大豆的热分解特性及其动力学探究

动态热重分析（TGA）被用来研究大豆的热降解动力学,通过改变大豆热解时的升温速率（5,10,20和40℃/min）以及气氛条件（氮气和空气）探索了大豆在不同热解条件下的热解特性。并结合对相应热解条件下的动力学参数（表观活化能E_k）进行求解,探究了大豆的火灾安全性。结果表明,大豆的热解可以分为四个阶段：前两个阶段对应自由水和结晶水的脱除,后两个阶段对应主要成分（淀粉、蛋白质和脂肪）的次分解阶段和主要分解阶段。后两个阶段,由于氧气的存在,导致大豆的热分解出现了不同的历程,800℃时的残炭率降低。且与氮气气氛下热解相比,大豆在空气气氛下表现出更低的反应活化能和火灾安全性。     

Thermal degradation kinetics of rigid polyurethane foams blown with water

The thermal decomposition behavior of rigid polyurethane foams blown with water was studied by dynamic thermogravimetric analysis (TGA) in both nitrogen and air atmosphere at several heating rates ranging from room temperature to 800°C. The kinetic parameters, such as activation energy (E), degradation order (n), and pre‐exponential factor (A) were calculated by three single heating rate techniques of Friedman, Chang, and Coats–Redfern, respectively. Compared with the decomposition process in nitrogen, the decomposition of foams in air exhibits two distinct weight loss stages. The decomposition in nitrogen has the same mechanism as the first stage weight loss in air, but the second decomposition stage in air appears to be dominated by the thermo‐oxidative degradation. The heating rates have insignificant effect on the kinetic parameters except that the kinetic parameters at 5°C/min have higher values in nitrogen and lower values in air, indicating different degradation kinetics in nitrogen and air. The kinetic parameters of foam samples blown with different water level in formulation decline firstly and then increase when water level increases from 3.0 to 7.0 pph. According to the prediction for lifetime and half‐life time of foams, water‐blown rigid foams have excellent thermostability, when used as insulation materials below 100°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:4149–4156, 2006     

Pyrolysis kinetics of Athabasca bitumen using a TGA under the influence of reservoir sand

Pyrolysis kinetics of thermal decomposition of bitumen was investigated by thermogravimetric analysis (TGA). TGA experiments were conducted at multiple heating rates of 5, 10, 20°C min^–1 up to 800°C to obtain the pyrolysis characteristics of bitumen. Weight loss curve from TGA shows that two different stages occurred during bitumen pyrolysis. Differential method has been used for determining the kinetic parameters and the best fit for the order of reaction was found based on the R² values. Kinetics results confirm the presence of two different stages in bitumen pyrolysis with varying kinetic parameters. The average activation energy for the first and second stage was 29 and 60 kJ mol^?1 and the average order of the reaction was 1.5 and 0.25, respectively. Experiments have been conducted with different reservoir sand. The effect of different source of sand reveals no effect on the pyrolysis behaviour of bitumen. A considerable difference was found with the pyrolysis of bitumen–sand mixtures and bitumen alone based on coke yield and activation energy. © 2011 Canadian Society for Chemical Engineering     

Two-Stage pyrolysis model of PVC

The pyrolysis of polyvinyl chloride (PVC) was examined with a thermal gravimetric analyzer (TGA). The experiments were carried out over the temperature range of 400-800 K at three heating rates of 1, 2, and 5.5 K/min and in a nitrogen atmosphere. The results indicate that the entire process of PVC pyrolysis under the experimental conditions of this investigation consists of two distinct pyrolysis stages, namely, the thermal dehydrochlorination and the breakdown of the intermediate products produced after the dehydrochlorination stage. The corresponding activation energy, pre-exponential factor, and reaction order were determined. A two-stage pyrolysis model, which is composed of four reactions including a number of independent, consecutive and competitive reactions with volatiles and solid products, was developed. This kinetic model gives good agreement with the experimental results.     

