Catalytic Upgrading of Acetaldehyde to Acetoin using a Supported N-Heterocyclic Carbene Catalyst.

We report the catalytic synthesis of 3-hydroxy-2-butanon (acetoin) from acetaldehyde as a key step in the synthesis of C4-molecules from ethanol. Facile C-C-bond formation at the α-carbon of the C2 building block is achieved using an N-heterocyclic carbene (NHC) catalyst. The immobilization of the catalyst on a Merrifield's peptide resin and its spectroscopic characterisation using solid-state Nuclear Magnetic Resonance (NMR) is described herein. The immobilization of the NHC catalyst allows for process intensification steps and the reported catalytic system was subjected to batch recycling as well as continuous flow experiments. The robustness of the catalytic system was shown over a maximum of 10 h time-on-stream. Overall, high selectivity S > 90% was observed. The observed deactivation of the catalyst with increasing time-on-stream is explained by ex-situ1H solution-state, as well as 13C and 15N solid-state NMR spectra allowing us to develop a deeper understanding of the underlying decomposition mechanism of the catalyst.

Mg(OH)2 -Facilitated Liquid-Phase Conversion of Lactic Acid into 1,2-Propanediol over Cu: An Experimental and Theoretical Study.

Mg(OH)2 is found to exhibit superior performance in the liquid-phase conversion of lactic acid (LA) into 1,2-propanediol over Cu. A conversion of 90 % with a selectivity of 98 % is achieved at 513 K and 5 MPa H2 . Mg(LA)2 could be identified as a crucial intermediate in this reaction, as it undergoes faster conversion than the combination of LA and Mg(OH2 ) and regeneration of Mg(OH)2 through the conversion of Mg(LA)2 as a substrate. DFT calculations reveal that the energetic span of the reaction decreases from 46.6 kcal mol-1 catalyzed with no cation to 43.6 kcal mol-1 with [Mg(OH)]+ , confirming the facilitating effect of Mg(OH)2 .