Abstract: Nonyl diphenylamine as a high base number antioxidant was synthesized by alkylation of diphenylamine with C9 olefins in the presence of solid Lewis acid catalyst in the laboratory. The product was isolated and characterized by NMR, TLC, and chromatography to determine the structure of these products and the content of the different components. The antioxidant performance in base oil was evaluated by means of RBOT and PDSC. It shows that the synthesized antioxidant contains tri-substituted (I) diphenylamine (II), disubstituted diphenylamine (III), monosubstituted diphenylamine (IV) and the unreacted diphenylamine. The total base number(TBN) order of these Component is Ⅳ>Ⅲ>Ⅱ>Ⅰ,the product prepared in lab has a higher TBN, better resistance to oxidation and less remaining diphenylamine compared to existing product.

Key words: alkylation, nonyl diphenylamine, total base number, antioxidant