Continuous-flow hydrogenation over resin supported palladium catalyst for the synthesis of industrially relevant chemicals

Herein, the catalytic performance of palladium nanoparticles grafted on the polymeric TSNH₂ (Tentagel-S-NH₂) resin was investigated for continuous-flow liquid-phase hydrogenation of two industrially relevant chemicals: 2-methyl-3-butyn-2-ol and nitrocyclohexane. We investigated the effect of process parameters such as temperature and pressure on PdTSNH₂ activity and selectivity. Depending on the reaction conditions, well-dispersed PdNPs with average size of about 2 nm have shown very high flexibility in terms selectivity toward the desired products: 2-methyl-3-buten-2-ol or 2-methyl-2-butanol in the case of 2-methyl-3-butyn-2-ol hydrogenation and cyclohexanone oxime or cyclohexylamine as the main product in the case of nitrocyclohexane conversion. The optimal reaction conditions for 2-methyl-3-buten-2-ol formation were estimated at 25 °C and 5 bar, and in the case of cyclohexanone oxime formation at 40 °C and 10 bar. We demonstrated the general trend in the catalytic performance of 2.2 wt% Pd grafted on Tentagel-S-NH₂. Independently of the hydrogenated substrate, the increase in conversion leads to decreased selectivity to 2-methyl-3-buten-2-ol and cyclohexanone oxime at the expense of increasing the selectivity to 2-methyl-2-butanol or cyclohexylamine. Graphic abstract: [Figure not available: see fulltext.]