热分析法研究五倍子醛的热稳定性及其分解动力学

采用热重法,以氮气为保护气,分别在5、10、15、20℃/min的升温速率下,测得五倍子醛的热重-微分热重(TG-DTG)曲线,并在10℃/min的升温速率下测得样品的差示扫描量热(DSC)曲线。结合热失重数据和五倍子醛结构对其分解机理进行推断和验证,并运用双外推法对五倍子醛的热解动力学进行分析,求得原始状态和热平衡态下的动力学参数。研究结果表明,五倍子醛晶体在升温过程中先经历了非结合水和结合水的受热挥发阶段,然后在163℃之后发生热分解,分子中醛基断裂失去1分子的CO;随着升温速率的升高,五倍子醛的分解反应向高温区域移动,最大失重速率依次减小;热解活化能Eα为286.21 kJ/mol,指前因子lnA为70.21,热解机理函数g(α)=[-ln(1-α)]2/3,反应级数n=2/3;热解活化能随转化率的增加逐渐减小;经动力学参数推断,在室温(25℃)下,五倍子醛的贮存期为4～5年。     

酚醛树脂保温板热分解过程的lnln法研究

采用热重分析仪研究酚醛树脂保温板粉体热解行为。采用lnln法探讨等温热解过程动力学,采用Eyring方程探讨热解活化热力学参数。结果表明:酚醛树脂保温板粉体,在800℃内,非等温热解分为四个阶段,各阶段失重率依次为9%、10%、24%、25%;低于523K和高于573K时等温过程热解失重率低于523-573K温度段。lnln法获得酚醛树脂保温板粉体热解表观活化能为40.36 kJ·mol~(-1);Eyring法获得热分解的摩尔活化焓△H~≠、摩尔活化熵△S~≠分别为35.87 kJ·mol~(-1)和-202 J·mol~(-1)·K~(-1),摩尔活化自由能△G~≠值在讨论温度范围内皆为正,表明热解过程需要引入热量并且为非自发分解反应,热解需要经历活化络合态且络合态系统比初始状态更有序。     

低熔点DNAN/RDX混合材料的热行为及分解机理

利用动态测压热分析法(DPTA)、差式扫描量热法(DSC)、热重分析法(TG)、热烤法研究了低熔点含能材料DNAN/RDX的热行为和分解机理。研究得到结论：1)DPTA法测试结果表明DNAN/RDX的热安定性较好；在固相分解阶段，运用Satava-Sestak法得出20～100℃时非等温固相分解阶段机理函数为G(α)=[(1-α)^-1/3-1]²,E_S=85.64 kJ/mol, lgA_s=11.57;等温阶段的等温分解动力学机理函数为G(α)=[(1-α)^1/3,反应速率常数k=1.515 32×10^-4。2)DSC法和TG法研究结果表明RDX主要为熔融液相形式分解，DNAN主要为气相形式分解；混合体系中RDX促进了DNAN的分解过程，DNAN/RDX的受热质量损失过程主要为DNAN的挥发过程和RDX的热分解过程。运用DSC法研究升温速率为5℃/min时DNAN/RDX的热分解过程，普适积分法得出在224～320℃范围内的分解过程机理函数为G(α)=[-...     

典型海鲜废弃物热解特性及动力学研究

本研究采用热重分析手段，对鱼骨、蟹壳、虾壳三种典型海鲜废弃物的热解特性进行分析，研究不同升温速率(20、40、60℃/min)条件下热解过程的特征参数，分析原料成分组成对于海鲜废弃物热解特性的影响。基于热解特性参数对热解过程进行动力学分析，结合表观动力学参数并在对比多种机理模型的拟合效果基础上，确定了较为适宜的海鲜废弃物热解过程机理模型。结果表明，海鲜废弃物热解过程与其成分组成具有密切关联，TG-DTG曲线对比分析发现，有机质和无机盐含量是影响热解过程的重要因素。随着升温速率的提高,三种海鲜废弃物的热解特性参数具有一致的增长趋势。动力学研究发现，鱼骨主要热解过程符合一级化学反应机理，而蟹壳和虾壳在有机物分解阶段可由一段1.5级化学反应过程描述，分析认为，反应级数的差别与与海鲜废弃物中几丁质含量有关。表观活化能Ea随着升温速率的提高而增大，而活化能增量?E_α逐渐变小，可以推测采用不低于40℃/min的升温速率不会导致三种海鲜废弃物热解过程难度的增大并更具经济性。研究结果为海鲜废弃物热解处理技术的开发提供了基础过程特性数据。     

