Catalytic performance of nickel-based catalysts with different supports in partial oxidation of methane to synthesis gas
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摘要: 采用浸渍法制备了单一载体(Al2O3、ZrO2、CeO2)和ZrO2、CeO2改性的Al2O3复合载体的Ni催化剂,考察了在甲烷部分氧化制备合成气反应中的催化性能。通过N2-物理吸附、H2程序升温还原、X射线衍射、NH3程序升温脱附和程序升温氧化等技术对催化剂进行了表征。结果表明,在单一载体催化剂中,Ni/Al2O3具有较大的比表面积,其初始反应活性较高,但该催化剂表面易形成大量的积炭而快速失活。Ni/ZrO2和Ni/CeO2催化剂比表面积较小,活性金属Ni在其表面分散性差,催化剂具有较低的CH4转化率。而CeO2和ZrO2改性的Al2O3复合载体催化剂,具有较大的比表面积,反应活性明显高于单一载体催化剂。CeO2-Al2O3复合载体催化剂具有最高的反应活性和较好的反应稳定性。同时表明,含CeO2催化剂反应后表面积炭较少,CeO2的储放氧功能增强了催化剂对O2的活化,提高催化剂活性的同时,可以抑制积炭的生成。Abstract: A series of Ni-based catalysts with different supports (Al2O3, ZrO2, CeO2, CeO2-Al2O3 and ZrO2-Al2O3) were prepared by the methods of impregnation. The effects of supports on the physical structures and catalytic performance of the resultant catalysts in partial oxidation of methane (POM) were investigated. The catalysts were characterized by N2 physical adsorption, X-ray diffraction, temperature programmed reduction by hydrogen, temperature programmed desorption of ammonia and temperature programmed oxidation. The results showed that the Ni/Al2O3 catalyst had a large BET specific surface area and high initial activity. However, the Ni/Al2O3 catalyst showed a serious deactivation due to the formation of large amount of carbon deposited on the surface of the catalyst. Ni/ZrO2 and Ni/CeO2 catalysts displayed low activity, which resulted from its low BET specific surface area and poor NiO dispersion. The Ni/ZrO2-Al2O3 catalyst showed high activity and the Ni/CeO2-Al2O3 catalyst exhibited the best activity and coking resistance among the catalysts. CeO2 could effectively suppress carbon formation and the transformation to inactive carbon species, due to the oxygen storage and release ability.
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Key words:
- methane /
- partial oxidation /
- nickel /
- support
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