Abstract:
A SPENT COPPER CHROMITE HYDROGENATION CATALYST IS RESTORED TO A CATALYTICALLY ACTIVE CONDITION BY A PROCESS WHICH COMPRISES (A) WASHING ORGANIC MATERIALS THEREFROM WITH A VOLATILE SOLVENT, (B) DRYING THE WASHED CATALYST TO REMOVE THE VOLATILE SOLVENT THEREFROM, AND (C) HEATING THE WASHED, DRIED CATALYST IN AN ATMOSPHERE COMPRISING MOLECULAR OXYGEN AT A CONTROLLED TEMPERATURE.
Abstract:
In a process for producing a derivative such as vinyl acetate from an olefin such as ethylene in the presence of a catalyst comprising a noble metal ion, an alkali metal acetate, and a redox agent comprising a copper (II) salt, in the course of which a portion of the copper (II) is deactivated by side reactions in which it is converted to copper oxalate which is then regenerated to an active form by treatment with hydrochloric acid at an elevated temperature, the treated liquid containing the regenerated catalyst tends to contain volatile organic chlorides (e.g. chloroform) which, upon recycle to the olefin reaction zone, tend to contaminate the product (e.g. vinyl acetate). Removal of these impurities from vinyl acetate by distillation is difficult if not impossible when a very high purity vinyl acetate is desired. The invention consists of removing these volatile chlorides, by vaporization processes, from the regenerated catalyst-containing liquid before it is returned to the olefin reaction zone. In a particular embodiment, the vaporization comprises stripping with a fixed gas containing molecular oxygen, whereby the catalyst is returned in a highly oxidized state to the olefin reaction zone.