GB1090287A - Production of dialkyl ketones - Google Patents

Abstract

Dialkyl ketones are prepared by heating saturated aliphatic carboxylic acids, in the gas phase at temperatures of 250 DEG to 500 DEG C. in the presence of a solid catalyst comprising a mixture of manganese dioxide and titanium dioxide. The carboxylic acids used preferably contain 2 to 18 carbon atoms, and are in particular, acetic acid, propionic acid, butyric acid, isobutyric acid and caproic acid. The catalyst mixture which can be used stationary or fluidized has a preferred particle size of from 100 microns to 600 microns. The ratio by weight of manganese dioxide to titanium dioxide is suitably from 1.0:1.5 to 1.0:5.0. The catalyst can take the form of pellets prepared from a paste of a mixture of the dioxides, dried and then heated for several hours at 400 DEG to 500 DEG C. in air or in the absence of oxygen, or it can be coemployed with either inert carrier substances such as diatomaceous earth or substances which themselves have catalytic activity for the reaction, such as the oxides of zinc, cadmium, thorium, uranium, aluminium, zirconium, magnesium, cerium, chromium, iron or divalent manganese. The metal oxides may also be replaced wholly or partly by other compounds of the metals which are converted to the dioxides on heating, such as the nitrates, hydroxides, carbonates or oxalates. A particularly suitable method is that in which catalysts to be used in a fluidized bed are prepared by impregnating titanium dioxide with an aqueous solution of manganese nitrate and further processing as described above. The catalyst may be regenerated, for example, by calcination in the air and subsequent treatment with concentrated nitric acid.ALSO:A catalyst used in the preparation of dialkyl ketones (see Div. C2) comprises a mixture of manganese dioxide and titanium dioxide. The catalyst mixture, which can be used stationary or fluidised, has a preferred particle size of from 100 microns to 600 microns. The ratio by weight of manganese dioxide to titanium dioxide is suitably from 1.0:1.5 to 1.0:5.0. The catalyst can take the form of pellets made from a paste of a mixture of the dioxides, dried and then heated for several hours at 400 DEG C to 500 DEG C in air or in the absence of oxygen, or it can be coemployed with either inert carrier substances such as diatomaceous earth or substances which themselves have catalytic activity for the reaction, such as the oxides of aluminium, zinc, cadmium, thorium, uranium, zirconium, magnesium, cerium, chromium, iron or divalent manganese. The metal oxides may also be replaced wholly or partly by other compounds of the metals which are converted to the dioxides on heating, such as the nitrates, hydroxides, carbonates or oxalates. A particularly suitable method is that in which catalysts to be used in a fluidised bed are prepared by impregnating titanium dioxide with an aqueous solution of manganese nitrate and further processing as above. The catalyst may be regenerated, for example, by calcination in the air and subsequent treatment with concentrated nitric acid.