Promotion of toluene catalytic oxidation by M−La/CoOx catalysts directly prepared from Co-MOFs precursors

Volatile organic compounds (VOCs) are identified as volatility and toxicity, and have become major pollutants in the atmosphere. The development of low-energy and high-efficiency environmentally friendly VOCs purification technologies is urgent. Therefore, in this paper, a series of M−La/CoOx (M = La addition) catalysts with different La additions were synthesized by a combination of impregnation and calcination using Co-MOFs as precursors. It was shown that the catalytic activity of the constructed 0.012-La/CoOx catalyst was unexpectedly improved (T90% = 227 °C) under optimal reaction conditions (catalyst mass-air velocity = 60000 mL/(g•h)), initial toluene concentration = 1000 ppm) when employing gaseous toluene (C7H8) as typical target VOCs. Among the La-doping catalysts, the catalysts containing La on the surface have smaller grain sizes as well as more homogeneous grain distributions than the pure Co3O4-MOF catalysts. 0.012-La/CoOx displayed the highest activity, which is attributed to its smaller particle size, larger specific surface area (SSA), richer content of Co3+ and surface Oads, which could enhance the oxygen mobility and the redox performance. The possible degradation mechanism of toluene on 0.012-La/CoOx was revealed using in-situ DRIFTS. This work might provide guidance for the development of efficient and environmentally friendly catalytic oxidation of toluene.