CLIAMS:We Claim:

1. A process for preparing substituted alkyl phenols, the process comprising:

a first stage of treating substituted amino compound with an acid to form an amine salt;

a second stage of treating the amine salt with a diazotizing agent to form a diazonium salt;

a third stage of hydrolyzing the diazonium salt with a solvent and an acid to obtain an effluent phase and an organic phase comprising substituted alkyl phenol; and

recycling the effluent phase to all or any of the first, second or third stage.

2. The process as claimed in claim 1 comprising recovering substituted alkyl phenol from the organic phase by rectification.

3. The process as claimed in claim 1 comprising recycling the effluent phase to the first and third stage.

4. The process as claimed in any of the preceding claims 1-3, wherein the effluent phase includes acid and water and is recycled infinite times without any pretreatment.

5. The process as claimed in claim 1 comprising treating substituted amino compound with an acid at a temperature in a range of 40 to 60°C.

6. The process as claimed in claim 1 comprising treating the amine salt with a diazotizing agent at a temperature in a range of 0° to 5°C.

7. The process as claimed in claim 1 comprising hydrolyzing the diazonium salt with the solvent at a temperature in the range of 70° to 105° C.

8. The process as claimed in claim 1 comprising the substituted amino compound and acid in a ratio of 1:1.5 to 1:5.

9. The process as claimed in claim 1, wherein the concentration of the acid is in a range of 10% to 40%.

10. The process as claimed in claim 1, wherein the substituted amino compound is selected from the group comprising of alkyl substituted aniline, halo substituted aniline, naphthylamines.

11. The process as claimed in claim 1, wherein the acid is selected from sulfuric acid, hydrochloric acid , sulfuric acid and phosphoric acid or mixtures thereof.

12. The process as claimed in claim 1, wherein the diazotizing agent is selected from nitrogen oxide component, Sodium Nitrite and HCl , sodium Nitrite and sulfuric acid , sodium nitrite and mixture of sulfuric acid and phosphoric acid , Nitrosyl sulfuric acid and sulfuric acid , Nitrosyl sulfuric acid and Acetic acid , Nitrosyl chloride .

13. The process as claimed in claim 12, wherein the nitrogen oxide component is a mixture of nitric oxide and nitrogen dioxide.

14. The process as claimed in claim 1, wherein the solvent is nonpolar and nonprotic.

15. The process as claimed in claim 13, wherein the solvent is selected from toluene, benzene, chlorobenzene, xylene, cumene.

16. A method for reducing the chemical components used in a process for preparing substituted alkyl phenols, the method comprising:

recycling an effluent phase obtained in the process to various steps of the process for preparing substituted alkyl phenols.

17. The method as claimed in claim 10, wherein the various steps includes a salt formation, diazotization and hydrolysis.

18. The method as claimed in claim 11, wherein the salt formation step comprises of treating a substituted amino compound with an acid to form an amine salt.

19. The method as claimed in claim 11, wherein the diazotization step comprises of treating an amine salt with a diazotizing agent to form a diazonium salt.

20. The method as claimed in claim 11, wherein the hydrolysis step comprises of treating a diazonium salt with a solvent and an acid to obtain an effluent phase and an organic phase comprising substituted alkyl phenol.

21. The method as claimed in claim 10 or 11, wherein the effluent phase is generated during hydrolysis.

22. The method as claimed in any of the preceding claims 16-22, wherein the effluent phase includes acid and water and is recycled infinite times without any pretreatment.
,TagSPECI:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)

&

THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
[See section 10, Rule 13]

A PROCESS FOR PREPARING SUBSTITUTED ALKYL PHENOLS;

DEEPAK NITRITE LIMITED, WHOSE ADDRESS IS 9/10, KUNJ SOCIETY, R C DUTT ROAD, ALKAPURI, VADODARA, GUJARAT -390005, INDIA

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

FIELD OF THE INVENTION

The present invention relates to a process for preparing substituted alkyl phenols, particularly to a method for reducing the use of chemical components in the process for preparing substituted alkyl phenols.

BACKGROUND OF THE INVENTION
Substituted alkyl phenols are important intermediate products for the production of agrochemical, dyes and medicines. In particular, all hydroxy-xylenes are useful precursors to agrochemical, medicine, and dyes.

JP51095030 discloses method of preparation of phenol wherein aniline is mixed with an organic solvent which is insoluble or sparingly soluble in water (such as the one selected from the solvents like ketones or esters), which is followed by mixing it with water and an acid (sulfuric acid or hydrochloric acid) and then adding a nitrite salt, under heating condition. However disadvantage of said patent is use of solvents such as isobutyl acetate, methyl ethyl ketone, methyl isobutyl ketone, which are partially soluble in water and cause a problem during effluent treatment. Also the use of said solvents having property of entrainment with substituted phenols during final distillation cause to get impure product. Also hydrolysis of said solvents is possible during diazotization.

