GB646919A - Method for improving drying and semi-drying oils - Google Patents

Abstract

Drying and semi-drying oils are modified to increase the proportion of conjugated double bonds by heating them at a temperature below that at which polymerization occurs in the presence of a nickel or cobalt catalyst containing a small amount of chemically bound sulphur. The temperature used varies from 170 DEG to 220 DEG C., preferably about 180 DEG C., whereas the polymerizing or bodying temperature is generally higher than 270 DEG C. The modified oil may be subsequently bodied by further heating, for example to 285 DEG C., either after filtration or in presence of the catalyst. In an example, refined linseed oil is heated with a catalyst consisting of 60 per cent nickel, 3 per cent sulphur, and 37 per cent kieselguhr, while carbon dioxide is conducted through it. Alternatively, a cobalt catalyst containing 5 per cent sulphur without a carrier may be used. Soya bean oil is similarly treated. Catalytic agents.-A catalyst for the above process may be prepared by precipitating nickel carbonate in the presence of kieselguhr from a solution of the sulphate by sodium carbonate solution at 80 DEG C. The washed and filtered product is boiled with dilute soda solution, washed, boiled with nickel sulphate solution, filtered without washing, and the dried powder reduced in a hydrogen stream at about 500 DEG C., whereby the nickel carbonate is reduced to nickel and the last-added nickel sulphate to nickel sulphide. The catalyst is pyrophoric and must be kept in oil. The preferred sulphur content is from 1-5 per cent, and other known carriers such as active carbon may be used.