Bychko I. Size effect of iron nanoparticles supported on carbon nanotubes on their catalytic properties in the hydrogenation processes

The thesis is devoted to the size effect of monodisperse iron nanoparticles for activity and selectivity of catalysts with deposited iron nanoparticles on carbon nanotubes (CNT) in the processes of ethylene and crotonaldehyde hydrogenation. The series of nanocomposite catalysts with supported on CNT monodisperse iron-containing nanoparticles in the size range of 4-9 nm (Fe/CNT) was synthesized for the first time. It was shown that the supported nanoparticles could be reduced by hydrogen at 350 °C. Iron nanoparticles agglomeration and catalytic gasification of CNT to methane are observed at the temperature of 450 °C and higher. It was studied the ethylene hydrogenation process on Fe/CNT catalysts. It was found that the mechanism of the ethylene hydrogenation on Fe/CNT depends on temperatures. At temperatures to 200 °C there is only ethane as product of the ethylene hydrogenation. At temperatures higher 200 °C the hydrogenolysis of ethylene to methane is also observed. Ethylene hydrogenolysis process on iron catalysts partially caused by the hydrogenation of the iron carbide surface phase, which is formed by the interaction between supported metallic iron and ethylene. Deposition of Fe nanoparticles on CNT significantly affects the selectivity catalyst in hydrogenation of unsaturated aldehydes. Firstly, based on kinetic studies of ethylene and crotonaldehyde hydrogenation on Fe/CNT showed, that spillover of atomic hydrogen from the surface of the iron nanoparticles to the surface of carbon nanotubes plays significant role in the hydrogenation reactions. Spillover effect causes appearance of minimum in the dependence of Fe/CNT selectivity on the nanoparticles size. For the first time it was demonstrated a significant difference in the catalytic activity of bulk iron and Fe/CNT catalysts in the crotonaldehyde hydrogenation.