Claims:1. A process for preparing of 9,10-anthraquinone and its derivatives, said process comprising the following steps:
i. reacting benzene or substituted benzene with phthalic anhydride at a predetermined temperature in the presence of an ionic liquid, and optionally an alkali or alkaline earth metal halide salt for a predetermined time period to obtain a mixture comprising 9,10-anthraquinone or its derivatives; and
ii. cooling and separating said 9,10-anthraquinone or its derivatives from said mixture.
2. The process as claimed in claim 1, wherein said ionic liquid comprises Lewis acid, Lewis base and/ or a fluid medium.
3. The process as claimed in claim 1 or 2, wherein said Lewis acid is at least one selected from the group consisting of AlCl3, GaCl3, InCl3 FeCl3, SnCl4 and TiCl4.
4. The process as claimed in claim 1, wherein said Lewis base is at least one selected from the group consisting of urea, N-Methyl-2-pyrrolidone, acetamide, triphenylphosphine, tributylphosphine and heterocylic amines.

5. The process as claimed in claim 1, wherein said alkali or alkaline earth metal halide salt is at least one selected from the group consisting of NaCl, KCl, NaBr, MgCl2, LiCl and KBr.
6. The process as claimed in claim 1, wherein the molar ratio of phthalic anhydride and said Lewis acid is in the range of 1:0.1 to 1:2.
7. The process as claimed in claim 1, wherein the molar ratio of phthalic anhydride and said alkali or alkaline earth metal halide salt is in the range of 1:0.1 to 1:2.
8. The process as claimed in claim 1, wherein the benzene derivative is at least one selected from the group consisting of toluene, xylene, chlorobenzene, bromobenzene, methoxy benzene, substituted methoxy benzene, substituted chlorobenzene, and substituted bromobenzene.
9. The process as claimed in claim 1, wherein said predetermined temperature is in the range of 80 to 200 °C.
10. The process as claimed in claim 1, wherein the predetermined time period is in the range of 30 min to 300 min. , Description:FIELD
The present disclosure relates to a process for the preparation of 9,10-anthraquinone.
BACKGROUND
Anthraquinone is a widely used chemical raw material in industries such as dyes, pharmaceuticals, pesticides and others. Anthracene is available in small quantities from coal tar and is used to make anthraquinone, but purification of the anthracene feed is difficult and expensive, so that, this process is undesirable. Another disadvantage of the process is that the supply of anthracene from coal tar is uncertain and it is expected in the future that its use as a source for anthraquinone will be significantly reduced.
In another method, phthalic anhydride and benzene are reacted in Friedel-Craft reaction using aluminum chloride in order to produce an intermediate compound, o-benzoyl benzoic acid, which is then converted by acid treatment to anthraquinone. The method consumes large quantities of aluminum chloride and has other disadvantages.
Further, the processes using large quantities of Lewis acids and mineral acids are not environment friendly. The use of the mineral acid is hazardous and the work-up of the related reaction becomes complex.
Therefore, there is felt a need to provide a process for the preparation of 9,10-anthraquinone and its derivatives, which is simple and economical.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to provide a process for the preparation of 9,10-anthraquinone.
Another object of the present disclosure is to provide a process for the preparation of derivatives of 9,10-anthraquinone.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure provides a process for preparing of 9,10-anthraquinone and its derivatives, the process comprising the following steps: i) reacting benzene or substituted benzene with phthalic anhydride at a predetermined temperature in the presence of an ionic liquid, and optionally an alkali or alkaline earth metal halide salt for a predetermined time period to form a mixture comprising 9,10-anthraquinone or its derivatives; and ii) cooling and separating 9,10-anthraquinone or its derivatives from the reaction mixture.
The process of the present disclosure is carried out in a single step. The ionic liquid of the present disclosure acts as a catalyst as well as medium for preparation of 9,10-anthraquinone. The alkali or alkaline earth metal salt is used as a co-catalyst that absorbs water formed during the process of the present disclosure, which drives the reaction forward towards completion.

DETAILED DESCRIPTION

Anthraquinone and its derivatives are widely used in the dye industry and find other applications in the manufacturing of hydrogen peroxide and in the paper pulp industry. Anthraquinone is produced industrially by several processes, principally by oxidizing anthracene or from the reaction of phthalic anhydride with benzene.
The present disclosure relates to a single step process for preparing 9,10-anthraquinone and its derivatives.
In accordance with one aspect of the present disclosure, there is provided a process for the synthesis of 9,10-anthraquinone and its derivatives. The process is accomplished by reacting benzene or substituted benzene with phthalic anhydride in the presence of an ionic liquid, and optionally an alkali or alkaline earth metal halide salt to form a mixture comprising 9,10-anthraquinone or its derivatives.
Benzene or substituted benzene is reacted with phthalic anhydride in an ionic liquid at a temperature in the range of 80 to 200 °C for a predetermined time period. The mixture is cooled and 9,10-anthraquinone or its derivatives are separated from the mixture.

Benzene or substituted benzene is acylated with phthalic anhydride in the presence of an ionic liquid. The ionic liquid acts as an acid catalyst to perform the acylation reaction, as well as the cyclization reaction to form anthraquinone.

During the above mentioned reactions, water is produced. The water, thus produced, can be absorbed by the alkali or alkaline earth metal salt, thereby driving the reaction forward towards completion.

Thus, the use of the alkali or alkaline earth metal salt during the process of the present disclosure, increases the yield of 9,10-anthraquinone or it’s derivative.

In accordance with one embodiment of the present disclosure, the ionic liquid of the present disclosure is used as a catalyst for preparation of 9,10-anthraquinone or its derivatives.

In accordance with another embodiment of the present disclosure, the ionic liquid is used as a medium for the preparation of 9,10-anthraquinone or its derivatives.

The use of the ionic liquid facilitates the single step reaction, which minimizes the use of reagents and the reaction time, thereby making the process of the present disclosure, economical.

The ionic liquid of the present disclosure comprises Lewis acid, Lewis base and/ or a fluid medium. Lewis acid of the present disclosure is at least one selected from the group consisting of AlCl3, GaCl3, InCl3 and FeCl3, SnCl4, TiCl4.

Lewis base of the present disclosure is at least one selected from the group consisting of urea, N-Methyl-2-pyrrolidone, acetamide, triphenylphosphine, tributylphosphine and heterocylic amines.

The alkali or alkaline earth metal halide salt acts as a co-catalyst during the process of the present disclosure. The alkali or alkaline earth metal halide salt of the present disclosure is at least one selected from the group consisting of NaCl, KCl, NaBr, MgCl2, LiCl, and KBr. The alkali or alkaline earth metal halide salt of the present disclosure absorbs water formed during the process of the present disclosure, thereby helps to produce 9,10-anthraquinone or its derivatives in a single step.
In accordance with the present disclosure, the molar ratio of phthalic anhydride and Lewis acid is in the range of 1:0.1 to 1:2.

In accordance with the present disclosure, the molar ratio of phthalic anhydride and said alkali or alkaline earth metal halide salt is in the range of 1:0.1 to 1:2.

The benzene derivative is at least one selected from the group consisting of toluene, xylene, chlorobenzene, bromobenzene, methoxy benzene, substituted methoxy benzene, substituted chlorobenzene and substituted bromobenzene.

The use of benzene derivatives as a reactant during the process of the present disclosure produces derivatives of 9,10-anthraquinone.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a process for the preparation of 9,10-anthraquinone, that is:
• simple,
• economical, and
• environment friendly.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.

While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.