Manufacturing Of Phthalonitrile By Ammoxidation Of O-Xylene

Abstract

Phthalonitrile is an organic compound with the formula C6H4(CN)2. It is a crystalline powder having a faint grayish yellow color and a slightly aromatic odor, similar to benzonitrile. Phthalonitrile is used in organic synthesis (such as phthalocyanine pigments, paint), flame retardant and as an insecticide. In India 80% production of copper phthalocyanine is done in Gujarat. The manufacturing procedure is mixing phthalic anhydride, urea and cuprous chloride in presence of ammonium molybdate catalyst and trichlorobenzene as solvent. This is an old technology giving environmental issues like generation of ammoniacal nitrogen in the effluent also excess of urea is used which results in decomposition of ammonia and carbon dioxide. In search of green technology it was thought of to make copper phthalocyanine pigment using phthalonitrile as starting material. If phthalonitrile is produced first then use of excess urea could be avoided and environmental issues specifically ammoniacal nitrogen can be taken care off. In a single stage continuous process o-xylene is converted to phthalonitrile by reaction with ammonia and oxygen in the gas phase in a fluidized bed reactor. A mixed metal oxide catalysts comprising varying fractions of Bi,Sb,Mo and V were prepared in laboratory and activity test of all catalysts using a lab scale fixed bed reactor made of stainless steel was performed. Results of the activity test showed that when the reactants, i.e., o-xylene, ammonia and air are fed at flowrates of 3 ml/min, 6 ml/min and 43 ml/min respectively, conversion of o-xylene is very low for all the catalyst. However when the reactants i.e., o-xylene, ammonia and air were fed at flowrates of 1 ml/min, 2 ml/min and 13 ml/min respectively, o-xylene conversion increased which resulted in increase in phthalonitrile yield. Also, from the results it has been noted that catalyst in which antimony has been used has shown less conversion as compared to those in which antimony is not used.