KR20000052844A - Method for preparing trimethylbenzoquinone - Google Patents

Abstract

PURPOSE: A novel method for preparing trimethylbenzoquinone(TMBQ) by oxidizing trimethylphenol(TMP) is provided, which is based on a method for oxidizing trimethylphenol(TMP) by a catalytic system consisting of heteropolyacids. CONSTITUTION: A process for the preparation of trimethylbenzoquinone comprises of: preparing heteropolyacids(H7PMo8V4O40;HPA); oxidizing TMP to TMBQ by a batch process(pouring all reactant(i.e., TMP melted by heating in oven at 70°C, HPA solution, acetic acid, and ortho-dichlorobenzene) into a flask consisting of refrigerator and machinery shaker at beginning of reaction) or a semi-batch process(adding TMP dissolved in organic solvent drop by drop with syringe or syringe pump) under 1 atmospheric pressure of oxygen in 50°C water bath(a flowing rate of oxygen is 12L/h); extracting TMBQ dissolved by catalyst from bottom by washing the hydro phase with ortho-dichlorobenzene for 2 times; analyzing two phase, i.e., hydro phase and organic phase by HPLC; investigating re-circulating property of a catalytic system in a solvent of ortho-dichlorobenzene/acetic acid/water=50ml/56ml/14ml.

Description

Method for preparing trimethylbenzoquinone {METHOD FOR PREPARING TRIMETHYLBENZOQUINONE}

For example, according to Mitsubishi Gas Kagaku Co., Ltd. patent (EP 127 888 or EP 167 153), it has been known for a long time to oxidize TMP to TMBQ, which is a major intermediate in the synthesis of vitamin E.

According to the patent, TMP is oxidized by oxygen-rich air, where the reaction is catalyzed by copper salts in a three-phase gas / alcohol / water system. The molten TMP runs continuously. At the end of the reaction, after decantation, the catalyst in the aqueous phase is recycled and the TMBQ in the alcohol phase is separated off after various treatments. This process allows for 100% TMP conversion and 95% TMBQ yield.

Scheme

The method has a number of disadvantages because the catalyst system is partially soluble in the organic phase consisting of TMBQ and solvent. Its regeneration requires acidification of the organic phase for quantitative recovery of the catalyst. This type of catalysis essentially requires the use of specialty materials to avoid corrosion resulting from the use of chlorinated derivatives from catalysis.

Certain catalysts (heteropolyacid catalysts) and partition coefficients for this oxidation have been addressed by the disadvantages of this process by using solvent media suitable for recovery and recycling of the catalyst.

Heteropolyacid (HPA) refers to the acid form of heteropolyanions; Heteropolyanions are heteroatoms X (X = B ³⁺ , Si ⁴⁺ , Ge ⁴⁺ , P ⁵⁺ , As ^5+, etc.), which are one or two central atoms, and polyatoms which are 4 to 18 periphery It is an oxoanion containing Y (Y = W, Mo, V).

It is also possible to include heteropolyanions or one of salts thereof in the heteropolyacids. In the solid state, HPA or salts thereof are composed of heteropolyanions, counterions (H ⁺ ions or metal cations) and crystalline water molecules.

Heteropolyanions can be distinguished into two main structures.

KEGGIN structure for heteropolyanions of Formula X ^{p +} M ₁₂ O ₄₀ ^(8-p)-

The structure most often described in the literature is the keggin structure, with a metal atom / heteroatom ratio of 12/1. In this structure, the group VI metal atom M (M preferably represents Mo or W) may be mostly substituted or slightly substituted by group V atoms (M ′ = V, Co, etc.). The resulting HPA of the form X ^{p +} M _12-n M ′ _n O ₄₀ ^{(8-p + n)} -is referred to as mixed HPA-n.

¡ ^{Æ a} DAWSON structure for heteropolyanions of formula (X ^{p +} ) ₂ M ₁₈ O ₆₂ ^(16-2p)-

In this structure, the metal atom / heteroatom ratio is 9/1. This structure consists of two fragments X ^{p +} M ₉ O ₃₄ ^(14-p) -which are bound.

In the context of various HPA preparations, heteropolyanions are generally synthesized by condensing oxoanions containing metal oxides and heteroatoms X in an acidic medium.

For the mixed heteropolyanion synthesis of the keggin structure, it is possible to use specific synthesis methods described in the literature and allowing the mixed heteropolyanions to be obtained directly.

a) For HPA-ns of type H _{3 + n} PMo _12-n V _n O ₄₀ , where n is 1 or more and 6 or less:

Three conventional methods are described in the literature together with the latest original methods by electrodialysis.

