Synthesis of Zinc Dialkyldithiophosphate (ZDDP) and Identification of Impurities Formed

Abstract

Synthesis of zinc dialkyldithiophosphate (ZDDP) consists of two stages. In the first stage, phosphorus pentasulfide reacts with an alcohol to give dialkyldithiophosphoric acid. In the second stage, the acid is neutralized by zinc oxide. In addition  to the product, some impurities are also formed which affect the quality of the final product. If we can determine the chemical structure of these impurities then we may control the reaction conditions to reduce these by products.By separation techniques such as extraction , thin   layer    chromatography    and   column chromatography, limited amounts of these impurities are separated from the major product and are analyzed by FT-IR and 31PNMR spectroscopy. Then by changing reaction conditions such as rate of stirring, reaction pressure, neutralizing process, the order of addition of starting materials, and the types of P2S5 and ZnO in order to reduce the activity of formerly , we can raise purity of ZDDP up to 90%. Of the five methods for synthesis of ZDDP, the first method was used , because it yielded a higher purity product.
 

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Journal of Petroleum Research
Volume 16, Issue 53 - Serial Number 53
July and August 2006
Pages 68-78

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