Study Of Preparation And Adsorption Desulfurization Performance Of Ag₂O-SiO₂ And Ag₂O-SiO₂-GO Composite Areogel-like Adsorbents

Removal of thiophene and its derivatives from hydrocarbon fuels have the importantly scientific and practical significance for solving the more stringent environmental problems and promoting the fuel cell applications.Adsorption desulfurization via?-complexation,with low energy consumption,low cost,environment-friendly,and efficient removal of thiophene and its derivatives,was referred to as the most promising desulfurization method.Adsorbent is the key issue for adsorption desulfurization,so development of the new?-complexing composite adsorbents,with mesoporous structure,more exposed and highly dispersed active sites,and low cost,is the main research trend.Aerogel is a kind of three-dimensional porous network of solid materials formed by the mutual aggregate of nanoscale particles.Aerogel-type?-complexing adsorbents would be anticipated to exhibit excellent adsorption performance for the thiophene and its derivatives because of its special physical properties.In this paper,the Ag₂O-SiO₂ composite aerogel-like adsorbents synthesized with different conditions and the Ag₂O-SiO₂-GO aerogel-like adsorbents with different graphene oxide?GO?contents were prepared by sol-gel synthesis followed by ambient pressure drying technology.Their adsorption performance and mechanism for thiophene and its derivatives from model gasoline were investigated by equilibrium and breakthrough adsorption experiments,respectively.Moreover,the key factors affecting the adsorption performances were investigated by N₂adsorption-desorption,XRF,SEM and TEM.The results showed that the specific surface area and doping Ag⁺content of Ag₂O-SiO₂ composite aerogel-like adsorbents were the key factors that influence the breakthrough adsorption capacity.While with ageing temperatures from 25?to40?and ageing solution composition?ester/alcohol volumetric ratio?from 40/0 to20/20,their pore volume and average pore size also have some impacts on its breakthrough adsorption capacity.The Ag₂O-SiO₂ composite aerogel-like adsorbent synthesized at hydrolysis pH of 1.5,water/alcohol volumetric ratio of 4/10,ageing temperature of 40?,and ester/alcohol volumetric ratio of 15/25?i.e.Ag₂O-SiO₂@composite aerogel-like adsorbent?exhibited the best adsorption performance owing to its higher doping Ag⁺content,bigger specific surface area,pore volume and pore diameter.And the breakthrough adsorption capacity for thiophene?TP?and benzothiophene?BT?from model fuels,were 26.17 mgS/g and 33.19 mgS/g,respectively.In order to promoting the doping Ag⁺content and mechanical strength of Ag₂O-SiO₂@composite aerogel-like adsorbent,the Ag₂O-SiO₂-GO aerogel-like adsorbents were further synthesized.When the added GO content is 1.29 wt‰,the Ag₂O-SiO₂-GO adsorbent?i.e.Ag₂O-SiO₂-GO?1.29 wt‰?adsorbent?exhibited the maximum breakthrough adsorption capacity,which were 32.92 mgS/g and 39.57mgS/g for TP and BT,respectively.Cyclohexene,benzene,toluene and methyl tert-butyl ether?MTBE?in model fuels were found to have inhibiting effects on adsorption desulfurization over Ag₂O-SiO₂@composite aerogel-like adsorbent and Ag₂O-SiO₂-GO?1.29 wt‰?adsorbent.The coexistence of 10 wt%cyclohexene and10 wt%benzene showed the most strong decrease of breakthrough adsorption capacity for both of Ag₂O-SiO₂@composite aerogel-like adsorbent and Ag₂O-SiO₂-GO?1.29 wt‰?adsorbent which was reduced to 30%and 16.01%,respectively.The two adsorbents exhibited the excellent regeneration property by benzene-n-heptane solvent washing,and the fourth regenerated Ag₂O-SiO₂@composite aerogel-like adsorbent and Ag₂O-SiO₂-GO?1.29 wt‰?showing 79.87%,81.66%and 52%,39.53%of recovery in adsorption capacity for TP and BT,respectively.In addition,the kinetic results showed that the adsorption kinetic data of thiopheneoverAg₂O-SiO₂@compositeaerogel-likeadsorbentand Ag₂O-SiO₂-GO?1.29 wt‰?adsorbent were more in line with the pseudo-second order model compare to the pseudo-first order model.The adsorption equilibrium results showed that the adsorption equilibrium data of thiophene over of the two adsorbents were more in line with the Freundlich isotherm compare to the Langmuir isotherm.The thermodynamic results showed that the?G for thiophene over Ag₂O-SiO₂@composite aerogel-like adsorbent and Ag₂O-SiO₂-GO?1.29 wt‰?adsorbent were-5.63 kJ/mol and-5.51 kJ/mol,respectively.The negative values of?G indicates that the adsorption of thiophene on the two adsorbents are spontaneous.