【摘要】 本工作改进了文献[4]报导的几种原料同时混合、加热煮沸合成的方法采用分步加入原料,控制反应温度、多次重结晶的方法合成了6、7、8个钒原子取代的钼钒磷杂多酸铵;并以铵盐为原料,用离子交换、冷冻分离和真空抽吸相结合的提纯方法制备了未见文献报导的相应的固体杂多酸;H₅[PMo₅V₇O_37.5]·xH₂O,H₆[PMo₄V₈O_37.5]·xH₂O。通过元素组成分析确定了它们的组成。这些杂多酸在水溶液、非水溶液中的电位滴定表明,杂多阴离子在分解前没有发生自电离、水解等情况,它们在水溶液中是稳定的。酸的碱度分别为5、5、6。通过纸上色谱实验,讨论了杂多酸的分解过程。由热重分析和溶解性实验得到它们的分解温度,本文还讨论了这些化合物的红外、紫外光谱,x光粉末衍射及极谱性质。光谱结果表明,它们可能具有Keggin结构,由导数脉冲极谱得到它们的峰电位。更多还原

【Abstract】 By the method of adding raw material stepwise and controlling the temperature of reaction about 80℃, the ammonium salts of molybdovanado-phosphoric acids with 6,7,8 vanadium atoms were prepared as crystalline solid. By the way of ion-exchange, the corresponding free acids were obtained first time with the salts as raw material: H5[PMo6 V6O38] xH2O, H5 PMo5 V7O37] xH2O, H6PMo4V8O37.5] xH2O. According to the chemical analyses, their composition were determined.The potentiometric titration measurements in the aqueous and non-aqueous solution with NaOH and NaOCH3 as titrant, respectively, showed that their alkalinities were 5,5,6. The process of the decomposition of heteropoly acids were studied. The temperatures of the decomposition of molybdovanado-phosphate compounds were obtained by the thermogravimetric analysis and solubility tests. Also, the UV, IR spectra, X-ray powder diffraction and polarographic properties were studied, These compounds seems to have the Keggin structure. The pulse polarographic experiments indicated that the moly-bdovanadophosphate anions with 6 vanadium atoms were reduced in three steps and with 7,8 vanadium atoms, in four steps. Their peak potentials Ep were Ep6: -0.30V, -0.54V, -0.98V; Ep7: -0.25V, -0.37V, -0.59V, -1.03V, Ep8:-0.22V, -0.34V, -0.55V, -1.00V.更多还原