Cordierite and citric acid regulate crystal structure of manganese oxide for effective selective catalytic reduction of nitrogen oxide

Catalyst is the key to effective selective catalytic reduction of nitrogen oxide, and developing catalyst is always one of the hottest topics in both field of industry and academy. In order to realize an industrial application, one catalyst must grow on a specific support. However, seldom work compared the difference of catalyst growth with or without support. In this work, Mn2+ growth on cordierite (a typical commercial catalyst support) was investigated. The formed active species were detailedly characterized. As a result, orthorhombic cordierite guided Mn2+ to form orthorhombic oxide (gamma-MnO2). In comparison, Mn2+ preferred to form tetragonal beta-MnO2 without the guide of cordierite. During the synthesis, cordierite and citric acid promoted gamma-MnO2 dispersion, increased growth of exposed (301) facet, and created lattice distortion between (301) and (101) planes. beta-MnO2 mainly exposed (101) facet. The best catalyst was gamma-MnO2, which was mostly dominated by (301) facet and had an obvious lattice distortion from 75 degrees to 78 degrees between (301) and (101) planes. In comparison, 0.1 g of the gamma-MnO2 reached a catalytic conversion rate 1.6 times bigger than 1.0 g of beta-MnO2 at 250 degrees C. This work helps to un-derstand guiding effect of support on formed catalytic species, which is in favor of developing effective com-mercial catalysts for environmental pollutants.

Automated summary

This study investigates the effect of cordierite on the growth of Mn2+. It is found that cordierite guides Mn2+ to form orthorhombic oxide while in its absence, Mn2+ tends to form tetragonal oxide.