1-丁基-3-甲基咪唑二氰胺盐离子液体的热稳定性和热分解动力学(英文)

Thermal stability and thermal decomposition kinetics of 1-butyl-3-methylimidazolium dicyanamide ([bmin+][N(CN) ]2-) were investigated using both isothermal and non-isothermal thermogravimetric analyses (TGA) under high pure nitrogen as carrier gas. The long-term thermogravimetric studies revealed that the highest temperature used should be 110 °C, at which [bmin+][N(CN)2-] lost less than 10% by mass in 10 hours. The non-isothermal activation energy values determined using Friedman and ASTM methods were (150±13) and (147±2) kJ·mol –1 , respectively. Multivariate non-linear-regression methods showed that expanded Fn and CnB models were the best fit models with highest correlation coefficient of 0.9994, and the apparent activation energies were consistent with iso-conversional methods.     

Non-isothermal decomposition kinetics of hydrogarnet in sodium carbonate solution

Carbonation decomposition of hydrogarnet is a significant reaction of the calcification-carbonation new method for alumina production by using low-grade bauxite. In this work, non-isothermal decomposition kinetics of hydrogarnet in sodium carbonate solution was studied by high-pressure differential scanning calorimetry (HPDSC) at different heating rates of 2, 5, 8, 10, 15 and 20 K·min^-1, respectively. The activation energy (E_a) was calculated with the help of isoconversional method (model-free), and the reaction mechanism was determined by the differential equation method. The calculated activation energy of this reaction was 115.66 kJ·mol^-1. Furthermore, the mechanism for decomposition reaction is Avrami-Erofeev (n = 1.5), and the decomposition process is diffusion-controlled.     

基于热重-红外联用技术分析油酸的热解特性及动力学分析

利用热重红外联动技术（TG-DTG-FTIR）研究了橡胶籽油中的单不饱和游离脂肪酸油酸组分在不同升温速率（5℃/min、10℃/min、20℃/min、30℃/min）下的热解特性。然后,用多元线性回归法对油酸非等温热解所得到的特性参数进行研究并计算,求得不同升温速率下对应的反应级数、活化能和指前因子,并对不同升温速率下油酸热解反应活化能和指数前因子作线性拟合。结果表明：油酸热解过程主要可分为0～268℃和268～300℃两个阶段,由红外谱图特征峰的分析可知,不同升温速率下,在油酸热解的阶段内均出现了水蒸气、CH₄、CO₂和CO这4种主要气体挥发分。随着升温速率的增大,油酸热解的最大失重速率随之增大,热解区间也向着高温段移动,同时计算在升温速率从5～30℃/min的过程中,反应级数n=1时,热解反应活化能由105.57kJ/mol降低至93.99kJ/mol,指数前因子由6.99×10⁶降低至6.7×10⁵;n≠1时,热解反应活化能由102.45kJ/mol降低至93.38kJ/mol,指数前因子由3.13×10⁶降低至2.97×10⁴,反应活化能和指数前因子随升温速率的增大出现明显减小。通过对不同升温速率下油酸热解反应的活化能和指数前因子进行线性拟合后发现,两者间具有较好的补偿效应。     

杯［6］芳烃热解及热动力学特性分析

在氮气氛围中，利用热失重分析方法对杯［6］芳烃与对叔丁基杯［6］芳烃的热解特性进行了研究，同时采用热分解动力学分析方法计算了反应过程对应的活化能以及最优机理函数方程。结果表明，对叔丁基杯［6］芳烃由于叔丁基的不稳定性导致其初始热分解温度同杯［6］芳烃相比提前约160 ℃，此之后的分解过程同杯［6］芳烃基本一致（即发生桥联的亚甲基断裂与母体苯环的热裂解），整体上残炭量杯［6］芳烃略高10 %；热解动力学分析表明，依据Kissinger和Flynn?Wall?Ozawa方法求出的杯［6］芳烃反应活化能分别是387.87 kJ/mol和376.28 kJ/mol，对叔丁基杯［6］芳烃脱叔丁基过程的化学反应活化能分别为223.56 kJ/mol和240.97 kJ/mol；依据Coats?Redfern方法求出杯［6］芳烃热解机理函数为g（α）=［-ln（1-α）］^2/5，反应级数n=2/5，对应非等温热解机理为随机成核和随后生长反应，对叔丁基杯［6］芳烃脱叔丁基过程的热解机理函数为g（α）=［-ln（1-α）］^1/2，反应级数n=1/2，对应非等温热解机理为随机成核和随后生长反应。     

