Comparison of Selective Catalytic Reduction Performance of Mn–Co Bi‐Metal Oxides Prepared by Different Methods

Abstract

In this work, the low dimensional flake Mn 4 Co 1 O x composite oxides were prepared by four different methods (hydrothermal, template, co-precipitation and one-step, noted as HS, TM, OP and OS, respectively) and used for the ammonia selective catalytic reduction (NH 3-SCR) at low temperatures. The results showed that the activity of the catalysts decreased in the sequence: Mn 4 Co 1 O x-HS > Mn 4 Co 1 O x-TM > Mn 4 Co 1 O x-OP > Mn 4 Co 1 O x-OS. The activity of the best catalyst (Mn 4 Co 1 O x-HS) was nearly 100 % NO conversion in the temperature range of 75-250°C and the N 2 selectivity remained above 50 % even at 250°C. Mn 4 Co 1 O x-TM catalyst also maintained the NO conversion more than 90 % in the range of 100-250°C, but the N 2 selectivity was poor. The catalytic activity of the other two catalysts was slightly lower than the above two catalysts. Based on the comprehensive characterization, it was found that the Mn 4 Co 1 O x-HS catalyst had a higher NH 3 adsorption and activation capacity, which was attributed to the higher surface area caused by its approximately two-dimensional folded layered structure leading to more active sites. Meanwhile, it was rich in the surface acid sites, Mn 3 + , Co 3 + and surface oxygen in the MnÀ Co spinel structure, thus giving strong acidity and good redox capacity.