The simulation of a reverse-flow operation of a fixed-bed catalytic reactor, where the highly exothermal partial oxidation of o-xylene to phthalic anhydride is processed, is accomplished by using a heterogeneous one-dimensional model, which accounts for mass transport by diffusion and convection inside large-pore catalytic particles. The dynamic behaviour of the reactor is analysed by varying the inlet conditions and the switching period. This work. points out the benefits that can arise from the use of the reverse-flow operation, namely the decrease of the hot-spot temperature and the more favourable temperature distribution along the bed. In spite of the lower temperature profiles, the final conversion, as well as selectivity and yield of phthalic anhydride are not. significantly affected. The results predicted by the heterogeneous model with intraparticle convection and diffusion, HT,, model, are compared with those obtained when diffusion is the only transport mechanism inside the catalyst, HT, model. A comparison with the simple pseudo-homogeneous model, PH, is also achieved.