【摘要】 V₂O₅与SnO₂构成的二元氧化物与单氧化物的性质很不相同,在所用实验条件下,V:Sn=1:2.1且及1:4.5（原子比）的样品具有较高的催化氧化活性。XRD实验证明:上述样品中SnO₂的作用主要是为钒离子的分散提供骨架,从ESR的结果可以看出:SnO₂的骨架有利于V⁴⁺的存在,氧化钒在SnO₂中的分散作用还引起了 V=O及 V—O—V 红外吸收带的消失及622.7cm^-1金属—氧键 IR吸收带的加宽和蓝移,由此设想可能生成了比 V—O—V键弱的V—O—Sn键,因而晶格氧的活动性得以增强,样品的V ⁴⁺含量与其对甲苯选择氧化的催化活性之间有平行关系。Mossbauer谱实验证明:不论在制备所得样品中或是在反应条件下处理所得样品中,Sn⁴⁺的氧化态都没有可觉察的变化,V₂O₅-SnO₂二元氧化物用于甲苯催化氧化的redox过程是通过V⁵⁺与V⁴⁺之间的电子传递及晶格氧的消耗与补充实现的。更多还原

【Abstract】 The binary oxides V2O5-SnO2 show a series of properties different from that of single oxides. The samples with V:Sn= 1:2.1 and 1:4.5 (atomic ratio) displayed high catalytic activities under the experimental condition used. The main role of SnO2 in above samples is to provide a host lattice for the dispersion of vanadium ions as proved by XRD. ESR results showed that the lattice of SnO2 is favourable for the existence of V4+. Moreover, the dispersion of vanadium oxide in SnO2 caused the disappearance of the V = O and V-O-V IR bands (which are typical for pure V2O5) and the broadening with a blue shift of the metal-oxygen bond around 622 cm-1. It was suggested that V-O-Sn bonds which are weaker than V-O-V bonds might be formed, and thus the mobility of the lattice oxygen was enhanced. A parallel correlation was found between the concentration of V4+ and the catalytic activity for toluene oxidation at 633K. No detectable change in oxidation state of tin ions was observed in sample either as prepared or under reaction condition by Mossbauer spectroscopy. Most probably, the redox process of V2O5-SnO2 samples during toluene oxidation is realized through the electron transference between V5+ and V4+, and through the consumption and compensation of lattice oxygen.更多还原