Abstract
In this work we have studied the performance of catalyst extrudates of Ni-Al2O3 promoted with potassium for steam methane reforming. The most interesting property of this catalyst is the presence of large pores (average diameter of 8 x 10(-4) m) to reduce diffusional limitations. We have determined the true kinetics using catalyst powder in the temperature range covering 757-804 K. Furthermore, experiments using a fixed bed filled with extrudates were performed in the temperature range covering 701-800 K at constant methane/steam ratio for different feed flowrates.
In the true kinetic experiments using catalyst powder it was observed that this catalyst has a very high CO2 selectivity against CO. The conversion of the catalyst is smaller than other commercial materials due to the smaller content of Ni (10%).
Experiments using catalyst extrudates showed that the reaction suffers from strong mass and heat limitations: diffusion of reactants/products and heat transfer in the gas/solid interface. The presence of large pores has an important contribution in decreasing the resistance to mass transfer in particles with 1.1 X 10(-2) m diameter. At 800 K and 2 bar the effectiveness factor was about 0.43 for the steam methane reforming reaction and 0.41 for the global reaction. (C) 2009 Elsevier Ltd. All rights reserved.