Patented Oct. 7, 1952 2,613,231 UNITED STATES PATENT OFFICE 2,613,23i PREPARATION of CYCLooCTATETRAENE Alfred J. Canale, Moorestown, and John F. Kin caid, Mount Holly, N.J., assignors to Rohm & in Haas Company, Philadelphia, Pa., a corporation. of Delaware. No Drawing. Application March 9, 1950, Serial No. 148,734 4 Claims. (CI. 260-666) 1 . 2 This invention deals with the preparation of monocyanide is taken in an amount which is one cyclooctatetraene by tetramerizing acetylene in fifth of the weight of nickelous cyanide, the rate the presence of nickel monocyanide, NiCN, as is 60 grams per liter-hour. catalyst...... Solvents which are useful for wetting and sus It was discovered by Reppe and coworkers that pending the nickel monocyanide include not only cycloctatetraene is formed when acetylene is dioxane and tetrahydrofurane which have been heated in the presence of nickelous cyanide, mentioned but also water-miscible diethers of Ni(CN)2, suspended in tetrahydrofurane in the glycols, such as the dimethyl ethers of ethylene presence of calcium carbide or ethylene oxide. glycol, diethylene glycol, triethylene glycol, tetra Great stress was placed upon the necessity of an 10 ethylene glycol, propylene glycol, or dipropylene hydrous conditions. The reaction as carried out glycol, diethyl ethers of these glycols, mixed meth was slow, not particularly efficient in time or ma yl and ethyl ethers thereof, and mixtures of terials, and not truly reproducible. For the prac the various diethers. Another type of ether com tical preparation of cyclooctatetraene it is al prises acetals, such as dibutyl acetal, dipropyl most essential that shortcomings and difficulties 15 acetal, diethyl-formal, dibutyl formal, etc. of the art be corrected or avoided. ; : To the mixture of nickel monocyanide and sol We have found that: cyclooctatetraene is vent there may be added pulverized calcium car formed at a relatively rapid rate and in a repro bide. An amount from 0.5 gram to 5 grams per ducible manner by tetramerizing acetylene., at 100 parts of solvent provides a satisfactory range. 100 to 600 p.s. i. by heating it in the presence of 20 The calcium carbide reacts with any water which nickel monocyanide at 90° to 150°C., preferably may be present in the nickel monocyanide after between 10 and 150 C. The nickel monocya Solvent has been added thereto. The calcium nide is wet with a water-miscible organic Solvent hydroxide which then results can take up any such as dioxane or tetrahydrofurane, and may trace of acid which might have been left in the be mixed therewith in amounts of 0.1 part by catalyst. The use of calcium carbide thus per weight to 20 parts per 100 parts of the Solvent. mits a less critical washing of the nickel monocy In a preferred method nickel monocyanide is anide and displacement of water by solvent. Aft prepared from K2Ni(CN)4 or Na2Ni(CN)4 by re er thorough washing with water and repeated duction with potassium or Sodium metal in liquid rinsing with solvent the use of calcium carbide ammonia. A red precipitate, KaNi(CN)3 or the is not essential even though there appears to be comparable sodium salt, is formed and is sepa Some slight advantage in ensuring alkalinity, as rated. The precipitate is dissolved in a minimum by its use. amount of air-free Water and this solution is Acetylene is used under pressures of 100 to 600 poured with vigorous agitation into cooled (0°-15 pounds per Square inch. The reaction is desir C.) hydrochloric acid about 5 normal in strength. .35 ably initiated at the lowest practical pressure A precipitate of NiCN is formed and is sepa and then the pressure may be increased. A range rated, as by centrifuging. The Solid is washed of 300 to 500 pounds per square inch for the par until free of acid. With dealerated Water which tial pressure of the acetylene is preferred. Pre is then displaced with a water-miscible solvent. cautions for handling acetylene have ben de Dioxane, tetrahydrofurane, and other Water-mis 40 Scribed at length in the art. Essential precau cible anhydrous organic solvents, which are also tions include use of narrow tubes and/or dilution useful as solvents in the tetramerization reaction, withinert gas or vapor. are examples of solvents suitable for this purpose. In carrying out the tetramerization of acetyl When the nickel monocyanide is used imme ene a pressure vesselinust be used. It is charged diately after preparation, there is no induction 45 With a mixture of catalyst and solvent. The ves period for formation of cycloocctatetraene. Sel is Swept out with an inert gas such as nitrogen When the catalyst is "aged,' a short induction to displace air. The inert gas may be displaced period is usually observed. With nickel monocy with acetylene before or after heating. The anide as catalyst, the rate of tetramerization is charge of catalyst and solvent is heated to 90o many times that experienced with Ni(CN)2. For to 160° C. and acetylene is run in slowly at grad instance, With nickelous cyanide under condi ually increasing pressure. It is desirable to ini tions of the art 4 to 5 grams per liter-hour was tiate the reaction at a relatively low pressure. found to be the rate of tetramerization. When Too rapid application of pressure may sometimes nickel monocyanide is used at 115° C. under oth cause an explosion. After reaction has started, erwise similar conditions except that the nickel 55 pressure can be increased. Acetylene is pressured 2,618,281 3 4. in until the rate of reaction falls off or becomes troduction from time to time of acetylene at negligible. The vessel is then cooled and vented. 