Abstract
Nowadays, the massive production of biodiesel leads to a surplus of glycerol. Thus, new applications of this by-product are being developed. In this study, glycerol steam reforming was carried out with Ni catalysts supported on Al2O3 rings and La-modified Al2O3. The catalysts were characterized by N2 physical adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and thermogravimetry. Both catalysts were effective in glycerol steam reforming. However, Ni/Al2O3 activity decreased over reaction time. Ni/La2O3/Al2O3 showed the best stability during the reaction. In addition, the activity of the modified support, La2O3/Al2O3, was evaluated. The modification of the support lent catalytic properties to the solid. Some conditions such as catalyst arrangement (catalyst in the first or second reactor), space velocity, and reaction temperature were studied. The highest hydrogen production was obtained when half the amount of the catalyst was located in both reactors. Glycerol conversion into gases was similar, regardless the space velocity, although higher amounts of H2 were obtained when this variable decreased. Complete glycerol conversion into gases was obtained at 900 and 1000 °C, and hydrogen production reached a H2/glycerol molar ratio of 5.6. Finally, the presence of the catalyst and the optimization of these conditions increased the energy capacity of the produced stream.
Highlights
Due to the need of alternative energies in recent years, biodiesel as an alternative fuel has shown a rapid increase in its production [1,2]
Several ways to valorize this by-product are being researched such as the production of chemical products, its use as a fuel additive, or its co-digestion; whereas one of the most promising chances is to produce hydrogen or syngas via steam reforming [3,4,5,6,7,8]
As seen in the reaction of the steam reforming of methane plus the water–gas shift reaction, the maximum amount of hydrogen would be four moles per mole of methane, whereas up to seven moles could be obtained per mole of glycerol, as shown in Equation (1)
Summary
Due to the need of alternative energies in recent years, biodiesel as an alternative fuel has shown a rapid increase in its production [1,2]. This has resulted in the production of huge amounts of glycerol (C3 H8 O3 ) as by-product in biodiesel synthesis. Several ways to valorize this by-product are being researched such as the production of chemical products, its use as a fuel additive, or its co-digestion; whereas one of the most promising chances is to produce hydrogen or syngas via steam reforming [3,4,5,6,7,8]. Biodiesel processing plants would add an interesting step by the conversion of glycerol into hydrogen [8]
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