Process for the preparation of oximes

In the conversion of ketones to oximes using hydroxylamine sulphate in a cyclic process, the sulphuric acid formed is neutralised by means of a metal oxide or metal hydroxide with the formation of a metal sulphate which is readily thermodegradable. The metal sulphate is cleaved thermally to give metal oxide and sulphur dioxide. These two cleavage products are recirculated to the cyclic process (after the sulphur dioxide has been converted into sulphuric acid). This process avoids the production of by-products which can only be utilised to a very small extent, such as ammonium sulphate, which means that the process is environmentally friendly.