Hydrothermally synthesized mesoporous titanium-containing Y zeolites with different titanium contents and their high activity for hydrodenitrogenation of quinoline and indole

Abstract

Herein, the effect of in-situ Ti modification on the physicochemical properties of the TixY zeolites and the corresponding NiW supported TixY-A catalysts, as well as on the catalytic performances for aromatic N-heterocyclic compounds hydrodenitrogenation (HDN) was investigated. The existing forms of Ti atoms in the Y zeolites and the active metal states of the corresponding catalysts were investigated by XRD, ICP-OES, SEM, FTIR, UV–Vis DRS, CP-MAS NMR, N2 physical adsorption–desorption, Py-FTIR, H2-TPR, HRTEM, XPS and DFT calculation. The results show that the Ti atoms can be effectively introduced into the Y zeolite framework by the in-situ hydrothermal crystallization method. With the increase of TiO2/Al2O3 molar ratio in the Y zeolite, the amount of Brønsted acid sites of the zeolite tended to decrease constantly, but the reducibility of the catalyst and the stacking layer number as well as the sulfidation degree of the NiWS active phase continued to be enhanced. The highest quinoline and indole conversions of 86.5 % and 46.9 % at 320 °C, 4.0 MPa, 300 H2/oil (v/v), and 10 h−1 LHSV, as well as the highest TOFs of 2.24 h−1 and 1.04 h−1, the highest kHDN values of 12.4 × 10−4 mol·g−1·h−1 and 3.6 × 10−4 mol·g−1·h−1, and the highest denitrogenated product selectivities of 46.1 % and 66.2 % under quinoline and indole conversions of about 15 % and 50 % respectively have been achieved in catalyst NiW/Ti0.1Y-A due to the perfect matching of its hydrogenation and hydrogenolysis performance, which was mainly derived from the remarkable synergistic effect between the Brønsted acid sites of the Y zeolite and the NiWS active phase of the catalyst.