摘要: A series of NiWF (x)/γ-Al2O3 catalysts were prepared by adding different amounts of ammonium fluoride, and the effects of fluoride amount on the structure and physicochemical properties were investigated with X-ray diffraction, X-ray photoelectron spectroscopy, NH3-TPD and high resolution transmission electron mcroscopy (HRTEM) techniques and N2 sorption experiment. Their hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) catalytic performances were evaluated in a fix-bed reactor with low and middle-temperature coal tar obtained from Inner Mongolia as feedstock. Although fluoride amount has little effect on the pore diameter and pore volume of the catalysts, increase of the fluoride amount decreases the specific surface area. In addition, the sulfidation degree of the catalyst decreases with the fluoride amount when it is sulfided at 643 K for 6 h. Also, the numbers of strong acid sites and total amount acid sites change with increasing fluoride amount. They slightly increase at first, but then obviously decrease. HRTEM shows that WS2 slabs have a typical layered structure. The catalytic activity of NiWF (x)/γ-Al2O3 for HDN and HDS of coal tar shows a volcanic trend with the fluoride amount.
摘要: Generally, the process for synthesis of hierarchical-structured ZSM-5 zeolite is complex. Here, the polygonal three-dimensional ZSM-5 zeolite with hierarchical structure was hydrothermally synthesized by one-step synthesis method with dual templates. The effects of crystallization conditions and synthesis gel compositions, including crystallization temperature, crystallization time, Si/Al molar ratio, on the products were investigated for optimizing synthesis conditions. The X-ray diffraction (XRD), N2 adsorption-desorption experiment, Pyridine adsorption FT-IR (Py-FTIR), scanning electron microscopy (SEM) and transmission electron microscope (TEM) were used to characterize the crystalline structure, pore structure, surface acidity and crystal morphology of products. It was shown that the hierarchical-structured ZSM-5 zeolite can be synthesized under the following conditions: crystallization temperature of 160-180℃, crystallization time of 24-96 h, the SiO2/Al2O3/Na2O/CTAB/TPABr/H2O ratio of 1/x/0.4/0.05/0.12/280, (x: 50-240). The sample crystallized at 160℃ for 48 h with a synthesis gel having a Si/Al molar ratio of 50 had uniform cylindrical crystal morphology, high crystallinity and ordered mesoporous structure with a pore diameter of 3.60 nm. It contains both strong Brønsted and Lewis acid sites at 300℃, which contribute to its catalytic properties.