Catalytic Hydrodeoxygenation of Bioderived C5 Acid into Motor Fuel Components: Kinetics and Mechanistic Study
C5 acid conversion through the intermolecular coupling into 5-nonanone with CO2 and water releasing followed by
hydrodeoxygenation into n-nonane over Pd and Pt catalysts in reductive atmosphere was studied. Spectroscopic methods (FTIR and UV-Vis in situ) were applied to study a feasible mechanism of ketonization still debated in the literature. Both catalytic reactions were explored separately in order to be performed thereafter in a cascade mode over the best bifunctional catalyst, which turned out to be Pt(Pd)/MxOy. Higher activity of ZrO2 and CeO2/ZrO2 in C5 acid decaboxylative coupling in H2 atmosphere compared to that in N2 was found. Kinetic regularities and size effect of 5-nonanone hydrodeoxygenation over Pd and Pt on Zr and Ce/Zr oxides was elucidated. FTIR and UV-Vis study allowed to identify different carboxylates adsorption forms and to reveal their key role in the ketonization mechanism. The reaction conditions were found provided C9 alkane yield more than 80%.