Sulfated Alumina Catalysts: Consequences of Sulfate Content and Source

Summary.

Consequences of the loading level of sulfate ions (3, 6, and 10-wt%) as well as the source of sulfate (H₂SO₄ or (NH₄)₂SO₄) on the structural, textural, and surface acid–base properties as well as the impacts on catalytic activity towards 2-propanol conversions on γ-Al₂O₃ and on aluminum hydroxide gel is described. Structural investigations of the catalysts by XRD revealed that the sulfation processes do not remarkably affect the γ-phase of alumina irrespective of the sulfate content or source. N₂-adsorption at 77 K indicated that sulfated gel catalysts exhibit the highest S _BET areas and, in general, S _BET for all catalysts were found to decrease with the increase of sulfate content, such a decrease is more pronounced for the 10% loaded catalysts. Pyridine adsorption as followed by FTIR indicated that sulfation of alumina increases the strength of its Lewis acid sites and creates Brønsted acidity in the case of highly loaded catalysts. The catalytic decomposition of 2-propanol in the gas phase indicated that, amongst all the catalysts investigated, the 6% loaded ones exhibited 100% activity (2-propanol conversion) and the highest propene (dehydration product) selectivity.