(164b) Partial Oxidation of O-Xylene to Phthalic Anhydride Inside of the Explosion Regime Using a Micro Structured Reactor

Heterogeneously catalyzed selective oxidations in the gas phase are an important class of reactions which is usually carried out outside the explosion regime in conventional laboratory and production reactors.  These processes are carried out at rich or lean feed compositions, so above the upper explosion limit or below the lower explosion limit. The o-xylene gas phase oxidation to phthalic anhydride was investigated inside of the explosion regime using micro structured reactor. For these investigations a V₂O₅/TiO₂ grafting catalyst was used as micro fixed bed and as wall catalyst to evaluate the potential of this reaction at high o-xylene concentrations. High selectivities to phthalic anhydride were obtained up to 7 vol.% o-xylene stoichiometric with O₂ as well as high space-time-yields. At higher o-xylene concentrations the selectivity to phthalic anhydride decreased, possibly due to a hotspot, which was estimated at high o-xylene concentrations and could be approved indirectly with a characterisation of the used catalyst.