Infrared spectroscopic studies of the hydrodeoxygenation of γ-valerolactone on Ni₂P/MCM-41

The hydrodeoxygenation (HDO) of the cyclic five-membered ester γ-valerolactone (GVL) was studied on a Ni₂P/MCM-41 catalyst. The activation of the passivated catalyst in H₂ was followed by in situ near-edge X-ray absorption spectroscopy (NEXAFS) which indicated reduction of the catalyst after 3 h at 550 °C. In situ infrared measurements under reactive H₂ and inert N₂ showed the presence of adsorbed GVL and pentanoic acid (PA) as the most abundant surface intermediates. The results supported a previous reaction network that showed that ring-opening of GVL to produce pentanoic acid was the rate-determining step. This was confirmed by transient infrared measurements which showed that the number of CH₂ groups in the adsorbed species increased under H₂ flow, consistent with PA formation but not an alkoxide. The results provide understanding of the key steps in the reaction mechanism.