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This post was last edited by Maimai on 2025-1-13 at 15:14. Solid acid and base catalysts possess significant advantages such as high catalytic efficiency, no corrosivity, no pollution, easy separation, and the ability to be recycled, making them important tools for achieving green and sustainable production. Zirconia is currently the only metal oxide known to possess four distinct properties: acidity, alkalinity, oxidizing ability, and reducing ability. These unique properties are widely utilized in catalysis. It is also a p-type semiconductor that readily generates oxygen holes; through special treatments such as sulfation and tungstate treatment, strong interactions can be induced, allowing the preparation of solid superacids such as zirconium sulfate SO42- / ZrO2 and zirconium tungstate WO3/ZrO2. Zirconia in both monoclinic and tetragonal phases possesses both acidic and basic sites, and it exhibits catalytic activity; the catalytic activity of the monoclinic phase is higher than that of the tetragonal phase. On monoclinic zirconia, acidic and basic sites are closely arranged, whereas in the tetragonal crystal system they are separated. Therefore, the density of acidic and basic sites in monoclinic zirconia is higher than that in tetragonal zirconia, which can also be interpreted as meaning that monoclinic zirconia is more basic than tetragonal zirconia. This is also reflected in some reactions, where different main products are catalytically formed on various crystalline forms of zirconia. The dehydration of 1,4-butanediol to form 3-butene-1-ol occurs on monoclinic zirconia, while **furan THF is more readily formed on tetragonal zirconia. The catalytic behavior of zirconia ZrO2 is often explained by its amphoteric properties, and it exhibits high catalytic activity for many reactions, such as the dehydration of secondary alcohols, the hydrogenation of dienes, the isomerization of 1-butene, and the ketonation of aldehydes and carboxylic acids. (The reaction mechanism for the conversion of benzoic acid to benzaldehyde on ZrO2) Zirconium oxide ZrO2 can be used as a catalyst for the conversion of benzoic acid to benzaldehyde. At a reaction temperature of 623 K, the reaction system achieved 51% conversion and 97% selectivity. The active site of the reaction is generally understood in terms of the synergistic effect of adjacent ion pairs. The basic site extracts an H+ from the carboxylic acid to form a bidentate carboxylate anion; H2 dissociates on the adjacent ion pair to yield H+ and H-. The carboxylate anion reacts with H- to produce an aldehyde, leaving O2- attached to Zr4+. This O2- then reacts with the two H+ atoms on the oxygen atom remaining on the surface to form H2O, which leaves the solid surface.