RU2126785C1 - Process for preparation of 2,3,5-trimethylhydroquinone - Google Patents

Abstract

FIELD: chemical industry. SUBSTANCE: 2,3,5- trimethylhydroquinone is prepared from 3-nitro-o-xylene by reducing 3-nitro-o-xylene to 2,3-xylidine on catalyst containing iron and chromium oxides or active aluminium oxide promoted by alkali and alkaline-earth metal ions. Reducing agent includes C₁-C₃ primary alcohols at 320-350 C and atmospheric pressure. The resulting 2,3-xylidine is subsequently diazotized to 2,3-xylenol, the latter is methylated in vapor phase with methanol over the same catalyst, and the resulting 2,3,6-trimethylphenol is oxidized to 2,3,5-trimethylhydroquinone by chemical or electrochemical methods. EFFECT: more efficient preparation process. 10 ex

Description

 The invention relates to an improved method for producing 2,3,5-trimethylhydroquinone (TMHH), an intermediate in the production of vitamin E.

 The main feature of modern methods for the preparation of TMHC is that they are all based on the preliminary preparation of 2,3,6-trimethylphenol, which is then oxidized using various methods to 2,3,5-trimethylbenzoquinone, the latter is hydrogenated to 2,3,5-trimethylhydroquinone.

Недостатком указанного метода является его многостадийность, сложность технологии, низкий выход целевого продукта - 17,3% мас. /1/. Химико-фармацевтический журнал, Москва, Медицина 1988 г., с. 1246.So there is a method of producing 2,3,5-trimethylhydroquinone from pseudocumene with preliminary protection of the reactive position 5 by the introduction of bromine or sulfo group according to the scheme:

The disadvantage of this method is its multi-stage, the complexity of the technology, the low yield of the target product is 17.3% wt. /1/. Chemical Pharmaceuticals Journal, Moscow, Medicine 1988, p. 1246.

Недостатками данного способа являются низкий выход - 17,2% целевого продукта и отсутствие сырья - диэтилкетона.A known method of producing trimethylhydroquinone based on diethyl ketone / 1 / according to the scheme:

The disadvantages of this method are the low yield of 17.2% of the target product and the lack of raw materials - diethyl ketone.

Однако данных о параметрах проведения процесса и выходе целевого продукта нет и сравнение провести по этим показателям не представляется возможным. Суть патента заключается в алкилировании 4-метоксифенола метанолом при температуре 350-550^oC и давлении 1-70 атм. над катализатором. В качестве катализатора обычно используется MgO или Al₂O₃ с активирующими добавками окислов V, Ti, Ce, Mn, Zn и Fe. В результате неполного или избыточного метилирования получают смесь, содержащую 2,3,6-триметилгидрохинон и 8 наименований побочных продуктов, которые после разделения необходимо вернуть в цикл или утилизировать.The patent literature refers to one of the well-known methods for producing 2,3,5-trimethylhydroquinone, starting from Phenol (prototype) / 2 / (US Patent 4060561, C 07 C 39 / 08.77)

However, there is no data on the parameters of the process and the yield of the target product and it is not possible to carry out a comparison on these indicators. The essence of the patent is the alkylation of 4-methoxyphenol with methanol at a temperature of 350-550 ^o C and a pressure of 1-70 atm. over the catalyst. MgO or Al ₂ O ₃ with activating additives of oxides V, Ti, Ce, Mn, Zn and Fe is usually used as a catalyst. As a result of incomplete or excessive methylation, a mixture is obtained containing 2,3,6-trimethylhydroquinone and 8 types of by-products, which, after separation, must be recycled or disposed of.

 An example of a prototype.

A mixture of 21.05 g of 4-methoxyphenol, 27.2 g of MeOH and 1.7 g of water is passed under pressure at 503 ^° C. through a granular layer for 1 hour. The reaction product is cooled, condensed and left overnight, then the organic liquid phase is separated from the solid and analyzed by gas chromatography. The total content of trimethylhydroquinone in both phases is 22.1%.

The disadvantages of the above method of obtaining TMHC are:
1) low selectivity of the process for the target product
2) the need to introduce a complex stage of separation of by-products, their identification
3) the need to recycle non-methylated products
4) the complexity of the process in terms of multi-stage technological scheme
5) low yield of TMHH.

 The purpose of this invention is to simplify the process, increase the yield of the target product and improve working conditions.

