DE1768679B1 - Process for the production of 3,5-dimethylphenol - Google Patents

Description

1 2

The invention relates to a method for production. The temperature rose to 62 ^° C. Afterward

of 3,5-dimethylphenol, which is characterized by being heated from the outside. A vigorous reflux is that one started m-xylene with concentrated sulfuric acid at 140 ° C. The water of reaction was collected in or weak oleum at temperatures of 140 to a Dean-Stark trap. The temperature of 220 ⁰ C, preferably with removal by distillation of the reaction 5 was set to 200 ° C at such a rate tion water, heated, further increases the reaction mixture without isolate that reflux tion under the control of 3,5-dimethylbenzenesulfonic held in at or a controlled reflux maintained in a known manner, the alkali melt could be subjected and out. The temperature of 200 ^° C. was maintained for the reaction mixture obtained, the 3,5-dimethyl-V for ₂ hours, and the phenol reaction mixture was obtained by acidification and distillation. io quenched in 2 liters of water.

In a modification of this procedure, the sulfonic acid was replaced by adding 80 g

Starting materials m-xylene and concentrated sulfur (2 mol) sodium hydroxide in 200 ml of water neutralized a reaction mixture ^{heated to 140 to 220 0} C, siert. A further 200 g (5 mol) of sodium hydroxide were added in a known manner by selective sulphonation, and the solution was evaporated to dryness with one of the m-isomers predominantly containing it. The mixture was stirred at 29o ⁰ C melted the xylene fraction below 130 ° C and separation and the temperature increased to 340 ° C, and that the unsulfonated hydrocarbons obtained temperature was ¹ J ₂ hours maintained is. The melt was quenched in 5 liters of water

The content of m-isomers in the xylene mixture is neutralized with concentrated hydrochloric acid. A low, the mixture is preferably separated in the presence of black oil, which solidified after an isomerization catalyst, first an iso-cooling. This solid was subjected to merization. Thus, a pressure of 20 Torr, for example, distilled and collected, the commercially available at 115 to 12O ⁰ C xylene with a low content of fraction passing over. The fraction bem-isomers by treatment with aluminum chloride was 120 g of pure 3,5-dimethylphenol (50% at 5O ⁰ C to obtain an about 50% of m-isomer 25 yield), a mixture containing rearranged. The sulfonation. .

the mixture was then treated with concentrated sulfur JS e 1 s ρ 1 e 1 2

acid at a temperature in the range from 150 to A mixture of m- and p-xylene containing 212 g (2 mol)

200 ^° C., the amount of the m-isomer and 150 g (1.4 mol) of the p-isomer sulfuric acid used containing approximately 1.1 mol per mole of the m-isomer was carried out at 120 ^° C. by addition of 220 g mers. The dimethylbenzene (2.2 mol) 98% sulfuric acid formed sulfonates. The sulfonic acid was neutralized with sodium carbonate, the mixture separated into two layers. As the bottom and the sodium sulfonate was fused, the sulfonic acid layer was converted from the reaction vessel with sodium hydroxide into the phenolate, removed and thus acidified by unreacted carbon. The 3,5-dihydrogen obtained was separated. Then, the xylene sulfonic acid was methylphenol containing 3,4- and 2,5-dimethylphenol V ₂ hours at 200 ⁰ C held as impurities by fractional distillation, the neutralization and Natriumhydroxydschmelze

tion were separated. was as in Example 1 using ins-

In the modified process, a total of 280 g (7 mol) of sodium hydroxide are passed through m-xylene and xylene mixtures containing m-xylene at a ratio of 40 leads.

moderately low temperatures sulfonated, expedient After acidification as in Example 1 was a

obtained moderately at a temperature within the brown oil, which under reduced pressure range 25 to 130 ⁰ C and advantageously at about (20 torr) with a yield of HOg one in 120 ⁰ C, for example at 115 to 125 ° C. The sulfo range from 90 to 120 ⁰ C boiling fraction distillation of m-xylene at such temperatures resulted in 45 lated. The fraction consisted of a 25% 2,4-dimethylbenzenesulfonic acid as determined by alkali 2,5-dimethylphenol and 75% 3,5-dimethylphenol melt and hydrolysis, the resulting mixture.

