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

Abstract

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.