Patent GB-729013-A (GB)
Title: Process for the preparation of nitriles
IPC: C07D213/85
Filed: 1953-08-04
Abstract: Nitriles are prepared by reacting nitric oxide with an alkyl-substituted organic compound containing at least one alkyl group directly attached to a carbon atom, which is in turn attached to another carbon atom by a double bond, the reaction being at temperatures between 400 DEG  and 700 DEG  C., in the presence of a dehydrogenation catalyst.  Referring to the Figure, the catalyst tube 1 is heated in a split-type electric furnace 2.  In operation the tube is packed with 50 cc. of catalyst 3 of 8-14 mesh, placed between glass helices 4 and 5 so as to occupy the hottest portion of the tube.  The thermocouple in tube 6 is used to locate <PICT:0729013/IV (b)/1> the hot-spot in the catalyst bed and the thermocouple in tube 7 regulates the furnace temperature.  The top of the catalyst tube is fitted with a gas inlet tube 8 and a constant flow dropping funnel 10.  At the start of a run, it is desirable to condition the catalyst under nitrogen and nitric oxide at 200 DEG  to 400 DEG  C. After this the compound to be nitrosated, e.g. toluene, is added through the capillary feed 14 at the desired rate.  The furnace temperature is raised in 50 DEG  C. increments until an exothermic reaction occurs. The mixed gases after reaction pass from the catalyst tube and are condensed to a mixture of unreacted material, nitrile, water and a trace of residue.  The crude condensate is distilled directly at atmospheric pressure, giving an azeotrope from which water is separated.  Distillation is continued under reduced pressure to separate the nitrile or mixture of nitriles.  Several dehydrogenation catalysts suitable for the process are specified (see Group III), a silver catalyst on an inert support being preferred but iron, ruthenium, tin, lead, cadmium, platinum and palladium either as metal, oxides, or salts may also be used.  The mol. ratio of nitric oxide to alkyl-substituted organic compound depends on the particular compound being reacted.  For highest conversion it is desirable to use the highest possible mol. ratio of nitric oxide to the compound nitrosated without causing loss in yield due to oxidation.  The preferred temperature range is 450 DEG  to 550 DEG  C. Inert diluents such as nitrogen or water vapour may be used in the reaction mixture and are advantageous in controlling over-oxidation.  Examples of compounds employable in the process of the invention are toluene, the xylenes, mesitylene, 1-methyl-2-ethylbenzene, 1 - phenyl - 4 - methylbenzene, m - tertiarybutyltoluene, 2 - methylpyridine 2 - methyl - 5 - ethylpyridine, 3 - methylpyridine, methylnaphthalene, 2-methylthiophene, 2 - chlorotoluene, 2 - nitrotoluene, 2 - methylfurane, propylene, butylenes, methyl - substituted butadienes such as isoprene and 2 : 3-dimethylbutadiene.  In examples (1-12) toluene gives benzonitrile, (13-15) p-xylene gives p-tolunitrile, benzonitrile and terephthalonitrile, (16) o-xylene gives o-tolunitrile, benzonitrile and o-phthalonitrile, (17) m-xylene gives m-tolunitrile, benzonitrile and m-phthalonitrile, (18) b -picoline gives nicotinonitrile, (19) ethylbenzene gives benzonitrile, (20) fumene gives benzonitrile, (21) p-tolunitrile gives terephthalonitrile, (22) p-chlorotoluene gives p-chlorobenzonitrile and propylene gives acrylonitrile.ALSO:Dehydrogenation catalysts are used in the production of nitriles, by reacting nitric oxide with an alkyl-substituted organic compound containing at least one alkyl group directly attached to a carbon atom, which is in turn attached to another carbon atom by a double bond, at temperatures between 400 DEG  and 700 DEG  C. (see Group IV (b)).  Examples of the catalyst which may be used are silver, iron, ruthenium, tin, lead, cadmium, platinum, and palladium, either as the free metals, oxides, or salts such as chromites, molybdites or tungstites.  The catalysts may be extended on such materials as charcoal, pumice, kieselguhr, Fullers earth, silica, alumina and thoria.  The preferred catalyst is silver extended on charcoal, alumina or silica.  The silver-on-alumina catalyst is prepared as follows: Alumina is impregnated with aqueous silver nitrate solution, ammonia and sodium hydroxide solutions added and then reacted with a reducing solution containing cane sugar, ethyl alcohol and nitric acid. Alternatively, the catalyst may be prepared by impregnating the support with the diaminesilver hydroxide and reducing thermally at the reaction temperature.