Example of Magnesium Oxide as Catalyst

The electron-donor centers on metal oxides can be measured by adsorbing certain organic molecules on the surface of the oxide. The transfer of an electron from the donor site of the oxide to the adsorbed molecule creates a paramagnetic ion detectable using electron paramagnetic resonance (EPR) spectroscopy. Che et al. (1972) studied the adsorption of tetracya-noethylene (TCNE) on MgO that had been pretreated between 100 and 800°C. Using EPR methods they identified the presence of adsorbed TCNE radical anion. As the pretreatment temperature increased from 100 to 800°C, the concentration of the radical anion passed through two maxima, one at 200°C and the other at 700°C. The electron-donor centers were found to be associated with OH and O ions with a low coordination number. 

The isomerization of 1-butene (CH2=CH—CH2—CH3) over magnesium oxide has been studied by Baird and Lunsford (1972) as a function of pretreatment temperature, which was varied from 300 to 900°C. The results showed that the isomerization reaction was dependent upon pretreatment temperature, as was the initial cis/trans ratio of the product 2-butene (CH3—CH=CH—CH3). The reaction rate was also found to pass through a maximum at 700°C. The proposed mechanism is that lbutene adsorbs onto the MgO surface where O2- ions on corner sites aid in removing an allylic proton and transferring it to the terminal methylene group. 

---