Confining the reactions on active facet enhances the simultaneous removal of NOx and toluene by copper-titanium catalysts

Abstract

Exposure of the low adsorption energy barrier facet facilitates the interaction between the catalyst support and the active species, and morphology modification was considered to be a feasible strategy to regulate the exposure of specific facet. The TiO2 support with hollow spherical shell structure (h-TiO2) was prepared using hard template method, and CuO was loaded on the inside and outside of h-TiO2 to obtain catalysts with different loading positions (Cu@h-TiO2, Cu/h-TiO2). For the efficient catalyst Cu@h-TiO2, NO conversion was above 95 % and N2 selectivity exceeded 90 % in the range of 250–275 ℃. In this catalyst, CuO was loaded on the internal low adsorption energy barrier facet of anatase TiO2 (200). In comparison to Cu/h-TiO2, and Cu@h-TiO2 exhibited more acidic site, stronger redox ability and reduced the temperature of toluene oxidation to match the temperature for NH3-SCR. Based on DFT studies, the adsorption energies of three adsorbates: toluene, NH3, and H2O on two types of anatase TiO2 crystal facets (200) and (101) were calculated, respectively. The results revealed that the adsorbates had a lower energy barrier on the (200) facet, which indicated a higher activation efficiency for the three adsorbates on this facet.