Reactive Grinding synthesis of La(Sr,Ce)CoO₃ and their properties in toluene catalytic total oxidation

Abstract

Perovskites-type metal oxides are an attractive alternative to noble metal-based materials for environmental catalysis. Nevertheless, they suffer from major issues such as unattractive textural properties and lower intrinsic activities than those of noble metal counterparts. Reactive grinding (RG) has been already proved to be a powerful method to produce materials with improved textural properties. La 1-x A' x CoO 3 (A': Sr, Ce) perovskite-type materials were synthesized by RG synthesis as a 3-steps top down method: (i) conventional solid-state reaction -SSR (leading to microcrystalline material); (ii) high energy ball milling -HEBM and (iii) low energy ball milling -LEBM. The physicochemical properties of perovskite materials were inves-tigated by XRD, N 2 -physisorption, H 2 -TPR, O 2 -TPD and XPS, while their catalytic performances were evaluated for the toluene total oxidation reaction. In this study we showed that the HEBM step leads in a drastic reduction in crystal size to nanometric scale along with aggregation into dense particles. The LEBM step allows the deagglomeration of particles and specific surface areas were significantly increased. Their performances in the toluene total oxidation increased along grinding steps and a maximum of catalytic performance was observed for La 0.9 Sr 0.1 CoO 3 . This material also exhibited a high catalytic stability as a function of the reaction time, under dry and wet air reaction conditions.

Thermally Inducing Viscous Fluids to Generate Co-Based Perovskites Enriched with Active Species for the Removal of VOCs

“…As shown in Figure b, the E a values for VOC oxidation followed the order of LaCoO 3 < SmCoO 3 < GdCoO 3 , suggesting that LaCoO 3 had the highest concentration of surface-active species, which led to the greater susceptibility of VOC to oxidation over LaCoO 3 . Furthermore, the E a values over LaCoO 3 (52.4 kJ·mol –1 ), SmCoO 3 (60.1 kJ·mol –1 ), and GdCoO 3 (66.7 kJ·mol –1 ) were also significantly lower than those of LaMnO 3 (84.0 kJ·mol –1 ), LaCoO 3 (173.0 kJ·mol –1 ), Eu 0.6 Sr 0.4 FeO 3 (78.8.0 kJ·mol –1 ), and La 0.6 Sr 0.4 Fe 0.8 Bi 0.2 O 3‑δ (127.7 kJ·mol –1 ), Cu 1.5 Mn 1.5 O 4 (111.2 kJ·mol –1 ), MnO/CeO 2 (>127.6 kJ·mol –1 ), MnO x /Al 2 O 3 (133.0 kJ·mol –1 ), and Ni 0.5 Zn 0.5 Fe 2 O 4 (94 kJ·mol –1 ) . In general, the activity of catalysts is determined by their structures, metal states, and redox properties, which can be improved through optimized preparation methods. , Therefore, we attribute the difference in E a values between RECoO 3 and the literature values to the high concentration of surface-active species in RECoO 3 , obtained through direct calcination of the viscous mixture.…”

Roles of the A-Site Ca Dopant in Modifying Surface Properties of a Co-Based Perovskite Catalyst for Selective Oxidation of Cyclohexane

“…are regarded as inert in catalysis and act as a rigid structural element in the crystal of perovskite oxides, while the B-site transition metal elements (e.g., Co, Mn, Fe, etc.) are mainly responsible for catalytic activity. , However, it should be noticed that the valence states of B-site redox elements and the crystal structure in perovskite oxides can be effectively altered by doping with both of A/B-site elements, which will also trigger the formation of abundant oxygen vacancies and lead to enhancement of oxygen mobility. − In previous studies, the low-valence elements (such as K, Sr, Ca, Co, Ni, and Cu) were usually applied to dope into the A/B-sites of various perovskite oxides to further improve their catalytic activity. − For example, Zhao et al reported the effect of different doping contents of Co 2+ in the B-site of LaFeO 3 on chemical looping steam methane reforming. They found that the substitution of Fe with an appropriate content of Co could promote the generation of oxygen vacancies, improve the reducibility of LaFe 1– x Co x O 3 , and change the types of oxygen species, which eventually facilitated the partial oxidation of methane, inhibited the direct decomposition of methane, and produced more hydrogen in chemical looping methane reforming.…”

Promotion of Low‐Temperature Oxidation of Propane through Introduction of Ce into Mullite Oxide YMn2O5

“…Catalytic oxidation is regarded as one of the promising approaches to control the emission of VOCs due to its high efficiency. [8][9][10] The catalysts for VOCs removal are usually included supported noble metals (i. e. Pt, Pd and Rh) and transition metal oxides (Mn, Cu, Co, Cr and Ce). Compared with noble metal catalysts, transition-metal oxides are attractive due to their low cost, high thermal stability and promising activity.…”