# Glycerol Steam Reforming in a Pilot Plant: Effect of Temperature and Catalyst Load
## 3 Results and Discussion
### Comparison between Non-Catalytic and Catalytic Steam Reforming  
Finally, this final experiment was compared with a non-catalytic steam reforming under the same chemical conditions except for the temperature, which was increased by 100 \({}^{\circ}\)C in the case of the non-catalytic experiment. The main results regarding this comparison are included in Table 7:  
As observed, and even though both experiments were carried out at different temperatures, there was a considerable increase in the outlet gas flow when the catalyst was used, which points out the effectiveness of the Ni catalyst to carry out glycerol steam reforming, allowing the use of lower temperatures for this purpose. Thus, Ni was effective due to its properties, promoting the reaction between water molecules and carbon bounds in the water/glycerol mixture, producing higher and constant amounts of gas. Regarding hydrogen production, a considerable percentage of this gas (exceeding 40%) was found in the catalytic experiment, which proves the effectiveness of NiO to promote hydrogen production in the outlet gas. However, when the non-catalytic experiments at 950 \({}^{\circ}\)C were considered, the gas composition was equivalent to the catalytic experiment, as high temperatures promote hydrogen production and therefore its proportion in the final gas outlet. In any case, the catalyst addition allowed the reduction in the temperature reaction, with the subsequent saving on the energy cost. The same trend was observed when non-catalytic GSR was compared to other experiments where zeolite-based Ni catalysts were used, with \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Non-Catalytic Studies at 950 \({}^{\circ}\)C** & **Catalytic Studies at 850 \({}^{\circ}\)C** \\ \hline Outlet gas flow, L/min & 30.93 (\(\pm\)0.65) & 34.88 (\(\pm\)0.60) \\ Hydrogen content, \% & 41.72 (\(\pm\)0.20) & 41.35 (\(\pm\)0.15) \\ Power, kW & 6.32 (\(\pm\)0.15) & 8.63 (\(\pm\)0.25) \\ LHV, kJ/m\({}^{3}\)N & 12.27 (\(\pm\)0.90) & 14.84 (\(\pm\)0.85) \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Comparison between non-catalytic and catalytic glycerol steam reforming (reaction conditions: water to glycerol ratio = 0.7; inlet flow = 40 mL/min). Figure 11: SEM images of fresh (**a**) and used (**b**) catalyst. a considerable increase in the yield and hydrogen percentage for the latter [52]. Finally, the power and LHV were compared, observing a 36% and 21% increase in the power generation and LHV, respectively, when the catalyst was used at lower temperatures. Regarding the LHV, this considerable increase in the case of the catalytic study was possibly due to the use of low temperatures, which implied lower CO\({}_{2}\) amounts in the outlet gas and higher hydrocarbon and CO proportions (which are elements with a strong influence on the LHV). Concerning the power generation, as the outlet gas flow and LHV were higher when using NiO 12% as a catalyst, it is no wonder that the power, obtained by using Equation (6), was much higher compared to non-catalytic experiments. In view of the above and considering further studies about this subject, once the improvements carried out to the pilot plant were proven to be effective, a thorough sustainability assessment should be carried out to assure the sustainability of the process under these circumstances. Even though bio-based materials present obvious advantages compared to petroleum, they should not be taken for granted, and a rigorous scientific assessment of this subject should be carried out. Thus, advanced sustainability tools such as techno-economic, energy, exergy or life-cycle assessments, among others, should be considered in further studies with these results as a starting point. Moreover, these tools separately present some advantages and disadvantages and their integration was highly recommended according to a recent review work [53].