Ga对0.3Ga-WOx/SBA-15催化顺式-环辛烯环氧化的促进作用

Role of Ga in promoting epoxidation of cis-cyclooctene over Ga-WOx/SBA-15

  • 摘要: 本工作研究了镓(Ga)对Ga-WOx/SBA-15催化H2O2与顺式-环辛烯环氧化反应活性的促进作用。最佳催化剂0.3Ga-WOx/SBA-15的TOF为112 h–1,是WOx/SBA-15(57 h–1)的近两倍。相较于WOx/SBA-15(64.0 kJ/mol),0.3Ga-WOx/SBA-15的低表观反应活化能(49.6 kJ/mol)与其优异的环氧化性能一致。动力学分析表明,H2O2在0.3Ga-WOx/SBA-15表面上的吸附更强,这有助于H2O2的活化。基于催化剂的表征和环氧化的性能表明,Ga添加剂的提升作用归因于Lewis酸位点的增加和亲电性的增强。此外,金属过氧化氢(M-OOH)被鉴定为主要中间体。

     

    Abstract: This article investigates the promoting effect of gallium (Ga) on the activity of Ga-WOx/SBA-15 catalyst for cis-cyclooctene epoxidation with H2O2. The optimal catalyst of 0.3Ga-WOx/SBA-15 offered a turnover frequency (TOF) of 112 h–1, which was nearly two times than that of WOx/SBA-15 (57 h–1). The low apparent reaction activation energy for 0.3Ga-WOx/SBA-15 (49.6 kJ/mol vs 64.0 kJ/mol for WOx/SBA-15) was also in line with its superior performance. Kinetic analysis demonstrated stronger adsorption of H2O2 on 0.3Ga-WOx/SBA-15 surface, facilitating the H2O2 activation. Based on the characterizations and catalytic performance, the improvement of Ga was attributed to the increase of Lewis acid sites and the enhancement of electrophilicity. Furthermore, the metal hydrogen peroxide (M-OOH) was identified as the primary intermediate.

     

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