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  Surface casted metal oxides as catalysts for the conversion of renewable resources and Synthesis of dumbbell shaped fullerene assemblies

Pichler, C. (2018). Surface casted metal oxides as catalysts for the conversion of renewable resources and Synthesis of dumbbell shaped fullerene assemblies. PhD Thesis, Technische Universität Graz, Graz, Österreich.

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 Creators:
Pichler, Christian1, Author              
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1Research Department Schüth, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445589              

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 Abstract: In the present work a novel hard templating method was investigated that allowed the synthesis of metal oxides with unprecedented BET surface areas. The key for the successful synthesis of these materials is an increased interaction between the metal precursor and the silica template. This interaction is caused by a high concentration of silanol groups on the surface of the silica template and leads to surface casting of the pore walls of the silica with the metal oxide. A modified synthesis procedure resulted in mesoporous silica templates with high concentrations of silanol groups. The surface casting synthesis principle can be extended to several types of silica materials. The crucial requirement is the presence of a sufficiently high concentration of silanol groups. The types of suitable silica templates as well as producible metal oxides were examined. One of the fabricated metal oxides was ZrO2, and these materials exhibited a particular high surface area of up to nearly 400 m2·g-1. As ZrO2 is a widely used material for catalyst supports, the surface casted materials should also be tested as catalyst support. The first investigated reaction was the oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA), as FDCA possesses a high potential to be used as biobased monomer for polymer production. For this task the surface casted ZrO2 was loaded with Ru and tested for this reaction. To obtain benchmark catalysts also commercial and other types of Ru/ZrO2 materials were subjected to catalytic testing. The surface casted catalysts showed by far the best catalytic performance and allowed nearly quantitative conversion of HMF to FDCA. The high BET surface area of the surface casted materials leads to a better and finer distribution of the loaded Ru, resulting in smaller Ru nanoparticles, which exhibit higher catalytic activity. FDCA can be used as monomer for the production of the polymer polyethylenefuranoate (PEF). In the next step the synthesis of PEF was investigated and polymers with different molecular weight were synthesized. The obtained polymers were also tested for their susceptibility towards enzymatic hydrolysis. Another tested reaction system was the hydrodeoxygenation (HDO) of guaiacol. With this reaction another aspect of the utilization of renewable resources is investigated, which is the conversion of biomass to transportation fuels. Also for the HDO reaction the surface casted ZrO2 materials were used as catalyst supports, which were then loaded with Ni. It was shown that the preparation mode of the ZrO2 support had a significant influence on the catalytic results, as remaining elements like Si and Na from the preparation can change the material properties. The influence of Si and Na on these material properties - especially surface acidity and oxygen vacancy concentration - could be clarified. It could be rationalized how the change of these properties affected the results of the HDO reaction. Furthermore it was demonstrated that the oxygen vacancy concentration is an important factor for the catalytic performance, although so far this property has been hardly considered in the design of HDO catalysts. Doping with La was found to be an efficient strategy to tune the oxygen vacancy concentration, and by using this approach the catalytic performance of the catalyst could be improved remarkably. Independently from the previously mentioned topics, the controlled modification of fullerenes was investigated. The aim was to synthesize a dumbbell shaped molecule based on the connection of two single C60 fullerene molecules with a bridge moiety. Different attempts to prepare such a molecule were undertaken, and it was tried to control specific characteristics of the resulting dumbbell, such as to enable free rotation of the bridge moiety or the introduction, respectively omitting, of specific side chain groups.

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Language(s): eng - English
 Dates: 2018-03-212018-03-21
 Publication Status: Published in print
 Pages: 201
 Publishing info: Graz, Österreich : Technische Universität Graz
 Table of Contents: -
 Rev. Type: -
 Identifiers: -
 Degree: PhD

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