Synthesis and application of carbon materials in heterogeneous catalysis

David Benjamin Christensen*

*Corresponding author for this work

Research output: Book/ReportPh.D. thesis

Abstract

Catalysts play a key role in the chemical industry owing to their ability to increase the yield and purity of the product of a given process. Concerns of long turn sustainability and impact on the climate have seen an increased desire to move toward green chemistry. By developing new catalysts, processes may be performed under milder conditions, produce less waste or use abundant rather than scarce resources. This thesis covers several examples of projects aiming to improve upon the durability, sustainability or activity of carbon-based catalysts for important chemical reactions. This includes the formation of formic acid, which has potential as a liquid organic hydrogen carrier. Formic acid could be produced using low concentrations of an Ir precursor (0.00001 M IrCl3) on a porous organic polymer (bpy-PP-POP). The catalysts even showed some promise in catalyzing the reverse reaction, dehydrogenation to hydrogen and CO2, in a continuous setup to produce pure hydrogen. The dehydrogenation of formic acid was examined in more detail using a series of nitrogen doped ordered mesoporous catalysts. Nitrogen was shown to improve the reactivity and selectivity of the catalysts in the vapor phase system, but did not directly affect dispersion of the active metal or reaction mechanism according to analysis using ME-PSD-DRIFTS. Pt on nitrogen-doped ordered mesoporous carbon (Pt@NOMC) proved to be the best among the tested catalysts with a TOF of 870 h-1 at 120 °C with no production of CO. Finally, a method for synthesizing bimetallic MOF-derived carbon catalysts was tested in the hydrosilylation of ketones. CoCu containing catalysts were produced by carbonizing ZIF-67 impregnated with Cu-solutions to achieve bimetallic materials with tunable metal ratios. The carbonization introduced mesoporosity into the structure and at lower Cu-loadings; the overall dodecahedral structure of ZIF-67 could be retained. The Co9Cu1@NC catalyst was investigated in detail, showing an overall first order reaction and the formation of a radical intermediate. Reactivity of the Co9Cu1@NC was stable after having been recycled once, and it showed good activity for the hydrosilylation of cyclohexanone and acetophenone.
Original languageEnglish
Place of PublicationKgs. Lyngby
PublisherTechnical University of Denmark
Number of pages178
Publication statusPublished - 2020

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