IL33439A - Process for recovering m-alkylphenol from a mixture of alkylphenols - Google Patents

Description

/29/48 33439/2 A PROCESS FOR RECOVERING m-ALKYLPHENOI FROM A MIXTURE OF AIKYLPHENOLS Ψ' The present invention relates to a process for recovering m-alkylphenols from a mixture containing substantially m- and jo-alkylphenols. m-Alkylphenols are useful as the raw material for synthetic resins, as antioxidants, and as intermediates for agricultural chemicals. Particularly, m-isopropylphenol, m-sec-butyl henol and m-tert-butylphenol are useful as the intermediates for the insecticides of carbamate series.

For the preparation of high-purity m-alkylphenols , fp.w/ a synthetic method, which produces^--i-t5ie- by-products, may possibly be employed. In commercial production, however, an effective way may be to alkylate phenol to produce a mixture of various isomeric alkylphenols, enrich said mixture with m-alkylphenol by isomerization, and then recover m-alkylphenol from the resultant mixture by any suitable method of separation. However, even after the isomerization said mixture contains other alkylphenols than m-alkylphenol, such as ^-isomer in significant quantities, dialkylphenol in minor quantity, etc. As the boiling point of m-isomer differs very little from that of p-isomer, their separation by fractional distillation is extremely uneconomical. The separation utilizing the difference in melting points is also unsuitable for the commercial production because the melting point of m-isomer is lower than that of p-isomer.

In the Specification of German Patent No. 1,186,077, there is disclosed an industrial procedure for recovering m-tert-butylphenol from the admixture with ja-isomer.

Said procedure involves dissolving said mixture in a 10 aqueous caustic soda solution, cooling the resultant solution ' ■ ■'■ '· -· ' to precipitateySodiUin salt of '-'.^r -bu yl enol v/hich io «u ae¾uently r movtjd by tf: trat:.i.0J i , and acidifying the mother liquor to precipitate Ι.Ί-to v -buty1 nheno1. It is stated in said Patent Jpecification that the purity of jn-tert-butvlohenol obtained by. the above-mentioned salting out process is 8 7$· It is difficult to attain a purity of 85/··' or more by said process. Moreover, said process has no advantage from an industrial viewpoint, because not only it is difficult to attain a purity of 85'·' or more, but 0 also the content of ^-isomer in the m-isoraer product varies according to changes in the conditions of salting out, and moreover the filtration of said sodium salt is not . easy to carry out.

The present invention provides a process for ; . economically recovering, by chemical method, ^-alkylphenol . labout/ having a purity ofyfoT- or more from a crude m-alkylphenol' containing jj-isomer.

According to the present invention, a process for ;. producing a high-purity m-alkylphenol is provided, comprisin ; . · heating a mixture of m-alkylphenol and other alkylphenols* in ·,'■ ■·'··.'.. liquid phase and in the presence of either a strong acid as '■'.{' ■'■[ hereinafter defined or a solid acidic oxide containing silica and alumina, to cause the selective dealkylation of £-aikylphenol and alkylphenOls other than ra-alkylphenol.

. £-Alkylphenol is converted by way of dealkylation reaction . into phenol, which is readily separable from ra-alkylphenol ' by fractional distillation. The process of the present invention ·,', ·ν.,\ :" ' ; - ; is most effective for removing jj-isoraer from a raixture of isomers ■: but it is also useful to remove isomers other than m- or .·'··''. n-isomers .'frora the isomer mixture. and appended c.lnimn ia intended to mean those having a . dissociation constant of 1.0" or more at room temperature .

The e 'rong acids uc?ed in the present proceee include mineral acids such as sulfuric acid, phosphoric acid, and others, strongly acidic sulfonic acids such as jo-toluenesu fonic ( acid, naphthalenesulfonic acids, soluble solid acids of siLica-aluniina type, i.e. solid acidic oxides containing silica and alumina, such as acid clay, ■ - / may be used in the present process. In practising the present process, it is not preferable to use the strong acid and the in solid acid/admixture, because isomeriaation of m-isomer to £-isomer takes place predominantly.

In the present process the amount of acid used is, in the ca3e of strong acid, generally 0.05^5 per cent, · preferably 0.1 2 per cent based on the weight of alkyl-phenols, and in the case of solid acid, generally 1-^15 per cent, preferably 3^10 per cent based on the same.basis. the,, The temperature of^dealkylation reaction in the present process is preferably within a range from 140° to 220°C. depending upon the type of alkylphenol, the . ^ · pressure, and other reaction conditions. The dealkylation ·' reaction proceeds more smoothly at lower temperatures when an inert- gas is passed into the reaction system or the 1 reaction is carried out under reduced pressure than when the reaction is carried out under ordinary- pressure without taking any such measure.

