Patent GB-806492-A (GB)
Title: The production of aromatic nitriles and imides
Inventor: GASSON EDWARD JAMES
Filed: 1956-11-10
Abstract: A vanadium oxide-chromium oxide catalyst is prepared by depositing the metals as their oxides on activated alumina.  The oxides may be prepared by evaporating a solution of vanadyl oxalate and chromium oxalate on the alumina and heating the residue in air at about 350-400 DEG  C.  The alumina is preferably pretreated by heating to a temperature of 1000-1500 DEG  C. for at least 3 hours.  The preferred atomic ratio of vanadium to chromium is between 1 : 1 and 1 : 2 and the catalyst may contain between 1 and 15 per cent of each component. To facilitate heat dispersion solid inert diluents such as brick, pumice or carborundum may be added to the catalyst.  In an Example (1) solutions of vanadyl oxalate (prepared from vanadium pentoxide and oxalic acid) and chromium oxalate (prepared from chromium trioxide and oxalic acid) are evaporated on activated alumina (which has been heated at 1400 DEG  C. for 22 hours) and the residue heated in a stream of air at 400 DEG  C. for 16 hours.  The catalyst, which contains an equiatomic ratio of vanadium and chromium, is used to catalyse the oxidation of m- and p-xylene.ALSO:Aromatic nitriles and/or imides are prepared by treating an alkyl substituted aromatic hydrocarbon or its nuclear monohalogenated derivative at elevated temperature in the gas phase with ammonia and molecular oxygen in the presence of a catalyst comprising vanadium oxide and chromium oxide deposited on activated alumina.  The atomic ratio of vanadium to chromium in the catalyst is preferably between 1 : 1 to 1 : 2 and the catalyst may contain between 1 and 15 per cent by weight of each component.  The catalyst may be prepared by evaporating a mixture of vanadyl oxalate and chromium oxalate on the alumina (which may have been pretreated by heating to a temperature of 1000-1500 DEG  C.) and then heating the catalyst in air at 350-400 DEG  C.  In order to facilitate heat dissipation the catalyst may be mixed with an inert diluent such as brick, pumice or carborundum.  The catalyst may be a stationary or moving bed and a fluidized bed method may be used with advantage.  Contact times may vary and times of 0.25-20 seconds have been found to be suitable.  The starting material may be a benzene or naphthalene compound substituted by at least one group <FORM:0806492/IV (b)/1> where R1, R2 and R3 are hydrogen or a methyl or ethyl group and examples of suitable starting materials are toluene and ethyl benzene, which are converted to benzonitrile; o-xylene, which is converted to phthalimide, o-tolunitrile and phthalonitrile; m-xylene, which is converted to isophthalonitrile and m-tolunitrile; p-xylene, which is converted to terephthalonitrile and p-tolunitrile; mesitylene, which is converted to tricyanobenzene; o-, m-, p-di-isopropyl benzene; o-, m-, p-cymene, o-, m-, p-chlorotoluene and a  and b  methyl naphthalene.  The concentration of oxygen may vary but is preferably at least 5 per cent of the mixture by volume and at least 3 mols. per mol. of hydrocarbon.  The concentration of ammonia is preferably at least twice the theoretical and when m-xylene is being used 8 mols. of ammonia per mol. of xylene, i.e. 4 times the theoretical may be used to advantage.  The concentration of hydrocarbon in the mixture is preferably kept low, below 2 per cent by volume, and the reaction may be carried out in the temperature range 300-500 DEG  C., preferably 330-420 DEG  C. In the examples (1) a mixture containing 1.5 per cent p-xylene, 8 mols. of ammonia per mol. of xylene and air is passed for 3 seconds over a catalyst containing equiatomic proportions of chromium and vanadium and the percentage yield of terephthalonitrile, p-tolunitrile and carbon dioxide are given for reaction at (a) 390 DEG  C., (b) 400 DEG  C., (c) 410 DEG  C., (d) 420 DEG  C.; (2) as (1) using m-xylene.