Reduced graphene oxide supported cobalt catalysts for ethylene hydroformylation: Modified cobalt-support interaction by rhodium

Abstract

The metal-support interaction (MSI) alters the geometric morphologies, electronic properties, or distribution of metal nanoparticles, which is indeed to influence the heterogenous catalytic system. Two heterogenous ethylene hydroformylation catalysts, cobalt supported on reduced graphene oxide (RGO) with or without Rhodium (5%Rh-20%Co/RGO and 20%Co/RGO), were successfully synthesized. The effect of the MSI between Co and RGO and a MSI tuning strategy by Rh on the ethylene hydroformylation (EH) were investigated. CoO nanorods was present in fresh Rh-Co/RGO, while only CoO nano-particles were formed in fresh Co/RGO. Rh enhanced the reducibility of the cobalt species. After reduction and the ethylene hydroformylation reaction, Co2C was formed in spent Rh-Co/RGO, while a mixture of Co and CoO were present in the spent Co/RGO. Co2C grew to a large flat plane structure in spent Rh-Co/RGO, while Co and CoO formed smaller nano-particles in spent Co/RGO. The changes of the geometric morphologies and the phases of the active species made by the Rh-Co-RGO interaction significantly enhance the activity of the CO and the selectivity for the production of the C3 oxygenates. A Model on how the nanoparticles distributed on the RGO were hypothesized.