(70f) XTL Process with Low Overall GHG Emissions

A patent-pending process that can be used for the production of liquid fuels from biomass/coal based syngas (H₂:CO â?¤1) over iron-based catalysts while completely suppressing the formation of CO₂ in the FTS process will be presented. Based on the most optimistic data available from Sasol, the fraction of carbon in the original coal that results in the formation of liquid hydrocarbons is only 16.9 % using iron-based catalysts. The data from research employing this new technology have shown that this fraction can be improved to 51.1 %. This is achieved by co-feeding CO₂ (produced in the upstream processes) such that the CO₂:syngas ratio in the reactor is above 3.33:1 and conducting the FTS at conditions above the critical pressures and temperatures of CO₂. The liquids selectivity moved towards higher hydrocarbons (C₁₀- C₂₂with peak content in the range of C₁₃-C₁₅). The ScCO₂ â?? FTS process also takes advantage of the strong solvent yet tunable power of ScCO₂ and allows for pressure tunable fractionation of the products. A final but important addition to the ScCO₂ â??FTs process is the addition of product gas recycle capabilities that renders the following two unique advantages. (A) recycle helps in improving the throughput (reduced reactor size). (B)Advantages of ScCO₂FTS are further enhanced by the recycle of HC gases (along with the unreacted feed) since HCs like hexane and pentane become supercritical. The results from the various stages of development of this technology will be discussed.