Abstract
•Catalytic systems for the reformation of glycerol and production of renewable hydrogen.•Modification of Ni catalysts to improve their activity at low temperatures and enhance their resistance to deactivation.•Type of products defined by the support at low temperatures.•Utilization and valorization of biodiesel by-product as hydrogen and chemicals source.
Glycerol, a by-product of biodiesel industry, could be utilized for the production of synthesis gas or hydrogen via steam reforming. Ni/Al2O3 catalysts are efficient for this process but could be improved regarding their activity at low temperatures, selectivity toward hydrogen production and stability with time-on stream. In the present work, the effects of addition of Β2Ο3 and La2O3 on Ni/Al2O3, on the physicochemical characteristics and catalytic performance are investigated. N2 adsorption–desorption, XRD, UV–vis DRS, TPR, NH3-TPD and HR-TEM were employed for the evaluation of the textural and structural properties of the catalysts, while quantitative assessment of the carbonaceous deposits was performed using TPH-TPO. Catalytic behavior was investigated in the temperature range of 400–800°C. In the absence of metal, the support presents considerable activity for the dehydration reactions and influences selectivity to oxygenate products. The catalytic behavior of the bare carriers seems to be dictated by their surface acidity.
The presence of Ni enhances significantly catalytic activity and promotes the production of gaseous products, mainly carbon oxides and hydrogen. Conversion to gas-phase products and hydrogen yield are enhanced by the addition of La2O3 to the support while the opposite is observed upon addition of B2O3. These differences are more pronounced at lower temperatures. Lower amount of graphitic carbon was formed on NiLaAl at all temperatures. However, this catalyst has not been proven more stable than the unmodified NiAl, mostly due to its poorer textural properties.