生物质三组分热裂解行为的对比研究

在热天平上对比研究了生物质中的纤维素、半纤维素和木质素三种主要组分的热失重规律。结果表明，作为半纤维素模型化合物的木聚糖热稳定性差，在217℃～390℃发生明显分解；纤维素热裂解起始温度最高，且主要失重发生在较窄温度区域，固体残留物仅为6.5%；木质素表现出较宽的失重温度区域，最终固体残留物高达42%。在红外辐射机理试验台上对比研究了三组分热裂解产物随温度的变化规律。三组分热裂解生物油产量随温度变化先升后降。纤维素生物油产量在峰值上最高，但纤维素生物油热稳定性差，高温时挥发分的二次分解最明显；木聚糖和木质素生物油产量较低，表现出较好的热稳定性。三组分热裂解焦炭产量随温度升高而降低，最终纤维素热裂解焦炭产量为1.5%，而木聚糖和木质素分别为22%和26%。三组分热裂解气体产物随温度升高而增长，但在气体组成分布上因三组分的结构上的差异而不同。     

木质素热解生物油组成成分与分子尺寸分布特性分析

选用脱碱木质素作为原料,以热裂解气质联用技术(Py-GC/MS)研究木质素在350～600℃下热解产物成分和含量,并利用Joback法、 Lijie法和Tahami法3种基团贡献法计算了生物油各组成成分的临界参数和动力学直径,对木质素热解油产物的分子动力学直径分布特性进行计算.结果显示,愈创木基结构、紫丁香基结构、苯酚类、邻苯二酚类和芳烃类等5种芳香族化合物是350～600℃下木质素热解生物油的主要组成成分,其中愈创木基结构化合物的平均峰面积百分比达到70.7%.随着反应温度从350提高到600℃,分子动力学直径在0.560～0.610 nm区间内的木质素热解油组分含量从14.6%增加至31.3%.木质素热解生物油主要产物的动力学直径在0.560～0.710nm,表明一些孔径尺寸在此范围内的分子筛如SSZ-20、 ZSM-5和Beta可作为木质素裂解制备高品质芳烃燃料的催化剂.     

β-1型木质素二聚体高温蒸汽气化机理的理论研究

以β-1型木质素二聚体为研究对象,采用以密度泛函理论B3LYP/6-31G(d,p)为基础的Gaussian工具包对该木质素二聚体的高温纯蒸汽气化反应过程进行了分子动力学模拟研究。结果表明,在木质素二聚体高温蒸汽气化的初反应中,R4和R5的反应焓变较小分别为243.9和323.2 kJ/mol,Cα-Cβ键和Cβ-C1键较易断裂。通过计算次反应路径的势垒,发现R4-1和R5-1反应的势垒较小分别为4.4和24.0 kJ/mol,因此,在该气化过程中会优先选择R4-1和R5-1路径。该反应路径最后得到的产物有甲醇、乙醇、苯酚、对羟基甲苯和对羟基苯甲醛,与实验产物吻合。     

CaO伴随生物质热裂解制油同时脱氧的小型流化床实验研究

在小型流化床反应器中,对CaO伴随生物质快速热裂解制油过程中的直接脱氧效果进行了研究。当反应温度为520℃、载气流量8000L/h时,在纯白松粉末和CaO伴随条件下分别制出了生物油样品。实验结果表明,当采用纯白松与CaO/白松质量比分别为1、2、4时,生物油样品中有机组分的含氧量依次为39.38%、39.15%、39.04%和32.29%;在CaO/白松质量比为4时,生物油有机组分含氧量的下降幅度达18.0%（相对变化）。GC-MS分析结果表明,CaO加入后左旋葡聚糖和甲酸、乙酸等高含氧量物质相对含量明显下降,证实了CaO伴随生物质热裂解过程中“富氧中间体”固氧路径的存在;与此同时,糠醛类等主要来源于脱水反应的产物相对含量上升,说明CaO的加入也促进了脱水反应的发生。     

生物油中酚类化合物加氢脱氧催化剂研究进展

随着化石能源日益匮乏,生物质热裂解制备生物油广受关注.然而,生物油中含有大量酚、呋喃、醛、酮等含氧化合物,含氧量高达50%,导致其热值低、化学稳定性差等,因而阻碍了它的广泛应用,必须对其进行加氢脱氧精制降低含氧量.在生物油中众多含氧化合物中,酚羟基氧被认为是最难被脱除的.对酚类含氧化合物加氢脱氧催化剂及反应进行了简单综述,并提出了如何进一步提高催化剂性能的有效方法.     

