GB2060670A

GB2060670A - Process for the Separation of Anthraquinone Compounds using Fractional Crystallisation

Info

Publication number: GB2060670A
Application number: GB7935317A
Authority: GB
Original assignee: Yorkshire Chemicals Ltd
Current assignee: Yorkshire Chemicals Ltd
Priority date: 1979-10-11
Filing date: 1979-10-11
Publication date: 1981-05-07
Also published as: GB2060670B

Abstract

There is described a simplified process for separation of certain alpha , alpha '- disubstituted anthraquinones of the formula <IMAGE> in which R<1> represents hydrogen or an optionally substituted alkyl, cycloalkyl or aryl group, R<2> represents an optionally substituted alkyl cycloalkyl or aryl group, Y represents the link -CO-, -SO-, or -SO2, and one Z represents the group <IMAGE> whilst the other represents a hydrogen atom, from mixtures also containing alpha -monosubstituted and alpha , beta '- disubstituted anthraquinones which comprises fractional crystallisation of the mixture. The process is especially useful for separating the waste liquors arising after separation of the majority of both the 1,5- and 1,8- anthraquinone disulphonic acids formed by the conventional mercury catalysed disulphonation of anthraquinone. The waste liquors are first halogenated to produce mono and dihalogenated anthraquinones and then all halogens in the alpha - positions are acylated and the resultant mixture separated by fractional crystallisation.

Description

SPECIFICATION Process for the Separation of Anthraquinone Compounds The process of the invention provides a means for the separation of aa'-disubstituted anthraquinone compounds from mixture which also contain a-monosubstituted and a0'-disubstituted anthraquinone compounds and allows the residual mixture of a-monosubstituted and a,B'- disubstituted anthraquinones to find use as a source of valuable intermediates for the manufacture of dyes.

The mixtures of compounds which are the subject of the present invention are derivatives of mixtures of anthraquinone disulphonic acids. The conventional mercury catalysed disulphonation of anthraquinone gives rise to a mixture containing 1,5, 1,6, 1,7 and 1,8 anthraquinone disulphonic acids along with small amounts of the a-monosulphonic acid. It is established practice that the commercially valuable 1,5- and 1 8-isomers are isolated by fractional crystallisation either separately or together and the remaining liquors, containing mainly the 1,6- and 1,7-isomers plus residual amounts of the amonosulphonic acid and any aa'-isomers not isolated, are run to waste.This discarding of the a0'- isomers represents a severe limit to the efficiency of the sulphonation process since these isomers contribute typically 3040% of the total yield of disulphonic acids produced in the reaction. It is the object of the present invention to provide a means for the isolation of derivatives of these a0'- disubstituted anthraquinone compounds in a form and purity which allows them to be exploited as intermediates for the manufacture of dyes.

The high water solubility of the a0'-anthraquinone disulphonic acids prevents their efficient isolation by the conventional methods used for the cra'-isomers, for example salting out with sodium or potassium chloride. However, it is known that halogenation, particularly chlorination, of aqueous solutions of anthraquinone disulphonic acids yields the corresponding water insoluble dihaloanthraquinones which may be readily isolated by filtration. Application of this halogenation process to the waste liquors arising after the separation of the majority of both the 1,5- and 1,8anthraquinone disulphonic acid isomers results in a mixture of haloanthraquinones which is particularly rich in the 1,6- and 1,7-isomers, although the 1,5- and 1 ,8-isomers and a-monohaloanthraquinone are also present but to a lesser degree.However, the presence of the aa'-dihaloanthraquinones greatly restricts the uses to which this mixture of haloanthraquinones may be put, since the presence of compounds containing two a-halogen atoms can give rise to undesirable impurities when the mixture is used as an intermediate for the manufacture of dyes.

Other attempts have been made to make use of the 1,6- and 1 ,7-anthraquinone disulphonic acid isomers via mixtures of products obtained by direct halogenation. For example, mixtures of chloroanthraquinones may be separated by vacuum fractional distillation (see for example BP 1 51 8,871) and mixtures of 1,6- and 1 ,7-dichloroanthraquinone thus obtained may be aminated by known methods (see for example Japanese Patent 76-37921) and used as intermediates in the manufacture of dyes. However such distillation processes require extensive plant equipment and severe conditions. The yield of efficiently separated products is comparatively low.

