Water Formation in Non‐Hydrolytic Sol–Gel Routes: Selective Synthesis of Tetragonal and Monoclinic Mesoporous Zirconia as a Case Study. Issue 8 (30th November 2020)

• Record Type: Journal Article
• Authors: Wang, Yanhui; Bouchneb, Maroua; Mighri, Rimeh; Alauzun, Johan G.; Mutin, P. Hubert
• Is Part Of: Chemistry. Volume 27:Issue 8(2021)
• Page Start: 2670
• Page End: 2682
• Publication Date: 2020-11-30
• Subjects: catalyst support -- mesoporous materials -- nonhydrolytic sol–gel -- sol–gel processes -- zirconia; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202003081
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Several non‐hydrolytic sol–gel syntheses involving different precursors, oxygen donors, and conditions have been screened aiming to selectively produce mesoporous t‐ZrO2 or m‐ZrO2 with significant specific surface areas. The in situ water formation was systematically investigated by Karl Fisher titration of the syneresis liquids. XRD and nitrogen physisorption were employed to characterize the structure and texture of the ZrO2 samples. Significant amounts of water were found in several cases, notably in the reactions of Zr(O n Pr)4 with ketones (acetone, 2‐pentanone, acetophenone), and of ZrCl4 with alcohols (benzyl alcohol, ethanol) or acetone. Conversely, the reactions of Zr(O n Pr)4 with acetic anhydride or benzyl alcohol at moderate temperature (200 °C) and of ZrCl4 with diisopropyl ether appear strictly non‐hydrolytic. Although reaction time and reaction temperature were also important parameters, the presence of water played a crucial role on the structure of the final zirconia: t‐ZrO2 is favored in strictly non‐hydrolytic routes, while m‐ZrO2 is favored in the presence of significant amounts of water. 1 H and 13 C NMR analysis of the syneresis liquids allowed us to identify the main reactions responsible for the formation of water and of the oxide network. The morphology of the most interesting ZrO2 samples was further investigated by electron microscopy (SEM, TEM). Abstract : Water in non‐hydrolytic sol–gel : Monitoring in situ water formation in non‐hydrolytic sol–gel routes to mesoporous zirconia shows that it impacts not only the mechanism of the sol–gel process but also the structure of the final material.