New W-doped nickel aluminate catalysts in the glycerol hydrodeoxygenation (HDO)

Biorefineries are emerging as an important pillar for achieving both sustainable energy and chemicals. Bio-derived feedstocks are extremely various, but one of the most relevant building block chemicals coming from them is glycerol. Glycerol is an interesting molecule to be valorised because of its high functionalization degree and the huge surplus obtained from biodiesel production. Among all the possible valorisation routes, the catalytic Aqueous-Phase Hydrodeoxygenation (APHDO) allows to combine two processes (APR and HDO) and to overcome the issues related to normal glycerol HDO, conducted with external and high-pressure H2, by producing H2 in-situ via APR on part of the reactant itself. This thesis work is focused on the development of a new catalytic system for the APHDO based on Ni, known to be active on APR, and doped with W, which increases the acidity of the system and makes it active towards HDO. Effects of dopant loading, synthesis method and space velocity were evaluated. To evaluate the effect of doping, four catalysts with different W loadings were synthetised via sol-gel method, characterised through a wide range of analytical techniques (XRD, XRF, H2-TPR, NH3-TPD, N2 physisorption and H2 chemisorption), and their catalytic activity was tested in a continuous tubular reactor, at 235 °C and 45 bar. Afterwards, the catalyst that showed the best performance among them was prepared through impregnation method and was characterised and tested as before. Finally, the Weight Hourly Space Velcoity (WHSV) effect was studied by conducting the process under the same conditions and with a doubled glycerol feeding flow. W-doping resulted to be effective in HDO activation, giving low values of carbon conversion to gas, and the catalytic performance resulted to be influenced by the preparation method. Low WHSV values resulted to be better for a good interaction between the substrate of the reaction and the catalyst.