Patent GB-803901-A (GB)
Title: Improvements in the preparation of aromatic nitriles and imides
Inventor: HADLEY DAVID JAMES
Filed: 1956-09-19
Abstract: Catalysts for use in the production of aromatic nitriles or imides by the reaction in vapour phase of alkyl aromatic hydrocarbons with ammonia and oxygen comprise mixtures of vanadium and tin oxides deposited on activated alumina, which has been previously heated, prior to deposition of the catalyst to a temperature between 1000 DEG and 1500 DEG  C.  The catalyst may be prepared by co-precipitating the vanadium and tin oxide from a mixed solution of their salts on to the support, or the support may be impregnated with a solution of the soluble salts of the two metals, dried and heated in air or oxygem to oxidize the salts to the corresponding oxides.  The alumina is preferably preheated between 12 and 24 hours in air.  The mixed oxides are preferably deposited on to the heat-treated activated alumina, by evaporating a solution of vanadyl oxalate and stannous chloride on to the alumina.  The catalyst is then heated in air to about 350 DEG  to 400 DEG  C.  Suitable proportions of vanadium and tin oxides are 0.1 to 20 per cent by weight of the total catalyst, and the relative proportions of vanadium to tin are preferably in the atomic ratio of 2 : 1.  The catalyst may be diluted with an inert substance such as brick, pumice, or carborundum.  Examples are given by the preparation of the catalyst using varying proportions of vanadium to tin oxide.  A further example also describes the preparation of a similar catalyst not supported on heat treated alumina.ALSO:The invention comprises a process for the production of aromatic nitriles or imides by contacting at an elevated temperature a mixture in the vapour phase of an alkyl substituted aromatic hydrocarbon or its nuclear substituted monohalo derivative, ammonia and molecular oxygen with a catalyst comprising mixtures of vanadium oxide and tin oxide deposited on activated alumina, which has been preheated prior to deposition of the catalyst, between 1000 DEG  and 1500 DEG  C.  The starting materials used for the process are benzene, or naphthalene or their nuclear substituted monohalo derivatives, substituted by at least one group of formula: <FORM:0803901/IV (b)/1> where R represents hydrogen or C1-C2 alkyl. Suitable alkyl substituted aromatic hydrocarbons are toluene, ethylbenzene, o, m and p xylene, mesitylene, o, m and p di-isopropyl benzene, o, m and p cymene, o, m or p chlorotoluene and a  and b methylnaphthalenes or mixtures thereof.  The proportion of vanadium and tin oxide in the catalyst may be between 0.1 and 20 per cent based on the weight of the total catalyst.  The relative proportions of vanadium to tin are preferably in the atomic ratio of 2:1, and the active catalyst granules are preferably diluted with an inert material such as brick, pumice or carborundum.  The reaction may be carried out between 300 DEG  and 500 DEG  C. for a contact time of e.g. 0.25 to 20 seconds.  The vapour phase catalysis may be carried out in a stationary or moving bed, preferably a fluidized bed. Suitable ratios of ammonia to alkyl substituted hydrocarbon are at least 1 1/2 to 2 times the theoretical amount of ammonia needed for the stoichiometric reaction, and suitable concentrations of alkyl-substituted aromatic hydrocarbon are not more than 2 per cent by volume of the total gaseous reaction mixture.  The gas mixture fed to the reaction chamber should preferably contain at least 5 per cent by volume of oxygen and at least 3 mols. of oxygen per mol. of hydrocarbon.  Suitable mixtures are air or mixtures of air with oxygen.  Examples are given illustrating the process of the invention of the preparation of terephthalonitrile and p-tolunitrile from p-xylene and isophthalonitrile from meta-xylene.  Other reactions mentioned are the preparation of benzonitrile from toluene or ethylbenzene, phthalimide, o-tolunitrile and phthalonitrile from o-xylene, m-tolunitrile from m-xylene and tricyanobenzene from mesitylene.  An example is also given of the preparation of terephthalonitrile from p-xylene using a catalyst consisting solely of mixed tin and vanadium oxides, not supported on alumina.