOF) derived catalysts are emerged as the finest materials with tunable properties and activities for the energy conversion and storage. Recently, several nano‐ or microstructures of metal oxides, chalcogenides, phosphides, nitrides, carbides, alloys, carbon materials, or their hybrids are explored for the electrochemical energy conversion like oxygen evolution, hydrogen evolution, oxygen reduction, or battery materials. Interest on the efficient energy storage system is also growing looking at the practical applications. Though, several reviews are available on the synthesis and application of MOF and MOF derived materials, their applications for the electrochemical energy conversion and storage is totally a new field of research and developed recently. This review focuses on the systematic design of the materials from MOF and control over their inherent properties to enhance the electrochemical performances.     

甲烷干气重整镍基复合结构催化剂的研究进展

甲烷干气重整反应能够实现温室气体CO₂和CH₄的转化利用, 其反应产物合成气可以通过费托反应进一步生产液态燃料, 该反应在能源与环境领域具有重要意义。寻找合适的催化剂是推动甲烷干气重整工业化的关键。镍基复合结构催化剂因其与贵金属催化剂相媲美的催化活性和低廉的工业成本而受到广泛关注, 但镍基催化剂存在高温下长时间反应后碳沉积和金属组分烧结所导致的失活问题, 严重影响了其工业应用和干气重整化工的发展。本文从镍基复合结构催化剂的成分、结构、制备方法及模拟计算设计等方面出发, 介绍了改进镍基催化剂活性、抗积碳和抗烧结性能的研究进展, 并结合最新的原子催化以及原位表征等研究进展对干气重整研究的发展趋势进行 展望。     

Ultrasmall Metal Nanoparticles Confined within Crystalline Nanoporous Materials: A Fascinating Class of Nanocatalysts

Crystalline nanoporous materials with uniform porous structures, such as zeolites and metal–organic frameworks (MOFs), have proven to be ideal supports to encapsulate ultrasmall metal nanoparticles (MNPs) inside their void nanospaces to generate high‐efficiency nanocatalysts. The nanopore‐encaged metal catalysts exhibit superior catalytic performance as well as high stability and catalytic shape selectivity endowed by the nanoporous matrix. In addition, the synergistic effect of confined MNPs and nanoporous frameworks with active sites can further promote the catalytic activities of the composite catalysts. Herein, recent progress in nanopore‐encaged metal nanocatalysts is reviewed, with a special focus on advances in synthetic strategies for ultrasmall MNPs (<5 nm), clusters, and even single atoms confined within zeolites and MOFs for various heterogeneous catalytic reactions. In addition, some advanced characterization methods to elucidate the atomic‐scale structures of the nanocatalysts are presented, and the current limitations of and future opportunities for these fantastic nanocatalysts are also highlighted and discussed. The aim is to provide some guidance for the rational synthesis of nanopore‐encaged metal catalysts and to inspire their further applications to meet the emerging demands in catalytic fields.     

Research Advances of Amorphous Metal Oxides in Electrochemical Energy Storage and Conversion

Amorphous metal oxides (AMOs) have aroused great enthusiasm across multiple energy areas over recent years due to their unique properties, such as the intrinsic isotropy, versatility in compositions, absence of grain boundaries, defect distribution, flexible nature, etc. Here, the materials engineering of AMOs is systematically reviewed in different electrochemical applications and recent advances in understanding and developing AMO‐based high‐performance electrodes are highlighted. Attention is focused on the important roles that AMOs play in various energy storage and conversion technologies, such as active materials in metal‐ion batteries and supercapacitors as well as active catalysts in water splitting, metal–air batteries, and fuel cells. The improvements of electrochemical performance in metal‐ion batteries and supercapacitors are reviewed regarding the enhancement in active sites, mechanical strength, and defect distribution of amorphous structures. Furthermore, the high electrochemical activities boosted by AMOs in various fundamental reactions are elaborated on and they are related to the electrocatalytic behaviors in water splitting, metal–air batteries, and fuel cells. The applications in electrochromism and high‐conducting sensors are also briefly discussed. Finally, perspectives on the existing challenges of AMOs for electrochemical applications are proposed, together with several promising future research directions.     

Cork–polymer biocomposites: Mechanical,structural and thermal properties

This work addresses to the preparation of biocomposites resulting from the combination of different biodegradable aliphatic polyesters with cork (30 wt.%). The lignocellulosic biomass with closed cellular structure was compounded with poly(L-lactic acid) (PLLA), polyhydroxybutyrate-co-hydroxyvalerate (PHBV), poly-ε-caprolactone (PCL) and starch-poly-ε-caprolactone (SPCL) blend using a twin-screw extruder prior to injection moulding into tensile samples. The physico-mechanical and thermal properties of the matrices and the bio-based cork composites were investigated. This study shows that the addition of cork contributes to produce lightweight materials using PLLA and PHBV matrices and promotes an increase on the stiffness of PCL. The fracture morphology observations showed good physical cork–matrix bonding with absence of voids or cavities between cork and the bio-based polyesters. Cork increases the crystallinity degree of the biocomposites. These findings suggest that the cork–polymer biocomposites are a viable alternative to develop more sustainable composite materials, such as automotive interior parts and bio-based caps for wine bottles as it has been shown as proof-of-concept.     

催化剂在木质纤维素液化中应用的研究进展

木质纤维素是最丰富的可再生资源之一,具有低污染,广泛分布等优点,在化石资源日益枯竭的背景下,将其转化为高附加值化学品,为工业原料和能源油料提供可替代的资源是当前研究的一个热点,具有广阔的发展前景。文中详细综述了近年来国内外在木质纤维素液化中使用的催化剂类型、作用和研究进展,主要介绍了以浓硫酸为代表的液体无机酸,以NaOH为代表的固体无机碱,以草酸为代表的有机酸,以AlCl_3为代表的盐类和以Cl-/Fe_2O_3为代表的固体杂多酸;同时,分析、对比了不同类型催化剂的优点和缺点,预测了未来木质纤维素液化催化剂的发展趋势和前景。     

金属掺杂聚吡咯碳化物PPY-M的制备及其氧还原反应电催化活性

在Fe³⁺或Co²⁺存在下进行吡咯的聚合反应, 得到金属离子掺杂的聚吡咯, 并在N₂气氛下700℃碳化, 再将该碳化产物在900℃焙烧得到含有不同金属的复合催化剂PPY-M(M为不同的金属)。采用SEM、XRD等对催化剂的结构进行了表征。通过循环伏安和线性电位扫描等电化学手段, 研究了催化剂对氧还原(ORR)的电催化活性及其稳定性。结果表明, 掺杂金属钴的催化剂的活性最好, 在酸性溶液中ORR的起始电位达到0.54 V(vs SCE),电流密度为7.5 mA/mg@-0.3 V(vs SCE); 在碱性溶液中ORR的起始电位为-0.11 V(vs SCE),电流密度为5.7 mA/mg@-0.8 V。Fe或Co掺杂的聚吡咯碳化物对ORR具有较强的电催化活性, 而且制备过程简单、成本低, 有较重要的研究意义。     

镁基储氢材料催化的研究进展

过去十几年国内外对镁基储氢材料的催化剂研究表明,使用催化剂能够有效改善材料的表面特性,提高材料的吸放氢动力学性能。目前常用的催化剂体系有过渡族金属、金属氧化物、金属卤化物、金属间化合物以及碳素非金属。通过比较发现,不同种类的催化剂催化效果不同,相应的催化机理也有所差异。目前,国外研究者已发现几种催化剂共同催化的效果显著,国内应加强金属间化合物和碳素材料催化剂以及不同催化剂共同作用方面的研究。