Insights into the Bimetallic Effects of a RhCo Catalyst for Ethene Hydroformylation: Experimental and DFT Investigations
Ning Huang, Boyang Liu, Xiaocheng Lan, Tiefeng Wang
Abstract
Rh-based bimetallic catalysts are promising ligand-free heterogeneous catalysts for hydroformylation reactions. It is important to understand the mechanism of this bimetallic promotion for designing highly selective and active heterogenous catalysts. In this work, the RhCo bimetallic catalyst was investigated focusing on the promotion effect of Co for the gas-phase hydroformylation of ethene. Adding Co to Rh increased both the catalytic productivity and selectivity to oxygenates. In situ diffuse reflectance infrared Fourier transform spectroscopy and CO-temperature programmed desorption were used to characterize CO adsorption. The results showed that the addition of Co to Rh changed the CO adsorption modes and strength for the Rh-based catalyst. Modulated CO adsorption strength was important to enhance selectivity. Density functional theory calculations were carried out to reveal the reaction mechanism. A reaction pathway was proposed to clarify the reason for enhanced selectivity on a RhCo bimetallic catalyst and show that the ratio between CO migration and desorption played a great role in this reaction.