The Isomerization of Propylene Oxide on Metal Oxides and Silica-Magnesia Catalysts

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Abstract
The isomerization of propylene oxide was carried out over silica-magnesia catalysts and metal oxides at 260–270°C using a pulse reactor. The main products of the reaction were propionaldehyde, acetone, allyl alcohol, 1-propanol, and acrolein. Propionaldehyde and acetone are produced on acidic and basic sites respectively. Allyl alcohol is formed over acid-base bifunctional catalysts. 1-Propanol and acrolein are mainly produced through hydrogen-transfer reactions between allyl alcohol and propionaldehyde and propylene oxide. As regards these reactions, acid-base bifunctional catalysts are favorable and the reaction rate depends on the electron-donating power of the hydrogen acceptor and the basic strength of the catalyst. The acid sites on silica-magnesia catalysts are attributed to the forsterite produced by the reaction of magnesium oxide and silica gel, and the basic sites, to the magnesium oxide remaining. The metal oxides, such as magnesium and calcium oxides, are considered to have very weak acid sites.