K-promoted cobalt-based catalysts for heterogeneous hydroformylation

Abstract

Developing inexpensive cobalt-based catalysts with sufficiently high activity and selectivity for heterogeneous hydroformylation has aroused great interest but remains challenging. Herein, a series of K-promoted Co/SiO₂ catalysts were synthesized and the promotional effect of K on the catalytic performance of Co/SiO₂ catalysts was investigated in the heterogeneous 1-octene hydroformylation reaction. It was found that the oxygenate selectivity was greatly improved from 49.6% for Co/SiO₂ to 79.2% for 0.4 K-Co/SiO₂ without sacrificing the activity at 4 MPa. Increasing the reaction pressure to 5 MPa can further increase the oxygenate selectivity to 92.9%. Various structure characterization techniques suggested that the metallic Co was the active site for hydroformylation. The K promoter was found to weaken hydrogenation ability and reduce the acidity of the catalyst, leading to a certain level of inhibition in the isomerization of 1-octene. Additionally, CO diffuse reflectance infrared Fourier-transform spectroscopy (CO-DRIFTS) provided further confirmation that the addition of K regulated the electronic structure of Co and enhanced the adsorption of CO. This work provides an effective strategy for designing highly selective non-noble Co-based heterogeneous catalysts for the hydroformylation reaction.