低阶烟煤热解过程中氯的迁移释放特性研究

为探明氯元素在低阶烟煤热解过程中的释放机制行为,采用热重红外光谱质谱(TG-IR-MS)联用技术和管式热解炉,考察热解温度、粒径等级、升温速率对陕北低阶烟煤热解过程中氯的迁移转化行为特性的影响,并建立氯迁移释放动力学模型。红外光谱和质谱分析结果表明,陕北低阶烟煤热解气体产物中含氯组分主要为HCl和微量的Cl_2。管式炉热解过程中,相比于粒径和升温速率而言,氯的释放率受温度影响最为显著。在300-800℃,随着温度升高,煤中氯的释放率迅速增大,800℃时氯的释放率为49.5%;半焦中氯的分布率逐渐减小,焦油和热解气中氯的分布率逐渐增大。煤样粒径为3.0-4.0 mm时,氯的释放率达到最大值35.8%;粒径的变化也会一定程度影响热解产物中氯的分布率。提高热解升温速率有利于挥发分的释放,升温速率为15-25℃/min时,煤中氯的释放率变化趋势明显,但过高的升温速率不利于煤中氯的释放。热解焦油中氯元素主要以无机含氯化合物的形式存在,超纯水萃取可明显降低焦油中氯的含量。低阶烟煤中低温热解过程中,氯释放的活化能均在20 k J/mol左右。     

升温速率对氨基酸裂解生成含氮气体的影响研究

为进一步阐明卷烟烟气中含氮有害气体的形成机理,以甘氨酸、天冬酰胺和天冬氨酸为研究对象,采用TG-FTIR技术对其在不同升温速率下热解时含氮气体的释放特性进行了研究。结果表明:(1)随着升温速率增加,三种氨基酸TG和DTG曲线各个失重阶段的起始和终止温度向高温侧移动;(2)氨基酸结构不同,HCN、NH3、HNCO的生成温度及生成量不同;(3)增加升温速率,三种氨基酸热解过程中HCN、NH3、HNCO的生成量均增加,但三种氨基酸氮转化的选择性不尽相同。甘氨酸和天冬酰胺热解过程中氮主要转化为NH3,而天冬氨酸在低升温速率下热解时,氮主要转化为HCN和NH3,在高升温速率下主要生成HNCO。     

森林泥炭的热解特性及热解动力学

泥炭阴燃是森林地下火的主要燃烧形式之一, 研究泥炭的热解规律对认识其阴燃机理及地下火蔓延机理有重要意义. 本文使用荧光光谱分析技术测定了我国东北林区一种典型泥炭样品的主要元素组成, 并使用热重-差热分析(TG-DTA)技术研究了泥炭样品在惰性气氛中的热解规律. 实验结果表明, 泥炭样品主要由45种元素构成. 从常温到1073 K高温的升温过程中, 泥炭样品的质量损失过程可以分为三个阶段, 依次为水分损失阶段、有机质热解阶段和矿物质分解阶段. 对于泥炭阴燃密切相关的有机质热解阶段, 结合热分析动力学理论和优化计算方法, 建立了描述泥炭有机质热解动力学规律的三组分叠加反应模型.     

生物质与废轮胎共热解催化热解油蒸发过程及其动力学研究

采用热重微商(TG-DTG)法考察生物质稻壳与废轮胎共热解经催化与非催化热解油的热失重行为，并同0#柴油的热失重行为进行了比较；同时采用Achar微分法和Coats-Redfern积分法对热解油热失重蒸发过程的蒸发热进行了计算，并结合Satava和Bagchi法确定了热失重蒸发过程的机理函数， 建立了0#柴油和在催化与非催化条件下得到的热解油蒸发过程的动力学方程，得出了在催化与非催化条件下热解油热失重过程的机理函数，其动力学方程为dα/dt=Ae-△vapH/RT(1-TBX〗α)2；而0#柴油的热失重蒸发过程动力学方程为dα/dt=1.5Ae-△vapH/RT(1-α)2/3\[1-(1-α)1/3\]-1。蒸发热的顺序由大到小依次为,柴油＞非催化热解油＞SBA-15热解油＞MCM-41热解油。结果表明，通过建立的模型函数得到的蒸发热与实验值非常接近。催化剂SBA-15和MCM-41的存在对降低高沸点馏分的物质具有一定作用，而SBA-15催化作用强于MCM-41。     

