2-(1-propenyl-5-norbornene separation from piperylene dimers by complexing with copper, silver, gold or mercury compound
United States Patent [1 1 [111 3,875,251 Ellis et al. Apr. 1, 1975 2-( l-PROPENYL-S-NORBORNENE [51] Int. Cl. C07c 13/28 SEPARATION FROM PIPERYLENE DIMERS BY COMPLEXING WITH COPPER, SILVER, GOLD OR MERCURY COMPOUND Inventors: James Morgan Hunter Ellis; Paul l-lepworth; Pannalal Sohanlal Jhawar, all of Stockton-on-Tees,  
 England Assignee: Imperial Chemical Industries Ltd.,  
 London, England Filed: Feb. 19, 1974 Appl. No.: 443,769  
 Foreign Application Priority Data Feb. 21. 1973 United Kingdom 8492/73 US. Cl. 260/666 PY, 260/6815 C [58]Field. of Search...260/&#39;666 PY, 681.5 R, 681.5 C  
 Primary E.\aminerVeronica OKeefe Attorney, Agent, or F irmCushman. Darby &amp; Cushman [57] ABSTRACT 2-( l-propenyl)-5-norb0rnene is separated from piperylene dimers by complex formation with a compound of copper, silver, gold or mercury.  
 8 Claims, No Drawings 2-(l-PROPENYL-S-NORBORNENE SEPARATION FROM PIPERYLENE DIMERS BY COMPLEXING WITH COPPER, SILVER, GOLD OR MERCURY COMPOUND The present invention relates to a separation process, in particular to the separation of 2- -(l-propenyl)-- norbornene from piperylene dimers.  
  2-( l-propenyl)-5-norbornene (PNB) is a bridged ring compound of structure CH=CII-CH3 (b.pt. 169C at 1 at.) and is a useful termonomer in co-called EPDM rubbers in which it is copolymerised with ethylene and propylene. The synthesis of PNB involves the condensation of piperylene with cyclopentadiene and as well as the desired product there are obtained coproduct dicyclo- ,pentadiene (DCPD) and piperylene dimers boiling in the range 140 to 180C. (There are some 16 isomeric piperylene dimers, the principle isomers being The separation of the PNB and piperylene dimers may be carried out by distillation but it involves a considerable capital outlay in a number of multiplate distillation columns. The present invention replaces at least some of the distillation stages by an extraction process and in so doing reduces the cost of production of PNB.  
  Accordingly the invention is a process for the separation of 2-(1-propenyl)-5-norbornene from a mixture containing 2-( l-propenyl)-5-norbornene and piperylene dimers in which a. the mixture is contacted with a compound of copper. silver, gold or mercury so as to form a complex between the 2-( l-propenyl)-5-norbornene and the metal compound,  
 b. the complex is separated from the piperylene dimers and.  
 c. the complex isdecomposed 2-( l-propenyl)-5-norbornene.  
  The compound of copper, silver. gold or mercury which is used in the process is preferably a simple salt such as a halide, e.g. chloride, a carboxylate e.g. derived from a C to C alkanoic acid or a nitrate. Copper is the preferred metal and cuprous chloride has proved to be. a suitable complex forming compound.  
  The metal compound may be used in solution, particularly in aqueous solution which forms a two phase system with the hydrocarbon mixture being extracted. The PNB/metal compound complex passes into the aqueous phase and the PNB is recovered therefrom by suitable means such as by heating, eg with steam, up to 200C if necessary under pressure. Alternatively the metal compound maybe used in solid form in which case the hydrocarbon mixture being extracted is slurried with the solid metal compound, the complex when it is formed also being a solid and being capable of separation from the uncomplexed hydrocarbon by filtration, decantation etc.  
  The conditions under which the metal compound is contacted with the PNB/piperylene dimers mixture varies depending on the metal compound to be used. Both PNB and piperylene dimers are capable of forming complexes with the metal compound but we have found that the complexes have different stabilities. Piperylene dimers form less stable complexes than does PNB so the conditions should be chosen such that the PNB complex is stable whereas the piperylene dimers complex is not. For example, if cuprous chloride is the complexing agent the complex should be formed at 20 to 50C. For other metal compounds this temperature may differ although for practical purposes a metal compound should be chosen which can be used in the range l00 to +C.  
  The concentration of metal compound used should preferably be such as to provide one mole per mole of PNB to be extracted. If desired a diluent may be added to the hydrocarbon mixture to facilitate the extraction although in many cases the volume of uncomplexed piperylene dimers provides sufficient diluent. If a diluent is used it may suitably be a hydrocarbon particularly a paraffin. The exact diluent may be chosen by reference to the temperature required for the formation of the complex. For instance if the complex is to be formed at 30 to 40C then a 30/40 petroleum ether (comprising predominantly pentanes) may be used and allowed to reflux during the exothermic complex formation so maintaining the desired temperature. If higher temperatures are required then a higher boiling diluent, e.g. a heptane mixture may be used. The metal compound should be agitated with the PNB/piperylene dimers mixture so as to provide as effective contact as possible between the PNB and the metal compound.  
