Patent GB-812139-A (GB)
Title: Improvements in or relating to process for the production of solid polymers of ethylene and other olefin polymers
IPC: C08F110/02
Filed: 1955-06-22
Abstract: Polymers of ethylene and olefines with a higher molecular weight than ethylene, are prepared by introducing a stream of olefine-containing hydrocarbon gases through a sequence of polymerization zones in which the predominant reactions are respectively, the polymerization of ethylene, and the polymerization of the said olefines having a molecular weight higher than ethylene.  The ethylene is freed from impurities by selective absorption of the ethylene in a nonreactive liquid hydrocarbon solvent, e.g. isooctane, propane, butane and n-iso-pentane, which is liquid, inert and non-deleterious under the ethylene polymerization conditions.  The gases which may be in a stream obtained by cracking hydrocarbons, and may contain ethylene, hydrogen, acetylene and propylene, are hydrogenated with the aid of a catalyst such as palladium or nickel sulphide to convert the acetylene to ethylene and are contacted with the solvent to selectively absorb the ethylene and the enriched solvent is passed to a polymerization zone to form a tacky, semi-solid or solid polymer. The stream may first be subjected to conditions to polymerize the propylene, e.g. by heating in the presence of a phosphoric acid polymerization catalyst, the product removed, the gas-stream absorbed in the non-reactive solvent and passed to the ethylene polymerization zone, or alternatively the ethylene and propylene may be absorbed in the hydrocarbon solvent and the enriched solvent subjected to propylene polymerization conditions and then to ethylene polymerization conditions for example by contacting with a chromium oxide catalyst at between 225 DEG  to 350 DEG  F. and a pressure between 350 to 400 p.s.i.g., with a concentration of ethylene in the iso-octane solvent of from 1 to 5 per cent of the total mixture.  In an example, an ethane feed containing 95 per cent ethane with methane and propane is cracked at 1500 DEG  F. and 5 p.s.i.g., reacted with a nickel sulphide catalyst at 400 DEG  F. and 50 p.s.i.g., and passed over a phosphoric acid catalyst for the polymerization of propylene which is removed by a mineral oil, and contacted with iso-octane at 300 p.s.i.g. at 0 DEG  F.  The solution is passed, together with recycle ethylene, to a polymerization zone containing chromium oxide and reacted at 300 DEG  F. and 400 p.s.i.g.  The effluent is flashed and the polymer and solvent separated and ethylene recycled.  The catalysts may be of the fixed or moving bed types or be present as a slurry and regenerated if required.  Processes are described; Fig. 1, in which thermally cracked propane is selectively hydrogenerated, zone 3, propylene polymerized, zone 4, scrubbed of polymer, 5, and the ethylene absorbed in iso-octane, 8, the solution is fed to a chromium oxide-alumina-silica catalyst in zone 10, the polymerized ethylene unreacted hydrocarbons and iso-octane separated in zone 11, and recovered iso-octane recycled to absorber 8; Fig. 2 in which an acetylene free gas stream is selectively absorbed, zone 20, in iso-octane, the solution polymerized with a phosphoric acid catalyst and with polypropylene polymerization conditions, zone 22, and then under polyethylene conditions 23, the product flashed 24, pure polyethylene removed and the vapour fractionated 26 and 27.  The recovered iso-octane re <PICT:0812139/IV (a)/1> <PICT:0812139/IV (a)/2> <PICT:0812139/IV (a)/3> <PICT:0812139/IV (a)/4> <PICT:0812139/IV (a)/5> cycled to absorber, and polymer containing compounds having twelve or more carbon atoms to the molecule removed at the bottom of fractionator 26, and propylene dimer and unreacted gases removed at overhead of fractionator 27; Fig. 3, in which gases are pyrolysed in furnace 30 acetylene removed 32, and the propylene polymerized in zone 33 and the polymer removed in zone 34.  The ethylene is absorbed in zone 35 at a pressure of 50-400 p.s.i.g. and from 0 DEG  to 125 DEG  F., and polymerized in zone 36 at about 300 DEG  F. and 400 pounds p.s.i.g.  The polymer is separated in flash chamber 39, and fractioned in 40 and the gas separated in 41, and the non-condensed gases are compressed and recycled to absorber 35.  In the process according to Fig. 4, the gas recovery process of Fig. 3 is applied to the process according to Fig. 2 and the recycle gases are heated or cooled as required.  In the process according to Fig. 5, the gas stream is absorbed in iso-octane and polymerized in reactors 69 and 71, stripped and the removed ethylene which is at high pressure recycled to between zones 69 and 71, and the desired concentration of ethylene in conduit 67 maintained by the addition of solvent or ethylene.