生物质热化学转化制备生物燃料及化学品

生物质是环境友好的可再生能源.近年来相关研究不断升温,文献报道量激增.本文在现有文献综述及近期报道的基础上,从利用热化学方法由生物质获得燃料油及化学品的角度对各方案进行了归纳、适当补充及简要述评,重点介绍了生物油催化裂解精制、水相重整制备烷烃、超临界水/水热制备化学品3个领域.     

生物质热化学转化制备生物燃料及化学品

生物质是环境友好的可再生能源.近年来相关研究不断升温,文献报道量激增.本文在现有文献综述及近期报道的基础上,从利用热化学方法由生物质获得燃料油及化学品的角度对各方案进行了归纳、适当补充及简要述评,重点介绍了生物油催化裂解精制、水相重整制备烷烃、超临界水/水热制备化学品3个领域.     

木质素催化转化制取苯、甲苯和二甲苯

对HZSM-5、HY和MCM-22三种催化剂进行了比较,其中HZSM-5催化裂解木质素制备苯、甲苯和二甲苯（BTX）的结果最优．确定了木质素催化裂解的最佳反应条件,包括反应温度、载气流速、催化剂／木质素配比．当反应温度为550-600℃,载气流速为300mL／min,催化剂／木质素配比为2时,使用HZSM-5催化裂解制备BTX的最高C产率和芳香选择性分别可达25．3％和90．9％。     

生物质焦制备条件对其燃烧反应特性的影响

在热重分析仪上,研究了生物质焦的制备条件对其燃烧反应特性的影响。生物质焦由闪速裂解技术制得,裂解温度为 748 K、773 K和823 K;原料含水质量分数为0、7.0%和11.3%。研究发现,生物质焦中挥发性物质的质量分数和H/C质量比随裂解温度的增加而降低,其燃烧反应性随裂解温度的增加而降低;与高裂解温度条件下制得的生物质焦相比,低裂解温度条件下制得的生物质焦具有较高的反应活化能和对燃烧温度更敏感。原料含水量对生物质焦的燃烧反应特性影响很小;但对高裂解温度条件下制得的生物质焦中的挥发性组分含量有较大的影响。简化的生物质焦本征燃烧反应幂函数动力学模型可以很好地描述其燃烧行为。     

木质素活化改性制备酚醛树脂胶黏剂研究进展

木质素由于化学结构与苯酚相似,通过活化改性可部分替代苯酚制备木质素改性酚醛树脂胶黏剂。既可降低成本、达到生物质资源高效利用的目的,并且制备的木质素改性酚醛树脂胶黏剂有毒残余较低,具有环保意义,是合成制备生物质高分子材料的重要途径。本文综述了国内外研究人员在木质素活化改性制备酚醛树脂胶黏剂研究领域的最新进展,重点介绍了化学改性、物理改性、生物改性等木质素活化改性方法,比较了不同改性产物制备酚醛树脂胶黏剂的性能,并对影响木质素活化改性制备酚醛树脂胶黏剂实现工业化应用的主要因素进行了分析。     

Fast pyrolysis of biomass

The development of viable fast pyrolysis processes for biomass and other carbonaceous feedstocks will offer significant advantages over conventional pyrolysis, flash pyrolysis and gasification processes with respect to product yield quality and flexibility. Fast pyrolysis is defined and related to other biomass thermochemical conversion processes in some detail. Brief references are made to corresponding coal, hydrocarbon and oil conversion research and development. Proposed mechanisms and chemical pathways are reviewed, potential products. product upgrading and product applications are identified. Fast pyrolysis research is reviewed on both the fundamental bench-scale level and the applied process development level.     

High temperature pyrolysis of novolac resin biomass composites

Composites of novolac resin (N.R.) and biomass derived from olive stones (OL.B.), in various proportions, were cured with hexamethylenetetramine (HTA) and pyrolyzed up to 900°C. The pyrolysis mechanism was monitored using TGA and gas chromatography. The pyrolysis regions, as well as important pyrolysis parameters of the materials used, were determined. Cured and pyrolyzed composites of N.R./OL.B. varied from 20/80 to 75/25, exhibiting at temperatures up to approx. 600°C lower weight losses than expected by the rule of mixtures, owing to additional cross linkages of lignin with HTA. This stabilization effect vanished during pyrolysis at higher temperatures because of the breaking of other chemical bonds, e.g. cross linkages. The release of CH₄ during the pyrolysis of OL.B. is derived from the lignin contained in OL.B. The other gases, CO, CO₂ and H₂, could be formed from celluose, hemicellulose and lignin which are the main components of OL.B. The use of N.R. in the initial mixture with OL.B. reduces the weight losses during pyrolysis compared with OL.B. alone. A heating rate of 10°C/min was necessary for the carbonization processes of OL.B. and its mixtures with N.R. in order to promote minimum weight loss of material and minimum pyrolysis time.     

