Effect of Zr/Si molar ratio and sulfation on structural and catalytic properties of ZrO2–SiO2 mixed oxides

Synthesis and characterization of novel ZrO2-SiO2 mixed oxides

“…This indicates that the synthesis methods used promoted a high dispersion of the ZrO 2 in the amorphous silica matrix 31,32,42,43 . As discussed in section 3.1, and suggested by the results of the X-ray diffraction, the pre-hydrolysis of the TEOS promoted the production of highly homogeneous materials.…”

“…The presence of sulfate ions in the micropores partially blocks the pores, makes them inaccessible to N 2 molecules, and consequently influences the size of the area. The increase in pore diameter can be linked to the presence of sulfate ions on the micropore walls, causing tension and rupture, followed by increased micropore volume and diameter 42 . The spectra in the infrared region shown in Figure 5 indicate the presence of a band at 1630 cm -1 that corresponds to scissor bending vibration of the H-O-H bond of the physisorbed molecular water 27,42,46,47 .…”

“…The increase in pore diameter can be linked to the presence of sulfate ions on the micropore walls, causing tension and rupture, followed by increased micropore volume and diameter 42 . The spectra in the infrared region shown in Figure 5 indicate the presence of a band at 1630 cm -1 that corresponds to scissor bending vibration of the H-O-H bond of the physisorbed molecular water 27,42,46,47 . The samples showed bands centered at 1078 cm -1 with a shoulder at ~ 1220 cm -1 due to the asymmetric Si-O-Si stretching vibrations of transverse-optical (TO 3 ) mode and the longitudinal-optic (LO 3 ) part stretching vibrations, respectively 47 .…”

ZrO2–SiO2 Mixed Oxides Xerogel and Aerogel as Solid Acid Catalysts for Solvent Free Isomerization of α-Pinene and Dehydration of 4-Methyl-2-Pentanol

“…ZrO 2 -SiO 2 mixed oxides have strong surface acidity and could be useful for diverse acid catalyzed reactions due to enhanced acidity as compared to less acidic individual zirconia or silica [11,12]. The acidity of mixed oxides may further be modified by the use of sulfation [5,10,13]. The enhanced surface acidity and catalytic activity resulting from sulfation is extensively studied in the case of pure zirconia [11].…”

“…The enhanced surface acidity and catalytic activity resulting from sulfation is extensively studied in the case of pure zirconia [11]. Influence of sulfation on the acidic properties of ceria-zirconia [10], zirconia-silica [5,9,13] and titania-silica [6,14] mixed oxides has also been reported.…”