多元技术研究铌酸和磷酸铌的本征和有效酸度,Chemistry of Materials

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多元技术研究铌酸和磷酸铌的本征和有效酸度
Chemistry of Materials ( IF 7.2 ) Pub Date : October 25, 2005 , DOI: 10.1021/cm0512070
Paolo Carniti ₁ , Antonella Gervasini ₁ , Serena Biella ₁ , Aline Auroux ₁

Affiliation

铌酸（Nb ₂ O ₅ ·nH ₂ O）和磷酸铌（NbOPO ₄）的酸度性质为了获得有关其酸性位点的数量，强度和强度分布的全面信息，已通过不同的方法和在各种条件下对表面进行了研究。已经使用了四个具有不同碱性的碱基探针分子（氨，吡啶，2-苯乙胺和苯胺）。这些基本探针的气固和液固滴定法已经使用静态或动态吸附（与容量法关联的量热法，反应量热法，使用HPLC装置的脉冲流容量法）和解吸（热重分析）技术进行。将在真空或惰性气氛下测定的两种固体的固有表面酸度与在不同极性和性质的液体（癸烷，环己烷，甲苯，甲醇和异丙醇）中测得的有效酸度进行了比较。两个表面的有效酸度可能与它们在水相中果糖脱水反应中测得的催化活性有关。磷酸铌比铌酸具有更高的催化活性，这是因为即使在高极性和质子溶剂中，磷酸铌也具有较高的表面位点数量，从而保持了酸的特性。

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Intrinsic and Effective Acidity Study of Niobic Acid and Niobium Phosphate by a Multitechnique Approach

The acidity properties of niobic acid (Nb₂O₅·nH₂O) and niobium phosphate (NbOPO₄) surfaces have been studied by different methods and under various conditions in order to obtain comprehensive information about the number, strength, and strength distribution of their acid sites. Four base probe molecules of different basicities (ammonia, pyridine, 2-phenylethylamine, and aniline) have been used. Gas−solid and liquid−solid titrations by these basic probes have been performed, using static or dynamic adsorption (calorimetry linked to volumetry, reaction calorimetry, pulse flow volumetry using a HPLC apparatus) and desorption (thermogravimetric analysis) techniques. The intrinsic surface acidities of the two solids, determined under vacuum or inert atmospheres, were compared with the effective acidities measured in liquids of different polarities and proticities (decane, cycloexane, toluene, methanol, and isopropanol). The effective acidities of the two surfaces could be related to their catalytic activities measured in the fructose dehydration reaction in aqueous phase. The superior catalytic activity of niobium phosphate compared to niobic acid is related to its higher number of surface sites maintaining acid characteristics even in highly polar and protic solvents.

更新日期：2017-01-31

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