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。     

生物质热解液化技术研究与发展趋势

介绍了生物质热解液化技术,总结了该项技术在原料预处理、热解工艺和生物油分离精制3个方面的最新研究成果。在原料预处理方面,介绍了微波干燥、烘焙和酸洗3种方法;在热解工艺方面,介绍了催化热解和混合热解两种新工艺;在生物油分离精制方面,介绍了催化加氢、催化裂解、催化酯化、乳化燃油和分离提纯5种新技术,并分析展望了生物质热解液化技术的产业化发展趋势。     

生物质闪速热裂解制备生物质油

生物质闪速裂解是使生物质的有机高聚物在隔绝空气、常压、快速加热到400～600℃（约104 K/s的升温速率）,超短反应时间（小于2 s）的条件下迅速断链分子键,使结炭和产气降到最小限度,从而最大限度地获得生物质油.依据这一原理,出现了涡旋反应器、烧蚀裂解、旋转锥、沸腾流化床、循环流化床等工艺.文中系统地阐述了常用的生物质闪速裂解液化的方式,介绍了生物质裂解油的特点.     

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。     

基于欧拉-欧拉多相流模型对生物质快速热裂解的数值模拟

基于欧拉-欧拉多相流方法,采用单步多元反应动力学模型研究了生物质在二维鼓泡流化床反应器中的快速热裂解反应,分析了反应器中颗粒流动、传热以及热裂解产物组成的分布规律。结果表明:气泡的流动有助于气体、石英砂和生物质的混合和热量交换;经过气体的对流换热和石英砂的接触导热,生物质温度迅速升高后发生热裂解,热裂解温度为750～850 K;计算得到的生物油、焦炭和不可冷凝气体的产率分别为59.2%、14.4%和22.1%。     

基于电磁感应的新型热解液化反应器可行性研究

将电磁感应加热技术与热裂解技术有机地结合在一起,研制出一种新型的热解液化反应器,在该反应器上既可以实现油页岩的干馏又可以实现生物质快速热解液化.利用电磁感应原理加热兼输料于一体的螺旋输料轴,不需要气体和固体热载体,降低了系统的运行能耗,避免了可燃气体的稀释,减少反应器的磨损.通过对桦甸油页岩进行实验研究,说明了该反应器的可行性.为今后油页岩和生物质的快速热解制取石油替代品奠定了基础.     

生物质热裂解技术的实验研究

以木屑为原料,利用从荷兰引进的旋转锥反应器闪速热裂解装置进行了热裂解试验。对热裂解产物的组成及反应的物质平衡进行了分析。结果表明：木屑热裂解产物由生物油、不可冷凝气体和木炭组成。其中,生物油成分复杂,低热值为１６ ５９５ｋＪ／ｋｇ;不可冷凝气体主要由ＣＯ,ＣＨ４ ,ＣＯ２ ,Ｈ２ 和Ｈ２Ｏ蒸汽组成。在反应器温度为６００℃,旋风机温度为５００ ℃,旋转锥频率为１０Ｈｚ 条件下,当木屑喂入率为２６．４２ｋｇ／ｈ 时,生物油、不可冷凝气体及木炭的得率分别为５３．３７％ ,２１ ．４５％ 和２５．１６％ 。     

污泥催化水热液化制备生物油的研究进展

水热液化是“双碳”背景下实现废弃生物质资源化、能源化利用的有效途径,特别是针对含水率高的污泥,可将其直接转化为生物油。然而水热液化转化效率和生物油中化合物的形成取决于水热液化工艺的各种参数,其中合适的催化剂在水热液化反应中具有非常重要的作用。均相催化剂中的碱催化剂主要作用于碳水化合物、木质素以及脂质等物质的液化反应,能够有效降低生物油中的氧含量,并能将生物油产率提高到48%左右。而酸催化剂可以促进蛋白质的水解以及脱氨反应,将生物油中的氮元素转移到水相中,从而降低生物油中的氮元素含量,提高生物油品质。非均相催化剂则促进了脱羧反应及美拉德反应,尤其是金属负载型催化剂,双金属的协同作用及过渡金属的加氢作用,将生物油产率最高提高至53.12%(Ni/Mo催化剂)。今后对各类催化剂的具体作用机理仍需进一步明确,以期开发出高性能、稳定性好、高选择性且成本适宜的催化剂,在提高生物油产率的同时改善生物油品质。     

