Activation of the Surface of Carbon and Nitrogen-Doped Carbon Nanotubes by Calcium Nitrate: Catalytic Properties of Cobalt Supported Catalysts of the Fischer–Tropsch Process Based on Them

Abstract

Using the methods of scanning and transmission electron microscopy (SEM and TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, the influence of concentration, time, and the procedure for the oxidative treatment of the surface of carbon nanotubes (CNTs) and nitrogen-doped carbon nanotubes (N-CNTs) in the mixture with calcium nitrate was studied. All prepared materials were tested as supports of cobalt-supported catalysts in the Fischer–Tropsch process. It is shown that an increase in the Ca(NO₃)₂ concentration from 15 to 25 wt % leads to the destruction of CNTs, and the time of treatment and oxygen concentration in the oxidizing mixture have almost no effect on the morphology and physicochemical characteristics of the materials. It is found that heterosubstitution in nanotubes and a change in the surface relief of the carbon support lead to an increase in CO conversion, and the catalyst activity increases in the series: Co/CNTs → Co/N-CNTs → Co/CNTs(Ca) → Co/N-CNTs(Ca).