CH128729A - Process for purifying oils formed from aromatic hydrocarbons and containing impurities. - Google Patents

Description

Process for purifying oil formed from aromatic hydrocarbons and containing impurities. The present invention relates to a process for the purification of oils formed from aromatic hydrocarbons, and in particular hydrocarbons of the Benzol series, starting, for example, from the various fractions obtained by the distillation of tar from coal, petroleum tar or the like, as well as oils obtained by scrubbing coal gas which are extraordinarily rich in Benzol. All of these distillates and other products are of similar chemical composition and are in the form of aromatic hydrocarbons.

The usual method of purifying these oils to increase their commercial qualities is to distil, for example, the coal tar fractions, such as the so-called light oils, which are separated into light Benzols. and heavy Benzols by fractional distillation. Benzols, light or heavy, are treated to separate acid bases and oils and then washed with strong sulfuric acid. Sometimes the Ben zols are separated into fractions after removal of acids and bases and the individual fractions are washed with sulfuric acid.

Sulfuric acid washing is usually carried out in stages, the crude Benzols being first treated with partially exhausted acid, then with several successive portions of very fresh acid. In each Rage or Phase of this wash, the acidic sludge separates, when left to stand, and must be removed quickly as it tends to thicken due to the presence of resinizable substances. The amount of acid required usually ranges from 6 to 10% in the case of lighter fractions, while in the case of solvent Benzol fractions the amount may be considerably higher.

Residual acid is of limited utility, and acid resins separated from this acid are for the most part of little value, if not completely devoid of it.

The acid-washed Benzol fractions are washed with water or with a dilute alkaline solution and rectified, forming the commercial Benzols. These products still contain significant amounts of impurities and even technically pure Benzols, Toluols, etc., which have been subjected to the cleanest fractionation, still contain small amounts of aliphatic hydrocarbons, saturated and unsaturated, and various sulfur compounds, such as compounds of the nature of thiophene, carbon disulphide, etc. Other impurities are also present and vary with the source of the raw distillate.

For many purposes the presence of these impurities, some of which tend to polymerize into resins, is undesirable, especially when the Benzol, or toluol, or xylol, etc., which contains them is intended to be used in reactions which promote polymerization. Carbon disulphide, thiophene and other similar sulphide compounds are also detrimental in many cases, especially when Benzol, or toluol, or xylol, or their derivatives are to be employed for catalytic purposes, especially hydrogenation and reduction.

The invention makes it possible to partially or completely replace the expensive treatment of crude Benzols with sulfuric acid and alkaline washes in the case where phenols are present in small quantities and in certain cases to remove substantially, in a single operation, not only basic and unsaturated impurities, but also thiophene compounds, CS2, other organic and inorganic sulphide compounds, phenols, aliphatic hydrocarbons, etc. .

It also makes it possible, in many cases, to separate the impurities into a form in which they can be used to produce resins, solvents and other materials and also to avoid large losses of aromatic hydrocarbons. that occur in the old sulfuric acid washing process. According to the present invention, an oil is subjected, for example a crude coal tar distillate, or a similar mixture, with or without preliminary purification with strong sulfuric acid to a lesser extent than that employed. in industrial practice, to a selective halogenation of the impurities transforming some of the impurities into substances easily separated from the RTI ID="0002.0276" WI="23" HE="4" LX="1414" LY=" 584"> aromatic hydrocarbons present, and certain others into substances of a non-harmful nature.

The process according to the invention can be carried out by treating, for example, a crude light oil, or crude light oil fractions, before or after the removal of the acids and basic compounds contained therein, with chlorine, or substances yielding chlorine, with or without chlorine carrier, under suitable conditions. Aliphatic compounds, saturated and unsaturated, and thiophene compounds present in oils, as well as other impurities, such as CSZ and other sulphide compounds, organic and inorganic, are preferentially attacked by chlorine. and form, for the most part, high boiling point compounds of the aromatic hydrocarbons which can be easily separated by distillation in a very pure state. Bromine or brominating agents can also be used; but iodine does not act satisfactorily.

