Cu基催化剂脱除逃逸氨的机理研究

Mechanisms of slip ammonia removal based on Cu-based catalyst

氨气是PM_(2.5)的重要前体物之一,为了脱除以氨作为还原剂的选择性催化还原(NH_(3) selective catalytic reduction,NH_(3)-SCR)技术产生的脱硝烟气中的逃逸氨,基于固定床反应器对30-CuO/Al_(2)O_(3)的脱除逃逸氨反应机理进行了实验研究。结果发现,由于30-CuO/Al_(2)O_(3)具有载氧体的属性,当反应气体中不含O_(2)时仍发生了基于氧化态载氧体(CuO)的氨脱除过程,由此证明了基于30-CuO/Al_(2)O_(3)的氨脱除过程包含化学链燃烧反应机理,且基于化学链燃烧反应机理的氨脱除的N_(2)选择性明显高于基于选择性催化氧化机理(SCO)的氨脱除的N_(2)选择性。研究SO_(2)对逃逸氨脱除机理的影响发现,当反应气体中含有50μL/L SO_(2)时,与不含SO_(2)相比,350℃下的NO选择性从38.0%大幅降至2.7%,结合催化剂的XRD表征结果认为,含有SO_(2)时的逃逸氨脱除机理以化学链燃烧反应机理为主。

Ammonia is one of the important precursors of PM_(2.5).In order to remove slip ammonia from denitrification flue gas produced by NH_(3) selective catalytic reduction(NH_(3)-SCR)technology with ammonia as reducing agent,the mechanisms of the slip ammonia removal reaction of 30-CuO/Al_(2)O_(3) were studied based on a fixed bed reactor.The results show that due to the oxygen carrier property of 30-CuO/Al_(2)O_(3),the slip ammonia removal process based on the oxidized oxygen carrier(CuO)still occurs when the reaction gas does not contain oxygen.Thus,it is proved that the slip ammonia removal reaction process based on 30-CuO/Al_(2)O_(3) includes chemical-looping combustion mechanism,and the selectivity of N_(2) of slip ammonia removal based on the chemicallooping combustion reaction mechanism is significantly higher than that of the selective catalytic oxidation(SCO)mechanism.The influence of SO_(2) on the slip ammonia removal mechanism was studied.It is found that when the reaction gas contains 50μL/L SO_(2),the selectivity of NO at 350°C is significantly reduced from 38.0%to 2.7%compared with the absence of SO_(2).Combined with the XRD characterization results of the catalyst,it is considered that the mechanism of slip ammonia removal in the presence of SO_(2) is dominated by the chemical-looping combustion mechanism.