Reaction Pathways of Methanol Reforming over Pt/a-MoC Catalysts Revealed by In Situ High-Pressure MAS NMR

Methanol reforming to hydrogen is a promising route for releasing hydrogen when it is used as a hydrogen carrier, but the reaction pathways are still in dispute. Herein in situ high-pressure MAS NMR rotors have been developed to reveal the reaction pathways of methanol reforming over Pt/a-MoC catalysts. Time-resolved in situ H-1 and C-13 MAS NMR spectroscopy was carried out to quantitatively monitor the evolution of H-2, CO2, and reaction intermediates. Notably, for Pt/a-MoC, in addition to CO derived from direct decomposition of methanol proposed for group 10 metal catalysts, formaldehyde is also an active intermediate that readily reacts with methanol or H2O and further transforms into methyl formate or formic acid, respectively, under high-pressure and lower-temperature conditions. Like the Cu-based catalyst, CO2 and H-2 were produced mainly through a formic acid mediated mechanism. Moreover, our present work has proven multinuclear high-pressure in situ MAS NMR to be a powerful tool for exploring reactions containing multiple phases (solid, liquid, and gas), and the vital insights related to the reaction mechanism.

Automated summary

In this study, in situ high-pressure MAS NMR rotors were developed to investigate the reaction pathways of methanol reforming over Pt/a-MoC catalysts. The results showed that, besides direct decomposition of methanol, formaldehyde is also an active intermediate that reacts with methanol or H2O and further transforms into methyl formate or formic acid. CO2 and H2 production mainly occurs through a formic acid mediated mechanism.