Preparation Of Ionic Liquid-heteropolyelic Acid Supported Catalysts And Study On Its Oxidative Desulfurization Performance For Thiophene Compounds

The sulfide compounds in oil products are extremely harmful to the environment and human health,and many countries and regions have set strict sulfide emission standards to limit the sulfide content in fuel oil.Therefore,the production of ultra-clean low-sulfur oils is crucial.Among many desulfurization methods,oxidation desulfurization process has attracted much attention because of its mild operating conditions and high desulfurization efficiency.In the oxidative desulfurization process,the key to improve the desulfurization efficiency is to continuously develop new oxidative desulfurization catalysts with high activity,low cost and recyclability.The catalysts commonly used in oxidative desulfurization include metal oxides,ionic liquids and heteropoly acids.Homogeneous catalysts such as heteropoly acid（HPA）catalyst and ionic liquid（IL）catalyst have the advantages of good stability,strong acidity,strong oxidation,etc.They are active components with good performance,At the same time,ionic liquid-heteropoly acid（HPA-IL）active component could be obtained by the reaction of heteropoly acid and ionic liquid,and the desulfurization activity of POK-IL is higher than the single component of heteropoly acid or ionic liquid.However,HPA-IL has some shortcomings such as small specific surface area and difficult recovery.The heterogeneous catalysts such as supported catalysts are easy to recover.Molecular sieve,metal-organic framework materials（MOF）and other supports are widely used as catalyst supports because of their good pore structure,and doping rare earth metals can further improve their stability,promote the dispersion of active components,and improve their catalytic performance.Therefore,in this dissertation,porous supports such as Y-UiO-66,La-UiO-66and Y-SBA-15 were obtained by doping modification of rare earth metals.Then ionic liquid-heteropoly acid was loaded on porous supports to obtain supported catalysts.Organic thiophene sulfide containing thiophene rings was used as the model sulfide to evaluate the oxidative desulfurization performance of the series of catalysts.The main research contents and results are as follows:（1）Firstly,the rare earth metal yttrium（Y）was doped into the organic metal framework material UiO-66,and then the heterogeneous catalyst[C₁₂mim]PWO/Y-UiO-66 was obtained by loading HPA-IL on the modified UiO-66,which gave full play to the high activity of the active component,and also solved the problem of separation and recovery.The structure of imidazole ring and heteropoly acid Keggin unit PW₁₂O₄₀^3-in the active component remained intact on the catalyst.Under the conditions of m_cat=0.1 g,V_Oil=10 m L,n_（O/S）=5 and reaction temperature60℃,the removal rate of DBT reached 96.0%within 60 min.（2）Compared with yttrium（Y）,lanthanum（La）has the advantages of large adsorption capacity and high adsorption efficiency.Therefore,La-UIO-66,a La-doped UiO-66 support with excellent performance and stable structure,has been prepared on the basis of previous studies.Then,a heterogeneous catalyst[C₁₂mim]PWO/La-UiO-66 was obtained by loading HPA-IL on La-UiO-66,which can be obtained under the conditions of m_cat=0.1 g,V_Oil=10 m L,n_（O/S）=5 and reaction temperature of 60℃.The DBT removal rate reached 100%within 60 min.Therefore,the catalytic activity is further improved.（3）Compared with UiO-66,graphitic phase carbon nitride g-C₃N₄has attracted extensive attention due to its advantages of convenient preparation and high chemical stability.Therefore,[MIMPs]PMo WO/g-C₃N₄catalyst supported by g-C₃N₄was prepared.The synthesis process of this catalyst is simple,with slit mesoporous structure and pore size of 17.6 nm.[MIMPs]PMo WO/g-C₃N₄catalyst can achieve100%DBT conversion within 40 min.After 6 cycles of oxidative desulfurization,the desulfurization rate still reached 92.0%.The desulfurization rate of real catalytic cracking diesel oil reached 96.1%.（4）Although[MIMPs]PMo WO/g-C₃N₄catalyst has high desulfurization efficiency,but g-C₃N₄has problems such as small specific surface area and irregular pore.Therefore,it is of great significance to find a support with regular pore,large specific surface area and economy for the industrial application of oxidative desulfurization.In this dissertation,the amphiphilic 25[Bmim]PMo O/10Y-SBA-15catalyst was synthesized by using rare earth element Y doped on SBA-15 by solvo-free solid grinding method to further improve the performance of the support,and thus improve the ODS performance of the catalyst.The catalyst has regular pore structure,specific surface area of 400 m²·g^-1,pore size of 6.5 nm.Under the conditions of m_cat=0.1 g,V_Oil=10 m L,m_{PMo O}^[Bmim]:m^[Bmim]_{PMo O/10Y-SBA-15}=25%,DBT can be completely removed within 40 min.The ODS activity remained 92.5%after 6 cycles.Studies on ODS mechanism show that·OH and·O₂^-are important active species in ODS reaction.The sulfur content in the product oil can be reduced from 203μg/g to 8μg/g,and the regeneration performance is good.During the process of synthesis,doping and loading of the active phase:The doping of rare earth（Y,La）can create more adsorption sites of-Y-and-La-without breaking the mesoporous structure,which is conducive to the adsorption of sulfides.Because ofπ-πinteraction,the lipophilic part of long chain ionic liquid(such as[C₁₂mim],[MIMPs]and[Bmim])can also adsorb sulfides and increase the concentration of sulfides.Heteropoly acids（such as PWO,PMo O and PMo WO）have good hydrophilicity,which is conducive to their contact with water-soluble oxidant H₂O₂,thus improving the efficiency of oxidative desulfurization.It provides experimental support and guidance for the development of oxidation desulfurization catalysts with high activity,high selectivity,excellent reuse performance and low cost.