Method for producing 2,3,5-trimethyl benzoquinone by oxidation of 2,3,6-trimethylphenol

Abstract

The invention relates to a method for producing 2,3,5-trimethyl benzoquinone or a compound containing 2,3,5-trimethyl benzoquinone, the method comprising the following steps: Oxidation of 2,3,6-trimethylphenol with oxygen or an oxygen-containing gas in a two- or multi-phase reaction medium in the presence of a catalyst or catalyst system containing at least one copper (II)-halide to a mixture containing 2,3,5-trimethyl benzoquinone, characterized in that the reaction medium contains water and at least one secondary aliphatic acyclic alcohol having 6 or more, preferably 7 or more, carbon atoms.

Claims

1. A process for preparing 2,3,5-trimethylbenzoquinone or a mixture comprising 2,3,5-trimethylbenzoquinone, comprising the following step: (i) oxidizing 2,3,6-trimethylphenol to 2,3,5-trimethylbenzoquinone with oxygen or an oxygen-containing gas in a two-phase or multiphase reaction medium in the presence of a catalyst or catalyst system at least comprising a copper(II) halide, to give a mixture comprising 2,3,5trimethylbenzoquinone, wherein the reaction medium comprises water and at least one secondary aliphatic acyclic alcohol having 6 or more carbon atoms.

2. The process according to claim 1, wherein said at least one secondary aliphatic acyclic alcohol having 7 or more carbon atoms.

3. The process according to claim 1, wherein the catalyst or the catalyst system comprises copper (II) chloride.

4. The process according to claim 1, wherein the catalyst or the catalyst system further comprises at least one alkali metal halide.

5. The process according to claim 4, wherein said at least one alkali metal halide is lithium chloride.

6. The process according to claim 1, wherein the reaction medium comprises 3-heptanol.

7. The process according to claim 1, wherein the process is carried out batchwise.

8. The process according to claim 1, wherein the mixture comprising 2,3,5-trimethylbenzoquinone is washed in a step (ii) with an aqueous alkaline solution.

9. The process according to claim 1, wherein the oxidation is carried out at a temperature of between 50° C. and 65° C.

10. The process according to claim 1, wherein the oxidation is carried out at a temperature of between 53 and 58° C. and the oxidation is carried out over a period of 4 to 7 hours.

11. The process according to claim 1, wherein the oxidation is carried out over a period of 4 to 8 hours.

12. The process according to claim 1, wherein the reaction medium, after oxidation has taken place, is subjected in a step (iii) to a phase separation, and the organic phase is extracted for recovery of the catalyst in solution in the organic phase.

Description

EXAMPLES 1 to 10

(1) A 4 L steel reactor was charged with 657 g of an aqueous reaction medium consisting of 151 g of CuCl.sub.2.2H.sub.2O, 150 g of LiCl, and 365 g of water, and with 818 g of the alcohol serving as solvent. With stirring, this two-phase mixture was brought to the desired starting temperature T.sub.D, and an oxygen-containing gas mixture was passed through it under atmospheric pressure. When the temperature T.sub.D has been reached, a 60 wt % strength solution of 500 g of 2,3,5-trimethylphenol (4) in the alcohol serving as solvent is supplied at a constant rate over a period t.sub.D. In order to complete the reaction, stirring is continued at the temperature T.sub.R for a time span t.sub.R.

(2) After the end of reaction and after cooling to room temperature, the phases are separated and weighed individually, and the organic phase is analyzed. The conversion of (4) is complete in all cases (>99.9%). There is little variation in the yield of quinone (1), which in all of the experiments is in the 90-95% range. The results are set out in table 1.

(3) As shown by a comparison of the inventive examples (I 2, 4, 6, 8, 10) with the associated comparative examples (C 1, 3, 5, 7, 9), the amounts of organically bonded chlorine when the reaction is carried out in a secondary alcohol for inventive use are lower on average by a factor of 3.5 than when using a primary alcohol. The total chlorine content, copper content, and lithium content of the organic phase is likewise much lower (on average by a factor of 6 for total chlorine, by a factor of 4.5 for copper, and by a factor of 18 for lithium).

(4) TABLE-US-00001 TABLE 1 Results of the oxidation experiments (I: inventive, C: comparative experiments). Cl.sub.tot, Cl.sup.−, Cl.sub.organic, Cu, Li, No. Solvent t.sub.D, h T.sub.D, ° C. t.sub.R, h T.sub.R, ° C. O.sub.2, SL/h N.sub.2, SL/h g/100 g g/100 g g/100 g g/100 g mg/kg C1 1-hexanol 3.25 58 2.75 58 90 60 2.3 2.2 0.1 1.2 2100 I2 3-heptanol 3.25 58 2.75 58 90 60 0.31 0.27 0.04 0.22 70 C3 1-hexanol 2.00 53 4.00 65 90 60 2.5 2.3 0.2 1.1 2100 I4 3-heptanol 2.00 53 4.00 65 90 60 0.31 0.26 0.05 0.21 65 C5 1-hexanol 1.00 53 5.00 58 150 0 2.2 2.1 0.1 1.1 1800 I6 3-heptanol 1.00 53 5.00 58 150 0 0.29 0.28 0.01 0.21 60 I7 3-heptanol 1.00 53 5.00 1 h, 53° C. 150 0 0.34 0.27 0.07 0.21 70 4 h 58° C. I8 2-octanol 1.00 53 5.00 58 150 0 0.47 0.42 0.05 0.29 230 C9 1-heptanol 1.00 53 5.00 58 150 0 1.80 1.60 0.20 0.92 1500 C10 1-octanol 1.00 53 5.00 58 150 0 1.70 1.50 0.20 0.83 1300

EXAMPLE 11

(5) A reaction effluent obtained from example 17 (reaction in 3-heptanol) is first washed with water. When phase separation has taken place the organic phase is extracted by shaking with aqueous HCl (25 wt %) and than washed with water again. Sodium hydroxide solution (2 wt %) is added to bring the solution to a pH of 6, and the solvent is removed under reduced pressure to an extent such as to give an approximately 75 wt % strength solution of trimethylquinone (1).

(6) In order to determine the thermal stability of this crude product, it is heated to 110° C. and the amount of (1) is determined at regular intervals by gas chromatography. After 125 hours, only 8% of the (1) originally present has undergone decomposition.

COMPARATIVE EXAMPLE 12

(7) Example 11 was repeated with the effluent from example C1 (reaction in 1-hexanol as solvent). On heating to 110° C., 44% of the quinone (1) originally present had undergone decomposition after 125 hours.