Characterization and Catalytic Properties of Sulfated ZrO2–TiO2Mixed Oxides

Surface Characterization and Catalytic Activity of Alumina and Alumina-Supported ZnSO4Catalysts Prepared from Different Alumina Sources

“…The spectra of the ZnSO 4 -supported samples (not illustrated) were almost identical to those of the unsupported aluminas, the only difference being the presence of an additional peak at ca. 1230 cm -1 which has been assigned to asymmetric SO 4 stretching (Miller and Wilkins 1952). The intensity of this band was related to the ZnSO 4 content and was consequently smallest for samples containing 1.0 wt% ZnSO 4 .…”

“…Pore analysis of the investigated samples was carried out using the MP method (Mikhail et al 1967), from which the cumulative areas, S cum , and cumulative pore volumes, V cum , were computed (columns 6 and 7 of Table 1). The pore volume distribution curves for AN and ZnSO 4 -supported AN samples calcined at 773 K are depicted in Figure 5 as a representative series.…”

“…One of the most important roles of the alumina is to maintain a high dispersion of the active ingredients on its surface. This is feasible because the surface anionic OH groups of alumina interact strongly with the metal oxides during calcination (Matralis et al 1995), thus causing an extensive spread of the metal oxide over the surface.…”

“…The presence of F -ions increases both the number and strength of acid sites and also enhances the electron-acceptor properties. On the other hand, the high catalytic activity of catalysts modified with SO 4 2-ions is attributed to the enhanced acidity brought about by the inductive effect of the S=O bonds in the complex formed by the interaction of oxides with the sulphate ion (Sohn and Kim 1986;Bautista et al 1994;Morrow et al 1987;Wagif et al 1992;Lonyi et al 1996).…”

“…On the other hand, the dehydration of 1-butanol takes place on relatively weaker acid sites, while the skeletal isomerization of cyclohexene and isobutylene requires exceedingly strong acid sites (Tanabe et al 1978). Thus, in order to incorporate stronger acidity and a greater acid strength, single or binary oxide catalysts are often treated with small amounts of electronegative ions such as F -and SO 4 2- (Kerkhof et al 1980;Allenger et al 1987Allenger et al , 1991Sohn and Jang 1992;Sohn and Kim 1986;Bautista et al 1994;Morrow et al 1987;Wagif et al 1992;Lonyi et al 1996). There is general agreement that the fluoridation of alumina or other metal oxides improves the acidity of these catalysts for acid-catalyzed reactions (Kerkhof et al 1980; Allenger E-mail: faridsh@mans.edu.eg.…”