## 3 Results and Discussion  
### Effects of the Operating Conditions on the SCWG of Cellulose  
Table 1 shows the operating conditions and the reactor types employed in different studies on cellulose SCWG. As can be seen, all experiments were carried out at batch reactors and residence times of minutes. In the present study, different experiments were carried out in order to determine how different operating conditions had an effect on the process. Since SCWG is a complex reaction process, each individual gas yield (mmol/g of feedstock) was determined as the number of moles of each gas with respect to the initial amount of feed. All the experiments were carried out using three different residence times (6-10 s). Three experiments were made in duplicate, showing a good reproducibility. Moreover, multiple injections were made for all samples to establish the reproducibility of the results. The accuracy of those measurements was within \(\pm\)2%. The results from all the experiments are presented in Table 2. The hydrogen gasification efficiency percentage indicates the amount of hydrogen produced based on the hydrogen that could theoretically be obtained from the initial cellulose feed if a total gasification was achieved based on global gasification reaction (Equation (8)) [46]. As mentioned for Equation (9) [46], the total gasification amount would be 0.1482 g H2/g cellulose. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**T (\({}^{\circ}\)C)** & **P (MPa)** & **Feed** & \begin{tabular}{c} **Reaction** \\ **Time (Min)** \\ \end{tabular}  & **Reactor** & **Oxidant** & **Catalyst** & **Ref. ** \\ \hline
400–600 & 22–40 & 5.0–33.3 wt \% & 0–30 & \ \begin{tabular}{c} Quartz capillary tubes \\ (0.58 cm\({}^{3}\)) \\ \end{tabular}  & None & None & \begin{tabular}{c} None \\ (Ni/CeO2/Al2O3, \\ \end{tabular}  \\
400–550 & — & 12.5–25 wt \% & 30 & \ \begin{tabular}{c} Batch reactor (O.D of \\ 0.95 cm and a wall \\ thickness of 0.16 cm) \\ \end{tabular}  & None & KOH, calcined &
\begin{tabular}{c} [10]  
Global gasification reaction of cellulose:  
\[\text{C}_{6}\text{H}_{10}\text{O}_{5}+7\text{ H}_{2}\text{O}\leftrightarrow 12\text{ H}_{2}+6\text{ CO}_{2} \tag{8}\]  
Hydrogen gasification efficiency:  
\[HGE\ (\%)=\left[\left(\frac{g\ H_{2}}{g\ cellulose}\right)\right]\times 100 \tag{9}\]  
Naturally, the percentages that represent gasification efficiency could be over 100% in some of the experiments. This is because supercritical water acts as a reactant during the SCWG process, and, therefore, the amount of H\({}_{2}\) obtained in gaseous phase can be greater than the one fed into the process as a cellulose component. Moreover, a complex pattern of pathways comprises the complete SCWG process. Therefore, slight modifications with the theoretical calculation based on the global reaction can be obtained. While, the Lower Heating Values (LHV) of the gas products were calculated according to Equation (10), as already described [PERSON] et al. [47], which is based on the molar yields (mmol/g of feedstock) of H\({}_{2}\), CO and CH\({}_{4}\). The analysis of the different effects on the gasification reaction is explained in the sections below. \[LHV\left(\frac{\text{kJ}}{\text{Nm}^{3}}\right)=\left[\left(30\times CO\right)+ \left(25.7\times H_{2}\right)+\left(85.4\times CH_{4}\right)\right]\times 4.2 \tag{10}\] \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**T (\(\text{C}\)CO)**} & \multirow{2}{*}{
\begin{tabular}{c} **[Cellulose]** \\ **(g/L)** \\ \end{tabular} } & \multirow{2}{*}{**Oxygen** \\  & & & **Catalyst** \\  & & & **Tame (s)** \\  & & & & **Cellulose** \\ \hline  
3** & **61.67** \\ \hline \hline \end{tabular}  
* \(\text{n}\) = supplied oxygen/stoichiometric oxygen. When the amount of oxygen in the system matches the stoichiometric amount of oxygen that is required to completely oxidize all the cellulose fed into the system, the oxygen coefficient is unity (n = 1).  
\end{table}