Description:PROCESS FOR PREPARATION OF GUAIACOL AND P-METHOXYPHENOL
Field of the invention:
The present invention generally relates to preparation of guaiacol and p-methoxyphenol and more particularly it relates to separation of guaiacol and p-methoxyphenol from reaction mixture by semi continuous distillation.
Background of the invention:
Guaiacol (also known as o-methoxyphenaol or 2-hydroxy anisole) and p-methoxy phenol (also known as p-methoxyphenaol or 4-hydroxyanisole, or MEHQ or p-Guaiacol) are widely used methoxyphenol compounds in the field of medicinal organic, synthetic perfumes, anti-oxidants and polymerization inhibitors. There have been many references in the prior art for the manufacture of guaiacol, p-methoxy phenol and the mixtures of guaiacol and p-methoxy phenol. The prior art methods use expensive starting materials like catechol and hydroquinone. The methods involve multistep reactions involving expensive reagents and noble metal catalysts producing hazardous effluents as well as giving poor overall yields. US patent no. 5786519 discloses a process for preparation of a mixture of guaiacol and p-methoxy phenol, wherein anisole is reacted with hydrogen peroxide in the presence of a solid organotransition metal complex to form the mixture of guaiacol and p-methoxy phenol. Since the boiling point of compounds in the resulting reaction mixture are in close proximity, it is difficult to achieve the desired purity requirements. The prior art patents do not provide effective method of separation of guaiacol and p-methoxy phenol from mixture thereof. Batch distillation for separation of guaiacol and p-methoxy phenol is an energy intensive process with longer time cycle, resulting lower yield with higher tar formation. Due to these disadvantages, the process of preparation of guaiacol and p-methoxy phenol by reacting anisole with hydrogen peroxide is not commercialized.
Accordingly, there exists a need to provide a method of separation of guaiacol and p-methoxy phenol to yield high pure products, that can overcome the drawbacks in the prior art.
Objects of the invention:
An object of the present invention is to provide a cost effective method for separating guaiacol and p-methoxy phenol from the reaction mixture.
Another objective of the present invention is to provide a process for producing highly pure guaiacol and p-methoxy phenol.
Yet another objective of the present invention is to provide a process for recovering unreacted reactants and solvent for recycling them in the process for preparation of guaiacol and p-methoxy phenol.
Still another objective of the present invention is to provide a single step process with reusable catalyst and minimal effluents for
Summary of the invention
The present invention discloses a process for preparation of guaiacol and p-methoxyphenol, wherein anisole reacted with hydrogen peroxide in a ketone solvent in the presence of a catalyst. The components of reaction mixture containing anisole, ketone solvent and products - guaiacol and p-methoxyphenol are separated using a distillation method, which is a combination of batch and continuous modes. The distillation method comprises subjecting the reaction mixture to continuous distillation at atmospheric pressure to recover the ketone solvent giving a resulting mixture of anisole, p-methoxyphenol, guiacol and tar. In step II, the resulting mixture of anisole, p-methoxyphenol, guiacol and tar is again subjected to continuous distillation to partially recover anisole giving a resulting mixture of anisole, p-methoxyphenol, guiacol and tar. In step III, the resulting mixture of step II is subjected to batch distillation to recover fraction of anisole and distil out fraction A and fraction B, wherein fraction A and fraction B are mixtures of anisole, p-methoxyphenol, guiacol with specific weight ratios. In next steps, fraction A and fraction B are distilled separately by batch distillation method to recover high purity anisole, p-methoxyphenol and guiacol. The purity of anisole, p-methoxyphenol and guiacol recovered in the distillation ranges from 97% to 99.99%.
Brief description of the drawings:
The objectives and advantages of the present invention will become apparent when the disclosure is read in conjunction with the following figures, wherein
Figure 1 shows flow chart of a distillation method, in accordance with the present invention.
Detailed description of the embodiments:
The foregoing objectives of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiments.
