Progress in the design of zeolite catalysts for biomass conversion into biofuels and bio-based chemicals

This article reviews the recent advances in the development of zeolite catalysts for biomass valorization processes to produce both biofuels and/or bio-based chemicals, which is an emerging and fast expanding field. The work deals with different types of feedstocks, including vegetable oils, lignocellulose and sugars, as well as with a number of relevant intermediates and platform molecules. Transformation of biomass into valuable products is hindered by a number of factors, mainly related to its complex composition, as biomass typically consists of bulky molecules with high oxygen content. Accordingly, biomass processing usually requires the combination of multiple steps and severe conditions, hence concepts like atom efficiency, product selectivity, and catalyst deactivation become of special relevance. A great progress has been achieved in the past years engineering the properties of zeolites for being adapted to the challenges associated to biomass valorization. The possibility of tailoring the main physicochemical properties of zeolites has become now a reality, being the major reason that explains the success achieved by this class of materials in a growing variety of biomass conversion pathways, as those described in this work: catalytic cracking and pyrolysis, hydrotreatments, with special relevance for hydrodeoxygenation processes, as well as in a high number of condensation, isomerization, and dehydration reactions. Thus, the development of hierarchical zeolites, exhibiting enhanced accessibility, and the possibility of introducing and combining in a controlled way different types of active sites (Brønsted and Lewis acid centers, basic sites, and metal phases) are the main basis of the excellent performance of zeolites in numerous biomass conversion routes.     

A review on ex situ catalytic fast pyrolysis of biomass

Catalytic fast pyrolysis (CFP) is deemed as the most promising way to convert biomass to transportation fuels or value added chemicals. Most works in literature so far have focused on the in situ CFP where the catalysts are packed or co-fed with the feedstock in the pyrolysis reactor. However, the ex situ CFP with catalysts separated from the pyrolyzer has attracted more and more attentions due to its unique advantages of individually optimizing the pyrolysis conditions and catalyst performances. This review compares the differences between the in situ and ex situ CFP operation, and summarizes the development and progress of ex situ CFP applications, including the rationale and performances of different catalysts, and the choices of suitable ex situ reactor systems. Due to the complex composition of bio-oil, no single approach was believed to be able to solve the problems completely among all those existing technologies. With the increased understanding of catalyst performances and reaction process, the recent trend toward an integration of biomass or bio-oil fractionation with subsequent thermo/biochemical conversion routes is also discussed.     

生物质热解制生物油及其提质研究现状

生物质能源作为可再生能源的重要组成部分,其综合高效利用在能源替代与补充、保护生态环境等方面具有重要的战略意义。生物油是生物质通过热裂解技术获得的液体产物,具有能量密度较高、环境友好、可再生及可直接输送等优点,可替代传统化石燃料推广使用,解决日益严重的能源紧缺与环境污染等问题。生物质热解制油技术的开发与利用,已成为新世纪可持续能源研究领域的重要课题之一。总结了近年来生物质热解制油技术的主要研究进展,重点关注热解反应器、催化热解技术与生物油的提质利用方面的研究,介绍了碱金属、氧化物和分子筛3种生物质热解催化剂,以及乳化、催化加氢、催化裂解、催化酯化和重整制氢5种生物质提质方法,最后对生物质热解技术的现状及发展趋势进行了总结和概括。     

生物质制芳烃技术进展与发展前景

对目前利用生物质生产芳烃几种路线以及研究进展进行评述。介绍了前景较好的代表性工艺,如：Anellotech公司开发的生物质热解制芳烃（Bio-AromaticsTM）工艺、Virent公司开发的生物基氢解糖类经过催化转化制PX（Bio-FormingTM）工艺以及Gevo公司开发的生物质异丁醇制芳烃工艺,并详细分析了各工艺的原料来源、工艺流程、工艺条件等特点。分析几种生物质芳烃工艺生产成本,并对照传统石脑油裂解重整制芳烃生产成本,分析各工艺经济性后,得出结论：Anellotech公司开发的生物质热解制芳烃工艺经济性成本与经济性最佳。在此基础上,提出今后生物质制芳烃的研究应当以提高原料利用效率、增加芳烃产率和选择性为重点,开发适合生物质转化反应的催化剂和反应器。     

