Properties of Magnesium Oxides Prepared from Various Salts and Their Catalytic Activity in 1-Butene Isomerization

Abstract

Abstract The basicity, one-electron donor property, and surface area were examined on the magnesium oxide catalysts prepared from six different kinds of magnesium salts. Magnesium oxide prepared from magnesium nitrate, oxalate, and acetate exhibited strong basicity and relatively large surface area and, on the other hand, MgO prepared from magnesium chloride, carbonate and sulfate had relatively weak basicity and small surface area. Number of one-electron donor centers hardly changed in the variety of magnesium oxides, except the one prepared from magnesium chloride. Magnesium oxide prepared from chloride showed both the lowest basicity with less strength than H−=15.0 and surface area in the six kinds of catalysts. In order to examine the influence of remaining anions in MgO a variety of catalysts were prepared by the addition of ammonium chloride, sulfate, and carbonate, respectively in MgO prepared from the nitrate. Ammonium chloride brought the greatest influence on the basicity, one-electron donor property, and surface area. Thus the remaining chloride ion greatly affected such properties as cited above. Sodium nitrite which decomposes at higher temperature than 320 °C was added to the magnesium oxides for the examination of the effect of the sodium cation. The amount of the basicity with a moderate strength (H−=15.0–22.3) increased by the addition of NaNO2. This was ascribed to the formation of the moderate strength of basicity by the interaction of Na2O, one of the decomposed products of NaNO2 and MgO. Isomerization of 1-butene was carried out on the six kinds of catalysts at 30 °C. The magnesium oxides prepared from nitrate, oxalate, and acetate salts (group A) exhibited isomerization activity and the ones from chloride, sulfate, and carbonate (group B) did not entirely. The isomerization activity could be correlated with the stronger basicity than H−=22.3. Temperature pregrammed desorption curves of acetic acid adsorbed on the catalysts indicated two peaks at around 350 and 420 °C in group A catalysts and only one at 350 °C in group B. The desorbed peak at around 420 °C was assigned to the adsorbed acetic acid on the stronger basic sites than H−=22.3.