3-нитро-о-ксилол обычно восстанавливают молекулярным водородом в присутствии катализатора Pd/C при температуре 55-60^oC и давлении 5-10 атм. в автоклаве до 2,3-ксилидина. Неожиданно для авторов изобретения оказалось возможным проведение реакции восстановления 3-нитро-о-ксилола на не типичном для такого типа реакций окисном железо-хромовом катализаторе, используя в качестве донора водорода - метиловый спирт (или первичные спирты C_2-3) в реакторе проточного типа при атмосферном давлении и температуре 340-350^oC до 2,3-ксилидина. Выделение 2,3-ксилидина основано на отгонке метанола, применяемого как растворитель и реагент одновременно. Затем 2,3-ксилидин диазотируют в водной среде нитритом натрия до 2,3-ксиленола; 2,3-ксиленол метилируют в паровой фазе над тем же железо-хромовым катализатором или над активной окисью алюминия, промотированной ионами щелочных и щелочно-земельных металлов [Mg²⁺, Mn²⁺, Ca²⁺, Cr²⁺, Fe²⁺] при температуре 340-350^oC.This goal is achieved in that 2,3,5-trimethylhydroquinone is prepared according to the following scheme starting from 3-nitro-o-xylene:

3-nitro-o-xylene is usually reduced with molecular hydrogen in the presence of a Pd / C catalyst at a temperature of 55-60 ^o C and a pressure of 5-10 ATM. autoclave to 2,3-xylidine. Unexpectedly, it turned out to be possible for the inventors to carry out the reduction reaction of 3-nitro-o-xylene on an oxide-iron-chromium catalyst not typical of this type of reaction using methyl alcohol (or C _2-3 primary alcohols) as a hydrogen donor in a flow-type reactor at atmospheric pressure and a temperature of 340-350 ^o C to 2,3-xylidine. The isolation of 2,3-xylidine is based on the distillation of methanol, used both as a solvent and a reagent at the same time. Then 2,3-xylidine is diazotized in aqueous medium with sodium nitrite to 2,3-xylenol; 2,3-xylenol is methylated in the vapor phase over the same iron-chromium catalyst or over active aluminum oxide promoted with alkali and alkaline earth metal ions [Mg ²⁺ , Mn ²⁺ , Ca ²⁺ , Cr ²⁺ , Fe ²⁺ ] at a temperature of 340-350 ^o C.

 The resulting 2,3,6-trimethylphenol is subjected to chemical or electrochemical oxidation to 2,3,5-trimethylbenzoquinone, followed by reduction to 2,3,5-trimethylhydroquinone with any suitable reducing agent (molecular hydrogen, sodium hydrosulfite) or the electrochemical method.

As chemical oxidizing agents, atmospheric oxygen is used in the presence of catalysts containing monovalent copper, chromium compounds, hypohalogenites at a temperature of 30-65 ^o C. In the case of electrochemical oxidation, the final reaction product of 2,3,5-trimethylhydroquinone is obtained without isolation of 2,3,5- trimethylbenzoquinone as an intermediate of the reaction.

 The total yield of the target product (TMHC) in all stages is 46.6-48.5% wt.

 The invention is illustrated by the following examples.

реализуется одновременно с реакцией каталитического восстановления 3-нитро-о-ксилола.Example N 1. Obtaining 2,3-xylidine
A solution of 151 g (1 mol) of 3-nitro-o-xylene in methanol (35740% concentration) at a rate of 100-250 ml / h from the feed tank is dispensed by the batcher into the evaporation zone of a flow reactor previously purged with nitrogen. The reactor is a cylindrical apparatus made of stainless steel, equipped with electric heating, a thermocouple filled with granular Fe / Cr catalyst of the CTK-1-7 brand. The temperature in the evaporator zone is maintained at 200-250 ^o C, in the reaction zone 340-350 ^o C
Methanol catalytic steam reforming reaction

It is realized simultaneously with the catalytic reduction reaction of 3-nitro-o-xylene.

 The reaction products after passing through the refrigerator-condenser are collected in a receiver and then excess methanol is distilled off on a rotary-film evaporator. 119.8 g of 2,3-xylidine are obtained. Yield 99%.

 Analogously to example 1, it is possible to use other primary alcohols as a reducing agent, moreover, alcohols from isostructure remove the hydrogen atom under milder conditions.

 Example No. 2. Obtaining 2,3-xylidine in ethyl alcohol.

A solution of 151 g (1 mol) of 3-nitro-o-xylene in 226.5 g of ethanol at a speed of 100-250 ml / h is fed to the reactor at a temperature in the evaporator zone of 200-250 ^o C, in the reaction zone of 320-330 ^o C 118.4 g of 2,3-xylidine are obtained. Yield 97.8% wt.

 Example No. 3. Obtaining 2,3-xylidine in isopropyl alcohol.

A solution containing 151 g (1 mol) of 3-nitro-o-xylene in 226.5 g of isopropyl alcohol at a speed of 100-250 ml / tea is fed into the evaporation zone of the reactor at a temperature of 200-250 ^o C. The temperature in the reaction zone is 320- 330 ^o C. Receive 118.6 g of 2,3-xylidine with a yield of 98% May,
Example No. 4. Obtaining 2,3-xylene.

