The Cerium-Modified MgAl2O4 Spinel and Its Supported PdCu Three-Way Catalyst with Improved Performance

The three-way catalysts (TWC) are required to have high thermal stability and excellent catalytic activity. The MgAl 2 O 4 spinel is a thermal stable material, but its reactivity is unsatisfactory. In this work, CeO 2 was used as a promoter to modify MgAl 2 O 4 spinel, and the cerium modified MgAl 2 O 4 spinel (MAC) was applied as the carrier to construct PdCu/MAC catalyst. The catalytic activity evaluation showed that modifying MgAl 2 O 4 spinel with a handful of cerium (0.12 mol-Ce/mol-Mg) dramatically improved the three-way catalytic activity, especially for the elimination of NO x and C 3 H 8 . The XRD and XPS proved that these cerium cations incorporated into spinel lattices and occupied Al sites. For this reason, the cerium in PdCu/MAC-1 is mainly in +3 valence (Ce 3+ /Ce = 60.2%), which is accompanied by the formation of abundant oxygen vacancies (45.9%). These factors significantly promoted the dispersion of PdCu nanoparticles, and thus strengthened metal-support interaction, consequently the enhanced catalytic performance. However, adding excessive cerium (0.24 mol-Ce/mol-Mg) resulted in negative effect. This might be related to the appearance of isolated CeO 2 crystal originating from the separate nucleation of excessive cerium cations. This work provides some guidance for developing TWC with both high thermal stability and activity.