腐殖酸热分解动力学

采用热重分析法（DTA-TGA）研究了腐殖酸的热分解过程及其动力学,分析其DTA-TGA曲线可得：热分解反应发生在284.65～417.16℃; 用红外光谱（FT-IR）、核磁氢谱（¹H NMR）、核磁碳谱（¹³C NMR）对腐殖酸结构进行表征,用Flynn-Wall-Ozawa（F-W-O）法、Kissinger法及Šatava-Šesták法计算出腐殖酸热分解反应的表观活化能为210.83 kJ·mol^-1,指前因子对数为17.55;确定了其热分解反应的级数和动力学参数,且热分解反应机理为二级反应;腐殖酸在氮气氛围下维持1min寿命的最高使用温度为278℃;同时,计算出腐殖酸样品热力学参数焓变、熵变及摩尔自由能变分别为67.99 kJ·mol^-1、-164.83 J·（mol·K）^-1 和176.36 kJ·mol^-1。     

α-萘乙酸的非等温动力学研究

对α-萘乙酸(C_(12)H_(10)O_2)的热分解机理进行了研究,采用TG曲线确定了它的热分解过程,并通过四种方程对其热分解过程的活化能En进行了计算,利用41种不同的机理方程af)((微分机理方程)和G(α)(积分机理方程),对其热分解过程的非等温动力学数据进行了线性回归处理,并推断出其热分解机理为n=1/4的化学反应机理,最可几函数为4/3af-=)1(4)(a,并建立了其动力学方程。     

杯［4］芳烃的热分解动力学研究

通过热失重分析法（TG）研究了杯［4］芳烃与对叔丁基杯［4］芳烃在氮气氛围下的热稳定性,利用Kissinger方法和Flynn?Wall?Ozawa方法分析计算二者的热解表观活化能,通过Coats?Redfern方法确定了热分解动力学机理与模型,并分别求出了材料主降解阶段的非等温动力学方程。结果表明,Kissinger和Flynn?Wall?Ozawa方法求得的杯［4］芳烃的表观活化能分别为166.64 kJ/mol和175.79 kJ/mol,求得的对叔丁基杯［4］芳烃脱叔丁基过程的表观活化能分别为153.97 kJ/mol和166.81 kJ/mol,其自身苯环热分解过程的表观活化能分别为248.38 kJ/mol和252.92 kJ/mol,两物质的热性能在氮气氛围下都表现得较为稳定,且分解温度对于高分子材料的适应性较强;杯［4］芳烃热分解机理函数为g（α）=［-ln（1-α）］^3/2,反应级数n=3/2,其非等温热分解机理属于随机成核和随后生长反应,对叔丁基杯［4］芳烃脱叔丁基过程的热分解机理函数为g（α）=［-ln（1-α）］^2/3,反应级数n=2/3,其非等温热分解机理属于随机成核和随后增长反应,自身苯环热分解过程的热分解机理函数为g（α）=α²,反应级数n=2,其非等温热分解机理属于一维扩散反应。     

乌头碱的热解及半衰期研究

采用微量热技术及热重法，结合液质联用技术，探讨了乌头碱的热降解机理、水解机理的热效应等，求出乌头碱的半衰期。结果表明，乌头碱在空气氛围中不稳定，碱性溶液中易水解t_1/2=0.973 h。空气环境中热分解分3步，其分解温度区间分别为185～213℃，248～468℃和484～579℃。相应的反应级数分别为n=1/4、n=4、n=2。对应的活化能分别是154.53，100.97和120.08 kJ·mol^-1。乌头碱应尽可能储存于低温干燥并隔绝空气的环境中。     

