One-pot hydrogenation of carbon dioxide to methyl formate in an automated continuous-flow set-up
- "One-pot" Hydrierung von Kohlenstoffdioxid zu Methylformiat in einer automatisierten kontinuierlichen Anlage
Kühnrich, Ivo Robert; Leitner, Walter (Thesis advisor); Liauw, Marcel (Thesis advisor)
Aachen : RWTH Aachen University (2022)
Dissertation / PhD Thesis
Dissertation, RWTH Aachen University, 2022
In this thesis, a catalyst system for the one-pot CO2 hydrogenation with methanol to methyl formate under continuous-flow conditions has been developed. The one-pot approach is advantageous with respect to the good extractability of the highly volatile product methyl formate. Non-volatile ionic liquids were utilized as reaction medium for a homogeneous, Ru-based catalyst, thus allowing the application as catalyst phase under continuous-flow conditions. Novel imidazolium carboxylates were synthesized and investigated regarding their applicability as reaction medium. The fine-tuning of the hydrogen bonding properties of the imidazolium carboxylates was found to be decisive for harmonizing the opposing requirements of hydrogenation and esterification step in the synthesis of methyl formate. An automated continuous-flow set-up was constructed that enabled the implementation of a self-optimizing system utilizing a machine learning algorithm. The reaction conditions were optimized reaching a maximum methanol conversion to methyl formate of 23 % and a weight-time-yield of 38.7 gMFgRu−1h−1. Sustained stability and activity of the ionic liquid and the catalyst could be demonstrated for almost six days of continuous operation. Furthermore, the application of Lewis-acidic co-catalysts was tested and suitable reaction conditions were found that preserve their stability in the catalyst phase.