CA1128932 discloses a method for the preparation of aryldiazonium salts in aqueous solutions by reacting nitrous vapors of an aqueous solution of the aromatic amine salt. The method of the invention is characterized in that the nitrous vapors contain NO, NO2 and N2O3 such that at equilibrium the molar ratio NO/NO2 is between 2 and 100, in the gas mixture.

US2403748 discloses a process for manufacturing 2,6-di-halo phenols, the process comprising halogenating a 4-tertiary alkyl phenol to form the corresponding 2,6-dihalo, 4-tertiary alkyl phenol, and thereafter catalytically dealkylating the resulting 2,6- di-halo, 4-tertiary alkyl phenol in the presence of an alkyl acceptor.

Various known processes for production of phenols from aniline and its alkali derivatives were found to produce heavy foam during the reaction. Also, during the passing of solid diazonium salt from one reactor to another reactor, the diazonium salt decomposes quickly causing inconvenience and safety concerns. This traditional route suffers from the disadvantages of high capital, utility cost and safety issues.

Traditionally, the known processes have been found to be very unsatisfactory with respect to effluent treatment. Therefore, there is a need for a process which provides for the reuse of the effluent.

SUMMARY OF THE INVENTION
An aspect of the present invention relates to a process for preparing substituted alkyl phenol. The process comprises of a first stage of treating a substituted amino compound with an acid to form an amine salt. The second stage comprises of treating the amine salt with a diazotizing agent to form a diazonium salt. The third stage comprises of hydrolyzing the diazonium salt with a solvent and an acid to obtain an effluent phase and an organic phase comprising substituted alkyl phenol.

Another aspect of the present invention relates to a method for reducing the chemical components used in a process for preparing substituted alkyl phenols. The method comprises of recycling an effluent phase obtained in the process to various steps of the process for preparing substituted alkyl phenols.

The effluent phase is recycled infinite times to various stages without any pretreatment.

DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention relates to a process for preparing substituted alkyl phenols. The process comprises of a first stage of treating a substituted amino compound with an acid to form an amine salt. The second stage comprises of treating the amine salt obtained in the first stage with a diazotizing agent to form a diazonium salt. The third stage comprises of hydrolyzing the diazonium salt with a solvent and an acid to obtain an effluent phase and an organic phase, which comprises of substituted alkyl phenol. The effluent phase obtained in the third stage is recycled to all or any of the first, second or third stage.

In one embodiment of the present invention, the substituted alkyl phenol present in the organic phase is recovered by rectification.

In a preferred embodiment of the present invention, the effluent phase is recycled to the first and third stage.

The effluent phase is recycled to the same batch or to another batch.

The effluent phase includes acid and water. It is recycled any number of times to the various stages or steps of the process. The effluent phase is recycled without any pretreatment.

The substituted amino compound is treated with the acid at a temperature in the range of 40° to 60° C. The substituted amino compound and acid is present in a ratio of 1:1.5 to 1:5. The concentration of the acid is from 10% to 40 %. The substituted amino compound is selected from alkyl substituted aniline, halo substituted aniline, naphthylamines. The preferred amino compound is xylidine. The acid is selected from sulfuric acid, hydrochloric acid, mixture of sulfuric acid and phosphoric acid, preferably sulfuric acid.

The amine salt formed in the first stage is treated with a diazotizing agent at a temperature in the range of 0° to 5° C.

The diazotizing agent is selected from nitrogen oxide component, sodium nitrite and HCl, sodium nitrite and sulfuric acid, sodium nitrite and sulfuric acid and phosphoric acid, nitrosyl sulfuric acid and sulfuric acid, nitrosyl sulfuric acid and acetic acid, nitrosyl chloride, preferably nitrogen oxide component. The nitrogen oxide component is an equimolar mixture of nitric oxide and nitrogen dioxide.

The diazonium salt formed in the second stage is treated with the solvent and acid at a temperature in the range of 70° to 105° C.

The solvent is non polar and non protic and is selected from toluene, benzene, chlorobenzene, xylene, cumene, preferably toluene. The acid is selected from sulfuric acid, hydrochloric acid, mixture of sulfuric acid and phosphoric acid, preferably sulfuric acid.

Another embodiment of the present invention relates to a method for reducing the chemical components used in a process for preparing substituted alkyl phenols. The method comprises of recycling an effluent phase obtained in the process to various steps of the process for preparing substituted alkyl phenols.

The various steps involved in the process for preparing substituted alkyl phenols include salt formation, diazotization and hydrolysis.