In a four-necked round-bottom flask (V = 2000 ml) equipped with a stirrer, thermometer, dropping funnel and reflux condenser, 350 ml of tetrachlorethylene and 121 g (1.0 mol) of 2,3-xylidine are then charged. Then, with good stirring, 1 l of water and portions are charged 260.7 g (2.5 mol) of concentrated hydrochloric acid are added, maintaining the temperature of the reaction mixture with a thermostat 5-10 ^o C. An aqueous solution of sodium nitrite is added dropwise to the resulting suspension of hydrochloric acid 2,3-xylidine at such a rate as to prevent strong foaming and overheating of rea translational masses above +10 ^o C. After dosing the sodium nitrite the reaction mass under stirring is slowly heated to a temperature of 50 ^o C and kept at this temperature for two hours to complete decomposition of the diazonium salt.

At the end of the diazotization reaction, the reaction mass is an easily exfoliating liquid. The lower layer - a solution of 2,3-xylene in tetrachlorethylene is separated from the aqueous layer and on a rotary-film evaporator at a temperature of 60-80 ^o C and P = 20 mm Hg tetrachlorethylene is distilled off.

 The cube after distillation of tetrachlorethylene (raw xylene) is a yellow to brown crystalline product with a basic substance content of 95-99%. It is subjected to steam distillation to remove tar. The distillation of 2,3-xylenol is carried out until the distillate sample ceases to form turbidity with bromine water. The distillate from the receiver-phase separator is poured into a glass, cooled in an ice tank, water is drained by decantation, separating the crystallized 2,3-xylenol. 72.6 g of 2,3-xylenol are obtained. Yield 60% of theory.

Example No. 5. Obtaining 2,3,6-trimethylphenol
The 2,3-xylenol vapor phase methylation reactor is similar to the methanol catalytic steam reforming reactor described in Example 1 and is a stainless steel cylindrical apparatus equipped with electric heating, a thermocouple filled with CTK-1-7 iron-chromium catalyst.

The temperature in the evaporator zone is maintained at 200-250 ^o C, in the reaction zone 340-350 ^o C. A 35-40% solution of 2,3-xylenol in methanol is preliminarily prepared and it is poured into a raw material measuring tank. After reaching the required temperature in the evaporator and reactor and purging them with nitrogen, raw materials are supplied to the inlet of the evaporator with a dosing pump at a speed of 100-150 ml / hour. The feed rate is determined by the volume of the reactor and the activity of the catalyst. The reaction products, leaving the reactor, are condensed into a condenser refrigerator and collected in an alkylate collector; they are a solution of 2,3,6-trimethylphenol in methanol with impurities of reaction water. Alkylate is evaporated in a conventional distillation apparatus at 65-95 ^° C. from water and methanol. Crystalline 2,3,6-trimethylphenol is obtained. The conversion of 2,3-xylenol 99%, the methylation selectivity for 2,3,6-trimethylphenol 98% wt. The yield is 97.0%.

 Example No. 6.

Obtaining 2,3,6-trimethylphenol by vapor phase methylation on an aluminum-calcium catalyst, promoted with Fe ^{2+ ions} , is carried out analogously to example 5. The amount of promoter in the finished catalyst is 5-10% wt. Active γ-alumina of grade A promoted by alkali and alkaline earth metal ions [Mg ²⁺ , Mn ²⁺ , Ca ²⁺ , Cr ²⁺ , Fe ²⁺ ] is used as a support in the catalyst.
Obtain 2,3,6-trimethylphenol with a selectivity of 94-98%. The conversion of 2,3-xylenol ranges from 98 to 89%.

 Example No. 7.

Obtaining 2,3,5-trimethylhydroquinone. A 5-6% solution of 2,3,6-trimethylphenol in methanol is preliminarily prepared. Then, 250 g of a solution of 2,3,6-trimethylphenol in methanol and 6.1 g of an oxidation catalyst based on alumina hydrate, Cu ⁺ , Cl ^- are charged into a V = 0.5 L reactor equipped with a bubbler, thermometer, reflux condenser and stirrer ^. , PO PO $\genfrac{}{}{0ex}{}{\text{-3}}{\text{4}}$ ., Li ⁺ , NH NH $\genfrac{}{}{0ex}{}{\text{+}}{\text{4}}$ . Then, at a temperature of 30-65 ^o , preferably 64-65 ^o C, air is bubbled at a speed of 200 ml / hour for 4-5 hours with effective stirring. Then the catalyst is filtered off, the filtrate is evaporated. Obtain 11.7 g of 2,3,5-trimethylbenzoquinone with a yield of 85% by weight, which is treated with an aqueous solution of sodium hydrosulfite, extracted with ether in a volume ratio of 1: 1, the ether is distilled off and 2,3,5-trimethylhydroquinone is obtained in 95- 97% in terms of 2,3,5-trimethylbenzoquinone.

