Study On Reaction Adsorption Desulfurization And Olefin Hydrogenation On NiO/ZnO-Al₂O₃-SiO₂ Adsorbent At Moderate Temperature

The S-zorb desulfurization process of FCC gasoline is a typical reaction adsorption desulfurization(RADS)process,which is one of the main process for treating FCC gasoline in Sinopec.The processes has many advantages including low hydrogen consumption,low operating cost and low octane number loss of gasoline.It is of great significance to study the reaction characteristics of NiO/ZnO-Al2O3-SiO2 adsorbents at different temperatures.In this paper,the effect of decreasing reaction temperature on the desulfurization performance and hydrocarbon composition over NiO/ZnO-Al2O3-SiO2 adsorbent were investigated.It was found that NiO/ZnO-Al2O3-SiO2 adsorbent had good desulfurization performance and regeneration performance at 350?,which was about 80? lower than that of S-zorb reaction temperature,and the adsorbent had the higher breakthrough sulfur capacity and longer service life at this temperature.However,the hydrogenation saturation rate of olefins in oil products on adsorbents increases to a very high level at 350?.After that,for reducing the saturation rate of olefins in products,the space velocity,reactor pressure,and H2/oil rate ratio of the reaction at 350?were optimized.Results showed that the adsorbent has good desulfurization performance and low olefin hydrogenation saturation rate 23.3%under a reaction condition of 5.5h-1,2.9MPa and 40:1,respectively.The hydrogenation process of olefins on adsorbents was further investigated.Compared with long chain olefins,light olefins were more easily adsorbed on the active sites of adsorbents and easier to be saturated than long-chain olefins.The adsorption of sulfur-containing compounds and olefins were competitive reactions when they are adsorbed on the active sites,causing inhibition to each other between the RADS process and olefin hydrogenation saturation reaction.To reduce the octane number loss in the RADS process,the Ni loading on the adsorbent was also optimized.Results showed that the olefin saturation rate was reduced to 19.9%when the Ni loading was 15wt.%,while the adsorbent had good desulfurization performance.The calcination temperature of the adsorbents was further optimized,and BET,Py-IR,and XRD were employed to analyze the adsorbents formed at different calcination temperatures.Results show that the adsorbents prepared at 500? have good pore structure,surface acidity,and crystal structure,these lead to good desulfurization performance and low olefin hydrogenation saturation of the prepared adsorbents.Finally,the possible competition mechanism between RADS and olefins saturation in the process was proposed.There are three aspects impacting the competitive reactions,including active site number,olefin partial pressure ratio,and reaction temperature.The above research provides a certain theoretical basis for the RADS process to reduce energy consumption and improve efficiency.