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采用过量浸渍结合溶剂蒸发将12-磷钨杂多酸(TPA)分散于水合ZrO2干凝胶表面(以TPA质量分数表示的固载量为5～65 wt%),再经120～500℃空气气氛焙烧得到水合ZrO2固载磷钨杂多酸催化剂.借助等离子体原子发射光谱(ICP-AES)、物理吸附、X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱、吡啶吸附红外(Py-IR)光谱以及氨程序升温脱附(NH3-TPD)等手段对催化剂的组成、结构及酸性质进行表征,针对四氢呋喃(THF)开环聚合考察其酸催化性能.研究表明,在适宜的TPA固载量(35～45 wt%)及活化温度(120～300℃)条件下,TPA主要以畸变但结构未遭破坏的Keggin物种高度分散于水合ZrO2表面,赋予催化剂合适的酸性质及优良的催化性能.当TPA固载量过高时,部分TPA以体相物种析出;而当固载量过低或活化温度过高时,TPA的部分Keggin结构会发生分解.体相物种在THF极性体系中的严重溶脱或Keggin结构分解引起的酸性位大量丧失都使得材料的催化性能大幅度下降.催化剂重复使用实验显示,TPA固载量为45 wt%、300℃活化的催化剂具有良好的稳定性.
12-Tungstophosphoric acid (TPA) is dispersed on the surface of hydrated ZrO2 xerogel (5 to 65 wt% in terms of TPA mass fraction) by means of over impregnation combined with solvent evaporation, followed by 120 to 500 ° C air And calcined in an atmosphere to obtain hydrated ZrO2-supported phosphotungstic heteropolyacid catalyst. The surface morphology of the phosphotungstic heteropoly acid catalyst was characterized by means of plasma atomic emission spectrometry (ICP-AES), physical adsorption, X-ray diffraction (XRD), Fourier transform infrared (FTIR) Py-IR spectra and ammonia temperature-programmed desorption (NH3-TPD) were used to characterize the composition, structure and acidity of the catalysts. The catalytic properties of the catalysts were investigated by ring-opening polymerization of THF. Under the conditions of TPA loading (35-45 wt%) and activation temperature (120-300 ℃), the Keggin species, mainly in the form of distorted but unbroken structures, of TPA is highly dispersed on the surface of hydrated ZrO2, giving the catalyst proper acidity and excellent properties When the loading of TPA is too high, part of TPA is precipitated as bulk species, whereas when the loading is too low or the activation temperature is too high, some Keggin structures of TPA decompose. Acidic due to severe lysis in the sexual system or decomposition of the Keggin structure A large number of bits are lost so that the catalytic properties of the material significantly. Experiments show that catalyst can be reused, TPA solids loading of 45 wt%, 300 ℃ activated catalyst has good stability.