III International Conference

PP-II-146increased the rate of double bond isomerisation. The rate of re-adsorption of olefins decreaseswith an increase in internal olefins leading to a decrease in olefins being reincorporatedduring chain growth decreasing the Fischer-Tropsch chain growth probability (see Figure 1).The strength of the acid sites of the catalysts increased with a corresponding decrease inthe Fischer-Tropsch chain growth probability in the following order:Co/Al 2 O 3 > Co/VO x /Al 2 O 3 > Co/MoO x /Al 2 O 3 .Rate of double bondisomerisation0.30.20.100.0 0.4 0.8Relative strengh of acid sites (T.O.F)0.90.80.70.60.5Chain growth probabiltiFigure 1: Influence of strength of the acid sites on the Fischer-Tropsch selectivity of thecatalysts tested at 220°C and 20barReferences1. A. E Aksoylu, Z. Misirli, İ.Z. Önsan, Applied Catalysis A: General 168 (1998) 385-397.2. H. Chen, A.A. Adesina, Applied Catalysis A: General 112 (1994) 87-103.3. A. Guerrero-Ruiz, A. Sepúlveda-Escribano, I. Rodríguez-Ramos, Applied Catalysis A: General120 (1994) 71-83.4. R. Reichl, K. Hayek, Journal of Catalysis 208 (2002) 422-434.5. N. Takahashi, T. Mori, A. Miyamoto, T. Hattori, Y. Murakami, Applied Catalysis 22 (1986) 137-146.6. S., Zwane, S., MSc Thesis, University of Cape Town (2004).7. T.W. Wang, Y. Ding, J. Xiong, L. Yan, H. Zhu, Y. Lu, L. Lin, Catalysis Letters 107 (2006) 47-52.432