Product was 2,4-dimethylphenol. Three such series of experiments have also been carried out

found that after treatment of 2,4-dimethyl and the mixtures of the two as a product of any verbenzenesulfonic acid combined with concentrated or relative 50 search sequence dimethylphenols. The moderately concentrated sulfuric acid - z. B. one of two dimethylphenols were from the collected acid with a 60 to 95%, for example a product by fractional distillation at 20 Torr 81% concentration and at temperatures in a column with 50 floors with a withdrawal range 140 to 220 ° C, preferably 150 to 200 ⁰ C - separated from 10 g per hour, the acid converted to 3,5-dimethylbenzenesulfonic acid.

is stored, from which the corresponding dimethyl example

phenol is obtained after hydrolysis. A xylene fraction containing 212 g (2 moles) of the m-iso-

The important thing about the invention is above all meren, 212 g (2 mol) of the o-isomer and 100 g in it to be seen, by special sulfonation (0.94 mol) of the p-isomer, was at 12O ⁰ C conditions, especially with regard to the applied 60 by adding 220 g (2.2 mol) 98% igar sulfur temperature, a predominant sulfonation in 5-stelic acid sulfonated. After eliminating the non-recirculation or a rearrangement of the 4-sulfonic acid into the set hydrocarbon as in Example 2, the 5-sulfonic acid was obtained. Xylenesulfonic acid ¹ I treated at 200 ⁰ C for _{2 hours.}

_R. -Ii The neutralization and alkali melting were like

e 1 s ρ 1 e 65 in example 1 using a total of 280 g

212 g (2 moles) of m-xylene were carried out with 230 g (2.3 moles) (7 moles) of sodium hydroxide.

98% sulfuric acid for 15 minutes with vigorous acidification, 115 g of xylenol were obtained,

Stirring treated. the 25% 3,4-dimethylphenol and 75% 3,5-dimethyl-

contained phenol. The two phenols were obtained by fractional distillation at 20 torr in a column separated with 50 floors with a withdrawal of 10 g per hour. The 3,5-isomer had a boiling point of 117 ° C at 20 Torr and the 3,4-isomer has a boiling point of 124 ° C under the same conditions.

Example 4

A mixture of 2 moles of m-xylene and 1.4 moles of p-xylene was sulfonated with 2.2 moles of 98% strength sulfuric acid as in Example 2. After removal of the unreacted hydrocarbon, as in Example 2, the Xylosulfonsäure was maintained for 3 hours at 150 ⁰ C.

The neutralization and sodium hydroxide melt were carried out as in Example 2, 117 g of xylenol being obtained after acidification, which consisted of 25% 2,5-dimethylphenol and 75% 3,5-dimethylphenol. The two were phenols by fractional distillation - as described in Example 3 - separated, where the 2,5-isomers of the 3,5-isomers had a boiling point of 92 ° C at 20 Torr and a boiling point of 117 ⁰ C at the same pressure.

Example 5

A xylene mixture containing 2 mol of m-isomer, 0.47 mol of p-isomer and 2 mol of o-isomer was sulfonated with 2.2 mol of 98% strength sulfuric acid as in Example 3. After removal of the unreacted hydrocarbon, as in Example 2, the temperature of the xylene sulfonic acid was raised to 150 ⁰ C and maintained for 4 hours. Neutralization, sodium hydroxide melt and acidification as in the previous examples gave 125 g of a product containing 25% 3,4-dimethylphenol and 75% 3,5-dimethylphenol. The phenols were separated by fractional distillation at 20 Torr - as described in Example 3.

