| 摘要 |
Alkyl vinyl ethers are prepared by a process consisting of a first stage (Stage I) comprising contacting ethylene with a salt or co-ordination compound of palladium, in the presence of less than 5% by weight of the reaction medium of water and in the presence of acetate ions, molecular oxygen, a copper salt, acetic acid and 1,1-diacetoxyethane or 1,2-diacetoxyethane (the concentration of acetic acid in the process not exceeding 30% by weight of the reaction medium), separating a mixture comprising vinyl acetate, acetic acid and water, removing from said mixture at least some of the water by phase separation, and a second stage (Stage II) comprising contacting the remainder of the said separated mixture, containing vinyl acetate and acetic acid, with an aliphatic alcohol in the presence of a salt or co-ordination compound of palladium. Preferably in Stage I the concentration of acetic acid does not exceed 10% by weight of the reaction medium; the concentration of water does not exceed 1% by weight of the reaction medium; palladous chloride, palladous bromide or palladous acetate are used as the palladium salt, or lithium chloropalladite, sodium chloropalladite, or bis-(benzonitrile)-dichloropalladium II as the co-ordination compound in concentrations between 10-4 and 10-3 molar; halide ions may be present, in the form of an alkali metal chloride in concentrations up to 100 moles per mole of palladium compound, but in any case so that the total halide concentration does not exceed 0.2 molar; up to 1 mole (per litre of the reaction mixture) of nitrate, nitrite, nitrosyl, nitro or nitroso compound may be added, especially in the form of an alkali metal nitrate or nitric acid; acetate ions are provided by 0.1 to 0.5 moles of alkali metal or alkaline earth acetate per litre; the copper salt is copper acetate in concentrations between 0.05 and 0.3 molar; the reaction temperature is between 50 DEG C. and 180 DEG C.; ethylene and molecular oxygen are introduced as a gaseous mixture containing 3 to 10% of the latter; and an overall operating pressure of 20-34 atmospheres is maintained. The phase separation is suitably carried out at temperatures between 20 DEG C. and 50 DEG C. Preferably in stage II, the palladium compounds are as indicated in stage I in a similar concentration range; halide ions may be present in the form of an alkali metal bromide in concentrations up to 100 molar per mole of palladium compound, but in any case so that the total halide concentration does not exceed 0.2 molar; the redox system is present in the form of a copper salt, e.g. copper bromide; the reaction temperature is in the range -50 DEG C. to 200 DEG C.; the vinyl acetate and acetic acid mixture is introduced continuously; the aliphatic alcohols contain 1 to 6 carbon atoms, e.g. methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol; the vinyl acetate is present in excess; an inert solvent is present; a base is present, e.g. lithium acetate, at 0.1 to 2 times the molar concentration of the palladium compound; the concentration of the acetal, derived from the alcohol used in the process, is kept stationary at a level of up to 10% by weight of the reaction mixture, or up to 5% by weight, with up to 5% of water; the concentration of acetic acid is kept stationary at a level of up to 50% by weight of the reaction medium; the operating pressure is maintained between 0.1 and 1 atmosphere. |