聚酰胺12非等温热分解动力学研究

在不同升温速率下,利用热重分析法研究了聚酰胺12（PA12）在氮气氛围中的热分解动力学。运用Freeman Carroll、Kissinger、Ozawa、Achar和Coats Redfern方法计算和确定了PA12在氮气氛围中的热分解活化能和热分解机理及其模型。结果表明,在氮气氛围中,PA12的热分解活化能为246.5 kJ/mol,指前因子为1014.71;PA12热分解机理为收缩球体法则,机理方程的微分形式为f(α)=3(1-α)2/3,积分形式为G(α)=1-(1-α)1/3。     

长白松热解特性及热解动力学研究

为获取长白松的热解特性,预防森林火灾发生,以长白松的树枝、球果、树皮和松针作为研究对象进行热解过程分析,并采用Coats-Redfern法进行热解动力学分析,以球果为研究对象探究各种因素对长白松热解的影响。实验结果表明：4种材料的热解过程均可分为4个阶段,其中主要失重阶段的质量损失率为60%左右。升温速率越大,热解越不充分,并且存在热滞后现象,25℃/min时质量损失率最小(80.34%);粒径大小对TG、DTG曲线影响较小,粒径越小,内外部受热更均匀,因此0.20 mm粒径的材料质量损失率最大(91.18%);氮气气氛下主要失重阶段有一个失重峰,而在高纯空气气氛下有两个失重峰,且长白松球果在高纯空气中热解时间更长,热解更充分,促进作用更强,质量损失率为98.14%。热解动力学分析结果显示：4种材料的最佳机理函数为“三维扩散”,活化能最大的是树枝(157.04 kJ/mol),最小的是松针(98.19 kJ/mol),球果的活化能为148.08 kJ/mol,树皮的活化能为115.04 kJ/mol,因此,要格外注意对松针和树皮的防火工作。     

Thermal decomposition of petroleum and coal tar pitches by thermogravimetry

Thermogravimetry was used to investigate petroleum and coal tar pitches undergoing pyrolysis in an atmosphere of air and nitrogen at three different heating rates. Pyrolysis of pitches in air is a three-stage process, whereas in nitrogen two stages were found. A kinetic analysis of the thermogravimetric data has been made. The orders and activation energies have been determined for each stage of decomposition using the methods of Kissinger, Freeman, and Hüttinger.     

Multiscale thermal study of virgin and aged polyphenylene sulfide reinforced by glass fiber

In this study, virgin and thermal aged PPS samples were prepared and tested using different techniques such as thermogravimetric analysis (TGA), coupled TGA–Fourier transform infrared spectroscopy (FTIR), and FTIR as well as optical microscopy. Some interesting research results can be summarized as follows: TGA results prove the PPS composite samples aged at 180 and 200°C have been degraded obviously during the aging period in oven. Moreover, accelerated aging leads to the degradation of PPS composite with the observation of increased thermal oxidation layer from outside to inside. There is a plateau standing at about 350 μm for the thermal oxidation layer at oxidation temperature of 200°C. Some thermal decomposition models are applied to clarify the degradation kinetics of PPS composite. According to the activation energy value, it appears degradation more easily at the beginning of the heating process in the atmosphere of oxygen than that of nitrogen. Moreover, the related products of PPS composites during pyrolysis are fully discussed with the combined analysis of TGA–FTIR techniques.     

