生物质高压液化技术影响因素分析及展望

文章介绍了生物质高压液化技术的优势及目前开展生物质高压液化技术的必要性和紧迫性,着重介绍了反应原料、反应温度、反应时间、反应压力、反应气氛、溶剂和催化剂等因素对生物质高压液化产物分布及产物性质的影响.指出了生物质高压液化技术目前存在的问题及今后的研究方向,以期为生物质高压液化技术的工业化发展提供指导.     

油棕废弃物及生物质三组分的热解动力学研究

主要利用热重分析仪(TG)对油棕废弃物和生物质的三组分(半纤维素,纤维素和木质素)的热解特性进行了系统研究,对比分析了热解特性,计算了其热解动力学参数,并研究了升温速率对生物质热解特性的影响。研究发现半纤维素和纤维素易于热降解而木质素难于热解;油棕废弃物的热解可以化分为:干燥、半纤维素热解、纤维素热解和木质素热解4个阶段;生物质的热解反应主要是一级反应,油棕废弃物的活化能很低,约为60kJ/kg;升温速率对生物质影响很大,随升温速率加快,生物质热解温度升高,热解速率降低。     

纤维素热解生物油特性研究

为深入了解生物质热解生物油的特性,对生物质的主要成分纤维素热解生物油的析出和演变特性进行研究。在固定床上研究纤维素在不同温度(280~550℃)下的快速与慢速热解以及不同气相停留时间对纤维素生物油特性与组成的影响。研究表明,纤维素快速热解生物油由左旋葡聚糖及大量脱水糖组成,还有少量呋喃衍生物(如糠醛、5-羟甲基糠醛等)。慢速热解时产生的脱水糖种类较少,但小分子化合物种类更多。随着气相停留时间的缩短,液体产物中左旋葡聚糖含量逐渐升高,酸、醛等小分子消失。     

玉米秆超临界醇解产物高效液相分析

采用高效液相色谱法(HPLC)对玉米秆超临界醇解产物作了初步尝试性分析.结果表明:玉米秆超临界醇解产物中可能含有大量极性强于苯酚的化合物,其中芳烃类物质以单环为主.进行HPLC紫外检测分析时最好采用双波长检测:在0～30 min采用220 nm检测,在30 min后采用210 nm检测.示差检测表明:液化产物中存在烷烃类物质.挥发除去溶剂的样品与直接进样的色谱图对比表明:液化产物在溶剂挥发过程中可能损失了一些挥发性较好的小分子物质.对生物质液化产物的HPLC分析从侧面反映了该液化方法是可行的,生物质在超临界甲醇条件下解聚得较为彻底.     

我国生物质热解液化技术的现状

文章主要阐述了我国生物质热解液化技术的研究现状，包括现有的热裂解液化装置、反应动力学模型、已检测出的不同原料裂解产生的生物油成分及其物理特性分析，提出了生物油精制的必要性和未来需要研究的问题。     

第二代和第三代生物燃料发展现状及启示

第二代生物乙醇以生物质为原料,包括纤维素乙醇和纤维素生物汽油两种产品。目前已建有示范装置和/或工业装置的纤维素乙醇生产技术包括硫酸/酶水解-发酵技术、硫酸水解-发酵技术、酸水解-发酵-酯化-加氢技术、酶水解-发酵技术。业内专家认为,用酶替代硫酸水解是纤维素乙醇生产的发展方向。目前已经和准备进行示范装置试验的纤维素生物汽油生产技术包括快速热解-加氢改质技术和BioForming技术。第二代生物柴油主要以动植物油脂为原料,通过催化加氢生产非脂肪酸甲酯生物柴油,它是理想的优质柴油调合组分。生产第二代生物柴油的加氢技术包括加氢脱氧、回收丙烷和其他轻烃气体、脱水、异构化和裂化、蒸馏等5个步骤,主要有NExBTL可再生柴油生产技术、Ecofining绿色柴油生产技术、Haldor Topsoe可再生柴油生产技术、EERC可再生柴油生产技术。第三代生物燃料有两种:一种是以海藻油为原料生产乙醇、丁醇、喷气燃料和柴油,海藻培养(生长)和萃取海藻油是核心步骤,目前尚处于初期阶段;另一种是以生物质原料通过气化合成生产汽油、喷气燃料和柴油,重点是开发生物质气化技术,降低生产成本。我国应借鉴国外发展第二代和第三代生物燃料的做法,把技术开发工作做深做细做透,搞清楚原料的供应情况;目前我国生物柴油主要采用酯交换法生产脂肪酸甲酯,应考虑开发和采用加氢法生产第二代生物柴油,并努力扩大除麻风果油以外的原料来源;同时应加大海藻生物燃料和生物质气化合成生物燃料的开发力度。     

