| 摘要 |
Esters are prepared by passing the vapour of an alcohol into a molten mixture of a mono-carboxylic or dicarboxylic acid or an anhydride of such an acid which acid or anhydride is normally solid and has a melting point below 200 DEG C. with an esterification catalyst, e.g. potassium hydrogen sulphate, and drawing off the ester in vapourous form through a distillation column by maintaining a sub-atmospheric pressure above the melt, the melt being maintained at a sub-atmospheric pressure. The alcohol is passed through a conduit heated by being immersed in the acidic melt in such a way that the emerging vapour passes through the melt. When a dicarboxylic acid is used the diester passes through the distillation column, while the mono-ester condenses and is returned to the reaction zone. The ester is condensed and the water produced in the reaction is continually drawn off by the vacuum pump. Examples are given using specified apparatus wherein methyl laurate, dimethyl adipate, diethyl adipate, dimethyl succinate, dimethyl glutarate and dimethyl phthalate are prepared from the appropriate alcohol and acid or acid anhydride. |
