Synthesis of the weakly coordinating anion [Al(OC10F15)4]− and continuous anhydrous synthesis of oxymethylene dimethyl ethers with gaseous molecular formaldehyde

Abstract: One goal of this thesis was the synthesis of the novel weakly coordinating anion [Al(OC10F15)4]− ([pfAd]−). The [pfAd]− anion exhibits a higher stability towards fluoride-ion abstraction compared to the frequently used [Al{OC(CF3)3}4]− according to performed quantum-chemical calculations. The synthetic access towards the [pfAd]− anion was achieved by reaction of LiAlH4 with C10F15OH in 1,2- diflurorobenezene, providing the versatile Li[Al(OC10F15)4]. However, Li[pfAd] was not obtained free of alcohol impurities. Albeit salt metathesis reactions enabled the synthesis of pure Ag[pfAd], [Ph3C][pfAd], and [H(OEt2)2][pfAd], that were characterized by NMR-, IR-, and Raman-spectroscopy, as well as single-crystal X-ray diffraction analysis. Synthesis of Tl[pfAd] in an aqueous reaction media, as well as [P9][pfAd] by reaction of [NO][pfAd] with P4 represent the stability and first applications of this novel WCA. This thesis further deals with novel synthesis pathways towards oxymethylene dimethyl ethers (OMEn; CH3(-OCH2)n-OCH3). For this purpose, the reaction of molecular formaldehyde (FA) with both dimethoxymethane (OME1) and dimethyl ether (DME) was investigated. A wide catalyst screening in a batch reactor was initially performed. The salts Mx+[NTf2]x with M = Cu+, Co2+ and Mg2+ and [NTf2]− = [N(SO2CF3)2]− were identified as very active catalysts in the reaction of FA with OME1. Supported ionic liquid phase (SILP) catalysts were prepared based on these metal salts and demonstrated the successful synthesis of OMEn in a continuous process. SILP catalysts with the ionic liquid (IL) EMIM[BF4] (EMIM = 1-Ethyl-3-methylimidazolium) showed a fast and strong deactivation. In contrast, those prepared with the IL EMIM[NTf2] showed an excellent catalytic performance and stable results in the continuous process, even if stored under ambient conditions for almost two months. The ideal reaction conditions in regard of OME1 conversion and OMEn>1 selectivity were identified by variations in the reaction temperature and the weight hourly space velocity (WHSV). The very active SILP catalysts were also utilized in the reaction of FA with DME. However, only traces of OME1 were observable during these reactions. Further SILP catalysts using less polar ILs, as well as different SiO2 carrier materials, were prepared. Analysis of the product-gas stream revealed only trace amounts of OME1. Thus, conclusions about the success of the reaction should be made with the utmost caution. Instead, the unprecedented reaction of FA with DME was successfully catalyzed by heterogeneous zeolites. Brønsted-acidic zeolites with a 3D pore structure, including H-BEA-25 and H-ZSM-5, proved to be catalytically active. The possibility of shifting the product selectivity in favor of OMEn and suppressing FA disproportionation to methyl formate was demonstrated by feed-gas FA:DME ratio variations

Angaben zum Objekt

• Standort: Deutsche Nationalbibliothek Frankfurt am Main
• Umfang: Online-Ressource
• Sprache: Englisch
• Anmerkungen: Universität Freiburg, Dissertation, 2023

Beteiligte, Orts- und Zeitangaben

• Ereignis: Veröffentlichung
• (wo): Freiburg
• (wer): Universität
• (wann): 2023
• Urheber: Billion, Andreas
• Beteiligte Personen und Organisationen: Krossing, Ingo ; Krossing, Ingo ; Kurz, Philipp ; Institut für Anorganische und Analytische Chemie. Freiburg im Breisgau ; Albert-Ludwigs-Universität Freiburg. Fakultät für Chemie und Pharmazie

Weitere Informationen

• DOI: 10.6094/UNIFR/240652
• URN: urn:nbn:de:bsz:25-freidok-2406521
• Rechteinformation: Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Letzte Aktualisierung: 25.03.2025, 13:49 MEZ