Patent GB-290840-A (GB)
Title: Improvements in the purification of aromatic hydrocarbons
IPC: C07C7/00
Filed: 1927-06-07
Abstract: 290,840. Fairweather, H. G. C., (Selden Co.). June 7, 1927. Tar oils, purifying.-Aromatic hydrocarbons, particularly hydrocarbons of the benzene series, are purified by treatment with a halogen or halogen-yielding substances under such conditions that the impurities are converted into readily separable or harmless substances; treatment with sulphuric acid, to an extent less than that ordinarily applied, may precede or follow the halogenation. The halogenating agent may be gaseous or liquid chlorine or chlorine-yielding substances such as aqua regia, phosgene, sulphuryl chloride, nitrosyl chloride, other relatively unstable chlorides, hypochlorites, or hydrochlorioacid and an oxidizing, agent; bromine or brominating agents, or mixtures of chlorinating and brominating agents, also may be used. The halogenation may be assisted by the addition of halogen-carriers, and in this connection reference is made to sulphur, sulphur halides, thionyl chloride, benzene sulphochloride and its homologues, sulphuric acid, iron, ferric chloride or bromide, aluminium and its halides, antimony halides, tin, gold, tellurium, zirconium, uranium, vanadium, bismuth, molybdenum, zinc, and charcoal. The process may be assisted also by the application of heat, pressure, light, or a silent electric discharge; for example, the purification of benzene containing a little toluene may be effected in the vapour phase under the influence of light. Alkaline substances may be added, before or after halogenation, to neutralize the acid by-product. The process results in the conversion of aliphatic, alicyclic and heterocyclic impurities into easily separable halogencontaining or polymerization products or into innocuous products such as carbon tetrachloride (produced from carbon disulphide). In one example, a crude benzol fraction boiling up to 105‹ C. is treated at ordinary temperature with chlorine in the presence of a small amount of sulphur with or without soda ash; the product is washed and the benzene distilled off. In other examples, a similar fraction is treated at ordinary temperature with a mixture of chlorine and sulphur dioxide, and with chlorine in the presence of iron filings and of iron sulphide. In another example, a crude benzol fraction boiling at 105- 120‹ C. is treated at ordinary temperature with a mixture of chlorine and air in the presence of a little calcium carbonate, whereafter the toluene is distilled off, and in a further example a similar fraction is treated at ordinary temperature with sodium chlorate and hydrochloric acid. In example 7, a solvent naphtha fraction is treated at ordinary temperature with chlorine in the presence of benzene sulphochloride, whereafter xylenes are distilled off. The residue may be used as raw material in the production of coumarone and indene resins. In example 8, a low-boiling benzol fraction containing a little toluene and other impurities is distilled through a column, at the base of which chlorine is introduced in regulated amount. The distillate is collected and washed. The process may be effected continuously by replenishing the benzol in the still and removing therefrom the chlorinated impurities from which chlortoluene may be recovered. Further examples describe modifications of example 8 in which (1) the vapours in the column are exposed to light rich in ultraviolet rays, (2) a mixture of chlorine and sulphur dioxide is passed into the column, and (3) the column contains fragments of iron. In example 12, a low-boiling benzol fraction is treated with liquid chlorine, the product is washed, and the benzene distilled off. In example 13, a benzol friction boiling up to 105‹ C. and free from phenols is treated with 1-2 per cent of sulphuric acid. After washing, the fraction is treated with chlorine at ordinary temperature in the presence of sulphur or ferric chloride, with or without soda ash or lime, the product is washed, and the benzene distilled off. In example 14, a crude benzol fraction boiling up to 105‹ C. is freed from phenols and bases in the usual way and is then treated with 0.2-0.5 per cent of sulphuric acid. After washing, the fraction is treated with chlorine at ordinary temperature, preferably in the presence of aluminium chloride and calcium carbonate, the product is washed, and the benzene distilled off. In example 15, a crude toluene fraction is treated similarly, copper chloride being used as a chlorine carrier, and in example 16 a similar treatment is applied to a crude solvent naphtha fraction boiling at 130-150‹ C., bromine or a bromide, or benzene sulphochloride, being used as a chlorine carrier. In example 17, crude solvent naphtha is preliminarily purified as described in example 14, and a stream of liquid chlorine is then sprayed in beneath the surface, whereafter the product is washed and the solvent naphtha distilled off. The coumarone and indene bodies in the residue may be polymerized by treatment with sulphuric acid, and the chlorinated hydrocarbons, which are suitable for use as solvents, may be recovered by distillation. In the final example, a treatment similar to that of example 14 is applied to a light oil fraction boiling at 160-180‹ C.