生物质废弃物的热解研究

生物质能是可再生能源,在生长过程中通过光合作用将碳和能量固定下来,利用生物质能CO2排放很少.为实现可持续能源生产和减少温室气体排放的目的,中国已于2006年1月开始实施《中华人民共和国可再生能源法》.     

热解压力对生物质焦结构及气化反应性能的影响

利用加压固定床反应器、吸附仪、X射线衍射仪、元素分析仪、电感耦合等离子原子发射光谱仪等考察了热解压力对生物质半焦(以下简称半焦)产率、物化结构、元素组成的影响规律。同时,利用热天平对不同热解压力下所制半焦的气化行为进行了考察。结果表明,随热解压力升高,半焦产率增大,当压力升至1.0 MPa后,半焦产率基本不变;半焦中C元素含量随热解压力的升高而增加,而H元素含量和BET比表面积则减小;此外,随热解压力升高,玉米秸秆焦和锯末焦的石墨化程度增强,而稻壳焦的石墨化程度则基本不受热解压力影响。气化反应的研究表明,玉米秸秆焦及锯末焦的平均气化反应速率随热解压力的提高而减小,而稻壳焦的平均气化反应速率基本不受热解压力的影响。热解压力对半焦BET比表面积及碳微晶结构的影响规律与气化反应速率变化规律的对比研究表明,热解压力引起半焦微晶结构的变化是造成热解压力对半焦气化反应速率影响的主要原因。     

基于裂解气质联用分析的生物质逐级热解研究

为探究生物质快速热解反应历程,利用裂解气质联用仪对生物质进行逐级热解实验,考察在不同温度区间热解液体产物组分的分布规律。实验结果表明,生物质的化学组成和热解温度区间对热解液体产物都有重要影响。桉木在25℃~400℃热解液体产物较少,主要是吡喃和芳香类化合物,其中5,6-二氢-4-羟基-吡喃-2-酮相对峰面积随温度升高而降低;在450℃~500℃热解液体产物种类和产量均较多,主要以酮类和芳香类化合物为主。玉米芯热解规律和桉木的相似,但在25℃~350℃主要以呋喃类化合物为主,主要热解液体产物是2,3-二氢-苯并呋喃和2-甲氧基-4-乙烯基苯酚,在400℃~450℃热解液体产物以酮类化合物为主。生物质主要化学组分在不同温度区间热解得到不同液体产物,对其进行选择性热解,能够有效实现生物质资源的综合利用。     

Kinetic study of wood chips decomposition by TGA

Pyrolysis of a wood chips mixture and main wood compounds such as hemicellulose, cellulose and lignin was investigated by thermogravimetry. The investigation was carried out in inert nitrogen atmosphere with temperatures ranging from 20°C to 900°C for four heating rates: 2 K min⁻¹, 5 K min⁻¹, 10 K min⁻¹, and 15 K min⁻¹. Hemicellulose, cellulose, and lignin were used as the main compounds of biomass. TGA and DTG temperature dependencies were evaluated. Decomposition processes proceed in three main stages: water evaporation, and active and passive pyrolysis. The decomposition of hemicellulose and cellulose takes place in the temperature range of 200–380°C and 250–380°C, while lignin decomposition seems to be ranging from 180°C up to 900°C. The isoconversional method was used to determine kinetic parameters such as activation energy and pre-exponential factor mainly in the stage of active pyrolysis and partially in the passive stage. It was found that, at the end of the decomposition process, the value of activation energy decreases. Reaction order does not have a significant influence on the process because of the high value of the pre-exponential factor. Obtained kinetic parameters were used to calculate simulated decompositions at different heating rates. Experimental data compared with the simulation ones were in good accordance at all heating rates. From the pyrolysis of hemicellulose, cellulose, and lignin it is clear that the decomposition process of wood is dependent on the composition and concentration of the main compounds.     

