Carbon formation during volatile organic compound oxidation over a nickel catalyst

Abstract

Effect of metal additives on carbon formation during volatile organic compound oxidation over Ni/Al₂O₃<i> </i>catalysts has been investigated. Cyclohexane is used as the model volatile organic compound. Reaction is carried out under oxygen limited conditions with just sufficient oxygen to convert ~10% of cyclohexane into carbon dioxide and water. Presence of Ca, Ba, Sr or Zn (10% by weight) in oxide form in the Ni/Al₂O₃<i> </i>catalyst (25% Ni by weight) does not improve the resistance to carbon formation. In contrast, a remarkable improvement in the resistance to carbon formation is observed when Mg (10% by weight) is

present. To understand the effect of Mg, nickel catalysts have been synthesized over MgO and CaO supports. It is seen that the catalyst Ni/MgO<i> </i>is highly resistant to carbon formation. X-ray diffraction studies show that the NiO phase is highly stable over the MgO support but reduces to metallic nickel over the CaO support.