(514f) Study on the Function of Water in the Mixed Catalytic Oxidation System of Toluene and Chloromethane

In the research, the role of water for the catalysts of Pt-structured supported on anodic alumina was studied in the process of catalytic oxidation of chloromethane and toluene. Chloromethane (235ppm) was added into toluene flow gas (1000ppm) under dry atmosphere and moisture atmosphere respectively. It was found that chloromethane had an inhibition effect on catalytic oxidation of toluene under dry atmosphere, however, the inhibition effect was dismissed under moisture atmosphere. A series of characterizations were performed to analyze the different behavior of catalysts under dry and moisture atmosphere. The results showed that in dry mixed-gas flow, chloromethane occupied a part of active sites and formed  Pt-Cl_xO_y on the anodic alumina, which decreased the possibility of toluene being adsorbed. When water existed in the mixed-gas flow, the adding of chloromethane had no effect on toluene catalytic oxidation. It is because that water can improve the first-step reaction of chloromethane oxidation(Eq.(1)) and then the conversion of chloromethane completely were followed quickly. Moreover, water can carry part of chloromethane off because of excellent water-resistance of Pt catalysts prepared using competitive impregnation method, which decreased the adsorption of chloromethane.

                                                                              2CH₂Cl₂ + H₂O → CO + CH₃Cl + 3HCl                                      (1)