One-pot synthesis, characterization and ammonia-selective catalytic reduction performance of MnSAPO-18 molecular sieves

A one-pot synthetic method was used to prepare novel MnSAPO-18 catalysts with high crystallinity that were employed to efficiently scrub NO x in the flue-gas denitration reaction. In the controllable synthesis of MnSAPO-18, the effect of Mn content, organic amine templates, Mn precursors as well as hydrothermal crystallization time on the SCR performance of the resulting MnSAPO-18 catalysts and the structure-activity relationship of these samples was also investigated. The optimum combination of these variables in the hydrothermal synthesis process appeared to be using N,N-Diisopropylethylamine as the organic templates, manganese acetate as the Mn precursor, a crystallization time of 24 h and Mn content of n(MnO)/n(Al 2 O 3 ) = 0.2 in the synthesis gel. The optimum Mn 0.2 SAPO-18-2 catalyst exhibited nearly 95% NO x conversion and 90% N 2 selectivity in temperature range of 275–375 °C with a space velocity of 37,500 h −1 . In the low-cost seed-assisted, one-pot synthesis of Mn 0.2 SAPO-18-1.0DIPEA-Seed, it was found that this sample had almost comparable activity as the Mn 0.2 SAPO-18-2 in the traditional one-pot method. These novel catalysts were characterized using the H 2 -TPR, NH 3 -TPD, XRD, FESEM, DR UV–Vis and ESR analysis. The results of these characterizations showed that the optimum SCR performance of Mn 0.2 SAPO-18-2 was closely related to its abundant high valence framework manganese, suitable surface acidity and high redox capability. Thus, Mn 0.2 SAPO-18-2 was shown to be a promising catalyst for NH 3 -SCR removal of NO x and this fabrication technique appeared to be potentially valuable for application in industry. • MnSAPO-18 molecular sieves were synthesized by one-pot synthesis method. • The preparation and properties of MnSAPO-18 molecular sieves are outlined. • Mn 0.2 SAPO-18-2 and Mn 0.2 SAPO-18-1.0DIPEA-Seed samples exhibited high SCR activity. • Mn species in the Mn 0.2 SAPO-18 catalyst was mainly in the form of Mn 4+ .