چكيده به لاتين
Sulfur is one of the major contaminants in petroleum products. Therefore, removal of sulfur compounds in hydrocarbon fuels is important in terms of the environment. To remove refractory thiophenic compounds by hydrogen desulfurization, other new technologies can be used as alternatives to the hydrodesulfurization process. One of these new methods is the electrochemical desulfurization, which has many advantages such as mild operating conditions (low temperature and pressure), control of reaction rate selectivity and the ability to remove refractory sulfur compounds, such as thiophene. Therefore, in this project, first electrochemical desulfurization of benzothiophene was investigated in a dynamic (absorption-reduction) method on platinum electrode. In the next step, the performance of thiophene oxidation was evaluated on various electrodes such as platinum, carbon doped carbon, iradium-ruthenium oxides, lead/lead oxide and graphite in acid electrolyte under different potentials. Then, the fuel desulfurization of the model fuel containing thiophene and benzothiophene was studied by electrocatalyst of platinum/carbon in the electrochemical separator separated by fuel and electrolytic emulsion, and in the fourth step, the performance of the platinum/carbon and molybdenum disulfide electrocatalysts in the membrane electrochemical reactor using electrocatalystmembrane assembley was studied Also, electrochemical evaluations such as cyclic voltammetry, electrochemical impedance spectroscopy were also carried out for electrode/ electrocatalyst and electrocatalyst-membrane assembly. Desulfurization efficiency of benzothiphene by applying the adsorption/reduction potential on the platinum electrode over 8 hours reached to of 48.2%. In oxidation of thiophene, the desulfurization efficiency on platinum electrodes and Iridium-Ruthenium oxides increased up to 92% and 98%, respectively, and their current efficiency was 48% and 29%, in the potential of 2.5 V for 3 hours, respectively. Electroreductive desulfurization of model fuel using platinum/carbon in sodium hydroxide electrolyte showed 97% sulfur removal at current efficiency of 78% and potential of 0.75 V. The best performance was related to platinum/carbon‒Nafion membrane with maximum desulfurization efficiency of 85% at 20 mA cm-2 for thiophene and 71% at 50 mA cm-2 for benzothiophene. Desulfurization using molybdenium disulfide-Nafion membrane also resulted in the thiophene and benzothiophene removal of 79.6% at 20 mA cm-2 and 60% in 70 mA cm-2, respectively. Desulfurization using molybdenum disulfide-Nafion membrane also resulted in the removal of thiophene and benzothiophene, 79.6% at 20 mA cm-2 and 60% at 70 mA cm-2, respectively. Best performance was achieved by the electrochemical membrane reactor with desulfurization efficiency of 85% at 20 mA cm-2 for thiophene and 50% at 50 mA cm-2 for benzothiophene. The hydrogenation efficiency of 12% was also obtained, which is lower than that of the achieved using divided and undivided reactors. Moreover, the ease of process and no need for fuel emulsification as well as the remarkable removal of thiophenic compounds are unique advantages of the electrochemical membrane reactor. Although the Nafion membrane and the Pt/C electrocatalyst showed best performance in desulfurization process, SPEEK membrane and MoS2 electrocatalyst could also be utilized as an alternative electrocatalyst in desulfurization of thiophenic compounds owing to their lower cost and almost similar desulfurization efficiency using electrochemical membrane reactor.
