Protection Strategies Enable Selective Conversion of Biomass

Selective and economic conversion of lignocellulosic biomass components to bio‐based fuels and chemicals is the major goal of biorefineries, but low yields and selectivity for fuel precursors such as sugars, furanics, and lignin‐derived monomers pose significant disadvantages in process economics. In this Minireview we summarize the existing protection strategies used in biomass chemocatalytic conversion processes and focus the discussions on the mechanisms, challenges, and opportunities of each strategy. We introduce a concept of using analogous methods to manipulate biomass catalytic conversion pathways during the upgrading of carbohydrates to fuels and chemicals. This Minireview may provide new insights into the development of selective biorefining processes from a different perspective, expanding the options for selective conversion of biomass to fuels and chemicals.     

Molecular‐Level Understanding of the Carbonisation of Polysaccharides

Understanding of both the textural and functionality changes occurring during (mesoporous) polysaccharide carbonisation at the molecular level provides a deeper insight into the whole spectrum of material properties, from chemical activity to pore shape and surface energy, which is crucial for the successful application of carbonaceous materials in adsorption, catalysis and chromatography. Obtained information will help to identify the most appropriate applications of the carbonaceous material generated during torrefaction and different types of pyrolysis processes and therefore will be important for the development of cost‐ and energy‐efficient zero‐waste biorefineries. The presented approach is informative and semi‐quantitative with the potential to be extended to the formation of other biomass‐derived carbonaceous materials.     

Derivative spectrophotometric analysis of benzophenone (as an impurity) in phenytoin

Background

Biomass and municipal solid waste offer sustainable sources of energy; for example to meet heat and electricity demand in the form of combined cooling, heat and power. Combustion of biomass has a lesser impact than solid fossil fuels (e.g. coal) upon gas pollutant emissions, whilst energy recovery from municipal solid waste is a beneficial component of an integrated, sustainable waste management programme. Concurrent combustion of these fuels using a fluidised bed combustor may be a successful method of overcoming some of the disadvantages of biomass (high fuel supply and distribution costs, combustion characteristics) and characteristics of municipal solid waste (heterogeneous content, conflict with materials recycling). It should be considered that combustion of municipal solid waste may be a financially attractive disposal route if a 'gate fee' value exists for accepting waste for combustion, which will reduce the net cost of utilising relatively more expensive biomass fuels.

Results

Emissions of nitrogen monoxide and sulphur dioxide for combustion of biomass are suppressed after substitution of biomass for municipal solid waste materials as the input fuel mixture. Interactions between these and other pollutants such as hydrogen chloride, nitrous oxide and carbon monoxide indicate complex, competing reactions occur between intermediates of these compounds to determine final resultant emissions.

Conclusions

Fluidised bed concurrent combustion is an appropriate technique to exploit biomass and municipal solid waste resources, without the use of fossil fuels. The addition of municipal solid waste to biomass combustion has the effect of reducing emissions of some gaseous pollutants.     

Nanostructured Metal Catalysts for Selective Hydrogenation and Oxidation of Cellulosic Biomass to Chemicals

Conversion of biomass to chemicals provides essential products to human society from renewable resources. In this context, achieving atom‐economical and energy‐efficient conversion with high selectivity towards target products remains a key challenge. Recent developments in nanostructured catalysts address this challenge reporting remarkable performances in shape and morphology dependent catalysis by metals on nano scale in energy and environmental applications. In this review, most recent advances in synthesis of heterogeneous nanomaterials, surface characterization and catalytic performances for hydrogenation and oxidation for biorenewables with plausible mechanism have been discussed. The perspectives obtained from this review paper will provide insights into rational design of active, selective and stable catalytic materials for sustainable production of value‐added chemicals from biomass resources.     

Conversion of methanol to hydrocarbons: how zeolite cavity and pore size controls product selectivity

Liquid hydrocarbon fuels play an essential part in the global energy chain, owing to their high energy density and easy transportability. Olefins play a similar role in the production of consumer goods. In a post-oil society, fuel and olefin production will rely on alternative carbon sources, such as biomass, coal, natural gas, and CO(2). The methanol-to-hydrocarbons (MTH) process is a key step in such routes, and can be tuned into production of gasoline-rich (methanol to gasoline; MTG) or olefin-rich (methanol to olefins; MTO) product mixtures by proper choice of catalyst and reaction conditions. This Review presents several commercial MTH projects that have recently been realized, and also fundamental research into the synthesis of microporous materials for the targeted variation of selectivity and lifetime of the catalysts.     

