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摘要: 本研究考察了不同载体(CeO2、ZrO2、MnO2、SiO2和活性炭)对负载型Ru基费托合成制烯烃(FTO)催化剂结构和催化性能的影响。结果表明,载体的本征属性和金属-载体相互作用(MSI)对催化性能有很大影响。在同一反应条件下的催化活性关系为:Ru/SiO2 > Ru/ZrO2 > Ru/MnO2 > Ru/AC > Ru/CeO2。对于烯烃选择性,Ru/SiO2和Ru/MnO2得到的总烯烃选择性最高,超过70%,而Ru/ZrO2催化剂的烯烃选择性低至29.9%。由于金属Ru与SiO2的金属载体相互作用较弱,反应后的Ru/SiO2催化剂得到适中的Ru纳米颗粒尺寸( ~ 5 nm)且反应活性也最高。对于Ru/AC和Ru/MnO2,其Ru纳米颗粒尺寸仅为1−3 nm,表现出较低的CO转化率。较高的烯烃二次加氢能力导致Ru/AC和Ru/ZrO2催化剂的烯烃选择性偏低。此外,由于存在强的MSI效应,部分Ru纳米颗粒被可还原性CeO2活性层包覆,导致Ru/CeO2催化活性最低。Abstract: The effects of supports (CeO2, ZrO2, MnO2, SiO2 and active carbon) on the structure and catalytic performance of Ru-based catalysts for Fischer-Tropsch synthesis to olefins (FTO) were investigated. It was found that the intrinsic characteristics of supports and the metal-support interaction (MSI) would greatly influence the catalytic performance. The catalytic activity followed the order: Ru/SiO2 > Ru/ZrO2 > Ru/MnO2 > Ru/AC > Ru/CeO2. As far as olefins selectivity was concerned, both Ru/SiO2 and Ru/MnO2 possessed high selectivity to olefins (>70%), while olefins selectivity for Ru/ZrO2 was the lowest (29.9%). Ru/SiO2 exhibited the appropriate Ru nanoparticles size ( ~ 5 nm) with highest activity due to the relatively low MSI between Ru and SiO2. Both Ru/AC and Ru/MnO2 presented low CO conversion with Ru nanoparticles size of 1−3 nm. Stronger olefins secondary hydrogenation capacity led to the significantly decreased olefins selectivity for Ru/AC and Ru/ZrO2. In addition, partial Ru species might be encapsulated by reducible CeO2 layer for Ru/CeO2 due to strong MSI effects, leading to the lowest activity.
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Key words:
- Fisher-Tropsch synthesis /
- syngas /
- olefins /
- Ru nanoparticles /
- support effects
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Figure 1 Detailed catalytic results over various supported catalysts (a): comparison of O/P and olefins total selectivity over various supported Ru-based catalysts, reaction condition for Ru/CeO2: 1 MPa, 3000 mL/(g·h), H2/CO=2, 300 °C, reaction condition for other catalyst: 1 MPa, 3000 mL/(g·h), H2/CO=2, 270 °C; (b)−(f): products distribution and cumulative olefins selectivity over various catalysts: (b) Ru/SiO2, (c) Ru/MnO2, (d) Ru/CeO2, (e) Ru/AC, (f) Ru/ZrO2
Table 1 Catalytic performance of various supported catalysts
Catalyst CO conversion /% Product selectivity /% ROH CO2 CH4 olefins C2 + paraffins Ru/SiO2 33.6 1.3 2.8 2.5 79.4 14.2 Ru/MnO2 12.0 4.9 10.2 4.4 70.1 10.4 Ru/CeO2a 8.3 8.3 21.5 12.4 49.7 8.1 Ru/AC 7.8 0.6 7.4 46.5 33.5 12.0 Ru/ZrO2 17.6 10.1 3.7 18.0 29.9 38.4 a: Reaction condition for Ru/CeO2: 1 MPa, 3000 mL/(g·h), φH2/φCO=2, 300 °C; reaction condition for other catalysts: 1 MPa, 3000 mL/(g·h), φH2/φCO=2, 270 °C Table 2 Texture property and Ru loading content of various catalysts
SBET /(m2·g−1) a Average pore
width /nm aRu 3p5/2 /eVb Ru /%c SiO2 279 23.6 − − MnO2 110 11.4 − − CeO2 88 7.3 − − AC 1438 2.1 − − ZrO2 83 3.1 − − Ru/SiO2 215 10.6 461.71 1.94 Ru/MnO2 69 14.4 462.28 2.28 Ru/CeO2 89 5.6 462.48 1.82 Ru/AC 1340 2.1 462.50 2.03 Ru/ZrO2 60 2.7 461.92 1.79 a: Particle physical property determined by BET test, b: BE of Ru 3p determined by XPS test, c: Ru content determined by ICP test -
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