Schanke, D.; Hilmen, A. M.; Bergene, E.; Kinnari, K.; Rytter, E.; dnanes, E.; Holmen, A.

Energy & Fuels (1996), 10(4), 867-872 CODEN: ENFUEM; ISSN: 0887-0624. English.

The role of water in the deactivation of Al2O3-supported cobalt Fischer-Tropsch catalysts was studied under different water partial pressures. In addition, model studies under nonreacting conditions using H2O/H2 feeds were carried out in order to study the possible reoxidn. of cobalt by water. High-pressure gravimetry, temperature-programmed reduction (TPR), and XPS were used as characterization methods. Significant deactivation was observed when water was added to the feed in fixed-bed expts. In model studies, a large extent of bulk cobalt reoxidn. was only observed in the absence of H2. Only a small amount of reoxidn. could be observed when H2 was present, even at high H2O/H2 ratios. However, XPS studies indicated significant surface oxidation of cobalt at lower H2O/H2 ratios. Surface oxidation or oxidation of highly dispersed cobalt phases were concluded to be responsible for the observed deactivation. The possibility of changes in the phase distribution of the catalysts caused by the presence of high water partial pressures was discussed based on TPR studies of H2O/H2-treated and H2O/He-treated catalysts.