On the secondary promotion effect of Al and Ga on Cu/ZnO methanol synthesis catalysts

IF 6.5 1区化学 Q2 CHEMISTRY, PHYSICAL

Journal of Catalysis Pub Date : 2024-10-04 DOI:10.1016/j.jcat.2024.115785

Benjamin Mockenhaupt , Jil Gieser , Sharif Najafishirtari , Lorena Baumgarten , Jelena Jelic , Thomas Lunkenbein , Erik-Jan Ras , Jan-Dierk Grunwaldt , Felix Studt , Malte Behrens

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Abstract

The structural and electronic effect of Al and Ga as ternary metals in Cu/ZnO catalysts for the methanol synthesis was examined. For this purpose, three zincian malachite-derived catalysts with the nominal Cu:Zn ratio of 70:30 were synthesized: an unpromoted binary catalyst (CZ) and two ternary catalysts with either 3 mol% Al (CZA) or Ga (CZG). Both Al and Ga showed a strong impact on the catalyst’s structure. Alongside the catalyst’s evolution from the co-precipitated precursors phase to the activated and reduced state, an improved microstructure and an increased BET surface area were found for the secondary promotor (Al or Ga) containing catalysts. Moreover, a sequence of chemisorption experiments allowed us to quantify and differentiate between Cu^surf and Zn^red surface species in the activated catalysts. Considering the specific copper surface areas, DRIFTS data and catalytic results, an additional electronic promotion of Al and Ga is proposed. As demonstrated by Ga K-edge XANES, this promotion effect is related to doping of the ZnO support and enhances the reducibility of ZnO to form more Zn^red sites. This effect is stronger for Al leading to a more pronounced Zn^red overlayer on the Cu surface due to SMSI. In methanol synthesis, this results in a performance order CZA > CZG > CZ.

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铝和镓对铜/氧化锌甲醇合成催化剂的二次促进作用

研究了铝和镓作为三元金属在用于甲醇合成的 Cu/ZnO 催化剂中的结构和电子效应。为此，研究人员合成了三种锌孔雀石衍生催化剂，Cu:Zn 的标称比例为 70:30：一种未促进的二元催化剂（CZ）和两种含有 3 mol% Al（CZA）或 Ga（CZG）的三元催化剂。铝和镓都对催化剂的结构产生了很大影响。在催化剂从共沉淀前驱体阶段向活化和还原状态演化的同时，还发现含有二级促进剂（铝或镓）的催化剂的微观结构得到了改善，BET 表面积增大。此外，通过一系列化学吸附实验，我们还对活化催化剂中的 Cusurf 和 Znred 表面物种进行了量化和区分。考虑到铜的比表面积、DRIFTS 数据和催化结果，我们提出了 Al 和 Ga 的额外电子促进作用。正如 Ga K-edge XANES 所证明的那样，这种促进效应与氧化锌载体的掺杂有关，它提高了氧化锌的还原性，从而形成更多的 Znred 位点。由于 SMSI 的作用，铝的这种效应更强，从而在铜表面形成更明显的 Znred 叠层。在甲醇合成中，这导致了性能顺序 CZA > CZG > CZ。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Journal of Catalysis 工程技术-工程：化工

CiteScore

12.30

自引率

5.50%

发文量

447

审稿时长

31 days

期刊介绍： The Journal of Catalysis publishes scholarly articles on both heterogeneous and homogeneous catalysis, covering a wide range of chemical transformations. These include various types of catalysis, such as those mediated by photons, plasmons, and electrons. The focus of the studies is to understand the relationship between catalytic function and the underlying chemical properties of surfaces and metal complexes. The articles in the journal offer innovative concepts and explore the synthesis and kinetics of inorganic solids and homogeneous complexes. Furthermore, they discuss spectroscopic techniques for characterizing catalysts, investigate the interaction of probes and reacting species with catalysts, and employ theoretical methods. The research presented in the journal should have direct relevance to the field of catalytic processes, addressing either fundamental aspects or applications of catalysis.