Aliphatic hydrocarbons, for example: pentane, hexane, amylene, hexylene, heptylene, octylene, alicyclic compounds such as cyclopentadiene, dicyclopentadiene, di- and tetrahydrobenzene, heterocyclic compounds, such as for example pyrrol, pyridine, thiophene, thiotolene, etc., are easily attacked by active halogen bodies to form addition or substitution products. halogens, or to form condensation or polymerization products which may or may not contain halogenated bodies. The aromatic hydrocarbons of the Benzol series are much more resistant to chlorine and bromine and, by adjusting the treatment, they can almost quantitatively remove some impurities and render others harmless without any significant loss of hydrocarbons. benzolics. 1 < even the Phenols and basic compounds which are present in the crude Benzol fractions in quantities too small to justify their extraction are much more reactive with chlorine and bromine than the corresponding hydrocarbons5 and are transformed into boiling substances pupil.

The CS' and other sulphide compounds contained in Brut Benzol are chemically transformed by the halogen body, in suitable working conditions, in particular in the presence of specific halogen body carriers such as iodide. .e. For example 1e CS,= is cha.nae in CC14, which is difficult to ä. separate by fractional distillation from the benzal mass which is chemically relatively inert and can exist in small quantities in the final products without rendering them unsuitable for many uses, such as the production of compounds intended for, ire used in catalytic reactions, such as the reduction of aromatic nitro-compounds to amines.

Elemental chlorine, gaseous or liquid, can be used in or in the form of solutions or one can make use of bodies yielding chlorine, such as aqua regia, phosgene, sulfuryl chloride, 1e nitrosyl chloride, los hypochlorites, los. chlorates, etc., or even hydrochloric acid can be used in the presence of an oxidant. Similarly, bromine or brominating agents can be used, as well as mixtures of chlorinating and brominating agents.

Liquid chlorine is particularly effective in the case where the quantity of impurities is great, because the evaporation of the liquid absorbs large quantities of heat and prevents the local increase in temperature due to the reaction of chlorine with the impurities, reactions which are for the most part exothermic. A local temperature rise is undesirable in many cases. in particular when one wishes to prevent the chlorination of side chains, because this chlorination is accelerated by a rise in temperature.

Mixtures of the above chlorinating agents, with or without elemental chlorine, can also be used in the presence or absence of chlorine carriers, and RTI mixtures can also be used. ID="0003.0275" WI=" 13" HE="4" LX="1572" LY="657"> chlorinating agents and brominating agents.

Sulfur or sulfide compounds such as halogen compounds of sulfur, sulfuryl chloride, thionyl chloride, benzol sulfochloride and homologs are preferably used, individually or together, as halogen carriers, because they preferentially catalyze the halogenation and in particular the chlorination of acyclic, alicylic and heterocylic compounds, of C.S' and of other sulfide compounds, both organic and inorganic, while having little effect on the halogenation of aromatic hydrocarbons. Nitrosyl chloride can also be used.

The following halogen carriers can also be used individually or together; iron, ferric chloride or bromide, aluminium, halogen derivatives of aluminium, halogen derivatives of antimony, tin, gold, tellurium, zirconium, uranium, vanadium, bismuth, molybdenum , zine, animal black, charcoal or any other well known halogen body carriers. The reaction can also be advantageously carried out in the presence of light, heat, or a silent electrical discharge. Combinations of the above-mentioned chemical mixtures and physical characteristics such as light, heat, etc., can be used. Chemical compounds of catalysts which preferentially catalyze the halogenation of aliphatic compounds and those which catalyze the halogenation of aromatic compounds can also be used in certain cases.

Halogenation, especially when dealing with fractions which contain a very high percentage of benzol, with only small amounts of toluol, can take place in the vapor phase. An advantage of processing in the vapor phase, especially in the presence of light, is that the toluol is also attacked and transformed into high boiling point compounds.