2-巯基吡啶镉(Ⅱ)、汞(Ⅱ)配合物的热分解动力学研究

采用TG-DTG技术研究了2-巯基吡啶镉(Ⅱ)、汞(Ⅱ)配合物在氮气气氛中的热分解机理及非等温动力学。采用积分法(Coats-Refern方程,HM方程,MKN方程)和微分法(Achar方程)对非等温动力学数据进行了分析,得到了配合物第一步热分解反应的机理函数、动力学参数和热分解动力学方程。结果表明:其热分解过程属F2(化学反应)机理控制,非等温热分解的动力学方程为dα/dT=A/β.e-E/RT(1-α)2,其中镉(Ⅱ)配合物的表观活化能E=86.35 kJ/mol,指前因子A=4.72×107s-1;汞(Ⅱ)配合物的表观活化能E=189.67 kJ/mol,指前因子A=3.79×1018s-1。     

Non-Isothermal Decomposition Kinetics of Alkaline Earth Metal Carbonates

The kinetics of thermal decomposition of four synthetic alkaline earth metal carbonates (MgCO₃, CaCO₃, SrCO₃, and BaCO₃) was studied under non-isothermal conditions using thermo-gravimetry. The activation energy and the pre-exponential factor for the decomposition reactions were determined using the Agarwal and Sivasubramanium integral approximation method. A new method was developed using a Turbo-C-based computer program to evaluate the integral of the kinetic equation. It was observed that the decomposition reaction of MgCO₃ and CaCO₃ followed two-dimensional diffusion-controlled kinetics and the decomposition reaction of SrCO₃ and BaCO₃ followed a Ginstling–Brounshtein model-based diffusion-controlled kinetics.     

Stability Diagram for the System Yba2Cu3O7–x

The dependence of the degree of nonstoichiometry of YBa₂Cu₃0_7–x (123) on temperature and oxygen pressure has been determined by thermogravimetric analysis (TGA) in the temperature range 400° to 950°C and the oxygen pressure range 10^–6 to 1 atm (1 atm = 10⁵ Pa). The nature of the decomposition of 123 in the temperature range 750° to 950°C and the oxygen pressure range 10^–6 to 10^–2 atm has been determined by TGA and X-ray diffractometry (XRD). As the oxygen pressure decreases, the decomposition of 123 follows the sequence 123→ Y₂BaCuo₅ (211) + BaCuO₂° Cu₂O→ 211 ° BaCuO₂° BaCu₂O₂→ 211 ° YBa₃Cu₂O_x (132) ° BaCu₂O₂→ 211 ° BaCu₂O₂°BaO. The incongruent melting temperatures have been determined in the oxygen pressure range 10^–6 to 1 atm by differential thermal analysis, and the phases formed on solidification have been identified by XRD. The stability diagram for the composition 123 has been constructed.     

Mechanistic study of organic template removal from ZSM-5 precursors

The decomposition mechanism of tetrapropylammonium (TPA⁺) template cations in several commercial ZSM-5 precursors was studied by temperature-programmed desorption/oxidation using a mass spectrometer (TPD/TPO-MS). Different oxygen concentrations, gas flow rates and temperature ramp rates were examined to understand the effects of these factors on the organic template decomposition. The TPA⁺ template decomposition pattern is strongly dependent on the SiO₂/Al₂O₃ molar ratio (SAR) and the oxygen concentration. The TPA⁺ template cations may be associated with three different sites depending on the SAR: Lewis acid sites (surface Al–O⁻), Brønsted acid sites (framework Al–O⁻), and weakly acidic Si---O⁻ sites. The thermal decomposition of TPA⁺ templates at different sites produced different products, including water, ammonia, propylene, ethylene, methane, and n- and iso-propylamines. However, no significant heavy volatile compounds were detected, suggesting that secondary reactions (e.g., oligomerization of olefins) were extremely limited and negligible in a fixed-bed micro-reactor used for TPD/TPO. The TPD-MS results suggest that the thermal decomposition mechanism on Lewis acid sites is possibly a free radical type of reaction, while on Brønsted acid sites and Si---O⁻ sites, the decomposition undergoes both Hoffman elimination reaction and a radical type of reaction. The presence of oxygen significantly lowered the TPA⁺ decomposition temperature, which is also a function of oxygen concentration. The knowledge about the template decomposition pattern and the composition of the evolved volatiles obtained by the TPD/TPO-MS technique may be used to develop ideal organic template removal procedures for zeolites.     

