Patent GB-835770-A (GB)
Title: Improvements in or relating to the separation of olefinic materials from mixtures
IPC: C07C51/487
Filed: 1956-10-25
Abstract: Olefinically unsaturated compounds are separated from mixtures containing them by reacting the mixture with a mercuric salt of an organic acid and an alcohol, enol, organic acid or aromatic amine, separating the resulting addition compound, decomposing it to regenerate the olefinic compound and recovering the olefinic compound.  Unsaturated compounds which may be so separated, include aliphatic olefines; styrene; unsaturated alicyclies such as cyclohexene, methycyclohexene, menthene, dipentene; unsaturated alcohols such as allyl alcohol, geraniol, citronella oil; b -carotene; steroid hormones; acids such as fumaric, oleic, cinnamic and ricinoleic acids and their esters and other derivatives. Olefinic compounds of differing reactivity can also be separated from each other.  The mercuric salt may be of any monoor poly-basic aliphatic or aromatic carboxylic acid including keto-, hydroxy-, and halogenacids, the following salts being specified: acetate, propionate, butyrate, caprylate, stearate, benzoate, salicylate, chloracetate, adipate, oxalate, malonate, succinate, phthalate, lactate, tartrate, citrate, acetylacetate and acetylsalicilate.  The compound containing an active hydrogen atom may be a mono- or poly-hydric, aliphatic, alicyclic or aromatic alcohol, an organic acid, an enol or an aromatic amine, the following organic compounds being specified : methyl-, ethyl-, isopropyl-, isoamyl- and benzyl-alcohols, cyclohexanol, glycol, acetic-, propionic, butyric-, oxalic-, malonic-, chloracetic- and lactic acids, aniline, methyl aniline, ethyl aniline and acetone. The following is a typical example of the reaction involved :- <FORM:0835770/IV (b)/1> where R represents R1O in the case of an alcohol, R1COO in an acid, R1NH in an amine and R11-CH=C(R1)-O- in an enol.  The compound containing active hydrogen should not be such that it reacts with the mercuric salt in preference to the unsaturated compound. Where it is an alcohol, an acid, e.g. that of which the mercuric salt is used, is preferably added to minimise alcoholysis of the mercuric salt.  The mercuric salt may be formed in situ by dissolving mercuric oxide in an organic acid which may be provided in excess to provide the compound containing active hydrogen.  An inert solvent such as a hydrocarbon, e.g. benzene, cyclohexane or a mineral oil product, a halogenated hydrocarbon or dioxane may be added, if the mixture containing the unsaturated compound is difficult to dissolve.  The reaction can also be carried out in two phases, the unsaturated compound in one and the mercuric salt and compound containing active hydrogen in the other, the unsaturated compound gradually reacting with and dissolving in the latter phase.  Where the product is insoluble in the reaction mixture it may be separated by filtration. Where it is soluble the product mixture is washed with water to remove organic acid formed in the reaction and excess mercuric salt. The desired product can then be separated by distillation at low pressures and temperatures below 50-60 DEG  C. or by adsorption on activated carbon, cellulose, sugar, aluminium oxide, fuller's earth, or silica gel from which it may be removed by washing with alcohol. The product can be decomposed with an acid solution containing halogen, cyanide or thiocyanate ions, particularly by using gaseous or aqueous hydrogen chloride, and the liberated unsaturated compound separated.  The mercuric salt may then be precipitated as the oxide by addition of alkali and redissolved in an organic acid to be used again.  The process can also be applied to separating unsaturated compounds of varying activity from each other, such as a 1-olefine from a less reactive 2-olefine and cis- and trans-isomers from each other.  In the examples the following compounds are separated: (1) tridecene from tridecane in cyclohexane using mercuric propionate and ethyl alcohol; (3) tridecene from mineral oil using mercuric propionate and propionic acid; (4) olefines from a Fischer-Tropsch "Kogosin" of boiling range 219-321.5 DEG  C. using mercuric propionate and ethyl alcohol; (5) olefines from a cracked gasoline using mercuric propionate and propionic acid; (6) olefines (mainly propylene) from a cracked gas containing 52% by volume olefines using mercuric propionate and methyl alcohol; (7) styrene from unsaturated alcohols (eutanol) in a pentane-hexane mixture using mercuric propionate and methyl alcohol; (8) ethyl cinnamate from benzene and cyclohexane using mercuric acetate and methyl alcohol; (9) 1-pentadecane from 2-pentadecane using mercuric acetate and methyl alcohol; (10) cisfrom trans-2-pentadecene with mercuric acetate and methyl alcohol; (11) as in (5) using mercuric oxide, stearic acid and octyl alcohol; (12) cinnamic acid from kerosene using mercuric acetate in methyl alcohol; (13) lemon oil from technical lemon oil using mercuric acetate and isopropyl alcohol; (14) 1-nonene, 2-cis-nonene and 4-cis-nonene (separately) from nonene and cyclohexane using mercuric propionate and propionic acid. Specification 835,771 is referred to.