Vaporization-Induced External Dewetting of a Catalyst during an Exothermic Multiphase Reaction

A heterogeneous model is developed to elucidate the phenomena of dewetting and hot-spot formation during an exothermic reaction in a gas-liquid fixed-bed reactor. The model focuses on processes external to the catalyst and accounts for the mass, energy, and momentum transport, vaporization, and reaction on the gas- or liquid-covered catalytic solid surface. For a typical olefin hydrogenation reaction, model predictions indicate that the system is external heat- and mass-transfer limited and that thermokinetic coupling causes steady-state multiplicity. In addition, the effects of the heat of reaction, catalytic activity, liquid-phase volatility, and solid-phase thermal conductivity on the location of the dewetting point and conversion are assessed.