Patent GB-580088-A (GB)
Title: Improvements in or relating to the production of styrene and its homologues by dehydrogenation
IPC: C07C17/00
Filed: 1943-02-15
Abstract: Styrene, halogen-substituted styrenes, and homologues thereof are produced by passing the vapour of an alkyl-substituted benzene hydrocarbon, the alkyl group containing at least two carbon atoms, or a halogen substitution product thereof, with steam over a catalyst consisting of magnesium oxide impregnated with a vanadium oxide or a compound giving the same under the reaction conditions, and an alkali metal compound, said catalyst being substantially free from metals whose oxides are readily reducible by hydrogen to the metals, and from compounds thereof.  Preferably the vanadium oxide and the alkali compound are each present in an amount of 2-20 per cent. by weight of the magnesium oxide.  China clay may be incorporated.  For example, a mixture of china clay and magnesite is treated with a solution containing vanadium pentoxide and excess sodium hydroxide, the paste is shaped, dried, and broken into pieces.  Any soluble vanadium compound decomposing to oxides can be used for the impregnation; the catalyst preferably containing not less than 2-3 per cent. by weight of vanadium oxide.  Vanadium pentoxide or sodium metavanadate dissolved in aqueous sodium or potassium hydroxide, monoethanolamine or hydrogen peroxide is suitable.  Alkali metal compounds used include sodium or potassium hydroxide, sodium carbonate, acetate or nitrate.  With a catalyst containing china clay, steam may be used equivalent to about 0.5 mol per mol of hydrocarbon but 3-8 mols or more can be employed.  Ethylbenzene may be dehydrogenated to styrene at 550-700 DEG C., and isopropylbenzene to a -methylstyrene at 500-650 DEG C. a -Chlorethylbenzene gives a -chlorstyrene.  In examples: (1) calcined magnesite granules are impregnated with 5 per cent. of vanadium pentoxide and 3 per cent. of sodium hydroxide using a solution of the oxide in caustic soda.  Ethylbenzene with four molar proportions of steam is passed thereover at about 600 DEG C. with a contact time of two seconds, (2) a similar catalyst with 3-3.5 per cent. vanadium pentoxide is used at 550 DEG C. for conversion of isopropylbenzene to a -methylstyrene; (3) a similar catalyst at 570-600 DEG C. is used for dehydrogenating ethylbenzene to styrene with a molar ratio of steam to hydrocarbon of 4.1-8.2:1; (4) a mixture of 60 parts china clay and 80 parts calcined magnesite by weight is made into a paste with a solution containing 20 parts sodium hydroxide and 17 parts sodium metavanadate, extruded into lengths, dried, and broken. Ethylbenzene with 3.4 molar proportions of steam is converted to styrene at 590-600 DEG C. with a contact time of three seconds. U.S.A. Specification 1,986,241 is referred to.ALSO:Styrene, halogen-substituted styrenes and homologues thereof are produced by passing the vapour of an alkyl-substituted benzene hydrocarbon, the alkyl group containing at least two carbon atoms, or a halogen substitution product thereof, with steam over a catalyst consisting of magnesium oxide impregnated with a vanadium oxide or a compound giving the same under the reaction conditions, and an alkali metal compound, said catalyst being substantially free from metals whose oxides are readily reducible by hydrogen to the metals, and from compounds thereof. Preferably, the vanadium oxide and the alkali compound are each present in an amount of 2-20 per cent by weight of the magnesium oxide.  China clay may be incorporated.  For example, a mixture of china clay and magnesite is treated with a solution containing vanadium pentoxide and excess sodium hydroxide, the paste is shaped, dried and broken into pieces.  Any soluble vanadium compound decomposing to oxides can be used for the impregnation, the catalyst preferably containing not less than 2-3 per cent by weight of vanadium oxide.  Vanadium pentoxide or sodium metavanadate dissolved in aqueous sodium or potassium hydroxide, monoethanolamine or hydrogen peroxide is suitable.  Alkali metal compounds used include sodium or potassium hydroxide, sodium carbonate, acetate or nitrate.  With a catalyst containing china clay, steam may be used equivalent to about 0.5 mol. per mol. of hydrocarbon, but 3-8 mols. or more can be employed.  Ethylbenzene may be dehydrogenated to styrene at 550-700 DEG  C. and isopropylbenzene to a -methylstyrene at 500-650 DEG  C. a -Chlorethylbenzene gives a -chlorstyrene.  In examples: (1) calcined magnesite granules are impregnated with 5 per cent of vanadium pentoxide and 3 per cent of sodium hydroxide using a solution of the oxide in caustic soda.  Ethylbenzene with four molar proportions of steam is passed thereover at about 600 DEG  C. with a contact time of 2 secs.; (2) a similar catalyst with 3-3.5 per cent vanadium pentoxide is used at 550 DEG  C. for conversion of isopropyl-benzene to a -methylstyrene; (3) a similar catalyst at 570-600 DEG  C. is used for dehydrogenating ethylbenzene to styrene with a molar ratio of steam to hydrocarbon of 4.1-8.2 : 1; (4) a mixture of 60 parts china clay and 80 parts calcined magnesite by weight is made into a paste with a solution containing 20 parts sodium hydroxide and 17 parts sodium metavanadate, extruded into lengths, dried and broken.  Ethylbenzene with 3.4 molar proportions of steam is converted to styrene at 590-600 DEG  C. with a contact time of 3 secs. U.S.A. Specification 1,986,241 is referred to.