铜离子在CuLaHY分子筛中的分布与吸附脱硫性能

在空气气氛中采用等体积浸渍法制备了具有不同Cu担载量的CuLaHY分子筛吸附剂, 并用X射线衍射(XRD)、比表面积(BET)、X射线光电子能谱(XPS)技术对分子筛吸附剂进行了表征. 通过多晶XRD确定了Cu2+及La3+离子在Y型分子筛笼内的结构与分布, 并测定了分子筛吸附剂在含二苯并噻吩(DBT)的模拟柴油中的吸附脱硫性能. 结果表明, 前驱体CuCl2中的大部分Cu物种与LaHY分子筛进行了离子交换, 进入分子筛笼内, 极少部分Cu物种以CuCl形式高度分散在Y型分子筛的笼中. La3+离子及进入Y型分子筛笼中的部分Cu2+离子处于茁笼的SI'位, 而另一部分Cu2+离子与骨架氧和水分子配位, 并牢固地定位于Y型分子筛超笼中的SII及SIII位上. 处于超笼中SII及SIII位上的Cu2+离子对模拟柴油中的DBT分子具有吸附作用, 成为吸附脱硫的中心. 当模拟柴油中有萘存在时, 与DBT分子会产生竞争吸附.

Distribution of Copper Ions in a CuLaHY Zeolite and Its Performance in Adsorption Desulfurization

CuLaHY zeolite absorbents with different Cu loadings were prepared by the equal volume impregnation method under an air atmosphere. They were characterized by X-ray diffraction (XRD), BET surface area measurement, and X-ray photoelectron spectroscopy (XPS). The crystalline structure and distribution of Cu2+ and La3+ cations in the cages of the Y zeolite were determined by powder XRD. The performance of adsorption desulfurization for CuLaHY zeolite adsorbents was investigated using a model diesel containing dibenzothiophene (DBT). Results showed that a large amount of Cu from the precursor CuCl2 exchanged with the LaHY zeolite and entered the cages of the Y zeolite while a very small amount of Cu from the precursor CuCl2 was highly scattered in the cages of the Y zeolite in the formof CuCl. The La3+ cations and a portion of the Cu2+ cations entered the cages of the Y zeolite and situated at the SI' sites in the beta cages while another portion of the Cu2+ cations situated firmly at the SII and SIII sites in the supercages of the Y zeolites. They were coordinated to skeleton-oxygen atoms and water molecules. Cu2+ cations in the supercages can adsorb DBT molecules from the model diesel and thus become centers of adsorption desulfurization. However, naphthalene molecules will result in competitive adsorption with DBT molecules.