Efficient Conversion of Glycerol to a H₂ Rich Gas Mixture by Steam Reforming Over NiLaZr Catalysts

Glycerol is a side product of biodiesel production which is available in the world market at relatively low cost and could be used to obtain other valuable products. H₂ and H₂-CO mixtures can be obtained from glycerol by steam reforming using Ni based catalysts. NiLaZr catalysts prepared by a coprecipitation technique were tested in the steam reforming of pure glycerol. The tests were performed at 500 and 650 °C and at glycerol:water molar ratios 1:6 and 1:12. Glycerol conversion to gas phase products and H₂ yields were greatly improved with the increase of Ni loading from 5 to 15 %. The addition of 0.5 % of Rh is also very effective at low temperature to attain almost total glycerol conversions and high H₂ yields. The catalyst containing 15 % of Ni and the NiO and La₂Zr₂O₇ phases showed the best catalytic performance with glycerol conversion above 99 % and a H₂ yield close to the thermodynamic value at 650 °C. This catalyst also showed the best results in term of stability and low carbon formation. Fast deactivation of the Rh impregnated catalyst is ascribed to its ability to yield carbon by dissociation of C–C and C–H bonds in glycerol and other C1–C3 intermediates. Carbon morphology is greatly influenced by Ni interactions with the rest of the catalyst structure.