Direct synthesis of LPG from syngas over Cu modified FeMg@SiO2 nano-level core@shell catalyst
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摘要: 本实验系统研究了纳米级核壳催化剂由合成气经费托合成路线一步法直接制备液化石油气。通过采用共沉淀法、改性溶胶-凝胶法和浸渍法相结合的方法将Cu纳米颗粒浸渍在介孔二氧化硅壳包覆的FeMg催化剂上,所制备的Cu/FeMg@SiO2纳米核壳催化剂的物理化学性质通过一系列的表征技术进行分析,如XRD、TEM、N2吸附-脱附、H2-TPR、XPS 和 CO2-TPD等。Cu/FeMg@SiO2纳米核壳催化剂在液化石油气合成反应中表现出较高的CO转化率(96.6%)和较低CO2选择性(21.9%),其中,液化石油气的选择性到达37.9%。反应结果表明,SiO2 壳层抑制了CH4的形成,有助于增加长链产物。同时,高的CO转化率归因于Cu/FeMg@SiO2上活性金属Cu元素在SiO2壳上的高分散,进一步促进了烯烃加氢和C5 + 烃类产物的裂解。本实验中所提出的催化剂制备方法将为金属和沸石基纳米级催化剂的合成提供新的策略。Abstract: Direct synthesis of liquefied petroleum gas from syngas via Fischer-Tropsch synthesis route was systematically investigated over a nano-level core@shell catalyst. We introduced an incorporation of FeMg catalyst into mesoporous silica shell, with a further modification of Cu particles on the silica surface. The modified Cu/FeMg@SiO2 nano core-shell catalysts were synthesized by the combination of co-precipitation, modified sol-gel and facile impregnation methods. The as-synthesized catalysts’ physicochemical property was characterized by XRD, TEM, N2 adsorption-desorption, H2-TPR, XPS and CO2-TPD techniques. The catalytic performance of Cu/FeMg@SiO2 catalyst shows a high CO conversion of 96.6%, rather low CO2 selectivity of 21.9% and considerable LPG selectivity of 37.9%. The catalytic results indicate that the SiO2 shell restrains the formation of CH4 and contributes to increasing long-chain products. Meanwhile, the enhanced CO conversion of Cu/FeMg@SiO2 was ascribed to the active metal Cu dispersed on SiO2 shell, which also promoted olefin hydrogenation and cracking of C5+ hydrocarbons products. The proposed catalyst preparation method will provide a new strategy for the synthesis of nano level catalyst with combinations of metal- and zeolite-based catalyst.
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Key words:
- liquefied petroleum gas /
- core/shell /
- Fischer-Tropsch synthesis /
- mesoporous SiO2 shell
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Table 1 Texture properties of samples
Sample SBET /(m2·g−1)a v /(cm3·g−1) FeMg 90 0.36 SiO2 131 0.21 FeMg@SiO2 92 0.33 Cu/FeMg@SiO2 88 0.30 a: Determined by Brunauer-Emmett-Teller (BET) method Table 2 Catalytic performance of samplesa
Catalyst CO conv. /% CO2 sel. /% Hydrocarbons selectivity /% CH4 C2−4 ${\rm{P}}_{3-4}^{\rm{b}} $ ${\rm{O}}_{2-4}^{\rm{c}} $ ${\rm{C} }_{5+}$ olefinsd FeMg 97.9 35.0 22.6 59.2 28.0 11.7 18.2 16.8 FeMg@SiO2 97.0 31.3 19.5 54.5 22.3 16.0 26.0 24.2 Cu/FeMg@SiO2 96.6 21.9 22.3 60.2 37.9 3.7 17.5 6.3 a: Reaction condition: temperature-300 °C, pressure-1 MPa, W/F=10 g·h·mol−1, TOS=6 h, H2/CO/Ar= 12.6∶6.3∶1.0, b: P stands for paraffins, c: O means olefins, d: olefins includes the selectivity of O2−4 -
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