IE52057B1

IE52057B1 - A process for the o-substitution of phenols

Info

Publication number: IE52057B1
Application number: IE233381A
Authority: IE
Original assignee: Union Rheinische Braunkohlen
Priority date: 1981-01-10
Filing date: 1981-10-06
Publication date: 1987-05-27
Also published as: CH648280A5; DD206988A1; IE812333L; ATA379181A; AT375910B

Abstract

Phenols containing at least one free o-position are reacted with methanol and/or dimethyl ether in the presence of a catalyst which contains iron oxide, chromium oxide, one or more oxides of the elements titanium, zirconium, silicon, germanium, tin or lead, and one or more oxides of the alkali metals or alkaline earth metals, of lanthanum and of manganese in specific quantitative ratios to give the corresponding o-methylated phenols. [CH648280A5]

Description

This invention relates to a process for the o-substitution of phenols. More particularly, this invention relates to a process for the production of o-substituted phenols by reacting phenol, mono5 and di-alkyl phenols having at least one free imposition with methanol and/or dimethyl ether in the gaseous phase, in the presence of a catalyst.

The production of o-substituted phenols, for example 2,6-dimethyl phenol or 2,3,6-trimethyl phenol, ir, of considerable commercial interest because the first of these two phenol derivatives is required for numerous applications, particularly the production of polyphenylene oxide, whilst the second derivative may be used, for example, as a preliminary stage in the production of vitamin E. Although various synthetic processes are known from the patent literature, there has never been a process by which o-substitution products can be obtained highly selectively from phenols having free expositions with production times that are sufficiently long for practical application. Although phenol can be reacted to form 2,G-dimethyl phenol with a selectivity of the order of 99¾ in accordance with German Offenlegungsschrift No. 21 27 083, a selectivity of only 95¾ is obtained where o-cresol is used as the starting material.

I -3German Offenlegungsschrift No. 19 48 607 describes a process in which o-cresol is converted into 2,6-dimethy1 phenol with a selectivity of about 84%. Conversely, a selectivity of 98% is obtained with o-cre5 sol as the starting material according to German Offenlegungsschrift No.24 28 056. Where phenol is used, however, a selectivity of only 96.5% is achieved, falling to 92% after 150 hours. According to German Offenlegungsschrift no.25 47 309, 2,4,6-trimethyl phenol is obtained in a yield of 955 by methylating £-cresol, 2,3,6-trimethyl phenol being obtain in a yield of 94% from m-cresol, whereas according to German Offenlegungsschrift No.23 29 812 . 2,3,6-trir.iethyl phenol is obtained in a yield of 82% from in-cregoJ, According to the present invention, it has been found that phenols having at least one free o-position can he substituted in the o-position or positions by catalytic reaction with alcohols and/or their ethers by reacting phenol and/or mono- and/or di-alkyl phenols for 0.05 to 10 seconds with methanol and/or dimethyl ether in a molar ratio of 1:0.1-10, at a temperature of from 270 to 390°C in the gas phase in the presence of a catalyst comprising oxides of iron, chromium and silicon and at least one oxide selected from oxides of alkaline earth metals·, lanthanum and manqancse or of a catalyst comprising oxides of iron and chromium, one or more oxides selected from oxides of germanium, titanium, zirconium, tin and lead and at least one oxide selected from oxides of alkali -4metals, alkaline-earth metals, lanthanum and manganese, the molar ratios of the components amounting to 100:0.1-10: 0.1-10:0.01-10.

For alkylating phenol, mono- or di-alkyl phenols with alcohols and/or their ethers, the starting materials or mixtures thereof are vapourised in the usual way and introduced in the ratio indicated into a reactor in which the catalyst is arranged, for example in the form of a fixed bed. The reaction according to the invention may also be carried out advantageously in a fluidised bed. In addition, steam may be introduced with the starting materials in a quantity such that the molar ratio of phenol and/or alkyl and dialkyl- phenol to steam amounts to about 1:1-5. The reactor is Operated at a temperature in the range from 27O°C to 390°C and preferably at a temperature in the range from 300°C to 380°C. The reaction is generally carried out at normal pressure, although it may also be carried out advantageously under elevated pressure. Thus, it has been found, for example, that, where p-substituted phenols are used, equally good results are obtained even where pressures of up to about 30 bars are applied.