Principles of searching for catalysts for deep conversion of fossil solid fuels and renewable organic raw materials

Approaches developed and used in practice for searching catalysts for the deep conversion of fossil coals and plant biomass are considered. The application of catalysts to the conversion of solid organic raw materials into liquid and gaseous fuels is discussed. The successful use of catalysts in the manufacture of valuable chemical products from plant polymers is exemplified.     

Catalytic conversion of lignocellulosic biomass to fine chemicals and fuels

Lignocellulosic biomass is the most abundant and bio-renewable resource with great potential for sustainable production of chemicals and fuels. This critical review provides insights into the state-of the-art accomplishments in the chemocatalytic technologies to generate fuels and value-added chemicals from lignocellulosic biomass, with an emphasis on its major component, cellulose. Catalytic hydrolysis, solvolysis, liquefaction, pyrolysis, gasification, hydrogenolysis and hydrogenation are the major processes presently studied. Regarding catalytic hydrolysis, the acid catalysts cover inorganic or organic acids and various solid acids such as sulfonated carbon, zeolites, heteropolyacids and oxides. Liquefaction and fast pyrolysis of cellulose are primarily conducted over catalysts with proper acidity/basicity. Gasification is typically conducted over supported noble metal catalysts. Reaction conditions, solvents and catalysts are the prime factors that affect the yield and composition of the target products. Most of processes yield a complex mixture, leading to problematic upgrading and separation. An emerging technique is to integrate hydrolysis, liquefaction or pyrolysis with hydrogenation over multifunctional solid catalysts to convert lignocellulosic biomass to value-added fine chemicals and bio-hydrocarbon fuels. And the promising catalysts might be supported transition metal catalysts and zeolite-related materials. There still exist technological barriers that need to be overcome (229 references).     

Autohydrolysis of Tropical Agricultural Residues by Compressed Liquid Hot Water Pretreatment

Pretreatment is an essential step in biorefineries for improving digestibility of recalcitrant agricultural feedstocks prior to enzymatic hydrolysis to composite sugars, which can be further converted to fuels and chemicals. In this study, autohydrolysis by compressed liquid hot water (LHW) pretreatment of various tropical agricultural residues including sugarcane bagasse (BG), rice straw (RS), corn stover (CS), and empty palm fruit bunch (EPFB) was investigated. It was found that LHW pretreatment at 200 °C for 5–20 min resulted in high levels of hemicellulose solubilization into the liquid phase and marked improvement on enzymatic digestibility of the solid cellulose-enriched residues. The maximal yields of glucose and pentose were 409.8–482.7 mg/g and 81.1–174.0 mg/g of pretreated substrates, respectively. Comparative analysis based on severity factor showed varying susceptibility of biomass to LHW in the order of BG> RS> CS> EPFB. Structural analysis revealed surface modification of the pretreated biomass along with an increase in crystallinity index. Overall, 75.7–82.3 % yield of glucose and 27.4–42.4 % yield of pentose from the dried native biomass was recovered in the pretreated solid residues, while 18.3–29.7 % of pentoses were recovered in the liquid phase with dehydration by-product concentration under the threshold for ethanologens. The results suggest the potential of LHW as an efficient pretreatment strategy for implementation in biorefineries operated using various seasonal agricultural feedstocks.     

Bio-refinery as the bio-inspired process to bulk chemicals

This paper describes several examples of knowledge-intensive technologies for the production of chemicals from biomass, which take advantage of the biomass structure in a more efficient way than the production of fuels or electricity alone. The depletion in fossil feedstocks, increasing oil prices, and the ecological problems associated with CO(2) emissions are forcing the development of alternative resources for energy, transport fuels, and chemicals, such as the replacement of fossil resources with CO(2) neutral biomass. Allied with this is the conversion of crude oil products utilizes primary products (ethylene, etc.) and their conversion into either materials or (functional) chemicals with the aid of co-reagents such as ammonia, by various process steps to introduce functionalities such as -NH(2) into the simple structures of the primary products. Conversely, many products found in biomass often contain functionalities. Therefore, it is attractive to exploit this in order to by-pass the use, and preparation of, co-reagents as well as to eliminate various process steps by utilizing suitable biomass-based precursors for the production of chemicals.     