Interaction of a phosphorus‐based FR,a nanoclay and PA6—Part 1: Interaction of FR and nanoclay

The thermal decomposition of organophosphorus fire‐retardant (OP1311) and/ or organonanoclay (Cloisite 30B) is hereby investigated employing thermogravimetric analysis (TGA), to give an insight into their intrinsic behaviour and interaction in polymer nanocomposites for fire safety applications, because the addition of OP1311 and Cloisite 30B in Polyamide 6 (PA6) seems to have a synergistic effect on the thermal decomposition of PA6 (part 2 of the paper). An important objective of this research was to determine to what extent phosphorus components escape in the gaseous phase, which will affect the heat of combustion of the fire‐retarded polymer. The decomposition products arising from pyrolysis and combustion are investigated by means of Fourier transform infrared spectroscopy. Under pyrolytic conditions, the inclusion of Cloisite 30B into OP1311 (FR) shows a synergistic effect on the initial mass loss at low temperature of ～280–420°C and leads to the acceleration of the thermal degradation process. While the DTG curve of Cloisite 30B shows two distinct degradation peaks (steps) that of OP1311 and OP1311 plus Cloisite 30B show four degradation steps. TGA measurements of OP1311 in nitrogen show more mass loss than in air, whereas Cloisite 30B gives similar amounts of mass loss in air and nitrogen. In nitrogen, the major evolved gaseous species from Cloisite 30B alone are hydrocarbons, 2‐(diethylamino)ethanol and water, whereas the evolved gases from that of OP1311 at ～320°C are mainly water, at ～420°C, carbon dioxide, water and ammonia and at 480–570°C diethylphosphinic acid. Under thermo‐oxidative conditions, the gases evolved are mainly carbon dioxide and water from both Cloisite 30B and OP1311. Copyright © 2009 John Wiley & Sons, Ltd.     

垃圾衍生燃料燃烧历程的试验研究*

采用热重、质谱和红外测试等热分析技术,对垃圾衍生燃料(RDF)在不同气氛、不同升温速率、不同氧化钙和无烟煤掺量条件下燃烧过程的失重特性进行了研究。结果表明:(1)垃圾衍生燃料的燃烧过程包含四个阶段,第一阶段为自由水的蒸发过程;第二和第三失重段在空气气氛下表现为纤维类和橡胶等物质的裂解与燃烧,在氮气条件下体现为裂解;第四阶段为固定碳的燃烧及燃烧中间产物的分解过程。(2)空气气氛下的失重速率高于氮气气氛。(3)氧化钙和无烟煤的掺入可以提高RDF的着火温度、延缓燃尽时间。     

热解气氛对油漆稀料和塑料共热解特性的影响

为研究不同热解气氛对油漆稀料与聚对苯二甲酸乙二醇酯（PET）共热解特性的变化规律，采用同步热分析仪，根据预实验结果，测定在升温速率为10 ℃/min时，不同热解气氛（空气和氮气）条件下油漆稀料和PET塑料共热解过程中失重（TG）、焓变（DSC）的变化，并采用Coats?Redfern法对样品进行热动力学分析。结果表明，样品在氮气气氛下的热解过程存在明显的滞后现象，质量损失率为82.2 %；在空气气氛中更有利于油漆稀料和PET塑料的共热解反应中间产物的检出；PET塑料及其燃烧残留物在空气中的平均活化能均小于氮气中的值，但混合物在空气中400~475 ℃温度间活化能更低；500 ℃后混合物达到二次燃烧条件。     

Pyrolysis kinetics of highly crosslinked polymethylsiloxane by TGA

The pyrolysis kinetics of highly crosslinked polymethylsiloxane (PMS) was investigated by thermogravimetric analysis (TGA) under both isothermal and elevated temperature conditions with several environmental gases, such as oxygen, nitrogen, air, and helium. A non-chain-scission mechanism composed of initiation, propagation, and termination was proposed to interpret the thermal degradation of highly crosslinked PMS. The mechanism was verified by the experimental results under isothermal conditions. The activation energy of initiation, E_i, was about 20–30 kcal/mol and the activation energy of propagation, E_p, was about 4–6 kcal/mol. These activation energies were found to be different for different gases. The activation energy of initiation for PMS in an aggressive atmosphere, such as oxygen, was lower than that in an inert atmosphere, such as nitrogen. But the activation energy of propagation for PMS was higher in an active environment than in an inert one. There were no direct conclusions about the thermal degradation of highly crosslinked PMS at elevated temperature. Based on thermogravimetric experiments, it is suggested that a pyrolysis process be conducted with a rate of temperature increase less than 10°C/min for preparing the silicon base inorganic membrane.     