  The separation of the metal complex from the piperylene dimers is made by a phase separation either liquid from liquid or solid from liquid. If desired the separated complex either in solid form or in solution may be purifled by washing with a solvent such as an alkane to remove final traces of piperylene dimers.  
  The complex is preferably decomposed by heating at an elevated temperature, e.g. up to 250C, when the PNB is released. The complex may be heated as a solid or in solution or in suspension in a high boiling diluent.  
  The process of the present invention is particularly suitable for combination with the process described in our British Pat. No. 1,297,081 (US. Application Ser. No. 136,547). The latter process involves the production of a mixture of olefines containing PNB by:  
 a. distilling a pyrolysis gasoline fraction derived from a cracked hydrocarbon feedstock to produce a distillate boiling in the range 10 to 80C and comprising piperylene and isoprene,  
 b. redistilling this distillate to produce an isoprene concentrate&#34; and a piperylene concentrate, and  
 c. heating the piperylene concentrate at a temperature in the range to 250C to produce a mixture containing predominantly PNB, DCPD and piperylene dimers, but also including some unchanged C hydrocarbons and higher polymers of CPD, i.e. hydrocarbons containing 15 carbon atoms.  
  The isoprene concentrate produced in the process of British Pat. No. 1,297,081 suitably boils in the range to 40C and comprises isoprene and the lower boiling hydrocarbons of the fraction boiling in the range 10 to 80C while the piperylene concentrate comprises piperylene and the higher boiling hydrocarbons of this fraction.  
  The product from stage (c) may, if desired, be used as a termonomer after removing the C and C hydrocarbons, i.e. as a mixture of PNB (50 wt.7c) piperylene dimers and DCPD. Alternatively and preferably some further refinement of the mixture is carried out to increase its PNB content and to reduce its piperylene dimers content. To carry out this refinement by distillation involves the use of at least three more distillation columns after the first distillation in which the C hydrocarbons are removed. The use of the process of the present invention enables a reduction to be made in this number and in particular it eliminates the distillation stages requiring the largest number of plates.  
 EXAMPLES 2 (1-15) The following examples were carried out using the 1 basic technique described in Example 1. Individual variations are noted in the following Table of results. In each case the complex was decomposed by heating at 126C. 2% based on the weight of hydrocarbon feed of methanol was added to facilitate the complex formation. This effect could equally as well have been achieved with any lower (C to C alkanol.  
  F d Product Composition* &#39;/1 Pet Composition Example P1P ether Wt.  
 No. PNB Dimers DCPD /40 CuClg feed g PNB Dimcrs DCPD &#34;The complex was slurried in silicone-oil for decomposition The (&#39;uCl was reused from the previous experiment w-Solid (u(&#39;l added to the hydrocarbon Thus the mixture from stage (c) of the process described in British Pat. No. 1,297,081 may be initially subjected to a distillation step in which unreacted C hydrocarbons are removed as a distillate boiling up to 80C. The residue from the distillation may be then submitted to the process of the present invention, e.g. by agitation with solid cuprous chloride at 20 to C. The complex formed may be removed and decomposed as described earlier in this specification. Alternatively, the residue remaining after the C removal may be subjected to a second distillation in which C hydrocarbons are removed as residue and the PNB, piperylene dimers and DCPD as distillate (boiling at 140 to 190C). This distillate is then treated by the process according to the present invention by means of which some DCPD is removed as well as the piperylene dimers.  
  The invention will now be further described by reference to the following examples.  
 EXAMPLE 1 A mixture comprising wt.7r PNB, l5 wt.7z piperyl- 65 We claim:  
  1. In a process for the separation of 2-( l-propeny1)- 5-norbornene from a mixture containing 2-( l-propenyl)-5-norbornene and piperylene dimers as hereinbefore defined the steps of a. contacting the mixture with a compound ofa metal selected from the group consisting of copper, silver, gold and mercury so as to form a complex between the 2-( l-propenyl)-5-norbornene and the metal compound.  
 b. separating said complex from the piperylene dimers and,  
  decomposing said complex 2-( 1-propenyl)-5-norbornene.  
  2. The process of claim 1 in which said compound of said metal is a halide, a carboxylate or a nitrate.  
  3. The process of claim 1 in which the temperature in step (a) is l00 to +C.  
  4. The process of claim 3 in which the metal compound is cuprous chloride and the temperature 20 to 50C.  
  5. The process of claim 1 in which the concentration of said metal compound in step (a) is such as to provide about one mole for each mole of 2-(l-propenyl)-5- norbornene in the mixture.  
 c. to recover kanoic acid at 20 to 50C and in a concentration of about 1 mole copper salt for each mole of 2-(l-propenyl)-5-norbornene in the mixture and the aqueous solution of the complex is separated from the residual organic phase and the aqueous solution heated at a temperature up to 250C to recover said