Synthesis Of Liquid Antioxidant Alkyl-Diphenhydramine

Liquid alkyl-diphenhydramine with excellent properties is convenient to be applied in various fields. Liquid alkyl-diphenhydramine is a promising alternative to phenolic antioxidant which color could be darken by nitrogen oxide. However, the raw materials diphenylamine with active chemical properties prefers to lead product reddish brown after synthesis or during the period of storage. Consequently, the dark color of liquid alkyl-diphenhydramine product will contaminate the color of oil and polymers.The present work is a collaborative research program between the enterprise and the college. Two kinds of liquid antioxidant, octyl/butyl diphenylamine and nonyldiphenylamine, were selected to explore the optional process parameters. The alkyl-diphenhydramine shortcomings of dark color and undesirable product distributions were overcome in this study. Characterizations using infrared spectroscopy (IR), gas chromatography (GC), thermogravimetry (TG), and chroma analysis are carried out to investigate the relationships among molecular structure, product distributions, and physical properties of liquid alkylated diphenhydramine antioxidant. The results and corresponding conclusion obtained in this work are summarized as follows:(1) Octyl/butyl diphenylamine antioxidant was prepared by the alkylate reaction of diphenylamine and diisobutylene with activated clay catalyst. It shows that the DPA residual in the product plays an important role in the color of octyl/butyl diphenylamine. The amount of the DPA residual should be strictly controlled less than 2% during the synthesis. The product thermal stability is improved with the increasing of 2C8-DPA; however, the amount of solid deposition, which resulted in the deterioration of product physical performance, is increased. A desired octyl/butyl diphenylamine antioxidant was obtained when the optimize process parameter is following:reaction time is 4 h; the amount of catalyst is 30%.(2) Nonyldiphenylamine antioxidant was synthesized by the alkylate reaction of diphenylamine (DPA) and nonene, under the catalysis of activated clay. The synthesis parameters of alkylation reaction had critical influence on the 2C9-DPA selectivity. DPA conversion was 97.9% and 2C9-DPA selectivity was 64.1% under the optimize process parameter. The desired nonyldiphenylamine was obtained under the conditions that the mole ratios of nonene to diphenylamine was 8:1, the addition of catalyst was 30% (according to the mass of DPA), and the reaction time was 10h. In this study, the quality of nonyldiphenylamine is the same as that of the import Irganox L67 product.