The first step of salt formation comprises of treating a substituted amino compound with an acid to form an amine salt. The substituted amino compound is selected from alkyl substituted aniline, halo substituted aniline, naphthylamines. The preferred amino compound is xylidine. The acid is present in a concentration of 10% to 40% and is selected from sulfuric acid, hydrochloric acid, mixture of sulfuric acid and phosphoric acid, preferably sulfuric acid. Substituted amino compound and acid are present in a ratio of 1:1.5 to 1:5. The temperature is maintained in a range of 40° to 60°C.

The second step of diazotization comprises of treating the amine salt with a diazotizing agent at a temperature in the range of 0° to 5° C to form a diazonium salt. The diazotizing agent is selected from nitrogen oxide component, sodium nitrite and HCl, sodium nitrite and sulfuric acid, sodium nitrite and mixture of sulfuric acid and phosphoric acid, nitrosyl sulfuric acid and sulfuric acid, nitrosyl sulfuric acid and acetic acid, nitrosyl chloride. Preferably, nitrogen oxide component is used. The nitrogen oxide component is an equimolar mixture of nitric oxide and nitrogen dioxide.

The third step of hydrolysis comprises of hydrolyzing the diazonium salt in the presence of a solvent and an acid to obtain an effluent phase and an organic phase comprising substituted alkyl phenol. Hydrolysis is carried out at a temperature in the range of 70° to 105°C.

The solvent is non polar and non protic and is selected from toluene, benzene, chlorobenzene, xylene, cumene, preferably toluene. The acid is selected from sulfuric acid, hydrochloric acid, mixture of sulfuric acid and phosphoric acid, preferably sulfuric acid.

The effluent phase generated during hydrolysis includes acid and water and is recycled infinite times to various steps. Preferably, the effluent phase is recycled back to the first step of salt formation and the third step of hydrolysis. The effluent phase does not need any pretreatment prior to recycling.

The substituted alkyl phenol present in the organic phase can be recovered by rectification.

The effluent phase including acid and water is recycled to the various steps of the process. Recycling of the effluent phase obviates the risk of handling the acid, which is hazardous. The acid generated in the effluent phase which otherwise would be a waste is utilized in the reactions thereby reducing acid consumption significantly. Also, the side reactions in the diazotization step are suppressed by this process. The effluent phase does not require any pretreatment and is recycled back to various steps such as salt formation, diazotization and hydrolysis. Preferably, the effluent phase is recycled to the salt formation and hydrolysis steps. Due to recycling of the effluent phase, additional feeding of acid and water in the process is not required. The continuous recycling of the effluent phase to various steps help sustain the reaction.

The following examples illustrates the invention, but is not limiting thereof.
Example 1:
A. Salt formation
To a round bottom flask with scrubber system, 1015 g of 35% aqueous solution of sulfuric acid was charged. 121 g of 2,4-xylidine was added slowly into the flask at 60°C under stirring to obtain aqueous solution of 2,4-xylidine sulfate.

B. Diazotization
Nitrogen oxide component (NO 200ml/min and NO2 600ml/min) was passed into chilled aqueous solution of 2,4-xylidine sulfate at a temperature of 2°C to form diazonium salt solution. The solution was tested with starch potassium iodide paper. The reaction was stopped when the color of the paper changed to blue. Simultaneously 5 gm of sulfamic acid was added to eliminate excess of nitric oxide component.

C. Hydrolysis
353 g of 35% aqueous solution of sulfuric acid and 453 g of toluene was added to another round bottom flask and heated to 80°C. The diazonium salt solution as prepared above was added slowly to the round bottom flask within 2 hours at 80°C under stirring. The temperature was maintained at 80°c for 30 minutes after complete addition of diazonium salt solution to obtain an organic phase comprising 2, 4 xylenol and an effluent phase comprising of sulfuric acid and toluene. The reaction mixture was cooled to 35°C. The organic phase was separated from the effluent phase. The effluent layer was recycled back to the salt formation and hydrolysis step. The organic phase was distilled and toluene was recovered which was recycled to the hydrolysis step.107 g of 2,4-Xylenol of 99.5% purity was obtained, Yield was 87.5%.

Example 2:
The effluent phase separated in example 1 was charged into a 5 litre Round Bottom Flask to which 2,4-xylidine (121g ) was added and the further steps of diazotization and hydrolysis as described in example 1 was carried out.
Example: 3

A. Salt formation
To a round bottom flask with scrubber system, 1015 g of 35% aqueous solution of sulfuric acid was charged. 121 g of 2,5-xylidine was added slowly into the flask at 60°c under stirring to obtain aqueous solution of 2,5-xylidine sulfate.