旋转锥式反应器催化大豆油裂解制备可再生燃料油

采用自制的转锥式催化裂解反应器,研究了以大豆油为原料制备可再生液体燃料油的技术.考察了催化剂的种类、裂解温度、加料速度等反应工艺条件对裂解产物性能的影响.研究结果表明:催化裂解反应的优选工艺条件为氢氧化钾作为催化剂,反应温度为450-500℃,滴加速度为50g/h,液体燃料收率为78.3%.气质联用和红外光谱分析表明,...     

厨余垃圾水热液化成油特性研究

以中国农业大学5个学生食堂厨余垃圾按照日产量比例混配后作为原料(含固量,22.54%),研究反应温度(260、290和320℃)对水热液化反应和产物分布的影响。最大液化率和最大产油率分别为79.25%(290℃)和42.02%(260℃),生物原油热值最高可达37.39 MJ/kg,能量回收率最高可达65.96%。GC-MS分析表明生物原油由烃类、酸类、醇类、酮类和醛类等物质组成。     

微藻热化学催化液化及生物油特性研究

以杜氏盐藻为原料,乙二醇为液化介质、浓硫酸为催化剂进行热化学液化反应.运用中心组合设计及响应面分析(RSA),在单因素试验的基础上建立了预测杜氏盐藻液化产率的数学模型.回归分析表明,液化温度、停留时间与催化剂用量及其交互作用对液化都有显著影响.以液化产率为响应值作响应面和等高线图,揭示了各参数交互关系.通过响应面优化,求得最佳工艺条件为:催化剂用量2.4%,液化温度170℃,停留时间33min,在此条件下液化率达到97.05%.基于生物油广泛应用的目的,对产物生物油的物理化学性质进行了研究,并结合FT-IR、~(13)C-NMR、GC-MS等技术对生物油的主要组分分布进行了分析.结果表明:生物油的主要成分为苯并呋喃酮30.43%、C14～C18有机酸甲酯23.25%和C14～C18有机酸羟乙基酯27.89%.生物油由于高的含氧量,需要进一步改性才能高端应用.     

生物质高压液化制生物油研究进展

以生物质为原料进行高压液化制备生物油是目前生物质能领域研究的一个热点。纤维素在水中的降解是复杂的竞争和连串反应机理;在180℃以上,半纤维素就很容易水解,而且不管是酸还是碱都能催化半纤维素的水解反应;在水热条件下木质素会发生分解,生成多种苯酚、甲氧基苯酚等,这些产物可进一步被水解成甲氧基化合物。影响生物质液化产率及生物油组成的主要因素是温度、生物质类型和溶剂种类;次要因素包括停留时间、催化剂、还原性气体和供氢溶剂、加热速率、生物质颗粒大小、反应压力等。纤维素类生物质通过高压液化可以生产生物油,生物油经物理精制及化学加工可以制取车用燃料、生物气及化工产品等。生物油有轻油和重油之分,都是通过对生物质液化产物的分离精制而得到的。目前用来分析生物油的主要方法包括GC-MS(色-质联用)、EA(元素分析)、FTIR(傅里叶变换红外光谱)、HPLC(高效液相色谱)、NMR(核磁共振)、TOC(总有机碳测定)等。人们对生物质高压液化研究已经进行多年,并建立了几套工业试验示范装置。不过因为操作条件太苛刻,到目前为止还没有建立商业化装置。     

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.     

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.     

