聚醚醚酮改性酚醛树脂热解动力学研究

利用热失重分析仪对聚醚醚酮（PEEK）改性酚醛树脂（PF）的热解过程进行分析,并根据热失重曲线的特点,把树脂的热解过程分为3个阶段。结果表明,随着升温速率的增大,PEEK改性PF出现延迟分解的现象。根据Kissinger法、Ozawa法和Crane法建立了热解动力学模型,得出热解的活化能为561 kJ/mol,指前因子为1.06×1035 s-1,反应级数为0.9648(近似于1级反应)。     

果壳生物质热解特性与动力学

采用热重分析仪对林产果壳生物质（澳洲坚果壳、油茶壳、核桃壳）热解特性进行了研究,利用分布活化能模型（DAEM）分析了热解动力学。热解特性研究表明：油茶壳最大失重速率最小,热解起始温度、结束温度、最大失重速率温度均低于澳洲坚果壳和核桃壳;澳洲坚果壳和核桃壳热解特征值近似;3种果壳生物质随升温速率的增加,热解过程向高温区转移。DAEM研究表明：DAEM适用于3种果壳生物质的热解动力学研究,相关系数R²在0.914~0.999之间;澳洲坚果壳热解活化能83.91~211.86 kJ/mol,油茶壳热解活化能68.64~244.49 kJ/mol,核桃壳热解活化能98.69~267.75 kJ/mol;随转化率的增加,3种果壳生物质活化能呈现相同的变化趋势,但变化幅度不同。     

生物质玉米芯热解机理研究

利用热重分析方法对生物质玉米芯在不同条件下热解行为进行了详细研究 ,得出了影响热解过程的因素及热解动力学参数 (如表观活化能、反应级数及指前因子等 ) .结果表明 ,所选保护气的种类对热解过程基本上不产生影响 ;同在较低的气体流速下进行热解相比较 ,在较高的流速下进行热解 ,发生分解反应需要较高的起始分解温度、最大分解速率的温度及较高的反应活化能 ,反应级数也大 ;随着加热速率的增大 ,发生分解反应的最大分解速率的温度向高温处移动 ,但反应的活化能降低 ,反应级数减小 .在实际的热解过程中 ,采用快速加热、低流速的惰性保护气进行热解 ,有利于利用热解过程的各种产物 .     

城市粪便热解特性与动力学

随着国家相关标准的细化和执行,城市粪便（收集自化粪池及旱厕）的无害化处理正受到越来越多关注。本文利用热重-微商热重分析（TG-DTG）对我国北方典型城市粪便热解特性进行了研究,并与3种常见动物粪便（猪粪、牛粪、鸡粪）的热解行为进行了对比。城市粪便的热解过程温度主要集中在205～525℃。城市粪便的最大失重温度与其余三种动物粪便较为接近,但热解结束温度高于其他三种样品。利用试验所得数据,采用Coats-Redfern法处理并计算不同生物质在相应热解条件下的反应动力学参数,结果显示城市粪便热解适合采用一级双组分分阶段反应模型。与动物粪便相比,城市粪便热解所需活化能低于牛粪,但高于鸡粪和猪粪。     

烟杆废物热解动力学研究

通过热重分析（TGA）方法,采用单步和三平行反应模型分别考察烟杆废物的热解动力学。烟杆废物单步热解的平均活化能为182.4 kJ/mol,最适宜的反应机理函数为14级反应机理f（α）=（1-α）¹⁴。能量补偿效应结果显示烟杆废物的热解可以分为3个阶段α=0~0.32、α=0.32~0.80和α=0.80~1,各阶段的指前因子分别为2.88×10¹⁰、4.33×10¹⁴和9.76×10¹⁶s^-1。单步热解过程中伴有表观活化能的变化以及高级数反应的机理,不能合理地描述烟杆废物的热解机理。采用混合韦伯分布活化能模型考察了三平行反应热解动力学,结果显示：混合韦伯分布活化能模型能很好地拟合烟杆废物热解数据,相关系数R²≥0.997 6;3种伪组分的活化能大小符合E₀（木质素,195.26 kJ/mol）> E₀（纤维素,152.54 kJ/mol）> E₀（半纤维素,121.18 kJ/mol）的顺序;半纤维素的热解机理为一级反应f（α）=1-α,纤维素的热解机理属于成核机理,木质素的机理亦呈现级数反应,级数介于n=3~4之间,木质素的热解机理复杂,可能为多步反应。     

