应用分布活化能模型分析伊敏褐煤丝炭腐植酸热解及氢气生成动力学

应用开放体系的热重-质谱(TG-MS)联用技术在5、20和50℃·min-1三个升温速率下对伊敏褐煤丝炭腐植酸(F-HA)和脱灰丝炭腐植酸(DF-HA)的热解行为进行了分析,并利用分布活化能模型(DAEM)分别对其热解和氢气生成动力学进行分析,获得了热解过程和氢气生成的活化能分布函数.结果表明:(1)F-HA热解活化能分布函数呈类Gaussian分布,且具有一定的对称性,主峰位与标准Gaussian分布相一致;DF-HA热解活化能分布函数也呈类Gaussian分布形式,主峰位与Gaussian分布相比,偏向低活化能值.根据转化率与温度、活化能的关系,结合腐植酸的热失重特征,将F-HA热解过程划分为四个阶段,DF-HA热解过程划分为五个阶段,并对腐植酸热解过程中各阶段的化学反应进行了详细讨论.(2)F-HA和DF-HA热解氢气生成活化能分布函数均呈类Gaussian分布,热解氢气生成活化能的整体趋势为随着转化率的升高而增加,但也表现出一定的阶段集中分布特征.根据热解氢气生成的动力学特征,将其生成过程划分为五个阶段,反映了其生成的不同化学反应机制.(3)酸洗脱灰对伊敏丝炭提取出的HA的热解行为、热解过程及热解氢气生成动力学产生了影响.     

煤-焦炉气共热解半焦燃烧动力学特性研究──燃烧模型的建立及其表观活化能动态描述

采用热重分析方法（ＴＧＡ）对煤－焦炉气共热解半焦燃烧动力学特性进行研究,建立了半焦燃烧动力学模型,采用新的数学处理方法,实现了表观活化能在半焦燃烧过程中的动态描述及平均表观活化能的求取。分析结果表明,表观活化能在半焦燃烧过程中呈“两头高、中间低”的“钟”型动态分布,其变化范围为：４７～９５ｋＪ／ｍｏｌ,其中主要燃烧失重阶段（转化率为２０％～８０％）的表观活化能较低且变化幅度较小,约为４７～６０ｋＪ／ｍｏｌ,在燃烧转化率为４０％左右出现最低活化能约４７ｋＪ／ｍｏｌ。同一半焦燃烧过程中,表观活化能与燃烧速率动态分布具有良好的对应关系,即较大燃烧速率对应着较低表观活化能,这说明表观活化能的大小直接体现了半焦燃烧反应活性的高低     

热分析动力学与热动力学

正热分析动力学与热动力学是用热分析和量热技术研究某些物理变化或化学反应动力学的分支学科,是目前热化学最活跃的研究领域之一。热分析动力学主要研究反应过程的活化能和机理函数,热动力学则是在量热学、化学热力学和化学动力学的基础上,通过高精度、自动化和连续式的微     

基于分布活化能模型法的农林生物质热解动力学对比研究

采用热重质谱（TG-MS）联用技术,考察杏壳、小麦秸秆与杨树木屑等典型农林生物质的热解行为及动力学。结果表明,组分差异使得三种生物质在主要反应区间内（200–450℃）表现出不同的特征。采用等转化率法计算发现,杏壳平均活化能为188.22 kJ/mol,秸秆平均活化能为220.77 kJ/mol,木屑平均活化能为175.87 kJ/mol。利用分布活化能模型（DAEM）法计算生物质中各组分的平均活化能,发现三种生物质中存在平均活化能较高的第四组分（杏壳297.44 kJ/mol、秸秆284.35 kJ/mol和木屑309.96 kJ/mol）,而半纤维素与纤维素呈现“秸秆<杏壳<木屑”规律。各类动力学计算方法能够互为补充,等转化率方法的整体计算结果与单组分分布活化能模型法结果接近,方法更简便,而分布活化能模型法可以求得原料不同组分的动力学参数,弥补等转化率法的不足,综合使用可以形成对热解反应更为全面的认识。     

