Molecular-Scale Perspective of Water-Catalyzed Methanol Dehydrogenation to Formaldehyde

Abstract

Methanol steam reforming is a promising reaction for on-demand hydrogen production. Copper catalysts have excellent activity and selectivity for methanol conversion to hydrogen and carbon dioxide. This product balance is dictated by the formation and weak binding of formaldehyde, the key reaction intermediate. It is widely accepted that oxygen adatoms or oxidized copper are required to activate methanol. However, we show herein by studying a well-defined metallic copper surface that water alone is capable of catalyzing the conversion of methanol to formaldehyde. Our results indicate that six or more water molecules act in concert to deprotonate methanol to methoxy. Isolated palladium atoms in the copper surface further promote this reaction. This work reveals an unexpected role of water, which is typically considered a bystander in this key chemical transformation.

The promotional role of water in heterogeneous catalysis: mechanism insights from computational modeling

“…DFT + U calculations showed that the activation barrier of hydrogen diffusion on the FeO surface significantly decreased from ~1.0 eV in the absence of water to ~0.2 eV in the presence of water, as depicted in Figure , which further confirmed the water‐mediated hydrogen diffusion mechanism. A similar water effect has also been reported by Flytzani‐Stephanopoulos et al in water‐catalyzed methanol dehydrogenation to formaldehyde . In this study, the dehydrogenation of methanol was assisted by an active complex consisting of several water and/or methanol molecules, which can bind hydrogen atoms of methanol and release them to the surface.…”

Evaluation of the Sorbent Properties of Single‐ and Multiwalled Carbon Nanotubes for Volatile Organic Compounds through Thermal Desorption–Gas Chromatography/Mass Spectrometry

“…Chemically,m ethanol can undergo dehydrogenation in the presenceo fc opper-containing residues in the CNTsa nd at high temperatures (300 8C) to yield formaldehyde. [28][29][30] Oxidation of methanol into formaldehyde can also occur when oxygen and oxideso fi ron, molybdenum, and vanadium are present at temperatures between 250 to 400 8C. [31] Formaldehyde can undergo furtherr eactions with alkenes such as the Prins reaction, aldol addition, and aldol condensation.…”

Carbon Monoxide Poisoning Resistance and Structural Stability of Single Atom Alloys

“…In several cases it has been shown that by doping the coinage metals with PGMs at very low molar fractions, such that these more reactive metals disperse as isolated single atoms in the surface layer of the host material, the activity of the coinage metal surface can be dramatically enhanced whilst retaining excellent reaction selectivity [11][12][13][14][15][16][17][18][19][20][21][22][23][24]. These single atom alloys (SAAs) of Sykes and co-workers exhibit tolerance to CO [18] and have been employed to catalyse hydrogenation [16][17][18][19][20], dehydrogenation [22,23], C-H activation and hydrosilylation [25] reactions with high activity and selectivity, as extended model surfaces and/or as real catalyst nanoparticles.…”

“…These single atom alloys (SAAs) of Sykes and co-workers exhibit tolerance to CO [18] and have been employed to catalyse hydrogenation [16][17][18][19][20], dehydrogenation [22,23], C-H activation and hydrosilylation [25] reactions with high activity and selectivity, as extended model surfaces and/or as real catalyst nanoparticles.…”