Infrared Study of the Adsorption of Methanol and Ethanol on Magnesium Oxide

Abstract

The adsorbed species which result when magnesia is exposed to methanol or ethanol vapor are reported. Five different surface species have been identified for both methanol and ethanol. At 25°C a tightly bound layer of liquid alcohol is observed. When this is removed by heat and evacuation, another species appears which is identified as a surface methoxide in the case of methanol and ethoxide in the case of ethanol. When the magnesia sample is heated to 165°C in alcohol vapor, a formatelike surface compound is formed from methanol and an acetatelike compound from ethanol. At temperatures near 430°C, two more surface species are observed to form after the disappearance of surface formate (or acetate). They are identified as a surface methyl carbonate from methanol (ethyl carbonate from ethanol) and surface carbonate which is formed from both methanol and ethanol. Both the surface alkyl carbonate and surface carbonate are attributed to a low-temperature (<240°C) reaction between surface alkoxide and CO2 which is liberated by dicarboxylation of the surface carboxylate. The interpretation of surface structures has been checked by using CD3 methanol and 13C enriched methanol. Proposed mechanisms for the formation of the different surface species (followed by mass spectrometry) are discussed.

The mechanism for the synthesis of 1-methoxy-2-propanol from methanol and propylene oxide over magnesium oxide

“…The new OH group that formed from the dissociative adsorption gave rise to broad bands near 3600 cm À1 . When the adsorption temperature reached 393 K, new bands appeared at 1599 and 1394 cm À1 , these could be ascribed to the transformation of methoxide species into formate ions [19,20]. However, for methanol adsorbed on CaO (see Fig.…”

In situ investigation of MgO nanocube deformation at room temperature

“…This method precludes the use of solvents that may modify the surface structure of MgO samples [47]. Since the nanocubes exhibit h1 0 0i surfaces, the compression axis is expected to be parallel to [0 0 1].…”

Solid base and their performance in synthesis of propylene glycol methyl ether

“…Junko Kondo et al [23] reported similar results, which were attributed to two kinds of methoxide species. The new OH group formed from the dissociative adsorption gave rise to broad bands near 3500 cm −1 .When the adsorption temperature reaches 393 K, new bands appeared at 1599 and 1394 cm −1 , which could be ascribed to the transformation of methoxide species into formate ions [24,25]. Fig.…”