Title of Invention

"PROCESS FOR THE PREPARATION OF A MIXTURE OF ALKYL PHENOLS"

Abstract

A process for the preparation of mixture of alkyl phenols The invention relates to a process for the preparation of mixture of alkyl phenols. In the process, mixture of alkyl phenols, o-cresol and 2,6 xylenol are prepared by alkylation of phenol with methanol using boron oxide - zirconium oxide catalyst. The feed consisting of an alcohol and a phenolic compound are reacted at a temperature ranging between 300 - 450°C, at an atmospheric pressure to obtain the mixture of alkyl phenols.

Full Text

The present invention relates to a process for the preparation of mixture of alkyl phenols. More particularly it relates to the process for the preparation of o-cresol and 2,6 xylenol by alkylation of phenol with methanol using boron oxide - zirconium oxide catalyst,/ Alkyl phenols are industrially important chemical intermediates in the manufacture of pharmaceuticals, agrochemicals, resins, various additives, polymerization inhibitors, antioxidants and various other chemicals. Especially, ortho alkylated phenols, o-cresol and 2,6 xylenol and trialkyl substituted phenols are industrially important alkyl phenols. In the prior art, the catalysts used for alkylation of the phenol are ranging from zeolites to metal oxides. Reference may be made to U.S. Pat. No. 437174 wherein a process for the alkylation of phenols is described using a Y zeolite to both cresols and xylenols but no selectivity for 2,6 Xylenol. US pat. No.20010005769 describes a process for the alkylation of phenols using ortho selective cobalt/nickel ferrite catalyst with 75% conversion of phenol and 60% selectivity for 2,6 xylenol. European Pat. No. 1148040A1 describes a method for ortho-alkyaled phenols by reacting phenols with monohydric alcohol in presence of germanium oxide under conditions in which said alcohol is in supercritical condition. Most of these reported processes have the drawbacks such as; non selective catalysts for o-cresol or 2,6 xylenol, involves very critical control of catalyst structure and composition, low conversion of phenols and low conversion of alcohol to alkylated products producing large quantities of waste gases. It is therefore desirable to provide a process for the preparation of o-cresol and 2,6 xylenol using ortho selective catalyst which is comparatively easy to prepare, produces negligible quantities of p-cresol and removes the drawbacks of the earlier processes. The inventors of the present invention have observed that the use of boron oxide - zirconium oxide catalyst provided by the present invention removes the above mentioned drawbacks. The main object of the present invention is to provide a process for the preparation of mixture of alkyl phenols. More particularly it relates to the process for the preparation of o-cresol and 2,6 xylenol using boron oxide - zirconium oxide catalyst which obviates the above mentioned drawbacks. Another object is to provide a process for the said improved catalyst that gives high conversion and higher selectivity to o-cresol and 2,6 xylenol with negligible deactivation rate. Another object is to provide a process for the preparation of improved catalyst, which need not be prepared in situ and is easily prepared outside. Accordingly, the present invention provides a process for the preparation of a mixture of alkyl phenols which comprises; contacting catalyst with a feed consisting of an alcohol and a phenolic compound at weight hourly space velocity of 1 to 4 at a temperature ranging between 300 - 450°C, at an atmospheric pressure and collecting the mixture of alkyl phenols, o-cresol and 2,6 xylenol at - 5°C to +5°C. In another embodiment the alcohol used may be lower alcohol such as methanol or any other methylating agent such as dimethyl carbonate. In yet another embodiment the phenolic compound used can be phenol, methoxy phenol, o-cresol or methyl methoxy phenol. In another embodiment the ratio of alcohol to phenolic compound may vary from 1:1 to 10:1 (mol/mol). In still another embodiment the space velocity of the reaction mixture may vary from 1 to 4. WHSV (weight hourly space velocity expressed as grams of feed per gram of catalyst per hour). In another embodiment of the present invention, the catalyst used has general formula X B2O3: 1-x Zr02, where