The present invention provides a process for preparation as well as separation of guaiacol and p-methoxyphenol. The components of reaction mixture containing reactants, solvent and products are separated using distillation process. Distillation is a method of separating mixtures based on differences in volatility of components in a boiling liquid mixture. In the present process, distillation is carried out in continuous, batch and flash modes. In continuous distillation, the mixture is continuously fed into the process and separated fractions are removed continuously as output streams. The batch distillation refers to the distillation in batches, meaning that a mixture is distilled to separate the components in its entirety and subsequently charged again with more mixture; and the process is repeated. Although the batch distillation allows for a high level of chemical purity and maximum flexibility, the batch distillation process is highly energy intensive, requiring longer cycle time with more tar formation and lower yield. Flash distillation is a methodology to separate the high boiler/tar from volatiles in very short time frame without separating the components of volatiles. This is to avoid the decomposition of volatiles in the presence of tar. The present invention uses a semi continuous distillation method having combination of continuous and batch distillations. The semi-continuous distillation method of present invention provides 97 to 99% pure guaiacol and p-methoxyphenol with recovery of anisole and also the reaction solvent.
The process for preparation of guaiacol and p-methoxyphenol comprises: reacting anisole with hydrogen peroxide in a ketone solvent in the presence of a catalyst, wherein the weight proportion of anisole: hydrogen peroxide: solvent ranges from 62:3:25 to 70:7:35. In an embodiment, the ketone solvent is any one selected from acetone, 2-butanone, tert-butylmethylketone, 2-hexanone and methylphenyl ketone. In this process, a valuable byproduct guaiacol is formed along with p-methoxyphenol and excess anisole is left in the reaction mixture. After completion of the reaction, the reaction mixture contains the products: guaiacol and p-methoxyphenol, as well as the unreacted anisole and the solvent. The reaction mixture containing anisole, ketone solvent, guaiacol, p-methoxyphenol and tar in a weight ratio ranging from 62:25:0.5:0.2:0.1 to 70:35:4:3:1 is subjected to distillation for separation of components.
Referring to the figure 1 the method (100) (100) (hereinafter referred as “the method (100)”) for separation of guaiacol and p-methoxyphenol and recovery of unreacted reactants and solvent, in accordance with the present invention is shown. The method (100) is a combination of continuous and batch distillations
In step I, the method (100) includes subjecting the reaction mixture to continuous distillation at atmospheric pressure and with a feed rate in a range from 25 tons/h to 30 tons/h to distil out the ketone solvent giving a resulting mixture of anisole, p-methoxyphenol, guiacol and tar in weight ratio ranging from 93: 1: 0.3: 0.2 to 97: 5: 2: 0.5. The purity of ketone solvent recovered in step I ranges from 97% to 99.99%. The recovered solvent is recycled in the process of preparation of guaiacol and p-methoxyphenol.
In step II, the method (100) includes subjecting the resulting mixture of step I to continuous distillation at a temperature ranging from 132°C to 140°C, a pressure ranging from 530 - 560 mm Hg and with a feed rate from 17.5 ton/h to 22 ton/h, to partially distil out fraction of anisole, giving a resulting mixture of anisole, p-methoxyphenol, guiacol and tar in weight ratio ranging from 48: 29: 13: 1 to 52: 33: 17: 5. The purity of anisole recovered in step II ranges from 97% to 99.99%.
In step III, the method (100) includes subjecting the resulting mixture of step II to recover anisole at a temperature ranging from 92°C to 98°C and a pressure ranging from 600 to 640 mm Hg from batch distillation, followed by flash distillation to distil out a fraction A and a fraction B, wherein a portion of tar in p-methoxyphenol remains at a bottom. The portion of tar in p-methoxyphenol remaining in the distillation column is removed and p-methoxyphenol is recovered later separately.
