| Organosulfur compounds in fuel not only corrode the engines of vehicles and industrial equipments,but also produce SOxduring the combustion process,causing environmental pollution problems such as urban smog and acid rain,and thus endangering the health of human life.Therefore,many countries have raised great concerns for environmental remediation and mandated strict regulations to limit the sulfur concentration in transportation fuels in recent years.Compared with traditional hydrodesulfurization technology,adsorption desulfurization technology is considered to be one of the most promising non-hydrodesulfurization technologies due to its characteristics of mild reaction conditions,low equipment investment and operation cost,and its ability for selective ultra-deep desulfurization.In previous work,our research group prepared a low-cost dual-function Ti O2/silica gel adsorbent based on the catalytic oxidation-adsorption coupled desulfurization mechanism and realized the ultra-deep desulfurization of real diesel.The dual-funtional adsorbent can act as catalyst and adsorbent,which can catalytically convert organosulfur compounds into sulfones with the aid of cumene hydroperoxide,and then adsorb the sulfones with high selectivity and capacity.Notably,this approch can overcome bottleneck problems such as low adsorbent selectivity and poor desulfurization performance caused by competitive multi-component adsorption in real diesel.However,considering the problems of large pressure drop,low mechanical strength,and easy loss of the powdered adsorbents during the industrial process,this article used pseudo-boehmite as a binder to prepare dual-function Ti O2/silica gel extrudates by extrusion molding,and was based on catalytic oxidation-adsorption coupled desulfurization mechanism explored its desulfurization kinetics and regeneration performance for real diesel.The results showed that the desulfurization process of the real diesel by the Ti O2/silica gel extrudates conformed to the first-order kinetic model,and the kinetic model of the CN2extrudates is ln?C?=–9.42×10-3t+3.84.In addition,the static saturated adsorption capacity of the Ti O2/silica gel extrudates hardly decreased??1.6 mg-S/g-A?and the particle size Lphad a linear relationship with the desulfurization kinetic rate constant k.This article also investigated the dynamic desulfurization process of the Ti O2/silica gel extrudates,and the dynamic curves fitted the mathematical model of the two-stage process of dynamic coupled desulfurization proposed previously.The CN2extrudates can reduce the sulfur concentration in the diesel from 50 ppm to 10 ppm,the desulfurizaion capacity reached 75.3m L-F/g-A.By comparing the parameters of fixed bed such as packing density and mass space velocity in different dynamic desulfurization processes,it was found that the dynamic desulfurization rate constant of the Ti O2/silica gel extrudates were affected by the mass space velocity,which was the residence time of the organosulfur compounds in the diesel on the surface of the material.In addition,the kinetics of adsorbed diesel desorption in the adsorbent conformed to the first-order kinetic desorption model,and the kinetic desorption rate constant increased with increasing temperature.When the temperature of nitrogen purge>150?,the total diesel yield can reach more than 99.5%.In this paper,the regeneration performance of the CN2extrudates were investigated by high-temperature nitrogen/air calcination and solvents elution,and it was found that there was almost no loss of adsorption capacity after20 cycles over adsorption-air thermal regeneration.The adsorption capacity after 6 cycles over adsorption-methanol regeneration can still reach 92%of the initial desulfurization performance.In this paper,different kinds of supported adsorbents were prepared for the problems of traditional gasoline desulfurization technology that cannot reduce the total sulfur concentration of gasoline or the difficulty of regeneration of spent alkaline liquid and environmental pollution and their adsorptive desulfurization performance for 500 ppm n-heptanethiol in model gasoline was investigated under ambient conditions.Results showed that Cd?OH?2/SBA-15 showed superior adsorption performance for selective mercaptan removal,which achieved the removal of mercaptan by forming salts with mercaptans.In addition,we also investigated the effect of Cd?OH?2loading on adsorption capacity of Cd?OH?2/SBA-15.It was found that the sulfur capacity of Cd?OH?2/SBA-15 material increased with the increase of active component,and once the loading of Cd?OH?2up to 20%,the adsorption capacity began to decrease.It is presumably because the active component on the surface of the material agglomerated and blocked the pores under high loading.The N2adsorption isotherm characterization results showed that the 14%Cd?OH?2/SBA-15-4.9material with the highest specific surface area exhibited the highest adsorption sulfur capacity?47.8 mg-S/g-A?,which may attributed to the exposure of more adsorption active sites.Taking 14%Cd?OH?2/SBA-15 as the research object,it was found that the adsorption capacity of the adsorbent decreased slightly with the increase on the size of the normal mercaptan,implying the neglect effect of the size of normal mercaptan on the adsorption performance.Nevertheness,the adsorption capacity of isomeric mercaptan over 14%Cd?OH?2/SBA-15dropped significantly compared to normal mercaptan,which may due to the steric hindrance effect.From the adsorption isotherm of n-heptanethiol,the saturation adsorption capacity of the material can reach 63.96 mg-S/g-A,and when the concentration of mercaptan in the fuel was only 5 ppm,the adsorption capacity reached 16.45 mg-S/g-A. |
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