Research On The Catalytic Strippering Technology Producing Ultra-low Sulfur Clean Diesel

Development and utilization of ultra-low and even sulfur free diedel oil is a trend of clean fuel in the world. Peking began to enforce Europe Fuel Regulation StandardⅢ,in which sulfur content is required lower than 350μg/g after July, 2005. Further it will be decreased to 50μg/g after July, 2008. And then this rigorous specification will be carried out after July, 2010 in whole china. The existing diesel criteria of our country has a definite gap with the developed countries. Enactment and enforcement of new clean fuel and quickly joint track with the international is required.The conventional hydrodesulfurization (HDS) reactor encountered an ever been enormous difficulty and challenge in producing ultra low sulfur diesel, which is due to the accumulation of H2S, a byproduct in HDS under cocurrent down flow of the gas and liquid , and leads to poison the catalyst and prohibite the HDS reaction. It is known that 0.0006MPa of H2S partial pressure can result in 70% reduction of the HDS reaction rate.This paper proposed a countercurrent flow operation (catalytic stripping technology) which was deduced from the factors such as the default of now existing hydrogenation process, reaction order of HDS, the influence of react conditions and the adsorption equilibrium of H2S on the catalyst for deep removal of sulfur in diesel. Counter-current hydrogenation technology had a good solution to matching problem as temperature, hydrogen pressure and H2S adsorption. The advantage and necessity to gain ultra-low sulfur clean diesel by using countercurrent flow operation was justified from small and pilot plants'experiments.To cope with poor quality diesel such as catalytic cracking diesel and coker diesel, which containing high sulfur and high aromatic, single stage countercurrent ractor has a imperfect result in desulfurization and dearomatic extent. After adopting first cocurrent and second counter-current mode, clean diesel with sulfur content lower than 10μg/g can be produce. Thus existing plants can be used and lower investing cost was obtained.However, nonnoble metal catalyst in low H2S partial pressure atmosphere had poor...