Preparation Of Modified Montmorillonite And Study On Adsorptive Desulfurization Of FCC Model Gasoline

Gasoline desulfurization is of great significance to environmental protection. Adsorptive desulfurization is not only a highly efficient environmentally friendly way to remove sulphur from gasoline but also one of the current scientific research hot issues. Montmorillonites have abundant pores and are rich in China, especially in Inner Mongolia. So preparing adsorbents for the desulfurization of gasoline from montmorillonites not only is beneficial to the environment protection but also promotes the local economic development, and thus has a great potential to application.In this study, montmorillonites have been used as raw materials, and several kinds of modified montmorillonites have been prepared using the pillaring method by metal oxides, the hydrothermal method, the incipient-wetness impregnation method, the acid-treatment method, and the calcination in nitrogen gas method. The modified montmorillonites have been characterized by the X-ray diffraction (XRD), the nitrogen adsorption-desorption, the Fourier transform infrared spectroscopy (FⅡR), the scanning electron microscopy (SEM) equiped with an energy dispersive spectroscopy (EDS) and the transmission electron microscopy (TEM), and have been used to the experiment of the static adsorptive desulfurization of the FCC model gasoline. The factors that influence the desulfurization such as metal elements and their chemical environments including the raw clays, zirconia-modified clays, acid-treated clays and the carbon-modified clays, as well as the specific areas and temperture, are investigated and the mechanisms of adsorptive desulfurization have been briefly discussed. Specific research contents and main conclusions are as follows:1. M(Ag, Cu, Zn, Ni)-MMT adsorbents have been prepared by the pillaring method and the desulfurization perfromances of the adsorbents have been investigated. The results indicate that the Cu pillared clays exhibit the best desulfurization performance. A series of zriconia-modified clays ZrO2-MMTs with different zirconia content have been prepared by the hydrothermal method, and it has been found that there exists a weak interaction between thiophene and ZrO2-MMTs. The equilibrium adsorption capacity of thiophene of the adsorbent is proportional to its specific surface area and decreases with increasing the temperature, which belongs to the typical physical adsorption process. The adsorbent with 15 wt.% zirconium content has the largest specific surface area and thus the largest equilibrium adsorption capacity. The adsorbents of Cu-ZrO2-MMTs loading with 10 wt.% Cu have been prepared by the incipient-wetness impregnation method. It has been found that the equilibrium adsorption capacity increases with the increase of the specific surface area and pore volume of the adsorbent. The desulfurization rate of the adsorbent with 10 wt.% zirconia contant attains to 87.89% at 40℃. The equilibrium adsorption capacities of the adsorbent with 10 wt.% Cu and zirconia at temperatures higher than 40℃ are far larger than at 20℃ and it slightly decreases when the temperature increases from 40 ℃ to 80℃. There are strong interactions between thiophene molecules and Cu-ZrO2-MMTs, which might be resulted from the chemical adsoiption.2. The carbon-modified clays of C-hyd-MMT and C-carb-MMT have been prepared by the hydrothermal method and the calcination in nitrogen gas method, respectively, and the desulfurization results indicate that the C-carb-MMT is far better than the C-hyd-MMT at the same condition. The adsorbent of H-C-MMT prepared by the calcination in nitrogen gas method using the acid-treated clays as raw materials exhibits better desulfurization effect than the C-carb-MMT. The carbon content in the adsorbent has been modulated by controlling the amount of the precursor glucose, and it has been found that the adsorbent with 10 wt.% glucose has the largest equilibrium adsorption capacity of thiophene at 20 ℃, with desulfurization rate of higher than 94%. When the temperature changes from 20 ℃ to 60℃, the chemical adsorption dominates the process, and the adsorption capacity increases with increasing the temperature and the desulfurization rate attains to 99% at 60 ℃. When the temperature reaches 80℃, the balance of chemical adsorption is broken and the adsorption capacity sharply decreases.The FTIR results show that thiophene on the carbon modified montmorillonite has different adsorption sites.