Oxidative reforming of diesel fuel over LaCoO3 perovskite derived catalysts: Influence of perovskite synthesis method on catalyst properties and performance

Oxidative reforming of diesel fuel was studied over Co/La2O3 catalysts derived from LaCoO3 perovskite precursors synthesized by co-precipitation (COP), sol–gel (PEC) and combustion (SCS) methods. Physical–chemical characterization of perovskite precursors by N2-adsorption isotherms, Hg-intrusion porosimetry, XRD, XPS, TPR and SEM showed that the method of preparation produced changes in the porosity and homogeneity both at bulk and surface levels of the LaCoO3 perovskite precursors. The perovskite prepared by the SCS method achieved a higher development of the porous network as well as higher homogeneity in bulk and surface compared to COP and PEC counterparts. By contrast, the PEC and COP methods produced perovskites with lower porosity and with the presence of some secondary phases such as Co3O4 and La(OH)3. The modifications of the characteristics of LaCoO3 perovskites directly affected the structure and morphology of the catalytic materials derived from the thermal pre-treatment of perovskites before the activity tests. The differences in catalyst characteristics resulted from a different reduction and interaction between the gaseous reducing stream and the initial LaCoO3 perovskites which occurred during the thermal pre-treatment. The activity of the samples at the beginning of the reaction test followed the order: PEC > SCS > COP. The latter could be related to the different interaction of the catalysts with the reactants as well as with the larger presence of the La2CoO4 phase produced during the thermal pre-treatment. The evolution of the catalysts for long times on stream resulted in the activity order: SCS > PEC > COP. Characterization of used samples disclosed the key role of the Co0 exposure on the catalyst surface as concerns the achieved catalytic activities and the extent of the La2O2CO3 phase on catalysts as regards the inhibition of coke deposition.

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► Different physicochemical properties of LaCoO3 catalyst precursors depending on the synthesis method.
► Physicochemical properties of LaCoO3 precursors affect the structure of the catalysts derived after thermal reduction.
► Higher initial activity in diesel reforming on catalysts with La2CoO4 after thermal reduction of LaCoO3.
► Long-term activity depends on the extension of Co0 and La2O2CO3 phases developed under reaction.