Nanosized solid superacids SO₄²⁻/TiO₂ and S₂O₈²⁻/TiO₂, as well as MCM-41-supported SO₄²⁻/ZrO₂, were prepared. Their structures, acidities, and catalytic activities were investigated and compared using XRD, N₂ adsorption-desorption, and in situ FTIR-pyridine adsorption, as well as an evaluation reaction with pseudoionone cyclization. The results showed that SO₄²⁻/TiO₂ and S₂O₈²⁻/TiO₂ possess not only nanosized particles with diameters < 7.0 nm, a BET surface greater than 140 cm²/g and relatively regular mesostructures with pores around 4.0 nm, but also a pure anatase phase and strong acidity. Different from the Lewis acid nature of SO₄²⁻/ZrO₂/MCM-41, SO₄²⁻/TiO₂ and S₂O₈²⁻/TiO₂ exhibit mainly Bronsted acidities. The strongest Bronsted acid sites were produced on SO₄²⁻/TiO₂ promoted with H₂SO₄, while Lewis acid sites on S₂O₈²⁻/TiO₂ even stronger than those on SO₄²⁻/ZrO₂/MCM-41 were generated when persulfate solution was used as sulfating agent. Because of their distinct acid natures, SO₄²⁻/TiO₂ and S₂O₈²⁻/TiO₂ exhibited catalytic activities for the cyclization of pseudoionone that were much higher than that of SO₄²⁻/ZrO₂/MCM-41. It can be concluded that the existence of more Brønsted acid sites was favorable for proton participation in the cyclization reaction.

中文翻译：

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SO ₄ ^2- / TiO ₂和S ₂ O ₈ ^2- / TiO ₂催化剂的制备与表征

制备了纳米级固体超强酸SO ₄ ^2- / TiO ₂和S ₂ O ₈ ^2- / TiO ₂，以及MCM-41负载的SO ₄ ^2- / ZrO ₂。利用XRD，N ₂吸附-解吸， 原位 FTIR-吡啶吸附以及假紫酮环化反应进行了研究，比较了它们的结构，酸度和催化活性。结果表明，SO ₄ ^2- / TiO ₂和S ₂ O ₈ ^2- / TiO ₂不仅具有直径小于7.0 nm的纳米级颗粒，大于140 cm ² / g的BET表面和相对规则的介孔结构以及约4.0 nm的孔隙，还具有纯的锐钛矿相和强酸性。与SO ₄ ^2- / ZrO ₂ / MCM-41的路易斯酸性质不同，SO ₄ ^2- / TiO ₂和S ₂ O ₈ ^2- / TiO ₂主要表现出布朗斯台德酸度。H ₂ SO ₄促进的SO ₄ ^2- / TiO ₂上产生最强的布朗斯台德酸位，而S ₂ O上的路易斯酸位在当使用过硫酸盐溶液作为硫酸化剂时，生成了比SO ₄ ^2- / ZrO ₂ / MCM-41上更强的₈ ^2- / TiO ₂。由于SO ₄ ^2- / TiO ₂和S ₂ O ₈ ^2- / TiO ₂具有独特的酸性质，因此它们对假紫罗酮的环化反应具有比SO ₄ ^2- / ZrO ₂ / MCM-41更高的催化活性。。可以得出结论，存在更多的布朗斯台德酸位点有利于质子参与环化反应。