Kohlenstoffdioxid als C1-Baustein in der Synthese von Carbonsäuren und Kohlenwasserstoffen
- Carbon dioxide as a C1 building block in the synthesis of carboxylic acids and hydrocarbons
Schmitz, Marc; Leitner, Walter (Thesis advisor); Klankermayer, Jürgen (Thesis advisor)
Dissertation / PhD Thesis
Dissertation, RWTH Aachen University, 2018
Central theme of this work is the homogeneously catalyzed use of carbon dioxide (CO2) as a raw material or synthesis component, especially in combination with a sustainable reducing agent such as hydrogen (H2). In the first chapter of the thesis, the synthesis of lower and higher carboxylic acids with molecular rhodium compounds starting from non-activated alkenes and in the beginning also with oxygenated substrates is discussed. To understand the reaction, a systematic reaction development is to be pursued by using a close link between optimization and understanding of the various parameters. The aim is to obtain as complete picture as possible of the transformation, which is the prerequisite for a later rational catalyst design. On that way e.g., the choice of ligands with their different steric and electronic properties and the central atom play a crucial role. In this chapter, additional aspects (solvents, partial pressures, additives, promoters) of the developed catalyst system for the formal hydrocarboxylation are explored to provide in-depth information on the course of the reaction. Here, the actual formal hydrocarboxylation is understood as a sequence of a reverse water gas shift reaction (rWGSR) and a conventional hydroxycarbonylation in two interlocking processes and studied systematically. Subsequently, investigations are carried out on potential involved molecular rhodium compounds. In the second chapter of this thesis, based on the combination of CO2 and H2, a formal hydromethylation of cyclohexene with molecular ruthenium compounds, which has not previously been realized in this form, is treated. Core aspect here is also, as in the first chapter, a reverse water-gas shift reaction, but this time in combination with a hydroformylation and the consecutive, complete reduction to the corresponding hydrocarbon compound (methylcyclohexane). In order to simplify the realization of this reaction initially, synthesis gas is used successively instead of CO2 and H2 and systematically optimized for an understanding of the reaction process. Subsequently, first investigations on this transformation are carried out in their entirety based on CO2 and H2.