Research On Performance At Low Temperature And The Mechanism Of Reactive Adsorption Desulfurization Of NiO/ZnO-Al₂O₃-SiO₂

Reactive Adsorption Desulfurization(RADS)process is an important method for producing national V and VI standard low-sulfur gasoline.Low-temperature RADS process can greatly reduce the energy consumption of the unit,reduce the surface coking of adsorbents,and improve the service life of adsorbents.Firstly,the desulfurization performance of a NiO/ZnO-Al2O3-SiO2 adsorbent for a simulated gasoline(thiophene+n-hexane)at different reaction temperatures was investigated.It was found that the desulfurization performance of the NiO/ZnO-Al2O3-SiO2 adsorbent showed a special trend of first decreasing and then rising at lower reaction temperatures(300 ℃),then maintained a higher desulfurization level,which was significantly different from the desulfurization performance curves at higher temperatures(400 ℃ and 420 ℃).When the reaction temperature of RADS is 300 ℃,the chromatographic analysis results show that the content of CH4,C2H6 and C3H8 in the pyrolysis tail gas is very small.The effects of different carrier gas and space velocity on the desulfurization performance of adsorbent at 300 ℃ were investigated.The results show that in N2 atmosphere,adsorbents show considerable desulfurization activity,but the desulfurization performance decreases continuously with the reaction.In H2 atmosphere,mass space velocity does not affect the shape of the desulfurization rate curve greatly.The effects of high temperature pretreatment,hydrocarbon pretreatment and simulated gasoline pretreatment on the desulfurization performance of the adsorbent at 300 ℃ were further studied.It was found that the desulfurization performance of the adsorbent at 300 ℃ could be effectively activated by the above pretreatment methods,among which the alkane feed pretreatment at 420 ℃ was the best.Finally,XRD,H2-TPR,TOPT and XPS were used to characterize the adsorbents before and after reaction under different carrier gases and reduction conditions.Combining with the reaction results of mechanical mixtures of Ni3S2 and ZnO-Al2O3-SiO2 powders under different carrier gases,it was considered that the surface active component NiO of adsorbent was unlikely to be reduced to elementary Ni in the reaction process.These indirectly proved that NiO in adsorbents had desulfurization activity.There are different reaction paths in the RADS process.Based on such fundings,the mechanism of reaction adsorption desulfurization process with NiO as active center is proposed,which provides theoretical support for the preparation and development of new adsorbents and the optimization of RADS process.