碱土金属氧化物基催化剂催化热解生物质研究进展

快速热解是生物质高效转化利用的重要方法之一,然而其目标产物生物油因含氧量高、组分复杂等不足而难以直接利用。通过在热解体系中引入碱土金属氧化物基催化剂,可以将热解产物中的氧元素以CO₂和H₂O等方式脱除,从而实现生物油品质的提升。总结了典型碱土金属氧化物基催化剂对生物质催化热解过程中发生的酮基化、羟醛缩合、开环和侧链断裂反应及机理,讨论了催化剂类型（CaO、MgO、基于碱土金属氧化物的分子筛和活性炭等）、生物质原料、温度、催化剂用量、停留时间、催化方式、催化剂失活等因素对生物油产率与品质的影响,并对生物质催化热解制备高品质生物油及其应用进行了展望。     

生物质能源转化技术与应用(Ⅲ)——生物质热解液体燃料油制备和精制技术

生物质能源是唯一可再生、可替代化石能源转化成气态、液态和固态燃料以及其它化工原料或者产品的碳资源。随着化石资源的枯竭和人类对全球性环境问题的关注,生物质能源替代化石能源利用的研究和开发,已成为国内外众多学者研究和关注的热点。本系列讲座主要讲述以生物质资源为主要原料,通过不同途径转化为洁净的、高品位的气体、液体或固体燃料。本讲主要综述了生物质高压液化、快速热解液化制备液体燃料油技术现状、工艺及设备,并在总结生物质热解液体燃料油特性的基础上,总结了生物热解液体燃料油的物理法精制技术(包括脱水、添加溶剂和乳化)和化学法精制技术(包括催化加氢、催化裂解、催化酯化、水蒸气重整)的研究现状,并对其精制机理、优缺点进行了分析。随着制备和精制技术的深入研究,生物质热解液体燃料油可望替代汽油、柴油等化石燃料而越来越受到人们的关注。     

Stability of nickel-containing catalysts for hydrodeoxygenation of biomass pyrolysis products

Heterogeneous catalysts for the hydrotreatment (hydrodeoxygenation) of biomass fast pyrolysis products (bio-oil) for the production of fuel hydrocarbons are considered. Hydrodeoxygenation catalysts are conventionally divided into three groups: catalysts based on noble metals, sulfided catalysts for desulfurization, and non-sulfided catalysts based on supported transition metals. The main emphasis in this work is on nickel-based non-sulfided catalytic systems as the ones most promising for the hydrotreatment of feedstocks with low content of sulfur. In light of specific features of bio-oil (high acidity and viscosity, low thermal stability), requirements are formulated that must be met in developing hydrodeoxygenation catalysts and processes based on them, especially specifications for the stability of catalysts of this type and their ability for multiple regeneration.     

生物质油与蜡油在FCC装置共炼的多目标优化

生物燃料作为一种可部分代替化石燃料的潜在能源具有绿色、可再生、无硫等优势,但其生产成本一般较高。生物质油与蜡油在催化裂化装置中的共炼通过利用炼厂已有设备可有效降低生物炼厂的投资费用进而降低生物燃料的生产成本。为同时降低共炼过程的经济费用和环境影响以筛选最优的生物质原料和生物质油制备技术,采用Eco-indicator 99方法量化共炼过程的环境影响,提出了针对该过程的多目标优化模型。结果表明：无论是降低经济费用还是减少环境影响,采用催化热解技术制备生物质油优于快速热解;不同目标下所获得的最优生物质原料不同;生物质原料在费用和环境影响中占比最大。因此,在对共炼过程进行优化时,需要考虑过程对环境的影响,而降低生物质原料的消耗对共炼过程费用和环境影响的降低最为有效。     

