Effect of polyethylene glycol addition on Cu-Mn-Ce-Ox/TiO2/CH catalyst in microwave catalytic combustion of toluene

Adding polyethylene glycol (PEG) can lessen the shedding of coating and improve the dispersion of active particles for monolithic catalysts. In this study, a series of Cu-Mn-Ce-O_x(P_x)/TiO₂(P_x)/CH catalysts were prepared with different PEG molecular weights (P_x, x = 200, 1000, and 2000) to explore the effect of P_x addition on the structure and activity of the catalysts in microwave catalytic combustion of toluene. The research showed that P_x addition (1 wt% dosage to titanium sol) to coating reduced the particle size of titanium sol and decreased the shedding rate of TiO₂ coating 0.9–0.93 %, and P_x addition (3 wt% dosage to CH's water absorption) to active components further lessened the shedding rate of the catalysts 1.93–2.04 %. Under an initial toluene concentration of 1500 mg/m³ and a gas hourly space velocity of 2260 h⁻¹, Cu-Mn-Ce-O_x(P₁₀₀₀)/TiO₂(P₁₀₀₀)/CH owned the highest catalytic activity and its complete removal temperature (T_R100) and mineralization temperature (T_M100) to toluene were 180℃ and 218℃, respectively, which were lower 33℃ and 16℃, 56℃ and 58℃ than Cu-Mn-Ce-O_x/TiO₂(P₁₀₀₀)/CH and Cu-Mn-Ce-O_x/TiO₂/CH catalysts separately, and its activity maintained steadily with toluene removal efficiencies of 99–91 % over 12 h. The improved activity is attributed to the uniform dispersion of active particles, larger specific surface area, and increased adsorbed oxygen, facilitated by pore-forming and steric-hindrance effects of P_x. Electron transfer among Mn⁴⁺/Mn³⁺/Mn²⁺, Cu²⁺/Cu⁺, and Ce⁴⁺/Ce³⁺ promoted the oxidation of toluene under microwave irradiation. Therefore, the research provides technological support for developing transition metals-based catalysts for industrial VOC waste gas treatment.