The dealkylation reaction in the present process., may generally be completed in 2 to 10 hours. The reaction time varies according to the alkylphenols present, temperature and concentration of acid added.

The alkylphenols, to which the present invention is adaptable, include,' for example, isopropylphenol , >: ; sec- and tert-butylphenols, sec- and tert-amyl henols. sec- and tert-hexylphenols, etc.

The present process may be applicable to a mixture containing alkylphenols other than £-alkylphenol such as o-alkylphenol, 2, 4-dialkylphenol, etc. However, since the removal of £-alkylphenol f om m-alkylphenol is an urgent and difficult industrial problem, the present specification will deal primarily with this problem.

The dealkylation reaction in the present process may be expressed by the following reaction formula: H+ p-Alkylphenol ?► phenol + olefin.

Accordingly, olefin formed can be drawn from the reaction system by passing an inert gas stream into the reaction mixture or by evacuating the reactor. Phenol can easily be separated from m-alkylphenol by making use of the difference in boiling points. m-Alkylphenol can be recovered as a distillate by fractionally distilling the reaction mixture as it is or after being washed with water dr ing/ followed by The following examples are given to illustrate specific embodiments of the present invention, and are not to be coristrued to limit the scope of the invention defined in appended Claims.

Example 1 200 g. of mixed tert-butylphenols, containing m- and ^-isomer in a ratio of 70:30, and 4 g of 9&° sulfuric acid as a catalyst were introduced into a reactor provided with a stirrer, a thermometer and a condenser. The mixture was reacted at 180° - 185°C. for 6 hours with stirring. dried ( Then, the reaction mixture was washed with water, (€.ehy4a?a¼e& and distilled fractionally. 24 g of phenol containin /trace amount of o-tert-butylphenol were obtained as the initial distillate, followed by 140 g of the second fraction containing m-1ert-butylphenol and having a boiling range of 125° - 130°C./20 mmHg. According to the gas-chromatographic analysis, the composition of the said fraction was as follows: 88 m-tert-butyl henol; 12$ p-tert-butylphenol. .

Example 2 150 g of mixed tert-butyl henols containing m- and jD-isomer in a ratio of 70:30 was placed in a 500 cc flask provided with a stirrer, a thermometer, a gas inlet and a condenser. After the addition of 3 g of 98$ sulfuric acid as a catalyst, the mixture was reacted at 160° - 170°C. for well hours stirring/whxle nitrogen was introduced into the mixture at a rate of 200 cc/min. Then, the <3ried_/ reaction mixture was washed with water, Ie¾y3l¾¾e4 and distilled fractionally. 21 g of phenol was recovered as the initial fraction. The subsequent fraction, having a boiling range of 125° - 129°C./20 mmHg and containing m-tert-butylphenol, weighed 108 g. According to the gas-chromatographic analysis, the composition of said fraction was as follows: 94$ m-tert-butylphenol; 6.0$ p-tert-butylphenol.

Example 3 1,700 g of a mixture containing - and p-tert- butylphenol in a ratio of 55:45 and 34 g of 98 sulfuric acid as a catalyst were placed in the still of a vacuum distillation apparatus provided with a rectifying column.

The mixture was reacted in the still at a temperature of 150° - 160°C. while maintaining the inside reduced pressure at 50 mmHg. As the debutylation reaction proceeds, phenol formed, was distilled. After the reaction period of 7 hours when no more distillate at 80° - 105°C became recognizable, the reaction was stopped and 420 g of phenol were recovered.

The residue remained in the still was washed with water and drlecij to yield 930 g of an oily substance which contained 97$ of m-tert-butyl henol as determined by gas- chromatography.

Example 4 200 g of a mixture of m- and p-tert-butyl henol in a ratio of 70:30 and 1 g of 98$ sulfuric acid as a catalyst were added into a flask provided with a stirrer, a thermometer and an outlet tube for distillates. The mixture was reacted at a temperature of 210° - 215°C. with thorough stirring. During the period of reaction 28 g of phenol formed were recovered. The residue remained in the driedj flask was washed with water, / «5y35ft4e and distilled fractionally to yield 140 g of the distillate containing m-tert-butyl henol and having a boiling range of 126° - 130°C./20 mmHg. The content of m-tert-butyl henol in the said distillate was 93$ as determined by gas-chromatography.

Example 5 The reaction was conducted in the same manner as described in Example 4 except that 2 g of jo-toluenesulfonic acid was used as a catalyst. 30 g of phenol was recovered and 136 g of a distillate containing m-tert-butyl henol was obtained. According to the gas-chromatographic analysis, the composition of said distillate was as follows: 94 m-tert-butyl henol; 6.0% p-tert-butylphenol.