含氟聚酰胺酸亚胺化反应动力学

利用动态热重法研究了两种含氟聚酰胺酸薄膜在连续升温过程中的亚胺化反应动力学.采用积分法确定了两种含氟聚酰胺酸的亚胺化反应动力学函数是g(α)=(1-α)-1-1(其中:α为转化率);分别由Ozawa、KAS和迭代法来求取反应的活化能Ea值.结果表明:由KAS法或迭代法求得的活化能比较可靠.在此基础上得出相关的动力学参数、动力学模型方程和动力学补偿效应表达式,为聚酰亚胺工艺参数的选择和工艺窗口的优化提供了理论依据.     

石墨烯氧化过程中的热分析-质谱以及脉冲热分析方法研究

本文由氧化石墨烯通过水热法制备直接获得石墨烯。采用热重-差热分析方法检测了石墨烯受热过程中的质量变化和氧化温度。利用热分析-质谱联用技术在400-650 ℃温度区间得到了水和二氧化碳正离子质谱峰,这说明石墨烯氧化过程中的质量损失是由羟基水和二氧化碳脱除造成的。同时,还采用非等温热分析动力学方法,利用5、10、15 ℃·min^-1三种不同升温速率获得了石墨烯材料在空气气氛下的热分析动力学参数。通过Kissinger方法计算出石墨烯氧化过程中的活化能（E_a）和指前因子的对数（lg（A/s^-1））分别为155.11 kJ·mol^-1和6.90。利用Ozawa-Flynn-Wall （FWO）方法还建立了活化能和指前因子与反应转化率之间的关系。基于以上研究结果,本工作将对石墨烯在热界面、导热和先进复合材料等领域的应用提供参考价值。     

水蒸气气氛煤中温催化气化动力学研究

以碳酸钾为催化剂,用热天平的等温热重法研究了四种不同变质程度煤焦常压下水蒸气催化气化反应动力学。在加和不加碳酸钾条件下,测定了温度为700~850℃煤焦的化学反应控制条件下的碳转化率与时间的关系。碳酸钾催化剂的加入对变质程度越高煤的气化催化作用越大。加碳酸钾的碳转化率与时间的关系用混合模型和修正随机孔模型可以良好的拟合关联,均相模型关联较差。利用修正随机孔模型拟合关联出了四种煤焦催化水蒸气气化反应的活化能和指前因子,活化能为90.317~167.861kJ/mol,指前因子和活化能之间具有补偿效应。     

碱及碱土金属对准东煤热解特性及动力学影响分析

利用程序升温热重(TG)技术对准东原煤(R-form)和酸洗煤(H-form)样品的热解过程进行了研究,同时,采用分布活化能模型(DAEM)法对两者的热解动力学参数进行了计算。结果表明,准东煤在热解过程中保持了丰富的孔隙结构;碱及碱土金属(AAEM)的存在不会对准东煤大分子网络结构造成显著影响,但会提高准东煤的平衡水分含量及二次脱气阶段挥发分释放速率,降低其主热解阶段挥发分释放速率及热解最终失重率;DAEM法可以在较宽的温度范围内对准东煤的热解过程进行准确的描述,R-form和H-form煤样品的热解活化能均随转化率的增大而升高;相同转化率下R-form煤样品的活化能高于H-form,前者活化能分布函数的最大值出现在261.85kJ/mol处,而后者出现在264.51kJ/mol处;AAEM的存在使准东煤的热解活化能升高且分布更加集中,使其热解反应活性降低;准东煤热解的频率因子与活化能之间呈现明显的动力学补偿效应。     

固相物质热分解反应中活化能异常问题的研究

用热分析法研究固相物质分解反应时,往往因升温速率不同而得到不同的反应活化能。这一异常现象的本质原因在于反应本身的复杂性导致反应活化能服从非均匀分布。本文以此为前提,提出了一种解析热分析实验曲线,计算反应活化能的方法。其特点是将反应活化能视为反应转化率的函数,利用不同升温速率下的多条实验曲线,借助严格的理论处理进行计算,同时建立了反应活化能与反应转化率的定量关系式。文中以固体碳酸钙粉末的分解反应为例,对提出的方法进行了讨论。     

