Comparative TPR and TPD Studies of Cu and Ca Promotion on Fe-Zn- and Fe-Zn-Zr-Based Fischer-Tropsch Catalysts

Abstract

© O.O. James et al. The present study demonstrates the effect of zirconium promotion on Fe-Zn-based catalysts to boost the active sites of Fischer-Tropsch (FT) catalysts. The catalysts are also promoted by Cu and Ca and the active sites are examined using Temperature- Programmed Reduction (TPR) with H2 and CO and Temperature-Programmed Desorption (TPD) with NH3 and CO2. The results are presented as a comparative study between Fe-Znand Fe-Zn-Zr-based catalysts. The results show that addition of Zr to Fe-Zn catalysts increases the availability and dispersion of the precursor to the active sites and promotion with Cu and Ca independently and synergistically enhances reduction of Fe-Zn-Zr-based catalysts. The presence of Ca promotes carburisation, while Cu inhibits carburisation. The impact of the Ca and Cu on the surface acidity/basicity is governed by the nature of the interaction between the phases in the catalysts. The extent of reduction reflects the availability and dispersion of the precursor to the active phase, while the extent of carburisation will impact on the selectivity of the catalysts.