See, P. COURTIN, F. CHAUVEAU, P. SOUCHAY in a Compte-rendu de l'Academie des Sciences, 258, 1964, 1247-1250. It is possible. This method consists of treating sulfuric acid with sodium molybdate, phosphate and vanadate, followed by reflux heating, cooling and dissolving. The HPA-n formed is extracted from the aqueous solution with ether, and after extraction, the solvent is sufficiently evaporated to produce HPA-n in crystalline form. However, when the yield is low and n increases, a large excess of vanadate has to be used and a large number of by-products are obtained.

For example, according to Japanese Patent JP 77138499 it is also known to prepare heteropolyacids of the formula H ₅ PMo ₁₀ V ₂ O ₄₀ from molybdenum oxide (MoO ₃ ) and vanadium oxide (V ₂ O ₅ ) and phosphoric acid. The three compounds are dissolved in water by reflux heating for 20 days. The solution is then concentrated to drive pure crystals of HPA-2.

Furthermore, according to ODYAKOV et al., Kinetics and Catalysis, 36, 1995, 733-738, n is 1 or more from a solution of H ₃ PO ₄ , MoO ₃ and decabanadium acid H ₆ V ₁₀ O ₂₈ . It is also known to produce HPA-ns of 6 or less.

The amounts of P, Mo and V 3 species to be introduced are adjusted in accordance with the stoichiometry of the HPA-n to be synthesized. The decabanadium acid solution is obtained by dissolving vanadium pentoxide V ₂ O ₅ in a cooled aqueous solution containing 4 to 6% hydrogen peroxide.

To synthesize HPA-ns with n of 1 to 4, the decabanadium acid solution is gradually added to a dilute mixture of MoO ₃ and H ₃ PO ₄ to boil it. Stirring and boiling continue until MoO ₃ is completely dissolved, then the mixture is filtered. The filtrate is recovered, which is an aqueous solution of HPA-n.

In order to synthesize HPA-ns in which n is larger than 4, HPA-n 'solution in which n' is 1 or more and 4 or less is used instead of MoO ₃ . The HPA-n 'solution is mixed with H ₃ PO ₄ , the mixture is boiled and then the decabanadium acid solution is added slowly. Water is evaporated, the mixture is filtered and the residue is dissolved in 5% hydrogen peroxide solution and added back to the filtrate.

In 1995, KHOZHEVNIKOV Catalysis Reviews-Sciences Engineering, 37, 1995, 311-352, proposed a novel synthesis method by electrodialysis. HPA is formed at the anode in aqueous solution, while electrolysis of water occurs at the cathode. The two electrodes are separated by a cation exchange membrane. No by-products are formed. The yield reaches 100%.

HPA is used in both homogeneous and heterogeneous catalysts. These may be supported on silica, activated carbon or ion exchange resins.

The main applications of HPA in acid catalysis include condensation of phenols, hydration and dehydration, esterification and etherification, nitrification, epoxide phase reactions, acetolysis, carbonylation, isomerization, oligomerization, alkylation, dealkylation And transalkylation.

In terms of oxidation, the most commonly used HPA is molybdobanadophosphate due to its high oxidation potential and good thermal stability. This HPA-ns catalyzes the oxidation of both organic and inorganic materials. In this case, the oxidizing agent of the reaction may be O ₂ or H ₂ O ₂ .

The reduced forms of these HPAs can be readily reoxidized by O ₂ .

The main applications in redox catalysis are alkanes (preparation of maleic anhydride, oxidation of cycloalkanes to alcohols and ketones, oxidative dehydrogenation, oxidation of methane, etc.), alkenes, alcohols (primary, secondary alcohols, etc.) , Aldehydes, and inorganics (N ₂ H ₄ , NO, H ₂ S, etc.).

Many authors have envisioned the possibility of catalyzing the oxidation of TMP → TMBQ by HPA-containing systems in a homogeneous H ₂ O / AcOH system. Various types of HPA were tested according to different procedures.

That is, according to the publication of KHOLDEEVA et al. In Journal of Molecular Catalysis, 75, 1992, 235-244, 86% with TMP / HPA (H ₇ PMo ₈ V ₄ O ₄₀ keggin structure) with molar ratio of 20. It is known that the TMBQ yield of can be achieved.

In addition, according to SHIMIZU et al., Published in Tetrahedron Letters, 30, 1989, 471-474, the oxidation of TMP → TMBQ can be carried out in the presence of HPA and hydrogen peroxide of formula H ₇ PMo ₁₂ O ₄₀ . This is known.

In Tetrahedron Letters, 33, 1992, 1795-1798, R. NEUMANN was reacted with H ₅ PV ₂ Mo ₁₀ O ₄₀ in hexanol under 1 atmosphere of oxygen for 4 hours at 60 ° C. for a TMP / HPA ratio of 50. The oxidation from catalyzed, 2,3,5-trimethylphenol to TMBQ is described. This person achieved 73% selectivity for 75% conversion.

