Selective Hydrodesulfurization Of Full Range Fluid Catalytic Cracking Gasoline At Low Temperature

Fluid catalytic cracking (FCC) gasoline contributes more than 80% of commercial gasoline in China, FCC gasoline contains very high levels of olefins and sulfur compounds, which provides over 90% sulfur compounds and almost all of the olefins for the commercial gasoline. The new catalytic cracking technology such as MGD, MIP and FDFCC technology have been developed successfully to decrease olefins. Also the combined application of new FCC catalysts and additives make the olefin content in FCC gasoline well controlled. At present, the FCC gasoline is mainly suffering from the high sulfur content. The sulfur content of the FCC gasoline can be reduced effectively by using traditional hydrotreating catalysts. But the hydrotreating process will inevitably decrease the olefins content leading to serious loss of RON, that will do harm for the application and economy profit of the clean gasoline.The main purpose of this thesis is to develop a selective hydrodesulfurization catalyst which has high desulfurization activity and low olefin saturation activity at low temperatures (250℃), for full-range FCC gasoline. TS-1 and SiO2 were used as HDS catalysts which were modified by metal oxides and third component TiO2, EDTA. The performances of the catalysts in the selective HDS of full-range FCC gasoline were investigated at different temperatures and WHSV. Reaction conditions of selective hydrodesulfurization catalyst DQG0905-5 were investigated on small fixed-bed reactors. The main conclusions were shown as follows:1. The experimental results showed that the olefin hydro-saturation could be reduced by appropriately increase of reaction WHSV and hydrogen/oil ratio, as well as by appropriately decrease of reaction pressure and temperature. Improvement of hydrodesulfurization selectivity of DQG0905-5 catalyst would be achieved by changing reaction conditions. The best result is:desulfurization rate of 84%, olefin saturation rate of 14%, under reaction temperature 250℃, reaction pressure 1.0 Mpa, WHSV 2.0 h"1, hydrogen/oil ratio 630, the final clean gasoline sulfur content is less than 40 ppm, RON loss is less than 2 unit and liquid yield is more than 99%.2. TS-1 is an effective catalyst for selective hydrodesulfurization, It's unique acidic can catalyze desulfurization, and keep the low olefins saturated rate at the same time. TS-1 is a good support for the active component. It has a large specific surface area, suitable pore volume and size, so makes the sulfur compounds of FCC gasoline easily diffuse in the channels, and provides enough spaces for hydrodesulfurization reaction.3. The desulfurization activity of TS-1 catalyst is sensitive to temperature and WHSV, however, the olefin hydrogenation activity is not sensitive to temperature and WHSV. After promoted with Co-Mo, TS-1 get excellent hydrogenation selectivity (Δ＞53%) with low olefin hydrogenation activity (HDO≤20%) at high temperature (≥320℃). EDTA promoted Co-Mo/TS-1 improved the catalyst with good property at low temperature (250℃).4. Compared with traditional supported alumina HDS catalysts, supported silica catalysts have better selective hydrodesulfurization performance. Co-Mo/SiO2 catalyst showed a strong desulfurization capacity (HDS＞71%) and excellent hydrogenation selectivity (Δ≥46%) at high temperature (340℃). Co-Mo/SiO2 catalyst is sensitive to temperature and WHSV. After introduction of the third component TiO2, EDTA, the selective hydro-upgrading performance of Co-Mo/SiO2 catalyst is effectively improved with high desulfurization activity and good selective hydrogenation at low temperatures (≤270℃).