Patent GB-796765-A (GB)
Title: Improvements in the preparation of aromatic nitriles and imides
Inventor: HADLEY DAVID JAMES
IPC: C07D209/48
Filed: 1955-09-27
Abstract: Aromatic nitriles and imides are produced by reacting in the vapour phase alkyl substituted aromatic hydrocarbons or their nuclear monohalo derivatives with ammonia and molecular oxygen in the presence of a catalyst comprising vanadium oxide deposited on activated alumina, the latter having been heated prior to deposition to a temperature between 1000 DEG  and 1500 DEG  C.  Suitable alkyl substituted aromatic hydrocarbons or their nuclear monohaloderivatives, are benzene or naphthalene, or their nuclear monohalo derivatives substituted by at least one group represented by the formula <FORM:0796765/IV (b)/1> where R1, R2 and R3 each represent a hydrogen atom, or a lower alkyl group of up to 4 carbon atoms, e.g. toluene, ethylbenzene, o-, m- or p-xylene, mesitylene, o-, m- or p-diisopropylbenzene, o-, m- or p-cymene, o-, m- or p-chlorotoluene, and alpha- and beta-naphthalene.  The catalyst may be prepared by evaporating a solution of vanadyl oxalate on activated alumina which has previously been heated to a temperature between 1000 DEG  to 1500 DEG  C. for at least 3 hours, preferably at about 1350 DEG  C. for about 20-24 hours, and then allowed to cool.  The mixture is evaporated to dryness at about 100 DEG  C. and then heated in a stream of air at 350 DEG  to 400 DEG  C.  The vanadium oxide may be between 0.1 and 10 per cent by weight of the total catalyst which may be mixed with an inert diluting material such as brick, pumice or carborundum.  The reaction is preferably carried out between 300 DEG and 450 DEG  C. with a contract time of between 0.25 and 20 seconds. The concentration of oxygen is preferably at least 5 per cent of the gas mixture with at least 3 mols. of oxygen per mol. of hydrocarbon, e.g. a mixture of air and oxygen, or air alone.  It is preferable to use about 1 1/2 to 2 times the theoretical amount of ammonia for the stoichiometric reaction and the concentration of alkyl-substituted aromatic hydrocarbon or the monohalo derivative is preferably not more than 2 per cent by volume of the total gaseous reaction mixture. The nitriles and/or imides may be recovered by tooling the hot gases to temperatures at which the nitriles and/or imides will be deposited as liquids or solids.  Examples are given of the preparation of terephthalonitrile and paratolunitrile from para-xylene under varying conditions, isophthalonitrile and m-tolunitrile from meta-xylene, phthalimide and phthalonitrile from o-xylene, terephthalonitrile from p-diisopropylbenzene, 1 : 3 : 5-tricyanobenzene, 3 : 5 - dicyanotoluene and 3 : 5 - dimethylbenzonitrile from mesitylene, benzonitrile from ethylbenzene, and benzonitrile from toluene.  The terephthalonitrile may be converted to polyethylene terephthalate.ALSO:A vanadium oxide catalyst is deposited on activated alumina pre-heated to a temperature in the range of 1000 DEG  C. to 1500 DEG  C. for a period of not less than 3 hours.  The catalyst may be prepared by evaporating a solution of vanadyl oxalate on to 10-18 mesh activated alumina which has previously been heated at about 1350 DEG  C. for about 20-24 hours and then allowed to cool. The mixture is evaporated to dryness with frequent stirring, and then heated in a stream of air at 350-400 DEG  C.  The proportion of vanadium oxide in the catalyst may be from 0.1 to 10 per cent.  An inert diluent may also be present, e.g. brick, pumice or carborundum. Examples are given of the preparation of the catalyst from vanadium pentoxide and oxalic acid using activated alumina that has been preheated at various temperatures.