Example 6 Into a reactor provided with a stirrer, a thermometer, a gas inlet and a condenser, were added 200 g of a mixture of m- and p_-isopropylphenol in a ratio of 75:25 and 4 g of 98% sulfuric acid as a catalyst. The mixture was reacted at 180° - 185°C. for 6 hours with stirring while nitrogen was introduced into the mixture at a rate of 200 cc/min. Then, the reaction product was washed with dried/ water, (^iehsrch^ect-ed, and distilled fractionally. 18 g of phenol was recovered as the initial distillate. The subsequent distillate containing m-isopropylphenol and having a boiling range of 228° - 230°0. weighed 149 g.

The composition of said distillate as determined by the infrared analysis was as follows: 0% m-isopropylphenol; 10% j)-isopropylphenol.

Example 7 Into a reactor provided with a stirrer, a thermometer, a gas inlet -and a condenser, were added 300 g of a mixture of m- and p-tert-amyl henol in a ratio of 65:35 and 6 g of sulfuric acid as a catalyst, and the mixture was reacted at 160° - 165°C. for 5 hours with well stirring while nitrogen was introduced into the mixture at a rate of 250 cc/min. Then, the reaction mixture was washed with drledj water, (3«5y3¥a%e& and distilled fractionally. 52 g of phenol were recovered as the initial distillate. The subsequent distillate containing m-tert-amylphenol and having a boiling range of 250° - 255°C. weighed 200 g.

According to the gas-chromatographic analysis, the composition of said distillate was as follows: 93% m-tert-amylphenol; 1% p-tert-amylphenol.

Example 8 Into a flask provided with a stirrer, a thermometer, an outlet tube for distillates were added 200 g of a mixture of m- and p-tert-butyl henol in a ratio of 70:30 and 14 g of an acid clay as a catalyst. The mixture was reacted at 210° - 215°C Phenol distilled along with isobutylene, and the amount of phenol recovered during a reaction period of about 5 hours was 25 g. The residue remaining^ -9?e«eri«re (si the reaction flask was distilled fractionally, after the removal of catalyst by filtration, to yield 138 g of a distillate having a boiling range of 125° - 129°C./20 mmHg and containing m-tert-butylphenol. According to the gas-chromatographic analysis, the composition of said distillate was as follows: 9 m-tert-butyl henol ; & o JD-tert-butyl henol.

Example 9 Into a flask provided with a stirrer, a thermometer, a gas inlet tube and a condenser were added 150 g of f a mixture of m- and p-tert-butylphenol in a ratio of 73:27 and 7.5 g of an acid clay as a catalyst. The mixture was reacted at 180° - 185°C for 6 hours with well stirring while nitrogen was introduced into the mixture at a rate of 150 cc/min. The reaction product was freed f om the acid clay by filtration, and then distilled fractionally. 18 g of phenol was obtained as the initial distillate.

The subsequent distillate containing m-tert-butylphenol and having a boiling range of 125° - 130°C./20 mmHg weighed 108 g. The content of m-tert-butylphenol in said distillate was 93$ as determined by gas chromatography.

Example 10 300 g of a mixture of m- and p-tert-butyl henol in a ratio of 60:40 and 15 g of an acid clay as a catalyst were placed in a flask provided with a stirrer, a thermometer and a rectifying column connected to a vacuum distillation assembly. The mixture was reacted at a temperature of 145° - 155°C. under a reduced pressure of 50 mmHg. As the debutylation reaction proceeds, the phenol formed was allowed to distil from the reaction mixture, and 60 g of phenol were obtained in 7 hours. The liquid the flask was freed from the catalyst by filtration and distilled fractionally. The distillate having a boiling range of 126° - 130°C./20 mmHg and containing m-tert-butylphenol weighed 172 g. The content of m-tert-butylphenol in said distillate was 9 as determined by gas chromatography.

Example 11 The reaction was conducted in the same way as described in Example 2, using 300 g of a mixture of m- and p-tert-amylphenol in a ratio of 68:32 and 20 g of an acid clay as a catalyst. 45 g of phenol was recovered, and 190 g of the distillate having a boiling range of 114° -117°C./ll mmHg and containing m-tert-amylphenol was obtained. The content of m-tert-amylphenol in said distillate was 93 as determined by gas chromatography.

Claims (1)

1. A process for recovering which other in liquid phase and in the presence of either a strong acid defined or a solid acidic oxide silica and to cause alkylphenols other than 2 A process according to claim 1 wherein the strong acid is sulfuric phosphoric acid or naphthaleneoulfonic A process according to claim 2 wherein the amoun of strong acid is 5 per cent by weight based on the process according to claim 1 wherein the solid acidic oxide is an acid 5 A process according to claim 4 wherein the amount acid clay is 1 cent by weight based on the 6 A process according to claim 1 wherein dealkylation is carried out under reduced pressure while the phenol formed is distilled A process according to claim 1 wherein an inert gas is blown into the reaction A process according to claim 1 for recovering substantially as described in any of the foregoing r insufficientOCRQuality