生物质油加氢脱氧精制研究进展

随着石油能源渐趋匮乏,生物质高温裂解制备生物质油备受关注。而生物质油中氧含量高达40%,这将影响生物质油的稳定性、极性、热值、粘度和酸性等,应必须对其进行加氢脱氧精制处理。文中介绍了裂解生物质油的组成分布和特点,阐述了裂解生物质油加氢脱氧精制的反应过程和影响因素。     

催化型多孔陶瓷球制备及催化玉米秸秆热解

针对生物质热解液化过程中生物油品质差的问题,本文以陶瓷球作热载体为研究基础,制备了5种负载金属氧化物（ZnO、NiO、CeO₂、Cr₂O₃、Fe₂O₃）的多孔陶瓷球,在固定床反应器上研究多孔陶瓷球催化剂对玉米秸秆热解过程的催化效果。结果表明：多孔陶瓷球基体在热解过程中有一定催化活性,经浸渍改性处理后,都能促进生物油产率的提高,其中Ni基多孔陶瓷球热解的产率高达41.62%。多孔陶瓷球负载的5种金属氧化物可促使生物油中酚类、呋喃类物质的含量明显增加,酸类物质的含量明显降低,且种类减少,其中CeO₂降酸效果显著,降低幅度为37.15%。此外,催化型多孔陶瓷球的引入促进了不可冷凝气中C _n H _m （n≥2）的生成,烯烃类中乙烯的增长幅度最大,为50.53%,同时生物炭的理化特性在一定程度上得到改善和提高。     

轻烃催化裂解制低碳烯烃反应规律与原料特征化

利用小型固定床实验装置对比研究了轻烃模型化合物的催化裂解性能,从优到劣的顺序依次是正构烯烃、正构烷烃、环烷烃、异构烷烃、芳香烃。正构烷烃、异构烷烃与环烷烃催化裂解的总低碳烯烃收率有较大差别,但是总低碳烯烃选择性却均在56.57%左右。研究了直馏石脑油的催化裂解性能,发现乙丙烯收率和总低碳烯烃收率随反应温度的升高及重时空速的降低而逐渐增大;在反应温度680℃、重时空速4.32 h^-1和水油稀释比0.35的条件下,乙丙烯收率35.87%（质量）,总低碳烯烃收率为41.94%（质量）。针对轻烃催化裂解提出了原料特征化参数KF,它是原料H/C原子比、相对密度与分子量的函数,能较好地表征轻烃原料的催化裂解性能。     

动植物油生产清洁燃料和低碳烯烃的替代加工工艺

Since the production cost of biodiesel is now the main hurdle limiting their applicability in some areas, catalytic cracking reactions represent an alternative route to utilization of vegetable oils and animal fats. Hence, catalytic transformation of oils and fats was carried out in a laboratory-scale two-stage riser fluid catalytic cracking （TSRFCC） unit in this work. The results show that oils and fats can be used as FCC feed singly or co-feeding with vacuum gas oil （VGO）, which can give high yield （by mass）of liquefied petroleum gas （LPG）, C2-C4 oletms, tor example 45% LPG, 47% C2-C4 olefins, and 77.6% total liquid yield produced with palm oil cracking. Co-feeding with VGO gives a high yield of LPG （39.1%） and propylene （18.1%）. And oxygen element content is very low （about 0.5%） in liquid products, hence, oxygen is removed in the form of H2O, CO and CO2. At the same time, high concentration of aromatics （C7-C9 aromatics predominantly） in the gasoline fraction is obtained after TSRFCC reaction of palm oil, as a result of large amount of hydrogen-transfer, cyclization and aromatization reactions, Additionally, most of properties of produced gasoline and diesel oil fuel meet the requirements of national standards, containing little sulfur. So TSRFCC technology is thought to be an alternative processing technology leading to production of clean fuels and light olefins.     

