GB1111416A - Dehydrogenation process - Google Patents

Abstract

Preparation of an aldehyde or ketone by the dehydrogenation of the corresponding primary or secondary alcohol respectively by contacting the alcohol at elevated temperature with a catalyst comprising elemental nickel and zinc oxide. Suitable feed alcohols include isopropanol, n- or sec-butanol, sec-pentanol or n- or sec-hexanol. The dehydrogenation catalyst, which may be supported on an inert material such as kieselguhr or pumice, preferably has a weight ratio of Ni to Zn in the range 1:100 to 10:1 and may be prepared by roasting a suitable support material, cooling it, then mixing the cooled support with an aqueous slurry formed from a nickel salt and zinc oxide, drying the mixture, roasting the residue in air or oxygen and, finally, heating (e.g. to 300 DEG to 400 DEG C.) in a stream of hydrogen. The dehydrogenation is preferably carried out at 250 DEG to 450 DEG C. by passing the feed alcohol in the vapour phase over the catalyst optionally in a stream of carrier gas such as hydrogen. The preparation of hexanones from sec-hexanols using a catalyst containing 2.3% Ni and 5.5% Zn is described. Comparative examples describe the use of catalysts containing copper and zinc oxide and copper and magnesium oxide.ALSO:A catalyst, suitable for dehydrogenating alcohols, comprising p elemental nickel and zinc oxide, preferably having a weight ratio of Ni to Zn in the range 1:100 to 10:1 and a combined weight of nickel and zinc oxide representing 0.1 to 98% by weight of the total catalyst, is prepared by roasting a suitable support material (e.g. pumice or kieselguhr), cooling the support material, mixing the cooled support material with a aqueous slurry formed from the nickel salt (e.g. nickel formate) and zinc oxide, drying the mixture, roasting the residue in a stream of air or oxygen and, finally, heating in a stream of hydrogen. The slurried catalyst composition is preferably dried at a temperature between 80 DEG and 150 DEG C., roasted in air at a temperature between 350 DEG and 450 DEG C. and reduced at a temperature between 300 DEG and 400 DEG C. The example described the preparation of a catalyst containing 2.3% nickel and 5.5% zinc by weight wherein 10-18 mesh pumice is roasted at 550 DEG C., cooled in vacuo, mixed with a slurry containing nickel formate zinc oxide and aqueous ammonia, dried and roasted in air and reduced with hydrogen prior to use. Catalysts containing 7.3% Cu and 12.6% Zn, and 7.5% Cu and 13.5% Mg are prepared by a similar method for comparison.