There is another study that has made it possible to oxidize TMP to TMBQ by carbon-supported HPA; Research by JANSEN and colleagues in the Journal of Molecular Catalysis A chemical, 107, 1996, 241-246 falls into this category.

The present invention relates to a novel process for the production of trimethylbenzoquinone (TMBQ) by oxidation of trimethylphenol (TMP). More specifically, the present invention relates to a process for the oxidation of trimethylphenol by a catalyst system consisting of heteropolyacids.

The realization of this oxidation reaction with easy recycling of the catalyst is not described in any paper. The present invention has achieved this object. The present invention relates to a process for preparing trimethylbenzoquinone by oxidizing trimethylphenol in the presence of an oxidant selected from oxygen and hydrogen peroxide and a heteropolyacid, wherein the reaction is carried out in a two-phase liquid medium. It features.

The trimethylphenol is preferably 2,3,6-trimethylphenol and the trimethylbenzoquinone obtained is especially 2,3,5-trimethylbenzoquinone.

Heteropolyacids are preferably selected from kegin-structured heteropolyacids or Dawson-structured heteropolyacids, and salts of heteropolyacids may also be used in the context of the present invention.

The reaction medium consists of an aqueous mixture consisting of water and monobasic or dibasic organic carboxylic acids having 2 to 6 carbon atoms, preferably acetic acid. Preference is given to using volume ratios of organic acids and water of 95/5 to 20/80; It is particularly preferable to use a volume ratio of 80/20 to 60/40.

The water-immiscible solvents that enable the obtaining of a two-phase system with the aqueous phase are selected from aliphatic or aromatic hydrocarbons with their halogenated derivatives, preferably their chlorinated derivatives. Particular preference is given to using ortho-dichlorobenzene.

The volume ratio between the solvent and the aqueous system (water and organic acid) is preferably 30/70 to 90/10, more preferably 30/70 to 50/50.

The molar ratio between trimethylphenol and heteropolyacid is preferably 200/1 to 5/1, more preferably approximately 10/1.

The weight ratio between the HPA and the TMP assembly for a liquid medium consisting of a solvent and an aqueous medium is preferably 0.1 to 15%, more preferably approximately 6%.

Regarding the reaction conditions, it is preferable to work at a temperature of 30 ° C. or higher, preferably 50 to 70 ° C. The oxygen pressure is preferably 0.2 to 1 bar.

According to a preferred embodiment of the present invention, after the reaction, the reaction medium is decanted to separate the solvent containing TMBQ from the aqueous phase containing HPA. The organic phase is then dehydrated, the solvent is distilled off and recycled to a new oxidation step to distill the TMBQ. The aqueous phase is optionally ortho-dichlorobenzene treated to remove dissolved TMBQ and then optionally concentrated before recycling to the oxidation step.

By this process, no brine water treatment is required and no inorganic salts are produced, all of the solvent used is recycled and the TMBQ produced is of high purity. Due to the nature of the reactants used, the choice of compatible materials is simplified because the use of chlorination catalysts eliminates the aforementioned corrosion problems.

The invention is more fully illustrated by the following examples.

I) Preparation of Heteropoly Acid

Preparation of H ₇ PMo ₈ V ₄ O ₄₀ according to the procedure described in ODYAKOV et al., Kinetics and Catalysis, 36, 1995, 733-738.

II) Oxidation from TMP to TMBQ

Some experiments are performed batchwise by introducing all reactants at the start of the reaction; Another experiment is carried out in a semi-batch manner by gradually introducing a predetermined amount of TMP to be oxidized.

a) assembly

The reaction is carried out in a 250 ml four neck round bottom flask equipped with a cooler, frit and a mechanical stirrer. The reaction medium is heated using a thermostat. Pure oxygen is circulated in the reactor so that the reaction medium is subjected to one atmosphere of oxygen pressure. The flow meter controls the circulating flow rate of oxygen.

In the case of semi-batch experiments, TMP dissolved in an organic solvent is added dropwise to the reaction medium using a syringe and a syringe pump. Since the speed of the syringe pump is adjustable, it is possible to set the addition speed.

b) procedure

All experiments are carried out in a 50 ° C. thermostat at an oxygen flow rate of 12 L / h.

For batch run experiments

3 g of TMP are heated in molten form, ie in an oven at 70 ° C. and then charged into the reactor. 15 ml of an aqueous solution of HPA (H ₇ PMo ₈ V ₄ O ₄₀ ) having a concentration of 0.15 mol / l are added, followed by 55 ml of acetic acid followed by 50 ml of ortho-dichlorobenzene.

Agitation and oxygen circulation are initiated. The reaction medium is placed in a water bath at 50 ° C.

