Synthesis of a Novel Highly Active NiMoO4 Nanocatalyst for the Sustainable Production of Anhydrous Formaldehyde from the Non-oxidative Dehydrogenation of Methanol at Relatively Low Temperature

The production of formaldehyde (FA) and clean hydrogen gas via the non-oxidative dehydrogenation of methanol is seen to be a promising approach where the anhydrous formaldehyde is an ideal for using in the subsequent manufacture of oxygenated synthetic fuels. In this investigation, NiMoO₄ with nanoaggregates morphology was synthesized by hydrothermal method in presence of triethylamine (TEA) as a surfactant and tested for the non-oxidative catalytic dehydrogenation of methanol into formaldehyde at relatively low temperature. Structural, morphological and textural properties were characterized by TGA, DSC, XPS, XRD, FT-IR, HR-TEM, pyridine-TPD and N₂-sorption assessments. Results of XRD verified the coexistence of mixed phases of both α and β-NiMoO₄. The catalysts' texture, structure, acidity and catalytic activity were greatly influenced by the introduction and the molar ratio of TEA. The variation of catalytic activity is strongly associated to the variation in S_BET and acidity. Activity results revealed that catalyst with Ni:TEA ratio of 1:1 (N₁T₁) was the most active catalyst with methanol conversion of 96% and selectivity to FA of 95% at reaction temperature of 325 °C. The outstanding catalytic performance of this catalyst is due to the presence of weak and intermediate strength Brønsted acidic sites on its surface. This catalyst showed remarkable stability for the synthesis of anhydrous formaldehyde over a 160 h period while maintaining the same conversion and selectivity.

Graphical Abstract