Grenzflächendesign von funktionsintegrierenden Katalysatoren für die Ethanoldehydrierung
Zusammenfassung der Projektergebnisse
Acetaldehyde is a very important bulk chemical that is widely used as precursor for the synthesis of acetic acid, acetic anhydride, ethyl acetate and many more largely produced chemicals. Green chemistry alternatives to the petroleum-based process (Wacker process; is energetically costly, requires strong acidic solutions and produces chlorinated wastes) are oxidative or non-oxidative dehydrogenation of ethanol, which can be produced by biomass fermentation. Only few studies have reported on the non-oxidative dehydrogenation of ethanol to acetaldehyde. While Cu-based catalysts were successfully used, they suffer from reduced acetaldehyde selectivity due to the formation of side products, such as ethyl acetate, 1-butanol and 2-butanone, on acidic sites of the support, as well as short life time of the catalyst, caused mostly by the agglomeration of copper nanoparticles, if carbon supports are used, which lead to reduced levels of side products. Two approaches were followed to solve these problems, i.e. supporting the copper on designed silica/carbon supports or nano-confining zirconia materials with reduced concentration of acidic sites. For example, a thin layer of carbon over silica, selectively etched at locations of copper particles resulted in higher acetaldehyde selectivities, while having an interface of silica and copper to stabilize the particles and avoid sintering. Furthermore, hybrid carbon on hollow silica as support material also showed better performance compared to the copper on silica catalysts. On the other hand, zirconia supports, which were synthesized by the newly developed surface casting process using SBA-15-OH or KIT-6-OH revealed excellent performance with over 95% ethanol conversion and >99% selectivity towards acetaldehyde. Besides, the reaction temperature could be kept at 250°C, which is substantially lower than the reaction temperatures reported so far, moreover, catalysts were stable for over 20 hours on stream. An important aspect revealed during work on the project are shortcomings in the standard methods for determination of copper surface areas. While they are suitable for methanol synthesis catalysts, these protocols do not allow reliable analysis of other types of copper catalysts. Thus, alternative protocols are explored, which is almost finished and the results of which will be published in the near future.
Projektbezogene Publikationen (Auswahl)
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Copper Supported on Hybrid C@SiO2 Hollow Submicron Spheres as Active Ethanol Dehydrogenation Catalyst. ChemNanoMat, 2018, 4, 505–509
Wen-Duo Lu, Qing-Nan Wang, Lei He, Wen-Cui Li, Ferdi Schüth, An-Hui Lu
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Cu supported on thin carbon layer-coated porous SiO2 for efficient ethanol dehydrogenation. Catal. Sci. Technol., 2018,8, 472-479
Qing-Nan Wang, Lei Shi, Wei Li, Wen-Cui Li, Rui Si, Ferdi Schüth and An-Hui Lu
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Tailoring the Surface Structure of Silicon Carbide Support for Copper Catalyzed Ethanol Dehydrogenation. ChemCatChem 2019, 11, 481 – 487
Meng-Yue Li, Wen-Duo Lu, Lei He, Ferdi Schüth, An-Hui Lu
