EKU Faculty and Staff Scholarship


Deuterium enrichments in hydrocarbons produced during ruthenium catalyzed Fischer-Tropsch synthesis



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Fischer-Tropsch synthesis was carried out with a ruthenium catalyst by using H2/D2 switching and competitive methods. The results showed that there is an inverse isotope effect during ruthenium-catalyzed Fischer-Tropsch reactions with the hydrocarbon production rate increasing when syngas was switched to D2/CO. When the ruthenium-catalyzed Fischer-Tropsch synthesis was conducted using a mixture of H2/D2/CO (1:1:1) as the syngas, the H/D ratios in hydrocarbons produced by the reaction are less than 1, indicating that the deuterium was enriched in these hydrocarbons. Also, the deuterium enrichment is a function of carbon number with more deuterium enriched in larger hydrocarbons. These results are similar to the results of cobalt and iron catalyzed Fischer-Tropsch reactions we have reported earlier. To explain these results and other experimental facts accumulated over the years about Fischer-Tropsch synthesis, we proposed the alkylidene mechanism for this important reaction, in which MCH is the monomer of this polymerization-like reaction and M=CHR is the growing chain. Based on this mechanism, we developed mathematic equations for each step of propagations to calculate the deuterium enrichment. The theoretic deuterium enrichment results calculated based on the Alkylidene mechanism are very close to the experimental results of deuterium enrichment of ruthenium-catalyzed Fischer-Tropsch reactions.


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Catalysis Today