x may vary from 0.01 to 0.3 and characterized by XRD pattern showing amorphous or crystalline nature having surface area of 50 to 150 sq. m/g. In still another embodiment, the catalyst used is B203 - Zr02, wherein selectivity of ortho methylated products is not less than 60% and conversion of phenol is not less than 75%. In still another embodiment of the present invention, the catalyst is prepared as per the procedure which comprises preparing the solution of source of Zirconium and hydrolyzing with liquid ammonia, drying it at 100-300°C, adding this powdered form to a solution of source of boron under stirring, drying the resultant slurry and calcining it to suitable temperature, ranging from 500 to 750°C for 12 to 36 hours. The process of the present invention is described herein below with reference to the following examples, which are illustrative only and should not be construed to limit the scope of the present invention in any manner. The process of preparation of catalyst has been claimed in our co-pending application no. 0309/del/2003. Example 1 B2O3 - ZrO2 catalyst used in the present invention was prepared as follows: 39.7 g of zirconyl oxychloride [ZrOCl2, 8 H2O] was dissolved in 110 ml distilled water and aqueous ammonia (25%) was added to it drop wise with constant stirring till the solution became alkaline (pH=10). The resultant solution was filtered and washed with hot distilled water till free from chloride ions. The residue was dried overnight at 85 °C in an oven. 0.79 g boric acid [HjBOs] was dissolved in 150 ml distilled water. The zirconium hydroxide obtained above was added to the boric acid solution with stirring to obtain slurry. It was air-dried, heated in an oven at 110°C for 5h and calcined overnight at 650°C. The molar composition of the catalyst was 0.05 8203 : 0.95 ZrO2. Molar composition of the x 8263: 1-x ZrO2 catalyst was varied where x = 0.01 - 0.3. The catalyst was molded in the form of a pellet, which is granulated to -10 to +20 mesh size for its use in alkylation reaction. Examples 2-6 illustrate the process with various catalysts prepared as per example 1. EXAMPLE 2 3 g of catalyst prepared by the procedure given in the Example 1 was loaded in a tubular glass reactor of 15 mm diameter and 25 cm length. The upper part of the reactor was packed with inert ceramic beads as preheating zone. Phenol and Methanol were mixed and fed to the reactor using syringe pump. Reaction conditions were as follows. Activation of catalyst= Air/500°C/12h Reaction temperature = 400°C Carrier gas = N2 Phenol: Methanol = 1:4 (molar ratio) WHSV =2 The product was condensed at 7°C and collected in a receiver and analyzed by gas chromatography using Perkin Elmer Autosystem XL gas chromatograph (PE-1 column, 30m x 0.25mm x 1pm). Results after 5 hours from beginning of the reaction are shown below. Conversion of Phenol = 58.8% (Table Remove) Selectivity for o- Cresol = 53.9% Selectivity for 2,6 Xylenol = 17.3% There was negligible deactivation in catalyst activity and selectivity during this period. Also, mass balance was 85-90% showing good conversion of alcohol and less quantity of waste gases. EXAMPLE 3 Example 2 was repeated except the catalyst used was 1%B2O3: 99%ZrO2. Results after 5 hours from beginning of reaction are shown below. (Table Remove) Conversion of Phenol = 40.0% Selectivity for o- Cresol = 69.0% Selectivity for 2,6 Xylenol =8.7% EXAMPLE 4 Example 2 was repeated except the catalyst used was 3%B2O3: 97%ZrO2. Results after 5 hours from beginning of reaction are shown below. (Table Remove)Selectivity for o-Cresol =65.0% Selectivity for 2,6 Xylenol =12.3% EXAMPLE 5 Example 2 was repeated except the catalyst used was 20%B2O3: 80%ZrO2. Results after 5 hours from beginning of reaction are shown below. (Table Remove) Conversion of Phenol = 34.2% Selectivity for o- Cresol = 60.8% Selectivity for 2,6 Xylenol =13.4% EXAMPLE 6 Example 2 was repeated except the catalyst used was 30%B2C>3: 70%ZrC>2. Results after 5 hours from beginning of reaction are shown below. (Table Remove)Conversion of Phenol = 60.3% Selectivity for o- Cresol = 52.7% Selectivity for 2,6 Xylenol =24.0% Examples 7-9 illustrate the process where composition of the feed was varied. EXAMPLE 7 Example 2 was repeated except the mole ratio Phenol: Methanol was changed to 1:2. Results after 5 hours