| The problem of air pollution is becoming more and more serious in cities, and the emission of automobile exhaust is one of the sources of pollution. Reduction of sulfur oxide emissions from automobile exhaust is very important for improving air quality. And reducing sulfur content in gasoline is an effective way to control the emissions of sulfur oxides.Catalytic hydrogenation is the main method for gasoline desulfurization, but the removal efficiency of thiophene and its derivatives with high stability is very difficult. The operating conditions of adsorption method are mild, which do not reduce the octane number of gasoline and can remove sulfide deeply. The particle size of the traditional adsorbent is generally between the millimeter and centimeter level, and the resistance of mass transfer is very large. So the separation of sorbent from gasoline will be difficult if it is not moulding a certain shape. On the contrary, the magnetic nano adsorbent is fast and easy to be separated and recovered. Based on this, Ag/Fe3O4@ SiO2, a magnetic nano adsorbent with the core-shell structure was synthesised to remove the sulfur in gasoline deeply. Investigating the influencing factors of the preparation process of Fe3O4 and Fe3O4@ SiO2, and optimize the process. The adsorbent was prepared by the impregnation method to load the active component. The sulfur in commercially available gasoline was removed by static adsorption method and its desulfurization efficiency was investigated.Firstly, monodisperse magnetic nanoparticles Fe3O4 were prepared by the solvent thermal method. Some influence factors, for example reactant concentration, concentration of sodium citrate, sodium acetate concentration, iron concentration, reaction time and reaction temperature were investigated. Analysised the reasons and found that the magnetic Fe3O4 nanoparticles were prepared at 200℃ for 10 h when ethylene glycol was 60 mL, anhydrous ferric chloride was 12 mmol, sodium acetate was 36 mmol and anhydrous citric acid sodium was 3 mmol. The morphology of magnetic Fe3O4 nanoparticles made in this condition was the most regular and particles were uniform spherical particles. The diameter of it was about 140 nm, and it has good magnetic response, and the magnetization is as high as 53.2 emug-1.Then take the prepared uniform size, spherical Fe3O4 nanoparticles as the core, using CTAB as the template, TEOS as silicon source, ammonia as catalyst, Fe3O4 particles were coated on porous SiO2 by Stober method. And the effect of amount of CTAB, TEOS and adding quantity of ammonia dosage, reaction time, reaction temperature and stirring speed on the specific surface area, pore size and thickness of composite microspheres coated core shell structure have been analyzed. The intrinsic reasons were analyzed and the morphology of the composite microspheres Fe3O4@ SiO2 with uniform morphology and complete coating was prepared, and its specific surface area is as high as 529 m2/g and the pore size is about 2.3 nm.Finally, different carriers were impregnated by silver nitrate solution to load the active component and commercially available 93 # gasoline was carried out by static adsorption desulfurization to investigate its desulfurization effect. The result show that, when ratio of catalyst and oil is 0.13 g/mL, Ag/Fe3O4@ SiO2 core-shell magnetic nano adsorbent can decrease sulfur from 44.7 ppm to 4.5 ppm. The sulfur content in gasoline reached the national standard for motor gasoline fifth stage in our country to implement the requirments of sulfur content in less than 10 ppm. |
PDF Full Text Request