Fraction A is recovered at a temperature ranging from 122°C to 126°C and at pressure ranging from 660 to 700 mm of Hg. Specifically, the fraction A is recovered at 124°C and 680 mm of Hg pressure. The fraction A contains anisole, guaiacol and p-methoxyphenol in a weight ratio ranging from 14: 78: 2 to 18: 82: 6.
The fraction B is recovered at a temperature ranging from130°C to 135°C and at a pressure ranging from 670 to 710 mm of Hg. More specifically, the fraction B is recovered at 132°C temperature and at 690 mm of Hg pressure. The fraction B contains anisole, guaiacol and p-methoxyphenol in a weight ratio ranging from 0.1: 6: 88 to 4: 10: 92.
The fraction A and the fraction B are separately distilled in next steps to recover anisole, guaiacol and p-methoxyphenol.
In step IV, the method (100) includes subjecting the fraction A to batch distillation to recover anisole at a temperature ranging from 92°C to 98°C and a pressure ranging from 600 to 640 mm Hg, In step IV, guaiacol is recovered at 117°C to 123°C and a pressure ranging from 660 to 700 mm Hg and a decomposition mixture of anisole, phenol and guaiacol is distilled out at a temperature ranging from 132°C to 136°C and a pressure ranging from 590 to 630 mm of Hg. The decomposition mixture contains anisole, phenol and guaiacol in weight ratio ranging from 2: 9: 83 to 6: 13: 87. The purity of guaiacol recovered in step IV ranges from 97% to 99.99%.
In step V, the method (100) includes subjecting the fraction B to batch distillation to recover p-methoxyphenol at a temperature ranging from 115°C to 121°C and a pressure ranging from 680 to 720 mm Hg. The fraction ‘A’ and the fraction ‘B’ are also recovered in step V. The fraction A is recovered at a temperature ranging from 122°C to 126°C and at pressure ranging from 660 to 700 mm of Hg while the fraction B is recovered at a temperature ranging from130°C to 135°C and at a pressure ranging from 670 to 710 mm of Hg. Fraction A and fraction B can be subjected to further distillation for recovery of components. The purity of p-methoxyphenol recovered in step V ranges from 97% to 99.99%.
Further distillation of fraction A and Fraction B recovered in the process recovers fraction of guaiacol, anisole and p-methoxyphenol. The purity of anisole, p-methoxyphenol and guiacol recovered in the process ranges from 97% to 99.99%.
The process of preparation of guaiacol and p-methoxyphenol and the method (100) is further explained by way of illustrative example. The example is given by way of illustration and should not be construed to limit the scope of present invention.
Illustrative example 1
Anisole is reacted with hydrogen peroxide in acetone in the presence of a catalyst, wherein the weight proportion of anisole: hydrogen peroxide: solvent is 66:4:30. On completion of the reaction, guaiacol and p-methoxyphenol are formed in the reaction mixture. The reaction mixture contained anisole, acetone, p-methoxyphenol, guaiacol and tar in a weight ratio of 67: 30:2:1:0.2. Throughout the example, the components, Anisole, guaiacol phenol and p-methoxyphenol are respectively represented as A, G, P and M.
