IR-Spectroscopic Study on the Interface of Cu-Based Methanol Synthesis Catalysts: Evidence for the Formation of a ZnO Overlayer

• Published in: Topics in catalysis Vol. 60; no. 19-20; pp. 1735 - 1743
• Main Authors: Schumann, Julia, Kröhnert, Jutta, Frei, Elias, Schlögl, Robert, Trunschke, Annette
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.12.2017; Springer Nature B.V; Springer
• Subjects: Aluminum; Carbon monoxide; Catalysis; Catalysts; Characterization and Evaluation of Materials; Chemical synthesis; Chemistry; Chemistry and Materials Science; CO adsorption; Copper; Defects; DRIFTS; Industrial Chemistry/Chemical Engineering; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Magnesium oxide; MATERIALS SCIENCE; Methanol; Methanol synthesis catalyst; Original Paper; Pharmacy; Physical Chemistry; Spectrum analysis; Zinc oxide; Zinc oxides; Cu; Methanol synthesis catalyst; CO adsorption; DRIFTS
• ISSN: 1022-5528; 1572-9028
• DOI: 10.1007/s11244-017-0850-9

Carbon monoxide was applied as probe molecule to compare the surface of a ZnO-containing (Cu/ZnO:Al) and a ZnO-free (Cu/MgO) methanol synthesis catalyst (copper content 70 atomic %) after reduction in hydrogen at 523 K by DRIFT spectroscopy. Nano-structured, mainly metallic copper was detected on the surface of the Cu/MgO catalyst. In contrast, the high energy of the main peak in the spectrum of CO adsorbed on reduced Cu/ZnO:Al (2125 cm −1 ) proves that metallic copper is largely absent on the surface of this catalyst. The band is assigned to Zn δ+ –CO. The presence of not completely reduced Cu δ+ –CO species cannot be excluded. The results are interpreted in terms of a partial coverage of the copper nano-particles in the Cu/ZnO:Al catalyst by a thin layer of metastable, defective zinc oxide. Minor contributions in the spectrum at 2090 and 2112 cm −1 due to nano-structured Cu 0 –CO and CO adsorbed on highly defective Cu 0 , respectively, indicate that the coverage of metallic copper is not complete.