چكيده به لاتين
Combustion of fossil fuel with high sulfur content cause environmental problems and sulfur compounds in fuels leads to inactivation of catalyst and corrosion of refining equipment. Electrochemical Desulfurization (ECDS) is able to remove sulfur at lower temperature and pressure than conventional hydrodesulfurization processes is more economical. Electrocatalysts are the most important component of electrochemical cell. In this research, performance of Pt, Pt/C, and MoS2 for electrochemical desulfurization of thiophene/Benzothiophene-containing model fuel by applying a square wave between adsorption and reduction potential in undivided cell was investigated.
In order to determining optimal adsorption potential on platinum surface electrode, first a constant potential was applied to the electrolyte solution containing Benzothiophene (BT) and then in the electrolyte solution without BT, a voltammogram was taken from electrode surface. After investigation the result voltammogram, the potential of 0.3 volt was selected as the optimum adsorption potential of BT. Then a model fuel containing 344 ppm of BT in n-decane solvent was prepared. The emulsion of model fuel and acidic electrolyte in the optimal condition of 50% (v/v) of organic phase plus, 0.2% emulsifier with HLB 13, was prepared. finally, emulsion model fuel desulfurized by applying a square wave beween adsorption potential (0.3 volt) and reduction potential (-0.15 volt) at optimal frequency of 10 Hz. X-ray fluorescence spectroscopy test showed that 44% BT resistant sulfur compound removed.
In the next step hydrothermal synthesis of molybdenum disulfide low cost electrocatalyst with ammoniumheptamolybdate and thiourea as the source of molybdenum and sulfure, respectively, was carried. X-ray Diffraction test showed that the average size of particle was 5.7 nm. MoS2 electrocatalyst was coated on glassy carbon electrode and after performing of voltammetry test, optimal adsorption potential of thiophen on MoS2 was selected 0.5 volt. Model fuel containing 420 ppm thiophene desulfurizaed by MoS2 coated on carbon paper at optimal condition (adsorption potential (0.5 volt), reduction potential (-0.25 volt), optimal frequency of 0.2 Hz). Gas chromatography test results showed 85% thiophene was removed. In the following, electrochemical active surface area of MoS2 obtained 4.67 m2/g by cyclic voltammetry. Linear swip voltametry test showed that MoS2 has the high overpotential for undesired hydrogen evolution. According to results obtained, MoS2 low cost catalyst has a high efficieny for electrochemical removing of thiophene.
In order to increase the active surface with the aim of achiving the highest rate of mass transfer and facilitating the elctron transfer, catalyst basis is being used. So carbon black is used as basis platinum catalyst. Electroreductive desulfurization of thiophene and benzothiophen-containig model fuel was carried on Pt (40%)/C by applying square wave between adsorption and reduction potential of 0.1 and -0.15 volt at optimal frequency of 0.1 Hz. Gas chromatography analysis showed that thiophene and Benzothiophen were removed 61% and 48% respectiveky. In the following, the electrochemical active surface area of Pt/C obtained 9.67 m2/g. as well as electrochemical ampedance test confirmed the positive effect of increasing surface Pt/C catalyst than Pt in electrochemical desulfurization.
Keywords:
Electrochemical desulfurization, Electrocatalyst, Molybdenum Disulfid, Thiophen, Square wave
