Preparation And Catalytic Performance Of Supported Heteropolyacid-Phthalocyanine Composite Catalyst For Oxidative Desulfurization

In recent years,many regions in China have been affected by haze weather.The quality of air has continued to decline,which has been a great thread to people's life,production and health.The sulfides in fuel oil generate a large amount of sulfur oxides?SOx?and nitrogen oxides?NOx?,which can cause pollution to the atmospheric environment without treatment before combustion.With the air pollution becomes more serious as well as the environmental protection regulations become stricter,development of new,high-efficiency deep desulfurization catalysts and technological processes has become top priority of the petroleum refining industry.Currently,among many desulfurization technologies,oxidative desulfurization?ODS?attracts most attention from researchers worldwide due to the inherent advantages like mild reaction conditions,simple techniques,without hydrogen consumption and low cost.As a new material in the field of catalysis,heteropolyacid?HPA?is widely used in various organic catalysis reactions because of its unique structures and redox properties.Recently,the design,synthesis and application of highly efficient oxidative desulfurization catalysts that based on HPA attracted most attention.Metal phthalocyanine?MPc?is a kind of compound of conjugated macrocyclic coordination with good thermal stability and chemical stability,it can also remove the thiols from fuel oil effectively.However,there are few studies on the oxidative removal of thiophene and other heterocyclic sulfides use MPc as catalyst.Based on the above facts,in this study,HY zeolite is used as catalyst carrier,a series of supported HPA,MPc and composite HPA-MPc catalysts were prepared by impregnation method and high-temperature hydrothermal method.Dibenzothiophene?DBT?,benzothiophene?BT?,and thiophene?Th?were dissolved in n-decane to prepare the model fuel.The appropriate reaction conditions of each system were investigated in detail,including the amount of catalyst,the amount of oxidant,the reaction temperature,the amount and types of extractant and so on.This research was focused on the influence of different catalysts on the catalytic performances and reusability.In addition,the structure,composition and thermal stability of catalysts were characterized by means of XRD,FT-IR,Raman,UV-Vis,TG,N₂adsorption-desorption and SEM.The structure-performance relationship of catalysts was also explored.The Keggin-type HPAs?V₂?was synthesized by substep acidification-ether extracted,and a series of catalysts with different loading of HPAs on HY zeolite were prepared by impregnation method.XRD and FT-IR characterization results indicated that the HPA was highly dispersed on the surface of the HY zeolite and maintained its complete Keggin structure.The optimum reaction conditions for oxidative desulfurization are as follows:30 mg of catalyst,H₂O₂ 0.1 mL,reaction temperature70?and acetonitrile as extraction agent.Under these conditions,the catalyst10%V₂/HY showes the best catalytic activity with the DBT conversion reached up to99.2%.Furthermore,the catalyst has good catalytic reusability and the conversion of DBT still reach up to 90.1%after 7 times of reaction cycle.The FePcCl₁₆6 and CoPcCl₁₆6 were synthesized by phthalic anhydride-urea method.A series of supported CoPc,FePcCl₁₆ and CoPcCl₁₆ catalysts were prepared by impregnation method.The characterization results indicated that the supported metal phthalocyanine catalysts have good thermal stability,MPcs are highly dispersed on the surface of the HY zeolite,and the structure of MPcs and HY are unchanged.It has been found that catalyst,sulfide and extractant properties are the synergistic influencing factors of oxidative desulfurization.When acetonitrile is used as extractant,for the removal of simple sulfides such as thiophene under the same reaction conditions,the phthalocyanine compounds are more suitable than the heteropoly compounds.With acetonitrile as extractant,the phthalocyanine catalysts is more effective for the removal of simple sulfide,such as thiophene than the heteropoly catalystsunder the same reaction conditions.The phthalocyanine catalysts with different compositon has almost the same activity for oxidative desulfurization of thiophene.The oxidative desulfurization activity of different sulfides?Th,BT,DBT?increase significantly when DMF is used as extractant.Under the optimum reaction conditions:catalyst of 10 mg,H₂O₂ 0.1 mL,reaction temperature 60?and DMF as extractant,the catalyst CoPc/HY shows the better catalytic activity,and the conversion of DBT reached up to 88.4%.The catalyst has excellent catalytic reusability and the conversion of DBT can reach up to 86.4%after 6 times of reaction cycle.With the HPA?V₂?and three MPcs(CoPc,FePcCl₁₆6 and CoPcCl₁₆)as active ingredient,and HY zeolite as carrier,a series of composite catalysts were prepared by high-temperature hydrothermal method.There was a certain interaction between the HPA-MPcactive ingredient and the HY carrier.The HPA-MPc was highly dispersed on the surface of HY and the structure of HY carrier remained unchanged.Under the conditions:catalyst of 30 mg,H₂O₂ 0.1 mL,reaction temperature 60°C,and DMF as extractant,the composite catalyst CoPcCl₁₆-V₂/HY had excellent oxidative desulfurization performance for heterocyclic sulfide,and the conversion of DBT reached up to 91.7%.Furthermore,the catalyst has good catalytic reusability and the conversion of DBT still reach up to 89.6%after 6 times of reaction cycle.In addition,the three composite catalysts also have good oxidative desulfurization performance for mixed sulfides?Th+BT+DBT?.