Ester fuels and chemicals from biomass

Bench-scale research demonstrated that using an efficient esterification step to integrate an ethanol with a carboxylic acid fermentation stream offers potential for producing valuable ester feedstocks and fuels. Polar organic acids from bacterial fermentations are difficult to extract and purify, but formation of the ammonium salts and their conversion to esters facilitates the purifications. An improved esterification procedure gave high yields of esters, and this method will lower the cost of ester production. Fuel characteristics have been determined for a number of ester-gasoline blends with promising results for lowering Reid vapor pressure and raising octane numbers.     

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).     

Synergies between bio- and oil refineries for the production of fuels from biomass

As petroleum prices continue to increase, it is likely that biofuels will play an ever-increasing role in our energy future. The processing of biomass-derived feedstocks (including cellulosic, starch- and sugar-derived biomass, and vegetable fats) by catalytic cracking and hydrotreating is a promising alternative for the future to produce biofuels, and the existing infrastructure of petroleum refineries is well-suited for the production of biofuels, allowing us to rapidly transition to a more sustainable economy without large capital investments for new reaction equipment. This Review discusses the chemistry, catalysts, and challenges involved in the production of biofuels.     

Synthesis gas as substrate for the biological production of fuels and chemicals

Synthesis gas provides a simple substrate for the production of fuels and chemicals. Synthesis gas can be produced via established technologies from a variety of feedstocks including coal, wood, and agricultural and municipal wastes. The gasification is thermally efficient and results in complete conversion of the feedstock to fermentable substrate.Clostridium ljungdahlii grows on the synthesis gas components, carbon monoxide, hydrogen, and carbon dioxide. Production of acetic acid and ethanol accompanies growth with synthesis gas as sole source of energy and carbon. Rate and yield parameters are compared forC. ljungdahlii grown on carbon monoxide, or hydrogen with carbon dioxide.

     

Bioelectronics and biometallocatalysis for production of fuels and chemicals by photosynthetic water splitting

Applied Biochemistry and Biotechnology - By inserting metallocatalysts (such as platinum, osmium, or ruthenium) at the reducing site of photosystem I (PSI), electrons that emerge from PSI can be...     

Cellulosic materials recovered from steam classified municipal solid wastes as feedstocks for conversion to fuels and chemicals

Applied Biochemistry and Biotechnology - A process has been developed for the treatment of municipal solid waste to separate and recover the cellulosic biomass from the nonbiomass components. The...     

生产运输燃料和有机化学品生物催化体系的新进展

总结了细菌作为生物催化剂的特征和应用的新进展,预测了未来发展趋势。深入讨论了微藻系统的发展,包括PetroAlgae公司和中国石化石油化工科学研究院微藻实验室的一些进展。     

Modern approaches to the production of carbon materials from vegetable biomass

Recent trends in methods for the preparation of porous carbon materials (PCM) from vegetable biomass by physical and chemical activation methods are analyzed. Data on the effect of activating agents and also other parameters on the textural characteristics of PCMs were classified. A new direction for the production of PCMs was discovered in the use of high-ash biomass.     

Integrated catalytic process for obtaining liquid fuels from renewable lignocellulosic biomass

An integrated process for obtaining liquid biofuels is reported. The process is based on the separation of a lignocellulosic feedstock into cellulose and low-molecular-weight lignin (LMWL) followed by their conversion into two types of liquid biofuels, namely, hydrocarbon mixtures and bioalcohols. Different methods of wood fractionation into cellulose and LMWL—mechanical, steam explosion, and selective oxidation methods and their combinations—are compared. The amount of cellulose derived from wood and the amount of hydrolysate obtained from this cellulose for ethanol biosynthesis are determined by the efficiency of the method used for the fractionation of the lignocellulosic material. The best results are achieved by combining mechanical activation and subsequent catalytic oxidation of wood. Use of the resulting high-quality glucose solution, which are free of pentoses—sugars inhibiting ethanol biosynthesis—allows the alcohol yield to be increased by 30–35%. Liquid hydrocarbon mixtures enriched with phenols and products of their alkylation with ethanol have been obtained by thermal processing of LMWL in ethanol at an elevated pressure.     