On the Decomposition of Synthetic Gibbsite Studied by Neutron Thermodiffractometry

The thermal decomposition mechanism of synthetic Al(OH)₃ (gibbsite) was studied in situ by neutron thermodiffractometry in an ambient atmosphere from room temperature to 600°C with 50°C steps. Gibbsite decomposed to yield AlO·(OH) (boehmite) and then poorly crystallized χ-Al₂O₃. Rietveld analysis was used to refine the cell parameters' variation of gibbsite and its thermal expansion coefficients were obtained: for the a -axis: 15±1 × 10⁻⁶ K⁻¹, for b : 10±2 × 10⁻⁶ K⁻¹, and for c : 17±2 × 10⁻⁶ K⁻¹.     

燃气管用PE100级混配料的热分解动力学和机理

采用热重分析法测定了在氮气气氛中2、5、10、20 ℃/min 4种不同升温速率下的燃气用PE100级混配料热分解过程。采用Kissinger法、Flynn-Wall-Ozawa方法和Coats-Redfern法考察了燃气用PE100级混配料热分解动力学和机理。运用Toop法对PE100级混配料在不同温度下的寿命进行了评估。结果表明,PE100级混配料的热失重为一步分解反应;Kissinger 法求得热分解平均活化能（E）为327.8 kJ/mol,Flynn-Wall-Ozawa法求得的E为304.6 kJ/mol,表观指前因子（lnA）值为53.9 min^-1;在12种常见热分解模型中,R2即圆柱对称的收缩机制最适合描述PE100级混配料热分解反应过程;50 ℃下,Kissinger 法和Flynn-Wall-Ozawa法求得的PE100级混配料寿命分别为7.4×10⁸年和7.9×10⁷年,随着温度的升高,寿命急速降低。     

Kinetics of thermal decomposition of hydromagnesite

The thermal decomposition of hydromagnesite has been studied using thermogravimetric analysis. The experiments were conducted in a nitrogen atmosphere with pellets of hydromagnesite in the temperature range 300 to 550°C, and also with powder samples under non-isothermal conditions at a heating rate of 10°C/min. It is found that the reaction proceeds in two stages: dehydration followed by decomposition. The dehydration reaction is controlled by external mass transfer whilst the decomposition reaction is controlled by both external and internal mass transfer. The activation energy for the dehydration reaction was found to be 2.67 × 10⁷ J/kmol. From the non-isothermal analysis the activation energy for the decomposition of magnesium carbonate was found to be 1.62 × 10⁸ J/kmol.     

High-Temperature Thermal Expansion and Stability of V2AlC Up To 950°C

Herein, we report on the thermal expansion and stability of V₂AlC in the 25°–950°C temperature range. The sample was heated in an Argon atmosphere in a quartz capillary and the thermal expansion was measured using a X-ray synchrotron radiation source. Up to the maximum temperature explored, there were no signs of decomposition or phase transitions. The temperature variation of volumetric thermal expansion is given by α_v=2.53(5) × 10⁻⁵+5.75(3) × 10⁻⁹ T °C⁻¹. At ≈9.40 × 10⁻⁶°C⁻¹, the thermal expansions along both the a and c lattice directions are quite comparable; in other words, there is little thermal expansion anisotropy in V₂AlC.     

