Effect of fluoride promoter on the catalytic activity of NiWF/γ-Al2O3 for hydrodenitrogenation and hydrodesulfurization of coal tar
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摘要: 制备了一系列添加不同含量F助剂的NiWF（x）/γ-Al2O3催化剂，并采用X射线衍射（XRD）、N2吸附、X射线光电子能谱（XPS）、NH3-TPD和高分辨透射电子显微镜（HRTEM）等手段对其结构和物化性质进行了表征，同时在固定床反应器上考察了其加氢脱氮（HDN）和加氢脱硫（HDS）活性，反应原料为中国内蒙中低温煤焦油。结果显示，随着F含量的增加，催化剂孔容和孔径没有明显变化，但比表面积减小。催化剂在643 K下硫化6 h后，其硫化度随着F含量的增加而减少，强酸位数和总酸位数呈现先略微增加后减少的趋势。高分辨透射电子显微镜测试表明，硫化后的催化剂中含有具有典型层状结构的WS2。F含量对NiWF（x）/γ-Al2O3的煤焦油HDN性能有较大影响，但对其HDS活性影响很弱。
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关键词:
- 加氢脱硫 /
- 加氢脱氮 /
- F /
- NiW/γ-Al2O3 /
- 煤焦油
Abstract: 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.-
Key words:
- hydrodesulfurization /
- hydrodenitrogenation /
- fluoride /
- NiWF/γ-Al2O3 /
- coal tar
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Figure 1 XRD patterns of catalyst
a: NiWF (0.00)/γ-Al2O3; b: NiWF (0.05)/γ-Al2O3; c: NiWF (0.10)/γ-Al2O3; d: NiWF (0.20)/γ-Al2O3; e: NiWF (0.50)/γ-Al2O3; f: NiWF (0.75)/γ-Al2O3; g: NiWF (1.00)/γ-Al2O3
Figure 2 Survey scanned ((a), (b)) and deconvoluted ((c), (d)) W 4f of NiWF (x)/γ-Al2O3 ((a), (c)) and Ni 2p ((b), (d)) XPS of sulfided NiWF (0.50)/γ-Al2O3 catalysts
a: NiWF (0.00)/γ-Al2O3; b: NiWF (0.05)/γ-Al2O3; c: NiWF (0.10)/γ-Al2O3; d: NiWF (0.20)/γ-Al2O3; e: NiWF (0.50)/γ-Al2O3; f: NiWF (0.75)/γ-Al2O3; g: NiWF (1.00)/γ-Al2O3
Figure 3 NH3-TPD profiles of catalyst
a: NiWF (0.00)/γ-Al2O3; b: NiWF (0.05)/γ-Al2O3; c: NiWF (0.10)/γ-Al2O3; d: NiWF (0.20)/γ-Al2O3; e: NiWF (0.50)/γ-Al2O3; f: NiWF (0.75)/γ-Al2O3; g: NiWF (1.00)/γ-Al2O3
Figure 5 HRTEM images of catalyst
(a): NiWF (0.00)/γ-Al2O3; (b): NiWF (0.05)/γ-Al2O3; (c): NiWF (0.10)/γ-Al2O3; (d): NiWF (0.20)/γ-Al2O3; (e): NiWF (0.50)/γ-Al2O3; (f): NiWF (0.75)/γ-Al2O3; (g): NiWF (1.00)/γ-Al2O3
Figure 6 Distributions of WS2 slab layer-stacking number in different sulfided NiWF (x)/γ-Al2O3 catalysts
Figure 7 Distributions of WS2 slab length in different sulfided NiWF (x)/γ-Al2O3 catalysts
Figure 8 Catalytic results of NiWF (x)/γ-Al2O3 for HDN and HDS of coal tar
(reaction conditions: t=380 ℃, p=8.0 MPa, LHSV=0.3 h-1, H2/oil=1 500)
Table 1 Pore structural parameters of NiWF (x)/γ-Al2O3 catalysts
Catalyst A/(m2·g-1) v/(cm3·g-1) d/nm NiWF (0.00)/γ-Al2O3 174.2 0.406 9.3 NiWF (0.05)/γ-Al2O3 163.2 0.399 9.8 NiWF (0.10)/γ-Al2O3 162.7 0.399 9.9 NiWF (0.20)/γ-Al2O3 162.5 0.402 9.9 NiWF (0.50)/γ-Al2O3 162.4 0.397 9.8 NiWF (0.75)/γ-Al2O3 154.2 0.397 10.3 NiWF (1.00)/γ-Al2O3 152.5 0.402 10.5 
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Table 2 Binding energy and sulfidation degree of W and Ni species on the catalyst surface
Catalyst NiWF (0.00) NiWF (0.05) NiWF (0.1) NiWF (0.2) NiWF (0.5) NiWF (0.75) NiWF (1.00) WS2 EB4f7/2 /eV 32.5 32.5 32.5 32.5 32.5 32.5 32.5 Relative content w/% 60.50 55.96 51.64 50.35 47.25 38.37 33.41 WO3 EB4f7/2 /eV 35.9 35.9 35.9 35.9 35.9 35.9 35.9 Relative content w/% 39.50 44.04 48.36 49.65 52.75 61.63 66.59 NiS EB2p3/2 /eV 854.2 854.2 854.2 854.2 854.2 854.2 854.2 Relative content w/% 52.89 47.31 42.38 39.34 27.49 24.52 19.37 NiO EB2p3/2 /eV 856.2 856.2 856.2 856.2 856.2 856.2 856.2 Relative content w/% 47.11 52.69 57.62 60.66 62.51 75.48 80.63
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