Mn/Co Redox Cycle Promoted Catalytic Performance of Mesoporous SiO₂‐Confined Highly Dispersed LaMn_xCo_1‐xO₃ Perovskite Oxides in n‐Butylamine Combustion

Abstract

In this study, highly‐dispersed perovskite‐type oxides LaMnxCo1‐xO3 supported on mesoporous SiO2 (LMxC1‐xO/SiO2) were synthesized by a citric acid‐assisted deposition method. For LMxC1‐xO/SiO2 catalysts, the double B‐site transition metal ions can not only significantly arise the surface defects, but also lead to the formation of (Mn3++Co3+)/(Co2++Mn4+) redox cycle, both of which were able to improve the catalytic performance of LMxC1‐xO/SiO2 in n‐butylamine combustion. Strikingly, LM0.2C0.8O/SiO2 catalyst showed the optimum catalytic performance (T90%=210 °C at a space velocity of 15,000 mL gcat−1 h−1) and the lowest NOx yield among the LMxC1‐xO/SiO2 samples, which could be greatly assigned to the accelerated activation and circulation of the oxygen species initiated by the surface defects and redox cycle.

Influence of the Thermal Processing and Doping on LaMnO3 and La0.8A0.2MnO3 (A = Ca, Sr, Ba) Perovskites Prepared by Auto-Combustion for Removal of VOCs

“…For all the studied samples, two reduction stages are observed in the TPR profile, one below 600 • C and the other at around 800 • C. Owing to the fact that La 3+ , Sr 2+ , Ca 2+ and Ba 2+ are not reducible under the measurement conditions, the water production is due to the reduction of manganese. According to the literature [38][39][40], the H 2 consumption below 600 • C corresponds to the reduction of Mn 4+ to Mn 3+ while that observed at high temperature it is attributed to the reduction of Mn 3+ to Mn 2+ (which will not be discussed because it is beyond the temperature range considered for the reaction conducted under oxidizing conditions in this work). Then, based on the first reduction process (Table 2), it is possible to obtain the Mn 4+ content of the perovskite being the 100% of Mn 4+ equal to 1/2 mol H 2 mol −1 cat.…”