GB636743A - Improvements in and relating to the dehydrogenation of secondary alcohols to ketones - Google Patents

Abstract

Aliphatic secondary alcohols are dehydrogenated to the corresponding ketones at elevated temperatures using a catalyst comprising copper and zinc oxide in proportions, expressed as a molecular ratio of cupric oxide to zinc oxide, in the range 2 : 1 to 1 : 2. The alcohols, anhydrous or mixed with water, for example in azeotropic proportions, may be vaporized by the passage of hydrogen and preheated before feeding to the reaction zone. The catalyst may be prepared by coprecipitation by alkali metal hydroxide or carbonate from water soluble salts of copper and zinc, e.g. nitrate or sulphate. After washing and drying it is ignited, pelleted and reduced by hydrogen at 300 DEG C. The presence of alkali in the catalyst in an amount expressed as sodium oxide, of not greater than 0.21 by weight, improves the yield and conversion and lengthens the life. The catalyst is washed to the required alkali content, dried, ignited, if desired, sieved and admixed with graphite, pelleted and reduced as above. The catalyst may be reactivated, after contamination by carbon, by treatment with air or air-nitrogen mixtures at 500 DEG C., followed by reduction with hydrogen at 300 DEG C. In examples, isopropanol is dehydrogenated to acetone, and secondary butanol to methyl ethyl ketone.ALSO:Aliphatic secondary alcohols are dehydrogenated to the corresponding ketones at elevated temperatures, e.g. 300-440 DEG C., and atmospheric, subatmospheric or superatmospheric pressure, using a catalyst comprising copper and zinc oxide in proportions, expressed as a molecular ratio of cupric oxide to zinc oxide, in the range 2 : 1 to 1 : 2. The alcohols, anhydrous or mixed with water, for example in azeotropic proportions, may be vaporized by the passage of hydrogen, and preheated before feeding to the reaction zone. The catalyst, which may comprise inert supports, e.g. kieselguhr or pumice, may be prepared by co-precipitation by alkali metal hydroxide or carbonate from water soluble salts of copper and zinc, e.g. nitrate or sulphate. After washing and drying it is ignited and reduced by hydrogen at 300 DEG C. The presence of alkali in the catalyst in an amount expressed as sodium oxide, of not greater than 0.2 per cent by weight, improves the yield and conversion. The catalyst is washed to the required alkali content, dried, ignited and may be sieved and admixed with a little graphite, pelleted and reduced as above. In examples, isopropanol is dehydrogenated to acetone, and secondary butanol to methyl ethyl ketone.