Activity of Alkaline Earth Metal Oxides

Alkaline earth metal oxides are active catalysts for double bond isomerization. For example, SrO exhibits high activity and selectivity for the isomerization of a-pinene to /1-pinene 110). MgO and CaO have excellent activities for isomerization of 1-butene and 1,4-pentadiene and, particularly, for isomerization of compounds containing heteroatoms, such as allylamine or 2-propenyl ethers 111-115). Recently 

As in the case of double bond isomerization of butenes, the double bond isomerization of VBH is considered to be initiated by abstraction of an allylic proton from a tertiary carbon atom to give an allylic anion that may be stabilized by metal ions, yielding the E- and Z-EBH isomers. 

Baba and Endou 117) reported that CaO is an active catalyst for isomerization of VBH to EBH when it is evacuated at temperatures above 800 K, whereas MgO did not show any activity for this process. However, some discrepancies have been reported by Kabashima et al. 10), who found that MgO, CaO, SrO, and BaO catalyze the isomerization of VBH to EBH, with the order of activity being CaO MgO SrO BaO. This order in activity is attributed to the trends in base strength of oxides (BaO SrO CaO MgO) and the surface area, the latter decreasing in the order MgO CaO SrO BaO (Table II). The activity of the CaO was the highest among these alkaline earth metal oxides, and the activity of the MgO varied with the pre-treatment temperature, reaching a maximum it was 873 K  

Results Characterizing Isomerization of VBH to EBH on Alkaline Earth Metal Oxide Catalysts in a 

Catalyst Pretreatment temp (K) Surface area (m /g) Reaction temp (K) Time (min) Conversion (%) E/ ratio 

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