Sintering of nickel steam-reforming catalysts

Sintering is an important deactivation mechanism for nickel-based steam-reforming catalysts. In this work, the effects of nickel loading, carrier surface area, and temperature on the nickel surface area are studied. The experiments are performed under simulated industrial conditions, i.e., in a mixture of steam and hydrogen (10 : 1) in the temperature range of 500-682 degreesC and at 30 bar total pressure. The data are analyzed using a simple model assuming spherical particles and a lognormal metal particle-size distribution with constant standard deviation. It is also assumed that the sintering proceeds via crystallite migration and coalescence. The model predicts well the experimental nickel surface area as a function of nickel loading, carrier surface area, temperature, and time. The model is also used to analyze data from the literature. The model is discussed in the context of predicting metal surface areas of catalysts consisting of small metal particles on ceramic supports. (C) 2003 Elsevier Science (USA). All rights reserved.