The halogenation can be carried out in batches or continuously in any suitable apparatus. Alkaline compounds of the alkali and alkaline earth metals may be added in small amounts to neutralize any HCl or other released acid and to protect the apparatus against corrosion. The addition can take place before or after the halogenation.

Although it is usually advantageous to completely eliminate the sulfuric acid wash, and an advantage of the invention is that in some cases such complete elimination is feasible, the invention is not there. s limited and sometimes it may be desirable to combine modified acid washing with selective halogenation of impurities. We have found that some of the impurities are more easily attacked by sulfuric acid than others and that it is possible, with a mild acid wash, to remove certain highly unsaturated impurities which are commercially safe. value, or of little value. The subsequent treatment with halogenated bodies then facilitates the extraction of the other impurities, or their reaction products with a halogenated body, except in a form uncontaminated by the impurities of lesser value removed by the preliminary, partial washing at 1 'sulfuric acid. 0n can thus obtain a product of Maction which has a greater commercial value than Jans 1e ras oiz mowing 1'épuration is done by halogenation. This is particularly true when processing fractions containing considerable amounts of resin-forming materials, such as coumarone and indene. The preliminary sulfuric acid wash also increases in many ca. the effectiveness of the halogenation treatment, and the remaining traces of acid appear in some cases to act as a catalyst for the halogenation.

It is usually desirable to employ a preliminary acid wash prior to RTI ID="0004.0276" WI="3" HE="4" LX="1330" LY="581"> , of course, is much less extensive than the ordinary sulfuric acid washing used in industrial processes. However, in some cases it may be desirable to treat first with a halogen body and then to acid wash, when the raw distillate contains impurities which are easily attacked by the halogen body and which form ment with him reactioii products. having commercial value.

By combining the sulfuric acid washing process with the halogenation process, it is possible to remove unwanted impurities in precisely the form in which they can best be used. Thus, certain impurities which are desired in a polymerized form can be removed by sulfuric acid, while other products which are desired in the form <B>of</B> halogenated bodies can be removed by 1st halogenation treatment. The combined process most satisfactorily removes all undesirable impurities, or converts them into harmless products. pentane, hexane, amylene, hexylene, heptylene, oatylene, alicyclic compounds such as cyclopentadiene, dicyclopentadiene, di- and tetrahydrobenzene, hydrindene, etc., heterocyclic compounds such as pyrrol, pyridine, thiophene, thiotelene, thioxene, etc. Other sulfide compounds, especially carbon disulfide, which may exist in crude fractions, are attacked by the body. halogen and are transformed into other compounds, such as carbon tetrachloride in carbon disulphide gas.

The following specific examples show how the invention may be practiced.

Example,) aple <I>1:</I> 0n fractionates an ordinary light oil (obtained for example by distillation of coal tar), and takes a fraction of Brut Benzol boiling up to 105°C; this fraction contains about 4% impurities consisting of a mixture of the compounds described above. Without any other treatment, the Crude Benzol is subjected to the action of approximately 6 to 8%, by weight, of gaseous chlorine at the temperature of the ball in which it operates. The chlorine is introduced in a rapid, uniform stream into the Benzol brat which is stirred vigorously. 0n preferably makes use of a chlorine distributor to ensure an even .distribution of chlorine. About 1 to 3% sulfur is added as a chlorine carrier. The solution takes on a dark color and the chlorine is quantitatively absorbed, with a slight release of HCl.

Once the reaction is finished, I mix it with water and dilute alkali, I dry it and I distill it with Benzol; After just one distillation, the column usually suffices. Or, if I wish, add ordinary commercial soda, finely divided, in quantities approximately equivalent to the chlorine absorbed.

The Benzols thus obtained are chemically very pure and suitable for the production of derivatives for use in catalytic reactions. Example <I>2:</I> 0n place in a container an eraction of Brut Benzol, boiling from<B>105'</B> to 120'C and containing about 85.10% impurities and an added a small amount of calcium carbonate. A mixture of chlorine and air is passed through it, by means of a chlorine distributor, until a sample which is distilled no longer colors the sulfuric acid when let it rest.

