(583fk) Study On the Reactive Adsorption of Thiophene On Modified Ni/ZnO-TiO2 Adsorbents By Addition of Al2O3, SiO2, ZrO2

In our previous study, reactive adsorption desulfurization (RADS) experiments were conducting over a series of commercial metal oxide supports (Al₂O₃-, SiO₂-, TiO₂- and ZrO₂-) supported Ni/ZnO adsorbents and it turned out that Ni/ZnO-TiO₂ showed the best desulfurization performance. In continuation of our earlier studies, modified Ni/ZnO-TiO₂ adsorbents by addition of Al₂O₃, SiO₂,  ZrO₂ were prepared by wet mixing method. The adsorbents were characterized by the N₂ adsorption-desorption, X-ray diffraction (XRD), temperature programmed reduction (TPR), and fourier transform infrared spectroscopy (FTIR). The prepared adsorbents were firstly pretreated by sufficient H₂ reduction to ensure Ni in the reduction state and then used in RADS experiments in a fixed-bed flow sorption system at the temperature of 400^oC, pressure of 1MPa, WHSV of 4h^-1 to evaluate the RADS performance. The results show that Ni/ZnO-TiO₂-ZrO₂ reveals the best RADS performance and the 3 hours accumulated sulfur capacity is 13.85 mg-S/g-sorbent. The RADS performance decreased in the following order: Ni/ZnO-TiO₂-ZrO₂ > Ni/ZnO-TiO₂-SiO₂ > Ni/ZnO-TiO₂-Al₂O₃ > Ni/ZnO-TiO₂ which is coincide with the order of the amount of total L acid according to the results of pyridine-FTIR. It is revealed that the RADS performance has a strong relationship to the amount of total L acid. XRD studies suggest that ZnAl₂O₄ and NiAl₂O₄ are present in Ni/ZnO-TiO₂-Al₂O₃ which indicate that there are interactions between ZnO, NiO and Al₂O₃. The formation of ZnAl₂O₄ and NiAl₂O₄ may affect the activity of adsorbent. The intensities of diffraction peaks for NiO and ZnO become stronger after adding SiO₂ into Ni/ZnO-TiO₂ which means the partical size of active components become larger. However, the BET surface area become much bigger after the addition of SiO₂ which may be one factor contribute to a better RADS performance than Ni/ZnO-TiO₂. The TPR profiles reveal that the reduction temperature of Ni/ZnO-TiO₂-ZrO₂ adsorbent is lower than other three samples implying Ni cations in ZnO-TiO₂-ZrO₂ support are easier to be reduced in the hydrogen reduction pretreatment and could obtain more active centers. After find out the high RADS performance adsorbent Ni/ZnO-TiO₂-ZrO₂, the optimal component proportion of support was investigated by adjusting the ratio of TiO₂/ZrO₂ and (TiO₂+ZrO₂)/adsorbent. The results reveal that the adsorbent showed the best RADS performance when TiO₂/ZrO₂ is 1 and (TiO₂+ZrO₂)/adsorbent is 50%.