Cobalt ferrites (CoxFe3-xO4) nanoparticles with various compositions were synthesized by a new non-aqueous synthesis method. The cobalt ferrites were characterized by X-rays diffraction, and transmission electron microscopy coupled with energy dispersive spectroscopy. The nanoparticles are highly crystallized, with a homogeneous chemical composition. The particle size varies from 4 nm up to 7.5 nm, depending on the cobalt content. The smallest particles, with a size of 4 nm, are obtained for high cobalt content. These particles have also the highest micro-structural strain. Catalytic measurements were realized using Fourier Transform Infrared Spectroscopy. The lowest activation energy and the highest conversion rate are obtained for Co1.8Fe2.4O4, in the 400-500°C temperature range.