Mgo Substrate. The Fcc Process Sulfur Transfer Agent

In recent years,with the enhancement in environmental protection, the SOx incremental pollutions brought about the widely attention in every country. Sources of SOx pollution are very popullar, among which main roots are from industrial production process. SOx from refinery factories is about 6-7%of total SOx releases in atmosphere, but SOx from the feed stock of fluld catalytic cracking(FCC) process is about 5%. So the reasearch of desulfurization techniques in FCC is significant.In the paper, coprecipitations were adopted in the preparation of MgO based sulfur transfer absorbents(STC) added with minor promoters, based on the key issue of construction and performance of sulfur-transfer absorbents, the performance of desulfurization and regeneration of sulfur transfer absorbents were studied, and physical and chemical, as well as structural factors that affect desulfurization performance(DP) were discussed.Rare earth elements cerium(Ce), lanthanum(La), and transient metal elements iron(Fe), copper(Cu), zinc(Zn) and manganese(Mn) were respectively doped into MgO as the additive to study the DP of them, and SO2 was chosen as object contamination. The results indicated that, the DP of MgO indoped with Ce is about 10 times of undoped and indoped with other elements.The DP of MgO indoped with Fe, Cu, Zn is better. Using one step response surface method(RSM) to choose the optimal composition of the STCs of MgO indoped with two promoters of Ce and Fe, Cu, Zn when the STCs DP is best. Finally, the DP of MgO-Ce-Fe is best and its sulfur capacity is 1.60 gSO2/g absorbent.In the research on the regeneration performance(RP) of MgO-Ce-Fe, MgO-Ce-Cu and MgO-Ce-Zn, it could be found that beacause regeneration temperature of MgO-Ce-Cu and MgO-Ce-Zn are higher, and their regeneration rate are smaller, so they are unsuitable as STCs. But MgO-Ce-Fe can be regenerated in lower temperature quickly and completely. The sulfur capacities were 62.2%of fresh STCs after ten times sulfuration and regeneration. MgO-Ce-Fe has best regeneration performance.X ray diffraction(XRD), Special surface area, pore structure and FT-IR and other characterization means were adopted in the structure analysis of the upper three STCs before and after reaction. Compared with pure MgO, MgO indoped with promoters decreased in particle size, and increased in special surface area and pore volume. Especially the exchange extent is very obvious adulterating Fe2O3. Morever, there was CeO2. All of characteristics are positive to improve the STCs DP and RP. On the contrary, because of emerging blocks in STCs pores, special surface area and pore capacity decrease much after first desulfurization, and there is much particles reunion in them. There is much difference MgO-Ce-Fe after regeneration desulfurization.After the regeneration of MgO-Ce-Fe, the average pore size, species states, special surface area and pore capacity doesn't change obviously comparing with fresh STCs.Results showed that MgO was the only active material for SOx adsorption, Fe2O3 was not only the absorbent for oxidatlng SO2 to SO3, but also the absorbent for reducing MgSO4, CeO2 was a very nice absorbent for oxidating SO2 to SO3, but had no contribute to the reduction of MgSO4.This work will provide the valued data and theoretie bases for the application in reasearch of sulfur transfer additive.