Upgrading of BTL-FT naphtha to gasoline

Naphtha is produced as a by-product of the BTL-FT process, both straight-run from the FT reactor and as a co-product of the upgrading of the FT wax to middle distillates. BTL-FT naphtha has a low octane number and cannot be used as a gasoline blending component. The two dominant processes that have been considered for upgrading FT naphtha to high-octane gasoline are isomerization and reforming. Given that straight-run FT naphtha contains olefins and oxygenates that are not compatible with commercial reforming or isomerization technologies, a hydrotreating step is first required to convert olefins and oxygenates in the naphtha to paraffins (Gregor and Fullerton, 1989). According to a techno-economic study by Kreutz et al. (2008), the optimum BTL-FT plant configuration in order to maximize the yield of premium diesel and gasoline fuels is to isomerize a portion of the naphtha in order to convert normal paraffins to isoparaffins and boost its octane value and catalytically reform the other fraction to provide some aromatic content to (and further boost the octane value of) the final gasoline blendstock. However, it is still uncertain whether the additional gasoline blending stock value can justify the great capital and operational costs that these upgrading units impose on the BTL-FT process and explains why this option has yet to be considered in commercial operations.