Method for making cycloaliphatic epoxidesPatent US6084111
(2000)
Patent US5767150
(1998)
The new method involves low level of catalyst composition and no organic acid and/or peracid, which results in simple product workup and process. The present invention uses hydrogen peroxide in the presence of
(a) tungstic acid or its metal salts,
(b) phosphoric acid or its metal salts,
(c) at least one phase transfer catalyst.
The epoxidation of unsaturated cyclic substrates with hydrogen peroxide in the presence of tungsten catalyst, phosphoric acid or its salt, and phase transfer catalyst can be performed at any temperature which is sufficient to react, however, particularly suitable temperatures are between 0°C. and 100°C., preferably from 25°C. to 70°C. The reaction takes place faster at higher temperature and requires shorter time to complete. The reaction is typically exothermic. Slow addition of hydrogen peroxide is preferred to control the exotherm. The reaction can be performed at pressures from subatmospheric to superatmospheric; however, the reaction is preferably carried out at atmospheric pressure.
The epoxidation can be performed with or without solvent. Solvent can be used to reduce the viscosity. If solvent is needed, water immiscible organic solvents such as chlorinated hydrocarbons, ethers, glycol ethers, hydrocarbons, combinations thereof, can be used. Particular suitable organic solvents are toluene, chlorobenzene, chloroform, methylene chloride, and the like.
Hydrogen peroxide solution is used as oxidant in the concentration of 5 to 70%. The amount of hydrogen peroxide can vary depending on the desired degree of epoxidation, typically from 0.1 to 1.5 equivalent per unsaturated double bond.
The phase transfer catalyst can be used from 0.001 to 1, preferably 0.05 to 0. 1, equivalents per equivalent of carbon--carbon double bond. Suitable phase transfer catalysts includes quaternary ammonium salts, quaternary phosphonium salts, and polyethers.
Phosphoric acid or its various salts can be used from 0.001 to 0.5 equivalents per equivalent of carbon-carbon double bond. Sodium or potassium salts of monobasic, dibasic, or tribasic salts of phosphoric acid can also be used. The final pH can be adjusted by other acids or bases to 0-5.
Tungsten catalysts can be used from 0.001 to 50% by weight based on the cyclic substrates. Tungstic acid or its metal salts can be used as the metal catalysts, the metal salts are water soluble and the acid is not. The typical catalyst is used from 0.005 to 1% and the preferred catalyst is tungstic acid which is not water soluble. Either tungstic acid which is not water soluble or its metal salts which are soluble can be used as the metal catalyst. The typical catalyst is used in amounts of about 0.005 to 1%, based on weight of unsaturated compound. The preferred metal catalyst is tungstic acid.
The expoxidation can be performed with or without solvent. The use of solvent is preferred because it reduces the viscosity. If solvent is desired, a water immiscible organic solvent such as chlorinated hydrocarbons, and ethers, glycol ethers, hydrocarbons, and combinations thereof, are especially useful. Particularly suitable organic solvents are toluene, chlorobenzene, chloroform, methylene chloride, heptane, and the like.
The method of the invention allows use of a low level of catalyst composition free of organic acid and/or peracid, resulting in simple product workup and process, and using readily available catalysts.
Example 2Preparation of Diepoxide from Unsaturated Diester (epoxidation of a compound containing two cyclohexene rings bound together by a ester function)
Product from Example 1(100.0 g) was added to a reactor, followed by tungstic acid (0.80 g), phosphoric acid (85%, 0.40 g), sodium hydroxide (25%, 0.40 g), Aliquat 336 (0.80 g), and toluene (200.0 g). The mixture was stirred and heated to 50°C. when slow addition of hydrogen peroxide (30%, 65.0 ml) began. The hydrogen peroxide addition was completed in 70 minutes to control the exotherm. The reaction mixture was kept at 50°C. for 2.5 additional hours when no residual starting material was detected by GC and FTIR.
The final mixture was separated into two phases. The organic phase was isolated and washed twice with 50 ml of water to remove the excess hydrogen peroxide. The final dicycloaliphatic epoxide was isolated by removing solvent at 95°C. under reduced pressure which has epoxy equivalent weight of 280.1 g/eq (yield 94.0 g).
Example 4Preparation of Diepoxide from Unsaturated Dicyclic Diester (epoxidation of a compound containing two cyclohexene rings similar to the above)
Unsaturated dicyclic diester from Example 3 (100.0 g) was added to a reactor, followed by tungstic acid (0.80 g), phosphoric acid (85%, 0.40 g), sodium hydroxide (25%, 0.40 g), Aliquot 336 (0.80 g), and toluene (200.0 g). The mixture was stirred and heated to 50°C. when slow addition of hydrogen peroxide (30%, 70.0 ml) began. The hydrogen peroxide addition was completed in 40 min to control the exotherm. The reaction mixture was kept at 50°C. for 2.0 additional hours when no residual starting material was detected by GC and FTIR.
The final mixture was separated into two phases, the organic phase was isolated and washed twice with 50 ml of water to remove the excess hydrogen peroxide. The final dicycloaliphatic epoxide was isolated by removing solvent at 95°C. under reduced pressure which has epoxy equivalent weight of 207.0 g/eq (yield 105.0 g).