According to one embodiment of the invention, tho catalyst comprises a mixture of iron oxide, chromium oxide, silicon oxide and at least one oxide selected saost -5from oxides of alkaline-earth oxide metals, lanthanum and manganese in which the iron oxide may be present in excess. According to another embodiment, the catalyst comprises a mixture of iron oxide, chromium oxide, one or more oxides of germanium, titanium, zirconium, tin and lead and at least one oxide selected from oxides of alkali metals, alkaline earth metals, lanthanum and manganese. The oxides of germanium, titanium, zirconium, barium, calcium, strontium and manganese are preferred'.

The starting materials are used in a quantity such that a residence time of 0.01 to 10 seconds and preferably from 1 to 3.5 seconds is obtained.

After leaving the reactor, excess alcohol or ether is removed by distillation from the product mixture. The product mixture is then separated from the aqueous phase. Unreacted starting materials are distilled off and returned to the reactor.

The selectivity with which substitution takes place in the free o-positions generally amounts to 98 to 99%. Even after a production time of 2000 hours, there are still no signs of any significant reduction in the selectivity of the catalyst. A major advantage of the process according to the invention lies in the fact that the consumption of methanol is considerably lower than in conventional processes. -6The process according to the invention is illustrated by the following Examples.

EXAMPLE 1 A mixture of o-eresol and phenol, methanol 5 and water in a molar ratio of 1 (o-cresol and phenol) to 4 (methanol) to 2.6 (water) was introduced in vapour, form into a fixed-bed reactor heated to about 3G0°C and containing a catalyst consisting of iron oxide, silicon oxide, chromium oxide and calcium oxide in a molar ratio of 100:2:1:0.2. The starting materials were introduced under normal pressure in a quantity such that the residence time amounted to 3 seconds. The product leaving the reactor was cooled in countercurrent to the starting materials. Excess methanol was distilled off from the condensate accumulating. The aqueous phase was separated off from the sump.. The small quantity of o-cresol and phenol was distilled off from the organic phase, of which 99% consisted of 2,6-xylenol, and returned to the reactor. The 2,6-xylenol remaining in the sump, which still contained 0.5% of 2,4,6-trimethyl phenol, was subjected to fine distillation in another column.

The total yield of 2,6-xylenol, based on o-cresol and phono], amounted to 99%. The 2,6-xylenol obtained overhead was 99.9% pure. After 2000 hours, the catalyst still showed a selectivity of 98.2%. ί -7EXAMPLE 2 Phenol, dimethyl ether and water in a molar ratio of 1:2.5:2.5 were reacted in the vapour phase in the same way as described in Example 1. After working up, 2,G-xylenol was obtained with a selectivity of 99%. EXAMPLE 3 Phenol, methanol and water in a molar ratio of 1:0.5:2.5 were reacted in the vapour phase in the same way as described in Example 1, except that the reaction temperature was 340°C and the residence time 5 seconds. o-Cresol was obtained with a selectivity of 96% and 2,6-xylenol with a selectivity of 3.6%, based on the phenol reacted. Even after 2100 hours, the activity and selectivity of the catalyst showed only a negligible reduction.

EXAMPLE 4 o-Cresol, methanol and water in a ratio Of 1:2.5:2.5 were reacted in the same way as described in Example 1. The catalyst contained iron oxide, titanium oxide, chromium oxide and calcium Oxide in a molar ratio of 100:4.5:2:0.5. After working up, 2,6-xylenol was obtained with a selectivity of 99.1%, EXAMPLE 5 m-Cresol, methanol and water in a molar ratio -8of 1:5:2.5 were reacted in the same way as described in Example 1. The catalyst contained iron oxide, silicon oxide, chromium oxide and barium Oxide in a molar ratio of 100:2:1:0.2.

After working up, 2,3,6-trimethyl phenol was obtained with a selectivity of 99.5%.

EXAMPLE 6 £-Cresol, methanol and water were used in a molar ratio of 1:5:1 and reacted in the gaseous phase over the catalyst described in Example 1 under a pressure of 20 bars.

After working up, 2,4,6-trimethyl phenol was . obtained with a selectivity of 99%.