B. Diazotization
Nitrogen oxide component (NO 200ml/min and NO2 600ml/min) was passed into chilled aqueous solution of 2,5-xylidine sulfate at a temperature of 2°C to form diazonium salt solution. The solution was tested with starch potassium iodide paper. The reaction was stopped when the color of the paper changed to blue. Simultaneously 5 gm of sulfamic acid was added to eliminate excess of nitric oxide component.

C. Hydrolysis
353 g of 35% aqueous solution of sulfuric acid and 453 g of toluene was added to another round bottom flask and heated to 80°C. The diazonium salt solution as prepared above was added slowly to the round bottom flask within 2 hours at 80°C under stirring. The temperature was maintained at 80°c for 30 minutes after complete addition of diazonium salt solution to obtain an organic phase comprising 2, 5 xylenol and an effluent phase comprising of sulfuric acid and toluene. The reaction mixture was cooled to 35°C The organic phase was separated from the effluent phase. The effluent layer was recycled back to the salt formation and hydrolysis step. The organic phase was distilled and toluene was recovered which was recycled to the hydrolysis step. 107 g of 2,5-xylenol of 99.5% purity was obtained, Yield was 87.5%.
Example 4:
The effluent phase separated in example 3 was charged into a 5 litre Round Bottom Flask to which 2,5-xylidine (121g ) was added and the further steps of diazotization and hydrolysis as described in example 3 was carried out.

Example: 5
A. Salt formation
To a round bottom flask with scrubber system, 1015 g of 35% aqueous solution of sulfuric acid was charged. 121 g of 2,3-xylidine was added slowly into the flask at 60 °c under stirring to obtain aqueous solution of 2,3-xylidine sulfate.

B. Diazotization
Nitrogen oxide component (NO 200ml/min and NO2 600ml/min) was passed into chilled aqueous solution of 2,3-xylidine sulfate at a temperature of 2°C to form diazonium salt solution. The solution was tested with starch potassium iodide paper. The reaction was stopped when the color of the paper changed to blue. Simultaneously 5 gm of sulfamic acid was added to eliminate excess of nitric oxide component.

C. Hydrolysis
353 g of 35% aqueous solution of sulfuric acid and 453 g of toluene was added to another round bottom flask and heated to 80°C. The diazonium salt solution as prepared above was added slowly to the round bottom flask within 2 hours at 80°C under stirring. The temperature was maintained at 80°c for 30 minutes after complete addition of diazonium salt solution to obtain an organic phase comprising 2,3 xylenol and an effluent phase comprising of sulfuric acid and toluene. The reaction mixture was cooled 35°C. The organic phase was separated from the effluent phase. The effluent layer was recycled back to the salt formation and hydrolysis step. The organic phase was distilled and toluene was recovered which was recycled to the hydrolysis step. 99 g of 2,3-xylenol of 99.5% purity was obtained, Yield was 81.1%.

Example 6:
The effluent phase separated in example 5 was charged into a 5 litre Round Bottom Flask to which 2,3-xylidine (121g ) was added and the further steps of diazotization and hydrolysis as described in example 5 was carried out.

Example: 7
A. Salt formation
To a round bottom flask with scrubber system, 1351 g of 35% aqueous solution of sulfuric acid was charged. 161 g of 3-Amino Benzotrifluoride was added slowly into the flask at 60 °c under stirring to obtain aqueous solution of 3-Amino Benzotrifluoride sulfate.

B. Diazotization
Nitrogen oxide component (NO 350ml/min and NO2 535 ml/min) was passed into chilled aqueous solution of 3-Amino Benzotrifluoride sulfate at a temperature of 2°C to form diazonium salt solution. The solution was tested with starch potassium iodide paper. The reaction was stopped when the color of the paper changed to blue. Simultaneously 8 gm of sulfamic acid was added to eliminate excess of nitric oxide component.

C. Hydrolysis
470 g of 35% aqueous solution of sulfuric acid and 603 g of toluene was added to another round bottom flask and heated to 80°C. The diazonium salt solution as prepared above was added slowly to the round bottom flask within 2 hours at 80°C under stirring. The temperature was maintained at 80°c for 30 minutes after complete addition of diazonium salt solution to obtain an organic phase comprising 3-Hydroxy benzotrifluoride and an effluent phase comprising of sulfuric acid and toluene. The reaction mixture was cooled to 35°C. The organic phase was separated from the effluent phase. The effluent layer was recycled back to the salt formation and hydrolysis step. The organic phase was distilled and toluene was recovered which was recycled to the hydrolysis step. 148 g of 3-Hydroxy benzotrifluoride of 99% purity was obtained, Yield was 91.1%.

Example 8 :
The effluent phase separated in example 7 was charged into a 5 litre Round Bottom Flask to which 3-Amino Benzotrifluoride (161g) was added and the further steps of diazotization and hydrolysis as described in example 7 was carried out.