چكيده به لاتين
Liquid hydrocarbon fuels contain high amounts of sulfur compounds. Ignition of these compounds causes to SOx emission that is extremely harmful to the environment. The oxidative desulfurization (ODS) process is a promising complement process to the hydrodesulfurization (HDS) to remove refractory sulfur compounds of liquid hydrocarbon fuels under low temperature and atmospheric pressure.DBT was oxidized to DBT-sulfone, a species with a higher polarity that could be subsequently adsorbed on the active sites and therefore, Controlling the adsorption and polarity properties of solid catalysts is very important in improving activity and catalyst life.
Thus, In addition to the importance of selecting the suitable active site, the adsorption properties of the catalysts are necessary. In this study, The nanostructured titania -silica catalyst synthesized using a sol-gel method and investigated for oxidative desulfurization (ODS) of dibenzothiophene (DBT) and surface modified by silylation to aiming decrease the adsorption of the more polar sulfones on the surface that will strongly contribute to catalyst deactivation.
The samples were silylated with hexamethyldisilazane and trimethylchlorosilane to increase their hydrophobicity by the reaction between OH groups with the alkyl silyl group of the silylating agent, thus rendering the material more hydrophobic.The oxidative desulfurization was conducted in a batch reactor with tertbutylhydroperoxide (t-BuOOH) as an oxidant and the molar ratio of oxidant to sulfur (O/S) was 5. The catalyst dosage was 0.03 g for 3 g model fuel that includes 500 ppm dibenzothiophene in n-dodecane, At 50 °C and 1 atmosphere.
The conversion of dibenzothiophene was determined with the gas-chromatography equipped pulsed flame photometric detector (PFPD) and the effect of silane agents, oxidant, temperature reaction, nitrogen, and aromatic compounds. The catalyst samples were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), diffuse reflectance UV-vis spectrum (UV-Vis DRS), Thermogravimetric (TGA), energy dispersive X-Ray (EDX) and Mapping and Contact angle (CA). The best catalytic activity was observed for the TS-H2 sample modified with 4 wt% HMDS/Toluene achieved 100% DBT conversion after only 20 min of the reaction at 50°C.
Keywords: Nanostructured catalyst, Surface modification, Silylation, ODS
