Promoting Strong Metal Support Interaction: Doping ZnO for Enhanced Activity of Cu/ZnO:M (M = Al, Ga, Mg) Catalysts
Promoting Strong Metal Support Interaction: Doping ZnO for Enhanced Activity of Cu/ZnO:M (M = Al, Ga, Mg) Catalysts
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DOI：
10.1021/acscatal.5b00188
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发表时间：
2015-06-01
期刊：
影响因子：
12.9
通讯作者：
Behrens, Malte
中科院分区：
文献类型：
--
作者：
Schumann, Julia;Eichelbaum, Maik;Behrens, Malte
研究了铝、镓、镁对铜/氧化锌甲醇合成催化剂载体的促进作用。合成了不同助剂和助剂的氧化锌载体，并在后续步骤中浸渍了金属铜。用各种方法对所有材料、载体、焙烧和活化的催化剂进行了表征，包括在不同气体气氛下的非接触式(微波)电导测量。发现少量的促进剂对氧化物载体的性质有很大的影响，包括织构和电子性质。我们发现在逆水煤气变换反应(RWGS)和甲醇合成中，氧化锌载体的电导率与催化剂的活性之间存在相关性。在rWGS中，三价促进剂Al3+和Ga3+促进了氧化锌载体的活化能和H-2反应级数的降低，表明这是电子促进作用。在甲醇合成中，结果表明Al3+和Ga3+对结构有促进作用。在这两个反应中都观察到了镁离子掺杂的不利影响。这种影响是在氧化锌在反应条件下的可还原性的背景下讨论的，该反应条件可以由促进剂以不同的方式进行调节。还原性被认为是铜/氧化锌体系动态金属载体相互作用的关键性质。
The promoting effect of Al, Ga, and Mg on the support in Cu/ZnO catalysts for methanol synthesis has been investigated. Different unpromoted and promoted ZnO supports were synthesized and impregnated with Cu metal in a subsequent step. All materials, supports, and calcined and activated catalysts were characterized by various methods, including contactless (microwave) conductivity measurements under different gas atmospheres. Small amounts of promoters were found to exhibit a significant influence on the properties of the oxide support, concerning textural as well as electronic properties. We found correlations between the conductivity of the ZnO support and the activity of the catalyst in the reverse water-gas shift reaction (rWGS) as well as in methanol synthesis. In rWGS the activation energy and reaction order in H-2 are decreased upon promotion of the ZnO support with the trivalent promoters Al3+ and Ga3+, indicating an electronic promotion. In methanol synthesis, results point to a structural promotion by Al3+ and Ga3+. A detrimental effect of Mg2+ doping was observed in both reactions. This effect is discussed in the context of the reducibility of ZnO under reaction conditions, which can be tuned by the promoter in different ways. The reducibility is seen as a critical property for the dynamic metal support interaction of the Cu/ZnO system.