Field of the Present Invention:
The present invention is related to a process for preparing Catechol and Hydroquinone by hydroxylation of Phenol and more particularly, to a process for preparing Catechol and Hydroquinone such that production of Para-Benzoquinone is minimized.
Background of the Invention
Catechol and Hydroquinone are two important Chemicals having several applications. Catechol is used in the synthesis of pesticide, medicine, perfume, rubber, dyes, photosensitive materials, etc. Hydroquinone is mainly used to synthesize photosensitive materials, additives, anthraquinone dyes and other dyes. It is also used in composition material processing using a polymerization inhibitor, antioxidant, etc.
Many processes are known in the prior art for the conversion of Phenol to Hydroquinone and Catechol using Hydrogen Peroxide as an Oxidant.
U.S. Patent No. 5,493,061 discloses that Phenol and H202 in a molar ratio equal to or lower than 5, are contacted at 60 - 150 degrees Celsius with a Titanium Silicate molecular sieve containing Titanium in a proportion, (calculated as Ti02) of between 0.1 and 7% by weight and preferably between 2 and 4% wt. to yield the products Hydroquinone and Catechol. Heavy oxidation products, usually denoted, as tar, are formed in the said process. The invention in the said Patent requires higher concentration of Hydrogen Peroxide if water is used as a solvent and that has a risk of explosion.
U.S. Patent No. 3,920,756 describes use of Iron, Copper, Chromium and Cobalt chelate as catalyst in the Hydroxylation of Phenol. The invention disclosed in the said Patent has low reaction efficiency if water is used as a solvent.
The prior art available is practically silent on the quantity of Para-Benzoquinone formed in the reaction irrespective of the catalyst used in the reaction. Para-Benzoquinone is one of the major causes for the formation of heavy oxidation products, usually referred to as tar.
An ideal process would be such where a favorable Catechol and Hydroquinone ratio is obtained with minimum byproducts like Para-Benzoquinone under mild reaction conditions, low concentration of Hydrogen Peroxide and an easy-to-
prepare Catalyst.

Summary of the Invention
An object of the present invention is to minimize production of Para-Benzoquinone.
Another object of the present invention is to allow use of Catechol-Iron Complex Catalyst that is easier to prepare than TS-1 Catalyst.
Yet another object of the present invention is to use low concentration Hydrogen Peroxide in mild reaction conditions.
The process in accordance with the present invention is for preparing 11-21% Catechol, 5-19% Hydroquinone and 1-18% Para-Benzoquinone. In a Stirrer-equipped Reactor maintained at 28-32 degrees Celsius temperature, Catechol-Iron Complex Catalyst is prepared in presence of water by reacting Catechol with Iron Sulphate Heptahydrate. Weight of the water is twice that of the Phenol to be added. Catechol-Iron Complex Catalyst prepared is 1-6% of the total weight of Phenol to be added. pH is maintained from 2 to 6. Thereafter, Phenol is added at once while maintaining the said Reactor at 20-45 degrees Celsius temperature. 30% Hydrogen Peroxide is continuously added over 20 hours to carry out hydroxylation reaction while maintaining the pH from 2 to 6. pH is maintained by adding dilute Sulphuric Acid or Ammonia Solution. Molar ratio of Phenol and Hydrogen Peroxide is 1:1 to 1:4. Reactor contents are stirred continuously for an hour and the water in the Reactor is used as Solvent. Unreacted Phenol is recovered using Steam Distillation.
Description of the Present Invention
The process in accordance with the present invention uses a Reactor having a Stirrer. The said Reactor is kept at a temperature from 28 to 32 degrees Celsius.
The process begins by preparing Catechol-Iron Complex Catalyst in presence of water by reacting Catechol with Iron Sulphate Heptahydrate. Weight of the water is twice that of the Phenol to be added. Catechol-Iron Complex Catalyst prepared is 1-6% of the total weight of Phenol to be added. Catechol-Iron Complex Catalyst prepared is 1-6% of the total weight of Phenol to be added.
pH is maintained from 2 to 6 by adding dilute Sulphuric Acid or Ammonia Solution.
Thereafter, Phenol is added at once while maintaining the said Reactor at 20-45 degrees Celsius temperature. Phenol to be added may be in the state of solid,
liquid or an aqueous solution.