It has now been found that the aa'-disubstituted compounds may be separated from mixtures also containing a-monosubstituted and a,B'-disubstituted anthraquinones in a surprisingly efficient manner by conversion of all halogen atoms occupying a-positions to the corresponding acylamino derivatives, followed by separation of the resultant a'-diacylaminoanthraquinones by virtue of their lower solubility in certain organic solvents under defined conditions of temperature and concentration.

The present invention thus provides a process for the separation of compounds of formula I:

in which R' represents hydrogen or an optionally substituted alkyl, cycloalkyl or aryl group, R2 represents an optionally substituted alkyl, cycloalkyl or aryl group, Y represents the link -CO-, -SO-, or -SO2-, and one Z represents the group

whilst the other represents a hydrogen atom.

from mixtures which also contain compounds of formula II

in which one X1 represents a halogen atom whilst the other represents a hydrogen atom, or both represent hydrogen atoms, and R', R2 and Y are as described above, by fractional crystallisation from an organic solvent.

The said mixture of compounds of formulae I and Ills, in preferred embodiments of the invention, derived from mixtures of mono- and dihaloanthraquinones represented by formula Ill

in which X2 represents a halogen atom, X3 represents a halogen or hydrogen atom, and X3 may be in any one of the four possible positions in ring B, by replacement of all halogen atoms occupying a-positions with the group

As a result of the process of the invention the more soluble a,B'-disubstituted anthraquinone compounds of formula II are isolated substantially free of contamination from the less readily soluble au::'-disubstituted anthraquinones of formula I, the latter being present typically in amounts much less than 5% by weight, and may now be successfully used as valuable intermediates for the manufacture of dyes. Similarly, the aa'-diacylaminoanthraquinones of formula I are isolated substantially free of contamination from compounds of formula II and there is thus provided an extra source of the already commercially exploited cga'-disubstituted anthraquinone derivatives.

The separation process is applicable to mixtures of acylaminoanthraquinone compounds of formula I and II which are derived from mixtures of mono- and dihalogenated anthraquinones, represented by formula Ill, having a wide range of composition. Of particular advantage is the application of the process of the invention to the acylamino derivatives of the mixture of mono- and dihalogenated anthraquinones, which are produced by halogenation of the waste liquors arising after the separation of the majority of both the 1,5- and 1 ,8-anthraquinone disulphonic acids formed by the conventional mercury-catalysed disulphonation of anthraquinone. However, the process may also be applied to the mixture of acylaminoanthraquinones derived from mixtures of anthraquinone disulphonic acids from which none or only part of the as disulphonic acids have been isolated.

In contrast to such processes as disclosed for example in BP 1 ,5 1 8,871, the process of the present invention provides a more simple and direct method of obtaining mixtures of compounds of formula II which are derivatives of 1 -halo and 1,6- and 1 ,7-dihaloanthraquinone, from mixtures of 1 halo- and 1,5-, 1,6-, 1,7- and 1 ,8-dihaloanthraquinones.

The process is carried out under mild conditions, in existing readily available plant facilities and with surprisingly high efficiency of separation. According to the process, mixtures of 1 -acylamino and 1-acylamino-6 (and 7)- haloanthraquinones are obtained by the efficient separation of reaction products derived from mixtures of halogenanthraquinones and not by complex separation procedures carried out on the mixtures of halogenanthraquinones themselves, prior to further reaction.

The mixture of acylaminoanthraquinones represented by formula I and II may be prepared by the reaction of the mixture of compounds of formula lil with ammonia or amines of formula NH2Rl, where R1 is as described above, followed by acylation. Alternatively the transformation maybe carried out by reacting the mixture of compounds of formula Ill with amides of formula NH2-Y-R, followed by optional alkylation, R2 and Y having the meanings described above. The resultant product of such transformations is a mixture of compounds of formulae I and II.

