Patent GB-587969-A (GB)
Title: Improvements in manufacture of halogenated hydrocarbons
IPC: C07C17/10
Filed: 1944-12-13
Abstract: <PICT:0587969/IV/1> A process for the chlorination of saturated hydrocarbons in the gaseous phase by means of cupric chloride, and in particular for the preparation of alkyl chlorides such as methyl chloride from natural gas, includes the steps comprising suspending an inert finely-divided porous solid impregnated with cupric chloride in a stream of the hydrocarbon at a temperature sufficient to bring about chlorination, for example, above 400 DEG  C., separating the impregnated powder now containing reduced cupric chloride from the gaseous stream and fractionating the gaseous product to recover chlorinated hydrocarbon.  An <PICT:0587969/IV/2> advantageous embodiment of the invention comprises a combined process wherein the reduced cupric chloride impregnated solid is suspended in a free oxygen-containing gas at a temperature sufficient to oxidise the copper chloride to copper oxychloride which is thereupon neutralized by suspending the impregnated solid in a gas stream comprising hydrogen chloride at a temperature sufficiently elevated to convert the oxychloride to cupric chloride and the now cupric chloride impregnated solid is recycled for the further chlorination of hydrocarbons; the oxidation and neutralization steps may be combined or carried out separately.  The reduced cupric chloride impregnated solid for the oxidation may be obtained from the chlorination step or may be prepared by heating a cupric chloride impregnated carrier at above 500 DEG  C.  Preferably, the cupric chloride impregnated solid contains also an alkali-metal chloride; thus there may be present an alkali metal chloride in amount from 20 to 50 moles. per cent of total impregnated chlorides whilst the carrier may be impregnated to the extent of 20 to 65 per cent of chlorides based on the total weight of the impregnated solid; suitable carriers, preferably 10 mesh to 10 microns in particle size, are natural clays such as attapulgus clay, kieselguhr, infusorial or fuller's earth, and porous synthetic gels such as alumina or silica gels. Referring to Fig. 1, preheated oxygen-containing gas, such as air, is passed through line 1, compressor 2 and line 3 to an injector at the base of standpipe 4 which delivers finely-divided natural clay impregnated with reduced cupric chloride and potassium chloride from chlorination tower 5, the impregnated solid being transferred in suspension (fluidised) via line 7 to an oxidation tower 8 maintained at 325 DEG  to 425 DEG  C. Additional air for the oxidation is supplied to the tower through line 11 from line 3.  A linear gas velocity of 0.25 to 5 feet per second maintains the impregnated powder in a fluidised state. Effluent gas leaves tower 8 by line 29 to cooler 30 and thence via line 31 to a cyclone-separator 32, wherein any suspended impregnated powder is separated and the effluent gas leaves the system through line 34. Oxidised powder in fluidised dense phase is picked up from the bottom of standpipe 24 by a hot stream of natural gas, introduced into the system via line 42, compressor 43, heat exchanger 44 and lines 45 and 46, and is delivered in suspension through line 47 to neutralization tower 52.  Hydrogen chloride is supplied to tower 52 via line 53 for the conversion of copper oxychloride to cupric chloride.  A temperature of between 325 DEG  C. to somewhat below 400 DEG  C. is employed in this stage though it may be 200 DEG  C. or even lower.  The cupric chloride enriched powder settles in standpipe 57 at the base of tower 52 and is delivered via valve 65 to a hydrocarbon stream of natural gas in line 45 whence it is transferred through line 66 to chlorination tower 5 maintained at 400 DEG  C., or lower, to 525 DEG  C.  Additional hydrocarbon is supplied to the tower via lines 42, 72 and 73, heat exchanger 74 and line 75.  The reduced impregnated powder settling in standpipe 4 is maintained fluidised by means of hydrogen chloride introduced through line 80 and is picked up by air in lines 3 and 7 and recycled to tower 8 as stated above, for oxidation to copper oxychloride.  An effluent gas stream comprising chlorinated hydrocarbon, unreacted hydrocarbon, and hydrogen chloride formed in the chlorination leaves chlorination tower 5 via line 86 passing through a cyclone separator 84, any impregnated powder being thus separated, the gas stream then passing by line 88, heat exchanger 74 and lines 62, 63 to neutralization tower 52 where the hydrogen chloride in the gas stream is used in the neutralization process.  