Effect of feeding nitrogen to a fixed bed Fischer-Tropsch reactor while keeping the partial pressures of reactants the same

The effect of co-feeding nitrogen in Fischer-Tropsch synthesis (FTS) in a fixed bed reactor over a Co/TiO2 catalyst was investigated. The partial pressure of reactants (CO and H2) in the feed to the reactor was kept constant, while the partial pressure of N2 was switched between a low and high value. The low value corresponded to a syngas feed while the high value corresponded to a feed of syngas enriched with N2. A comparison of the results obtained from more than four switches between syngas and syngas enriched with N2 are reported. The results indicate that there was almost no effect on the overall reaction rate, but that there was a significant, positive effect on the product selectivity. A lower selectivity to the undesired light hydrocarbons (especially methane) was observed when co-feeding N2. Such results cannot be explained by classic kinetics alone as the partial pressures of CO and H2 were held constant during the experiment. The laboratory data indicates that the selectivity to the (C5-C19) fraction is particularly enhanced by co-feeding N2 in FTS.