制备方法对MnOx-TiO2吸附剂脱汞及抗硫性能的影响

摘要

针对燃煤烟气中单质汞( Hg0)不溶于水很难去除和锰基吸附剂抗硫能力差的问题，以浸渍法、溶胶-凝胶法和沉积-沉淀法等三种方法制备MnOx-TiO2为吸附剂，在固定床实验台架上考察了制备方法对MnOx-TiO2吸附剂Hg0吸附量和抗硫性能的影响；利用N2吸附/脱附、TG-DSC、XRD、TEM、H2-TPR和XPS等手段对吸附剂进行表征。结果表明，制备方法对MnOx-TiO2吸附剂的脱汞活性影响颇大；沉积-沉淀法制备的MnOx-TiO2吸附剂具有较高的Hg0吸附量和抗硫能力。吸附剂的BET比表面积高低与其脱汞活性无直接相关性；与浸渍法和溶胶-凝胶法相比，沉积-沉淀法制备的MnOx-TiO2吸附剂不但可以增强其还原性和MnOx分散度，而且还会显著提高吸附剂表面Mn4+/Mn的比率和表面化学吸附态氧含量，进而增强吸附剂的脱汞活性和抗硫性能。%Aiming at the difficulty of elemental mercury ( Hg0 ) removal from flue gas due to its indissolubility in water and the problem of lower SO2 resistance performance of manganese-based adsorbent, the MnOx-TiO2 adsorbents prepared with impregnation ( IM) , sol-gel ( SG) and deposition-precipitation method ( DP) were employed to remove Hg0 in the absence and presence of SO2 . The adsorbents were characterized by N2 adsorption-desorption, TG-DSC, XRD, TEM, H2-TPR, and XPS techniques. The results showed that Hg0 removal performance over MnOx-TiO2 adsorbents was markedly influenced by the preparation methods. The adsorbent prepared by DP method exhibited a superior activity for Hg0 adsorption and the best SO2 resistance performance. The characterization results indicated that the Hg0 removal activity did not correlate with the BET surface area. The preparation method of deposition-precipitation could not only lead to an increase of reducibility and high dispersion of MnOx , but also significantly enhance a migration of well-dispersed active phase from bulk to surface, resulting in a higher Mn4+/Mn ratio and the presence of abundant chemisorbed oxygen, which would play an important role in promoting Hg0 removal.