Effect of crystallization mode of hydrous zirconia support on the isomerization activity of Pt/WO3–ZrO2

Nature of Catalytically Active Sites in the Supported WO3/ZrO2 Solid Acid System: A Current Perspective

“…Tungstated zirconia catalysts have been examined for acid-catalyzed vapor-phase reactions ( n -butane isomerization, dehydration of glycerol to acrolein, , SCR of NO x with NH 3 , and SCR of NO x with CO) and liquid-phase reactions (esterification of acetic acid with methanol, esterification of acetic acid with 1-heptanol, transesterification of triacetin and methanol, hydration of cyclohexene, synthesis of acetyl salicylic acid, reduction of the viscosity of heavy oil, hydrolysis of cellobiose, fructose conversion into 5-HMF, conversion of glucose to 5-HMF, alkylation of catechol with tert -butyl alcohol, solvent-free acetalization and ketalization, conversion of cellulose to hexanedione, palmitic acid esterification, synthesis of levulinic acid esters, oxidative desulfurization of thiols, and oxidation of styrene). Additionally, novel syntheses have been reported in an attempt to prepare superior solid acid tungstated zirconia catalysts (mesoporous Zr-WO x /SiO 2 , aerogel and xerogel WO 3 /ZrO 2 , mesoporous nano-WO x /ZrO 2 , ,, MOF-derived tungstated zirconia, two-phase interface hydrolysis, metal oxide promoted WO x /ZrO 2 , ,− precious-metal-promoted WO x /ZrO 2 , ,− and ZrO 2 -supported tungstaphosphoric acid polyoxo-metalates). Many of these studies claim that their novel syntheses result in superior tungstated zirconia catalysts.…”

MOF-Derived Tungstated Zirconia as Strong Solid Acids toward High Catalytic Performance for Acetalization

“…Moreover, higher calcination temperature will convert t-ZrO 2 to m-ZrO 2 , and surface WO x agglomerates into monoclinic WO 3 crystallites. As previously reported, tetragonal ZrO 2 is a more active support than m-ZrO 2 for WZ solid acids, and amorphous polytungsten species are the catalytic active sites in the supported catalysts while inactive WO 3 crystallites suppress the acid-catalyzed performance of WZ. , …”

“…Furthermore, coinciding with the XRD result for UiO-3-650, crystalline WO 3 NPs are formed at higher density of surface WO x species, while WO 3 NPs show two symbolic Raman bands at 805 and 714 cm –1 . In conclusion, fewer WO x species cannot completely inhibit intercrystallite accumulation into m-ZrO 2 by reducing the rate of ZrO 2 surface diffusion (UiO-1-650), and too much tungsten species lead to the formation of monoclinic WO 3 crystallites (UiO-3-650) …”

Preparation, Characterization, and Isomerization Catalytic Performance of Palladium Loaded Zirconium Hydroxide/Sulfated Zirconia

“…Here, Z, ZH, ZNH, and AZNH are calcined at series temperature for 3 h and are denoted as Z T , ZH T , ZNH T , and AZNH T , where T means the calcination temperature. The crystalline phase of a series of samples calcined at 500 °C was measured by the Raman spectroscopy, which was more sensitive to the surface property, as shown in Figure . The Raman bands appear at 176, 336, 373, and 469 cm –1 and can be assigned to monoclinic ZrO 2 , and the bands located at 325 and 640 cm –1 can be attributed to tetragonal ZrO 2 . , From Figure , it could be seen that the ZH500 and ZNH500 had a weaker crystalline phase than Z500, especially the monoclinic ZrO 2 , implying fewer chemical hydroxyl groups, and formed a colloidal network structure that could delay the crystallization.…”

“…Here, Z, ZH, ZNH, and AZNH are calcined at series temperature for 3 h and are denoted as ZT, ZHT, ZNHT, and AZNHT, where T means the calcination temperature. The crystalline phase of a series of samples calcined at 500 °C was measured by the Raman spectroscopy, which was more sensitive to the surface property, 32 as shown in Figure 5. The Raman bands appear at 176, 336, 373, and 469 cm −1 and can be assigned to monoclinic ZrO 2 , and the bands located at 325 and 640 cm −1 can be attributed to tetragonal ZrO 2 .…”