Investigation of performance of Ni/W-USY/Al2O3 catalyst with full mesoporous in Fischer Tropsch wax hydrocracking
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摘要: 制备了富含介孔的Ni/W-USY/Al2O3催化剂并开展费托合成蜡加氢裂化实验,从反应性能、产品特性以及催化剂性质变化三方面对该催化剂进行评价。312 h运行实验结果表明,催化剂初始活性较高,120 h后趋于稳定,无明显失活现象,重质蜡转化率为73.95%时,轻质油选择性达到98.46%,裂解气以C3,4为主;石脑油、煤油、柴油为无色透明液体,以正构烷烃和甲基、多甲基取代的异构烷烃为主,异构烃含量分别达到63.98%、52.26%、48.90%;对反应前后催化剂分析发现,新鲜催化剂的金属分散性较好、介孔含量高,加氢活性中心以WS2、NiWS为主,随着反应由高活性到稳定阶段过渡,WS2部分迁移并与Ni形成更多Ni-S-W键,部分W-S键断裂释放出S后形成W-W键,使得稳定后催化剂的NiWS活性中心增加而WS2活性中心降低,并引起L酸密度降低而B酸密度增加。Abstract: Ni/W-USY/Al2O3 with full mesoporous structure was prepared and used for hydrocracking of Fischer Fropsch wax. The catalyst was evaluated for its reaction performance, product characteristics and catalyst properties change. In a 312 h experiment, the result showed that the catalyst possessed high initial activity, and maintained stable after 120 h, and did not show obvious deactivation afterward. When the heavy wax conversion reached 73.95% at the stable stage, the fuel oil selectivity reached to 98.46% and C3, 4 constituted the most cracked gas. Gasoline, kerosene and diesel, as the products, were transparent and composed of paraffins and iso-paraffins substituted by methyl-groups. The iso-paraffin contents in the three products were 63.98%, 52.26% and 48.90% respectively. The fresh catalyst contained two main active states of WS2 and NiWS, had good metal dispersion and rich mesoporous structure. With transition from high activity to stable state of the catalyst property, part of W migrated and formed more Ni-S-W bonds with Ni, and some W-S bonds broke to form W-W bonds after releasing S, resulting in the increase of active states of NiWS and the decrease of WS2, and forming more Brönsted acid sites and less Lewis acid sites.
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Key words:
- Fischer Tropsch wax /
- hydrocracking /
- catalyst /
- fuel oil /
- iso-paraffin
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表 1 催化剂DH的部分物理性质
Table 1 Physical properties of DH
Shape d/mm Length/mm Bulk density ρ/(g·mL-1) Cylinder 1.50 3.00-5.00 0.772 表 2 费托蜡的元素组成及性质
Table 2 Elemental composition and properties of Fischer-Tropsch wax
Element Content w/% H/C(atomic ratio) tSP/℃ Density /(g·mL-1) C H N S O F-T wax 85.01 14.53 0 0 0.46 2.05 76 0.756 Boiling range distribution 10% 20% 30% 40% 50% 60% 70% 80% 90% 192.5 234.0 287.5 370.0 442.5 491.3 534.3 588.4 652.7 表 3 产品的物化性质
Table 3 Physical and chemical properties of the products
Item Unit Naphtha Kerosene Diesel Chroma colorless/transparent colorless/transparent colorless/transparent Density ρ/(g·mL-1) 0.717 0.733 0.759 SP t/℃ - <-51 -26 Bromine w/(mg· (100 g)-1) 25.5 23.7 20.3 Sulfur w/% 0.0004 0.0006 0.0006 Calorific value Q/(MJ·kg-1) 47.17 47.03 47.48 Cetane number - - 71 Normal/isomerism m/m 36.02/63.98 47.74/52.26 51.10/48.90 Boiling range distribution 10% t/℃ 62 143 189 20% t/℃ 86 158 204 50% t/℃ 131 173 244 70% t/℃ 152 211 271 90% t/℃ 174 228 305 Final distillate t/℃ 199 241 348 表 4 催化剂的元素组成(XRF)
Table 4 Elemental composition of the catalysts (XRF)
Sample Content w/% WO3 SiO2 NiO Al2O3 Na2O SO3 DH 27.16 8.65 8.28 53.30 0.27 0 DH-R 27.26 8.67 8.38 53.30 0.21 0.74 表 5 DH催化剂的比表面积和孔结构
Table 5 Specific surface area and pore structure of samples
Sample Specific surface area A/(m2·g-1) Volume v/(cm3·g-1) dmeso/nm total micro meso total meso DH 208 74 134 0.307 0.261 31.1 DH-R 144 35 109 0.250 0.225 32.5 表 6 硫态化催化剂表面金属化学态分布比例
Table 6 Percentage of the surface metal species of sulfide catalysts
Sample w/% W0 W4+S W6+O Ni2+S Ni2+WS Ni2+O DH-S 18.05 51.05 30.90 23.52 22.53 53.95 DH-RS 21.74 49.26 29.00 19.08 32.76 48.16 表 7 DH-S和DH-RS的TG-DTA分析
Table 7 TG-DTA analyses of DH-R and DH-RS
Catalyst Lost weight w/% Ⅰ/(Ⅰ+Ⅱ)/% Exothermic Q/(kJ·g-1) Ⅰ/(Ⅰ+Ⅱ)/% Ⅰ Ⅱ Ⅰ Ⅱ Ⅰ+Ⅱ DH-S 11.10 10.51 51.37 0.81 2.13 2.94 27.55 DH-RS 2.01 7.08 22.10 1.24 1.32 2.56 48.43 -
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