Effect of Na⁺ on catalytic performance of CoCe/ZSM-5 catalysts for oxidation of toluene

A CoCe/ZSM-5 catalyst was prepared by ultrasonic-assisted impregnation for the catalytic combustion of toluene. To study the effect of Na⁺ on catalytic performance of CoCe/ZSM-5 catalysts, a series of different Si/Al ZSM-5 zeolites and catalysts doped with Na were synthesized. The experimental results show that 0.71 wt% Na⁺ can inhibit active growth, generate more active small crystal grains, and promote improvement of the catalytic activity by the grain boundary segregation block mechanism, and the catalyst with 0.71 wt% of Na shows toluene conversion of 90 vol% at 250 °C. Over 0.71 wt% of Na⁺ content will neutralize the acid centre of the catalyst, lowering the specific surface area of the catalyst and resulting in a gradual decrease in the catalytic activity.