In the next step, Mild concentration Hydrogen Peroxide at 30% is continuously added over 20 hours to carry out hydroxylation reaction while maintaining the pH from 2 to 6.
Molar ratio of Phenol and Hydrogen Peroxide is 1:1 to 1:4.
Reactor contents are stirred continuously for an hour and the water in the Reactor is used as Solvent.
After completion of the reaction, 11-21% Catechol, 5-19% Hydroquinone and 1-18% Para-Benzoquinone is formed in the said Reactor.
Unreacted Phenol is recovered using Steam Distillation.
The advantages of the process of the present invention are as follows:
1. Catechol and Hydroquinone can be produced in good ratio with minimization of Para-Benzoquinone formed as a by-product.
2. The Hydroxylation conditions, pH and temperature and amount of the Catechol - Iron complex used can be selected over a range described. All of them have effect on the ratio of Catechol - Hydroquinone formed in the reaction.
3. The process gives flexibility to use dilute aqueous Hydrogen Peroxide solution.
4. The reaction temperatures are low and without pressure.
5. The resultant Catechol and Hydroquinone can be easily isolated from the reaction admixture, because the Hydroxylation is carried out in an aqueous medium and therefore, the products can be separated using distillation and conventional separation methods.
Best Method of performing the Invention
In the Best Method of performing the Invention, 21% Catechol, 14% Hydroquinone and 1% Para-Benzoquinone can be obtained. Inside a Reactor equipped with a stirrer a temperature from 28 to 32 degrees Celsius is to be maintained. In the said Reactor, an aqueous solution of Catechol-Iron Complex Catalyst can be prepared by reacting 0.24 g (0.00086 mole) of Iron Sulphate Heptahydrate with 0.46 g (0.0042 mole) of Catechol in 100 ml of water with adjusting the pH to 6 by adding small amount of dilute Ammonia solution at 300C and the same pH needs to be maintained throughout the reaction. Thereafter, at once, 47 gm (0.5 mole) of Phenol is added to the said aqueous solution of the Catechol-Iron Complex Catalyst. Temperature of the said Reactor is maintained from 20 to 45 degrees Celsius . Thereafter, Hydroxylation Reaction is to be

carried out by adding 56.66 gm (0.5 mole) of an aqueous solution containing 30% Hydrogen Peroxide continuously over a period of 20 hours while stirring and thereafter, the reaction mixture is to be further stirred for 1 hr. The water in the said Reactor is to be used as solvent. Thereafter, the unreacted Phenol from the Reaction Admixture is recovered using Steam Distillation.
The present invention will be illustrated in detail by the following examples:
Example- 1
An aqueous solution of a Catechol-Iron Complex was prepared by reacting 0.24 g (0.00086 mole) of Iron Sulphate Heptahydrate with 0.46 g (0.0042 mole )of Catechol in 100 ml of water with the adjustment of pH to 5 by adding small amount of dilute Ammonia solution at 30 degrees Celsius and the same pH was maintained throughout the reaction. To the aqueous solution of a Catechol-Iron Complex thus prepared was added 47 gm (0.5 mole) of Phenol. 56.66 gm (0.5 mole) of an aqueous solution containing 30 % Hydrogen Peroxide was continuously added over a period of 20 hrs, while stirring and thereafter, the reaction mixture was further stirred for 1 hrs. The reaction resulted into the formation of 18 % Catechol, 15 % Hydroquinone and 2 % Para- Benzoquinone in the reaction mixture. The unreacted Phenol was recovered by steam distillation.
Example- 2
An aqueous solution of a Catechol-Iron Complex was prepared by reacting 0.24 g (0.00086 mole) of Iron Sulphate Heptahydrate with 0.46 g (0.0042 mole )of Catechol in 100 ml of water with the adjustment of pH to 4 by adding small amount of dilute sulphuric acid solution at 30 degrees Celsius and the same pH was maintained throughout the reaction. To the aqueous solution of a Catechol-Iron Complex thus prepared was added 47 gm (0.5 mole) of Phenol. 56.66 gm (0.5 mole) of an aqueous solution containing 30 % Hydrogen Peroxide was continuously added over a period of 20 hrs, while stirring and thereafter, the reaction mixture was further stirred for 1 hrs. The reaction resulted into the formation of 16 % Catechol, 12 % Hydroquinone and 5 % Para- Benzoquinone in the reaction mixture. The unreacted Phenol was recovered by steam distillation.
Example- 3
An aqueous solution of a Catechol-Iron Complex was prepared by reacting 0.24 g (0.00086 mole) of Iron Sulphate Heptahydrate with 0.46 g (0.0042 mole )of Catechol in 100 ml of water with the adjustment of pH to 2 by adding small amount of dilute sulphuric acid solution at 30 degrees Celsius and the same pH was maintained throughout the reaction. To the aqueous solution of a Catechol-