生物质热加工液化技术评述

介绍了生物质热加工液化技术中的各种热裂解液化和高压液化工艺,包括流化床、涡流烧蚀反应器、真空快速裂解反应器以及高压釜、半连续固定床等装置的工作原理和生产工艺,分析它们各自的优点和存在的问题,着重讨论了各种工艺提高生物原油产率的措施以及精制生物原油可替代柴油作为车用轻质燃油的方法,指出降低生物原油的生产成本,扩大生产规模是热加工液化的发展方向。     

生物质裂解油催化裂解精制机理研究(Ⅲ)——生物质裂解油模拟物的催化裂解机理

分析生物质油6种模拟物在裂解温度500℃,不同质量空速条件下的催化裂解产物。不含芳环的生物质油模拟物(乙酸、甲醇、环戊酮和糠醛)经过HZSM-5分子筛催化剂催化裂解后的产物中,均含有苯、萘、茚和多环芳烃及其衍生物,而苯酚和间甲酚经过HZSM-5分子筛催化裂解后,产物中主要是酚类化合物。根据模拟物催化裂解产物,推测不同类型化合物的催化裂解反应途径,说明生物质裂解油催化裂解精制反应过程主要发生脱氧和芳烃化反应,为生物质油催化裂解精制机理研究提供了理论依据。     

石油炼厂加工纤维素/木质纤维素生物质原料的前景

生物质热解与生物油改质、生物质气化与合成气费-托转化工艺是正在研究开发的第二代生物燃料技术,前者利用快速热解工艺对生物质进行热解或热加氢改质生成热解油;后者用生物质直接合成或先转化为生物油后再生成合成气,合成气经改质和转化生产费-托合成烃。许多石油公司都在以纤维素/木质纤维素为原料,研究开发在石油炼厂内对生物质原料进行后续加工和应用的相关技术。在石油炼厂中引入生物质原料,其挑战是要找到源自非食用生物质或生物质废弃物的原料,而且这些原料应易于运输并易于在炼厂中进行处理,同时应尽可能使用现有的工艺和装置。虽然石油炼厂加工生物质原料尚存在一些问题,但近来开发势头十分强劲。从长远角度来看,任何能为炼厂提供原料,生命周期分析证明能减少CO2排放,并在经济上可行的技术均会在生物燃料开发竞争中成为赢家。     

生物油的分离与分析研究进展

生物质是唯一可转化为液体燃料的、对环境友好的、清洁的可再生资源。通过高压液化或热裂解方法可将生物质制备成类似石油的粘稠状物质——生物油,生物油经过精制可转化为替代石油的常规燃料。生物油的分离与分析具有非常重要的意义,文章综述了生物油的分离与分析技术的研究现状。分离技术包括过滤、萃取、溶解、减压蒸馏：分析技术包括红外光谱、高效液相色谱、气质联用技术、液质联用技术、核磁共振技术等。分析结果表明,生物油含氧量较高,主要含有酸、醛、酮、酚、醚、酯、呋喃等成分。     

Biorefineries: Current activities and future developments

This paper reviews the current refuel valorization facilities as well as the future importance of biorefineries. A biorefinery is a facility that integrates biomass conversion processes and equipment to produce fuels, power, and chemicals from biomass. Biorefineries combine the necessary technologies of the biorenewable raw materials with those of chemical intermediates and final products. Char production by pyrolysis, bio-oil production by pyrolysis, gaseous fuels from biomass, Fischer–Tropsch liquids from biomass, hydrothermal liquefaction of biomass, supercritical liquefaction, and biochemical processes of biomass are studied and concluded in this review. Upgraded bio-oil from biomass pyrolysis can be used in vehicle engines as fuel.     

Liquefaction of palm kernel shell in sub- and supercritical water for bio-oil production

The heavy palm oil industry in Malaysia has generated various oil palm biomass residues. These residues can be converted into liquids (bio-oil) for replacing fossil-based fuels and chemicals. Studies on the conversion of these residues to bio-oil via pyrolysis technology are widely available in the literature. However, thermochemical liquefaction of oil palm biomass for bio-oil production is rarely studied and reported. In this study, palm kernel shell (PKS) was hydrothermally liquefied under subcritical and supercritical conditions to produce bio-oil. Effects of reaction temperature, pressure and biomass-to-water ratio on the characteristics of bio-oil were investigated. The bio-oils were analyzed for their chemical compositions (by GC–MS and FT-IR) and higher heating values (HHV). It was found that phenolic compounds were the main constituents of bio-oils derived from PKS for all reaction conditions investigated. Based on the chemical composition of the bio-oil, a general reaction pathway of hydrothermal liquefaction of PKS was postulated. The HHV of the bio-oils ranged from 10.5 to 16.1 MJ/kg, which were comparable to the findings reported in the literature.     

