Near-Surface Gas-Phase Methoxymethanol Is Generated by Methanol Oxidation over Pd-Based Catalysts

Abstract

Catalytic conversion of alcohols underlies many commodity and fine chemical syntheses, but a complete mechanistic understanding is lacking. We examined catalytic oxidative conversion of methanol near atmospheric pressure using operando small-aperture molecular beam timeof-flight mass spectrometry, interrogating the gas phase 500 μm above Pdbased catalyst surfaces. In addition to a variety of stable C 1−3 species, we detected methoxymethanol (CH 3 OCH 2 OH)a rarely observed and reactive C 2 oxygenate that has been proposed to be a critical intermediate in methyl formate production. Methoxymethanol is observed above Pd, Au x Pd y alloys, and oxide-supported Pd (common methanol oxidation catalysts). Experiments establish temperature and reactant feed ratio dependences of methoxymethanol generation, and calculations using density functional theory are used to examine the energetics of its likely formation pathway. These results suggest that future development of catalysts and microkinetic models for methanol oxidation should be augmented and constrained to accommodate the formation, desorption, adsorption, and surface reactions involving methoxymethanol.

The Far-Infrared Spectrum of Methoxymethanol (CH3–O–CH2OH): A Theoretical Study

“…12 Furthermore, it has been observed as a primary product of continuous methanol oxidation in the near-surface gas phase over all Pd- based catalysts where it is considered a key intermediate in the production of methyl format. 13 In addition to the astrophysical interest, methoxymethanol is involved in relevant atmospheric processes that originated from dimethyl ether (DME). The interest in the atmospheric chemistry of DME 1,14 and its derivatives is due to their use as diesel fuel substitutes since their emissions to the atmosphere might be harmful to the environment.…”

“…Experimentally, it is produced in ternary liquid mixtures of formaldehyde–water–methanol in the 298–383 K range of temperatures where methanol acts as a stabilizer . Furthermore, it has been observed as a primary product of continuous methanol oxidation in the near-surface gas phase over all Pd-based catalysts where it is considered a key intermediate in the production of methyl format …”

“… 12 Furthermore, it has been observed as a primary product of continuous methanol oxidation in the near-surface gas phase over all Pd-based catalysts where it is considered a key intermediate in the production of methyl format. 13 …”