 Example N 8.

The oxidation reaction of 2,3,6-trimethylphenol is carried out analogously to example 7, but after filtering the oxidation catalyst, the filtrate (a solution of 2,3,5-trimethylbenzoquinone in methanol) is placed in a "duck" and reduced with molecular hydrogen on a suspended Pd / C catalyst at a temperature 55-60 ^o C. Then the hydrogenation catalyst is filtered off, methanol is distilled off. Get 2,3,5-trimethylhydroquinone with a yield of 98-99% wt. in terms of trimethylbenzoquinone.

 Example No. 9.

The oxidation of 2,3,6-trimethylphenol is carried out with a 6-10% aqueous solution of sodium hypochlorite at a temperature of 25-50 ^o C and pH = 9 ^o C13.5 in an aqueous alkaline medium for 2-3 hours at a molar ratio of 2 3,5-trimethylphenol: sodium hypochlorite = 1: 5. Then the reaction temperature is increased to 90-95 ^o C, maintained with stirring for another 1.5 hours. The resulting 2,3,5-trimethylhydroquinone is extracted with tetrachlorethylene at a volume ratio of reaction mass: tetrachlorethylene = 1: 1 3 times. The extract is evaporated on a rotary film evaporator in vacuo and get 2,3,5-trimethylhydroquinone with a yield of 87.1-90% wt. in terms of 2,3,6-trimethylphenol.

 Example No. 10. Electrochemical redox process for producing 2,3,5-trimethylhydroquinone.

150 ml of 10% H ₂ SO _{4 are} poured into the anode chamber of the membrane electrolyzer, and 40 ml of 20% H ₂ SO _{4 are} added to the cathode. As an anode, PbO ₂ with an area of 150 cm is used, the cathode is lead or copper. At a temperature of 8-10 ^o C and a current strength of 5A conduct electrolysis for 30 minutes. Then, the current is turned off, 50 ml of anolyte are drained and a solution of 5 g (0.036 m) of 2,3,6-trimethylphenol in 50 ml of acetone is poured into the anode chamber. The oxidation process is carried out at a temperature of 30-40 ^o C, current 3A for 2 hours. Then the reaction mass is poured from the anode space into the cathode.

The electroreduction of 2,3,5-trimethylquinone is carried out by a current of 3 A at a temperature of 30-40 ^o C for one hour. The resulting 2,3,5-trimethylhydroquinone is extracted with an organic solvent (chlorocarbons, aromatic hydrocarbons, esters or ketones) and reprecipitated from the solution with hexane, heptane or cyclohexane. The yield of 2,3,5-trimethylhydroquinone 4.7-5 g (85-90% wt.) In terms of 2,3,6-trimethylphenol.

 Thus, the method proposed by the authors for producing 2,3,5-trimethylhydroquinone differs from the prototype in the nature of the raw materials used, the high selectivity of the process and the practical absence of reaction by-products, and higher yield of the target product. 46.6-48.5% compared with 22.1% of the prototype, the complexity of the use of methanol as a solvent and reagent.

Claims (1)

A method for producing 2,3,5-trimethylhydroquinone, including alkylation of phenol, oxidation of the obtained alkyl phenol, hydrogenation of alkyl benzoquinone, characterized in that the starting 3-nitro-o-xylene is reduced with primary C ₁ -C ₃ alcohol on a catalyst containing iron and chromium oxides, at 320 - 350 ^o C to 2,3-xylidine, which is diazotized to 2,3-xylenol, followed by methylation of the latter in the vapor phase with methanol on a catalyst containing oxides of iron and chromium, or an active alumina promoted with alkali and alkaline earth Ferrous materials (Mg ^2+, Mn ^2+, Ca ^2+, Cr ^2+, Fe ²⁺⁾ at 340 - 350 ^o C, followed by oxidation of 2,3,6-trimethylphenol obtained by atmospheric oxygen in the presence of a catalyst based on aluminum oxide hydrate containing Cu ⁺ , Cl ^- , PO $\genfrac{}{}{0ex}{}{\text{-3}}{\text{4}}$ , Li ⁺ , NH $\genfrac{}{}{0ex}{}{\text{+}}{\text{4}}$ or hypohalogenite at 30 - 65 ^o C, by hydrogenation of the obtained trimethylbenzoquinone with molecular hydrogen in methanol in the presence of a Pd / C catalyst at 55 - 60 ^o C or sodium hydrosulfite to the target product, or 2,3,6-trimethylphenol obtained after methylation is subjected to electrochemical oxidation -reduction process at a current strength of 3A, in acetone, at 30 - 40 ^o C to the target product.