Evaluation of different biomass materials as feedstock for fermentable sugar production

Saline crops and autoclaved municipal organic solid wastes were evaluated for their potential to be used as feedstock for fermentable sugar production through dilute acid pretreatment and enzymatic hydrolysis. The saline crops included two woods, athel (Tamarix aphylla L) and eucalyptus (Eucalyptus camaldulensis), and two grasses, Jose tall wheatgrass (Agropyron elongatum), and creeping wild rye (Leymus triticoides). Each of the biomass materials was first treated with dilute sulfuric acid under selected conditions (acid concentration =1.4% (w/w), temperature =165 degrees C, and time =8 min) and then treated with the enzymes (cellulases and beta-glucosidase). The chemical composition (cellulose, hemicellulose, and lignin contents) of each biomass material and the yield of total and different types of sugars after the acid and enzyme treatment were determined. The results showed that among the saline crops evaluated, the two grasses (creeping wild rye and Jose tall wheatgrass) had the highest glucose yield (87% of total cellulose hydrolyzed) and fastest reaction rate during the enzyme treatment. The autoclaved municipal organic solid wastes showed reasonable glucose yield (64%). Of the two wood species evaluated, Athel has higher glucose yield (60% conversion of cellulose) than eucalyptus (38% conversion of cellulose).     

木质纤维素中C-O键选择性活化和高效转化制化学品

高效转化来源丰富且可再生的木质纤维素制备化学品和燃料对建立可持续发展社会具有重要意义。木质纤维素利用的一条理想途径是将其主要成分纤维素、半纤维素和木质素在温和条件下高选择性地催化转化为关键平台化学品。本文综述了近年报道的有关纤维素、半纤维素和木质素或其模型分子中C–O键选择性活化生成葡萄糖、葡萄糖衍生物(包括葡萄糖苷、六元醇和葡萄糖酸)、木糖、阿拉伯糖和芳香化合物的新催化剂和新策略,阐述了决定催化性能的关键因素。本文还讨论了相关反应机理以深入理解C–O键选择性活化。纤维素由葡萄糖单元通过β-1,4-糖苷键连接而成,通过水解反应,选择性切断这些糖苷键可以获得葡萄糖或其低聚物。鉴于葡萄糖在水热条件下不稳定,发展纤维素温和条件下水解的酸催化剂至关重要。众多研究表明,均相酸催化剂(如无机酸,杂多酸等)具有强Br?nsted酸,在该水解反应中显示高的催化活性。另一方面,拥有强酸性基团-SO3H的固体酸也表现出优异的水解糖苷键性能,但是-SO3H官能团易于流失,限制了这类固体酸催化剂的循环使用。最近研究显示,一些催化剂尤其是碳材料上引入能够与纤维素形成氢键的官能团时,其催化纤维素水解性能显著增强。设计合成这类具备酸性位和氢键位协同效应的稳定固体酸催化剂是纤维素水解转化的一个颇具前景的研究方向。以醇替代水为溶剂实施纤维素醇解制葡萄糖苷是高效活化糖苷键的有效策略。杂多酸被证实为该醇解反应的高性能催化剂。在相同反应条件下,醇解产物葡萄糖苷较水解产物葡萄糖更为稳定,因此可以获得高的葡萄糖苷收率。开发稳定可重复利用的固体酸催化剂是纤维素醇解的关键。耦合水解与加氢或氧化反应可以直接将纤维素转化为相对稳定且具有广泛用途的多元醇或有机酸。目前已有一系列双功能催化剂被报道,这些催化剂通常组合了具备水解功能的液体酸或固体酸和具备加氢或氧化功能的贵金属或过渡金属(譬如Ru, Pt, Ni和Au)。其中杂多酸盐或含有磺酸官能团的固体酸负载Ru或Au双功能催化剂显示出优异的生成六元醇或葡萄糖酸的催化性能。半纤维素由葡萄糖、甘露糖、木糖、阿拉伯糖、半乳糖等单糖单元通过糖苷键连接而成,糖苷键选择性活化可生成各种单糖混合物。硫酸可以有效水解半纤维素,但是同时也易于催化所生成的单糖深度转化为呋喃及其衍生物。较之硫酸,酸性较弱的有机酸特别是二元羧酸(例如马来酸、草酸等)具有较高的单糖选择性。固体酸如酸性树脂,分子筛等亦可催化半纤维素水解反应,但树脂类催化剂中官能团的流失问题有待解决。木质素是由含甲氧基等取代基的苯丙烷单元通过一系列化学键连接而成的复杂大分子,其芳香单元间包括β-O-4,α-O-4和4-O-5等三种主要连接方式,选择性切断这些C–O键可获得高附加值的芳香化合物。水解和氢解是两类普遍用以活化木质素及其模型化合物C–O键的反应。酸和碱均可催化木质素及其模型化合物水解,但是通常需要苛刻条件获取高转化率。近期研究显示,通过对木质素Cα-OH预氧化,再以HCOOH/HCOONa实施水解反应,可以成功实现温和条件下有机溶剂提取木质素及其模型化合物的高效转化。另一方面,均相金属络合物(如Ni, Fe和Ru)或多相负载型金属催化剂(如Ni, Cu, Mo, Pt, Ru, Pd或Ru等)均可有效催化木质素及其模型化合物中C–O键氢解,获得芳烃化合物。在部分多相催化剂体系中,除C–O键活化断裂外,还伴随芳环深度加氢反应,产生较多环己烷衍生物。因此,设计合成具备氢解功能同时抑制过度加氢功能的催化剂是获得芳烃化合物的关键。     

