O2、SO2对As2O3在W-Cu/γ-Al2O3催化剂表面吸附特性的影响：实验及理论模拟

Effects of O2 and SO2 on As2O3 adsorption over W-Cu/γ-Al2O3 surface: An experimental combined theoretical analysis

    摘要
  • 摘要: 采用实验及量子化学方法探究了O2和SO2对As2O3在W-Cu/γ-Al2O3催化剂表面吸附特性的影响。实验结果表明，O2促进了As2O3在催化剂表面的吸附，随着SO2体积分数的增加，As2O3的吸附量表现出先升高后降低的趋势。为进一步探究烟气组分对气相砷吸附的影响机理，采用密度泛函理论（DFT）方法，模拟了预吸附不同气体后催化剂表面As2O3的吸附。结果表明，O2对气相砷的促进影响主要归因于吸附氧的形成。预吸附的O原子明显增强了临近原子的吸附活性，而预吸附的O2分子则主要通过提供吸附活性位点促进As2O3的吸附。SO2在W-Cu/γ-Al2O3表面形成了\rmSO^2- _4和\rmHSO^-_4 ，改变了基底表面的势场，从而促进了As2O3的吸附。随体积分数的进一步增加，SO2与气相As2O3的竞争吸附作用增强，As2O3吸附量减少。

     

    Abstract: In this work, the effects of O2 and SO2 on gaseous As2O3 adsorption over W-Cu/γ-Al2O3 catalyst were investigated through adsorption experiment and density functional theory (DFT) method. Experimental results show that the As2O3 adsorption is facilitated by O2, and intensified with the increasing concentrations of SO2. However, it is slightly weakened with the SO2 concentration of 2.0×10−3. The As2O3 adsorption on W-Cu/γ-Al2O3 surface with adsorbed gas constituents was calculated by DFT simulation to reveal the effect mechanism. The promoting effect of O2 on arsenic adsorption is attributed to the formation of adsorbed oxygen. The pre-adsorbed O atom significantly enhances the adsorption activities of adjacent atoms, and the pre-adsorbed O2 molecule provides the active sites for As2O3 adsorption. When SO2 is introduced, the \rmSO^2- _4 and \rmHSO^-_4 are formed, which change the potential field of substrate surface, and further enhance the As2O3 adsorption. However, the competitive adsorption between SO2 with As2O3 is strengthened with increasing SO2 concentration, and it is the reason for the decreasing trend of As2O3 adsorption with high concentrations of SO2.

     

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