Interaction of phosphorus with a FeTiOx catalyst for selective catalytic reduction of NOx with NH3: Influence on surface acidity and SCR mechanism

Phosphorus were employed to investigate the influences on the acid sites and reaction mechanism of FeTiOx SCR catalyst. The introduction of phosphorus inhibited the SCR activity by suppressing the redox property, decreasing the surface acidity and reducing the surface area. In particular, phosphorus preferentially bonded to the electron-deficient Ti4+ and Fe3+ cations on the surface as P-O-Fe and P-O-Ti, thereby blocking the Lewis acid sites (Fe-NH3 or Ti-NH3). Although phosphate provided additional Bronsted acid sites (P-O-NH4+), the larger decrease of Lewis acid sites results in the decrease of total surface acidity. The newly formed Bronsted acid sites showed less SCR active at low temperature and exhibited high thermal stability and reactivity at high temperature, which leads to a new pathway following the L-II mechanism and an enhancement of high temperature performance.

采用磷来研究其对FeTiOx SCR催化剂酸性位点和反应机理的影响。磷的引入通过抑制氧化还原性能、降低表面酸性以及减少表面积而抑制了SCR活性。特别是，磷优先以P - O - Fe和P - O - Ti的形式与表面缺电子的Ti⁴⁺和Fe³⁺阳离子键合，从而阻塞了路易斯酸位点（Fe - NH₃或Ti - NH₃）。尽管磷酸盐提供了额外的布朗斯特酸位点（P - O - NH₄⁺），但路易斯酸位点的大幅减少导致总表面酸性降低。新形成的布朗斯特酸位点在低温下SCR活性较低，在高温下表现出高热稳定性和反应性，这导致了遵循L - II机制的新途径以及高温性能的提高。