When the reaction is complete, stop chlorinating and allow a brief period of time to remove any remaining traces of HCl and chlorine. It is then stopped and the taluol fraction is distilled in a state of high purity. One beule distillation is usually sufficient. Example <I>3:</I> 0n treats a fraction of Benzol brat as Gele deci-ite in Example 1, passing about 8% chlorine, mixed with SO=, by means of a chlorine dispenser, stirring vigorously I mix during mowing the chlorination. Sulfur dioxide appears to accelerate the reaction, probably due to the formation of sulfuryl chloride which is an excellent chlorine carrier for aliphatic, alicyclic and heterocyclic compounds and also catalyzes the chlorination of sulphide compounds. . Chlorine is quickly and quantitatively absorbed. After all the chlorine has been absorbed, I neutralize I mix and I wash, then I distill the benzolic hydrocarbons, as described in Example 1.

Example <I>4:</I> 0n place in a container 1000 kilos of eraction Brut Benzol, boiling! from 105 to 120 C and containing about 8% impurities, and add about 100 kilos of a solution of sodium chlorate, then about 150 kilos of concentrated hydrochloric acid are slowly introduced, stirring vigorously. 0n neutralizes then I mix reaction and year I wash, then year distills the toluol reaction. Example <I>5:</I> 0n Rapidly chlorides a fraction of Crude Benzol, boiling up to 105 and containing 4 to 5% impurities, passing about 8 to 10% chlorine gas in the presence of about 1<B>%</B> iron filings, then heat slowly. The mixture is stirred vigorously during the chlorination, then it is neutralized, then it is washed and the benzolic hydrocarbons are distilled as described in Example 1.

<I>Example 6:</I> As in Example 5, a fraction of crude benzole is treated, boiling up to 105 o C and containing about 8% impurities, but making use, as a carrier - chlorine, from 1 to. 3%; finely divided iron sulphide. <I>Example 7:</I> A high boiling point light oil fraction containing mainly gasolines or benzines (xylenes and similar bodies) together with 40 to 50% impurities, mainly coumarone and indene; 1 to 3% of benzol sulfochloride is added, then approximately 8 to 20% of chlorine gas is passed through. The amount of chlorine needed depends on the particular crude oil sample. In general, chlorination will continue until a distilled sample gives a colorless, clear reading in the normal test. <B>sulfuric</B> acid. When the chlorination is complete, the mixture is neutralized and washed, as in example 1, then the solvent naphtha is distilled in a state of high chemical purity. A large amount of light-colored liquid remains in the vessel where the distillation takes place and is drawn off. This residue consists, in large part, of bodies containing coumarone and indene which can be partially chlorided or polymerized. This product can be used as a raw material for the preparation of coumarone and indene resins and is superior to residues obtained by washing with sulfuric acid, since the chlorine treatment does not tend to decompose the bodies containing coumarone and indene. In many cases, the residue is sufficiently resinified that it can be used directly, without further polymerization, in which case it is usually desirable to wash the product to remove water-soluble compounds.

