Microwave synthesis of nanocrystalline LaCoO3 samples and their catalytic activity towards decomposition of isopropanol

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.