The mixture of haloanthraquinones represented by formula Ill is subjected to amination or amidation such that only halogen atoms in a-positions are replaced by amino or amido groups. The amination reaction may be carried out by conventional methods using ammonia or amines for example in organic solvents, at temperatures between room temperature and the boiling point of the solvent, optionally under pressure, in the presence of a suitable catalyst and an acid binding agent, or in an aqueous medium under pressure at temperatures between 500C and 2500C in the optional presence of a suitable catalyst and an acid binding agent.

Suitable amines which may be used are ammonia or aliphatic, araliphatic, cycloaliphatic or aromatic primary amines. Examples of such amines are methylamine, ethylamine, n-propylamine, isopropylamine, 3-methoxy-propylamine, 3-dimethylaminopropylamine, n-butylamine, iso-butylamine, sec-butylamine, cyclohexylamine, benzylamine, aniline and o-, m-, or p-toluidine. Ammonia is preferred.

Examples of preferred organic solvents are halogenated or nitrated hydrocarbons of the aliphatic and aromatic series, for example, chlorobenzene, o-dichlorobenzene, trichlorobenzene, 1,2dichloroethane, 1,1 ,2,2,-tetrachloroethane or nitrobenzene. Hydrophilic solvents may be employed for example, dimethylformamide, dimethylsulphoxide, pyridine, N-methyl-2-pyrrolidone, triethanolamine, dioxan or water.

Acid binding agents may be employed to neutralise acid formed as a product of the condensation reaction. They may be salts of inorganic or organic acids, for example, sodium carbonate or acetate, potassium carbonate or acetate, or inorganic bases such as magnesium oxide or calcium oxide, or organic bases such as pyridine, piperidine or triethanolamine.

The subsequent acylation of the mixture of products from the amination of mixtures of chloroanthraquinones may be carried out by using conventional acylating agents in organic solvents at temperatures between room temperature and the boiling point of the solvent, in the optional presence of an acid binding agent. Acylating agents which may be used are anhydrides, for example acetic anhydride, or acid chlorides of aliphatic, araliphatic, cycloaliphatic, or aromatic carboxylic, sulphonylic or sulphinylic acids. Particularly efficient separations are achieved in the final stage of the process of the invention when the acylating reaction introduces a substituent of large molecular size, for example an aromatic group.Hence preferred acylating agents are: benzoyl chloride, phenylacetyl-chloride, ptoluyl chloride, benzene sulphonyl chloride, p-toluene sulphonyl chloride, benzene sulphinyl chloride and p-toluene sulphinyl chloride.

Suitable solvents which may be mentioned are, pyridine, toluene, chlorobenzene, odichlorobenzene and nitrobenzene. Acid binding agents which may optionally be present are conventional and may be as described previously.

Alternatively the haloanthraquinone mixture, represented by formula I may be converted directly to their a-acylamino- derivatives by conventional methods by reacting mixtures of haloanthraquinones with amides of formula NH2-Y-R2, wherein R2 and Y are as described previously.

The reaction may be carried out in a range of organic solvents, examples of preferred solvents being: toluene, chlorobenzene, o-dichlorobenzene, and nitrobenzene. The amidation is carried out at temperatures between room temperature and the boiling point of the solvent used, in the optional presence of a conventional acid binding agent, which may be as described previously, and the optional presence of a suitable catalyst such as cupric acetate or cupric sulphate.

Examples of classes of amides which may be used are acid amides of aliphatic, araliphatic, cycloaliphatic or aromatic carboxylic, sulphonylic or sulphinylic acids, but it is preferred to use amides which carry a substituent of large molecular size, such as an aromatic group, since particularly efficient separations are then achieved in the final stage of the process of the invention. Preferred amides are: ptoluenesulphonamide, benzene sulphonamide, benzamide and benzene sulphinamide.

The products obtained from the above amidation reactions may then be optionally alkylated by known methods using conventional alkyllating agents such as diethylsulphate, dimethylsulphate, bromomethane and methyl p-toluene sulphate, to give compounds of formulae I and II where R represents an alkyl group.

The invention provides a process by which the mixtures of compounds of formula I may be separated from the mixtures which also contain compounds of formula II and which are produced as described above. The separation is achieved in a surprisingly simple and efficient manner by fractional crystallisation from suitable organic solvents. Preferred solvents are optionally substituted aliphatic, cycloaliphatic or aromatic hydrocarbons, examples being: toluene, chlorobenzene, o-dichlorobenzene, nitrobenzene, cyclohexane and n-hexane. It is particularly convenient to use the solvent in which the acylation or amidation reaction has been carried out since no intermediate isolation stage is then necessary.