Catalysis in biomass processing

Biomass has in recent years been considered as a raw material for the production of fuels and chemicals. This work discusses the reasons for the increased interest in mainly lignocellulosic biomass. Gasification, pyrolysis, and depolymerization by hydrolysis are analyzed as key biomass technology. We also discuss which of the sugars obtained via depolymerization by hydrolysis can be processed into fuel or key intermediates of the chemical industry. Lignocellulosic biomass contains such extractants as fatty acids and terpenes, and we therefore describe the catalytic reactions of these substances for the synthesis of fuels and chemicals. Some typical reactions of biomass processing (oxidation, hydrogenation, cracking, etc.) are conceptually close to the process widely known in the refining and chemical industries. There are, however, other considerations due to, e.g., the large number of functional (hydroxyl and other) groups, and the processing of biomass components therefore requires dehydration, aldol condensation, ketonization, decarboxylation, etc. We cover the fundamentals of the approaches to selecting catalysts for these reactions.     

生物质三组分与低密度聚乙烯共催化热解制取轻质芳烃的协同作用机理

生物质与废塑料共催化快速热解是制取轻质芳烃的重要途径。 采用不同种类的分子筛催化剂,首先研究了分子筛种类对杨木、生物质三组分和低密度聚乙烯（LDPE）单独催化快速热解轻质芳烃产率的影响,其次研究了生物质三组分与LDPE在共催化热解过程中的协同作用机理。结果表明：在杨木、生物质三组分和LDPE单独催化快速热解时,HZSM-5（25）催化剂体现出最高的轻质芳烃产率;在杨木和LDPE共催化快速热解时,随着LDPE质量的增加,轻质芳烃的产率呈先升高后降低趋势;在生物质三组分和LDPE共催化快速热解时,纤维素和半纤维素热解的呋喃类中间产物与LDPE热解的轻烯烃中间产物易发生“双烯合成”反应,表现出较强的协同催化作用,促进轻质芳烃的生成,而木质素则抑制轻质芳烃生成。     

Deactivating species in the transformation of crude bio-oil with methanol into hydrocarbons on a HZSM-5 catalyst

A study has been carried out by using different techniques (TPO, FTIR, Raman, ¹³C NMR, GC/MS of the coke dissolved in CH₂Cl₂) on the nature of the coke deposited on a HZSM-5 catalyst modified with Ni in the transformation of the crude bio-oil obtained by flash pyrolysis of lignocellulosic biomass (pine sawdust) into hydrocarbons. The reaction system has two steps in-line. In the first one, the components of crude bio-oil derived from the pyrolysis of biomass lignin are polymerized at 400 °C. In the second one, the remaining volatile oxygenates are transformed into hydrocarbons in a fluidized bed catalytic reactor at 450 °C. The reaction has been carried out with different bio-oil/methanol mass ratios in the feed (from 100/0 to 0/100). Co-feeding methanol significantly attenuates coke deposition, and the nature of the coke components varies according to the bio-oil/methanol ratio in the feed. When bio-oil is co-fed, the coke deposited on the catalyst has a significant content of oxygenates and oxo-aromatics and consists of two fractions, identified by temperature programmed oxidation, corresponding to external and internal coke in the zeolite crystals. The fraction of external coke is soluble in CH₂Cl₂, with a high content of oxygenates and oxo-aromatics, and is generated by polymerization of products derived from biomass lignin pyrolysis activated by the zeolite acid sites. The fraction of coke retained within the zeolite crystals is partially insoluble and is formed by several routes: from the intermediates in the transformation of both methanol and bio-oil oxygenates into hydrocarbons; by evolution of the other coke fraction; from the hydrocarbons (with high aromatics content) in the reaction medium.     