Kinetics of calcium carbonate decomposition

Experiments on thermal decomposition of calcium carbonate were carried out in a thermogravimetric analyser under non-isothermal conditions of different heating rates (10 to 100°C/ min). A new technique for determining the kinetic parameters from non- isothermal thermogravimetric data was described. The activation energy and frequency factors were determined from the proposed method and also by the widely used Coats and Redfern method. The kinetic compensation effect between the activation energy and frequency factors obtained from both the methods were found to be very consistent and are in very good agreement with the literature values. The activation energy and frequency factors were also determined from isothermal experiments in the temperature range from 680 to 875°C. The activation energy and frequency factors determined from isothermal data using initial rate method were also found to be in very good agreement with the above results. It is also found that the kinetic parameters determined by isothermal analysis were consistent with the values determined by non-isothermal analysis.     

Synthesis of a novel super-microporous layered material and its catalytic application in the vapor-phase Beckmann rearrangement of cyclohexanone oxime

A novel well-ordered super-microporous layered material, silica-pillared niobic acid, was synthesized by a guest-exchange route and structurally characterized by powder X-ray diffraction (XRD), infrared absorption spectroscopy (IR), thermogravimetric and differential thermal analysis (TG/DTA), transmission electron micrographs (TEM), nitrogen adsorption method and ammonia-temperature-programmed desorption (NH₃-TPD). The obtained silica-pillared layered niobic acid had a supergallery of 1.78 nm, a large BET surface area of 250 m² g⁻¹, and a high thermal stability exceeding 973 K.The pillared layered material was also found to be an efficient solid acid catalyst for the vapor-phase Beckmann rearrangement of cyclohexanone oxime. When 1-hexanol was fed with cyclohexanone oxime, this solid catalyst exhibited a 100% conversion of the oxime with a selectivity of ε-caprolactam beyond 85% at a reaction temperature of 613 K and a WHSV of 0.17 h⁻¹ in terms of cyclohexanone oxime, and there was no significant change of the conversion and selectivity within 6 h.     

不同粒径的α-Fe_2O_3对KClO_3热分解催化性能的研究

通过热重分析法研究了微米Fe2O3和纳米Fe2O3对KClO3热分解的催化性能,用非等温热分析方法研究了纯KClO3、微米Fe2O3催化的和纳米Fe2O3催化的KClO3热分解机理。结果表明,微米Fe2O3和纳米Fe2O3对KClO3热分解均有催化作用,纳米Fe2O3的催化性能比微米Fe2O3的催化性能好,纯KClO3热分解由一维扩散动力学机理控制,活化能E=177.9 kJ/mol,指前因子A=6.3×107;微米Fe2O3催化的KClO3热分解,由三维扩散动力学机理控制,活化能E=118.0 kJ/mol,指前因子A=9.7×105;纳米Fe2O3催化的KClO3热分解,由二级化学反应动力学机理控制,活化能E=68.7 kJ/mol,指前因子A=6.2×104。     

溴化环氧树脂协同三氧化二锑阻燃PBT热分解动力学研究

利用热重分析法研究了聚对苯二甲酸丁二醇酯(PBT)及溴化环氧树脂(BER)协同三氧化二锑(Sb2O3)阻燃PBT在不同升温速率下的热稳定性及热分解动力学;采用Kissinger及Flynn-Wall-Ozawa方法计算出了PBT和阻燃PBT的热分解活化能;利用Coats-Redfern方法确定了PBT和阻燃PBT的热分解动力学机理及其模型,得出了聚合物主降解阶段的非等温动力学方程。结果表明:BER协同Sb2O3阻燃体系的添加提高了PBT的阻燃性能;通过Kissinger和FWO法的分析可知,阻燃PBT在主分解阶段的活化能明显提高;PBT的热分解机理函数为g(α)=1-(1-α)1/3,阻燃PBT的热分解机理函数为g(α)=2[(1-α)-1/2-1],反应级数n=1.5。