GB779388A - Process for demetalling hydroformylation stage products - Google Patents

Abstract

At least one metal carbonyl is removed from the hydroformylation products, obtained by the reaction of an olefine with hydrogen and carbon monoxide in the presence of a metallic hydroformylation catalyst by passing the products, initially at a temperature below the decomposition temperature of the metal carbonyl with the lowest decomposition temperature, downwardly from the upper portion of an elongated separation zone containing packing material, passing steam upwardly from a point in the lower portion of the zone, passing inert gas upwardly from at least one point above the entry of the steam to cause cooling and condensation of the steam by contact with the hydroformulation products, the amount and pressure of the steam and of the inert gas being adjusted to heat the hydroformylation products at least to the decomposition temperature of the metal carbonyl with the lowest decomposition temperature so that at least one metal is deposited on the packing material. In addition to the carbonyl formed from the metallic catalyst there may also be present in the hydroformylation product carbonyls of iron, nickel, chromium and molybdenum formed from the iron alloys used in the construction of the apparatus. Cobalt carbonyl may be decomposed at a temperature in the range 74 DEG to 100 DEG C. and the other carbonyls at temperatures in the range 171 DEG to 216 DEG C. If more than one metal is deposited the one of the carbonyl with the lowest decomposition temperature will be deposited nearest the top of the separation zone. Suitable inert gases for use in the separation are, for example, hydrogen nitrogen, methane and natural gas. Preferably the steam and inert gas are introduced at several points in the zone. The hydroformylation products fed into the separation zone may contain dissolved synthesis gas or may have it removed beforehand. In the example a mixture of carbon monoxide, hydrogen and olefines with cobalt 2-ethyl-hexanoate as catalyst is subjected to elevated temperature and pressure; a liquid phase containing aldehydes and carbonyls of cobalt of and of alloying metals such as iron, chromium, nickel and molybdenum is separated and passed to a demetalling tower, packed with pumice, where it is heated from an initial temperature of 38 DEG C. to a final temperature of 171-216 DEG C. by means of steam and inert gas; cobalt is deposited on the pumice near the top of the tower and other metals further down; cobalt may be recovered from the pumice by treatment with a dilute acid solution and used to make the 2-ethyl-hexanoate or other salt for use as catalyst in the carbonylation step.