## 3 Results and Discussion
### Desulfurization Properties  
Fourier transform infrared (FTIR) Spectroscopy  
Figure 10 shows the infrared (IR) spectrum obtained after the aqua-thermolysis process at 200 \({}^{\circ}\)C of heavy crude emulsion: without sample (Figure 10a) and with sample milled at 125 h (Figure 10b) and 150 h (Figure 10c). According to the sample milled at 125 h, a wide peak was observed at 3422 cm\({}^{-1}\), corresponding to the hydroxy (O-H) group, which indicated that the water used reacted with the compounds in the crude oil, promoting the formation of alcohols and carboxylic acids. The strong absorption bands at 2925 cm\({}^{-1}\) and 2856 cm\({}^{-1}\) corresponded to saturated compounds (C-H), showing a slight increase due to hydrogenation of the unsaturated groups; this hydrogenation was caused by the Mo phase. The sample milled at 150 h showed an increase and widening in the peaks to 490 cm\({}^{-1}\) and 607 cm\({}^{-1}\), corresponding to polysulfides and disulfides, respectively. Aqua-thermolysis is a technique that can generate free radicals during the breaking of molecules; these free radicals participate in polymerization reactions, producing larger molecules [40]. There is an increase in chemical activity in desulfurization of about 15% caused by an increase in Fe in the sample. According to the literature, the increase in Fe amount can lead to increased chemical activity, as reported with a Fe content of about 0.85 at.% [20]. The appearance of 1066 cm\({}^{-1}\) peak suggested that the reaction led to chain breakage, but then were polymerized, forming larger polysulfide molecules. This phenomenon indicated the desulfurization of heavy oil by the sample milled at 150 h, but then a polymerization reaction was observed after the aqua-thermolysis process. For both samples, there was a loss of peak intensity at 822 cm\({}^{-1}\), corresponding to the group C=C; this can be attributed to three factors: (1) hydration of alkenes--water is added to the double bond forming alcohols, (2) hydrogenation of alkenes--hydrogen is added to the double bond forming saturated compounds, and (3) breakage of double bonds [41]. One event that is always present in MA synthesis is the cross contamination in samples, usually of Fe due to wear and tear of the milling tools. If the proposal of using MoWC material is for catalysis during the aqua-thermolysis of heavy oil, the presence of Fe can interact with asphaltenes causing the reduction of the strength of the C-C, C-N, and C-S bonds. Therefore, it is an element commonly used in the synthesis of catalysts for hydrodesulfurization, such as hematite (Fe\({}_{2}\)O\({}_{3}\)), which shows excellent catalytic activity in reducing the viscosity of heavy oil [37; 42]. Figure 8 shows the distribution of the elemental SEM maps. The distribution showed that these particles were mainly composed of carbon and molybdenum, with a small contribution of tungsten, demonstrating the presence of the nanostructured MoW bimetallic carbide in a solid solution under X-ray results.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample (h)** & **Speed (rpm)** & **Crystal Size (nm)** & **Vickers Hardness (GPa)** & **Vickers Std. Dev. (GPa)** \\ \hline
25 & 500 & 118.3 & 10.5 & 1.1154 \\
50 & 500 & 84.1 & 13.35 & 1.1542 \\
75 & 500 & 58.7 & 24.97 & 2.0584 \\
125 & 1500 & 45.6 & 27.48 & 2.0685 \\
150 & 1500 & 40.8 & 31.48 & 2.1258 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Evolution of Vickers hardness at different milling times.