After 2 hours of reaction, the reaction mixture is emptied into a decanting funnel and the reactor is washed with 30 ml of ortho-dichlorobenzene. The recovered aqueous phase is washed twice with 30 ml of ortho-dichlorobenzene to extract TMBQ dissolved in catalyst at the bottom. All phases are recovered and weighed to determine their relative volume.

For half-batch performance experiments

Follow the above procedure but modify it as follows:

3 g of TMP was dissolved in an organic solvent (50 ml) and the solution was fed over 1 hour 30 minutes using a syringe and a syringe pump; At the end of the addition, a finishing time of 30 minutes is allowed under stirring and oxygen pressure.

TMBQ and catalyst recovery at the bottom are the same as in the batch process.

c) results

HPLC analysis of two phases, aqueous phase and organic phase:

The conversion of TMP is DC = 100% and the yield of TMBQ, ie the amount of TMBQ obtained for the introduced TMP, is RY = 84%. The main impurity is hexamethyldiphenol (HMDP), which is well known as a reaction byproduct, in addition to heavy products that are not analyzed. Batch and semicontinuous results are substantially the same.

One of the most interesting results is that the catalyst remains quantitative in the aqueous phase and is recycled to itself without further treatment.

III) Recyclability Study of Catalyst System

Recyclability Experiment

We investigated the recyclability of the catalyst system in the highest performance two phase system, namely ortho-dichlorobenzene / acetic acid / water medium = 50 ml / 56 ml / 14 ml. The inventors worked batchwise.

a) assembly

The assembly used for the repeated experiments is the same as that used for the batch experiments in heterogeneous media.

b) procedure

The aqueous phase containing the catalyst obtained at the end of the first catalyst cycle described in the preceding paragraph is evaporated on a Rotavapor until black oil is obtained. It is then made 56 ml with acetic acid and then 14 ml of water is added.

TMP (3 g) is heated in molten form, ie in an oven at 70 ° C. and then charged into the reactor. The catalyst solution is added followed by 50 ml of ortho-dichlorobenzene.

After doing this, the procedure is the same as in the first catalyst cycle.

c) results

We performed three cycles starting from the same catalyst system. Each oxidation reaction occurred under the same operating conditions.

HPA used: H ₇ PMo ₈ V ₄ O ₄₀

T = 50 ° C

P = oxygen 1 atm

Moles of TMP / Mole of HPA = 10

Composition of organic solvents / acetic acid / water medium: 50 ml / 56 ml / 14 ml

Duration = 2 h

DC% Selectivity% RY TMBQ% RY HMDP% Primary catalytic cycle 100 84 84 0.2 2nd catalytic cycle 100 86 86 One 3rd catalytic cycle 100 85 85 2

The activity of the catalyst system did not decrease between each cycle.

Claims (12)

A process for preparing 2,3,5-trimethylbenzoquinone by oxidation of 2,3,6-trimethylphenol in the presence of an oxidant selected from oxygen and hydrogen peroxide and heteropolyacids, characterized in that the reaction is carried out in a two-phase liquid medium . The method of claim 1 wherein the heteropolyacid is selected from keggin-structured heteropolyacids or Dawson-structured heteropolyacids. 2. The process of claim 1 wherein the reaction medium consists of an aqueous mixture of water and a monobasic or dibasic organic carboxylic acid having 2 to 6 carbon atoms and a water-immiscible organic solvent. 4. Process according to claim 3, characterized in that the volume ratio of acetic acid and water is 95/5 to 20/80, preferably 80/20 to 60/40. 4. The process of claim 3, wherein the water immiscible solvent is selected from aliphatic or aromatic hydrocarbons and their halogenated derivatives. 6. The process of claim 5 wherein the water immiscible solvent is ortho-dichlorobenzene. 4. Process according to claim 3, characterized in that the volume ratio between the solvent and the aqueous system is 30/70 to 90/10, preferably 30/70 to 50/50. 2. Process according to claim 1, characterized in that the molar ratio between trimethylphenol and heteropolyacid is between 200/1 and 5/1, preferably approximately 10/1. The method of claim 1 wherein the weight ratio between HPA and TMP assembly to a liquid medium consisting of a solvent and an aqueous medium is 0.1 to 15%, preferably approximately 6%. 2. The process according to claim 1, wherein the reaction temperature is at least 30 ° C., preferably from 50 to 70 ° C. 3. The method of claim 1 wherein the oxygen pressure is between 0.2 and 1 bar. The method of claim 1 wherein after reaction, the reaction medium is decanted to separate the solvent containing TMBQ from the aqueous phase containing HPA, then the organic phase is dehydrated, the solvent is distilled off and then recycled for a new oxidation step and the TMBQ removed. Distilling and optionally treating the ortho-dichlorobenzene to remove dissolved TMBQ and then concentrated to recycle to the oxidation step.