多级孔NiMo负载TS-1分子筛催化剂的制备及其加氢脱硫性能

Hierarchical TS-1 zeolite loaded with NiMo catalysts:Preparation and performance in hydrodesulfurization

钛硅(TS-1)分子筛的微孔孔道严重限制了其在复杂分子催化转化中的应用,为了克服这一问题,通过酸洗脱、碱刻蚀及二者相结合的方法制备了多级孔TS-1分子筛,并采用等体积共浸渍法制备了相应的NiMo负载型催化剂;使用X射线衍射(XRD)、N2吸附-脱附、吡啶吸附红外光谱(Py-FTIR)、氢气程序升温还原(H_(2)-TPR)、X射线光电子能谱(XPS)和高分辨透射电子显微镜(HR-TEM)等方法对多级孔TS-1分子筛的理化性质进行了表征;以二苯并噻吩(DBT)为探针对催化剂的加氢脱硫(HDS)性能进行了评价。结果表明,和常规TS-1分子筛相比,多级孔TS-1分子筛保持了MFI拓扑结构,比表面积增大且具有介孔结构,分子筛表面形成了适量的Br?nsted酸中心;相应催化剂上活性金属与载体间相互作用得以改善,MoS_(2)片晶长度和堆垛层数适宜,形成了更多的NiMoS活性相;催化剂活性和选择性均有所提升,尤其是酸洗脱获得的NiMo/AT-TS-1催化剂的活性相较未经处理的NiMo/TS-1催化剂提升了1.2倍,直接脱硫(DDS)路径选择性提升了22%。

The sole micropores strictly restrict the wide utilization of TS-1 zeolite in the catalytic fields,especially in the catalytic conversion of compounds with large molecular sizes.Here,we report a feasible and economical method to overcome this drawback.In this work,the hierarchical TS-1 zeolite was constructed via post-acid treatment,post-alkali etching,and a combination of post-acid treatment and alkali etching methods,after which,the corresponding NiMo-supported catalysts were prepared via the incipient wetness impregnation method.Then,the aforementioned materials were fully characterized using X-ray diffraction(XRD),N2 adsorption-desorption,pyridine adsorbed Fourier transform infrared spectroscopy(Py-FTIR),H_(2) temperature programmed reduction(H_(2)-TPR),X-ray photoelectron spectroscopy(XPS),and high-resolution transition electron microscope(HR-TEM)to unravel the changes in the physicochemical properties caused by the post treatments.Finally,the hydrodesulfurization of dibenzothiophene(DBT)was used as a probe to assess the effects of the post-treatments on the catalytic performance of the hierarchical NiMo/TS-1 catalysts.The results showed that the MFI topology of TS-1 zeolite remained undamaged significantly and the serial hierarchical TS-1 zeolites exhibited higher specific surface areas and mesopore structures.Moreover,appropriate amounts of Brønsted acid sites were formed at the surface of the serial hierarchical TS‑1 zeolites.The interaction between the active metals and the support materials was also modulated by the posttreatment of TS‑1 zeolite,which resulted in better dispersion of Ni promoted MoS_(2) slabs with a higher proportion of NiMoS active phase,further leading to the enhanced catalytic activity and direct desulfurization pathway selectivity of the corresponding serial hierarchical NiMo/TS‑1 catalysts.Among all the prepared catalysts,the catalytic activity was enhanced by approximately 1.2 times over catalyst NiMo/AT‑TS‑1 obtained by post‑acid treatment compared to that over catalyst NiMo/TS‑1 without treatment and on which the selectivity of the DDS pathway was 22%higher compared to that over catalyst NiMo/TS‑1.