GB1002105A - Improvements in and relating to carbonylation processes - Google Patents

Abstract

Olefins are recovered in a carbonylation process for the preparation of aldehydes or alcohols from olefins in which a volatile fraction containing unreacted olefins is separated from the product, treated for the removal of alcohols, and contacted with an aqueous solution of silver fluoborate or silver fluosilicate, and thereafter recovering the olefin from the said aqueous solution; the olefin extraction step preferably involves a liquid liquid phase separation of the aqueous extraction solution in the organic volatile fraction. It is preferred to operate one or more of the steps of separation of the volatile fraction, extraction of the olefins from the volatile fraction, and recovery of olefins from the extract continuously. Non-olefinic material in the aqueous extracting solution is preferably removed therefrom before the olefins are recovered from it, for example by contacting with an immiscible organic solvent saturated with the olefin to be extracted, which olefin may be obtained from a subsequent re-generation stage. Advantageously the organic solvent used in the purification step is paraffinic fraction differing in boiling range from the olefin. The recovery of the olefin is preferably effected by contacting the extracting solution with an immiscible organic solvent which advantageously has a different boiling range from the olefin to be recovered by 30-40 DEG C., the paraffin being the less volatile. The recovered olefin may be recycled to the carbonylation stage and the regenerated aqueous solution may be returned to the extraction stage. Hydrogen peroxide may be added to the aqueous solution of silver fluoborate or silver fluosilicate containing preferably at least 600 grams of silver per litre of solution. In the particular description the light ends resulting from the carbonylation of a mixture of C6 to C8 olefins after alcohol removal contained about 40% by weight of olefins and these were contacted at substantially atmospheric pressure and 0 DEG C. with aqueous solution of silver fluoborate in a continuous counter-current extraction system comprising three columns in series each column being equivalent to one theoretical plate. The olefins were recovered from the silver solution by steam stripping, the silver solution having been heated to about 60 DEG C. and the condensate from this steam stripping operation separated into two layers, the top hydrocarbon layer being separated. In another embodiment of the invention the silver fluoborate containing the hydrocarbons is contacted counter-current with a stream of high-boiling paraffin saturated with a portion of the olefin recovered from the subsequent olefin recovery prior to actual olefin recovery.