Elimination of Thiophenic Compounds by Cycloaddition with Ethylene for an Efficient Purification of Fuels: A DFT Study
Abstract
Using DFT calculations, we have investigated the cycloaddition of thiophene with ethylene, followed by desulfurization
of the produced heterobicyclic molecules at 373 K. The whole reaction process has been modeled in three steps: (i) the
molecule adsorption on tungsten sulfide acting as a catalyst, (ii) the cycloaddition of the adsorbed molecule with ethylene,
(iii) the elimination of the sulfur atom by hydrogenation of the cycloaddition products. Cycloaddition, in the presence or in
the absence of catalyst, produced a bicyclic compound including a C–S bond. Its reaction with hydrogen led to the hydrogenolysis
of C–S bonds. Without catalyst, the reaction of bicyclic compounds with hydrogen led to a double hydrogenolysis
producing cyclohexa-1,2-diene and hydrogen sulfur. In the presence of catalyst, the reaction took place in two steps, leading
to cyclohexene. With increasing the molecular weight of compounds, cycloaddition can allow the separation between
light hydrocarbons from alkyl-thiophenic molecules with distillation, knowing that boiling temperature increases with the
molecular weight. Although consuming more hydrogen, the reaction with catalysts led to an unsaturated cyclic product which
can improve the octane number of fuels containing them.