Reactive Adsorption Desulfurization Performance And Mechanism Of Ca-doped NiO/ZnO-Al₂O₃-SiO₂ Adsorbents

Reactive adsorption desulfurization process plays an important role on producing standard V low sulfur gasoline.What the most important is the development of high performance desulfurization adsorbent.A Ca-doped NiO/ZnO-Al₂O₃-SiO₂ adsorbent was investigated for reactive adsorption desulfurization（RADS）and regeneration of gasoline.Various characterizations such as powder X-ray diffraction（XRD）,energy-dispersive spectrum（EDS）,O2-Temperature Programmed Oxidation（H₂-TPO）,NH3-Temperature Programmed desorption（NH3-TPD）are used to research the mian reason that the adsorbent has better desulfurization and regeneration performance after Ca modification.The results showed that Ca loading could promote the dispersity of active component NiO and ZnO on the surface of adsorbent support,which resulted in better desulfurization performance;and Ca doping could reduce the mediate-strong and strong acidity,which could decrease the carbon deposition on the adsorbent and contribute to the regeneration ability.Then,the effects of the reduction of the adsorbent,the reaction temperature and the mass space velocity（MSV）on the performance of gasoline desulfurization and pyrolysis were investigated by using simulated gasoline（n-hexane + thiophene）.The results showed that the presence of H₂ could improve the desulfurization and cracking performance of adsorbents;with the reaction temperature increasing,the cracking degree was also increasing;and the appropriate increase of MSV could reduce the cracking degree of simulated gasoline.At last,the RADS of a model gasoline was investigated over a NiO/ZnO-Al₂O₃-SiO₂ adsorbent in N₂ and H₂ and their desulfurization results were compared.The results showed that the adsorbent performed well when using N₂ as carrier gas.Carbon deposition on the surface is the main reason of the drop of desulfurization efficiency.This indicates that NiO could directly react with sulfur compounds in gasoline without the presence of H₂.Results of XRD,H₂-TPR,TOPT and XPS showed that NiO was difficult to be reduced under the conditions of RADS.RADS process may depends on NiO and Ni simultaneously to remove sulfur compounds and there was little NiS_x on the adsorbent.And a possible RADS mechanism was presented and discussed.