## 3 Results and Discussion
### Bio-Oil Analysis
#### 3.4.2. CHN Analysis  
In addition to the qualitative characterization, liquid products were analyzed by means of elemental composition. Table 7 shows the elemental analysis of the different fractions varying the condensation temperature of the first condenser. A slight decrement in carbon content was observed, reducing the temperature from 170 \({}^{\circ}\)C to 100 \({}^{\circ}\)C, meaning that some long-chain carbon-rich compounds present in the vapor stream were migrating to the downstream collectors due to complex interaction of dew point changing and residence time inside the condensing chamber. It is also well predicted and confirmed that the aqueous phase, obtained in the last condenser, concentrates a substantial amount of oxygen mainly due to the presence of a high percentage of water plus a small amount of trapped oxygenated compounds. Carbon content in this fraction was still relatively high and settled around roughly 16%.  
CHN analysis was used to estimate the higher heating values (HHV) of the produced cuts. Figure 6 shows the evolution of the higher heating values as a function of the condensation temperature. The higher heating value of the bio-oil collected in the first condenser increased from 24 to 25 MJ kg\({}^{-1}\) when the condenser temperature increased from 100 to 170 \({}^{\circ}\)C.  
This is due to a higher concentration of lignin-derived compounds in the oil condensed at higher temperatures, which have a relatively low oxygen content compared to the light  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & & **170 \({}^{\circ}\)C** & & & **130 \({}^{\circ}\)C** & & & **100 \({}^{\circ}\)C** & \\ \hline
**Liquid Fraction** & **C (wt.\%)** & **H (wt.\%)** & **N (wt.\%)** & **C (wt.\%)** & **H (wt.\%)** & **N (wt.\%)** & **C (wt.\%)** & **H (wt.\%)** & **N (wt.\%)** \\ \hline
**First fraction** & \(61.1\pm 0.2\) & \(5.82\pm 0.001\) & \(0.15\pm 0.003\) & \(60.1\pm 0.046\) & \(5.85\pm 0.032\) & \(0.13\pm 0.038\) & \(58.9\pm 0.165\) & \(6.10\pm 0.004\) & \(0.31\pm 0.192\) \\ \hline
**Second fraction** & \(53.4\pm 0.003\) & \(6.60\pm 0.00\) & \(0.55\pm 0.03\) & \(51.7\pm 0.068\) & \(6.63\pm 0.002\) & \(0.59\pm 0.039\) & \(53.0\pm 0.045\) & \(6.62\pm 0.013\) & \(0.07\pm 0.008\) \\ \hline
**Intensive cooler** & \(16.4\pm 0.09\) & \(10.1\pm 0.015\) & \(0.61\pm 0.03\) & \(organic compounds passing through. HHV values for the second cut and the aqueous phase were found to be rather constant. The low values of the aqueous fraction were obviously due to water predominance in the composition. The average value for the bio-oil collected in the second condenser, which is the targeted liquid for the bio-fuel application, whether it is for combustion of the raw product or for the upgrading path, was shown to be significantly high (\(\simeq\)21.5 MJ kg\({}^{-1}\)).  
The targeted oil fraction (i.e., the second cut) presented highly considerable HHV, therefore, concentrating a significant share of energy that can be further transferred into fuels for transport after further upgrading, while the other two fractions should not be underestimated as to what concerns the potential precursors towards chemicals production.  
Finally, it was observed that the aqueous phase contains mainly light organic compounds such as acetic acid and phenol, which could be potentially extracted and further processed into bio-based commodity chemicals for several applications in the chemical industry [38; 63; 64].