溶液pH值及钨前驱体影响含钨过氧物种结构的Raman光谱研究

识别水溶液体系中含过渡金属W ,Mo的过氧物种结构是探索烯烃、醇及醛等与双氧水催化选择氧化反应机理的关键所在 ,本研究借助高灵敏度的共焦显微Raman光谱表征手段 ,考察了Na2 WO4,(NH4) 10 [H2 W12 O42 ]和H3 PW12 O40 三种含钨前驱体在不同pH值条件下与过量双氧水作用产生的主要过氧物种的结构特征 ,推测在酸性较强 (pH <2 3 )的条件下三者产生的主要过氧物种结构相同 ,可能是单核式的 [WO2 (O2 ) 2 (H2 O) ] 2 -,而二聚态或多聚态的过氧物种几乎不存在于体系中 ;此外 ,还首次建立了通过Raman光谱来半定量测定双氧水浓度的分析方法 ,并尝试用于双氧水催化分解的动力学研究中 .

Raman Study of Transformation Behaviors of Tungsten-containing Peroxo Species Affected by Different Precursors and Solution Acidities

Tungsten and molybdenum compounds act as efficient catalysts for oxidations of olefins, alcohols or aldehydes by hydrogen peroxide. The nature of the peroxo species formed in solutions with different precursors including Na 2WO 4, (NH 4) 10[H 2W 12O 42] and H 3PW 12O 40 in the presence of excess H 2O 2 has been studied by Raman spectroscopy. Regardless of tungsten-containing precursors, mononuclear species of [WO 2(O 2) 2(H 2O)] 2- is likely principal peroxo species under the conditions with low pH (pH<2 3) and excess H 2O 2, and other dimeric or polymeric species are almost absent. Moreover, novel method for determining H 2O 2 concentrations by Raman spectroscopic analysis was established and applied in kinetics study of H 2O 2 catalytic dismutation to H 2O and O 2.