Activity of Ni/A1 O catalyst for a methanation reaction.

Abstract

The reduction of a commercial Ni/A1?O? catalyst was carried out at temperature ranged from 250 to 500??C and for duration from 2 to 16 hours. The effects of reduction conditions on the activity and selectivity of Ni/A1?O? were studied for a methanation reaction in a gradientless Berty reactor. These effects were used to determine optimal reduction conditions of the catalyst. The optimal reduction conditions are: temperature 300?C, duration 8 hrs. space velocity 3000 hr?¹, and heating rate of bed 5?C/min. The reaction rates wre measured by injecting a feed containing H? (26 mo1%), CO (6.7%), and the balance being nitrogen. The product stream contained H?, N?, CO, CH?, and small amounts of CO? gas. The operating temperature and pressure of the reaction were kept constant at 350?C, and 30 psig, respectively. The flow rate of the feed was kept constant at 600m1/min and 10 gm. Of catalyst was charged for each run. The catalyst used was commercial ni/A1?O? (C13-4-04) containing 20% Ni supported on A1?O?; manufactured by UCI (United Catalyst Inc.) and supplied by SAMAD Fertilizer Co. Al-Jubail, Saudi Arabia. The effects of speed of impeller on the rate of methanation were studied and it was found that mass transfer limitations disappeared at a speed of 786 rpm. The effects of space-time, H?/CO ratio and pressure on the activity and selectivity of the catalyst were studied. It is found that by increasing the space-time, the activity decreases while selectivity to CH?, formation increases from 90 to 96%. Use of higher H?/CO ratio (3.0-6.5) improves selectivity up to 98% but decreases the rate methanation. Lower H?/CO ratio (3.0-1.0) increases rate of CO conversion but decreases both the selectivity and the rate of CH? production. Reaction pressure apparently has an insignificant effect on the activity of catalyst. However, improvement in the selectivity is observed.²