Selective extraction and conversion of lignin in actual biomass to monophenols: A review

Our over dependency on the fossil resource for industrial chemicals and fuels faces great challenges.Recently, the production of monophenols from lignin in lignocellulosic biomass is regarded as a promising process for sustainable biofuels. This article discusses the conversion of lignin in actual biomass directly to monophenols. The two step way including extraction of lignin from biomass and further degradation of the lignin oligomers to monophenols is especially discussed. The obtained monophenols can also be converted to chemicals with low-oxygen content via hydrodeoxygenation process. For extraction of lignin,co-solvent system is the most adopted for hydrolysis or solvolysis of lignin assisted by acid or alkaline catalysts. The structure of the obtained oligomers derived from lignin is discussed in detail. For lignin depolymerization, hydrogenolysis is an efficient method with the use of gaseous hydrogen or alcohols as hydrogen source. At the meantime, depolymerization mechanism and the route for repolymerization of the reaction intermediates are presented here. In hydrodeoxygenation process, metal catalysts, especially noble metal catalysts are required. The precise effects of the reaction solvents and catalysts on extraction and degradation of lignin need to be further investigated, and this will benefit to design more efficient strategies for lignin utilization.     

Solar Electricity and Solar Fuels: Status and Perspectives in the Context of the Energy Transition

The energy transition from fossil fuels to renewables is already ongoing, but it will be a long and difficult process because the energy system is a gigantic and complex machine. Key renewable energy production data show the remarkable growth of solar electricity technologies and indicate that crystalline silicon photovoltaics (PV) and wind turbines are the workhorses of the first wave of renewable energy deployment on the TW scale around the globe. The other PV alternatives (e.g., copper/indium/gallium/selenide (CIGS) or CdTe), along with other less mature options, are critically analyzed. As far as fuels are concerned, the situation is significantly more complex because making chemicals with sunshine is far more complicated than generating electric current. The prime solar artificial fuel is molecular hydrogen, which is characterized by an excellent combination of chemical and physical properties. The routes to make it from solar energy (photoelectrochemical cells (PEC), dye‐sensitized photoelectrochemical cells (DSPEC), PV electrolyzers) and then synthetic liquid fuels are presented, with discussion on economic aspects. The interconversion between electricity and hydrogen, two energy carriers directly produced by sunlight, will be a key tool to distribute renewable energies with the highest flexibility. The discussion takes into account two concepts that are often overlooked: the energy return on investment (EROI) and the limited availability of natural resources—particularly minerals—which are needed to manufacture energy converters and storage devices on a multi‐TW scale.     

乳酸酯氧化脱氢制备丙酮酸酯的研究进展

生物质资源替代化石资源制取燃料和化学品已成为发展可再生能源化工的重要研究方向之一。本文综述了近年来以生物质平台分子乳酸酯为原料制备丙酮酸酯的研究工作,主要涉及的反应包括气相催化反应、液相催化反应和光催化反应。详细讨论了各种类型的催化剂对反应性能的影响;最后,对乳酸酯催化转化制取丙酮酸酯的发展前景进行了展望。     

High Performance Bifunctional Electrocatalysts Designed Based on Transition-Metal Sulfides for Rechargeable Zn–Air Batteries

Due to the energy crisis by the excessive consumption of fossil fuels, Zinc–air batteries (ZABs) with high theoretical energy density have attracted people‘s attention. The overall performance of ZABs is largely determined by the air cathode catalyst. Therefore, it is necessary to develop high-efficiency and low-cost bifunctional catalysts to replace noble metal catalysts to promote the development of ZABs. Among a variety of cathode catalysts, TMS has become a research hotspot in recent years because of its better electrical conductivity than metal phosphides and metal oxides. In this work, we focus on the means of improving the electrocatalytic performance of transition-metal sulfides (TMS) providing ideas for us to rationally design high-performance catalysts. Furthermore, the performance improvement law between catalyst performance and ZABs is also discussed in this work. Finally, some challenges and opportunities faced in the research of TMS electrocatalysis are briefly proposed, and strategies for improving the performance of ZABs are prospected.     

