Acidity induced by H2S adsorption on unpromoted and promoted sulfided catalysts

Abstract

The effect of H 2 S adsorption on the nature and the number of acid sites of alumina supported sulfided catalysts was characterized by IR spectroscopy. For monitoring the variation of the surface properties, dimethyl-2,6-pyridine, a probe molecule more convenient to detect Bronsted acidity than pyridine, was adsorbed at room temperature (r.t.). Before H 2 S introduction, a few number of Bronsted acid sites was detected, particularly on the promoted catalysts. Whatever the catalysts, H 2 S adsorption at r.t. led to the creation of Bronsted acid sites at the expense of Lewis acid sites. The concentration of the created Bronsted acid sites depended on the presence and on the nature of the promoter. The highest number of Bronsted acid sites was detected on CoMo/Al 2 O 3 .