Inorganic salt catalysis in the process for the conversion of alcohols/alkylphenols into ethoxychloride surfactant intermediates

Abstract

The process for the preparation of alkyl/alkylphenylethoxychlorides, precursors to a range of speciality surfactants, was investigated. The original manufacturing procedure involved ethoxylation with ethylene oxide catalysed by potassium hydroxide of the alcohol/alkylphenol followed by uncatalysed chlorination with thionyl chloride. The chlorination stage was a batch process requiring long reaction times (4–18 h) at 80°C and resulted in cleavage of the ethyloxylate chain as 1,4-dioxan. Using a model alkylethoxyalcohol, we demonstrated that the chlorination stage may be effectively catalysed by alkali metal salts/bases. Rate enhancement and suppression of 1,4-dioxan production resulted. Investigation of a range of inorganic salts/bases for the catalysis of the chlorination of commercially realistic alkylphenylethoxyalcohols indicated lithium hydroxide monohydrate (0.2%) to be the most versatile and cost effective catalyst. Chlorination was complete after less than 0.25 h at 80°C and the benefits of a continuous process based upon this catalyst are discussed. Alkaline earth metal salts/bases were also found to be effective catalysts but transition and B-Group metal salts retarded chlorination and facilitated ethoxylate chain cleavage. The application of a single catalyst for the conversion of alcohols/alkylphenols into ethoxychlorides is proposed. We demonstrated that strontium hydroxide effectively catalysed both ethoxylation and chlorination of hexadecanol. The advantages of using lithium hydroxide monohydrate (strontium hydroxide) as a single catalyst for the manufacture of broad-(narrow-) distribution alkyl/alkylphenylethoxychlorides from alcohols/alkylphenols are discussed.