Thermal characteristics and pyrolysis of methyl‐di(phenylethynyl)silane resin

Thermal stability of a recently synthesized polymeric methyl‐di(phenylethynyl)silane (MDPES) resin was studied using a number of thermal and spectrometric analytical techniques. The polymer exhibits extremely high thermal stability. Thermogravimetric analysis (TGA) shows that the temperature of 5% weight loss (T_d5) was 615°C and total weight loss at 800°C was 8.9%, in nitrogen atmosphere, while in air, T_d5 was found to be 562°C, and total weight loss at 800°C was found to be 55.8% of the initial weight. Differential thermal degradation (DTG) studies show that the thermal degradation of MDPES resin was single‐stage in air and two‐stage in nitrogen. The thermal degradation kinetics was studied using dynamic TGA, and the apparent activation energies were estimated to be 120.5 and 114.8 kJ/mol in air, respectively, by Kissinger and Coats–Redfern method. The white flaky pyrolysis residue was identified to be silicon dioxide by FTIR and EDS, indicating that the thermal stability of polymer may be enhanced by the formation of a thin silicon dioxide film on the material surface. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 103: 605–610, 2007     

Strategy for kinetic parameter estimation—Thermal degradation of polyurethane elastomers

The kinetics of the thermal degradation of polyurethane (PU) elastomers based on poly(ether polyol) soft segments and an aromatic type of diisocyanate were investigated by thermogravimetric analysis (TGA) under a nitrogen atmosphere employing four heating rates. The corresponding kinetic parameters of the two degradation stages were estimated by minimizing the output error functional and by the Kissinger method. In evaluating the kinetic parameters of the two‐step PU thermal decomposition, a differential thermogravimetry curve was applied as an objective functional in a regression procedure. Parameter estimation was obtained by minimizing the weighted quadratic output error functional with the modified Nelder–Mead simplex search algorithm. The confidence regions in the preexponential factor‐activation energy space were established for both the first and second stages of degradation. The effect of the molecular weight of the soft segment and the content of the hard segment on the activation energy of the degradation process was constructed by response surface methodology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 764–772, 2007     

CoMoP/13X催化剂上黄土庙煤热解特性研究

采用等体积浸渍法制备了CoMoP/13X催化剂,利用TG-FTIR技术研究了该催化剂对黄土庙煤热解失重特性和气态产物生成规律的影响,并对不同条件下的煤热解过程进行了动力学分析.结果表明,CoMoP/13X催化剂对黄土庙煤加氢热解有明显的催化作用.与原煤热解相比,催化加氢热解的第二个热解峰温和二次脱气阶段的表观活化能分别降低了27.7℃和7.9 kJ/mol.在线FTIR实验结果表明,CoMoP/13X催化剂可以改善黄土庙煤热解产物的组成与分布,热解产物中CO2较大幅度降低,芳烃化合物和脂肪族化合物显著增加,CH4和CO等高热值气体有不同程度的增加.     

添加剂对烤烟烟气焦油和CO释放量的影响

在烤烟样品中添加KNO3和KClO3添加剂,采用烟支抽吸测试,结合热重-微分热重-差示扫描量热法联用热分析技术分析添加剂对烤烟燃烧污染物(焦油和CO)释放和烟丝样品热解燃烧的影响,研究烤烟燃烧污染物释放的反应阶段与其燃烧动力学的关系. 结果表明,KNO3和KClO3均能不同程度降低烤烟的抽吸口数、CO释放量及焦油量. KNO3比KClO3更显著地降低烤烟样品在大分子挥发分热解燃烧阶段(504.15~696.15 K)的活化能,促进该阶段的反应,降焦效果明显;而KClO3对烤烟残炭燃烧阶段(696.15~852.15 K)的促进效果略低于KNO3,但其在烤烟小分子挥发物热解挥发阶段(407.15~504.15 K)的促进作用非常明显,两个阶段的综合效果优于KNO3,降低烤烟CO释放量的作用更明显. 同时还研究了添加剂对烤烟燃烧各阶段的反应动力学及反应机理的影响.     

