Ti掺杂对Ni/ZnO-TiO2吸附剂用于FCC轻汽油脱硫性能的影响

Effects of Ti Doping on Ni/ZnO-TiO2 Adsorbent for Desulfurization Performance of FCC Light Gasoline

采用混捏法制备了不同Ti含量的ZnO-TiO2载体,采用等体积浸渍法制备了NiO/ZnO-TiO2汽油脱硫吸附剂前驱体,并采用X射线衍射(XRD)、压汞、NH 3程序升温脱附(NH3-TPD)、H2程序升温还原(H2-TPR)和H2程序升温脱附(H2-TPD)等手段对其进行了表征。以催化裂化轻汽油为原料,于氢气氛围下对NiO/ZnO-TiO2前驱体还原得到Ni/ZnO-TiO2吸附剂,在固定床上考察了Ti掺杂对该吸附剂脱硫性能的影响。结果表明:Ti的掺杂提高了Ni/ZnO吸附剂中活性组分Ni的分散度,增加了Ni活性位点,增强了吸附剂中强酸酸性及酸强度,Ti掺杂的吸附剂脱硫性能显著提高;Ti的掺杂能够减少游离Ni,有效抑制烯烃饱和;吸附剂脱硫性能随着Ti掺杂量的增加呈现先增强后减弱的趋势,当Ti掺杂质量分数为5%时,吸附剂具有最优脱硫性能,能够将FCC轻汽油中硫质量分数由300μg/g降低至5μg/g以下,穿透硫容为6.711%(每克吸附剂吸附硫67.11 mg),烯烃质量分数增加0.6百分点,降低了汽油辛烷值损失。

ZnO-TiO2 carriers with different Ti contents were prepared by the kneading method,and NiO/ZnO-TiO2 gasoline desulfurization adsorbent precursors were prepared by equal volume impregnation method.Afterwards,various methods,such as X-ray diffraction(XRD),Mercury intrusion porosimetry,NH3-temperature-programmed desorption(NH3-TPD),H2-temperature-programmed desorption(H2-TPD)and H2-temperature-programmed reduction(H2-TPR)were used to evaluate their performances.Using catalytic cracking light gasoline as raw material,NiO/ZnO-TiO2 precursors were reduced to Ni/ZnO-TiO2 adsorbents under hydrogen atmosphere,and the performance of adsorption desulfurization in FCC light gasoline was investigated.The results show that doping of Ti improves the dispersion of the active component Ni in the Ni/ZnO adsorbent,increases the number of Ni active sites,and enhances the acidity of adsorbents.Importantly,it is found that the desulfurization performance of the TiO2-doped adsorbent is remarkably improved,where,Ti doping reduces the content of free Ni,and suppresses the saturation reaction of olefin.The experimental results show that the desulfurization performance first increases and then decreases with the increase of Ti doping amount.When the doping mass fraction is 5%,the adsorbent shows the best performance,by which the sulfur mass fraction of 300μg/g in FCC light gasoline is reduced to below 5μg/g.The breakthrough sulfur mass fraction capacity is 6.711%,and percentage of the olefin mass fraction is increased to 0.6,declining the loss of RON.