## 3 Results and Discussion
### Blending Experiments  
For this proposal, four mixtures of the diesel fraction of distilled FTS waxes (D-FTS) and fossil diesel (FD) were prepared: 7:93, 15:85, 30:70, and 50:50 wt.%. Table 2 shows the product characterisation for each mixture and EN590 norm values. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Properties** & **FTS Wax Raw Material \({}^{*}\)** &
\begin{tabular}{c} **FTS Wax without Light** \\ **Compounds and Water \({}^{*}\)** \\ \end{tabular} & **FTS Wax Distillation Product \({}^{**}\)** \\ \hline S content, mg/kg & 2.2 & N/A & N/A \\ \hline N content, mg/kg & 83.7 & N/A & N/A \\ \hline Elemental analysis & & & \\ \hline C content, wt.\% & 80.8 & N/A & N/A \\ \hline H content, wt.\% & 14.1 & N/A & N/A \\ \hline Boiling range fraction & & & \\ \hline Gasoline (\textless{180 }^{\circ}\)C) & 1.0 & 0.0 & 0.0 \\ \hline Diesel (180–360 \({}^{\circ}\)C) & 42.0 & 39.0 & 38.0 \\ \hline Heavy/residue (\textgreater{}360 \({}^{\circ}\)C) & 57.0 & 61.0 & 58.0 \\ \hline Losses (wt.\%) & 0.0 & 0.0 & 4.0 \\ \hline \multicolumn{4}{l}{\({}^{*}\)Simids; \({}^{**}\) PILODIST distillation.} \\ \end{tabular}
\end{table} 
Table 1: Basic feedstock properties of Fischer-Tropsch waxes raw material and boiling range fractions Fischer–Tropsch waxes after water elimination and distillation. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Analysis** & \begin{tabular}{c} **Fossil** \\ **Diesel** \\ \end{tabular} & \begin{tabular}{c} **Mix 1** \\ **D-FTS:FD** \\ **7:93** \\ \end{tabular} & \begin{tabular}{c} **Mix 2** \\ **D-FTS:FD** \\ **15:85** \\ \end{tabular} & \begin{tabular}{c} **Mix 3** \\ **D-FTS:FD** \\ **30:70** \\ \end{tabular} & \
\begin{tabular}{c} **Mix 4** \\ **D-FTS:FD** \\ **50:50** \\ \end{tabular} &
\begin{tabular}{c} **Diesel Fuel Standards EN590** \\ **Min.** \\ \end{tabular} \\ \hline Density at 15 \({}^{\circ}\)C, kg/m\({}^{3}\) & 834.9 & 831.2 & 827.2 & 819.5 & 809.1 & 820 & 845 \\ \hline Kinematic viscosity at 40 \({}^{\circ}\)C, mm\({}^{2}\)/s & 2.6 & 2.6 & 2.7 & 2.7 & 2.9 & 2.0 & 4.5 \\ \hline Sulphur content, mg/kg & 8.1 & 6.3 & 5.3 & 5.1 & 4.4 & N/A & 10.0 \\ \hline Nitrogen content, mg/kg & 20.9 & 23.8 & 25.7 & 30.8 & 38.0 & N/A & N/A \\ \hline Poliaromatics, wt.\% & 8.0 & 7.3 & 7.0 & 6.7 & 5.3 & N/A & 8.0 \\ \hline Elemental analysis (wt.\%) & & & & & & & \\ \hline Carbon content & 86.7 & 86.4 & 86.6 & 86.4 & 85.9 & N/A & N/A \\ \hline Hydrogen content & 13.2 & 13.6 & 13.3 & 13.5 & 14.2 & N/A & N/A \\ \hline Distillation & & & & & & \\ \hline Evaporates at 250 \({}^{\circ}\)C: & 40 & 40 & 40 & 30 & 30 & N/A & 65 \\ \hline Evaporates at 350 \({}^{\circ}\)C: & 100 & 100 & 100 & 97 & 100 & 85 & N/A \\ \hline
95\% evaporated at: & 345.8 & 345.5 & 342.5 & 342.3 & 339.6 & N/A & 360 \\ \hline Cetane index & 50 & 53 & 55 & 60 & 67 & 46 & N/A \\ \hline Cetane number & 53 & 54 & 57 & 64 & 73 & 51 & N/A \\ \hline Flash point, \({}^{\circ}\)C & 68 & 68 & 71 & 73 & 77 & 55 & N/A \\ \hline Refractive index & 1.4624 & 1.4611 & 1.4595 & 1.4537 & 1.4494 & N/A & N/A \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Basic properties of fossil diesel and its mixtures with the diesel fraction of distilled Fischer–Tropsch waxes. Adding D-FTS to FD significantly increased the cetane index and relative parameters (flash point and cetane number). Moreover, it also decreased the density, sulphur content, nitrogen content, and polyaromatic compounds. These effects were clearly due to the paraffin nature of FTS waxes (Figure 1). Similar behaviour has also been observed during the co-processing of vegetable oil (HVO) into middle distillates due to the increase of paraffin compounds [40; 41]. Nevertheless, at the highest D-FTS:FD blending ratios (i.e., 30:70 and 50:50 wt.%), density and CPFF were entirely out of diesel fuel standards (i.e., 820-845 kg/m\({}^{3}\); >0 \({}^{\circ}\)C). Thus, it is possible to claim that the maximal possible D-FTS addition to FD is a value between 15 and 29% wt.%. Two linear models based on experimental data were determined for CPFF and density.