Manganese has high oxygen storage capacity and strong reducibility, so it is widely used as a catalyst for catalytic oxidation of volatile organic compounds (VOCs) such as benzene, toluene, formaldehyde, and other environmental pollutants.manganese catalyst The most promising transition metal oxide catalysts for VOCs are manganese-based catalysts due to their superior oxygen storage and release efficiency.
The structure and the chemical state of manganese determine its catalytic performance.manganese catalyst Therefore, the structural optimization of manganese-based catalysts can greatly improve their stability and activity. It can be achieved through the structural design, decorating modification and defect engineering.
Structural optimization of manganese-based catalysts is a key process for the development of efficient VOCs catalytic degradation catalysts.manganese catalyst It includes the improvement of the specific surface area, increasing the number of active sites, and decorating with other metal ions to improve the catalytic performance. In addition, defect engineering can help to regulate the electronic structure of manganese-based materials and enhance the catalytic activity by introducing different molecular structures.
To date, a series of manganese-based catalysts have been developed for VOCs catalytic degradation.manganese catalyst These include mesoporous manganese oxides (Mn3O4, Mn2O3, and MnxOy), manganese dioxide (MnO2), and Fe-Mn perovskite. These catalysts have excellent catalytic activity for the total oxidation of VOCs such as ethylene, propylene, and toluene. They are also suitable for the photocatalytic oxidation of VOCs.
Among the manganese-based catalysts, FeMn has the best performance for oxidation of propane and is more stable than Mn2O3.manganese catalyst It is possible that the high catalytic activity of FeMn is related to the higher Mn-OH bond energy and the more active Mn-OH oxygen vacancy.
The catalytic behavior of various types of FeMn-based oxides is comparable.manganese catalyst However, the activity of CuMn-based catalysts is lower than that of FeMn-based ones. The poor catalytic performance of CuMn-based catalysts is believed to be mainly associated with the aggregation of Mn atoms and the presence of large amounts of impurities.
The characterization of the surface and morphology of XMnOx catalysts was performed by using scanning electron micrographs (SEM). It was found that the morphology and the crystallite size of CuMn-based oxides were more granular than those of CeMn, CoMn, and FeMn-based oxides. The O(1s) spectral analysis showed that the binding energy of oxygen in the XMnOx oxides varied from 529.2-530 eV, which corresponded to surface and lattice oxygen respectively. Moreover, the amount of surface chemisorbed oxygen in the CuMn-based catalysts was significantly higher than that in the other two groups. This is because of the higher degree of interaction between the easily oxidizable manganese phase and highly reducible copper, cobalt and iron phases in the XMnOx oxides. The characterization results suggest that the CuMn-based catalysts have higher activity for CO oxidation than CeMn- and CoMn-based oxides. This is because the high oxidizable oxygen content facilitates the formation of the metastable oxo active species Q-4, which then undergoes either OH rebound to yield an alcohol or the desaturation reaction to produce phenanthrene.
