Catalytic oxidation of n-octane over cobalt substituted ceria (Ce0.90Co0.10O2−δ) catalysts

Catalytic oxidative activation of octane was carried out in the presence of Co substituted ceria catalysts of the type Ce1−xCoxO2−δ (Ce0.90Co0.10O2−δ). The catalysts were synthesized by the solution combustion method and the surface characteristics were determined by BET, powder XRD, structural refinement and XPS. The synthesized catalyst crystallizes with a fluorite structure, the crystallinity was confirmed by bright-field images of TEM. Hydrogen uptake studies show a strong reduction peak at 425 °C and it proves substitution of cobalt ions inside the matrix of the lattice system. X-ray photoelectron spectroscopy (XPS) clarified that even though under reduction conditions, the cerium ions were slightly oxidized because of the sequence of standard reduction potentials of both cerium and cobalt ions. The catalytic activity of the catalyst was investigated between the temperature range from 350 to 550 °C, in a continuous flow fixed bed reactor at GHSV 4000 h−1 with varying n-octane to oxygen molar ratios from 1:0.5 to 1:2.5. Results show that the conversion and selectivity of products (alkenes, oxygenates, aromatics, carbon oxides and cracked products) from the n-octane varies consequently with n-octane to oxygen molar ratio. The product selectivity at iso-conversion for C8 products, aromatics, oxygenates and octenes was determined. The catalyst shows higher activity with respect to an increase in the n-octane to oxygen molar ratio and reaction temperature.

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► Ce0.90Co0.10O2−δ catalyst is prepared by a single step solution combustion method.
► Ce0.90Co0.10O2−δ is a good catalyst for the oxidation of n-octane.
► Catalyst shows good activity and selectivity to oxygenates, octenes and aromatics.
► C8 aromatics like ethyl benzene and styrene formed through C1 to C6 cyclisation.
► No deactivation of the catalyst seen even after long start-up/shut-down operations.