Kinetic Modelling of Fischer-Tropsch Product Distributions
Dr. Michael Claeys
University of Cape Town
Wednesday, May 28, 2003 4:00 pm
Ben Bendy Conference Room
Center For Applied Energy Research
The variety of composition of Fischer-Tropsch products with hundreds of individual compounds shows a remarkable degree of order with regard to class and size of the molecules. This suggests a strict kinetic basis, which is undoubtedly complex, however as not accidential, it is well suited for kinetic modelling, provided the main reactions on the catalyst surface and their interrelations are well understood, as based on thoroughly measured experimental data.
Starting from the concept of Fischer-Tropsch synthesis as an ideal polymerisation reaction (Schulz-Flory kinetics) it is easily realised that the main primary products, olefins, can undergo secondary reactions and thereby modify the product distribution. This generally leads to chain length dependencies of certain olefin reaction possibilities, which are again suited to serve as a characteristic feature for the kind of olefin conversion.
Although the occurrence of these consecutive reactions has principally been known since the very early days of Fischer-Tropsch synthesis, they have only recently been incorporated into several kinetic models describing product distributions. These models, the assumptions and the experimental data they are based on as well as their potential to predict product selectivity, will be critically reviewed in this presentation.