Patent GB-821404-A (GB)
Title: Preparation of meta-and para-xylylenediamines
IPC: C07C209/48
Filed: 1958-02-24
Abstract: The invention comprises a process for the preparation of m and p xylylenediamines by contacting solid iso or terephthalic acid with gaseous ammonia, under such conditions that a phthalonitrile containing vaporous mixture is produced, passing said mixture into a phthalonitrile recovery zone containing a solvent for the phthalonitrile, which is substantially unreactive under subsequent hydrogenating conditions, withdrawing an effluent comprising the phthalonitrile dissolved in said solvent, passing the effluent without purification directly into a hydrogenation zone, contacting the dissolved phthalonitrile with hydrogen in the presence of a hydrogenation catalyst, under hydrogenating conditions and separating the xylylenediamine so formed, from the effluent from the hydrogenation zone.  The phthalonitrile is preferably produced in two stages.  In a first non-catalytic stage ammonia and phthalic acid are contacted in a reaction incomplete enough to convert substantially all of the acid to phthalonitrile, a portion of the acid remaining uncoverted.  In the second catalytic stage the reaction is completed. The first stage may be carried out by continuously charging solid iso and/or terephthalic acid into a volatilization zone above about 500 DEG  C. and below the melting point of the acid, from about 0.1-20 atmospheres, continuously passing sufficient gaseous ammonia through the zone to form a molten and relatively volatile mass of unreacted and partially reacted portions of the acid, i.e. until to 70% of the carboxyl groups have reacted with ammonia, and also to serve as a carrier for the vapours of the said mass.  The vapours are then passed into a dehydration zone at e.g. about 650-900 DEG  F. containing a dehydration catalyst.  Where water is removed, and unreacted and partially reacted acid is converted into phthalonitrile.  Suitable specified dehydration catalysts are activated alumina, silica, and thoria, zirconium, beryllium, tungsten and vanadium oxides, basic aluminium phosphate, basic aluminium sulphate or phosphoric acid.  The catalysts may be supported.  The effluent is then passed into a recovery zone and into the desired solvent, above e.g. about 200 DEG  F., and the resulting solvent-phthalonitrile passed to a hydrogenation zone containing a hydrogenating catalyst, the so formed xylylenediamines being recovered from the effluent.  Specified hydrogenation catalysts are reduced cobalt oxide, or nickel, and suitable hydrogenation conditions are 1,500 to 10,000 p.s.i.g., 180-400 DEG  F. a space rate of 0.05 to 8 grams of phthalonitrile per c.c. of catalyst per hour, and a make-up hydrogen rate, excluding recycle hydrogen, which may be used if desired, 4 to 20 moles. hydrogen per mole. of phthalonitrile. From 10 to 50% by weight of the total feed to the hydrogenation zone of ammonia may also be added at this stage.  The effluent from the recovery zone should preferably contain from about 50-90% by weight of the solvent before undergoing hydrogenation.  Specified solvents are xylene, isopropyl alcohol dioxane, benzene and methanol and their mixtures.  The solubility parameter of the solvent or mixed solvent should not differ in either direction from that of the nitrile by more than about 2.5.  Nitrogen may be passed into the vaporizer together with the solid acid in order to facilitate the passage of the acid to the vaporizer.  Examples are given.