Studies On Desulfurization Of Thiophenic Sulfur In Gasoline With Cu₂O/SiO₂ And Cu₂O/SiO₂-M_xO_y（M=Al、Ti） Aerogels

The π-complexation force is a weak chemical force,Which occurs between the transition metal ions with(n-1)d10ns0 configuration and the molecules with π bonds.The empty s-orbitals of the transition metal ions and the π bonds of the molecules form the usual a bonds.At the same time,the d electrons of the metal ions can feed back to the antibonding π-orbitals(π*)of the molecular,form the σ-π bonds.It is found that the strength of the π-complexation is stronger than that of the van der waals forces and weaker than that of the uaual chemical force bonding,the π-complexation could be broken by increasing temperature or reducing pressure.Therefore,the absorbents containing π-complexation exhibited an excellent absorption selectivity as well as a high regeneration adsorption performance.Thiophene and its derivatives in fuel oil are difficult to be removed by hydrodesulfurization(HDS).In many non-hydrodesulfurization processes,the selective adsorption desulfurization with good selectivity,lower operating costs and mild conditions,is currently the most promising desulfurization technology.The most important part in adsorption desulfurization technology turns to be the adsorbent,aerogels due to its high porosity,high surface area,thermal stability and high low density,become an excellent adsorbent.In this paper,Cu2O/SiO2 and Cu2O/SiO2-MxOy(M=Al or Ti)aerogels were prepared by sol-gel and atmosphereic pressure drying method to adsorb the thiophene and benzothiophene in gasoline.The adsorption performance of these threeπ-complexation absorbents on thiophene and benzothiophene in model gasoline,the effect of benzene and cyclohexene on the adsorption performance of thiophene and benzothiophene were investigated through stactic adsorption and dynamic adsorption respectively.Meanwhile,the adsorption mechanism of absorbents on thiophene and benzothiophene and the key factors of adsorption performance were explored by XRD,XRF,BET,SEM and TPR characterization methods.The results showed that stactic adsorption performance of Cu2O/SiO2 aerogels belongs to the Langmuir isotherm model.With a molar ratio of 50:1 to Si/Cu Cu2O/SiO2 aerogel had a highest adsoption capacity for thiophene,15.2 mg S/g、13.6 mg S/g at 25 ℃ or 60 ℃ respectively.The dynamic adsorption performance of these three π-complexation absorbents on thiophene and benzothiophene in model gasoline,along with increased content of Cu、Al and Ti，the adsorption capacity of thiophene and benzothiophene comes to the summit,then falls.The maximum breakthrough adsorption capacities to the thiophene and benzothiophene of Cu2O/SiO2 aerogel with a molar ratio of 50:1 to Si/Cu are 4.8 mg S/g,5.8 mg S/g respectively.And The thiophene and benzothiophene maximum breakthrough adsorption capacities of Cu2O/SiO2-Al2O3 aerogel with a molar ratio of 9:1 to Si/Al are 7.9 mg S/g and 9.2 mg S/g.The thiophene and benzothiophene maximum breakthrough adsorption capacities of Cu2O/SiO2-TiO2 aerogel with a molar ratio of 30:1 to Si/Ti are 11.6 mg S/g and 12.7 mg S/g.Owing to the Strong π electron density of benzene or cyclohexene,the presence of benzene or cyclohexene in model gasoline,can greatly compromise desulfurization performance of the all three aerogels above.Washed with benzene and n-heptane solvent,the regenerated adsorption capacity of the first time of Cu2O/SiO2-50:1 can be restored to 70.83%of the fresh absorbent,which meawhile for the Cu2O/SiO2-Al2O3-9:1 and Cu2O/SiO2-TiO2-30:1 are also 70%around.Then it comes to a conclusion that after introducing the Al or Ti atom into the aerogel’s skeleton,the capacities of aerogels to thiophenic sulfur were significantly enhanced due to the π-complexation and the acid-base interactions.