From a Molecular Single‐Source Precursor to a Selective High‐Performance RhMnO x Catalyst for the Conversion of Syngas to Ethanol

• Published in: ChemCatChem 2019-01, Vol.11 (2), p.885-892
• Main Authors: Preikschas, Phil, Bauer, Julia, Huang, Xing, Yao, Shenglai, Naumann d'Alnoncourt, Raoul, Kraehnert, Ralph, Trunschke, Annette, Rosowski, Frank, Driess, Matthias
• Format: Article
• Language: English
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.201801978

The first molecular carbonyl RhMn cluster Na 2 [Rh 3 Mn 3 (CO) 18 ] 2 with highly labile CO ligands and predefined Rh‐Mn bonds could be realized and successfully used for the preparation of the silica (davisil)‐supported RhMnO x catalysts for the conversion of syngas (CO, H 2 ) to ethanol (StE); it has been synthesized through the salt metathesis reaction of RhCl 3 with Na[Mn(CO) 5 ] 1 and isolated in 49 % yields. The dianionic Rh 3 Mn 3 cluster core of 2 acts as a molecular single‐source precursor (SSP) for the low‐temperature preparation of selective high‐performance RhMnO x catalysts. Impregnation of 2 on silica (davisil) led to three different silica‐supported RhMnO x catalysts with dispersed Rh nanoparticles tightly surrounded by a MnO x matrix. By using this molecular SSP approach, Rh and MnO x are located in close proximity on the oxide support. Therefore, the number of tilted CO adsorption sites at the RhMnO x interface increased leading to a significant enhancement in selectivity and performance. Investigations on the spent catalysts after several hours time‐on‐stream revealed the influence of rhodium carbide RhC x formation on the long‐term stability.