<I>Example 8:</I> A low-boiling crude benzol fraction containing about 2-3% toluol and impurities is column distilled as described above and introduce chlorine gas at the bottom of the column, adjusting the rate of introduction so that the distillate, after washing, does not give color in the normal sulfuric acid test. The distillate can be collected and washed with water or with a dilute alkali; or the vapors can be condensed in a scrubber, or the HCl removed in any other suitable way. The process can be made continuous by adding new quantities of crude benzol to the still or distillation column and occasionally removing impurities from the bottom of the still by means of a drain pipe. chlorureas. The chlorinated toluol can be extracted from the residual sludge when it exists in sufficient quantities to justify this extraction. The other constituents of the sludge can also be used for various purposes. as described above. Example <I>9:</I> A low-boiling benzol fraction is distilled as described in the example. 8, but the vapors in the column are illuminated with a quartz lamp, mercury vapor lamp, or other source of light rich in ultraviolet rays. The chlorination is faster and the distillation and the introduction of chlorine can be accelerated, or, if desired, a shorter, less efficient column can be used. The distillate is washed as described in the previous examples. The impurities converted are removed as described in Example 8. Example 10 A low-boiling crude benzol fraction containing 2 to 5% of toluol and impurities, as described; but instead of introducing chlorine alone into the column, a mixture of chlorine and a small quantity of sulphurous anhydride is introduced. The latter and the chlorine react to form sulfuryl chloride which strongly catalyzes the chlorination of impurities and allows a considerable increase in the yield, with the same apparatus. The sulphide chloride, which boils at a relatively high temperature, returns to the still, where it is removed with the residual sludge. Small amounts of unreacted sulfur dioxide may sometimes pass into the distillate, but are removed by the alkaline wash.

<I>Example</I> 11 A low-boiling benzol fraction is stripped as described in Examples 8 and 9; but, instead of making use of fragments of inert matter in the column, use is made of fragments of iron. The iron acts as a catalyst and allows rapid purification, but care must be taken not to greatly exceed the quantity of chlorine necessary to combine with the impurities and with the toluol, because in the presence of a sufficient quantity of chlorine, the iron catalyzes the chlorination of the benzol itself. <I>Example 12:</I> A crude benzol fraction with a low boiling point, containing in about 4% impurities. Liquid chlorine is then passed through in a thin stream, with constant agitation, until about 6-8% by weight chlorine has been absorbed. The stream of chlorine is then stopped and the mixture is washed with water, then with a dilute alkali. The washed product is then dried and the benzol is distilled. Instead of washing with water and with diluted alkali, ordinary commercial soda, finely divided, may be added in a quantity approximately equal to the chlorine absorbed. <I>Example 13:</I> Light oil (obtained for example by distillation of coal tar) is treated with caustic soda to remove the phenols, fractionated and a crude benzol fraction is taken from up to 105 C. This fraction is treated with 1 to 2 of sulfuric acid at 60 Baume, the addition of the acid taking place gradually and accompanied by vigorous stirring. After about 25 minutes, the stirring is stopped, the acid is allowed to settle for about 30 minutes, then the mixture is drawn off. This acid, known as pyridine acid, removes the. most of the pyridine. The mixture is allowed to stand for another 20 to. 30 minutes and a new acid deposit is removed. You can then wash the product with water and pass 6 to 8%, by weight, of chlorine at the temperature of the. room we are operating. The introduction must be done by means of a chlorine distributor to ensure a perfect distribution. The introduction of chlorine can also be done before washing. water, in which case the remaining sulfuric acid acts as a chlorine carrier. In either case, the solution becomes dark and the chlorine is quantitatively absorbed. It is advantageous to add 0.5 to 1% sulfur or ferric chloride as chlorine carrier to accelerate the chlorination, in particular carbon disulphide.

Once the reaction is complete, the mixture is washed with water, then with an alkali solution, dried and the benzol distilled. A single distillation in the distillation column is usually sufficient.

Corrosion of the chlorinator, due to the formation of hydrochloric acid, can be prevented by adding ordinary commercial soda ash or lime to the mixture, before chlorination, to neutralize the hydrochloric acid. form. It is also possible to add other bases, they are even advantageous in certain cases.

