A sulfur dioxide (SO2)-tolerant, stable mixed oxide as an alternative to platinum (Pt) group metal (PGM) catalysts has been explored for the catalytic oxidation of particulate matter (PM) due to its low-cost, desirable physiochemical properties, thermal stability, tailoring options, etc. Herein, a mixed oxide of Sr and Cr was prepared via a solution combustion method by mixing stoichiometric amounts of Sr- and Cr-precursors with citric acid and urea as fuels followed by calcination at 800 °C in air. A pure mixed oxide phase of Sr and Cr (SrCrO4) (P21/n ) (a = 0.7090 nm, b = 0.7394 nm, and c = 0.6755 nm) has been successfully prepared, and the SrCrO4 particles are larger in size with semi-oval shapes due to their agglomeration at elevated temperatures. The SrCrO4 catalyst shows significantly improved intrinsic catalytic performance for PM oxidation in the tested temperature range as compared to the reference catalysts, Pt/Al2O3 and Pt-dispersed SrCrO4 (Pt/SrCrO4) (loading weight: 5 wt%) are used as internal reference catalysts. The onset temperature (i.e., intrinsic catalytic activity at 10% conversion, T10) is observed at 426 °C, which is significantly lower than that of the reference Pt/Al2O3 (T10 = 537 °C) and comparable with that of the Pt/SrCrO4 catalyst (T10 = 414 °C). The SrCrO4 catalyst shows a stable, multi-cycle PM oxidation performance for the tested five cycles, and both its crystalline structure and morphology remain unchanged even after its multiple cycles of use. The structure of the SrCrO4 catalyst is stable even after moisture and SO2 treatments, and the catalytic PM oxidation activity of SrCrO4 is not compromised even after these harsh treatments. Importantly, the SrCrO4 catalyst is also stable after PM oxidation conducted using real world PM from a heavy-duty vehicle. These results demonstrate that the mixed oxide phase of SrCrO4 shows promise for PM oxidation.
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