非等温反应过程中新的动力学方程

对于非等温过程中的动力学方程，正确的Arrhenius方程的温度积分应该是从T₂到T₁，但是许多动力学方程中的温度积分是从T到0 K，例如Ozawa等方程。我们的研究指出对于某些反应，这些方程中的活化能存在较大的误差，因此我们提出了一个新的动力学方程。凭借等转化率法，应用新的方程可以精确求解线性或非线性加热过程中化学反应的活化能。用新方程对2个经典反应（聚酰胺的热裂解和一水草酸钙的热分解）的研究表明：Ozawa方程的活化能有时是精确的，有时偏差太大。     

Isothermal and non-isothermal pyrolysis kinetics of Kapton polyimide

The kinetics involved in the thermal decomposition of Kapton^® polyimide 100HN under nitrogen atmosphere were studied by applying various fitting techniques to the isothermal and non-isothermal gravimetric data. The correlation of the reaction mechanism fitting, the analytical model fitting and the isoconversional method to these data was examined in relation to the kinetic parameters and the kinetic predictions. The mechanisms for solid-state reactions fit the isothermal data very well but result in highly uncertain values for the kinetic parameters when applied to the non-isothermal data. Isoconversional methods show that the apparent activation energy depends on the extent of conversion but do not provide information for the reaction order and the pre-exponential factor. Three single heating-rate analytical models by Coats-Redfern, MacCallum-Tanner and van Krevelen were analysed using the non-isothermal data. A multi-heating rate model is proposed and its validity is compared to the single-heating rate models on the basis of kinetic predictions.     

Kinetic study of the thermal decomposition of low-grade nickeliferous laterite ores

This study presents an evaluation of the decomposition kinetic of low-grade nickeliferous laterite by thermogravimetric analysis. Kinetic parameters were calculated using the Ozawa and the iso-conversional Friedman methods. Simplified kinetics models like those based on the reaction order were also applied for the simulations. Two-dimensional shrinkage models of the reaction interface mechanism were adopted as describing the thermal transformation process from non-isothermal kinetic analysis. The iso-conversional method (model-free kinetics) reveals that the decomposition of low-grade nickeliferous laterite does not follow a single mechanism because the determined activation energies and pre-exponential factor are not constant during the course of the reaction.     

过渡金属Schiff碱配合物的研究(Ⅱ)——N-水杨醛甘氨酸三吡啶合镍(Ⅱ)热分解非等温动力学的研究

对由水杨醛及其衍生物所形成的Schiff碱配合物的研究已有不少报道,其中一些配合物具有抑菌、抗癌和抗病毒活性,可作为生物氧载体的模型化合物.     

Thermal degradation kinetics of poly(methylphenylsiloxane) containing methacryloyl groups

The kinetics of the thermal degradation of polymethylphenylsiloxane containing methacryloyl groups (PMPS-M) were investigated by thermogravimetric analysis (TGA). Thermal degradation of PMPS-M had two different processes: “unzipping degradation” and “rearrangement degradation”. The corresponding kinetic parameters of the two degradation stages were determined by using Friedman and Flynn-Wall-Ozawa methods, respectively. Coats-Redfern and Phadnis-Deshpande methods were also used to discuss the probable degradation mechanisms of the two different stages. The results showed that the activation energy obtained from Friedman method was in good agreement with the value obtained using Flynn-Wall-Ozawa method. The solid-state decomposition mechanism followed by the first degradation stage of PMPS-M was a decelerated D₄ type (three-dimensional diffusion controlled reaction). However, as for the second degradation stage of PMPS-M, its solid-state decomposition mechanism corresponded to a sigmoidal A₃ type, a nucleation and growth mechanism.     