By suitable adjustment of the concentration of the liquor containing the mixture of compounds of formulae I and II, the former components may be efficiently separated by filtration. Separation can be achieved over a wide range of temperatures up to the boiling point of the solvent or mixture of solvents employed but it is preferred to carry out the separation at temperatures between OOC and 30"C.

Particularly efficient separations are achieved when the group -Y-R2 in formulae I and II corresponds to the group -CO-C6H5 and when nitrobenzene is used as the solvent. Compounds of formulae II are then isolated from the filtrates by complete removal of solvent, for example, by direct distillation or by steam distillation, or by increasing the concentration of the filtrates and inducing crystallisation of product by cooling or optionally by the addition of a suitable precipitant such as methanol or ethanol.

Compounds of formula II are thus obtained typically containing less than five percent, by weight, of compounds of formula I, which in turn are obtained typically containing less than five percent, by weight, of compounds of formula II. Such an efficiency of separation is outstanding when the simplicity of the process is considered.

Compounds of formula II when of a purity as high as that produced by the process of the invention are valuable intermediates for the synthesis of dyes. For example hydrolysis of compounds of formula II yields a-amino- or a-alkylaminoanthraquinone derivatives which may be sulphonated and brominated to give mixtures of 1-amino (or alkylamino)-4-bromoanthraquinone-2-sulphonic acid and 1 amino (or alkylamino)-4-bromo- 6 (or 7)-halo anthraquinone-2-sulphonic acid which may be used in the preparation of various classes of dyes.Alternatively the products of hydrolysis of compounds of formula II may be readily halogenated, for example with bromine to give mixtures of 1-amino (or alkylamino)-2,4-dibromoanthraquinone and 1-amino (or alkylamino)-2,4-dibromo-6 (or 7)-haloanthraquinones and these in turn may be hydrolysed to give mixtures of 1-amino (or alkylamino)-2bromo-4-hydroxyanthraquinone and 1-amino (or alkylamino)-2-bromo-4-hydroxy-6 (or 7)haloanthraquinones.

Compounds of formula I may be hydrolysed to give aa'-diamino- (or aa'-dialkylamino)- anthraquinones which are also valuable as intermediates for dyestuffs. Compounds of both formulae I and II are themselves valuable intermediates for Vat dyestuffs.

The process according to the invention will be explained in more detail with the aid of examples which follow, in which parts and percentages are by weight.

In the following five examples the starting materials used are mixtures of dichloroanthraquinones obtained from the chlorination of the waste liquors from the mercury catalysed disulphonation of anthraquinone, obtained after the separation of 1,5- and 1,8-anthraquinone disulphonic acid. The aqueous solution of anthraquinone sulphonic acids is treated in a conventional manner with sodium chlorate and hydrochloric acid at 98-1 050C and the mixtures of chloroanthraquinones obtained typically have a composition within the range shown below.

1,6-Dichloroanthraquinone 35-40 1,7-Dichloroanthraquinone 35-40 1,5-Dichloroanthraquinone 8-12 1,8-Dichloroanthraquinone 8-12 a-Monochloroanthraquinone 1-5 The process of the invention is particularly applicable to mixtures of this type but is not restricted to this range of composition.

Example 1 a) 62.2 Parts of a mixture of chloroanthraquinones (of composition described above) are heated in an autoclave with 1 50 parts of 30% strength aqueous ammonia solution and 450 parts of water for 24 hours at 21 00C with efficient stirring. After cooling to room temperature the product is filtered off, washed alkali-free with cold water and dried, giving 43.8 parts of a mixture containing 1 ,5- and 1,8 diaminoanthraquinone, 1 -amino-6-chloroanthraquinone, 1 -amino-7-chloroanthraquinone and 1aminoanthraquinone.

b) 43.8 Parts of the mixture of products obtained are added with stirring to 307 parts of nitrobenzene and the mixture is heated to 1 500C over 1 hour. A solution of 44.2 parts of benzoyl chloride in 80 parts of nitrobenzene is added dropwise at 1 500C and the mixture is stirred for 1 hour at 1 500C after the final addition. The reaction mixture is allowed to cool and is stirred at room temperature for 1 6 hours.

