不同载体Ni基负载型催化剂对甲烷部分氧化制合成气催化行为研究

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。

Catalytic performance of nickel-based catalysts with different supports in partial oxidation of methane to synthesis gas

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.