The scaling-up of the gas phase catalytic ammoxidation of 2 6-dichloro toluene (DCT) to 2 6-dichloro benzonitrile (DCBN) over a promoted vanadium phosphate (VPO) catalyst from first lab-scale experiments to pilot plant runs is reported First experiments in a row of conversions of isomeric dichloro toluenes using simple non-promoted VPO catalysts only show poor yield and selectivity In particular DCT ammoxidation is hindered due to bulky chlorine substituents probably preventing a sufficient interaction of the methyl group and lattice oxygen and/or N-containing surface species Improved synthesis of VPO catalyst with the addition of promoters and gamma-alumina or mania leads to significant increase in DCT conversion and DCBN yield A Cr containing vanadyl pyrophosphate catalyst admixed with Mania (anatase) showed conversion up to 97% with DCBN yields of ca 80% The same catalyst was also used for pilot plant runs usually in the form of 5 mm x 3 5 mm shaped tablets that were prepared from a larger batch of solid synthesis The scaling-up of the process using 100 ml of catalyst was investigated both by catalytic experiments and reactor simulations The results showed that the temperature control will be crucial in scaling-up Validation of simulation results with that of experimental results was also checked and a good agreement between measured and simulated results is observed (C) 2010 Elsevier B V All rights reserved