S. Cimino

Temperature excursions during the transient behaviour of high temperature catalytic combustion monoliths

Spatio-temporal temperature profiles experimentally observed during the operation of a structured perovskite-based catalytic monolith for the combustion of methane were simulated by means of a transient heterogeneous one-dimensional model which accounts for heat losses to the surroundings and thermal conductivity inside the monolith substrate. In fact it is shown that such thermal phenomena are essential to correctly reproduce the slow warm-up transients and the wrong-way behaviour observed in a low conductivity ceramic monolith. Model simulations reveal that at higher values of solid conductivity the catalyst does not exhibit hot spot both in time and space, but needs higher inlet gas temperatures to reach complete methane conversion. Bifurcation analysis of the catalytic monolith reactor model were carried out to study steady-state multiplicity. We show that the origin of multiplicity is purely thermal as it is mainly ruled by the heat transfer through the external surface.

Development of High Temperature Catalytic Reactors for Oxidative Conversion of Natural Gas

The catalytic oxidative conversion of natural gas and light hydrocarbons represents an attractive route for the production of both clean energy and synthetic fuels. Catalytic combustion can be regarded as an intrinsically clean and safe technology which allows a primary air pollution control, since energy is produced with high efficiency burning fuel/air mixtures also outside the flammability limits, at operating temperatures far lower than those of flame combustion and without the instability problems and pollutants (CO, NOx, soot and unburned hydrocarbons) typical of the traditional processes [1-3]. On the other hand the production of synthesis gas from natural gas by catalytic partial oxidation (CPO) is considered a desirable alternative to highly endothermic steam reforming since it overcomes some of the problems related to high energy input, utility costs and polluting emissions [4]. Moreover, in the last years, the oxidative dehydrogenation of ethane (ODH) for ethylene production has received a renewed interest, due to the evidence that olefins can be efficiently produced with high yields, also if compared with those of the existing cracking processes, in catalytic reactors operated at high space velocity (short contact time reactors, SCTR) and temperatures in the range of 900–1000°C [5].