Preparation of unsaturated and saturated ketones

A process for the preparation of an unsaturated ketone of the formula (I) ##STR9## or a saturated ketone of the formula (II) ##STR10## where R.sup.1, R.sup.2 and R.sup.3 are each hydrogen, alkyl of 1 to 12 carbon atoms or a cycloalkyl, aryl, aralkyl or alkylaryl radical, or R.sup.1 and R.sup.3 or R.sup.2 and R.sup.3, together with the carbon atoms to which they are bonded, may form a cycloalkane, wherein a 5-methylene-1,3-dioxolanone which is substituted in the 4-position and is of the formula (III) ##STR11## where R.sup.1, R.sub.2 and R.sup.3 have the above meanings, (a) for the preparation of an unsaturated ketone (I), is converted in the gas phase at a temperature of from 100.degree. to 500.degree. C. in a fixed or fluidized catalyst bed, or in the liquid phase at a temperature of from 50.degree. to 200.degree. C. in the presence of a zeolite and/or of a B, Ce, Fe, Zr or Sr phosphate as catalysts and (b) for the preparation of a saturated ketone (II), is converted in the gas phase at a temperature of from 100.degree. to 500.degree. C. in a fixed or fluidized catalyst bed, or in the liquid phase at a temperature of from 50.degree. to 200.degree. C. in the presence of hydrogen over a zeolite and/or a B, Ce, Fe, Zr or Sr phosphate, which carries one or more hydrogenation components, as catalysts.