Surface analysis of lanthanum-modified cobalt catalysts. Invited lecture

Abstract

The effect of the addition of La on the structure of 3% m/m Co/Al₂O₃ catalysts has been studied by the combined use of X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction and gravimetric analysis. It was shown that La exists as a highly dispersed La—Al₂O₃ interaction species for alumina carriers impregnated with La and calcined at 600 °C. For 3% m/m Co/Al₂O₃ catalysts containing La, little effect is observed for La/Al atomic ratios below 0.0075. For higher La loadings, an increase in Co dispersion is observed owing to suppression of Co₃O₄ formation. Tetrahedral Co²⁺ and a small amount of an La—Co surface phase are formed. Formation of tetrahedral Co²⁺ is caused by migration of Co from the La—Co surface phase into the alumina support during calcination at 600 °C.