Advanced Biofuels Based on Fischer–Tropsch Synthesis for Applications in Gasoline Engines

The aim of the article is to determine the properties of fuel mixtures of Fischer–Tropsch naphtha fraction with traditional gasoline (petrol) to be able to integrate the production of advanced alternative fuel based on Fischer–Tropsch synthesis into existing fuel markets. The density, octane number, vapor pressure, cloud point, water content, sulphur content, refractive index, ASTM color, heat of combustion, and fuel composition were measured using the gas chromatography method PIONA. It was found that fuel properties of Fischer–Tropsch naphtha fraction is not much comparable to conventional gasoline (petrol) due to the high n-alkane content. This research work recommends the creation of a low-percentage mixture of 3 vol.% of FT naphtha fraction with traditional gasoline to minimize negative effects—similar to the current legislative limit of 5 vol.% of bioethanol in E5 gasoline. FT naphtha fraction as a biocomponent does not contain sulphur or polyaromatic hydrocarbons nor benzene. Waste materials can be processed by FT synthesis. Fischer–Tropsch synthesis can be considered a universal fuel—the naphtha fraction cut can be declared as a biocomponent for gasoline fuel without any further necessary catalytic upgrading.

Hydrocracking of Fischer-Tropsch Wax

The low-temperature Fischer-Tropsch synthesis (LTFT) processing of renewable feedstocks combined with the hydrocracking of its solid product is an effective way to produce synthetic renewable engine fuels. The hydrocracking of an FT wax derived from natural gas using the LTFT synthesis was studied in this paper. The hydrocracking was carried out in a tubular fixed-bed reactor with a cocurrent flow of the feedstock and hydrogen. Reaction temperatures in the range of 305– 370 °C, a pressure of 8 MPa, an H2/feed ratio of 500 m3/m3 and weight hour space velocities (WHSV) of 1; 2 and 4 h-1 were tested. The naphtha fraction (boiling up to 200 °C) was the main product of the hydrocracking under all the tested reaction conditions. It could be used as a component into petroleum-derived gasoline in a neat form or the after processing by common refinery processes (isomerization and/or reforming). The production of low-sulfur and low-aromatic paraffinic solvent or the utilization as a feedstock for steam cracking could be some other options of the naphtha fraction utilization. The maximum yield of the gaseous products (depending on the reaction temperatures and WHSV) was 20 wt.%. They were primarily composed of n-alkanes and isoalkanes and could be, therefore, used as an optimal feedstock for steam cracking as well. The C3-C4 fraction of the gaseous products could be also utilized as an LPG fuel. Very low yields (up to 10.4 wt.%) of the middle distillates were obtained under all the tested reaction conditions. Due to their saturated nature, their densities were very low and, additionally, poor low-temperature properties can be expected.