Hydrothermal liquefaction of biomass: A review of subcritical water technologies

This article reviews the hydrothermal liquefaction of biomass with the aim of describing the current status of the technology. Hydrothermal liquefaction is a medium-temperature, high-pressure thermochemical process, which produces a liquid product, often called bio-oil or bi-crude. During the hydrothermal liquefaction process, the macromolecules of the biomass are first hydrolyzed and/or degraded into smaller molecules. Many of the produced molecules are unstable and reactive and can recombine into larger ones. During this process, a substantial part of the oxygen in the biomass is removed by dehydration or decarboxylation. The chemical properties of bio-oil are highly dependent of the biomass substrate composition. Biomass constitutes of various components such as protein; carbohydrates, lignin and fat, and each of them produce distinct spectra of compounds during hydrothermal liquefaction. In spite of the potential for hydrothermal production of renewable fuels, only a few hydrothermal technologies have so far gone beyond lab- or bench-scale.     

利用微藻热化学液化制备生物油的研究进展

微藻是制备生物质液体燃料的良好材料,利用微藻热化学液化制备生物油在环保和能源供应方向都具有非常重要的意义。目前国内外研究者主要采用快速热解液化和直接液化两种热化学转化技术进行以微藻为原料制备生物油的研究。快速热解生产过程在常压下进行,工艺简单、成本低、反应迅速、燃料油收率高、装置容易大型化,是目前最具开发潜力的生物质液化技术之一。但快速热解需要对原料进行干燥和粉碎等预处理,微藻含水率极高,会消耗大量的能量,使快速热解技术在以微藻为原料制备生物油方面受到限制。直接液化技术反应温度较快速热解低,原料无需烘干和粉碎等高耗能预处理过程,且能产生更优质的生物油,将会是微藻热化学液化制备生物油发展的主流方向,极具工业化前景。国内外研究者还尝试利用超临界液化、共液化、热化学催化液化、微波裂解液化等多种新型液化工艺进行微藻热化学液化制备生物油的实验研究。今后的主要研究方向应是将热化学液化原理研究、生产工艺开发、反应器研发、反应条件优化、产品精制等有机地结合起来,进行深入研究。同时应努力节约成本、降低能耗。     

Utilization of lignin: A sustainable and eco-friendly approach

The use of renewable carbon sources as a substitute for fossil resources is an extensively essential and fascinating research area for addressing the current issues related to climate and future fuel requirements. The utilization of lignocellulosic biomasses as a source for renewable fuel/chemicals/mesoporous biochar derivative is gaining considerable attention due to the neutral carbon cycle. The cellulose and hemicellulose are highly utilized components of biomass, and on the other hand, lignin is a plentiful, under-utilized component of the lignocellulosic biomass in 2G ethanol and paper industry. Significant researchers have contributed towards lignin valorization, with a central goal of the production and upgradation of phenolic, unstable, acidic and oxygen-containing bio-oil to valuable chemicals or fuel grade hydrocarbons. This review is aimed to present the lignin valorization potential from pretreatment of biomass as an initial step to the final process, i.e., lignin bio-oil upgradation with mechanistic pathways. The review offers the source, structure, composition of various lignocellulosic biomasses, followed by a discussion of various pre-treatment techniques for biomass depolymerization. Different thermochemical approaches for bio-oil production from dry and wet biomasses are highlighted with emphasis on pyrolysis and liquefaction. The physical, chemical properties of lignin bio-oil and different upgradation methods for bio-oil as well as its model compounds are thoroughly discussed. It also addresses the related activity, selectivity, stability of numerous catalysts with reaction pathways and kinetics in a broad manner. The challenges and future research opportunities of lignin valorization are discussed in an attempt to place lignin as a feedstock for the generation of valuable chemical and fuel grade hydrocarbons.     

Comprehensive evaluation of hydro-liquefaction characteristics of lignocellulosic subcomponents

This study investigated the hydro-liquefaction behaviors of cellulose, xylan and lignin in ethanol at various temperatures. The interactions between the reaction medium and individual biomass component under different temperatures were evaluated using the Monte Carlo method. The simulation results indicated that the compatibility from cellulose and xylan system was superior to that of lignin with the elevated temperature. The liquefaction characteristics of cellulose and xylan were highly affected by temperature variation due to the existence of active chemical region and functional groups in the structures. In comparison, the reaction behavior of lignin-containing complicated polyaromatic structure was slightly dependent on the elevated temperature. The variation trend of chemical structures from solid residues was highly related to the nature of the raw feedstock. The properties of bio-oil derived from liquefaction of single biomass composition were also associated with the inherent composition of each biomass subcomponent.     

