Studies on the Catalytic Synthesis of Aromatic Nitriles (Part 2)

Ammoxidation Reaction of Various Aromatic Compounds with SO₂ as a Oxidizing Agent

Abstract

In order to clarify the profile of vapour phase catalytic ammoxidation reaction with SO₂ as an oxidizing agent, the reactions of various substituted aromatic compounds i.e. methylnaphthalene, ethylbenzene, cumene, styrene, benzaldehyde, n-heptane and methylcyclohexane were investigated.
It was found that the reaction of methylnaphthalene gave the corresponding naphthonitrile, while the reaction of ethylbenzene and cumene gave benzonitrile and styrene, benzonitrile, α-methylstyrene and a small quantity of α-phenylacrylonitrile, respectively. The reaction of methylcyclohexane gave benzonitrile and toluene. Also n-heptane was converted to benzonitrile and toluene more slowly than methylcyclohexane. Benzaldehyde was readily converted to benzonitrile even over fused alumina (Alundum: α-Al₂O₃) alone. The reactivity of these compounds decreased with increasing size of substituent group.
Addition of K₂CO₃ to catalyst supressed the activity for formation of nitrile, but little for dehydrogenation reaction. The dehydrogenation reactions were promoted even by the fused alumina catalyst (Alundum: α-Al₂O₃) alone.
Therefore, it was assumed that the dehydrogenation took place prior to formation of nitrile under the conditions of ammoxidation reaction.