Pulse study on the partial oxidation of methane over Ni/ θ-Al 2O 3 catalyst

Abstract

Pulse reactions of CH 4, O 2 and mixed gas (CH 4/O 2=2) over fresh, partially reduced and well reduced Ni/ θ-Al 2O 3 catalysts have been carried out at 923 and 1023 K to study the mechanism of CH 4 activation and the catalytic partial oxidation of CH 4. The fresh catalyst showed high activity for the dissociation of CH 4, and CO rather than CO 2 was the main carbon-containing gaseous product while H 2 being detected for the first CH 4 pulse, suggesting that CH 4 can be partially oxidized to CO and H 2 by the lattice oxygen of NiO. The bond strength of Ni–O seems to be favorable to the partial oxidation of CH 4, which is due to the strong interaction between NiO and θ-Al 2O 3. The results of CH 4/O 2 pulses indicate that both metallic nickel and NiO x ( x<1.0) are active phases for partial oxidation of CH 4. It has been demonstrated that both the reaction temperature and the C/O ratio are critical to the selectivities to CO and CO 2. The mechanisms of the oxidation of CH 4 over fresh and reduced catalysts have been proposed.