GB484660A - Improvements in the manufacture and production of unsaturated hydrocarbons - Google Patents

Abstract

Unsaturated hydrocarbons are prepared by splitting hydrogen halide from aliphatic or cyclo-aliphatic halogenated hydrocarbons containing at least 3 carbon atoms and at least 1 halogen atom by bringing them into contact with a glowing electrically heated body for a period of less than 1 second, e.g. 0,01 sec. or less, and rapidly cooling the products. Initial compounds mentioned are dichlor- or dibrompropanes or butanes, di- or trichlor-pentanes or cyclohexanes, or those containing olefinic linkages. A metal wire or rod of silicon carbide may be electrically heated to 700-900 DEG C. and dipped into the liquid compound which boils vigorously and moves at great speed past the wire or rod. The products are quenched by the body of liquid, the quenching temperature being determined by its boiling point and therefore regulatable by varying the pressure. Alternatively, the compound may be blown in vapour form through glowing spirals or grids, the reaction gases being immediately quenched. The heated bodies may be of metals such as alloys of chromium with nickel or iron, or of lustrous or graphitic carbon or graphite. Increased or reduced pressure may be used and inert gases or vapours may be present. In examples: (1) a glowing wire spiral is dipped into a dichlorbutane, the time of contact with the flowing liquid being about 0,1 sec. The reaction gases pass through a reflux condenser and are then treated with alkali. They contain butadiene and some butane and butene; (2) dichlorbutane vapour at 300 DEG C. is led over a graphite rod heated electromagnetically to red heat. The contact time is about 0,1 sec. Butadiene is the main product. Three heated silicon carbide rods may be employed similarly; (3) dichlorpropane is treated as in (1) yielding a mixture of hydrocarbons including mono- and diolefines; (4) butenyl chloride heated to 250 DEG C. is led over a glowing silicon carbide rod to give butadiene.