GB496840A - Improvements in and apparatus for the manufacture and production of acetaldehyde - Google Patents

Abstract

<PICT:0496840/IV/1> In the production of acetaldehyde by hydrolysis of vinyl ethers, the reaction products are removed from the reaction mixture and the aldehyde is then separated from the alcohol in the presence of water, preferably acidified. The vinyl ether may be made from methyl alcohol and acetylene in the presence of a basic substance in the liquid phase in a tower as described in Specifications 369,297 and 430,764, hydrolysis being effected with dilute acid in a second tower from which the aldehyde, alcohol and steam pass to a third tower for separation. Alternatively the vinyl ether may be made in the gas phase as described in Specification 427,036. For the hydrolysis there may be used a strong inorganic acid such as chromic, phosphoric or sulphuric acid in very dilute solution. Or the hydrolysis may be effected in the gas phase with steam by passing over a porous carrier such as silica gel impregnated with the acid at 150 DEG C. In an example acetylene or gas containing it is passed into methanol containing caustic potash in a tower I at 160 DEG C. at 14-16 atmospheres pressure, methanol being supplied continuously at 1a. Vinyl methyl ether passes out through a dephlegmator 2 and is condensed and collected in a receiver 4 and passes thence to a column 6 at a lower pressure to remove dissolved gas and through a measuring device 9 to a tower II in which it bubbles through acidified water at 80 DEG C. Acetaldehyde, methanol, and water vapours pass to a distillation tower III which is also supplied with acidified water. Acetaldehyde passes out of the top of the tower III and aqueous methanol at the bottom; after neutralization of the acid it is concentrated and used again for the production of vinyl methyl ether.