Performance of Ni/MgO–AN catalyst in high pressure CO2 reforming of methane

The catalytic activity of 8.8 wt Ni/MgO–AN prepared from alcogel derived MgO was studied for the dry reforming of methane under high pressure (1.5 MPa). The catalyst showed a self-stabilization process during the reaction that lasted for 50 h, in which the catalytic activity decreased with increasing the reaction time on stream (TOS) up to 12 h, and then became stabilized thereafter. The activity decline during the initial 12 h of the reaction was found closely related to an increase in the amount of carbon deposits on the catalyst, which also became stabilized after the catalyst had served the reaction for 12 h. Comprehensive characterizations of the coked catalyst with Temprature programmed hydrogenation (TPH), X-ray photoelectron spectroscopy (XPS) and X-ray diffractometer (XRD) techniques revealed two kinds of carbon deposits (α-carbon and β-carbon) on the used catalyst. The α-carbon deposits were found to be produced from CH<inf>4</inf> decomposition while the β-carbon deposits from CO disproportionation. It was revealed that the accumulation of β-carbon deposits was a key cause for the activity decline and the self-stabilized catalysis during the initial 12 h of the high-pressure reaction. Moreover, it was also observed that an unavoidable sintering of metallic Ni particles from 6.5 to 11 nm, which happened within the very first hour of the reaction, was not directly related to the catalyst stability.