白炭黑胎面胶热解动力学研究

在不涉及动力学模型假设的条件下,通过整合多动力学研究方法完成白炭黑胎面胶复杂热解过程的动力学分析,得到热解动力学反应机制并准确得出热解动力学三因子（机理函数、活化能和指前因子）。结果表明：白炭黑胎面胶的热解过程可分为子反应Ⅰ和Ⅱ两个阶段,子反应Ⅰ的机理函数为f（α）＝0.247 3α-3.043 7,活化能为155.26 kJ·mol-1,指前因子为1.288×1012 min-1;子反应Ⅱ的机理函数为f（α）＝0.414 2（1－α）[－ln（1－α）]-1.414 3,活化能为315.40 kJ·mol-1,指前因子为3.099×1024 min-1。     

生物质与煤共燃研究(Ⅰ)生物质的低温热解

介绍了生物质与煤共燃的研究流程及其主要的研究方法，通过对三种主要农业剩余生物质（锯屑，谷壳和花生壳）热解过程中的失重率变化，物理性质变化，工业分析变化，元素分析变化和发热量变化的研究发现，三种生物质在热解温度220℃-300℃，热解时间30min-60min下进行低温热解时，热解过程主要受热解温度控制，受热解时间控制较弱，随热解温度升高，热解时间延长，生物质的热失重率逐渐升高，生物质逐渐变得易于研磨。在工业分析上挥发分逐渐减少，固定碳及灰分不断提高，水分含量大幅下降；在元素分析上O元素的含量不断下降，C元素的含量不断上升，从而发热量不断增加，研究表明，当热解温度为270℃-300℃时，热解生物质的各项性质可与煤接近。     

KOH作用下甲壳素的热解特性和动力学研究

采用热重分析法研究了经KOH浸渍的甲壳素的热解特性,并考察了不同浸渍比对热解过程的影响;同时采用Coats-Redfern积分法拟合计算出热解动力学参数,探究了KOH对甲壳素主要热解过程中活化能的影响。热重分析结果表明：KOH的加入改变了甲壳素的热解行为,降低了热解所需的活化能,加快了反应速率,促进了甲壳素热解;当浸渍比即m（65% KOH）∶m（甲壳素）=2∶1或3∶1时,KOH浸渍后能使甲壳素在140℃左右开始迅速热解。热解动力学参数计算结果表明：无论反应级数选择多大,其线性拟合效果均比较好,相关系数基本都高于0.95;KOH作用下甲壳素热解是一个复杂的化学反应,而不是单一的某一级反应。     

接枝氯丁橡胶热分解动力学研究

研究了甲基丙烯酸甲酯（MMA）与氯丁橡胶（CR）接枝共聚物（CR—g—PMMA）热分解动力学，结果表明，CR的热分解过程分三步进行，N2气氛下的明显起始分解温度为210℃，推算出各步热分解反应级数、活化能和频率因子。     

生物质与煤共热解气化行为特性及动力学研究（摘要）

在现有实验室条件下,全面分析了6种形式的生物质与煤共热解过程,考察其中的协同反应效应,利用分布活化能法（DAEM）研究生物质与煤的共热解动力学特性,得出共热解动力学相关参数,为实现生物质与煤高效协同共热解反应寻找更为有效的途径。主要内容和研究成果归纳如下：     

Kinetic study of Chinese biomass slow pyrolysis: Comparison of different kinetic models

The slow pyrolysis of six Chinese biomasses was studied by thermogravimetric experiments. Non-linear square fitting method is used to calculate DTG data. The analysis results show that it is not possible to exactly represent the biomass pyrolysis by a one-step model with different mechanisms. Thus, three-pseudocomponent models were used to simulate the biomass pyrolysis. It was found that the three-pseudocomponent model with n-order kinetics (model II) is more accurate than the model with first-order kinetics (model I). Activation energies of three-pseudocomponents in model II are bigger than the values in model I. It is shown that model II yields the best simulation results, especially with respect to describe accurately the pyrolysis of the first pseudocomponent (hemicellulose) and the last one (lignin). Nevertheless, with regard to a practical utilization, the three-pseudocomponent model with a reaction order of one could be used, because the accuracy to represent biomass pyrolysis is high enough. Unrealistic high values of the reaction order are avoided, and thus this model is more realistic with respect to the chemical interpretation of the reaction order.     

