Abstract
A number of metallic oxides and carbonates may be used as catalysts for the preparation of dialkyl ketones from higher fatty acids in the liquid phase. All cause violent frothing which can be controlled by adding the fatty acid gradually to the catalyst at the reaction temperature. The various metallic oxide and carbonate catalysts are compared and magnesium oxide is selected as most suited for the commercial preparation of ketones. The most suitable reaction temperature range is 330β360Β°. The crude ketone is greasy, but its properties arc greatly improved by pressing. During the reaction carbon dioxide is evolved in an amount equal to 94% of that required for complete ketonisation. Small amounts of carbon monoxide and other gases arc also formed. The progress of the reaction has been followed by measurement of the rate of liberation of carbon dioxide and the results arc shown to agree with the supposition that a ketoβacid arises as an intermediate in the formation of ketones. Interruption of the reaction and estimation of the unchanged acid present, together with a knowledge of the amount of carbon dioxide then liberated, allows the amount of ketoβacid present in the reaction mixture to be calculated. This is found to be constant during the early stages of the reaction, but increases greatly when the reaction becomes violent. It is suggested that formation of the salt of the ketoβacid is the rateβdetermining reaction and that this reaction is catalysed by the metallic oxide used.