Insight into the effect of oxygen species and Mn chemical valence over MnOx on the catalytic oxidation of toluene

Abstract

A series of MnOx were prepared with four different precipitants and employed to catalyze the combustion of toluene with the aim to clarify the role of Mn3+, Mn4+, surface adsorbed oxygen and lattice oxygen. Lower crystallinities and better microstructures were observed on the catalysts prepared by carbonates, due to the lower nucleation rates. The co-existence of Mn3+ and Mn4+ was beneficial to the transfer and transformation of electrons, which promoted the redox performance of catalyst. But various contents of Mn3+ and surface adsorbed oxygen species were found on the catalysts synthesized with different precipitants. By the improving of Mn3+, the binding capacity of the catalyst using (NH4)2CO3 as precipitant (Mn-AC) to oxygen was weakened, thus increasing its oxygen mobility. Furthermore, more oxygen vacancies were produced, resulting in the generation of more active oxygen species on the surface of Mn-AC. Abundant adsorbed oxygen of Mn-AC enhanced the oxidation ability of lattice oxygen by the rapid supplement of consumed lattice oxygen species. Therefore, Mn-AC with excellent catalytic activity and durability is promising industrial catalyst for efficient removal of toluene.