In situ encapsulated molybdovanaphosphodic acid on modified nanosized TS-1 zeolite catalyst for deep oxidative desulfurization

In order to solve air pollution caused by SOx, oxidative deep desulfurization of diesel, has become a hotspot all over the world. In this paper, molybdovanaphosphodic acid (HPV2Mo10), a typical polyoxometalate (POM), was in-situ impregnated on TS-1-TAPOH@SiO2 which originated from TS-1 modified by tetrapropylammonium hydroxide (TPAOH) and tetraethyl orthosilicate (TEOS). The catalysts were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Ultraviolet–Visible Diffuse Reflectance (UV–vis), Raman Spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), N2-physisorption, X-ray Photoelectron Spectroscopy (XPS), Inductively Coupled Plasma Spectroscopy (ICP), 31P and 29Si Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR). The characterization results of XRD, FT-IR, UV–vis, Raman and MAS-NMR showed that HPV2Mo10 was successfully loaded on TS-1-TPAOH@SiO2, while the structure of support and Keggin-type of HPV2Mo10 remained unchanged. The catalysts were applied to the oxidative desulfurization (ODS) and adsorption desulfurization of thiophene (TH), benzothiophene (BT), and dibenzothiophene (DBT). The results show that HPV2Mo10/TS-1-TPAOH@SiO2 catalyst prepared by in-situ method has the best oxidation activity when the structure of both the POM and modified zeolite are retained. Under the selected reaction condition: T = 70 °C, n(H2O2)/n(Sulfur) = 13, m oil: m catalyst = 35: 1. The conversion rates of TH, BT and DBT over HPV2Mo10/TS-1-TPAOH@SiO2-in situ after 3 h were 99.3%, 45.9% and 84.1%, respectively. The function of two part in the investigated HPV2Mo10/TS-1-TPAOH@SiO2 catalyst, known as the modified nanosized TS-1 zeolite and HPV2Mo10, for the oxidative desulfurization activity are demonstrated.