Mechanistic reaction micro-kinetics-based structure–activity relationships for palmitic acid hydrodeoxygenation over NiMoS /Al2O3 catalysts
Matej Žula, Miha Grilc, Blaž Likozar
Abstract
The kinetics of palmitic acid hydro-deoxygenation over sulfided NiMo/γ-Al2O3 have been described, including the gas–liquid–solid mass transport/surface chemistry in a magnetically-stirred batch reactor via temperature (225–275 °C), hydrogen pressure (30–70 bar) and catalyst loading (0.1–0.4 g) variation. Intermediates, the hexadecanol and palmityl palmitate, have been probed for a deeper physical understanding of mechanisms. Rates were used to show the impact of the continuum H2 thermodynamic phenomena, availability and coverages on the selectivity among the direct hydrogenation, hydrogenolysis and decarbonylation reactions through the role of H• formation dependent and independent changes. The system was reduced to 11 catalytic transformation steps, including 8 different molecular species, present in medium. Sequence is simulated to happen on the calculated functional number of active site structures, the activity of which was averaged, while the activation of H2 was supposed to initiate independently. The results of model integrate parameters, such as energies, constants and performance. Process was highly temperature-related, while H2 presence expressed linearly. Phases were characterized with temperature-programmed desorption analysis, coupled with mass spectrometry (TPD–MS) technique, transmission- (TEM), scanning electron microscopy (SEM), X-ray powder diffraction (XRD).