Influence of the strategy for mixing Pd/La-Al2O3 and Pd/Ce0.5Zr0.5O2 on the activity of three-way catalysts

As the two main components in typical three-way catalysts, Pd-Al2O3 and Pd-Ce0.5Zr0.5O2 usually show different Pd-support interaction strength. Thus, Pd could re-distribute between Al2O3 and Ce0.5Zr0.5O2 upon heating. Here the strategy to mix Pd/La-Al2O3 and Pd/Ce0.5Zr0.5O2 (before or after calcination, or after aging) was researched. The optimal choice was mixing-calcination-aging , offering the highest oxygen storage capacity, Pd dispersion and catalytic activity for CO and C3H6 elimination during the three-way catalytic reaction. Thus, the mixing-calcination-aging strategy holds promise in industrial applications, as demonstrated at the monolith converter level. The transient drop in conversion with increasing temperature ( kink ) appeared simultaneously for CO, NO and C3H6 over the mixing-calcination-aging monolith, but did not over the calcined counterpart mixing-calcination . The kinks disappeared for the used mixing-calcination-aging , but could be restored upon re-oxidizing. By virtue of the in situ Raman characterization, the reduction of PdO under the reaction conditions was found to cause the kinks.

Automated summary

The mixing-calcination-aging strategy can enhance the catalytic performance and oxygen storage capacity of three-way catalysts, but it leads to a transient drop in conversion rate, which is caused by the reduction of PdO.