from beginning of reaction are shown below. (Table Remove)Conversion of Phenol =60.8% Selectivity for o- Cresol = 45.0% Selectivity for 2,6 Xylenol =14.8% EXAMPLE 8 Example 2 was repeated except the mol ratio phenol: methanol was 1:7. Results after 5 hours from beginning of reaction are shown below. (Table Remove)Conversion of Phenol =67.1% Selectivity for o- Cresol = 43.6% Selectivity for 2,6 Xylenol =27.8% EXAMPLE 9 Example 2 was repeated except the mole ratio Phenol : Methanol was 1:10. Results after 5 hours from beginning of reaction are shown below. (Table Remove) Conversion of Phenol = 84.2% Selectivity for o- Cresol = 36.3% Selectivity for 2,6 Xylenol =35.3% Examples 10-11 illustrate the process by changing the residence time of the feed. EXAMPLE 10 Example 2 was repeated except the WHSV was changed to 1 .Results after 5 hours from beginning of reaction are shown below. (Table Remove)Conversion of Phenol =67.7% Selectivity for o- Cresol = 42.2% Selectivity for 2,6 Xylenol =18.4% EXAMPLE 11 Example 2 was repeated except the WHSV was changed to 4. Results after 5 hours from beginning of reaction are shown below. (Table Remove) Conversion of Phenol =53.9% Selectivity for o- Cresol = 56.9% Selectivity for 2,6 Xylenol =25.6% Examples 12 and 13 illustrate the effect of temperature on the process. EXAMPLE 12 Example 2 was repeated except the temperature for the reaction was changed to 350°C. Results after 5 hours from beginning of reaction are shown below. (Table Remove)EXAMPLE 13 Example 2 was repeated except the temperature of the reaction was changed to 450°C. Results after 5 hours from beginning of reaction are shown below. (Table Remove) Conversion of Phenol =55.2% Selectivity for o- Cresol =47.1 % Selectivity for 2,6 Xylenol =17.2% EXAMPLE 14 Example 2 was repeated except 20 weight % of water was added to the feed. Results after 5 hours from beginning of reaction are shown below. (Table Remove) Conversion of Phenol =57.1% Selectivity for o- Cresol = 51.0% Selectivity for 2,6 Xylenol =16.8% EXAMPLE 15 Example 2 was repeated except the dimethylcarbonate is used as a methylating agent. Results after 5 hours from beginning of reaction are shown below. (Table Remove)Conversion of Phenol =64.9% Selectivity for o- Cresol = 48.4% Selectivity for 2,6 Xylenol =27.6% The main advantages of the present invention are: 1. Alkylation of phenol using ortho selective catalyst. 2. Catalyst is easy to synthesize. 3. The process produces negligible amount of p- cresol. 4. It also gives good conversion of phenol and good selectivity for ortho alkyl products in addition to the negligible deactivation over length of time. 5. Good recovery showing less quantity of waste gases. We Claim: 1. A process for the preparation of a mixture of alkyl phenols which comprises; contacting catalyst with a feed consisting of an alcohol and a phenolic compound at weight hourly space velocity of 1 to 4 at a temperature ranging between 300 - 450°C, at an atmospheric pressure and collecting the mixture of alkyl phenols, o-cresol and 2,6 xylenol at -5°C to +5°C. 2. A process as claimed in claim 1, wherein the alcohol used is lower alcohol such as methanol, or any other methylating agent such as dimethyl carbonate. 3. A process as claimed in claims 1 - 2, wherein the phenolic compound used is phenol, methoxy phenol or o-cresol or methyl methoxy phenol. 4. A process as claimed in claims 1-3, wherein the molar ratio of alcohol to phenolic compound vary from 1 : 1 to 10 : 1. 5. A process as claimed in claims 1-4, wherein, the catalyst used is B203 -Zr02 having surface area of 50 to 150 sq.m/g. 6. A process for the preparation of mixture of alkyl phenols substantially as herein described with reference to the examples.

Documents:

302-DEL-2003-Abstract-(28-11-2008).pdf

302-del-2003-abstract.pdf

302-DEL-2003-Claims-(28-11-2008).pdf

302-del-2003-claims.pdf

302-del-2003-correspondence-others-(16-12-2008).pdf

302-DEL-2003-Correspondence-Others-(28-11-2008).pdf

302-del-2003-correspondence-others.pdf

302-del-2003-correspondence-po.pdf

302-del-2003-description (complete)-(16-12-2008).pdf

302-DEL-2003-Description (Complete)-(28-11-2008).pdf

302-del-2003-description (complete).pdf

302-del-2003-form-1.pdf

302-del-2003-form-18.pdf

302-del-2003-form-2.pdf

302-DEL-2003-Form-3-(28-11-2008).pdf

302-del-2003-form-3.pdf