Revealing low temperature microwave‐assisted pyrolysis kinetic behaviors and dielectric properties of biomass components

The kinetic characteristics of microwave‐assisted pyrolysis (MAP) of biomass components were investigated in a self‐designed microwave thermogravimetric analysis using the KAS model and the master plot method. Compared with conventional pyrolysis, the initial decomposition temperatures of biomass components were reduced by 50–100°C and the fastest weight loss regions were shifted to lower temperatures. The average apparent activation energies of cellulose, hemicellulose, and lignin were 47.82, 44.81, and 51.54 kJ/mol, respectively. Analysis with master plot method suggested the MAP of cellulose followed the 2‐D diffusion reaction model, while hemicellulose and lignin could be interpreted by third order‐based and 3‐D diffusion model. The change of dielectric properties was consistent with the weight loss behaviors of biomass components during the pyrolysis process. The increase of dielectric properties with temperature can lead to a thermal gradient and “hot spots” within biomass, which accelerated the pyrolysis process at low temperatures and reduced the apparent activation energy. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2124–2134, 2018     

TG study on pyrolysis of biomass and its three components under syngas

Pyrolysis of sawdust and its three components (cellulose, hemicellulose and lignin) were performed in a thermogravimetric analyzer (TGA92) under syngas and hydrogen. The effect of different heating rates (5, 10, 15 and 20 °C/min) on the pyrolysis of these samples were examined. The pyrolysis tests of the synthesized samples (a mixture of the three components with different ratios) were also done under syngas. The distributed activation energy model (DAEM) was used to study the pyrolysis kinetics. It is found that syngas could replace hydrogen in hydropyrolysis process of biomass. Among the three components, hemicellulose would be the easiest one to be pyrolyzed and then would be cellulose, while lignin would be the most difficult one. Heating rate could not only affect the temperature at which the highest weight loss rate reached, but also affect the maximum value of weight loss rate. Both lignin and hemicellulose used in the experiments could affect the pyrolysis characteristic of cellulose while they could not affect each other obviously in the pyrolysis process. Values of k₀ (frequency factor) change very greatly with different E (activation energy) values. The E values of sawdust range from 161.9 to 202.3 kJ/mol, which is within the range of activation energy values for cellulose, hemicellulose and lignin.     

Kinetic Model of Biomass Pyrolysis Based on Three-component Independent Parallel First-order Reactions

The pyrolysis behavior of two kinds of typical biomass (pine wood and cotton stalk) was studied in nitrogen atmosphere at various heating rates by thermogravimetric analysis (TGA). The pyrolysis process can be divided into three stages: evolution of moisture (<200℃), devolatilization (200~400℃) and carbonization (>400℃). The comparison of DTG curves of two biomass materials show that the higher the hemicellulose content of biomass, the more evident the shoulder peak of DTG curve. The weight loss process of two materials was simulated by the kinetic model assuming cellulose, hemicellulose and lignin pyrolyzing independently and in parallel, obeying first-order reactions. The pyrolysis kinetic parameters corresponding to the three components were estimated by the nonlinear least square algorithm. The results show that their fitting curves are in good agreement with the experimental data. Their activation energy values for pine wood and cotton stalk are in the range of 188~215, 90~102, 29~49 and 187~214, 95~101, 30~38 kJ/mol, respectively. The corresponding pre-exponential factors are in the range of 1.8′1015~2.0′1016, 1.6′107~7.1′108, 9.3′101~1.5′103 and 1.2′1015~6.7′1017, 1.2′108~1.4′109, 1.4′102~4.6′102 min-1, respectively. In addition, the activation energy of cellulose and lignin increased and their contributions to volatile tended to fall, whereas the activation energy of hemicellulose decreased and its contribution to volatile tended to rise with increasing of heating rate.     