The material which has crystallised is filtered off, washed with 350 parts of nitrobenzene and dried. This yields 10.5 parts of a mixture comprising 98% 1,5- and 1 ,8-dibenzoylaminoanthraquinone.

The combined filtrates and nitrobenzene washings may be treated either by i) concentration of the liquor by distillation of 600 parts of nitrcoenzene, followed by the addition of 730 parts of methanol to the stirred residue, which has been cooled to room temperature. After stirring for 1 6 hours at room temperature the precipitated product is filtered off, washed with 365 parts of methanol and dried, yielding 41.9 parts of a mixture corresponding to formula II of compositions: 1-benzoylamino-6-chloroanthraquinone 45 1 -benzoylamino-7-chloroa nthraquinone 48 1-benzoylaminoanthraquinone 4 1,5-(and 1 ,8-)dibenzoylaminoanthraquinone 3 or ii) removal of the nitrobenzene by conventional steam distillation.The aqueous residues are cooled to room temperature and the solid product is collected on the filter, washed with 292 parts of methanol and dried. This yields 47.5 parts of a mixture corresponding to formula II of composition similar to that described above.

Example 2 43.8 Parts of a mixture of products obtained according to Example 1 a are added with stirring to 280 parts of toluene and the mixture is heated to 1 050C over 1 hour. A solution of 48.6 parts of phenylacetyl chloride in 75 parts of toluene is added dropwise at 1 050C and the mixture is stirred for 1 hour at 1 050C after the final addition. The reaction mixture is allowed to cool and stirred at room temperature for 20 hours.

The material which has crystallised is filtered off, washed with 250 parts of toluene and dried.

This yields 10.8 parts of a mixture of 1,5- and 1 ,8-diphenylacetylaminoanthraquinone.

The combined filtrates and toluene washings are concentrated by distillation of 450 mls of toluene, followed by the addition of 700 parts of methanol to the stirred residue, which has been cooled to room temperature. After stirring for 1 6 hours at room temperature the precipitated product is filtered off, washed with 300 parts of methanol and dried. This yields 43 parts of a mixture of 1 phenylacetyiamino-6-chloroanthraquinone, 1 -phenylacetylamino-7-chloroanthraquinone and 1phenylacetylaminoanthraquinone.

Example 3 a) 29.2 Parts of a mixture of chloroanthraquinones (of composition described above) and 300 parts of water are charged into an autoclave. 31.5 Parts of 40% aqueous monomethylamine and 0.10 parts of cupric sulphate are added to the stirred mixture. The autoclave is sealed and heated at 125 1300for 16 hours.

After cooling to room temperature the product is filtered off, washed alkali-free with cold water and dried, yielding 24.6 parts of a mixture containing 1,5- and 1 ,8-di(N-methylamino-anthraquinone, 1 -N-methylamino-6-chloroanthraquinone, 1 -N-methylamino-7-chloroanthraquinone and 1-Nmethylaminoanthraquinone.

Alternatively a similar mixture of products is obtained in the following reaction: b) 29.2 Parts of a mixture of chloroanthraquinones (of composition described above) are added to 400 parts of chlorobenzene, with stirring, at 800 C. The reaction mixture is heated to 1000C and methylamine gas is passed through the solution for 6 hours. After cooling to room temperature the mixture is drowned out into 750 parts of methanol and after stirring for 3 hours the product is filtered off, washed with 200 parts of methanol and dried. This yields 24.1 parts of a mixture of products of similar composition to those obtained in example 2(a).

c) 24.5 Parts of the mixture of products obtained in 2(a) or 2(b) are added with stirring to 80 parts of nitrobenzene and the mixture is heated to 1 500C over 1 hour. A solution of 20 parts of benzoylchloride in 42 parts of nitrobenzene is added dropwise at 1 500C and the mixture is stirred for 10 hours at 1 500C after the final addition. The reaction mixture is allowed to cool and is stirred at room temperature for 20 hours.

