Abstract: Nitration of benzene is an important reaction for the production of nitro benzene, which is an important intermediate in chemical and pharmaceutical industries. Conventionally nitrobenzene is produced by liquid phase reactions employing mixed acids. A sulfuric acid/nitric acid mixture is the most commonly used nitrating agent. Generation of large amount dilute sulfuric acid, organic wastes and products of their neutralization makes the benzene nitration a environmentally harmful process. The present process enables the preparation of nitrobenzene by vapor phase nitration of benzene over solid acid catalyst, MoO3/SiO2 using nitric acid. This process is a clean and environment friendly process without use of sulphuric acid.