防溴型环氧树脂电路板热解动力学分析

引言印刷电路板(printed circuit boards,PCBs)作为一种热固性复合材料,被广泛应用于电子元件与电动控制等多种工业领域[1-2]。印刷电路板主要由玻璃纤维、环氧树脂以及多种金属材料组成[3]其中环氧树脂被认为是最难降解回收的废旧塑料之一[4]。     

新型硬质聚氨酯泡沫的热分解行为及动力学

利用热重分析法比较研究了新型硬质聚氨酯泡沫[超支化聚氨酯多元醇型(HBPU型)]和硬质聚氨酯泡沫(RPUF)在氮气中的热分解行为,探讨了HBPU型RPUF在不同升温速率下的热分解动力学,运用Kissinger最大失重率法和Flynn-Wall-Ozawa等失重百分率法计算获得了其热分解过程的活化能。研究结果表明,HBPU型RPUF的初始分解温度(T5%)为205℃,半寿温度(T50%)为361℃,略低于传统的RPUF。Kissinger法得到的HBPU型RPUF的热分解表观活化能为159.8 kJ/mol;Flynn-Wall-Ozawa法得到的热分解过程分为三个阶段:第一阶段的平均活化能为82.8 kJ/mol,第二阶段的平均活化能为140.7 kJ/mol,第三阶段的平均活化能为111.3 kJ/mol,HBPU型RPUF具有较好的热稳定性。     

污水污泥气化焦油热解特性的研究

利用热重分析方法,对由5种不同性质污泥在气化温度600℃、700℃和800℃下进行外热上吸式固定床空气气化时制得的9种污泥气化焦油的热解特性进行了研究.结果表明:9种气化焦油热解时均分为3个阶段,分别是水和低沸点有机物的挥发、有机物挥发分解以及残余物分解.污泥厌氧消化和污水处理工艺中的厌氧过程均使800℃下制得的气化焦油中低分子有机物含量增加,但对第二阶段挥发的轻质及重质非极性有机物总含量的影响很小,且使气化焦油的热解特性变差.气化温度对未消化污泥气化焦油热解时第一和第二阶段失重率的影响变化规律与消化污泥气化焦油的不同,且气化焦油的热解特性优于污泥热解焦油.热解动力学研究表明,9种气化焦油热解机理函数彼此不完全相同,且热解活化能均较低,具有良好的热解特性.     

十溴二苯醚热解动力学及在聚苯乙烯中的热解行为

十溴二苯醚(decaBDE)是多种聚苯乙烯(PS)类塑料阻燃添加剂,其热解动力学对开发新型高效的电子塑料安全处置技术具有十分重要的意义,为此采用普适积分法成功关联了氮气中decaBDE的热解动力学参数。结果表明:固体decaBDE在306℃时熔融为液相并在400~450℃进一步汽化为气相,热重/红外(TG/IR)分析表明,其气相产物组成具有与decaBDE相同的红外特征;decaBDE热解过程可用三维扩散模型关联。进而通过对比分析decaBDE、PS和含decaBDE的阻燃PS样品的TG实验结果,发现阻燃塑料样品在热解时存在decaBDE与PS间的相互作用,表现为热解起始温度的降低和终止温度的升高。TG/IR分析表明:阻燃塑料样品的热解气相产物中不存在游离的HBr,decaBDE热解时产生的活性基团改变了PS的降解反应历程,使其气相产物具有与1,3-二苯基丁烷类似的红外特征。