40 Example 6

414 g (4 mol) of m-xylene were treated with 460 g (4.6 mol) of 98% strength sulfuric acid for 15 minutes with vigorous stirring. The temperature rose to 65 ⁰ C. After cooling, two layers formed and the top hydrocarbon layer was separated. The sulphonation mixture was treated very carefully with concentrated hydrochloric acid, a vigorous evolution of hydrogen chloride taking place as a result of the reaction of the hydrochloric acid with unreacted sulfuric acid in the sulphonation mixture. After the addition of excess hydrochloric acid - ■ of which a total of 400 ml were required - colorless crystals separated out and were filtered off. The product was 2,4-dimethylbenzenesulfonic acid, 0.5 mol of which was converted into pure 2,4-dimethylphenol by neutralization and fusing with 1.75 mol of sodium hydroxide as in Example 1.

The overall yield of 2,4-dimethylbenzenesulfonic acid was 512 g (59%).

100 g of the 2,4-dimethylbenzenesulfonic acid obtained in the previous sulfonation were heated to 200 ° C. with 25 g of 81% strength sulfuric acid for 30 minutes. Reflux was observed with the temperature increasing from 150 to 200 ⁰ C. The reaction mixture was quenched in 21% of water. The neutralization and sodium hydroxide melt were carried out as in Example 1 using 140 g of sodium hydroxide. After cooling and acidification as in Example 1, a brown oil was obtained which was distilled at 20 torr. The fraction distilling off at 115 to 120 ^° C. was collected. This fraction consisted of 35 g of 3,5-dimethylphenol with a melting point of 68 ^° C.

Example 7

100 g of a mixture consisting of 25 g (0.24 mol) of the o-isomer, 20 g (0.19 mol) of the m-isomer and 55 g (0.52 mol) of the p-isomer was mixed with 20 g of anhydrous aluminum chloride Treated at 50 ⁰ C for 2 hours. The mixture was thoroughly stirred at 5O ⁰ C and a continuous stream of hydrogen chloride passed through the mixture. Analysis of the insoluble residue of the product indicated that the xylene mixture consisted of 20% of the o-isomer, 45% of the m-isomer and 35% of the p-isomer. The reaction product was thoroughly washed with water, dried over anhydrous sodium sulfate and how / sulfonated sulfuric acid in Example 2 using 25 g (0,25MoI) 98 °. ₆ The neutralization and sodium hydroxide melt were carried out as in Example 1 using a total of 36 g (0.9 mol) of sodium hydroxide.

After acidification a brown oil was obtained, which was distilled at 20 torr and gave 20 g of a fraction consisting of a mixture of 75% 3,5-dimethylphenol, 12% 3,4-dimethylphenol and 13% 2,5-dimethylphenol.

Ten such series of experiments were carried out and the resulting fractions consisting of the three dimethylphenols were combined. The dimethylphenols were separated from the combined product by fractional distillation at 20 torr in a column with 50 trays with a withdrawal of 10 g per hour. The boiling points of the 2,5-, 3,5- and 3,4-isomers at 20 torr were 92 and 117 and 124 ^° C. respectively.

Claims (2)

Patent claims: 1. A process for the preparation of 3,5-dimethylphenol, characterized in that m-xylene with concentrated sulfuric acid or oleum at low temperatures of 140 to 22O ⁰ C, preferably while distilling off the water of reaction, heating the reaction mixture without isolation of the 3, Subjecting 5-dimethylbenzenesulfonic acid to the alkali melt in a manner known per se and recovering the 3,5-dimethylphenol from the resulting reaction mixture by acidification and distillation. 2. Modification of the process according to claim 1, characterized in that instead of the starting materials m-xylene and concentrated sulfuric acid, a reaction mixture is ^{heated to 140 to 220 0} C, which in a known manner by selective sulfonation of the m-isomer in a predominantly containing this Xylene fraction below 130 ⁰ C and separation of the non-sulfonated hydrocarbons has been obtained.