A promoted gamma-Al2O3 catalyst impregnated with 7 wt% HCl and 7 wt% H3BO3 has been recommended for the manufacture of diphenylamine (DPA) from aniline in vapour phase process. The catalyst selection has been based on the comparison of activity and selectivity among gamma-Al2O3 catalysts treated with different chemicals. It has been observed that H3BO3 has the characteristics of arresting the rapid deactivation of gamma-Al2O3 catalyst and improving the DPA selectivity. A kinetic model based on dual site adsorption has been found suitable for kinetics of the catalytic system.