| 摘要 |
Nitriles obtained by condensation of acetylene with ammonia or amines are saponified while in the vaporous state and while adding a vaporizable alcohol in the liquid or gaseous state and, if desired, oxygen. The alcohol may be vaporized by heating, for example, in the reaction vessel, or the alcohol vapours may be carried into the vessel by the nitrile vapours or by a current of gas, such as air. Readily volatile esters may be obtained in a concentrated form depending on the formation of azeotropic mixtures thereof with water and the alcohol, while with esters of high boiling point, it is preferable to work with excess of nitrile or alcohol over the equimolecular proportion, and, after separating the ester, to return the excess to the reaction vessel. The temperature of saponification is generally between 50 DEG and 250 DEG C. The alcohols used for the esterification, as for example methyl, ethyl or butyl alcohols, glycols, glycerol and the like, with or without the acids, may be led in counter-current to the nitrile vapours, but it is preferable to introduce the nitrile and the alcohol at the lower end of a tower while introducing excess of mineral acid at the top, the upper part of the tower being constructed as a dephlegmator. In the examples, (1) a mixture of 10 parts of the crude gas mixture containing acetylene and 1 part of ammonia is passed at 380 DEG C. over a catalyst containing zinc and chromium oxides with velocity of 110 litres per hour and per litre of catalyst. The nitrile is separated by adsorption in active carbon, then vaporized and mixed with approximately equal parts of air and ethyl alcohol vapour, and passed to the bottom of a column at 150 DEG C. An excess of 80 per cent sulphuric acid trickles down the column, and the temperature of the dephlegmator forming the upper part of the column is kept between 60 DEG and 80 DEG C. The product is a crude ethyl acetate of Sp. Gr. 0,92. (2) Butyl acetate is obtained by a process similar to that of example (1), or, by using ethylene glycol, a mixture of glycol mono-acetate with a little glycol di-acetate is obtained. Specifications 257,907, 264,143, 312,469, 313,877, 325,531, 332,258, and 339,235, [all in Class 2 (iii), Dyes &c.], are referred to. |
