One-step selective synthesis of 2-chlorobenzonitrile from 2-chlorotoluene via ammoxidation

Abstract

A series of V₂O₅/Al₂O₃ catalysts were prepared by a wet impregnation method and employed for a one-step synthesis of 2-chlorobenzonitrile from 2-chlorotoluene via ammoxidation in a fixed bed reactor at atmospheric pressure. The catalysts were characterized by BET-SA, XRD, FT-IR, TPR, UV-Vis DRS and NH₃-TPD to identify the molecular structural changes of the catalysts. The characterization results revealed that the addition of V₂O₅ to Al₂O₃ amplified the crystallinity of alumina and also resulted in the formation of an interactive species i.e. AlVO₄. Most of the V₂O₅ existed in the form of isolated surface and polymeric tetrahedral vanadia species in a highly dispersed state and/or having a strong interaction with the support. The formation of different kinds of vanadia species was entirely dependent on the content of vanadia present in the catalyst. A 10 wt% V₂O₅/Al₂O₃ catalyst was found to be the best and the high selectivity for 2-CBN was presumably due to the formation of the isolated surface and polymeric tetrahedral vanadia species along with aluminum vanadate species.