Iron‐Based Molecular Water Oxidation Catalysts: Abundant,Cheap, and Promising

An efficient and robust water oxidation catalyst based on abundant and cheap materials is the key to converting solar energy into fuels through artificial photosynthesis for the future of humans. The development of molecular water oxidation catalysts (MWOCs) is a smart way to achieve promising catalytic activity, thanks to the clear structures and catalytic mechanisms of molecular catalysts. Efficient MWOCs based on noble‐metal complexes, for example, ruthenium and iridium, have been well developed over the last 30 years; however, the development of earth‐abundant metal‐based MWOCs is very limited and still challenging. Herein, the promising prospect of iron‐based MWOCs is highlighted, with a comprehensive summary of previously reported studies and future research focus in this area.     

Will Zeolite‐Based Catalysis be as Relevant in Future Biorefineries as in Crude Oil Refineries?

Transition from petroleum‐ to biomass‐based fuel economy will require new conversion strategies. In a petroleum refinery, particular hydrocarbon fractions from crude oil are catalytically converted into high‐grade fuels. Certain zeolite catalysts are performing exceptionally well. Unlike petroleum fractions, biomass‐derived compounds have a high oxygen content requiring low‐temperature catalytic aqueous phase processes for selective conversion and stability of zeolite catalysts in hot liquid water. It will be shown that recent developments in zeolite synthesis and modification allow adapting zeolite properties to achieve selective conversion of biomass compounds/fractions as well.     

Emphasis on the Properties of Metal-Containing Zeolites Operating Outside the Comfort Zone of Current Heterogeneous Catalytic Reactions

The development of catalysts that can operate under exceptionally harsh and unconventional conditions is of critical importance for the transition of the energy and chemicals industries to low-emission and renewable chemical feedstocks. In this review we will highlight materials and more specifically metal-containing zeolite catalysts that have been tested under harsh reaction conditions such as high temperature light alkane conversion and biomass valorization. Particular attention will be given to studies that explore the stability and recyclability of metal-containing zeolite catalysts operating in continuous modes. Metal-containing zeolites are considered as an important class of catalysts operating outside the comfort zone of current heterogeneous catalytic reactions in both gas and liquid phase reactions. The relationship between the properties of the metal-containing zeolite and catalytic performance will be explored.     

生物质利用新途径:多元醇催化合成可再生燃料和化学品

日益严重的全球性能源和环境问题促使开发利用可再生的生物质资源成为当前研究的一个热点。本文概述了生物质基多元醇合成燃料和化学品来实现生物质转化利用的一些最新进展,特别是集中介绍了甘油和山梨醇等多元醇催化水相重整合成氢气和液体烃等燃料、催化选择氢解和氧化合成高附加值化学品或化学中间体等方面的进展,分析了存在的问题和可能的解决措施以及今后的发展趋势,指出生物质基多元醇将成为今后合成可再生燃料和化学品的新型平台分子。     

电化学二氧化碳还原中的铜基催化剂

由于不断增加的二氧化碳排放导致全球变暖,且能源短缺等问题日益恶化,将二氧化碳电化学还原为高附加值化学品和燃料引起了极大的兴趣,设计高效催化剂对实现二氧化碳的高效选择性转化具有重要意义. 在所探索的各种催化剂中,铜基催化剂具有良好的开发潜力,可用于烃类生产. 本文综述了铜基电化学二氧化碳转化材料的最新进展. 分别从尺寸结构到不同形式（合金、氧化物）的铜基催化剂,以及分子催化剂等方面展开,重点讨论铜基催化剂上二氧化碳电解还原的反应机理. 最后,对未来高效铜基催化剂的设计提出展望,以促进二氧化碳转化的可持续发展.     

生物质利用新途径:多元醇催化合成可再生燃料和化学品

日益严重的全球性能源和环境问题促使开发利用可再生的生物质资源成为当前研究的一个热点.本文概述了生物质基多元醇合成燃料和化学品来实现生物质转化利用的一些最新进展,特别是集中介绍了甘油和山梨醇等多元醇催化水相重整合成氢气和液体烃等燃料、催化选择氢解和氧化合成高附加值化学品或化学中间体等方面的进展,分析了存在的问题和可能的解决措施以及今后的发展趋势,指出生物质基多元醇将成为今后合成可再生燃料和化学品的新型平台分子.