Iron Complex thus prepared was added 47 gm (0.5 mole) of Phenol. 56.66 gm (0.5 mole) of an aqueous solution containing 30 % Hydrogen Peroxide was continuously added over a period of 20 hrs, while stirring and thereafter, the reaction mixture was further stirred for 1 hrs. The reaction resulted into the formation of 14 % Catechol, 14 % Hydroquinone and 6 % Para- Benzoquinone in the reaction mixture. The unreacted Phenol was recovered by steam distillation.
Example- 4
An aqueous solution of a Catechol-Iron Complex was prepared by reacting 0.24 g (0.00086 mole) of Iron Sulphate Heptahydrate with 0.46 g (0.0042 mole )of Catechol in 100 ml of water with the adjustment of pH to 6 by adding small amount of dilute Ammonia solution at 30 degrees Celsius and the same pH was maintained throughout the reaction. To the aqueous solution of a Catechol-Iron Complex thus prepared was added 47 gm (0.5 mole) of Phenol. 87.96 gm (0.776 mole) of an aqueous solution containing 30 % Hydrogen Peroxide was continuously added over a period of 20 hrs, while stirring and thereafter, the reaction mixture was further stirred for 1 hrs. The reaction resulted into the formation of 18 % Catechol, 19 % Hydroquinone and 2 % Para- Benzoquinone in the reaction mixture. The unreacted Phenol was recovered by steam distillation.
Example- 5
An aqueous solution of a Catechol-Iron Complex was prepared by reacting 0.24 g (0.00086 mole) of Iron Sulphate Heptahydrate with 0.46 g (0.0042 mole )of Catechol in 100 ml of water with the adjustment of pH to 6 by adding small amount of dilute Ammonia solution at 30 degrees Celsius and the same pH was maintained throughout the reaction. To the aqueous solution of a Catechol-Iron Complex thus prepared was added 47 gm (0.5 mole) of Phenol. 117.28 gm (1 mole) of an aqueous solution containing 30 % Hydrogen Peroxide was continuously added over a period of 20 hrs, while stirring and thereafter, the reaction mixture was further stirred for 1 hrs. The reaction resulted into the formation of 17 % Catechol, 17 % Hydroquinone and 5 % Para- Benzoquinone in the reaction mixture. The unreacted Phenol was recovered by steam distillation.
Example- 6
An aqueous solution of a Catechol-Iron Complex was prepared by reacting 0.24 g (0.00086 mole) of Iron Sulphate Heptahydrate with 0.46 g (0.0042 mole )of Catechol in 100 ml of water with the adjustment of pH to 6 by adding small amount of dilute Ammonia solution at 30 degrees Celsius and the same pH was maintained throughout the reaction. To the aqueous solution of a Catechol-Iron

Complex thus prepared was added 47 gm (0.5 mole) of Phenol. 234.56 gm (2 mole) of an aqueous solution containing 30 % of Hydrogen Peroxide was continuously added over a period of 20 hrs, while stirring and thereafter, the reaction mixture was further stirred for 1 hrs. The reaction resulted into the formation of 10.5 % Catechol, 5 % Hydroquinone and 17.5 % Para-Benzoquinone in the reaction. The unreacted Phenol was recovered by steam distillation.
Example- 7
An aqueous solution of a Catechol-Iron Complex was prepared by reacting 0.56 g (0.002 mole) of Iron Sulphate Heptahydrate with 1.128 g (0.01 mole )of Catechol in 100 ml of water with the adjustment of pH to 6 by adding small amount of dilute Ammonia solution at 30 degrees Celsius and the same pH was maintained throughout the reaction. To the aqueous solution of a Catechol-Iron Complex thus prepared was added 47 gm (0.5 mole) of Phenol. 56.66 gm (0.5 mole) of an aqueous solution containing 30 % Hydrogen Peroxide was continuously added over a period of 20 hrs, while stirring and thereafter, the reaction mixture was further stirred for 1 hrs. The reaction resulted into the formation of 18.5 % Catechol, 15.5 % Hydroquinone and 3.5 % Para- Benzoquinone in the reaction mixture. The unreacted Phenol was recovered by steam distillation.
Example- 8
An aqueous solution of a Catechol-Iron Complex was prepared by reacting 0.84 g (0.003 mole) of Iron Sulphate Heptahydrate with 1.692 g (0.015 mole )of Catechol in 100 ml of water with the adjustment of pH to 6 by adding small amount of dilute Ammonia solution at 30 degrees Celsius and the same pH was maintained throughout the reaction. To the aqueous solution of a Catechol-Iron Complex thus prepared was added 47 gm (0.5 mole) of Phenol. 56.66 gm (0.5 mole) of an aqueous solution containing 30 % Hydrogen Peroxide was continuously added over a period of 20 hrs, while stirring and thereafter, the reaction mixture was further stirred for 1 hrs. The reaction resulted into the formation of 18.5 % Catechol, 13.5 % Hydroquinone and 8 % Para-Benzoquinone in the reaction mixture. The unreacted Phenol was recovered by steam distillation.
Example- 9
An aqueous solution of a Catechol-Iron Complex was prepared by reacting 0.24 g (0.00086 mole) of Iron Sulphate Heptahydrate with 0.46 g (0.0042 mole )of Catechol in 100 ml of water with the adjustment of pH to 6 by adding small