The crystallised material is filtered off, washed with 75 parts of nitrobenzene and dried. This yields 5.4 parts of a mixture of 1,5- and 1 ,8-di(N-methyl-N-benzoylamino) anthraquinone.

The combined filtrates and nitrobenzene washings are concentrated by distilling off 230 parts of nitrobenzene and then 500 parts of methanol are added to the residue which has been cooled to room temperature. After stirring for 1 6 hours at room temperature the precipitated product is filtered off, washed with 1 50 parts of methanol and dried. This yields 23.5 parts of a mixture of 1 -N-methyl-N- benzoylamino-6-chloroanthraquinone, 1 -N-methyl-N-benzoylamino-7-chloroanthraquinone and 1-Nmethyl-N-benzoyl-anthraquinone.

Example 4 10 Parts of a mixture of chloroanthraquinones (of composition described above) are added, with stirring, to 1 30 parts of ortho dichlorobenzene. 0.35 parts of cupric acetate, 3.3 parts of sodium acetate and 1 5 parts of benzamide are added. The mixture is heated to 1 750C and maintained for 24 hours. After cooling to room temperature and stirring for a further 1 6 hours, crystallised material is filtered off, washed with 75 parts of orthodichlorobenzene and dried. This yields 2.20 parts of a mixture of 1,5- and 1 ,8-dibenzoylaminoanthraquinone.

The combined filtrates and washings are concentrated by the removal of 1 65 parts of ortho dichlorobenzene by distillation and the cooled residue is drowned out into 500 parts of methanol, with stirring. After stirring this mixture for 1 6 hours the product is filtered off washed with 100 parts of methanol and dried, yielding 8.35 parts of a mixture of 1 -benzoylamino-6-chloroanthraquinone, 1 - benzoylamino-7-chloroanthraquinone and 1 -benzoylamino-anthraquinone.

Example 5 10 Parts of a mixture of chloroanthraquinones (of composition described above) are added to 120 parts of nitrobenzene with stirring. 20 parts of p-toluenesulphonamide, 0.35 partsof cupric acetate and 3.3 parts of sodium acetate are then added, the stirred mixture is heated to 1 750C and maintained at this temperature for 24 hours. After cooling to room temperature and stirring for 16 hours crystallised material is filtered off, washed with 70 parts of nitrobenzene and dried. There are thus obtained 2.6 parts of a mixture of 1,5- and 1 ,8-di(4'-methylbenzenesulphonamido)anthraquinone.

The combined filtrates and nitrobenzene washings are concentrated by distilling off 1 50 parts of nitrobenzene and by drowning out the cold residue into 500 parts of methanol, with stirring. When crystallisation is complete the product is filtered off, washed with 100 parts of methanol and dried, yielding 10.6 parts of a mixture of 1 -(4'-methylbenzenesulphonamido)-6-chloroanthraquinone, 1 -(4'methylbenzenesulphonamido)-7-chloroanthraquinone and 1-(4'methylbenzenesulphonamido)anthraquinone.

Example 6 In the following example the starting material used is a mixture of chloroanthraquinones obtained from the chlorination of the aqueous solutions of anthraquinone disulphonic acids obtained from the mercury catalysed disulphonation of anthraquinone after the separation of 1,5-anthraquinone disulphonic acid.The mixtures of chloroanthraquinones obtained, after conventional chlorination, typically have a composition within the range shown below:- 1 ,8-Dichloroanthraquinone 5565 1,7-Dichloroanthraquinone 16-20 1,6-Dichloroanthraquinone 14-18 1,5-Dichloroanthraquinone 3-5 .1-Chlornanthraquinone 1-3 a) 62.2 Parts of a mixture of chloroanthraquinones (of composition described above) are heated in an autoclave with 200 parts of 30% strength ammonia solution and 400 parts of water for 24 hours at 2200C with efficient stirring.After cooling to room temperature the product is filtered off, washed alkali free with cold water and dried, giving 46.6 parts of a mixture containing 1,5- and 1,8 diaminoanthraquinone, 1 -amino-6-chloroanthraquinone, 1 -amino-7-chloroanthraquinone and 1aminoanthraquinone.

b) 46.6 Parts of the mixture of products obtained are added with stirring to 330 parts of nitrobenzene and the mixture is heated to 1 500C over 1 hour. A solution of 50 parts of benzoylchloride in 90 parts of nitrobenzene is added dropwise at 1 500C and the mixture is stirred for 1 hour at 1 500C after the final addition. The reaction mixture is allowed to cool and when crystallisation is complete the product is filtered off, washed with 350 parts of nitrobenzene and dried. This yields 51.1 parts of 1,8dibenzoylaminoanthraquinone containing 10% of 1 ,5-dibenzoylaminoanthraquinone.