EXAMPLE 7 p-Cresol, methanol and water were reacted in a ratio of 1:0.5:0.5 in the same way as described in Example 1. 2,4-Xylenol was obtained with a selectivity of 96% and 2,4,6-trimethyl phenol with a selectivity of 3%.

EXAMPLE 8 o-Cresol, methanol and water in a ratio of 1:2.5:2.5 were reacted in the same way as described in Example 1. The catalyst contained iron oxide, germanium oxide, chromium oxide and barium oxide in a ratio of 100;2: :1. After working up, 2,6-xylenol was obtained with a selectivity of 99.2% 830 57 4 -9EXAMPLE 9 o-Cresol, methanol and water in a ratio of 1:2.5:2.5 were reacted in the same way as described in Example 1. The catalyst contained iron oxide, tin oxide, chromium oxide and calcium oxide in a molar ratio of 100:2:1:1.

After working up, 2,6-xylenol was obtained with a selectivity of 98.9%. Even after 2000 hours, there was no change in the activity or selectivity of the catalyst.

EXAMPLE 10 m-cresol, methanol and water in a molar ratio of 1:5:2.5 were reacted in the same way as described in Example 1. The catalyst contained iron oxide, germanium oxide, chromium oxide and barium oxide in a molar ratio of 100:2:1:1. After working up, 2,3,6-trimethyl phenol was obtained with a selectivity of 99.2%.

EXAMPLE 11 £-Cresol and methanol in a molar ratio of 1:5 wore reacted in the same way as described in Example 1, except that tho pressure was 5 bars. The catalyst contained iron oxide, zirconium oxide, chromium oxide and barium oxide in a molar ratio Of 100:2:1:1.

After working up, 2,4,6-trimethyl phenol was obtained with a selectivity of 99.2%. 53057 -10EXAMPLE 12 Phenol, methanol and water in a ratio of 1:0.5:2.5 were reacted in the same way as described in Example 1, but at 33O°C. The catalyst contained iron oxide, germanium oxide, chromium oxide and calcium oxide.

Working up showed that the phenol had reacted to form o-cresol with a selectivity Of 95% and 2,6xylenol with a selectivity of 4.5%. 'Less than 0.5% of secondary products were formed.

EXAMPLE 13 K mixture of o-cresol and phenol, methanol and water in a molar ratio of 1:4:2.6 was reacted in vapour phases as described in Example 1.

The yield of 2,6-xylenol, based on o15 cresol and phenol, amounted to 99.9%. The 2,6-xylenol obtained was 99.9% pure. After 2000 hours, the catalyst still showed a selectivity of 98.2%.

EXAMPLE 14 o-Cresol, methanol and water in a molar 20 ratio of 1:2.5:2.5 were reacted in the same way as described in Example 1. The catalyst consisted of iron oxide, zirconium oxide, chromium pxide and lanthanum oxide in a molar ratio of 100:3:2:0.5.

After working up, 2,6-xylenol was obtained 25 with a selectivity of 98.2%. 520 5 7 11EXAMPLE 15 o-Cresol, methanol and water in a molar ratio of 1:2.5:2.5 were reacted as described in Example 1. The catalyst contained iron oxide, tin oxide, chromium oxide and manganese oxide in a molar ratio of 100:2:1:1.

After working up, 2,6-xylenol was obtained with a selectivity of 98.7%.

EXAMPLE 16 m-Cresol, methanol and water in a molar ratio of 1:5:2.5 were reacted as described in Example 1. The catalyst contained iron oxide, germanium oxide, chromium oxide and lanthanum oxide in a molar ratio of 100:2:1:1.

After working up, 2,3,6-trimethylphenoi was obtained with a selectivity of 99%.

EXAMPLE 17 g-Cresol and methanol in a molar ratio of 1:5 were reacted as described in Example 1, except that a pressure of 5 bars was employed. The catalyst contained iron oxide, zirconium oxide, chromium oxide and manganese oxide ina molar ratio of 100:2:1:1. After working up, 2,4,6-trimethyl phenol was obtained with a selectivity of 99%.

