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用NMR及IR、TG-DTA等手段研究具有Keggin结构的磷钼钒系杂多酸在空气中的热稳定性。实验结果表明:合成的杂多酸在各个Keggin单元中具有不同的钒含量。样品的热稳定性与其钒含量有关.随着钒含量的增加,keggin结构的热稳定性逐渐降低,但H_4PMo_(11)V_1O_(40)具有比H_3PMo_(12)O_(40)还要高的热稳定性。由于钒的取代,钼钒磷酸的热分解过程不同于钼磷酸。失去结构水使Keggin结构遭到破坏,但在室温下与水重新作用可使钼钒磷酸的Keggin结构恢复。
The thermal stability of phosphomolybdic vanadium-based heteropolyacids with Keggin structure in air was investigated by means of NMR, IR and TG-DTA. The experimental results show that the synthesized heteropolyacids have different vanadium content in each Keggin unit. The thermal stability of the sample is related to its vanadium content. The thermal stability of the keggin structure decreases with the increase of vanadium content, but H_4PMo_ (11) V_10_ (40) has higher heat than H_3PMo_ (12) O_ stability. Due to the substitution of vanadium, the thermal decomposition of molybdovanadophosphoric acid is different from molybdophosphoric acid. The loss of structural water destroys the Keggin structure, but reactivates the Keggin structure of molybdovanadophosphoric acid at room temperature with water.