锰改性活性焦脱除合成气中单质汞的影响因素

采用等体积浸渍法制备了Mn改性活性焦吸附剂(Mn-AC),研究了模拟合成气(0.04%H2S、20%CO、30%H2、N2为平衡气体)下Mn-AC对单质汞的吸附特性,并利用BET、XPS、XRD等手段对吸附剂进行表征,分析了还原性气体对吸附剂脱汞性能的影响。结果表明,在模拟合成气气氛下,Mn-AC具有优异的汞脱除能力,200℃下2 h内平均汞脱除率达到84.3%。合成气中,H2S提供了具有脱汞能力的活性硫吸附位(Sad),显著地提高了Mn-AC的高温脱汞能力;H2消耗了吸附剂表面的活性氧,不利于活性硫的生成,CO消耗了生成的活性硫吸附位,两者对汞脱除均有抑制作用。高温下由于活性硫和汞的反应减弱,同时H2的抑制作用加强,吸附剂对单质汞的脱除能力下降。

Factors influencing the removal of ele mental mercury by Mn-AC sorbent in syngas

Activated coke modified with manganese acetate (Mn-AC) was prepared through incipient impregnation and characterized by nitrogen sorption, X-ray photoelecuon spectroscopy (XPS) and X-ray diffraction (XRD). Mn-AC was used as a sorbent in the removal of elemental mercury in a simulated syngas (0.04% H₂S, 20% CO, 30% H₂ and balanced N₂) and the various actors influencing the removal efficiency were investigated in a bench-scale fixed-bed reactor. The results indicated that Mn-AC exhibits excellent Hg⁰ removal capacity at 200 ℃ and 84.3% of Hg⁰ can be removed from the syngas. H₂S present in the syngas can obviously promote the Hg⁰ removal efficiency at high temperature, as H₂S is oxidized to elemental sulfur (S_ad) that provides active adsorption sites for Hg⁰ to form HgS. Both H₂ and CO are unfavorable to mercury removal, as H₂ may deplete the active oxygen in the sorbent surface and CO may react with the active sulfur sites (forming COS). At high temperature, mercury removal is suppressed, which may be attributed to that the interaction between Hg⁰ and active sulfur sites is weakened and reducing capacity of H₂ is strengthened, resulting in the decrease of the active sites for mercury adsorption.