EXAMPLE 18 Phenol, methanol and water in a molar ratio 58057 - 12 of 1:0.5:2.5 were reacted as described in Example 1, but at a temperature of 330°C. o-Cresol was obtained with a selectivity of 95% and 2,6-xylenol with a selectivity of 4.5%, based on the phenol reacted. The amount of secondary products was less than 0.5%.

Claims

1. Λ process for the production of an o-substituted phenol which comprises reacting phenol and/or mono- and/or di-alkyl phenol for 0.05 to 10 seconds with methanol 5 and/or dimethyl ether in a molar ratio of 1:0.1-10, at a temperature of from 270°C to 390°C, in the gaseous phase in the presence of a catalyst comprising oxides of iron, chromium, silicon and at least one oxide selected from oxides of alkaline-earth metals, lanthanum and manganese 10 or of a catalyst comprising oxides of iron and chromium, one or more oxides of germanium, titanium, zirconium, tin and lead and of at least one oxide selected from oxides of alkali metals, alkaline-earth metals, lanthanum and manganese, the molar ratios between the components amount15 ing to 100J0.1-10:0.1-10:0.01-10.

2. Λ process for the production of an o-substituted phenol which comprises reacting phenol and/or monoand/or di-alkyl phenol for 0.1 to 10 seconds with methanol and/or dimethyl ether in a molar ratio of 20 1:1-10, at a temperature of from

3. OO U C to 390°C, in the gaseous phase in the presence of a catalyst comprising oxides of iron, chromium, silicon and at least one alkaline-earth metal oxide, the molar ratios between the components amounting to 100:0.1-10:0.1-10:0.01-10. 25 3. Λ process for the production of an o-substituted phenol which comprises reacting phenol and/or monoand/or dialkyl phenol for 0.1 to 10 seconds with methanol and/or dimethyl ether in a molar ratio of -141:0.1-10, at a temperature of from 300 Q C to 390°C, in the gaseous phase in the presence Of a catalyst comprising oxides of iron, chromium, one or more Oxides of germanium, titanium, zirconium, tin and lead and of 5 at least one oxide selected from Oxide of alkali metals and alkaline-earth metals, the molar ratios between the components amounting to 100:0.1-10:0.1-10:0.01-10.

4. Λ process for the production of an osubstituted phenol which comprises reacting phenol 10 and/or mono- and/or di-alkyl phenol for 0.05 to 10 seconds with methanol and/or dimethyl ether in a molar ratio of 1:0.1-10, at a temperature of from 270 to 390“C in the gaseous phase in the presence of a catalyst comprising oxides of iron, chromium, silicon and at least 15 one alkaline-earth metal oxide, the molar ratios between the components amount to 100:0,1-10:0.1-10:0.01—10.

5. A process for the production of an osubstituted phenol which comprises reacting phenol and/or mono- and/or di-alkyl phenol for 0.05 to 10 seconds with 20 methanol and/or dimethyl ether in a molar ratio of' 1:0.1-10, at a temperature Of from 270°C to 39O°C, in the gaseous phase in the presence of a catalyst comprising oxides of iron, chromium, one or more oxides of germanium, titanium, zirconium, tin and lead and of 25 at least ono oxide selected from oxides of lanthanum -15and manganese, the molar ratios between the components amounting to 100:0.1-10:0.1-10:0.01-10.

6. A process as claimed in any of claims 1 to 5, wherein o-cresol is reacted in a molar ratio 5 of 1:0.5-5 with methanol and/or dimethyl ether.

7. A process as claimed in any of claims 1 to 5, wherein m-cresol or a mixture of m- and g-cresol is used.

8. A process as claimed in any of claims 1-to 10 5, wherein a mixture of o-cresol and phenol is used.

9. A process as claimed in any of claims 1 to 8, wherein the reaction is carried out at a temperature in the range from 300 to 380°C.

10. A process as claimed in any of claims 1 to 15 9, wherein the residence time is from 1 to 3.5 seconds.

11. A process as claimed in any of claims 1 to 4 and 6 to 9, wherein the catalyst contains one or more calcium oxide, barium oxide and strontium oxide.

12. A process as claimed in claim 1, 20 substantially as herein described with reference to any of the specific Examples.

13. An o-substituted phenol whenever prepared by a process claimed in a preceding claim.