At step I, the reaction mixture was subjected to continuous distillation at atmospheric pressure with feed rate of 25-30 ton/h:
Step I : Continuous distillation
Components A, Acetone, M, G and Tar
Weight ratio 67: 30:2:1:0.2
Feed rate 25-30 ton/h
Temperature 56°C
Pressure Atmospheric pressure
Distillate 1 99% pure Acetone
Recovery rate 7.5 to 9 ton/h
Distillate 2 A, M, G and Tar in weight ratio 95.5:2.9:1.3:0.3
Recovery rate: 17.5-21 ton/h
At step II, the distillate 2 recovered at the end of step I was subjected to continuous distillation at a temperature ranging from 132°C to 140°C, a pressure ranging from 530 - 560 mm Hg and with a feed rate from 17.5 ton/h to 22 ton/h:
Step II : Continuous distillation
Feed A, M, G and Tar
Weight ratio 95.5:2.9:1.3:0.3
Feed rate 17.5-22 ton/h
Temperature 132°C to 140°C
Pressure 530-560 mm Hg
Distillate 1 99% pure Anisole
Recovery rate 16.1-20.2 ton/h
Distillate 2 A, M, G and Tar
weight ratio 50:31:15:3
Recovery rate: 1.4-1.8 ton/h
At step III, the distillate 2 from step II was subjected to batch distillation followed by flash distillation:
Step III : Batch distillation followed by flash distillation
Feed A, M, G and Tar
Weight ratio 50:31:15:3
Feed 19 ton
Distillates Pressure Temperature/ Purity/ weight ratio Quantity
A 620 mm Hg 94°C 99 % 11.35 ton
A, G, M
(Fraction A) 680 mm Hg 124°C 16:80:4 1.7 ton
A, G, M
(Fraction B) 700 mm Hg 140-105°C 2:8:90 5.5 ton
Tar -- -- -- 450 Kg
At step IV, the Fraction A from step III was subjected to batch distillation:
Step IV : Batch distillation
Feed A, G, M (Fraction A from stage III)
Weight ratio 16:80:4
Feed 1.7 ton
Distillates Pressure Temperature/ Purity/ weight ratio Quantity
A 610 mm Hg 93°C 99 % 0.2 ton
A:P:G
(decomposition mixture) 610 mm Hg 134°C 4:11:85 0.22 ton
G 680 mm Hg 120°C 99.8 1.22 ton
Tar -- -- -- 0.6 ton
At step V, the Fraction B from step IV was subjected to batch distillation:
Step V : Batch distillation
Feed A, G, M (Fraction B from stage III)
Weight ratio 2:8:90
Feed 5.5 ton
Distillates Pressure Temperature/ Purity/ weight ratio Quantity
A, G, M
(Fraction A) 680 mm Hg 124°C 16:80:4 0.58 ton
A, G, M
(Fraction B) 690 mm Hg 132°C 2:8:90 0.61 ton
M 700 mm Hg 118°C 99.8 4.3 ton
Tar -- -- -- Nil
The fraction A and B recovered from stage V was cycled back and mixed in step IV and V respectively in subsequent batches.
The distillation process of the reaction mixture thus gave guaiacol and p-methoxy phenol having 99.9 % purity. Anisole and acetone having 99% purity were recycled in the reaction.
Advantages of the invention:
1. P-methoxyphenol and guaiacol having 97% to 99% purity are separable using the method (100) of present invention.
2. The reactant i.e. anisole and the ketone solvent i.e. acetone are also recovered in pure form and can be reused in the reaction.
3. The present invention provides a single step process for preparation of guaiacol and p-methoxyphenol with inexpensive raw materials, reusable catalysts and minimal effluent with only water as a byproduct.
4. Present invention provides a cost effective method for separating guaiacol and p-methoxy phenol from the reaction mixture.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the scope of the claims of the present invention.

