Preparation And Performance Evaluation Of Adsorbents For Gasoline Deep Desulfurization

Deep desulfurization of transportation fuels is receiving increasing attention in the research community worldwide due to increasingly stringent regulations and fuel specifications in many countries for an environmental protection purpose. In terms of technology availability, the sulfur content in gasoline can be reduced by conventional hydrotreating desulfurization processes. The major disadvantages of the conventional hydrotreating technology for gasoline deep desulfurization are higher losses of product yield and octane number, as well as higher operation cost. Consequently, development of new deep desulfurization processes for liquid hydrocarbon fuels becomes one of the major challenges to the refining industry.A new approach for deep desulfurization is to use adsorption to selectively remove organic sulfur compounds from liquid fuels. Adsorption desulfurization has several potential advantages: (1) the process is operated at ambient temperature and atmosphere, without using any H₂, which leads to low energy consumption, low investment and low operating cost;(2) the process is very effective for ultra-deep desulfurization of liquid hydrocarbon fuels;(3) there is no or quite less reduction of octane number. Key issue for the commercialization of deep adsorption desulfurization is to develop new adsorbents with higher sulfur capacity and stability.In the present study two kinds of adsorbents were prepared using impregnation method: Ag/13X and CuO/13X. Active components within the adsorbents were silver and copper(II) oxide respectively. The effects of preparation, adsorption and regeneration conditions on performance of the adsorbents were investigated and the suitable conditions were determined.The suitable preparation conditions of Ag/13X are: silver nitrate concentration 0.1mol/L, impregnation time 6h, drying temperature 100℃, and calcinating temperature 550 ℃. The suitable adsorption conditions are: ambient temperature and pressure, the adsorbent-oil ratio 5 ∶ 20, adsorption time 1h. The suitable preparation conditions of CuO/13X are: bluestone concentration 0.2mol/L, impregnation time 6h, drying temperature 100℃, and calcinating temperature 350 ℃. The suitable adsorption conditions are: ambient temperature and pressure, adsorbent-oil ratio5 : 20, adsorption time lh.Determined by dynamic adsorption experiments, the sulfur capacities of Ag/13X and CuO/13X are 4.85 and 3.99mg/g, which were 2.6 times and 2.1 times of the best value reported so far, respectively.The suitable regeneration conditions of Ag/13X were.- regenerated at 200°C about 3 hours and the flow velocity of nitrogen 1 OOmL/min. After regenerated for 5 times, the performance of the adsorbents regenerated for model gasoline was no obvious changes. However, the performance of the adsorbent regenerated for FCC gasoline declined sharply. It is possibly due to the interactions between non-ideal compounds in FCC gasoline and the active components onto the adsorbents. The reason need to be probe deeply in the following efforts.Preliminary analysis of mechanism of adsorption suggested the two adsorbents adsorbing thiophene and its derivatives mainly via 7i-complexation.