GB898790A - Process for oxidizing olefines to aldehydes, ketones and acids - Google Patents

Abstract

A catalyst for the oxidation of olefinic hydrocarbons in neutral to acid medium comprises a salt of palladium, iridium, ruthenium, rhodium or platinum and a redox system. Suitable redox systems are compounds of metals which under the reaction conditions may occur in various oxidation stages such as compounds of copper, mercury, cerium, thallium, tin, lead, titanium, vanadium, antimony, chromium, molybdenum, uranium, manganese, iron, cobalt, nickel or osmium; other inorganic systems such as sulphite/sulphate, arsenite/arsenate or iodide/iodine systems; or organic redox systems such as azobenzene/hydrazobenzene or quinones or hydroquinones of the benzene, anthracene or phenanthrene series. The process may be carried out in solution or using a solid catalyst which may be supported on silica gel, pumice, alumina or coal. Alternatively the catalyst may be used as a slime in water or an aqueous solvent, e.g. aqueous acetic acid, glycol, glycerol or dioxane. A slime catalyst may be regenerated by dissolving it in a mineral acid. Advantageously a salt, e.g. sodium or potassium chloride, is added to the catalyst and also, if desired, a dispersant and/or a protective colloid. The catalyst may be regenerated (a) by treating it with oxygen or an oxygen-containing gas; (b) when a copper-containing catalyst is used, by heating it with carbon monoxide, an olefine or hydrogen and treating the resulting precipitate with water and an acid, e.g. hydrochloric acid, followed optionally by treatment with oxygen; (c) when palladium is present, by treatment with nitrogen-oxygen compounds; or (d) by thermal treating with a mineral acid. Specification 884,962 is referred to.ALSO:Aldehydes, ketones and/or acids corresponding to the aldehydes are produced by contacting an olefinic hydrocarbon in a neutral to acid medium with molecular oxygen and/or an active oxidising agent, water and a salt of palladium, iridium, ruthenium, rhodium or platinum in the presence of redox system. The "active" oxidising agents may be ozone, peroxide compounds, oxygen compounds of nitrogen, free halogens, halogen-oxygen compounds and compounds of the high valency states of metals, e.g. manganese, cerium, chromium, selenium, lead, vanadium, silver, molybdenum, cobalt or osmium. As the redox systems there may be used, for example, compounds of copper, mercury, cerium, thallium, tin, lead, titanium, vanadium, antimony, chromium, molybdenum, uranium, manganese, iron, cobalt, nickel or osmium or other inorganic redox systems such as sulphite/sulphate, arsenite/arsenate, or or iodide/iodine systems or organic redox system such as azobenzene/hydrazobenzene, or quinones or hydroquinones of the benzene, anthracene, or phenanthrene series. The presence of copper salts is particularly advantageous. The oxygen may be used in the form of air. The olefinic hydrocarbons may be used as a gaseous mixture containing, e.g. saturated hydrocarbons in addition to the olefine. The process may be carried out in solution in an aqueous solvent or using a solid catalyst which may be supported, e.g. on silica gel, pumice, alumina or coal, or using a slime catalyst. Suitable aqueous solvents are aqueous solutions of acetic acid, glycol, glycerol, dioxane or mixtures thereof. It may be advantageous to add prior to or during the reaction a compound yielding anions under the reaction conditions, e.g. an inorganic acid, a salt, a halogen, a halogen-oxygen compound or an aliphatic halogen compound of low molecular weight. The process is preferably carried out at a temperature in the range 50 DEG C.-160 DEG C. If the process is carried out in the liquid phase it may be necessary to use superatmospheric pressure. The preferred pH values of the p reaction mixture lie between 0.8 and 3. A metal halide, e.g. copper chloride, or a halogenoacetic acid or a salt thereof may be advantageously added to improve the solubility of the redox system. When ethylene is the starting olefine some acetic acid is formed in addition to acetaldehyde and, if desired, the acetaldehyde may be oxidised by known methods to acetic acid. Olefinic hydrocarbons which may be used as starting materials are, for example, ethylene, propylene, butylene, pentene, cyclohexene and styrene. The olefinic compound and the oxygen may be contacted simultaneously or separately with the catalyst. The reaction product required may be separated from the reaction mixture and the remainder reintroduced into the reactor. The olefinic hydrocarbon and oxygen may be introduced as a mixture or separately into the reaction vessel at several points. Preferably the ratio of the weight of the redox metals to that of the platinum group is at least 15 : 1, preferably 25-500 : 1. The yield of acids corresponding to the aldehydes may be increased without reduction of the aldehyde yield if the catalyst contains in addition to the noble metal salt and a redox system, an oxide of iron, manganese and/or cobalt. When copper and halogen are present in the reaction mixture it is preferable to keep the molar ratio of copper to halogen between 1 : 1 and 1 : 2. The amount of halogen present in a neutral salt is not included in this ratio. Desirably a quinone which may be substituted by a sulphonic or carboxylic acid group is added to the reaction mixture. The reaction is favourably influenced by irradiation of the reactants with rays rich in energy, preferably ultraviolet light or X-rays. The reaction may be carried out in a reactor comprising several stages, each of which has a contact catalyst and a coling zone or, alternatively, in a shaft furnace. Various methods of regenerating the catalyst are given. To avoid corrosion in the apparatus it is desirable to use an apparatus which is lined with titanium, enamel, a titanium alloy, tantalum, resins, rubber or brick. Examples are given of the oxidation of ethylene to acetaldehyde and acetic acid, propylene to acetone and propionaldehyde, butene-1 to methylethyl ketone and n-butyraldehyde; butadiene to diacetyl; isobutylene to isobutyraldehyde and tertiary butanol; propylene mixed with propane to acetone and propionaldehyde; and a mixture of ethylene and propylene to acetaldehyde and acetone, using various catalysts. Specification 884,962 is referred to.