Patent GB-804175-A (GB)
Title: A process for the production of hydrocarbon polymers
IPC: C08F10/00
Filed: 1955-07-12
Abstract: <PICT:0804175/IV (a)/1> <PICT:0804175/IV (a)/2> A polymerization process, preferably continuous, comprises passing an olefin and a solvent into a reaction zone containing a catalyst comprising chromium oxide, withdrawing a mixture comprising solid polymer, solvent and catalyst, heating the mixture at a temperature above that in the reaction zone (if desired in the presence of additional solvent) whereby maximum solution of polymer is obtained, and separating the catalyst.  The olefins specified are 1-olefins having a maximum chain length of 8 carbon atoms, e.g. ethylene, propylene, mixtures thereof, butene, pentene and heptene, and the solvents disclosed are butane, isobutane, pentane, isopentane, isooctane, paraffins and higher olefins.  In examples the chromium oxide catalyst used is supported on silica/alumina and may be recycled if necessary after regeneration and/or refortifying.  The polymerization temperature may be from 100 DEG  to 350 DEG  F., preferably in the lower range to favour production of high molecular weight flexible polymer, and the dissolution temperature is preferably at least 25 DEG  F. higher and may be from 250 DEG  to 400 DEG  F.  The catalyst may be separated by centrifuging, settling or filtering and the polymer recovered from solution by distillation, flashing or cooling. Fig. 1 illustrates a suspended catalyst system wherein olefin dissolved in solvent containing suspended catalyst is introduced via line 10 into reactor 11 and the reactor effluent is withdrawn via line 12 containing a heat exchanger, and preferably via line 37 and agitation zone 38, and is passed into separation zone 13 wherein catalyst is removed and may be recycled via lines 14 and 10. Additional hot solvent may be added through inlets 37A and 26.  The liquid phase fron zone 13 is cooled by heat exchanger 17 and passed to separation zone 18, the precipitated polymer being recovered through line 19.  The remaining liquid phase is passed into fractionator 21 and the recovered solvent recycled via lines 23 and 10.  Alternatively the reactor effluent can be passed via line 27 to liquid/solid separator 28 wherein catalyst/polymer slurry settles out and is passed via line 29 and in conjunction with solvent from line 35, into line 12 and thus processed as set out above.  The clarified liquid from separator 28 is passed through line 30 to fractionator 31 and polymer of relatively low molecular weight is recovered through outlet 36.  The solvent recovered from fractionator 31 is passed into separation zone 13 via lines 34 and/or 35.  Fig. 2 illustrates a fluidized catalyst bed system wherein ethylene enters at 40 and solvent at 41.  The solution obtained passes through screened inlet 43 into reactor 42, the lower part of which contains the catalyst in the form of a fluidized bed.  Catalyst fines are elutriated by the flow of hydrocarbon and passed through conduit 45 to fines removal zone 47 from which the fines may be withdrawn through conduit 48. Clarified hydrocarbon passes to fractionator 50 wherein solvent is recovered and passed via line 53 for recycling through conduit 44, or via conduits 60 and 57 for use as catalyst carrier.  Polymer is withdrawn through outlet 52.  Part of the reaction mixture from reactor 42 may be withdrawn through standpipe 46, conduit 54A and heat exchanger 58 and passed into the dissolution zone 59. Another part or all of the mixture may be passed into settler 55 from which the liquid passes through conduit 56 to the recovery system, and the catalyst/polymer slurry passes, in conjunction with recycled solvent from conduit 60, into the dissolution zone 59.  Polymer solution and catalyst from zone 59 may be passed into either of solids removal zones 62 or 70.  Catalyst may be withdrawn and recycled via conduit 44, or removed through outlet 44A, or passed to regeneration step through conduit 72.  Polymer solution may be passed through conduits 63 or 71, and 68 and 49 to fractionation zone 50, or alternatively to fractionation zone 64 in order to keep separate the relatively higher molecular weight polymer originally adhering to the catalyst.  The polymers produced may be granular and of molecular weight about 53,000 and may be moulded or extruded to form pipe, tubing, insulation material or lining for tanks.  Specification 790,195 is referred to.