The role of catalyst support on the activity of nickel for reforming methane with CO 2

Abstract

Thermodynamic studies were conducted to determine the operating conditions needed to inhibit carbon deposition and nickel carbide formation as well as to study the possible solid-state reactions within the catalysts in reforming methane with CO 2. Five nickel commercial catalysts, manufactured for steam reforming, on supports containing alumina in different forms were studied and their catalytic activity, selectivity and stability were established using different feed ratios, space velocities and temperatures. Fused α-Al 2O 3 was the only stable catalyst support but such a system yielded relatively lower conversion. Although γ-alumina partly transformed to the α-form with a resultant exothermic effect and drastic decrease in surface area, a decrease in conversion was not detected. α-Al 2O 3 in the presence of mullite caused a rapid irreversible deactivation which is accompanied by an increase in volume of 21%. On the other hand the presence of α-Al 2O 3 in the presence of MgAl 2O 4 or calcium aluminate gave high conversions which increase with time due to the formation of phases more active than metallic nickel. In both cases the resultant solid-state reactions are endothermic and are accompanied by a decrease in surface area. In the presence of MgAl 2O 4 the residual alumina forms NiAl 2O 4 which is soluble in MgAl 2O 4.