Deactivation Investigation And Improvement Of FCC Sulfur Transfer Additives

Because heavier crudes with higher sulfur content are being processed, and the environment regulations become more and more strict, thus reducing the SOx emissions in the FCC flue gas has become a matter of urgency. As an effective method the research on the sulfur transfer additive technology has attract much attention, however, the systematic study about the catalyst deactivation are rarely reported. In this paper, studies on the deactivation investigation of FCC are carried out and the improvement methods are also presented.The deactivation of sulfur transfer additives including reduction process, the Kaolin’s influence and the influence of poisonous metal in the oil were studied. The regeneration activity of the commercial sulfur transfer additives prepared by spray drying technique was studied under different reduction conditions. During the investigation of reduction process, it is found that the reduction temperature, the regeneration time and the flow of H2 play an important role of the regeneration performance. Kaolin in the sulfur transfer additives could react with MgO to produce the Mg2SiO4 which leads to the deactivation of the catalyst. The influence of V2O5 and NiO content on DeSOx activity and the crystalline structure was studied. The result showed that the DeSOx activity and renewable performance remains stable and the crystalline phases intact when the content of V2O5 and NiO is under 5% and 3% respectively. Meanwhile, it is found that the sulfur transfer additives could trap vanadium thus to protect the zeolite in FCC catalyst from being destroyed because of the components in it such as MgO and CeO2 that form the stable new compounds such as Mg3(VO4) and Ce(VO4).In order to improve the defect of sulfur transfer additives, high surface area sulfur transfer additives are prepared by reversed-phase microemulsion method. The experiment results showed that the adsorption performance and reduction property were improved.In order to increase the mechanical strength of the magnesium aluminum spinel sulfur transfer additives, Kaolin is added into it. However, on the one hand the addition of kaolin decreases the content of active component, on the other hand MgO can react with kaolin to generate magnesium silicate which is hard to be reduced. In the condition of laboratory, a new type of sulfur transfer additive(MgTiO3 type) was prepared by reverse coprecipitation method. This kind of sulfur transfer additives has a high quality of mechanical strength and behaves well in the adsorption performance and reduction property. After a series of experiments, the structure of 0.15Ce/0.075Fe/MgTiO3·2MgO which shows the best adsorption and reduction performance is confirmed as the best structure.