Preparation of the Mn-Ce-Co-O_x/PPS filter material by a redox method and its activity in the low-temperature selective catalytic reduction of NO_x

A series of Mn-Ce-Co-O_x/PPS composite filter materials with different mass ratios were obtained by modifying the pristine polyphenylene sulfide (PPS) filter material with sodium dodecyl sulfate (SDS) and then treated by a redox precipitation method. The Mn-Ce-Co-O_x/PPS composite filter materials were characterized by XRD, FESEM, TEM and XPS; their catalytic performance in the low-temperature selective catalytic reduction (SCR) of NO_x was then investigated. The results show that the Mn-Ce-Co-O_x/PPS composite filter materials obtained by the redox method presents higher low-temperature SCR activity than the Mn-Ce-Co-O_x/PPS-UM composite filter material fabricated via the ultrasonic method; over the former material, the NO_x conversion reaches 86%-100% at 120-160℃. Among them, the 1.2Mn-Ce-Co-O_x/PPS composite filter material displays the highest SCR activity, which is probably ascribed to the high Ce³⁺/(Ce³⁺+Ce⁴⁺) ratio and high concentration of Co; moreover, honeycomb-like MnO₂, Ce₂O₃, CeO₂, CoO and Co₃O₄ are uniformly distributed on the PPS filter material in the weak crystalline structure. In comparison with Mn-Ce-Co-O_x/PPS-UM, the 1.2Mn-Ce-Co-O_x/PPS composite filter material also exhibits higher resistance to H₂O and SO₂.