Patent GB-281298-A (GB)
Title: Improvements in the manufacture and production of aromatic hydrocarbons
IPC: C10G47/00
Filed: 1927-11-23
Abstract: 281,298. I. G. Farbenindustrie Akt.- Ges. Nov. 24, 1926, [Convention date]. Cyclic hydrocarbons, such as benzene and its homologues, naphthalene, anthracene, and phenanthrene are obtained, by treating aliphatic or hydroaromatic hydrocarbons with an excess of hydrogen or gases containing hydrogen under pressure at temperatures above 500‹ C. in a circular course, preferably in presence of catalysts and removing the gaseous hydrocarbons (such as methane) from the circulating gas so as to prevent accumulation of such undesired products. The pressures employed may be 10-200 atmospheres or more. A large excess of hydrogen favours the production of benzene and a smaller excess, naphthalene. The temperature should not exceed 1000‹ C. Those parts of the apparatus in contact with the hot organic products must be free from materials favouring the production of coke soot or methane such as free iron or nickel, and are preferably made of special steel alloys such as those known as V2a, WT2 of Krupps, or chrome nickel, B fused in vacuo of Heraeus the composition of which are given, or cobalt alloys, or aluminium (so far as temperature permits) or an internal coating of aluminium may be used. When materials free from sulphur are treated, copper, silver or the like mav be employed. The catalysts employed should also be such as do not cause production of carbon or methane. Suitable catalysts are chromium oxide or chromium with or without another metal such as chromium alloys or together with zinc. aluminium or the like; also manganese oxide or chromate or active carbon alone or with additions such as chromium or other elements of the sixth group which are reduced at high temperatures. The methane or other gaseous hydrocarbons which are produced are absorbed from the circulating gas stream, for instance by dissolving in benzine under pressure, at a point subsequent to the removal of the cyclic hydrocarbons by condensation. The initial materials mav be of any origin for instance products of hydrogenation of carbonaceous materials, and may be of the nature of middle oils, and these if desired may be produced in the same reaction vessel in which they are treated for the production of cyclic hydrocarbons. The initial material mav be treated as vapour or finely divided liquid; in the latter case it may be converted into a froth by introducing hydrogen through porous plates or may be atomized below or at 400‹C and then treated with hydrogen and catalyst at 600‹C, the catalyst being heated if desired by highly heated hydrogen. When the products contain some non-aromatic compounds they may be cooled rapidly to below the temperature at which benzene and the like would be formed, i.e., 400‹ C. Hydrogen is usually liberated in the reaction. In the examples, a thick crude mineral oil of Elwerath near Hanover is converted into 70-80 per cent of benzene besides naphthalene and other low-boiling hydrocarbons, the mixture being free from impurities such as sulphur and suitable for motor fuel or solvents. A heavy middle oil from coal hydrogenation is atomized or vapourized at 400‹. C, rapidly heated to 600‹C in a narrow tube and then introduced into a contact chamber at 200 atmospheres pressure and 600‹C with 20 to 30 times its volume of hydrogen, the catalyst being an intimate mixture of chromium, molybdenum and manganese oxides in about molecular proportions; the products leaving the contact chamber are cooled under pressure, the condensate containing 85 per cent benzene and 5 per cent of benzene homologues and naphthalene, the rest being mostly hydroaromatic hydrocarbons, while the residual gas contains gaseous hydrocarbons especially methane equivalent to 20-30 per cent of the initial material which are washed out with benzene. A middle oil from mineral oil distillation is sprayed at 200 atmospheres into a vessel at 580‹C. heated externally and also internally by an electric heater, which serves as catalyst consisting of a spiral of chrome nickel B, the partial pressure of the oil vapour not exceeding 5-10, atmospheres; the condensate contains 60-70 per cent benzene, 10-15 per cent naphthalene and small quantites of anthracene; if the partial pressure of the oil vapour is increased two or three-fold, the condensate contains 30-40 per cent benzene, 40 per cent naphthalene, and 5 per cent anthracene. Paraffin wax is vaporized or atomized without decomposition and passed with nearly 25 times its volume of hydrogen through a tube containing chromium oxide (obtained from ammonium bichromate) at 600‹C. and 200 atmospheres, the products being rapidly cooled whereby a condensate is obtained containing 60 per cent of homologues of benzene. Specifications 272,556, [Class 32, Distilling &c.]; 283,600; and 302,253, [Class 32, Distilling &c.], are referred to.