Effects of Interference Techniques On Fischer-Tropsch Product Distributions

Dwindling crude oil supplies will soon necessitate development of alternate sources of transportation fuels. The Fischer-Tropsch (FT) synthesis produces liquid fuels from coal-derived synthesis gas, but current product distributions from the synthesis are not sufficiently selective toward heavier hydrocarbons to render new FT plant construction economically feasible in the long term. We will focus on novel reaction engineering schemes, referred to as interference techniques, in attempts to improve the yield of heavier hydrocarbons in FT product distributions. For example, distributed synthesis gas feeding is one such technique. The distributed synthesis gas feeding strategy was explored experimentally by using two plug flow reactors in series and feeding synthesis gas at the entrances of both. The results from these experiments are compared against those from a conventional synthesis gas feeding strategy in which reactants were fed to the entrance of the first reactor only. It was found that a distributed feeding strategy is counterproductive for generating heavier product distributions when complete or near-complete CO conversion is effected within each reactor. However, when operating the first reactor at low CO conversions, the distributed synthesis gas feeding strategy was shown to improve the selectivity of C5+ hydrocarbons as compared to a conventional feeding strategy. This presentation will cover experimental techniques and results, and it will present results of FT reaction modeling efforts that aid in the explanation of experimental observations.