Kiwi twig biochar recycling promoting the reduction of NO by a MnO2 catalyst

Abstract

Kiwi twigs have abundant vessels and sieve tubes, which may provide abundant nanotube structures and active sites. In this study, kiwi twig biochar was used to modify the α-manganese dioxide (MnO2) catalyst through facile potassium hydroxide solution (KOH) activation to improve N2 selectivity in selective catalytic reduction (SCR). Results suggested that the C10.5MnO2 catalyst exhibited higher NO conversion (approximately 90%) and N2 selectivity (>95%) at 100 °C–250 °C. Moreover, biochar C1, which was directly mixed with KOH, increased the number of acid sites and lattice defects in the C10.5MnO2 catalyst; thus, the redox and acid cycles more easily occurred on the surface of the C10.5MnO2 catalyst than on that of the C20.5MnO2 catalyst. Moreover, the SCR process of the modified catalysts involved both Langmuir–Hinshelwood and Eley–Rideal mechanisms. This study demonstrated the effect of biochar on reaction sites and processes, providing a new perspective for the application of biochar in the field of catalysis.