Deep Oxidative Desulfurization Of Diesel By Dielectric Barrier Discharge And Ionic Liquid Synergistic Effect

Deep desulfurization from fuel oils has become an increasingly important subject worldwide. Thesulfur content present in the fuel oils can converted to sulfur oxide SOx during combustion, which not onlythe major source of acid rain, but also irreversibly poisons the catalysts for the conversion of NOx and CO,desulfurization has become an important unit operation in petroleum refining and has paid more attentionall over the word.The conventional method for removing sulfur in industry is catalytic hydrodesulfurization （HDS）process, which is limited for treating some refractory sulfur compounds such as dibenzothiophene （DBT） orits derivatives with one or two alkyl groups which are abundant in gasoline and especially in diesel.Consequently, it is difficult or very costly to use the existing HDS technology to reduce the sulfur in thefuels to less than10ppmw. Oxidative desulfurization （ODS） combined with adsorbent is considered to be apromising approaches, because the process can remove the refractory sulfur compounds under ambientconditions. hydrogen peroxide in aqueous solution are well known among oxidants for ODS, however, theyinvolve water in the reaction system which results in the biphasic problems of the mass transfer and oilphase recovery. So we exploit a ODS method combines a catalytic oxidation step by DBD plasma in thepresence of air and an extraction step of the oxidation-treated fuel over the ionic liquid.（1） One reactors was designed and machined through cogsidering the non-equilibrium plasma and thecharacteristic of diesel.（2） A series of ionic liquids based on metal salts were synthesized and employed in extractivedesulfurization systems, the IL containing anhydrous FeCl₃and [Omim]Cl showed the highest extractiveefficiency. The sulfur removal of DBT-containing model oil could reach99.4%with [Omim]Cl·2FeCl₃asextractant at room temperature, even when the model oil/IL ratio got to20:1. For BT and4,6-DMDBT,96.2%and99.3%S-removal were also achieved in30min. The extractive efficiency of sulfur-containingcompounds decreased in the order of DBT> BT>4,6-DMDBT. Moreover, this IL [Omim]Cl·2FeCl₃couldbe recycled five times without a significant decrease in activity. With the efficient production of ionicliquids in the chemical industry, the method of extractive desulfurization may be a simple, promising andenvironmentally-friendly process.（3） To study the oxidative/adsorptive desulfurization of refractory sulfur compounds using FeCl₃-SiO₂in plasma zone, three model sulfur compounds such as benzothiophene （BT）, DBT and4,6-dimethyldibenzothiophene （4,6-DMDBT） was carried out under the same conditions. The result wasshown in Fig.7, indicate that the activities of the three sulfur compounds increased over time and decreasesin the order DBT> BT>4,6-DMDBT, The removal of BT, DBT and4,6-DMDBT was94.8%,98.3%and92.7%after30min at room temperature, respectively. Among the three sulfur compounds, the activity wasinfluenced mainly by two factors, that is, the chemical molecular structure of sulfur compounds and thesurface properties of FeCl₃-SiO₂.（4） A novel oxidative desulfurization of liquid hydrocarbon fuels was explored to study theextraction–catalytic oxidation system with diperiodatocuprate （III） as the catalyst. In the presence of DBD,air as oxygen resource and [Bmim]FeCl₄as the extraction solvent were investigated in the removal of DBT,BT and4,6-DMDBT from the model oil. The S removal from DBT containing the model oil in[Bmim]FeCl₄reached97.5%. The IL could be recycled four times with a slight decrease in activity. Thus,the catalytic system can be developed into a simple, efficient, and environmentally friendly method fordeep desulfurization.（5） The mechanism of deep oxidative desulfurization of diesel by Dielectric barrier discharge andionic liquid was preliminary studied. This properly can instantaneously form a strong electric field andproduce non-thermal plasma, contains a significant amount of cation, anion (O_<sup>2-), ozone （O₃）, free radicals（OH, H, HO₂） active oxygen （O） and NOx in the presence of air or molecular oxygen. NOx is a harmful by-product in the DBD reactor. Active species hydroxyl radicals and reactive oxygen, especially ozone, arepotentially ideal oxidants for ODS. It can easily oxidize DBT to the hexavalent sulfur of DBT sulfones, andthe sulfones can be easily removed by conventional separation to obtain ultra-low-sulfur diesel.