动力学参数的补偿效应及改进的求解方法

阐述了目前被许多研究者所运用的模型匹配方法求解动力学参数的不足之处,并从动力学补偿效应的角度来说明一组实验数据可以与多个模型匹配的情况。然后应用 Friedman 法求出了黄桷树叶在4个不同升温速率条件下,黄桷树叶热解的活化能与转化率之间的关系,判断出整个反应过程不遵循单一的动力学反应机制。根据活化能在各个阶段受转化率的影响将黄桷树叶的热解过程划分为两个阶段,然后分别求出了两个阶段的活化能,以它们作为参考活化能,运用 Freeman-Carroll 法求出了反应级数和指前因子。     

Pyrolysis kinetics of forestry residues from the Portuguese Central Inland Region

The pyrolysis behaviour and kinetics of forest shrub wastes (Cytisus multiflorus, Spartium junceum, Acacia dealbata and Pterospartum tridentatum) from the Portuguese Central Inland Region have been studied in a thermobalance, as a previous step for their valorization by pyrolysis in order to obtain fuels and chemicals within the framework of the BioREFINA-Ter project. The kinetic model consists of a multi-component mechanism that describes the volatile formation involving three independent and parallel reaction networks corresponding to the decomposition of the three main biomass pseudo-components: hemicellulose, cellulose and lignin. The thermogravimetric curves and kinetic parameters have been compared with those obtained for other materials, and the chemical features of the biomasses have been determined. Although the samples are highly heterogeneous because of their bark and leaf content, the degradation of these shrubby biomasses is similar to other lignocellulosic materials, evidencing that their valorization by pyrolysis is feasible.     

Structural evolution of chars from biomass components pyrolysis in a xenon lamp radiation reactor

The structural evolution of the chars from pyrolysis of biomass components(cellulose, hemicellulose and lignin)in a xenon lamp radiation reactor was investigated. The elemental composition analysis showed that the C content increased at the expense of H and O contents during the chars formation. The values of ΔH/C/ΔO/Cfor the formation of cellulose and hemicellulose chars were close to 2, indicating that dehydration was the dominant reaction. Meanwhile, the value was more than 3 for lignin char formation, suggesting that the occurrence of demethoxylation was prevalent. FTIR and XRD analyses further disclosed that the cellulose pyrolysis needed to break down the stable crystal structure prior to the severe depolymerization. As for hemicellulose and lignin pyrolysis, the weak branches and linkages decomposed firstly, followed by the major decomposition. After the devolatilization at the main pyrolysis stage, the three components encountered a slow carbonization process to form condensed aromatic chars. The SEM results showed that the three components underwent different devolatilization behaviors, which induced various surface morphologies of the chars.     

芦苇秆热解特性及动力学分析

为了充分利用芦苇秆生物质能源,以不同升温速率对芦苇秆进行热重实验,分别运用Coats-Redfern（CR）法、Flynn-Wall-Ozawa（FWO）法、Kissinger-Akahira-Sunose（KAS）法计算芦苇秆热解动力学参数,并利用主函数图法确定反应机理和动力学。结果表明：芦苇秆热解可分为4个阶段,其中190~400℃为主要热解阶段。在此阶段,将3种方法计算所得转化率（α）与实验数据进行对比,发现当温度大于250℃时,Coats-Redfern法计算值与实验数据偏差较大,而Flynn-Wall-Ozawa法与Kissinger-Akahira-Sunose法在整个阶段内吻合度较高。由主函数图法可知芦苇秆热解最佳反应机理为随机成核,反应级数为2。对比残差平方和发现,Kissinger-Akahira-Sunose法相比于Flynn-Wall-Ozawa法更适合计算芦苇秆热解动力学参数,计算的表观活化能随转化率的增大呈先增大后减小的趋势,并在转化率为50%时达到最大值286.9 kJ/mol。     

Pyrolysis kinetics and product properties of softwoods,hardwoods, and the nut shell of softwood

The pyrolysis of softwoods (Pinus (P.) densiflora, P. koraiensis), hardwoods (Quercus acutissima and Liriodendron tulipifera) and nut shell of P. koraiensis was investigated using a thermogravimetric analyzer and fixed bed reactor. Thermogravimetric analysis showed that the maximum decomposition temperature of each biomass was influenced by the ash content and lignocellulosic composition of biomass. The activation energy values also varied according to the content of hemicellulose and lignin of each biomass. Large amounts of acids, such as acetic acid, were recovered from the hardwood pyrolysis reaction due to their high hemicellulose content. The nut shell of P. koraiensis and softwoods with a higher lignin content produced higher yields of phenolic compounds than the hardwoods.