Carbon formation during volatile organic compound oxidation over a nickel catalyst

Effect of metal additives on carbon formation during volatile organic compo und oxidation over Ni/Al2O3 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 similar t o 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 catalyst (25% Ni by wei ght) does not improve the resistance to carbon formation. In contrast, a re markable improvement in the resistance to carbon formation is observed when Mg (10% by weight) is present. To understand the effect of Mg, nickel cata lysts have been synthesized over MgO and CaO supports. It is seen that the catalyst Ni/MgO is highly resistant to carbon formation. X-ray diffraction studies show that the NiO phase is highly stable over the MgO support but r educes to metallic nickel over the CaO support.