Liquid phase ammoxidation of p-tert-butyl toluene(PTT) to p-tert-butylbenzonitrile(PTBN) has been studied in presence of Co-Mn-Ni-O/SiO
2
which is first put forward as the catalyst of liquid phase ammoxidation.The catalyst is prepared by impregnation and the reaction is carried out in the absence of solvent.The structure and catalytic properties of catalysts have been characterized.The results showed that the catalyst exists in the form of spinel composite oxide(Co
Mn)(Co
Mn)
2
O
4
catalytic inactivation was mainly due to sintering.And parts of permanent decline of catalytic activity caused by the sinter cannot be by calcinations.The surface area and pore volume were obviously decreased by aromatic adsorption in liquid phase ammoxidation.