PROCESS FOR PREPARING AN EXTREMELY PURE DIMETHYL ETHER

When ultrapure dimethyl ether of aerosol quality is prepared, the use of low-pressure methanol frequently results in malodour, caused by amines. It is therefore desired to prepare a product of stable, odour-free quality starting from methanol dehydration products of varying composition by means of a simple distillation technology. After the dehydration step and after feeding the dehydration product to a distillation system, the abovementioned object is achieved by removing, from a 1st column, a light-ends fraction of 0.5 to 5% by weight based on the column inlet product, as head product, a washing fluid composed of the bottom product of a 2nd column which contains, besides methanol and water, a series of higher-boiling impurities, being applied above the inlet plate of this 1st column, and separating, in the 2nd column to which the bottom product from the 1st column is fed, the ultrapure dimethyl ether at the top from the higher-boiling components at the bottom.