GB498242A - Improvements in the manufacture and production of butadiene - Google Patents

Abstract

Butadiene is obtained by reduction of vinylacetylene with alkali metal amalgam and substances developing hydrogen therewith such as water and/or alcohols. Vinylacetylene may be led into the amalgam mixed with water or led together with water vapour over anhydrous amalgam or liquid amalgam may react in countercurrent with a solution of vinylacetylene in an alcohol. Sodium, potassium, rubidium or mixed alkali amalgams may be used. Other metals especially thallium may be added, and electrolytes, e.g. secondary or mixtures of primary and secondary potassium phosphates, common salt, zinc or chromium salts, may be present in the reaction liquids. Carbon dioxide added to the vinylacetylene increases the speed of hydrogenation. Ordinary or elevated temperature, and any pressure may be employed. In examples: (1) vinylacetylene is led in a cycle through 2 per cent potassium amalgam and water, first at normal temperature then at 55 DEG C. The gas is liquefied and fractionally distilled to obtain butadiene; (2) vinylacetylene is shaken with 1,5 per cent rubidium amalgam and water at 20 DEG C. An amalgam containing 1 per cent potassium and 10 per cent thallium is used similarly; (3) 20 per cent caustic potash solution is continuously electrolyzed in presence of mercury containing 10 per cent of thallium, the amalgam formed being led through water containing vinylacetylene and returned. Butadiene-1,3 with some butadiene-1,2 is formed. Vinylacetylene containing acetaldehyde and diacetylene, made by treating electric are acetylene with cuprous and ammonium chloride solution, may be employed similarly; (4) the reaction liquid comprises an aqueous solution of zinc chloride and sodium butyl naphthalene sulphonate and, if desired, sodium hydroxide.ALSO:Alkali metal amalgams containing 2 per cent of sodium or potassium, or 1,5 per cent of rubidium, or 1 per cent of potassium and 10 per cent of thallium, are referred to.