The benzolic hydrocarbons thus purified are of high chemical purity and contain only small quantities of carbon tetrachloride. As the product is sulfur free and contains only a little carbon tetrachloride, it is suitable for the production of derivatives for use in catalytic reactions. Chlorine products remaining after distillation can be used as a solvent. It is either possible to use all of the impurities in this way, or to fractionate them to produce solvents of various boiling points. Example <I>II:</I> Phenols and bases are freed, in the usual way, by means of alkali and sulfuric acid, from a fraction of crude benzol boiling up to 105 C. the product with 0.2 to 0.5% by volume of 65-66 Baume sulfuric acid, stirring vigorously. Stirring is continued for 10 to 15 minutes, taking care that the oil does not become too hot. The mixture is then allowed to stand and the tar acid is drawn off, which settles in about 10 minutes. At the end of a further period of 10 minutes, another portion of the acid will have settled and this is also drawn off, after which the oil is washed with cold or lukewarm water and another wash with an acid solution is not necessary. The benzol thus treated is partially freed of its impurities by sulfuric acid and is then subjected to the chlorination process, by passing approximately 3% of gaseous chlorine, at the temperature of the room where one operates, by agitating vigorously. The color of the oil becomes darker and when a distilled sample no longer shows any color with sulfuric acid, in the normal test, the operation is complete. An addition of about 0.5% aluminum chloride as a chlorine carrier is advantageous, but not absolutely necessary. On the other hand, the addition of enough calcium carbonate to neutralize the hydrochloric acid formed during the reaction is very desirable. Once the reaction is complete, the mixture is washed with water, then with alkali until it is neutral and the benzol is distilled. A single distillation is usually sufficient.

The benzolic hydrocarbons thus purified do not contain sulfur compounds and contain only small amounts of carbon tetrachloride.

The residue of the. !distillation consists of a chlorinated oil and can be distilled to give a colorless or weakly colored solvent suitable for many industrial uses. Example <B><I>15:</I></B> Treating with alkali, to remove the phenoids, then with dilute acids, to remove the bases, a fraction of crude toluol boiling from 105 to 120 C. Then pour gradually, stirring vigorously, 0.2 to 0.5% sulfuric acid at 60-66 Baume. Stirring is maintained for fifteen to twenty minutes, then the acid is left to deposit and drawn off as much as possible. The remaining acid is then washed and the crude toluol fraction is partially chlorided with about 2.5%. 3.5% chlorine gas diluted with air. The color of the oil becomes darker and the process is continued until a distilled sample gives completely negative results in the sulfuric acid test. Use can advantageously be made of copper chloride as a chlorine carrier. Neutralizing agents can be added at the beginning of the chlorination process, or once it is finished; calcium carbonate is very satisfactory for this purpose.

Once the chlorination is complete and after flooding the mixture has been neutralized, the toluol is distilled. The chlorine residue can also be distilled to yield colorless or light yellow chlorine products which are suitable for many uses, particularly as inexpensive solvents.

<I>Example 16:</I> 0'n first treats with alkalis, to remove phenols, a crude heavy benzol fraction (naphtha solvent.) distilled from light oil and boiling at 130 to 150 C. The pyridine-containing bases are removed in the usual way with sulfuric acid. When the pyridine content is very high, several washings with sulfuric acid (various strengths may be desirable). The pyridine-free oil, which contains mainly zylol and similar compounds, is partially chlorided using a little bromine, or a bromide, as a catalyst The chlorine is passed through with vigorous stirring and, if desired, adding a small quantity of benzol sulphochloride as a catalyst, until a distilled sample does not give a yellow color with sulfuric acid. Small amounts of sodium hydroxide can be added to prevent corrosion of the containers. The product is then washed with water and distilled, giving a distillate freed of water which is fractionated, and the xylol fraction is obtained between 136.5 and 139 C. The tylol thus produced is of extraordinarily good quality and is well suited for the production of intermediates. can be used as a high boiling point solvent. <I>Example 17:</I> A fraction of crude heavy benzole, boiling between 140 and 160 C, is stripped of phenols and bases and subjected to a short washing with sulfuric acid, as described in example 16. Acid washing is done with. sulfuric acid at 65-66 Baumé, at, the, quantity of 0.3-0.6%. The washing should last about fifteen to twenty minutes and the acid is then left to deposit, which is drawn off as much as possible. The crude heavy benzole which has been subjected to this partial purification gives a dark brown test with sulfuric acid.

