Effect of noble metals deposition on the catalytic activity of MAPO-5 catalysts for the reduction of NO by CO Original Research Article

Molecular sieves MAPO-5 (M: Co, Ti, Cr and Fe) with the AFI structure type were prepared by the hydrothermal method. Noble metals (Pd, Rh, Ir and Ru) were deposited on the molecular sieve supports using the homogeneous deposition precipitation method. The catalysts were characterized using XRD, TEM, DRUV-VIS, N2 sorption, SEM, TG/DTA and ICP analysis techniques. The PdO and RhOx species demonstrated small particle sizes as compared with other noble metals. The catalysts were evaluated for their performance in the reduction of NO by CO at different temperatures (150–500 °C) for a GHSV of 44,000 h−1. Among the palladium and noble metals deposited catalysts, the PdCoAPO-5 and RhCoAPO-5 showed excellent performance. For the RhCoAPO-5 (Rh loading = 2.98% and Rh particle size = 2.2 nm) catalyst, the temperature required for complete NO reduction was 210 °C, which is lower than that required for PdCoAPO-5 (Pd loading = 2.96% and Pd particle size = 4 nm) and IrCoAPO-5 (Ir loading = 2.89% and Ir particle size = 6.5 nm) under identical conditions. The Rh deposited CoAPO-5 catalyst effectively operated at lower temperatures as compared with the other noble metal deposited CoAPO-5 catalysts studied here.