amount of dilute Ammonia solution at 20 degrees Celsius and the same pH was maintained throughout the reaction. To the aqueous solution of a Catechol-Iron Complex thus prepared was added 47 gm (0.5 mole) of Phenol. 56.66 gm (0.5 mole) of an aqueous solution containing 30 % Hydrogen Peroxide was continuously added over a period of 20 hrs, while stirring and thereafter, the reaction mixture was further stirred for 1 hrs. The reaction resulted into the formation of 14 % Catechol, 10 % Hydroquinone and 1% Para- Benzoquinone in the reaction mixture. The unreacted Phenol was recovered by steam distillation.
Example- 10
An aqueous solution of a Catechol-Iron Complex was prepared by reacting 0.24 g (0.00086 mole) of Iron Sulphate Heptahydrate with 0.46 g (0.0042 mole )of Catechol in 100 ml of water with the adjustment of pH to 6 by adding small amount of dilute Ammonia solution at 45 degrees Celsius and the same pH was maintained throughout the reaction. To the aqueous solution of a Catechol-Iron Complex thus prepared was added 47 gm (0.5 mole) of Phenol. 56.66 gm (0.5 mole) of an aqueous solution containing 30 % Hydrogen Peroxide was continuously added over a period of 20 hrs, while stirring and thereafter, the reaction mixture was further stirred for 1 hrs. The reaction resulted into the formation of 12 % Catechol, 9 % Hydroquinone and 16 % Para- Benzoquinone in the reaction mixture. The unreacted Phenol was recovered by steam distillation.
The above examples are only provided to illustrate how the present invention works. The abovementioned examples should not be construed to limit the scope of the present invention. Without departing from the scope and spirit of the present invention as defined in the accompanying Claims, the abovementioned examples can be modified or altered as a person skilled in the art will readily understand.

Claims
We Claim:
1. A process for preparing Catechol and Hydroquinone comprising the
steps of
a. having a Reactor at a temperature from 28-32 degrees Celsius
equipped with a Stirrer;
b. preparing in the said Reactor, in presence of water, Catechol-Iron
Complex Catalyst by reacting Catechol with Iron Sulphate
Heptahydrate while maintaining pH from 2 to 6;
c. adding Phenol at once in the said Reactor;
d. maintaining the temperature of the said Reactor from 20 degrees
Celsius to 45 degrees Celsius;
e. carrying out hydroxylation reaction by adding 30 % Hydrogen
Peroxide in the said Reactor continuously over a period of twenty
hours while maintaining the said pH range;
f. continuing stirring of the contents of the said Reactor for an hour;
g. using the water in the said Reactor as a solvent;
h. forming in the said Reactor after completion of reaction, Catechol 11-21 %, Hydroquinone 5-19 %, and Para-Benzoquinone 1 - 18 %;
i. recovering the unreacted Phenol from the reaction admixture using Steam Distillation;
2. A method according to claim-1, wherein the weight of the water in presence of which the Catechol-Iron Complex Catalyst is prepared is twice that of the Phenol to be added.
3. A method according to claim-1, wherein the Catechol-Iron Complex Catalyst prepared is 1 - 6 % of the weight of the Phenol to be added.
4. A method according to claim-1, wherein said the Phenol and Hydrogen Peroxide molar ratio is 1:1 — 1:4.
5. A method according to claim-1, wherein maintenance of pH is done by adding dilute Sulphuric Acid or Ammonia Solution.