污泥热解过程中焦的表面孔隙结构分形生长

主要对污水污泥在高温热解和低温热解条件下热解焦炭的表面孔隙结构特性进行了研究。结果表明,污泥热解过程中随着挥发分的析出,污泥热解焦炭的孔隙结构逐渐发达。低温和高温热解过程中挥发分的析出,使得孔径为3.75 nm的孔得到了极大的发展。通过对污泥热解焦炭的N2吸附过程进行的分形分析发现,不同停留时间低温和高温热解焦炭的表面分形维数可以分为FD-1和FD-2。其中,FD-1主要表征了较大孔(0.86 nm)的表面分形维数,FD-2则主要表征了超微孔(0.86 nm)的表面分形维数。随着热解停留时间的延长,FD-1和FD-2逐渐增大并趋于稳定。与高温热解焦炭的超微孔表面分形维数相比低温热解焦炭出现了较大的增加,而较大孔的表面分形维数则相对低温热解焦炭未见有较大的改变。     

不同升温速率下茂名油页岩的热分解动力学

在热重装置上考察了2.22—12.34K/min间五种升温速率下茂名页岩的热分解过程,结果表明,升温速率的改变对于热解转化率曲线及失重速率曲线有明显的影响。热重数据的动力学处理显示,茂名油页岩的热分解过程系一级反应。与前人多用一个总包一级反应描述页岩的热分解过程不同,本文在三个温度阶段(即大致在385—398℃之前,385—490℃及443—490℃之后)采用三个不同的一级动力学方程予以描述,并确定了各升温速率下相应的动力学参数。升温速率于2.22—12.34K/min范围内的变化对动力学参数无显著影响。     

Pyrolysis characteristics of cellulose derived from moso bamboo and poplar

To compare with pyrolysis characteristics of cellulose from moso bamboo and poplar, samples were pyrolyzed with different heating rates through thermogravimetric analysis (TG). The kinetics was calculated by Kissinger–Akahira–Sunose method. The results showed that pyrolysis process of moso bamboo and poplar fiber included three stages, and the main pyrolysis occurred in the second step. Moso bamboo fiber had a higher start temperature, a lower end temperature and a more mass loss at each heating rate in the main pyrolysis stage. With increase in heating rate, the temperature corresponding to the maximum of mass loss increased and the DTG curve shifted to higher temperature. The reaction rates varied at different heating rates. The activation energy of cellulose from moso bamboo was lower than poplar cellulose, indicating cellulose of moso bamboo was easier to be pyrolyzed. The results from this research will provide guidance to thermal conversion of moso bamboo and poplar.

     

Pyrolysis of olive residue/low density polyethylene mixture: Part I Thermogravimetric kinetics

This paper demonstrates the thermal pyrolysis of olive residue, low density polyethylene (LDPE) and olive residue/LDPE mixture in an inert atmosphere of N2 using thermogravimetric analysis (TGA). Measurements were carried out in the temperature range 300K~973K at heating rates of 2K/min, 10K/min, 20K/min and 50K/min. Based on the results obtained, three temperature regimes were selected for studying the nonisothermal kinetics of olive residue/LDPE mixture. The first two were dominated by the olive residue pyrolysis, while the third was linked to the LDPE pyrolysis, which occurred at much higher temperatures. Discrepancies between the experimental and calculated TG/DTG profiles were considered as a measurement of the extent of interactions occurring on copyrolysis. The maximum degradation temperatures of each component in the mixture were higher than those the individual components; thus an increase in thermal stability was expected. The kinetic parameters associated with thermal degradation were determined using Friedman isoconversional method.     

废轮胎热解特性研究

利用TG/DTG对不同来源的三种废轮胎样品的热解特性进行了研究，并得到了热解动力学参数。结果表明，新旧废外轮胎样品热解趋势基本一致，均经历了一个不明显的失重过程和两个明显的失重过程，其原因是由于废外轮胎中的橡胶组分比较复杂；内轮胎样品中的组分比较单一，其热解过程比较简单，仅经历了一个不明显的失重过程和一个明显的失重过程；三种样品的主要失重温度为600K～800K，转化率为0.2～0.8；使用一级动力学反应模型很好的拟和了三种样品的主要失重过程，并求出了热解动力学参数。     

氧离子导体La2Mo2O9中α→β相变非等温动力学的研究

以差热分析(differential thermal analysis,DTA)为手段研究了La2Mo2O9中α→β相变的非等温动力学。采用Flynn-Wall-Ozawa法计算了不同转化分数下的相变活化能E,并用Ozawa迭代法对E值进行了修正。应用Criado-Ortega法获得了α-La2Mo2O9→β-La2Mo2O9相变各温度区间的动力学机理函数,并用譒atava-譒esták法进行了验证。结果表明:La2Mo2O9中α→β相变的表观活化能与转化分数有关,说明该相变不属于一步简单反应。不同温度区间α→β相变的动力学机理函数不同,836～840K、842～848 K和850～853 K的动力学机理函数G(x)可依次表示为:-ln(1-x)、[-ln(1-x)]2/3、[-ln(1-x)]3/4。     

