GB738171A - Process for the preparation of propylene chlorhydrin - Google Patents

Abstract

<PICT:0738171/IV (b)/1> A continuous process for preparing propylene chlorhydrin from water, chlorine and propylene is characterized by operation at a temperature below 60 DEG C., with a volume of propylene-containing gas of which a maximum of 50 per cent is consumed in the reaction, in an apparatus comprising two distinct superposed reaction zones; the first said zone for dissolving the chlorine in the propylene chlorhydrin aqueous solution, the second said zone for reacting the chlorine-containing solution with the propylene and piping connecting the top of the second zone with the bottom of the first zone, said apparatus affording gravitational recirculation of the chlorhydrin solution between both reaction zones in consequence of the buoyancy of both gases introduced and of the different densities of the gaseous dispersion in the reaction zones on the one hand and of the liquid in the recirculation piping on the other hand whereby the concentrations of free dissolved chlorine and of chlorine transformed into hypochlorous acid taken together and expressed as chlorine are maintained at a value lower than 0.5 gram per litre. An excess of propylene compared with the introduced chlorine may be employed or a diluent may be used, e.g. a paraffin hydrocarbon such as ethane, propane or the butanes usually accompanying propylene in the fraction of liquefied petroleum gases rich in this olefine or any other gas inert under the reaction conditions such as methane, hydrogen or nitrogen. The apparatus in the drawing is filled to the upper level of tube 10 with an aqueous solution containing propylene chlorhydrin whilst a stream of chlorine gas is introduced into column 1 through porous plate 2, with the formation of hypochlorous acid which reacts in column 3 with diluted propylene introduced through porous plate 4. The solution of propylene chlorhydrin is partially withdrawn through tubing 10 and partially recirculated through tubing 5, water being introduced at 6 at a rate corresponding to the rate of withdrawal through 10. The solution is recirculated through tubing 7 and adjustment device 8 to column 1. The residual gases are recovered at 9. In the examples: propylene chlorhydrin is produced using the above apparatus and as propylene containing starting material a mixture of propylene, propane and hydrocarbons having four carbon atoms (1); and a mixture of propylene, ethylene, ethane, propane and butanes. Specification 450,372 is referred to.