500 p.s. i. After 2.5 hours the reaction was in The reaction mixture is placed in a still and terrupted by cooling the bomb to 25° C. and distilled at low pressure. The distillate is washed venting the acetylene. The reaction mixture with water to remove water-miscible Solvent, was distilled at one mm. pressure. No polymeric dried, and fractionally distilled. Pure cycloocta by-products were here obtained as residue. The tetraene is thus obtained, boiling at about 143°C. distillate was washed with water, separated, Further details of the preparation of cyclo dried, and fractionally distilled. There were ob octatetraene by the method of this invention ... tained 9 grams of cyclooctatetraene and 2.5 will be found in the following illustrative ex 10. grams of benzene. aimples: - . The above examples illustrate typical pro . . . . cedures for preparing cyclooctatetraene by the Eacample 1 r...... process of this invention. The process is chair A slurry Was prepared from 0.5 part by weight - acterized by positive, dependable production of of freshly prepared nickel monocyanide, 5 parts 5 the desired product. It depends upon contact of pulverized calcium carbide and 100 parts of ing acetylene under pressure with nickel mono anhydrous dioxane. This slurry was placed in cyanide between 90° and 160° C., preferably in a high pressure rocker bomb which was sealed, the presence of a high boiling, water-miscible swept with nitrogen, and heated to 115° C. anhydrous solvent. The ether solvents are par Acetylene was slowly admitted. Gas absorption 20 ticularly desirable. Calcium carbide may be began immediately. Gradually the pressure of added to ensure an anhydrous state and react acetylene was raised to 500 p. S. i. and main with any acid which might have been left in tained between 300 and 500 p.s. i. by Occasional the nickel monocyanide catalyst. When the introduction of acetylene. The acetylene was catalyst has been stored under Water prior to taken from a cylinder, passed over activated 25 its use, there appears to be little tendency for charcoal to remove acetone vapors, and over the formation of polymeric residues. activated alumina, compressed, and run into the ... We claim: bomb as needed. After two hours the prepara : 1. A process for preparing cyclooctatetetraene tion was discontinued. The bomb was cooled which comprises tetramerizing acetylene by con and the acetylene vented. The reaction mix 30 tacting it with nickel monocyanide at 90° to ture was distilled at one mm. pressure. The 150° C. under a pressure of 100 to 600 pounds per distillate was Washed with Water to remove di square inch. oxane. The organic layer was separated, dried 2. A process for preparing cyclooctatetraene over calcium chloride, and distilled. There were which comprises tetramerizing acetylene by con obtained 6 parts by weight of benzene and 14 35 tacting it with nickel monocyanide in the pres parts of cyclooctatetraene. Some polymeric ma ence of a high boiling Water-miscible anhydrous terial was obtained as a residue in the first dis organic solvent at 110° to 150° C. under a pres tillation. . Sure of 300 to 500 pounds per square inch. 3. A process for preparing cyclooctatetraene Eacample 2 which comprises tetramerizing acetylene by con Nickel monocyanide was prepared by dissolv tacting it with nickel monocyanide in the pres ing 6.7 grams of K2Ni(CN)4 in 400 ml. of liquid ence of calcium carbide and of a high boiling amIlonia, adding 0.5 gram of metallic potassium water-miscible anhydrous organic solvent at 110 in small portions to form a red precipitate, de to 150° C. under a pressure of up to 500 pounds canting off the ammonia, taking up the red per square inch. precipitate of K2Ni(CN)3 in water which had been 4. A process for preparing cyclooctatetraene boiled to free it of air, acidifying the resulting which comprises tetramerizing acetylene by con solution with 5 N hydrochloric acid, cooled to tacting it with a nickel monocyanide catalyst in 15° C., and separating and Washing the resulting the presence of calcium carbide and of a high NiCN with deaerated water. While this prod 50 boiling water-miscible anhydrous ether solvent uct could have been used as in Example l; it at 110° C. to 150° C. under an acetylene pressure Was Stored under Water for 20 hours before use. of 300 to 500 pounds per square inch, the said The water was decanted from the nickel mono catalyst having been stored under water prior cyanide which was then washed several times to its use into the reaction mixture. with dioxane. . . . . 55 ALERED J. CANAL.E. A slurry was made with 0.5 gram of the "aged' nickel monocyanide, 5 grams of pulverized cal JOHN F. KINCAID. cium carbide, and 100 parts of anhydrous di oxane. The slurry Was placed in a high pres REFERENCEs CITED sure rocker bomb, which was sealed, swept out The following references are of record in the with nitrogen, and heated to 115° C. Acetylene file of this patent: was slowly run into the bomb to a preSSure of Polymerization of Acetylene to Cyclooctatetra 500 p.s. i. After about 20 minutes the tempera ene by K. Kammermeyer, Fiat Final Report No. ture of the charge began to rise, indicating that 967, Feb. 28, 1947, pages 1-9 and 33-37. an exothermic reaction had started. Acetylene 65 Cyanogen Compounds by H. F. Williams, Ed absorption began at this time. The pressure was ward Arnold and Company, London, 2nd edition, maintained between 300 and 500 p., S. i. by in pages 141 and 142.