Acidities of sulfate species formed on a superacid of sulfated alumina

✍ Scribed by Tien-syh Yang; Tsong-huei Chang; Chuin-tih Yeh

• Book ID: 104423201
• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 686 KB
• Volume: 115
• Category: Article
• ISSN: 1381-1169
• DOI: 10.1016/s1381-1169(96)00283-x

✦ Synopsis

Sulfated alumina was prepared by impregnating y-Al,O, with aqueous H,SO,. Various sulfate species formed in these samples depended on the concentration of HaSO ([H2S04]). Three sulfate species, i.e., surface sulfate, multilayer sulfate and crystallized Al,(SO,), could be clearly identified by the DTG peaks at ca. 95O"C, 630°C and 8OO"C, respectively. Surface sulfates were the main sulfate species at [H2S04] I 0.8 M and induced Lewis superacidic sites (Ha < -13.8). The superacidic sites were also characterized by a NH,-TPD peak around 400°C and showed a catalytic activity towards n-butane isomerization.

When [H,SO,] > 0.8 M, multilayer sulfates were additionally formed, which created weaker Bronsted acid sites with a NH,-TPD peak around 250°C and a negligible activity towards n-butane isomerization. Until [H,SO,] > 2.4 M, neutral crystallized Al&SO,), was formed concurrently with the surface and the multilayer sulfates.