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Abstract:
Central to this thesis is the exploration of novel polymer supports and catalysts, and their application in the conversion of biomass, a renewable source of fuels and chemicals.
The concept of the catalyst preparation is the direct nanocasting of powdered mesoporous polymer supports that are similar in morphology to conventional carbon or metal oxide solid supports and simultaneously share the chemical composition of commercial styrene-co-divinylbenzene ion-exchange polymers. Sulfonation and the deposition of metal nanoparticles develop the finished catalysts by postfunctionalization of the polymer supports. The so-formed polymer catalysts bridge the gap between commercial bead-shaped ion-exchange polymer catalysts and powdered inorganic catalysts, thereby allowing a direct comparison of the catalytic performance to both catalyst classes. Thus, structure-property relationships are derived and implemented to optimize the structure of sulfonic acid polymer catalysts. Furthermore, polymer-supported platinum catalysts are prepared, which show better catalytic performance in the oxidation of alcohols than the corresponding powdered inorganic catalysts.
The potential of polymer catalysts in a biorefinery is demonstrated conceptually with the conversion of important biomass-derived compounds, representing each of the three stages of a biorefining process. In the first stage, the macromolecular structure of biomass is broken down, exemplified in this work by the acid-catalyzed depolymerization of inulin to fructose (98% yield). The second stage corresponds to the conversion of a wide variety of crude biomass derived molecular compounds into few key platform compounds, demonstrated here by the acid-catalyzed dehydration of fructose to 5-hydroxymethylfurfural (HMF, 71% yield). Finally, the conversion of these platform chemicals into a wide range of marketable fuels and chemicals is exemplified in this work by the hydrogenation of HMF and the oxidation of glycerol and ethanol. The final products (maximum yields with different catalysts and reaction conditions) obtained using exclusively polymer-based catalysts, unless specified otherwise, are 2,5-dihydroxymethylfuran (80% from HMF), 2,5-dihydroxymethyltetrahydrofuran (70% from HMF, 25% from fructose), 2,5-dimethylfuran (27% from fructose with a carbon catalyst), glyceraldehyde (15% from glycerol), dihydroxyacetone (10% from glycerol), glyceric acid (60% from glycerol), acetaldehyde (30% from ethanol) and acetic acid (94% from ethanol).