The combined filtrates and nitrobenzene washings are then steam distilled in a conventional manner to remove all traces of organic solvent and the resultant aqueous residues are cooled to room temperature. The solid product is collected on the filter, washed with 310 parts of methanol and dried.

This yields 22.5 parts of a mixture corresponding to formula II of composition: 1 -benzoylamino-7-chloroanthraquinone 49 1-benzoylamino-6-chloroanthraquinone 44 1-benzoylaminoanthraquinone 5 1,8-dibenzoylaminoanthraquinone 2

Claims

1. A process for the separation of compounds of formula I

in which R1 represents hydrogen or an optionally substituted alkyl, cycloalkyl or aryl group, R2 represents an optionally substituted alkyl, cycloalkyl or aryl group, Y represents the link -CO-, -SO-, or SO2, and one Z represents the group

whilst the other represents a hydrogen atom, from a mixture which also contains compounds of formula II

in which one X1 represents a halogen atom whilst the other represents a hydrogen atom, or both represent hydrogen atom, and R1, R2 and Y are as described above, which comprises fractional crystallisation of said mixture from an organic solvent.

2. A process as claimed in claim 1, in which the mixture of compounds of formulae I and II is derived from mixtures of mono- and dihaloanthraquinones represented by formula Ill

3. A process as claimed in claim 2, in which the mixture is a mixture of acylamino derivatives of mono- and dihalogenated anthraquinones, which are produced by halogenation of the mixture of anthraquinone disulphonic acids formed by the mercury-catalysed disulphonation of anthraquinone.

4. A process as claimed in claim 3, in which the majority of the 1,5-anthraquinone disulphonic acid has been separated from the mixture of anthraquinone disulphonic acids formed by the mercurycatalysed disulphonation of anthraquinone prior to halogenation.

5. A process as claimed in claim 3, in which the halogenation is carried out on the waste liquors arising after the separation of the majority of both the 1,5- and 1,8-anthraquinone disulphonic acids from the mixture of anthraquinone disulphonic acids formed by the mercury-catalysed disulphonation of anthraquinone.

6. A process as claimed in claim 2, in which the mixture compounds of formulae I and II is obtained by the reaction of the mixture of compounds of formula Ill with ammonia or amines of formulae NH2R1, wherein R' is as defined in claim 1 , followed by acylation.

7. A process as claimed in claim 2, in which the mixture of compounds of formulae I and II is obtained by reacting the mixture of compounds of formula Ill with amides of formula NH2-Y-R2, optionally followed by alkylation, R2 and Y having the meanings given in claim 1.

8. A process as claimed in any one of the preceding claims in which the organic solvent comprises an optionally substituted aliphatic, cycloaliphatic or aromatic hydrocarbon.

9. A process as claimed in claim 8, in which the solvent comprises toluene, chlorobenzene, odichlorobenzene, nitrobenzene, cyclohexane or n-hexane.

10. A process as claimed in any one of the preceding claims, in which the concentration of the liquor containing the mixture of compounds of formula I and II is adjusted to enable the former components to be efficiently separated by filtration.

11. A process as claimed in any one of the preceding claims, in which the separation is carried out at a temperature of from OOC to 300C.

12. A process as claimed in any one of the preceding claims, in which the group -Y-R2 in formulae I and II corresponds to the group -CO-C6H5 and in which nitrobenzene is used as the solvent.

1 3. A process as claimed in claim 1, substantially as hereinbefore described in any one of the foregoing Examples.

14. Compounds of the formula I as defined in claim 1, whenever separated by a process as claimed in any one of the preceding claims.

15. Compounds of the formula II as defined in claim 1, whenever separated by a process as claimed in any one of claims 1 to 11.