# Glycerol Steam Reforming in a Pilot Plant: Effect of Temperature and Catalyst Load
## 3 Results and Discussion
### Lifetime Determination of Final Catalysts under Optimum Conditions  
One of the main problems related to the use of catalysts in steam reforming is the possibility of deactivation during the reaction due to different factors, such as poisoning caused by impurities such as hydrogen sulfide, coke deposition due to hydrocarbon decomposition or sintering of the active phase on account of high temperatures. These problems provoke the decrease in active sites or active areas on the catalyst surface, implying the continuous efficiency loss of the catalyst. Thus, the use of promoters (such as Ce, Zr or La, in this case, which improved catalyst basicity, metal-support interaction and Ni dispersion, as was proved in similar studies [47]) or mild reaction conditions could lengthen the useful life of catalysts [30; 48; 49]. Thus, in order to determine the lifetime of the selected catalyst (12% NiO and 5% La\({}_{2}\)O\({}_{3}\)), an experiment including the selected reaction conditions according to previous sections (that is, W/G = 0.7; inlet flow = 40 mL/min; oven temperature = 850 \({}^{\circ}\)C) was carried out,  
Figure 9: Comparison of power and LHV obtained in glycerol steam reforming at different temperatures and catalyst concentrations (reaction conditions: water to glycerol ratio = 0.7, inlet flow = 40 mL/min). monitoring the gas composition every 30 min for at least 10 h. As a result, as observed in Figure 10, there was a slight change in the H\({}_{2}\), CO and CO\({}_{2}\) composition at around 580 min, possibly due to the lower influence of the WGS reaction (mainly responsible for changes in the syngas composition). At this moment, it is possible that the catalyst did not promote this secondary reaction. On the other hand, the remaining gases (CH\({}_{4}\), C\({}_{2}\)H\({}_{4}\) and C\({}_{2}\)H\({}_{6}\)) come from the thermal decomposition of glycerol, and that is the reason why their mole fraction is not altered at this point. Consequently, and even though the activity of the catalyst seems to be considerable after 700 min (especially concerning glycerol thermal decomposition), it should be noted that the changes in the gas composition observed from 600 min should be taken into account, especially concerning further syngas processes or purification techniques where the gas composition plays a vital role when it comes to the industrial design. In previous studies, where Ni-La/Al\({}_{2}\)O\({}_{3}\) was produced and characterized, the catalyst obtained (16% NiO and 5% La\({}_{2}\)O\({}_{3}\)) offered a high stability, with a minimum reusability of five times [44]. Other studies based on Ni/CeO\({}_{2}\)/Al\({}_{2}\)O\({}_{3}\) showed great catalytic stability (with a considerable H\({}_{2}\) production up to 10 h), possibly due to the inhibition effect due to Ce, used as a promoter [30]. Equally, Ni-CeO-based catalysts for glycerol steam reforming offered longer useful times, up to 35 h [40]. Similar catalysts (15% Ni-CaO/Al\({}_{2}\)O\({}_{3}\)) studied in the literature showed a decline in catalytic conversion after 15 h at lower temperatures (700 \({}^{\circ}\)C) [46]. Also, other works covered the catalytic activity of Ni-La-Ti mixed oxide catalysts for glycerol steam reforming, observing that there was a slight and continuous decrease in activity, possibly due to coke deposition on the catalyst [50]. Other studies pointed out the long stability of the hydrogen selectivity (up to 12 h) of the catalyst used for GSR (Ni/CeZrO) at 500 and 600 \({}^{\circ}\)C [51].