生物质双级催化热解制备燃料化学品的研究进展

生物质热解所得目标产物生物油因高含氧量、组分复杂等问题难以直接应用,通过使用适宜的催化剂升级热解蒸气可实现生物油的脱氧提质。本文基于前人研究,首先总结了生物质催化热解中金属氧化物和分子筛催化剂的结构特点、催化原理与催化效果。然后详细介绍了微介孔复合型、金属氧化物/ZSM-5复合型双级催化体系的构建原理、催化模式及其对于生物质催化热解产物分布规律产生的影响,并说明了双级催化体系的可行性与实用性;同时概述了影响生物质催化热解的其他因素,包括原料特性、工艺参数、操作模式等。最后针对目前双级催化热解研究与发展中存在的问题,对进行双级催化模式的比较研究、改进催化体系以降低生产成本、发掘双级催化剂的多种使用价值等方向提出了展望。     

催化裂解反应条件对产物收率的影响

增产低碳烯烃、轻质芳烃等产物是催化裂解技术发展的趋势,反应条件是影响催化裂解产物分布的关键因素。介绍催化裂解过程涉及的反应机理,概述反应温度、剂油质量比、停留时间(空速)、水油质量比等反应条件,裂解装置和原料油性质对产物收率的影响,结合工业实例分析反应条件对产物收率的影响。     

纤维素快速热解反应气体的在线催化裂解

通过浸渍法制备MHZSM-5(M Fe,Zr,Co)催化剂,采用激光粒度分析仪、比表面积及孔径分析仪和X射线衍射仪(XRD)对催化剂的性质进行表征,并在立式两段加热炉上进行纤维素快速热解蒸汽的在线催化实验。对不同催化剂条件下的产物分布特性及生物油组成特性进行分析,结果表明,随着催化剂的引入,液相产率从52.06%最大下降至23.63%,气相产率从42.39%最大提高至70.84%,CoHZSM-5对于热解蒸汽的催化气化效果最为明显;纤维素快速热解生物油中以1,6-脱水-β-D-吡喃葡萄糖(左旋葡聚糖)为主,引入催化剂对纤维素热解蒸汽进行在线催化重整后,产物中芳烃类物质显著增加,以FeHZSM-5和ZrHZSM-5效果最佳;HZSM-5催化下生物油中左旋葡聚糖的含量提高至63.78%;催化后热解油中乙酸及丙酸含量均减少,但降低幅度有限。综合催化剂对产率及组分的影响效果来看,FeHZSM-5和ZrHZSM-5对纤维素快速热解蒸汽的催化调控作用较为显著。     

生物质微波热解产生物油的影响因素研究进展

生物质作为可再生资源具有低成本、分布广泛且易得等优点,生物质能的开发利用可有效缓解能源压力,减少环境污染。微波热解技术是生产燃料油和高附加值化学品的有效方法之一,与传统的热解相比,微波热解具有加热速率快、均匀性好、选择性加热、节能与易于控制等优点。在简单分析微波热解产物分布的基础上,详细综述了近年来微波热解生物油产率的影响因素,主要包括热解温度、功率、吸波剂、催化剂、原料预处理、加热时间、原料性质和物料尺寸等因素;最后,总结和展望了微波技术在生物质催化热解制备生物油领域应用中存在的问题、解决途径和发展前景。     

Recent advances in the catalytic pyrolysis of biomass

Biomass is considered as a renewable and alternative resource for the production of fuels and chemicals, since it is the only carbon and hydrogen containing resource that we can find in the world except for fossil resources, capable of being converted to hydrocarbons. The pyrolytic liquefaction of biomass is a promising way to convert biomass to useful products. This paper briefly surveys the present status of the direct catalytic pyrolysis for the liquefaction of biomass. The direct use of catalysts could decrease the pyrolysis temperature, increase the conversion of biomass and the yield of bio-oil, and change the distribution of the pyrolytic liquid products then improve the quality of the bio-oil obtained. The fact that biomass is in solid state present great challenges for its conversion and for the effective use of catalysts due to the bad heat transfer characteristics and bad mass transfer properties. These barriers appeal for the development of a new catalyst and new catalytic process as well as the integration of both. Process design and process intensification are of significant importance in the catalytic conversion of biomass.