چكيده به لاتين
Oxidative desulfurization is one of the most important and desirable options for preparing diesel fuel with very low sulfur content in accordance with the latest environmental standards all over the world. In recent years, polyoxometalate catalysts have attracted special attention in the oxidative desulfurization process due to their high efficiency.Therefore in this study, Keggin and Dawson-type vanadium-containing hetropolyacids (HPAs) were synthesized and then covalently immobilized on amine-functionalized magnetic graphene oxide (APTES-MGO). Several techniques, including FT-IR, XRD, SEM-EDX, VSM, TGA, ICP-OES, Raman spectroscopy, and N2 adsorption-desorption isotherms, were used to characterize the samples. The results showed that under constant operating conditions, heteropolyacids with Keggin structure will perform better in removing dibenzothiophene than Wells-Dawsen structure with the same number of vanadium atoms in both homogeneous and heterogeneous states. Heteropolyacid K-PV2@APTES-mGO, (K-PV2 stands for H5PMo10V2O40 with Kegin structure and containing two vanadium atoms), had the highest dibenzothiophene removal efficiency. Meanwhile, the effect of loading percentage of active component K-PV2 on the prepared magnetic base was investigated. The results showed that the catalyst with the loading amount of 40% by weight of K-PV2 had the highest removal of dibenzothiophene. Also, the research on the four operating parameters of temperature, reaction time, molar ratio of oxidant to sulfur, and the amount of catalyst used was investigated in order to determine the optimal conditions using the response-surface design method. In optimal conditions including the use of 4.5 grams of catalyst per liter of model fuel, and the molar ratio of oxidant to sulfur is equal to 7, in a relatively short period of 30 minutes at a temperature of 45 degrees Celsius, the sulfur composition of the model fuel is completely deleted. After each EODS run, the catalyst can be easily separated and recovered from the reaction medium via an external magnetic field without significant mass loss. catalyst exhibited more than 95.0 % DBT removal efficiency even after 9 times of regeneration, showing the excellent stability of the nanocomposite catalysts. Next, with the aim of improving the operating conditions in this study, the EODS process was investigated in a magnetic fluid bed reactor for the first time. Comparing the performance of the two reactor systems showed that the EODS process in the fluidized bed reactor was affected by the magnetic field requires shorten time (20 min), the lower amount of catalyst (3 grams per liter of fuel) and lower the amount of oxidant (the molar ratio of oxidant to sulfur equal to 4) for complete DBT removal. In such a way that the use of magnetic field around the reactor will increase the contact of the reactants with the catalyst particles and reduce the mass transfer resistance.
