Reaction of adsorbed carbon monoxide with hydrogen on magnesium oxide

Abstract

The reactivity of carbon monoxide adsorbed on magnesium oxide surfaces towards hydrogen has been examined by the temperature-programmed desorption (t.p.d.) technique and by i.r. spectroscopy. The surface species resulting from the reaction of adsorbed CO with H₂ in the temperature range 343–583 K gave t.p.d. peaks for CO and H₂ at 773 K. The t.p.d. profiles were in agreement with that of adsorbed formaldehyde but were totally different from that of adsorbed formic acid. The surface species showed i.r. features in the C—H stretching region and in the region 1700–1000 cm^–1. One set of the features in the latter region appearing at 1604 and 1370 cm^–1 could be attributed to formate.

Based on the t.p.d. profiles and i.r. spectra it is concluded that CO adsorbed on the MgO surface reacts with H₂ to form formyl (HCO) which is then adsorbed on the surface oxygen atoms to give formate (HCOO).