Hydrothermal carbon supports for biorefinery-related catalysis

Abstract: Central to this thesis is the exploration of novel hydrothermal-based catalysts and their application in Biorefinery-related chemical reactions, with a focus on hydrogenation and solid acid catalysed reactions. Catalytic transformations in the liquid phase are a critical component of the continuing elaboration of Biorefinery and Power-to-X concepts. In a materials context, new heterogeneous catalysts are required to address challenges of catalyst’s stability and resistance in polar, low pH environments and chelating media of Biorefinery-related platform molecule transformations. Traditional carbon-based catalysts are produced based on petrochemical resources and are typically microporous with limited tuneability, which would hinder their application in Biorefinery processes.
The concept of the catalyst support preparation is based on the hydrothermal carbonisation (HTC) of biomass-based precursors. The low-temperature synthesis (180 °C) provides highly functional carbonaceous materials with the possibility for heteroatom doping and material tuning. Following the HTC synthesis, the next step includes secondary thermal carbonisation at different temperatures in an inert atmosphere. The final step is the functionalisation of the optimised support with acidic sulfonic groups or the impregnation with palladium nanoparticles, depending on the catalyst application.
With regard to the catalyst application in solid acid catalysis (Chapter 3 and 4), an acidic hydrothermal catalyst was developed by the optimisation of HTC support morphology and surface functionality in order to obtain high loading of sulfonic groups and fast diffusion of the large organic molecules to the active sites. It was found that the incorporation of sulfur-functional groups only partly depends on the specific surface area and porosity of HTC carbons, but mainly on the presence of oxygenated surface chemistry. Structure-activity relationships in esterification reactions revealed a correlation between the high catalytic activity and high loading of sulfonic groups on the mesoporous HTC structure with high specific surface area. In addition, an optimised acidic hydrothermal catalyst was applied in a challenging Biorefinery-related conversion of glucose to ethyl levulinate. High catalytic activities were obtained in combination with green solvents, which partly prevented deposition of carbonaceous material so-called humin and avoided complete deactivation of the catalyst.
The thesis as next is focused on the development of a palladium (Pd) catalyst supported on nitrogen-doped carbogels (NDC) as described in Chapter 5. NDC material chemistry was tuned by secondary thermal carbonisation at increasing temperatures in inert atmosphere. After Pd impregnation, it was found that nitrogen bonding motif(s) influenced size, dispersion and electronic structure of the formed Pd nanoparticles. The catalytic properties of such catalyst systems were investigated in Biorefinery-related aqueous-phase phenol hydrogenation to cyclohexanone, revealing excellent stability, good activity and selectivity towards phenol hydrogenation. In particular, the optimised Pd/NDC catalyst resulted in higher stability under batch as well as under flow reaction conditions than a commercial catalyst with Pd supported on activated carbon

Angaben zum Objekt

• Standort: Deutsche Nationalbibliothek Frankfurt am Main
• Umfang: Online-Ressource
• Sprache: Englisch
• Anmerkungen: Universität Freiburg, Dissertation, 2020

Klassifikation und Themen

• Schlagwort: Carbon ; Catalysis ; Heterogene Katalyse ; Bioraffinerie ; Katalytische Hydrierung ; Säurekatalyse

Beteiligte, Orts- und Zeitangaben

• Ereignis: Veröffentlichung
• (wo): Freiburg
• (wer): Universität
• (wann): 2020
• Urheber: Bosilj, Monika
• Beteiligte Personen und Organisationen: Fischer, Anna ; Albert-Ludwigs-Universität Freiburg. Fakultät für Chemie und Pharmazie

Weitere Informationen

• DOI: 10.6094/UNIFR/174774
• URN: urn:nbn:de:bsz:25-freidok-1747743
• Rechteinformation: Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Letzte Aktualisierung: 15.08.2025, 07:33 MESZ