水蒸气和α-Fe_2O_3对铈改性半焦脱除单质汞的影响研究

采用浸渍法制备了铈改性半焦吸附剂(Ce/SC),在小型固定床反应器上考察了水蒸气和α-Fe_2O_3对Ce/SC脱除Hg~0性能的影响,并利用X射线衍射、H2程序升温还原、X射线光电子能谱等分析手段对其机理进行了探究。结果表明,水蒸气会明显抑制Ce/SC对单质汞的脱除效率,原因是H_2O分子在活性组分CeO_2表面发生解离,部分晶格氧转化成Ce-OH官能团,从而导致其氧化活性的降低;α-Fe_2O_3的加入对Ce/SC的脱汞性能无显著影响;当水蒸气和α-Fe_2O_3同时存在时,Ce/SC的脱汞效率虽然有所降低,但是其降低幅度明显低于水蒸气单独作用时的情况,这主要是因为水蒸气与α-Fe_2O_3作用增加了其表面化学吸附氧的含量,提高了α-Fe_2O_3的氧化活性,促进单质汞的氧化和脱除。

Effect of water vapor and α-Fe2O3 on elemental mercury removal performance over cerium oxide modified semi coke

Cerium modified semi coke adsorbent (Ce/SC) was prepared by impregnation method and a bench-scale fixed bed reactor was used to study the effect of H₂O vapor and α-Fe₂O₃ on elemental mercury removal efficiency over Ce/SC. Characterizations of X-ray powder diffraction (XRD), Hydrogen temperature programmed reduction (H₂-TPR), and X-ray photoelectron spectroscopy (XPS) were conducted to investigate the mechanism of elemental mercury removal.The adsorption results showed that H₂O had a negative effect on the oxidation activity of the adsorbent. H₂O can be dissociated on the surface of CeO₂ with partial lattice oxygen transformation into Ce-OH functional groups which led to the decrease of its oxidation activity and thus resulted in the inhibitory effect of mercury removal efficiency. The addition of α-Fe₂O₃ had no significant effect on mercury removal over Ce/SC. The mercury removal efficiency of Ce/SC was decreased when the water vapor and α-Fe₂O₃ existed simultaneously. However, the decrease rate was much lower than that of water vapor conditions alone mainly due to the interaction between water vapor and α-Fe₂O₃ increased the content of the surface chemical adsorbed oxygen and thus the oxidation activity and elemental mercury removal performance of Fe₂O₃were promoted.