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首页> 外文OA文献 >Non-Isothermal Kinetics and Mechanistic Study of Thermal Decomposition of Light Rare Earth Metal Nitrate Hydrates using Thermogravimetric Analysis
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Non-Isothermal Kinetics and Mechanistic Study of Thermal Decomposition of Light Rare Earth Metal Nitrate Hydrates using Thermogravimetric Analysis

机译：轻稀土金属硝酸盐水合物热解的非等温动力学和机理的热重分析

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摘要

The formation of light rare earth metal oxides such as CeO2, La2O3, Sm2O3, Nd2O3 and Pr2O3 from thermal decomposition of its nitrate precursors (Ce(NO3)3·6H2O, La(NO3)3·6H2O, Sm(NO3)3·6H2O, Nd(NO3)3·6H2O and Pr(NO3)3·6H2O) have been investigated by thermogravimetric analysis. The rare earth metal oxides obtained were characterized for the nature of chemical bonds and textural properties using FTIR and N2-physisorption analyses, respectively. The FTIR analysis of the rare earth metal precursors and the oxides showed that the OH– and NO– bonds depicting the presence of hydrated water molecules and nitrate disappeared after the thermal decomposition leaving out only the pure solid oxides. The kinetics data obtained from the thermogravimetric analysis were fitted into “model free” kinetic expressions such as Kissinger, Ozawa–Flynn–Wall to calculate the apparent activation energy of the solid-state decomposition reaction of the rare earth metal precursors. The kinetic parameters were further analyzed using Coat–Redfern model to determine the possible mechanism of the decomposition process. The calculated values of the activation energy obtained from both Kissinger and Ozawa–Flynn–Wall models were similar compared to that obtained from Coat–Redfern model. Highest activation energies of 230.26, 344.78, 320.2.78, 392.72 and 258.26 kJ mol−1 were obtained from decomposition of Ce(NO3)3·6H2O, La(NO3)3·6H2O, Sm(NO3)3·6H2O, Nd(NO3)3·6H2O and Pr(NO3)3·6H2O), respectively, using Kissinger model, while the analysis of the kinetic data using Ozawa–Flynn–Wall model gave the highest activation energies of 229.01, 350.56, 348.56, 392.72 and 388.56 kJ mol−1 for decomposition of Ce(NO3)3·6H2O, La(NO3)3·6H2O, Sm(NO3)3·6H2O, Nd(NO3)3·6H2O and Pr(NO3)3·6H2O), respectively. Thirteen different models were evaluated using Coat–Redfern models in order to determine the mechanisms that govern the decomposition process. Interestingly, two-dimensional diffusion mechanism with activation energy of 105.61, 107.61, 140.61, 144.52 and 154.78 kJ mol−1 was obtained for thermal decomposition of Ce(NO3)3·6H2O, La(NO3)3·6H2O, Sm(NO3)3·6H2O, Nd(NO3)3·6H2O and Pr(NO3)3·6H2O), respectively. The rare earth metal oxides obtained from this study finds potential application as supports, promoters and catalysts in the field of catalysis.
机译：通过其硝酸盐前体（Ce（NO3）3·6H2O，La（NO3）3·6H2O，Sm（NO3）3·6H2O的热分解形成轻稀土金属氧化物，如CeO2，La2O3，Sm2O3，Nd2O3和Pr2O3通过热重分析研究了Nd（NO3）3·6H2O和Pr（NO3）3·6H2O。分别使用FTIR和N2-物理吸附分析对获得的稀土金属氧化物的化学键性质和结构性质进行了表征。稀土金属前体和氧化物的FTIR分析表明，OH-和NO-键描述了水合水分子和硝酸盐的存在，它们在热分解后消失了，只剩下纯的固体氧化物。从热重分析获得的动力学数据被拟合为“无模型”动力学表达式，如Kissinger，Ozawa-Flynn-Wall，以计算稀土金属前体的固态分解反应的表观活化能。使用Coat–Redfern模型进一步分析了动力学参数，以确定分解过程的可能机理。从基辛格和小泽-弗林-沃尔模型获得的活化能计算值与从科特-雷德芬模型获得的计算值相似。通过Ce（NO3）3·6H2O，La（NO3）3·6H2O，Sm（NO3）3·6H2O，Nd（）的分解获得最高活化能230.26、344.78、320.2.78、392.72和258.26 kJ mol-1使用基辛格模型分别分析NO3）3·6H2O和Pr（NO3）3·6H2O），而使用Ozawa-Flynn-Wall模型对动力学数据进行分析得出的最高活化能为229.01、350.56、348.56、392.72和388.56。用于分解Ce（NO3）3·6H2O，La（NO3）3·6H2O，Sm（NO3）3·6H2O，Nd（NO3）3·6H2O和Pr（NO3）3·6H2O的kJ mol-1。为了确定控制分解过程的机制，使用Coat–Redfern模型评估了13种不同的模型。有趣的是，通过二维扩散机理获得了活化能为105.61、107.61、140.61、144.52和154.78 kJ mol-1的Ce（NO3）3·6H2O，La（NO3）3·6H2O，Sm（NO3）的热分解。 3·6H2O，Nd（NO3）3·6H2O和Pr（NO3）3·6H2O）。从这项研究中获得的稀土金属氧化物在催化领域发现了潜在的载体，助催化剂和催化剂的应用。

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