Selective oxidation of p-substituted toluenes to the corresponding benzaldehydes over (VO)2P2O7: an in situ FTIR and EPR study
作者:Ursula Bentrup、Angelika Brückner、Andreas Martin、Bernhard Lücke
DOI:10.1016/s1381-1169(00)00306-x
日期:2000.11
The adsorption and oxidation of p-chlorotoluene (PCT), p-methoxytoluene (PMT), and toluene on vanadyl pyrophosphate catalyst (VPP) were studied by in situ FTIR and EPR spectroscopy. Various amounts of strongly adsorbed benzaldehydes and cyclic anhydride species were observed by FTIR in dependence on the different educts after oxidation experiments. The extent of spin–spin exchange pertubation and,
对氯甲苯(PCT),p的吸附和氧化通过原位FTIR和EPR光谱研究了-甲氧基甲苯(PMT)和钒基焦磷酸催化剂(VPP)上的甲苯。FTIR依赖于氧化实验后的不同离析物,通过FTIR观察到了各种数量的强吸附苯甲醛和环酐物种。自旋-自旋交换穿孔的程度以及因此由底物吸附和相互作用引起的EPR信号强度的损失受芳族化合物的性质影响。发现反应物的强度和产物在催化剂表面上的吸附是醛形成中重要的选择性限制因素。羰基与氧化反应过程中产生的布朗斯台德酸羟基的额外相互作用增强了苯甲醛的吸附,从而促进了更深的氧化。吡啶的共吸附是抑制强醛吸附并提高选择性的一种可能性。恒定转化率下苯甲醛的收率和选择性按PMT <甲苯