Synthesis and characterization of nanocrystallite MgAl₂O₄ spinels as catalysts support

MgAl₂O₄ spinels for use as Pt-Sn catalysts support for propane dehydrogenation were prepared by traditional coprecipitation techniques with nitrate salts as precursors and ammonia or ammonium carbonate as precipitating agent. Increasing pH from 10-12 decreases pore diameters but increases the surface areas of the samples when ammonium carbonate is the coprecipitation agent. A more basic media results in compositions close to that of stoichiometric spinel. In the coprecipitating samples, the crystalline size of the cubic crystals is uniformly distributed in the range from 7 to 14 nm. With wet mixing, however, both needle-shape and cubic crystals 10 to 100 nm appeared, indicating that it is necessary to produce spinels at higher calcination temperature.