Abstract

Nanocrystalline LaCoO₃ powders were fabricated via the sol–gel microwave-induced combustion approach using metal nitrates as oxidant and citric acid as fuel. Calcination of the precursor was performed in the temperature range 400–800 °C. The precursor of the LaCoO₃ powder as well as the calcination products were investigated using thermal analysis (TGA and DTA), FTIR, XRD and N₂ adsorption techniques. In a dynamic air atmosphere, calcination was implemented in the temperature range 400–800 °C. XRD patterns show the fabrication of the perovskite rhombohedral phase of LaCoO₃. The average nanoparticle size calculated from the XRD patterns was in the range 8–21 nm. Surface area measurements calculated from the N₂ adsorption isotherms show low surface area values. The porosity of these materials was identified to be microporous in nature. SEM and TEM tests endorsed the findings. Analysis of TGA and DTA showed a sharp exothermic peak of about 358 °C and a steady weight loss of up to about 600 °C. The vapor-phase dehydration/dehydrogenation of isopropanol, in the temperature range 350–425 °C, was adopted to assess the catalytic performance. The activity of the LaMnO₃ catalysts is mainly directed towards the dehydrogenation reaction forming acetone as a main product. The maximum yield was found for the sample calcined at 600 °C. A strong correlation was identified between the selectivity of dehydrogenation and the redox couple species evaluated. A potential reaction mechanism was suggested that would be compatible with the data obtained.

中文翻译：

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纳米晶LaCoO 3样品的微波合成及其对异丙醇分解的催化活性

摘要

纳米晶LaCoO ₃粉末是通过溶胶-凝胶微波诱导的燃烧方法，以金属硝酸盐为氧化剂，柠檬酸为燃料制备的。前体的煅烧是在400-800°C的温度范围内进行的。使用热分析（TGA和DTA），FTIR，XRD和N ₂吸附技术研究了LaCoO ₃粉末的前体以及煅烧产物。在动态空气气氛中，煅烧是在400–800°C的温度范围内进行的。XRD图谱显示了LaCoO ₃的钙钛矿菱面体相的制备。根据XRD图谱计算得出的平均纳米颗粒尺寸为8-21 nm。由N ₂计算得出的表面积测量吸附等温线显示较低的表面积值。这些材料的孔隙率被确定为本质上是微孔的。SEM和TEM测试证明了这一发现。对TGA和DTA的分析显示出约358℃的急剧放热峰和高达约600℃的稳定重量损失。异丙醇在350–425°C的温度范围内进行气相脱水/脱氢，以评估催化性能。LaMnO ₃的活性催化剂主要用于脱氢反应，形成丙酮为主要产物。发现在600°C下煅烧的样品的最大产率。在脱氢的选择性和所评估的氧化还原对物种之间发现了很强的相关性。提出了一种潜在的反应机理，该机理与获得的数据兼容。