Deep Desulfurization Of Fluid Catalytic Cracking Gasoline

The removal of sulfur compounds has became more and more urgent since the increasingly stringent environmental regulations implemented by government worldwide. In China, No. III emission standards have been executed in which less than 150μg/g of sulfur content in gasoline is required. With the Olympic Games approaching, several cities have implemented Europe IV standard ,the sulfur content must be reduced to below 50μg/g.On the other hand, ultra-low-sulfur fuel is also needed for on-site or on-board use with a fuel cell system. For fuel cell applications, the sulfur content in gasoline must be reduced to less than 0.1μg/g for PEMFC and less than 10μg/g for SOFC. In China, 80% of gasoline comes from FCC processes in which the sulfur and olefin content is high.The major problem for deep desulfurization is that the conventional hydrotreating technology results in a significant reduction of octane number due to saturation of olefins from fluid catalytic cracking.Based on the above investigations, the HDS and adsorption flow were combined to deeply remove sulfur content in the FCC gasoline, at the same time decreased the olefin content and kept the octane value unloss. In the experiment, we got following conclusions:(1) DOS catalyst was prepared and evaluated for desulfurization of FCC gasoline for 1116 h. The result showed that the catalyst exhibited strong ability to reduce sulfur and olefin content and kept the stability throughout the process. The desulfurizing ability increased when the temperature rised and at the same time aromatization activity also increased.The RON of product lost a lot compared with feed.(2) The heteropoly acid PMo and Ni loaded on nano HZSM-5 was prepared and used in the FCC gasoline desulfurization for 100 h. After hydrotreatment, the sulfur content decreased from 220μg/g to below 50μg/g, the olefin content decreased from 33.8vol.% to 11.5 vol.%; the aromatic content increased from 17vol.% to 19.7 vol.%. Mass balance calculation showed that the process has hige gasoline yield (98 wt.%);(3) Y zeolite had been chosen as adsorbent. CuY zeolite had been prepared and used in the desulfurization process. The breakthrough curve showd the breakthrough and saturation amount was 8.5mgS/g and 57.5mgS/g, respectively. We found the adsorptive selectivities to different sulfur compounds were consistent with the electron density of sulfur atom.