地开石热分解过程及非等温动力学研究

Fourier-transform infrared emission spectroscopy was used to study the dehydroxylation behavior of the thermal decomposition of dickite from Chenxi, Hunan Province, China. Dehydroxylation of dickite was followed by a loss of intensity of the 3620.73, 3695.34 cm-1 OH-stretching bands and 916.06, 1009.33 cm-1 OH bending bands. The thermal decomposition was investigated by thermogravimetric analysis (TGA). A good agreement is found with TG curves of dickite and the mass loss is 13.7% (close to the theoretical value). The non-isothermal kinetics of the thermal decomposition of dickite was studied in TG-DTG curves over the temperature range from 298 K to 1123 K by thermogravimetry and differential thermal analysis in air. Mathematical analysis of TG-DTG data using the integral methods (Coats-Redfern equation, HM equation, MKN equation) and differential method (Achar equation) shows that the thermal decomposition of dickite accords F2 mechanism. The kinetic parameters such as the activation energy (E=131.62 kJ/mol), pre-exponential factor (A=108.30 s-1) and reaction order (n=2.1) are reported. The Ozawa method was used to analyse the activation energy of the same sample at different heating rate and gave 133.07 kJ/mol. The kinetic parameters calculated from different equation are rather close to each other.     

双核Cu(I)配合物的热分解非等温动力学

Thermal decomposition process of four benzimidazolyl-containing dicopper(Ⅰ) complexes: [Cu2(OCTB)](ClO4)2•1.5H2O(1), [Cu2 (NMOCTB)](ClO4)2•H2O(2), [Cu2(NBUOCTB)](ClO4)2(3), [Cu2(NBOCTB)](ClO4)2•H2O(4) and their kinetics were studied under the non-isothermal conditions by TG-DTG techniques. The non-isothermal kinetic data were analyzed by means of Achar and Coats-Redfern method respectively. The kinetic equation for the second step of the decomposition of complex (1) can be expressed as: dα/dt=A•exp(-E/RT) •(1-α), the mechanism of this reaction corresponds to "Coring and Growth" with n=1; while for the first step of complex (3) decomposition, dα/dt=A•exp(-E/RT)• (1-α)2, which corresponds to the mechanism of "the second-order chemical reaction".     

Curing kinetic study using a well-controlled multifunctional copolymer based on glycidyl methacrylate

The curing kinetics using a glycidyl methacrylate (GMA)-co-butyl acrylate (BA) statistical copolymer synthesized by atom transfer radical polymerization (ATRP) and a commercial linear diamine (Jeffamine^® D-230) was investigated in the temperature range between 50 and 100 °C. Isothermal experiments using differential scanning calorimetry (DSC) were performed to determine all the kinetics parameters, such as the reaction orders, the activation energy and the rate constants, based on an autocatalytic mechanism proposed by Kamal. The isoconversion method was used to evaluate the variation of the effective activation energy with the extension of the conversion that seems slightly decrease initially, and then increases as the cure reaction proceeds. In addition, dynamic kinetic parameters were calculated from non-isothermal experiments using the Kissinger and Ozawa methods. The resulting epoxy resin presents similar physical characteristics to some reported in the literature.     

非等温TG- DTG法确定2,2'- 联吡啶- 对甲氧基苯甲酸铕(Ⅲ)热分解反应的机理函数和动力学参数

采用TG-DTG和DTA技术研究了2,2'-联吡啶-对甲氧基苯甲酸铕(Ⅲ)在静态空气中的非等温热分解过程及动力学,根据TG曲线确定了热分解过程中的中间产物及最终产物,运用微分法与积分法对非等温动力学数据进行分析,推断出第一步的动力学方程为dα/dt=Aexp(-E/RT)2(1-α)1/2.     

Mg(OH)2热分解反应的非等温动力学研究

用非等温动力学方法对氢氧化镁的热分解动力学进行了研究. 分解反应机理符合晶核形成及生长机理A，且随着升温速率的升高，机理由A2转变为A1.5. 根据Kissinger非机理方程计算和数值回归方法验证所得的分解反应活化能结果相互印证，约为148 kJ•mol^-1. 进一步研究发现，水蒸气的存在对氢氧化镁热分解反应具有非常明显的影响，可能是其动力学机理随升温速率升高而改变的主要影响因素.