Alternative fuels from biomass and their impact on carbon dioxide accumulation

Applied Biochemistry and Biotechnology - A number of transportation fuels can be produced from renewable resources. The major fractions of lignocellulosic biomass, cellulose and hemicellulose, can...     

Pressure swing adsorption for CO<Subscript>2</Subscript> capture in Fischer-Tropsch fuels production from biomass

Environmental concerns and oil price rises and dependency promoted strong research in alternative fuel sources and vectors. Fischer-Tropsch products are considered a valid alternative to oil derivatives having the advantage of being able to share current infrastructures. As a renewable source of energy, synthesis gas obtained from biomass gasification presents itself as a sustainable alternative. However, prior to hydrocarbon conversion, the bio-syngas must be conditioned, which includes the removal of carbon dioxide for subsequent sequestration and capture. A pressure swing adsorption cycle was developed for the removal and concentration of CO₂ from the bio-syngas stream. Activated carbon was chosen as adsorbent. The simulation results showed that it was possible to produce a (H₂ + CO) product with a H₂/CO stoichiometric ratio of 2.14 (suitable as feed stream for the Fischer-Tropsch reactor) and a CO₂ product with a purity of 95.18%. A CO₂ recovery of 90.3% was obtained. A power consumption of 3.36 MW was achieved, which represents a reduction of about 28% when compared to a Rectisol process with the same recovery.     

Biofuels and biomass-to-liquid fuels in the biorefinery: catalytic conversion of lignocellulosic biomass using porous materials

At a time when the focus is on global warming, CO(2) emission, secure energy supply, and less consumption of fossil-based fuels, the use of renewable energy resources is essential. Various biomass resources are discussed that can deliver fuels, chemicals, and energy products. The focus is on the catalytic conversion of biomass from wood. The challenges involved in the processing of lignocellulose-rich materials will be highlighted, along with the application of porous materials as catalysts for the biomass-to-liquids (BTL) fuels in biorefineries. The mechanistic understanding of the complex reactions that take place, the development of catalysts and processes, and the product spectrum that is envisaged will be discussed, along with a sustainable concept for biorefineries based on lignocellulose. Finally, the current situation with respect to upgrading of the process technology (pilot and commercial units) will be addressed.     

Selective electrocatalytic conversion of methane to fuels and chemicals

The increase in natural gas reserves makes methane a significant hydrocarbon feedstock. However, the direct catalytic conversion of methane into liquid fuels and useful chemicals remains a great challenge,and many studies have been devoted to this field in the past decades. Electrocatalysis is considered as an important alternative approach for the direct conversion of methane into value-added chemicals, although many other innovative methods have been developed. This review highlights recent advances in electrocatalytic conversion of methane to ethylene and methanol, two important chemicals. The electrocatalytic systems efficient for methane conversions are summarized with an emphasis on catalysts and electrolytes. The effects of reaction conditions such as the temperature and the acid–base property of the reaction medium are also discussed.