Sn改性VWTi催化剂高效提高耐碱金属性能—实验与模拟探究

Sn-modified VWTi catalysts for efficiently improving alkali metal resistance-experimental and simulation investigation

  • 摘要: 碱金属会使得脱硝催化剂中毒,降低催化剂的脱硝活性。为了提升VWTi催化剂在碱金属环境中的稳定性和活性,本研究通过掺入Sn元素提升VWTi催化剂抵御碱金属中毒性能。通过等体积浸渍法,合成了不同Sn含量(质量分数为1%、2%、3%)的VWTi催化剂,并评估了其对多种碱金属(KCl、K2O、NaCl、Na2O)的耐受性。利用X射线衍射(XRD)、氮气吸附-脱附(BET)和X射线光电子能谱(XPS)等表征手段对催化剂进行了测试。研究发现,Sn的加入有效增强了催化剂表面的酸性位点,从而提高其抗碱金属中毒能力。通过氨气程序升温脱附(NH3-TPD)分析发现,Sn掺杂增加了催化剂的酸性位点数量和总酸量。氢气程序升温还原(H2-TPR)和XPS结果显示,SnO2的掺入提升了催化剂的氧化还原性能,增加了表面化学吸附氧物种,提升了其对氨的选择性催化效率。将构建的催化剂及碱金属量子化学模型,根据前线轨道理论计算各种碱金属毒物与催化剂的反应活性,以揭示碱金属毒物与催化剂的化学反应机理。结果表明,碱金属与催化剂的反应活性排序为NaCl>KCl>Na2O>K2O,表明,NaCl最容易与催化剂结合发生化学中毒。实验结果表明,各种碱金属物种致使催化剂中毒程度大小为KCl>K2O>NaCl>Na2O,表明,KCl导致催化剂因中毒性能下降最为显著,且在高碱金属浓度条件下,Sn掺杂比例为2%的SnVWTi催化剂展现出优异的催化活性和稳定性,在300 ℃下抵御KCl中毒性能相较于VWTi催化剂提升33.48%。本研究制备的Sn掺杂VWTi催化剂抵御碱金属中毒能力有明显提升,在含有高浓度碱金属烟气处理时具有明显优势。

     

    Abstract: Alkali metals can poison denitrification catalysts and reduce the denitrification activity of the catalysts. In order to improve the stability and activity of VWTi catalysts in high alkali metal environments, this study was carried out to improve the performance of VWTi catalysts against alkali metal poisoning by doping with Sn element. VWTi catalysts with different Sn contents were successfully synthesised by the iso-volume impregnation method and their resistance to different alkali metals (KCl, K2O, NaCl, Na2O) was systematically evaluated. The catalysts were tested using characterisation tools such as X-ray diffraction (XRD), nitrogen adsorption-desorption (BET) and X-ray photoelectron spectroscopy (XPS). It was found that the addition of Sn effectively increased the acidic sites on the surface of the catalyst, significantly improving its resistance to alkali metal poisoning. In addition, Sn doping was found to increase the number of acidic sites and the total acid amount of the catalyst by ammonia programmed temperature rising desorption (NH3-TPD) analysis. Hydrogen programmed temperature rising reduction (H2-TPR) and XPS results showed that SnO2 doping significantly improved the redox properties of the catalysts, increased the surface chemisorption of oxygen species and enhanced their selective catalytic efficiency for ammonia. The constructed quantum chemical models of catalysts and alkali metals were used to calculate the reactivity of various alkali metal poisons with catalysts based on the frontier orbital theory to reveal the chemical reaction mechanism between alkali metal poisons and catalysts, and the results showed that the reactivity of alkali metals with catalysts was in the order of NaCl>KCl>Na2O>K2O, indicating that NaCl was most likely to be chemically poisoned by combining with catalysts. The experimental results show that the degree of catalyst poisoning caused by different alkali metal species is KCl>K2O>NaCl>Na2O, indicating that KCl causes the most significant decrease in catalyst performance due to poisoning.Under the condition of high alkali metal concentration, the SnVWTi catalysts with 2% Sn doping showed excellent catalytic activity and stability. The performance against KCl poisoning at 300 ℃ was improved by 33.48% compared to the VWTi catalyst. This study summarises the mechanism of metal element doping on the performance enhancement of VWTi catalysts, which can help to deeply understand the modification of metal elements on the physicochemical properties of VWTi catalysts, and provide guidance and reference for the development of high-efficiency alkali metal poisoning-resistant VWTi denitrification catalysts, and the Sn-doped VWTi catalysts prepared with alkali metal poisoning have obvious improvement in the ability to resist alkali metal poisoning and have obvious advantages in the treatment of flue gas with high concentration of alkali metal.

     

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