After having washed the oil thus treated with water, 4 to 5% of chlorine is passed through it, with violent agitation, in the form of a thin stream of liquid chlorine which is dispersed under the surface; the temperature is preferably maintained below 30° C. Among other impurities, cyclopentadiene, dic@-- elopentadiene, styrolene, hydrindene, and others, are transformed into high boiling point chlorinated products , while cou-marone -and indene are little, if at all, attacked. The product is washed with water in the usual way and distilled to give a colorless oil. Aromatic hydrocarbons can be removed therefrom by polymerizing the bodies containing the. coumarone and indene with concentrated sulfuric acid, or by distilling with or without steam. The aromatic hydrocarbons, as well as the heavy benzole purified itself, are excellent solvents and do not contain sulfur compounds or compounds which would result in darkening of the color from long exposure to there. light. <I>Example 18:</I> On: get rid of. bases and phenols in the ordinary way, an oil fraction (distillate of coal tar) boiling at 160 to 180 C and washed once or twice with a total amount of 0.5 to 1% of sulfuric acid at 65-66 Baume. Wash carefully to remove sulfuric acid as described in Example 17 and chloride the product with chlorine gas. In addition to the impurities described in the previous example, the heavy oily materials which are present are transformed into chlorinated products with a high boiling point, so that after distillation a colorless heavy benzol is obtained. The subsequent treatment of the heavy benzol is carried out in the same way as described in example 17.

Claims (3)

CLAIM Process for purifying oils formed from aromatic hydrocarbons and containing impurities, characterized by a treatment with halogens or substances providing halogens, having the effect of a selective halogenation of the impurities of the oil thus treated, converting some of the impurities into substances readily separable from the aromatic hydrocarbons present and others into substances of a non-harmful nature. SUB-CLAIMS: 1 Process according to claim, characterized in that the oils formed from aromatic hydrocarbons are subjected before the halogenation of the impurities to a treatment at least with strong sulfuric acid. 2 Process according to claim, characterized in that the oils are subjected, after the selective halogenation of the impurities, to a treatment with sulfuric acid. 3 Process according to claim, charac terized in that the halogenation takes place in the presence of a halogen body carrier. 4 Process according to claim<B>,</B> and sub-claim 3, characterized in that the halogenation is carried out in the presence of sulfur as halogen carrier. Process according to claim and sub-claim 3, characterized in that the halogenation takes place in the presence of sulfur compounds which catalyze the halogenation of aliphatic, alicyclic and heterocyclic compounds. 6 Process according to claim, characterized in that the halogenation is carried out under physical conditions such that the halogenation is favored. 7 P@roc & dice according to the. claim and the. subclaim 6, characterized in that the halogenation is carried out under physical conditions such that the halogenation of aliphatic, alicyclic and heterocyclic compounds present in the oil to be purified is favored. 3 Process according to claim, charac terized in that use is made, as halogenating agent, of a halogenated body in the liquid state so as to use the latent heat of evaporation: of the halogenated body, to maintain the The reaction temperature is within favorable limits. Process according to claim, characterized in that the halogenation is carried out in the presence of an antacid substance to neutralize any acid formed during the reaction. 11. Process according to claim and sub-claim 10, characterized in that at least part of the halogenation takes place in the vapor phase. halogenation takes place in the vapor phase and in the presence of gaseous halogen carriers.1 Process according to claim, characterized in that at least part of the reaction products of impurities and !of the hologen body. Process according to Claim, characterized in that the reaction products of the impurities formed by the halogenation are separated from the aromatic hydrocarbons by fractional distillation. Process according to claim and sub-claim 1, characterized in that the halogenation is carried out in the presence of at least traces of sulfuric acid originating from the preliminary treatment of the oil to be purified, this acid acting as a halogenation catalyst. 15 Process according to claim and sub-claims 10 and 11, characterized in that the oil to be purified is distilled, the vapors are subjected to a selective ha- logenation of the impurities in the vapor phase and that the products of reaction are fractionally condensed to separate them from the aromatic hydrocarbons.