Patent GB-283600-A (GB)
Title: Improvements in the catalytic decomposition of cyclic compounds
IPC: C10G47/00
Filed: 1926-07-12
Abstract: 283,600. Johnson, J. Y., (I. G. Farbenindustrie Akt.-Ges.). July 12, 1926. Benzene and other hydrocarbons: aniline; alcohols.-Aromatic, hydroaromatic, and heterocyclic compounds are converted into compounds containing a smaller number of carbon atoms than the initial materials by treatment with hydrogen, or gas mixtures containing hydrogen, in the presence of mixed dehydrogenating catalysts, the treatment being applied at diminished, ordinary, or slightly elevated pressure and at a temperature above 300‹ C. but below dull red heat. The mixed dehydrogenating catalysts may be mixtures of a number of dehydrogenating catalysts or mixtures of a dehydrogenating cata- Lyst with one or more activating substances such as the mixtures of iron, cobalt, or nickel with activating substances described in Specification 2306/14, [Class 1 (i), Chemical processes &c.]. For example, for the conversion of cyclic compounds containing oxygen, such as higher phenols, into lower products free from oxygen, catalysts containing iron, cobalt, nickel, molybdenum, and/or vanadium, or compounds or mixtures of compounds thereof, are suitable, and for the production of benzene from its higher homologues or from polynuclear hydrocarbons or hydroaromatic or heterocyclic compounds, catalysts containing iron, cobalt, nickel, molybdenum, vanadium, tungsten, manganese, and/or chromium, or compounds or mixtures of compounds thereof, may be used. Suitable activating substances are those elements of the fourth to the seventh periodic group which form difficultly reducible oxides, such as titanium, vanadium, chromium and manganese, and also boron, the alkali and the alkaline-earth metals, including beryllium and magnesium, and the earth metals, especially aluminium and zinc; the oxides or other compounds of these elements also may be used. It is preferred to remove from the reagents, prior to the reaction, contact poisons such as sulphur, arsenic compounds, and metal carbonyls. The gaseous hydrocarbons into which the carbon atoms or groups split off by the decomposition are generally converted may be treated with steam at a high temperature to produce a mixture of hydrogen with carbon monoxide or dioxide, which mixture may be used in the catalytic manufacture of alcohols or for the production of hydrogen. In one example, a mixture of carbazol vapour with hydrogen is passed at 350‹ C. over a catalyst prepared by reducing in hydrogen at 400‹ C. a mixture of aluminium hydroxide and iron oxide; the products include benzene, ammonia, and aniline. Other catalysts for use in this reaction may be prepared similarly from mixtures of (1) zinc oxide copper oxide, chromic acid, and ferric oxide; (2) magnesium oxide and ferric oxide, (3) zinc oxide, ferric oxide, and aluminium oxide, or (4) zinc oxide, ferric oxide, and titanium dioxide. In another example, a mixture of cresol vapour with hydrogen is passed at 450‹ C. over a catalyst prepared by reducing in hydrogen at 350‹ C. a mixture of iron oxide and alumina; the products include benzene and toluene. Other phenols or mixtures containing them, such as tar fractions, may be treated similarly, preferably with the use of mixed catalysts containing a component having both dehydrogenating and dehydrating properties, such as ferric oxide, molybdenum oxide, or uranium oxide. In another example, a mixture of hydrogen with the vapour of a low-temperature tar is passed at 450‹ C. over a catalyst prepared by reducing in hydrogen at 350‹ C. a mixture of iron oxide, magnesia, and ammonium vanadate; the product is a light oil. In a further example, a mixture of hydrogen with the vapour of centrifuged crude naphthalene is passed at 450‹ C. over a catalyst prepared by reducing in hydrogen at 400‹ C. a mixture of iron oxide and ammonium molybdate; the product comprises benzene and other liquid hydrocarbons, but may be made, by varying the conditions, to consist chiefly of toluene, o-xylene, and other homologues of benzene. Other varieties of naphthalene, tar fractions containing naphthalene, and tetra and deka-hydronaphthalene may be treated similarly. In the concluding example, a mixture of hydrogen with the vapour of hot-pressed crude naphthalene which has been purified from contact poisons is passed at 400-450‹ C. over a catalyst prepared by reducing in hydrogen at 400‹ C. a mixture of iron oxide, alumina, and a small amount of alkali; the product consists chiefly of benzene. Specification 277,394 is referred to.