Transition Metal-based Ionic Liquid Polymers For Deep Oxidative Desulfurization Of Fuels

At present,fuel is still the main energy consumption in industrial economic development,but sulfur oxides emitted by the combustion of sulfur-containing fuel cause air pollution and emission of acid rain.As a result,many countries have issued a strict emission standard,which is a huge challenge for the refining industry.Hydrodesulfurization is a kind of desulfurization technology which is more mature in industrial,but the method requires strict reaction conditions such as high temperature and high pressure.Therefore,researchers explore non-hydrodesulfurization technology with mild reaction conditions,in which oxidation has received widespread attention due to its high desulfurization efficiency and green environmental protection.In recent years,poly ionic liquids（PILs）formed by the polymerization of ionic liquid monomers has become the focus of attention in various research fields.PILs not only have excellent properties of ionic liquids,but also have the adjustable structure and easy to separate.Focusing on the topic of ionic liquid polymer,this paper synthesizes a series of catalysts which PILs by free-form polymerization combine with POM by anion exchange.The property of catalytic oxidation desulfurization of fuel with hydrogen peroxide as an oxidant have been explored.The imidazole based ionic liquid monomer synthesized PILs by free-based polymerization,and then the catalyst C8-PIL@PW was prepared by anion exchange method.The results show that the length of carbon chain in the cation part of PILs has a great influence on the catalytic performance.Under the conditions of oxygen-sulfur ratio of 6,reaction temperature of 50^oC and catalyst dosing of 50 mg,the desulfurization efficiency of C8-PIL@PW can reach 99%.The desulfurization efficiency can still reach 89%after 5 cycles,in which no organic solvent is added as extractant in the process.In addition,the desulfurization properties of different sulfur-containing substrates are investigated that the desulfurization efficiency order of different sulfides is DBT>4,6-DMDBT>4-MDBT under optimal reaction conditions.The mechanism of reaction process is explored by GC-MS,which proves that the reaction product is fully converted to DBTO₂.The poly acid loaded catalyst C-PIL-POM-Si O₂ was synthesized which PILs were loaded on the prepared silica by impregnation method and C-dots was doped.The structure of the catalyst is explored by SEM and BET,which proves that the load-type catalyst has more surface area that is beneficial to the uniform distribution of the active points.The experimental results show that C-PIL-POM-Si O₂ can reach99.95%desulfurization efficiency within 60 min under the optimal condition that the reaction temperature is 50^oC,the O/S ratio is 3 and the catalyst dosing is 10 mg.At the same time,oxidation desulfurization experiments on different sulfur-containing substrates of 4-MDBT and 4,6-DMDBT under the optimal conditions also achieve good removal efficiency,which are 96.95%and 94.85%,respectively.The catalyst is cycled and found that the ODS efficiency can still reach 97.78%after six cycles.It is demonstrated that C-PIL-POM-Si O₂ has a good stability.Hence,it is proved that the load of Si O₂ is beneficial to the effective contact between active sites and sulfides.Moreover,as a catalyst,C-dots has its own rich function group structure,which can effectively activate hydrogen peroxide,thus further improving the efficiency of desulfurization.The mechanism of reaction process is explored by GC-MS and ESR,which proves that the reaction product is fully converted to DBTO₂,and hydroxyl free radical and superoxide free radical act together during the reaction.