Alkaline Earth Metal Oxides Doped with Alkali Metals Prepared by Impregnation

Alkaline Earth Metal Oxides Doped with Alkali Metals Prepared by Impregnation 

As stated above, a second route for the preparation of alkali-doped alkaline earth metal oxides is impregnation with aqueous solutions of alkali metal salts or hydroxides. As shown by Kijenski et al. (242), the resultant alkali metal-doped 

Driscoll et al. (259,266) concluded that the catalytically active species for OCM are Li -0 centers, which are equilibrated with surface 0 centers via hole transport, because vacant hole sites are formed by Li doping in the surface and bulk. However, direct observation of the Li -0 pairs is difficult, because they are present at high temperatures and are formed only in an O2 atmosphere (267). It has been reported that 0 species in other alkali-doped MgO catalysts are also active for OCM (265,268). 

Besides oxidative coupling of methane and double bond isomerization reactions (242), a limited number of organic transformations have been carried out with alkali-doped alkaline earth metal oxides, including the gas-phase condensation of acetone on MgO promoted with alkali (Li, Na, K, or Cs) or alkaline earth (Ca, Sr, or Ba) (14,120). The basic properties of the samples were characterized by chemisorption of CO2 (Table VI). 

Values of M represent a measure of the effect that the addition of 1 mol of A has on increasing the CO2 adsorption capacity of the MgO sample. 

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