Non-noble metal manganese oxide catalysts for the selective hydrogenation of α,β-unsaturated aldehydes and ketones

Selective hydrogenation of α,β-unsaturated aldehydes and ketones is of great importance in the production of fine chemical and pharmaceutical industry. Noble metals such as Au, Pt, Re, Ru and Ir are often used as active catalyst sites in chemo-selective hydrogenations. However, considering the expensive cost and limited abundance of noble metals, it is of high interest to develop non-noble metal catalysts for chemo-selective hydrogenations. We have previously shown octahedral manganese oxide with 2x2 tunnel structure (OMS-2) to be a good hydrogenation catalyst and display high selectivity towards hydrogenation of C=C (80% selectivity to hydrocinnamaldehyde at 96% conversion). In contrast to the previous results, herein, we have tuned the hydrogenation of cinnamaldehyde to achieve selective reduction of C=O group, with 95% selectivity to cinnamyl alcohol at 99% conversion using octahedral layered manganese oxide (OL) under basic conditions. Reaction conditions have been optimized, including, choice of catalysts, reaction temperature, solvent system and the addition of additive to the reactor (NaOH, KOH). We have further extended the scope of layered manganese oxides to the hydrogenation of other substrates including ketoisophrone and citral.