CO2 hydrogenation over cobalt-containing catalysts

Carbon dioxide hydrogenation over catalysts consisting of 0.56-45 wt % cobalt supported on carbon nanotubes (CNTs), carbon nanofibers, few-layer graphite fragments, or CNTs-Al2O3 composites has been investigated. All of the Co/support catalytic systems have been characterized by temperature-programmed reduction, transmission electron microscopy, and scanning electron microscopy. Under the conditions of our catalytic experiment (1 atm, 180-500A degrees C), the CO2 hydrogenation products are CH4 and/or CO and the activity of the catalysts depends on the size and phase state of the cobalt particles. The CNTs-supported materials containing less than 5 wt % Co are catalytically inactive because of the amorphism of the metal. They can be activated by cobalt crystallization by means of heat treatment. The size of the cobalt particles deposited on the carbon supports is about 4 nm. Methods of functionalizing the carbon nanomaterial surface for additional stabilization of metal nanoparticles are suggested.