The effluent gas stream from tower 52 which comprises mainly chlorinated hydrocarbon, unreacted hydrocarbon and water vapour is passed through separator 94, then via line 100, heat exchanger 44 and line 101 to another separator 102 where it meets a stream of gaseous hydrocarbon containing oxidised powder from lines 103 and 47, whereby residual hydrogen chloride and chlorine are removed from the effluent gas stream, the treated powder being transferred to tower 52 via line 104, and the purified effluent stream is passed from separator 102 via line 105 through condenser 110 and water separator 112, to packed tower absorber 120.  Here the gas stream of chlorinated and unreacted hydrocarbons is contacted countercurrently with a liquid stream of highly chlorinated hydrocarbon such as carbon tetrachloride, introduced via line 122, which removes the chlorinated hydrocarbons, unreacted hydrocarbon vapours being returned to the chlorination process via lines 134 and 42, and the enriched liquid absorbent is passed through line 123 to a fractionator 125, where chlorinated light hydrocarbons, such as methyl chloride, are removed as overheads via line 130, and chlorinated higher hydrocarbons removed as bottoms through line 131, part being returned, if desired, as absorbent in the absorber 120 by means of pump 121 in line 122. Instead of separating the products of the chlorination reaction in the neutralization tower as above, the products in line 62 may be compressed and cooled for fractionation of anhydrous hydrogen chloride, unreacted hydrocarbon and chlorinated hydrocarbon as shown in Fig. 2 described below, the hydrogen chloride being p  recycled to neutralization tower 52.  The reaction towers are normally operated at atmospheric pressures, but pressures up to 4 or 5 atmospheres may be used.  Referring to Fig. 2, wherein is shown an embodiment in which the oxidation and neutralization reactions are carried out in the same zone, an oxygen-containing gas is passed by means of compressor 200, heat exchanger 203 and line 204 to the base of chlorination tower 214 where it picks up reduced copper chloride-alkali metal chloride impregnated carrier which is transferred in suspension through line 208 to combination oxidation-neutralization reactor 209.  Hydrogen chloride enters the reactor at line 215 and oxidation and neutralization occurs simultaneously.  To regulate the temperature to a range of 325 DEG to 400 DEG  C., the impregnated carrier is circulated through a bank of multiple coolers represented by cooler 220.  The effluent gases from reactor 209 are passed through a separator 232 to remove any impregnated carrier present and thence through cooler 203 to separator 235 wherein hydrogen chloride in the effluent is removed by reaction with oxidised cuprous chloride impregnated carrier, the treated effluent leaving by line 250; the required impregnated carrier is prepared by feeding reduced cupric chloride-carrier from line 208 through line 240 to separator 241 wherein it is oxidised by air supplied from lines 244 and 245, the oxidised carrier being picked-up at the base at 247 and led to separator 235 by line 248. In the chlorination step, the oxidised-neutralized carrier supported chlorides from reactor 209 are picked up at the base 264 by means of a gaseous hydrocarbon stream introduced through line 260, compressor 261, heat-exchanger 262 and line 263 and passed to chlorination reactor 214 via line 265.  The reactor is maintained at about 400 DEG to 525 DEG  C., sufficient heat being supplied by means of heater 271; additional hydrocarbon is furnished by means of line 266 from feed line 263.  The reduced cupric chloride-carrier is treated as described above.  The gaseous effluent product from reactor 214 passes through a separator 276, heat-exchanger 262 and after further cooling, is compressed and delivered by line 285 to a high-pressure fractionator 290.  Unreacted hydrocarbon is passed from the fractionator through line 293 to line 260 for recycling, hydrogen chloride is removed as a side stream in line 294 and chlorinated hydrocarbons are withdrawn as bottoms.  The products may also be separated by treating with a high boiling chlorinated hydrocarbon to remove the chlorinated hydrocarbons and then removing the hydrogen chloride from unreacted hydrocarbons by water treatment.  In further modifications, inert carrier gases may be used for transference of the impregnated carriers between reaction zones in which case intermediate cyclone separators are used, and the powder fed from these separators to the reactors. In place of the reactors described above, there may be used elongated tubes, the reactant gases serving as carrier gases. Also one or all of the reactors may be operated at such lineal gas velocities that the whole of the impregnated powder is taken over - head.  Specifications 568,913 and 591,799 (as open to inspection under Sect. 91) are referred to.