Improvement of coke resistance of Ni/Al2O3 catalyst in CH4/CO2 reforming by ZrO2 addition

This work investigates the improvement of Ni/Al2O3 catalyst stability by ZrO2 addition for H2 gas production from CH4/CO2 reforming reactions. The initial effect of Ni addition was followed by the effect of increasing operating temperature to 500–700 °C as well as the effect of ZrO2 loading and the promoted catalyst preparation methods by using a feed gas mixture at a CH4:CO2 ratio of 1:1.25. The experimental results showed that a high reaction temperature of 700 °C was favored by an endothermic dry reforming reaction. In this reaction the deactivation of Ni/Al2O3 was mainly due to coke deposition. This deactivation was evidently inhibited by ZrO2, as it enhances dissociation of CO2 forming oxygen intermediates near the contact between ZrO2 and nickel where the deposited coke is gasified afterwards. The texture of the catalyst or BET surface area was affected by the catalyst preparation method. The change of the catalyst texture resulted from the formation of ZrO2–Al2O3 composite and the plugging of Al2O3 pore by ZrO2. The 15% Ni/10% ZrO2/Al2O3 co-impregnated catalyst showed a higher BET surface area and catalytic activity than the sequentially impregnated catalyst whereas coke inhibition capability of the promoted catalysts prepared by either method was comparable. Further study on long-term catalyst stability should be made.