Patent GB-987416-A (GB)
Title: Process for the separation of a mixture containing polymerizable olefinic compounds
IPC: C07C7/13
Filed: 1961-10-16
Abstract: Zeolitic molecular sieves, employed to separate mixtures containing olefins which polymerize on contact with the molecular sieve, are treated with a nitrogen base having a critical molecular cross-section at least 1<\>rA greater than the pore diameter of the molecular sieve to inhibit polymerization.  The molecular sieves used are those mentioned in the parent Specification.  Examples 4 to 6 describe (a) the removal of water from isoprene, (b) the removal of piperylene from isoprene and (c) the separation of 50/50 mixture of butylene-1 and isobutene. Many nitrogen bases are specified, e.g. aniline, quinoline, acridine and phenylene diamines.  In a preferred embodiment, nitrogen bases having a critical molecular cross-section not more than 1<\>rA greater than the pore diameter of the molecular sieve may be used in addition to the nitrogen bases referred to above.ALSO:Gas mixtures containing olefins, which easily polymerize in contact with a zeolitic molecular sieve, are separated using a zeolite which has been pretreated with a nitrogen base having a critical molecular cross-section at least 1  greater than the pore diameter of the zeolite.  The zeolites may be those mentioned in the parent Specification.  Suitable nitrogen bases are specified amongst which heterocyclic, aromatic and aliphatic amines or mixtures thereof are mentioned.  The method is particularly suitable for separating iso-olefins whether they be mono- or di-olefins.  The amount of base required is from 0,05-3% by weight, based on the weight of the dehydrated molecular sieve.  In a preferred embodiment, the nitrogen bases may be used together with one or more nitrogen bases (see the parent Specification) having a critical molecular cross-section not more than 1  unit greater than the pore diameter of the molecular sieve employed, capable of being adsorbed within the pores in order to inhibit polymerization in the inside as well as on the outside of the molecular sieve.  The amount of adsorbable nitrogen base is 1-2 millimoles per gram of sieve material.  As described, the additional base is first deposited in the pores of the sieve. The nitrogen base may be deposited on the molecular sieve by dissolving in a hydrocarbon, e.g. iso-pentane, slurrying the sieve particles therein and evaporating the hydrocarbon with agitation.  In examples, (IV) isoprene is dehydrated with tertiary-butylamine on a 4  molecular sieve at 25  DEG C.; (V) quinoline was deposited on the molecular sieve by dissolving in iso-pentane, applying the solution to the sieve material and then evaporating off the iso-pentane.  The sieve material was then treated by adsorbing therein 2 millimoles of dimethylamine per gram of sieve material.  Isoprene containing piperylene was passed through, the latter being selectively adsorbed. Ammonium can be used in place of dimethylamine; (VI) isobutylene is isolated using quinoline and ammonia in a 5  molecular sieve at 260 DEG C. Other processes referred to are (a) removing up to 5% by volume of impurity from olefins with a 4-5  molecular sieve, (b) treatment of organic feeds, e.g. removal of water vapour, carbon dioxide &c. by contact with a 4  molecular sieve, and (c) contacting mixtures of polymerizable olefinic nonhydrocarbons, e.g. acrolein and methylacrolein, and the following gases may be separated: n-butane and butylene-2 using pyridine or pyridine and ammonia; a cracked C4 fraction including n-butylene using acridine and ammonia.