A comparative study on the catalytic properties of high Ni-loading Ni/SiO2 and low Ni-loading Ni-Ce/SiO2 for CO methanation
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摘要: 采用等体积浸渍法制备了高镍负载量的13%Ni/SiO2(13Ni/Si)催化剂和低镍负载量的7%Ni-2%Ce/SiO2(7Ni-2Ce/Si)催化剂.通过N2物理吸附、XRD、FT-IR、TEM、H2-TPR/TPD等技术对催化剂进行表征,在连续流动微反装置上考察了催化剂的CO甲烷化活性.结果表明,在7Ni-2Ce/Si催化剂中NiO、CeO2和SiO2之间产生的相互作用,改变了Ni-O-Si键的化学环境,促进了氧化镍物种的分散和还原,进而提高了催化剂的活性比表面积,同时在催化剂表面形成了新的中等强度的CO吸附中心.与高镍负载量的13Ni/Si催化剂相比,低镍负载量的7Ni-2Ce/Si表现出更高的CO吸附能力和甲烷化活性.常压下,在CO体积分数1%和空速7 000 h-1的反应条件下,低镍负载量的7Ni-2Ce/Si催化剂上CO完全甲烷化最低温度为230 ℃,比高镍负载量的13Ni/Si低了30 ℃.
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关键词:
- CO甲烷化 /
- Ni-Ce/SiO2催化剂 /
- CeO2助剂 /
- 镍负载量
Abstract: Two Ni-based catalysts of 13%Ni/SiO2(13Ni/Si) and 7%Ni-2%Ce/SiO2(7Ni-2Ce/Si, by weight) were prepared by the incipient-wetness impregnation method and characterized with N2-sorption, XRD, H2-TPR, FT-IR, TEM, H2-TPD and CO-TPD techniques. It was shown that addition of Ce promoter generated an interaction among NiO, CeO2 and SiO2, which changed chemical environment of Ni-O-Si bond, enhanced the dispersion and reduction of NiO, and increased the active surface area. In particular, a new type of moderately strong CO adsorption sites was formed on the surface of the 7Ni-2Ce/Si catalyst. As a result, the low Ni-loading 7Ni-2Ce/Si catalyst exhibited higher CO adsorption capacity and CO methanation catalytic activity than the high Ni-loading 13Ni/Si. Under the reaction conditions of 1% CO (volume fraction in H2 atmosphere), GHSV of 7 000 h-1 and atmospheric pressure, the temperature for complete conversion of CO over the 7Ni-2Ce/Si catalyst was 230 ℃, being 30 ℃ lower than that found over the high Ni loading 13Ni/Si catalyst.-
Key words:
- CO methanation /
- Ni-Ce/SiO2 catalyst /
- cerium promoter /
- Ni loading
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