蔗渣的热解与燃烧动力学特性研究

利用热重分析仪对蔗渣在不同升温速率下的热解、燃烧失重特性进行了研究。采用Friedman法对反应过程中可能存在的反应机理进行初步判断，蔗渣热解过程由其主要组分半纤维素、纤维素和木质素热解的三个独立的平行反应来描述，相应的反应活化能分别为203.92 kJ·mol-1、238.50 kJ·mol-1和77.11 kJ·mol-1； 蔗渣燃烧过程分为两段，第一段类似于其热解过程，第二段由木质素热解和残焦燃烧共同组成的连续反应，反应活化能为255.57 kJ·mol-1和159.11 kJ·mol-1。通过非线性回归法拟合获得的曲线与实验曲线基本一致，证实了蔗渣的热解、燃烧过程中存在着上述假定的反应机理。     

A kinetic investigation on the pyrolysis of Seguruk asphaltite

The pyrolysis of Seguruk asphaltite has been investigated using thermogravimetric analysis at atmospheric pressure between 293 to 1223 K at different linear heating rates of 5, 10 and 20 K min⁻¹ under nitrogen as ambient gas. There was a two-stage thermal decomposition. Thermal decomposition started around 630 K for stage 1 for the slowest heating rate. On the other hand, for the same heating rate and stage 2, thermal decomposition started around 950 K. These values were shifted to higher temperatures with increasing heating rate. In this study, two different Coats-Redfern methods were applied to thermal degradation of Seguruk asphaltite.     

Pyrolysis and TG Analysis of Shivee Ovoo Coal from Mongolia

The coal sample of the Shivee Ovoo deposits has been non-isothermally pyrolysed in a thermogravimetric analyser to determine the influence of temperature, heating rate and purge gas employed on the thermal degradation of the sample. The heating rates investigated in the TG were 10–50 K min^–1 to final temperature of 1000°C. N₂or CO₂ were employed as well as type of purge gas on the process of thermal degradation of the coal sample. The coal was also investigated in a fixed bed reactor to determine the influence of temperature and heating rate of the pyrolysis on the yield of products and composition of the gases evolved. The main gases produced were H₂, CH₄, C₂H₂, C₂H₄, C₂H₆, C₃H₆ and C₃H₈ and also minor concentrations of other gases. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal Behavior of Zn(Thr)SO_4·H_2O

IntroductionRecently,a considerable interest has been fo-cused on the complexes of zinc with amino acidsdue to their excellent additives in medicine foodstuff and cosmetics[1— 6] .The investigation on thethermal behavior and the thermochemistry of somezinc amino acids is important to its further applica-tion,which has been reported in references[4,5 ,7— 1 0 ].However,the studies on solid complexZn( Thr) SO4· H2 O has not been reported,whichcan provide the necessary data and the foundation…     

Non-isothermal degradation kinetics of MMA-St copolymer and EPS lost foams

Methylmethacrylate-styrene (MMA-St) random copolymer was synthesized by suspension copolymerization. The thermal degradation of MMA-St copolymer and EPS lost foams was studied by non-isothermal thermal gravimetric analysis under nitrogen purge. Thermal decomposition behavior of MMA-St copolymer lost foam was examined and compared with EPS. It was found that EPS foam starts to decompose at higher temperatures than MMA-St copolymer foam in all heating rates. The apparent activation energy was calculated by the Flynn-Wall-Ozawa method. It has been concluded that the model fitting methods unable to reveal the complexity of the pyrolysis process and the model-free methods can be suggested as a reliable way of determining the kinetic parameters.     

马瑞原油在空气和氮气中的热解-氧化性能

低温氧化是注空气采油及原位燃烧采油技术中的重要化学反应,为深入认识原油在有氧环境下复杂热反应过程中的低温氧化特性,我们采用热重/差热分析法(TG/DTA)研究了线性升温和等温条件下马瑞(Merey)原油的热反应行为。 结果表明,Merey原油在空气及线性升温条件下的受热过程分4个阶段:气化段、低温氧化段、热解段和高温氧化段;相邻阶段的物理、化学主导过程的重叠增加了分析原油热反应特征的难度。 升温速率提高,气化段和低温氧化段的终止温度不变;热解段和高温氧化段的终止温度以及热解段的峰温随升温速率的增加而升高。 N₂气与空气下Merey原油的热重/微分热重(TG/DTG)数据对比表明,升温速率越高,空气下的高温氧化段与热解段重叠程度越大,这有利于燃烧但会降低原油采收率。 空气下等温时的TG/DTA结果表明随升温速率增加,升温至300 ℃时的失重率降低,不利于原油轻组分的气化。 反应温度越高,气化过程时间越长,失重分数越大。 Merey原油在低于300℃时低温氧化反应不是主导反应。