Inorganics distribution in bio oils and char produced by biomass fast pyrolysis: The key role of aerosols

Fast pyrolysis of biomass is a promising process for the preparation of bio-oil dedicated to energy production. Inorganic species originally present in biomass are known to induce problems such as bio-oil instability or deposits and fouling. However the mechanisms of inorganic species release during biomass pyrolysis into the raw bio-oils still remain unclear. The present work focuses on the determination of inorganic distribution in the products from wheat straw and beech wood fast pyrolysis performed in a fluidized bed. More specifically, the bio-oils are fractionated by using a series of condensers. The results show that more than 60 wt.% of the inorganic content of the overall bio-oil is contained in the aerosols. Several possible interpretations for this observation are discussed. It is likely that the inorganics are transported within the aerosols droplets and solid particles which are recovered in the bio-oils, either by mechano-chemical processes, or by entrainment of submicron intermediate liquid compound formed in the first steps of biomass fast pyrolysis.     

钾元素对生物质主要组分热解特性的影响

采用热重-红外联用仪对松木及生物质主要化学组分半纤维素、纤维素、木质素的热解特性及钾元素对其热解特性的影响进行了研究.结果表明,半纤维素、纤维素、木质素发生热解的主要温度分别为200~350 ℃、300~365 ℃和200~600 ℃;半纤维热解产物中CO、CO₂较多;纤维素热解产物中LG和醛酮类化合物最多;木质素热解主要形成固体产物,气体中CH₄相对含量较高.三种组分共热解过程中发生相互作用使热解温度提高、固体产物增加,气体中CO增加而CH₄减少.添加K₂CO₃后半纤维素和纤维素热解温度区间向低温方向移动,固体产率提高.K对纤维素作用最明显,CO、CO₂气体与固体产物产率明显增加,醛酮类和酸类物质的产率降低;木质素受K影响相对较小,热解固体产物略有增加,挥发分中H₂O和羰基物质增加;三组分共热解减弱了钾元素的催化作用.     

Investigation of physicochemical properties of biooils produced from yellow poplar wood (Liriodendron tulipifera) at various temperatures and residence times

Fast pyrolysis of yellow poplar wood (Liriodendron tulipifera) was performed under different temperature ranges and residence times in a fluidized bed reactor to maximize the yield of biooil. In this study, the pyrolysis temperature ranged from 400 °C to 550 °C, and the residence time of pyrolysis products was controlled between 1.2 and 7.7 s by inert nitrogen gas flow. The results revealed that the distribution of thermal degradation products (biooil, biochar, and gas) from the woody biomass was heavily influenced by pyrolysis temperature, as well as residence time. The highest yield of biooil was approximately 68.5 wt% (wet basis), with pyrolysis conditions of 500 °C and 1.9 s of residence time. Water content of the biooils produced at different temperatures was 25-30 wt%, and their higher heating values were estimated to be between 15 MJ/kg and 17 MJ/kg. Using GC/MS analysis, 30 chemical components were identified from the biooil, which were classified into 5 main groups: organic acids, aldehydes, ketones, alcohols, and phenols. In addition, biochar was produced as a co-product of fast pyrolysis of woody biomass, approximately 10 wt%, at temperatures between 450 °C and 550 °C. The physicochemical features of the biochar, including elemental analysis, higher heating values, and morphological properties by SEM, were also determined.     

碱／碱土金属催化松木屑快速热解机制

研究碱／碱土金属（AAEM）对生物质的热解及其热解产物组成的影响规律,可为生物质热解特性研究和热解产物的高效利用提供重要的理论依据。本文以松木屑为原料,将原样进行酸洗,并对酸洗样分别用K、Ca、Na和Mg氯化盐溶液浸渍,在500℃和Ar气氛下对各样品进行快速热解,考察了4种金属离子对松木屑热解产物组成分布的影响规律;通过热重分析考察了各个样品的热解特性;通过对热解生物油的气相色谱／质谱（GC／MS）分析考察了快速热解的焦油成分。研究结果表明：AAEM对松木屑有明显的催化作用,AAEM的存在能够提高热解气体和固体的产率,降低热解焦油的产率;AAEM能够降低热解温度,使热解更加容易进行;快速热解的焦油成分主要有酚类、酮类、醛类、芳烃、醇类、脱水糖类、呋喃类以及酸类,AAEM显著影响焦油产物组成,特别是呋喃类和芳烃的含量会有所增加。本文为优化生物质的热解条件与提高热解生物油品质具有重要意义。