Synthesis of 3-fluorobenzaldehyde by gas-phase selective oxidation on Fe-Mo oxide/boralite catalysts

The gas-phase selective synthesis of 3-fluorobenzaldehyde from 3-fluorotolu ene over bulk iron molybdate and Fe-Mo oxide in a host boralite sample is d escribed. The latter samples, prepared by adding Fe and Mo by chemical vapo r deposition to the boralite, show high selectivity in oxidation, making yi elds of 3-fluorobenzaldehyde of over 40% possible. The pretreatment of the zeolite to eliminate extra-framework boron improves behavior, and secondary post-addition of molybdenum by CVD to increase the Mo/Fe ratio in the cata lyst has a similar enhancing effect. The behavior of Fe-Mo/boralite samples proves significantly better, in terms of both specific activity (per mass of active phase) and selectivity, than bulk Fe-2(MoO4)(3), but at high conv ersion lower selectivities are found probably due to the presence of limita tions in the backdiffusion of 3-fluorobenzaldehyde.