, Claims:We claim:
1. A process for preparation of guaiacol and p-methoxyphenol, the process comprising: reacting anisole with hydrogen peroxide in a ketone solvent in the presence of a catalyst, weight ratio of anisole: hydrogen peroxide: solvent ranging from 62: 3: 25 to 70 : 7: 35, to give a mixture of guaiacol and p-methoxyphenol, and subjecting the reaction mixture containing anisole, ketone solvent, guaiacol, p-methoxyphenol and tar in a weight ratio ranging from 62: 25: 0.5: 0.2: 0.1 to 70: 35: 4: 3: 1 to distillation by a distillation method (100);
characterized in that, the distillation method (100) is a combination of continuous distillation and batch distillation, the distillation method (100) comprising the steps of:
I) subjecting the reaction mixture to continuous distillation at atmospheric pressure to distil out the ketone solvent giving a resulting mixture of anisole, p-methoxyphenol, guiacol and tar in weight ratio ranging from 93: 1: 0.3: 0.2 to 97: 5: 2: 0.5;
II) subjecting the resulting mixture of step I to continuous distillation at a temperature ranging from 132°C to 140°C, and a pressure ranging from 530 - 560 mm Hg to distil out fraction of anisole, giving a resulting mixture of anisole, p-methoxyphenol, guiacol and tar in weight ratio ranging from 48: 29: 13: 1 to 52: 33: 17: 5;
III) subjecting the resulting mixture of step II to batch distillation followed by flash distillation to recover anisole at a temperature ranging from 92°C to 98°C and a pressure ranging from 600 to 640 mm Hg, to distil out a fraction A and a fraction B, wherein a portion of tar in p-methoxyphenol remains at a bottom;
IV) subjecting the fraction ‘A’ of step III to batch distillation to recover anisole at a temperature ranging from 92°C to 98°C and a pressure ranging from 600 to 640 mm Hg, to recover guaiacol at a temperature ranging from 117°C to 123°C and a pressure ranging from 660 to 700 mm Hg and distil out a decomposition mixture of anisole, phenol and guaiacol;
V) subjecting the fraction B of stage III to batch distillation to recover p-methoxyphenol at a temperature ranging from 115°C to 121°C and a pressure ranging from 680 to 720 mm Hg, and to distil out the fraction ‘A’ and the fraction ‘B’; and
VI) recycling the fraction ‘A’ and the fraction ‘B’ recovered from step V to the step IV and the step V respectively for further distillation,
wherein purity of recovered anisole, p-methoxyphenol and guiacol ranges from 97% to 99.99%.
2. The process for preparation of guaiacol and p-methoxyphenol as claimed in claim 1, wherein the solvent is any one selected from acetone, 2-butanone, tert-butylmethylketone, 2-hexanone and methylphenyl ketone.
3. The process for preparation of guaiacol and p-methoxyphenol as claimed in claim 1, wherein the fraction A contains anisole, guaiacol and p-methoxyphenol in a weight ratio ranging from 14: 78: 2 to 18: 82: 6.
4. The process for preparation of guaiacol and p-methoxyphenol as claimed in claim 1, wherein the fraction A is recovered at a temperature ranging from 122°C to 126°C and at pressure ranging from 660 to 700 mm of Hg.
5. The process for preparation of guaiacol and p-methoxyphenol as claimed in claim 1, wherein the fraction A is recovered at 124°C and 680 mm of Hg pressure.
6. The process for preparation of guaiacol and p-methoxyphenol as claimed in claim 1, wherein the fraction B contains anisole, guaiacol and p-methoxyphenol in a weight ratio ranging from 0.1: 6: 88 to 4: 10: 92.
7. The process for preparation of guaiacol and p-methoxyphenol as claimed in claim 1, wherein the fraction B is recovered at a temperature ranging from130°C to 135°C and at a pressure ranging from 670 to 710 mm of Hg.
8. The process for preparation of guaiacol and p-methoxyphenol as claimed in claim 1, wherein the fraction B is recovered at 132°C temperature and at 690 mm of Hg pressure.
9. The process for preparation of guaiacol and p-methoxyphenol as claimed in claim 1, wherein the decomposition mixture contains anisole, phenol and guaiacol in weight ratio ranging from 2: 9: 83 to 6: 13: 87.
10. The process for preparation of guaiacol and p-methoxyphenol as claimed in claim 1, wherein the decomposition mixture of anisole, phenol and guaiacol recovers at a temperature ranging from 132°C to 136°C and a pressure ranging from 590 to 630 mm of Hg.
Dated this on 4th day of October, 2022

Ashwini Kelkar
(Agent for the applicant)
(IN/PA-2461)