Catalytic Deoxygenation of Renewable Chemicals – Structure‐Performance Studies
Abstract
Generation of chemicals from a viable feedstock is an increasingly interesting field. One of the major issues is the high oxygen ratios in biomass. There are a multitude of ways to remove oxygen from organic molecules. This thesis deals with two topics: The dehydration of glucose into HMF and the decarbonylation of aldehydes both heterogeneous and in ionic liquids. Chapter 1 provides a walkthrough of areas such as green chemistry, ionic liquids, biomass, dehydration of glucose in ionic liquids and decarbonylation. The topics are all taking into account the current research and is subjectively chosen to provide a broad platform for the following chapters. Furthermore, the objectives for the thesis are listed here. Chapter 2 deals with the synthetic preparation of the catalysts and the catalytic setups. Chapter 3 deals with the dehydration of glucose into HMF in ionic liquids. The system was investigated thouroughly via several spectroscopic techniques. This was done in order to obtain novel information in regard to the catalytically active sites. EXAFS results showed that during the catalytic reaction, a species of the form CrCl4O2 was formed from CrCl6 in the solution. These are the predominant chromium containing species in the solution. EPR results showed the presence of a S= 1/2 spin system, and the only possible choice is radical formation. Optical absorption spectroscopy showed a change in the ligand field around the chromium. Chapter 3 also deals with the homogeneous decarbonylation of aldehydes. The investigation of the effects of the ionic liquids in the catalytically active species is investigated in depth and the system [Rh(dppp)2]Cl in BMImCl was shown to be the most active combination. The reusability of the system showed great potential. The system showed a potential to decarbonylate both aliphatic and aromatic aldehydes. Finally Chapter 3 looks at the heterogeneous decarbonylation of aldehydes, focussing on a continuous flow setup. The catalytic effect of oxidation state and ligandsphere is investigated. And the effects of temperature, solvent and substrate were under scrutiny. The catalyst decomposition was pictured by the aid of TEM and the formation of nanoparticles explained. Chapter 4 concerns the summation of the results as well as the future perspectives for the respective applications and scientific developments.
Info
Thesis PhD, 2014
UN SDG Classification
DK Main Research Area
Science/Technology
