Patent GB-626313-A (GB)
Title: Improvements relating to the manufacture of derivatives of ethyl naphthalene
IPC: C07C15/58
Filed: 1946-07-10
Abstract: A mixture comprising methyl naphthyl carbinol and methyl naphthyl ketone is obtained by acting upon ethyl naphthalene in the liquid state with air or other oxygen-containing gas in the presence of an oxidation catalyst at a reactive temperature below that at which substantial dehydration of methyl naphthyl carbinol occurs.  The mixture obtained may then be hydrogenated to convert the ketone to methyl naphthyl carbinol and the latter then dehydrated to form vinyl naphthalene.  The oxidation is preferably effected at from 100 DEG C. to 175 DEG  C. and the pressure may vary from <PICT:0626313/IV (b)/1> atmospheric or less to 400 pounds per square inch.  Manganous naphthenate is particularly effective as oxidation catalyst but cobalt stearate, cobalt naphthenate, cupric acetate, manganous acetate, manganous carbonate, chromic naphthenate and a mixture of manganous acetate and benzaldehyde are also specified as oxidation catalysts.  Water may be present in the oxidation process.  The oxidation product mixture may, if desired be treated to separate the alcohol and ketone, e.g. by esterifying the alcohol and then distilling the ketone from the ester.  Any unconverted ethyl naphthalene may be separated from the oxidation products by distillation below atmospheric pressure and may then be returned to the oxidation process.  The crude oxidation product may first be extracted with caustic solution to remove acidic constituents.  In the diagram, a solution of manganous naphthenate in ethyl naphthalene from the vessel is passed into a jacketed-converter 3 and air is forced into the bottom of the converter.  The oxidation product is withdrawn into a caustic extractor where it is washed with sodium hydroxide solution.  The solution containing the acidic by-products is withdrawn through line 9 and the washed product passed to a filter where the precipitated manganous hydroxide and oxide are filtered off.  The filtrate passes into a column 13 and the first fraction condensed in a condenser and collected in receiver 15 whence it is returned to the receiver 1.  The second fraction is taken off as bottoms and further fractionated in column 17.  The distillate consisting of a mixture of methyl naphthyl carbinol and methyl naphthyl ketone is condensed and collected in receiver 19.  The mixture obtained may be hydrogenated to form methyl naphthyl carbinol by acting on it in the liquid state with hydrogen in the presence of a hydrogenation catalyst at a reactive temperature below that at which substantial dehydration of the methyl naphthyl carbinol takes place.  Specified hydrogenating catalysts are copper chromite, nickel and nickel alloy catalysts.  Thus the mixture may be passed upwardly through a converter 21 packed with hydrogenation catalyst, preferably copper chromite contained in jacketed tubes 22.  Hydrogen is introduced at 24 bubbled up through the converter 21 and vented at 25.  The hydrogenated product passes into a column 27 the light ends being condensed in condenser 28 collected in receiver 29 and then returned to receiver 1 while the bottoms are passed into a second column 32 where methyl naphthyl carbinol is taken off as overhead condensed in condenser 33 and collected in receiver 34.  The methyl naphthyl carbinol may be dehydrated to form vinyl naphthalene, e.g. by passing it into contact with a surface active dehydration catalyst such as activated alumina at 300 DEG  to 350 DEG  C.  The methyl naphthyl carbinol may also be dehydrated by distilling it over caustic soda in a high vacuum low pressure-drop still but dehydration over a surface-active catalyst is preferred.  The dehydration is preferably effected at atmospheric pressure but higher or lower pressures may be used.  It is also preferable to dilute the vapours of methyl naphthyl carbinol with an inert diluent gas such as carbon dioxide.  In the drawing, methyl naphthyl carbinol is vaporised in a heater 36 and after dilution with carbon dioxide introduced at 38 passes into the dehydration converter 39 which is packed with activated alumina in the jacketed converter tubes 40.  The vapours pass into the condenser 43 and are collected in the receiver 44, the carbon dioxide being vented at 45.  The vinyl naphthalene may be purified by passing it into the column 47 from which it is recovered as overhead, condensed and then collected in receiver 49.  Methyl naphthyl carbinol may be taken off as bottoms and returned through line 50 to the dehydration process.  Tables are given to illustrate the results obtained in (a) the oxidation step using manganous naphthenate as catalyst at 100 DEG  C. and 125 DEG  C.; (b) the hydrogenation using cupric chromite as catalyst at 115-120 DEG  C. and (c) the dehydration over activated alumina at 300-340 DEG  C. with and without carbon dioxide as diluent.  Specifications 626,362 and 626,363 which are divided out of the present Specification are referred to.