PREPARATION OF KETENE FROM GLACIAL ACETIC ACID. METHYL ACETATE, AND ETHYL ACETATE

Laboratory studies were carried out to determine whether methyl and ethyl acetates could be pyrolyzed to give yields and conversions to ketene comparable to those obtainable from acetic acid. Acetic acid was pyrolyzed to ketene and water in the presence of 0.33% triethyl phosphate or phosphoric acid catalyst at 680°–760 °C. and 140–160 mm. Hg absolute. Maximum yield obtained was 80.6% and maximum conversion 34.5%. Methyl acetate was cracked to ketene and methanol at 610°–685 °C. and 95–400 mm. absolute, using triethyl phosphate, phosphoric acid, sulphuric acid, dimethyl sulphate, butyl borate, and silica gelboric acid as catalysts. High yields could be obtained only with phosphates in 2–3% concentration. Maximum yield to ketene, including ketene recovered as acetic acid, was 76% (conversion 31–34%). Maximum yield to methanol was 81.3% (conversion 33–34%). Methyl acetate containing 18% methanol was also cracked but results were poorer. Ethyl acetate, in the presence of 0.33% triethyl phosphate, was pyrolyzed to ketene, ethylene, and water at 630°–685 °C. and 140–190 mm. absolute. Maximum yield of ketene, including ketene recovered as acetic acid, was 85.8%. Maximum conversion to ketene was 35.4% and to ketene plus acetic acid 85.7%. Yields to ethylene were nearly quantitative.