Bio-oil production and upgrading research: A review

Biomass can be utilized to produce bio-oil, a promising alternative energy source for the limited crude oil. There are mainly two processes involved in the conversion of biomass to bio-oil: flash pyrolysis and hydrothermal liquefaction. The cost of bio-oil production from biomass is relatively high based on current technologies, and the main challenges are the low yield and poor bio-oil quality. Considerable research efforts have been made to improve the bio-oil production from biomass. Scientific and technical developments towards improving bio-oil yield and quality to date are reviewed, with an emphasis on bio-oil upgrading research. Furthermore, the article covers some major issues that associated with bio-oil from biomass, which includes bio-oil basics (e.g., characteristics, chemistry), application, environmental and economic assessment. It also points out barriers to achieving improvements in the future.     

Effects of solvents and catalysts in liquefaction of pinewood sawdust for the production of bio-oils

Liquefaction of biomass with proper solvents and catalysts is a promising process to produce liquid biofuels and valuable chemicals. In this study, pinewood sawdust was liquefied in the presence of various supercritical solvents (carbon dioxide, water, acetone, and ethanol) and catalysts (alkali salts and acidic zeolites). The liquid, gas and solid products were analyzed using GC–MS, FT-IR, elemental analyzer, ¹H NMR, ¹³C NMR. The experimental results showed that both solvent and catalyst can significantly improve the liquefaction process by increasing the yield of liquid oil and suppressing the formation of solid residue. K₂CO₃ showed the best performance by doubling the yield of bio oil. Meanwhile, the maximum bio-oil yield (30.8 wt%) and the minimum solid residue yield (28.9 wt%) were obtained when ethanol was employed as the solvent. Solvents can also strongly affect the distribution of liquid products. 2,4,5,7-tetramethyl-phenanthrene and bis(2-ethylhexyl) phthalate were the premier compounds in liquid product as supercritical carbon dioxide is used as solvent while 2-methyl-naphthalene became the main composition when water is used as solvent.     

Comparative study on pyrolysis and catalytic pyrolysis upgrading of biomass model compounds: Thermochemical behaviors,kinetics, and aromatic hydrocarbon formation

In order to understand the pyrolysis mechanism, reaction kinetic and product properties of biomass and select suitable agricultural and forestry residues for the generation desired products, the pyrolysis and catalytic pyrolysis characteristics of three main components (hemicellulose, cellulose, and lignin) of biomass were investigated using a thermogravimetric analyzer (TGA) with a fixed-bed reactor. Fourier transform infrared spectroscopy (FTIR) and elemental analysis were used for further characterization. The results showed that: the thermal stability of hemicellulose was the worst, while that of cellulose was higher with a narrow range of pyrolysis temperatures. Lignin decomposed over a wider range of temperatures and generated a higher char yield. After catalytic pyrolysis over HZSM-5 catalyst, the conversion ratio increased. The ratio for the three components was in the following order: lignincellulose < biomass < xylan. The Starink method was introduced to analyze the thermal reaction kinetics, activation energy (Ea), and the pre-exponential factor (A). The addition of HZSM-5 improved the reactivity and decreased the activation energy in the following order: xylan (30.54%) > biomass(15.41%) > lignin (14.75%) > cellulose (6.73%). The pyrolysis of cellulose gave the highest yield of bio-oil rich in levoglucosan and other anhydrosugars with minimal coke formation. Xylan gave a high gas yield and moderate yield of bio-oil rich in furfural, while lignin gave the highest solid residue and produced the lowest yield of bio-oil that was rich in phenolic compounds. After catalytic pyrolysis, xylan gave the highest yield of monocyclic aromatic hydrocarbons, 76.40%, and showed selectivity for benzene and toluene. Cellulose showed higher selectivity for xylene and naphthalene; however, lignin showed enhanced for selectivity of C10 + polycyclic aromatic hydrocarbons. Thus, catalytic pyrolysis method can effectively improve the properties of bio-oil and bio-char.     

Recent progress in the direct liquefaction of typical biomass

Energy from biomass, bioenergy, is a promising source to replace fossil fuels in the future, as it is abundant, clean, and carbon dioxide neutral. Thermochemical liquefaction of biomass is widely investigated as a promising method to produce one kind of liquid biofuel, namely bio-oil. This review presents the recent research progress in the liquefaction of typical biomass from a new perspective. Particularly, this article summarizes five aspects of related work: first, the effect of solvent type on the liquefaction behaviors of biomass; second, the effect of biomass type on the liquefaction behaviors of biomass; third, the liquefaction of biomass in sub-/super-critical ethanol; fourth, the liquefaction of biomass in organic solvent–water mixed solvents; fifth, the liquefaction of sewage sludge. Meanwhile, the research advance in the migration and transformation behavior of heavy metals during the liquefaction of sewage sludge was also summarized in this review. This review can offer an important reference for the study of biomass liquefaction.