Hydrothermal catalytic liquefaction mechanisms of agal biomass to bio-oil

The liquefaction mechanisms of the algal biomass to bio-oil were investigated by using Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy, respectively. It was found that NaOH was a satisfactory catalyst and contributed to helping the liquefaction of algal biomass. The bio-oil from algal biomass was composed of many compounds, including carbohydrates, alcohol, hydroxybenzene, carboxylic acid, alkene, ester, and others. The mechanism of hydrothermal catalytic liquefaction was discussed. It was found that, comparing with the husk bio-fuel, the algal bio-oil as a promising alternative fuel was more close to the traditional diesel fuel in physicochemical properties. The novel research outcomes contribute to improving the yield of bio-oil from microalgae, reducing the cost of the bio-oil and accelerating the commercial application of the algal bio-oil in the near future.     

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 macroalgae: Influence of zeolites based catalyst on products

Hydrothermal liquefaction (HTL) of Ulva prolifera macroalgae (UP) was carried out in the presence of three zeolites based catalysts (ZSM-5, Y-Zeolite and Mordenite) with the different weight percentage (10–20 wt%) at 260–300 °C for 15–45 min. A comparison between non-catalytic and catalytic behavior of ZSM-5, Y-Zeolite, and Mordenite in the conversion of Ulva prolifera showed that is affected by properties of zeolites. Maximum bio-oil yield for non-catalytic liquefaction was 16.6 wt% at 280 °C for 15 min. The bio-oil yield increased to 29.3 wt% with ZSM-5 catalyst (15.0 wt%) at 280 °C. The chemical components and functional groups present in the bio-oils are identified by GC-MS, FT-IR, ¹H-NMR, and elemental analysis techniques. Higher heating value (HHV) of bio-oil (32.2–34.8 MJ/kg) obtained when catalyst was used compared to the non-catalytic reaction (21.2 MJ/kg). The higher de-oxygenation occurred in the case of ZSM-5 catalytic liquefaction reaction compared to the other catalyst such as Y-zeolite and mordenite. The maximum percentage of the aromatic proton was observed in bio-oil of ZSM-5 (29.7%) catalyzed reaction and minimum (1.4%) was observed in the non-catalyst reaction bio-oil. The use of zeolites catalyst during the liquefaction, the oxygen content in the bio-oil reduced to 17.7%. Aqueous phase analysis exposed that presence of valuables nutrients.     

Comparison of pyrolysis and hydrothermal liquefaction of Chlamydomonas reinhardtii. Growth studies on the recovered hydrothermal aqueous phase

The production of bio-oil by pyrolysis with a high heating rate (500 K s⁻¹) and hydrothermal liquefaction (HTL) of Chlamydomonas reinhardtii was compared. HTL led to bio-oil yield decreasing from 67% mass fraction at 220 °C to 59% mass fraction at 310 °C whereas the bio-oil yield increased from 53% mass fraction at 400 °C to 60% mass fraction at 550 °C for pyrolysis. Energy ratios (energy produced in the form of bio-oil divided by the energy content of the initial microalgae) between 66% at 220 °C and 90% at 310 °C in HTL were obtained whereas it was in the range 73–83% at 400–550 °C for pyrolysis. The Higher Heating Value of the HTL bio-oil was increasing with the temperature while it was constant for pyrolysis. Microalgae cultivation in aqueous phase produced by HTL was also investigated and showed promising results.     

Bio-oil fractionation by temperature-swing extraction: Principle and application

Bio-oils produced by direct thermal liquefaction often contain heavy components that hinder their utilization as a liquefaction medium. This paper reports a new approach to fractionate the liquefaction bio-oil into a light and a heavy fraction based on solvent extraction and temperature-swing regeneration. This approach is based on hot extraction (T ∼ 70 °C) of the light fraction of the oil with a suitable extraction solvent followed by cold (T ∼ 25 °C) de-mixing of the light fraction and the extraction solvent. In this paper, we (i) illustrate the selection of the extraction solvent and define the solvent properties required, (ii) demonstrate the potential of multistage extraction/regeneration for the bio-oil produced by direct thermal liquefaction, (iii) extend the concept to fractionate a petroleum crude oil, (iv) discuss the theoretical basis of the fractionation using polymer solution theory and, finally, (v) show a low energy requirement of the extraction process by means of process simulation, i.e., an equivalent of ∼1% of the biomass intake.