GB342319A - Improvements in the treatment of hydrocarbons - Google Patents

Abstract

Unsaturated hydrocarbons; aromatic hydrocarbons.-Hydrocarbons containing more than one carbon atom are passed in two or more stages through a space heated to 1000 DEG -1200 DEG C. or over, at a space velocity of 50-100 reciprocal minutes or higher. The raw materials may be saturated hydrocarbons such as ethane, propane, and butane, unsaturated hydrocarbons such as ethylene and acetylene, or mixtures of the above compounds, e.g. natural gas, gases obtained by the destructive hydrogenation of coal, gases from oil cracking plants or mixtures also containing methane such as those obtained by thermal treatment of methane. The products may be unsaturated hydrocarbons such as ethylene, acetylene, or diolefines, e.g. butadiene, or aromatic hydrocarbons, e.g. benzene, or oils. The unsaturated hydrocarbons may be used as intermediate products, being further converted into light oils or other saturated hydrocarbons. Preferably the first treatment is performed under such conditions as to prepare the gas for the next thermal treatment. Between each treatment the light oils produced, which consist largely of benzene and homologues, are removed, and the unsaturated hydrocarbons may also be removed; alternatively, the gases remaining after the removal of benzene may be heated in known manner to yield hydrogen. It is better to perform the consecutive treatments in separate furnaces, so that the composition of the mixture, the temperature and the velocity may be more easily controlled. The conditions are chosen so as to avoid blocking of the chamber by carbon. At relatively low space velocity, aromatic hydrocarbons are the main products, while at high space velocity a large proportion of olefines is obtained. The space velocities may be as high as several thousand reciprocal minutes. Usually catalysts are unnecessary and the reaction chamber should not be packed with solid material other than the walls of the reaction vessel. The walls may exert a catalytic influence. The reaction vessel may be of carborundum or of graphite or heat-resisting alloys such as nickel-chromium or chromium steels. By using a reaction vessel whose walls are constructed of or lined with alumino-silicate refractories such as the mineral sillimanite or like material or similar composition, an increased yield of naphthalene is obtained, and in other cases hydrocarbons such as anthracene are formed. The chambers should be very narrow in relation to their length and width. The reaction vessel may be externally heated, but vessels with an inner tube for the heating gases or with an electrically heated member may also be used. Three examples, each describing a three-stage operation, are given. Among the intermediate products specified are butylene, propylene, ethylene, acetylene, with small amounts of butadiene and other diolefines not identified, while the final products are the aromatic light oils, methane and hydrogen together with some ethylene and acetylene. Specifications 264,827, 309,455, 309,488, 324,939, [all in Class 2 (iii), Dyes &c.], are referred to. In the first Provisional Specification, the use of inert gaseous diluents is mentioned. The space velocity most suitable for a maximum yield of ethylene with a methane-ethane mixture is stated to be double that necessary for maximum deposition of carbon and 1 1/2 times that necessary for maximum yield of benzene. Methane is included in the scope of the invention. A mixture is so treated that it is first stripped of its heaviest constituents, then of the next highest hydrocarbons, and so on. In the second Provisional Specification, an example of the treatment of pure propane is given, and it is stated that the ethylene so produced may be treated for the production of ethyl alcohol.