摘要
针对模拟钙中毒的商业V_2O_5-WO_3/TiO_2选择性催化还原(SCR)脱硝催化剂,选用络合剂乙二胺四乙酸(EDTA)、表面活性剂十二烷基苯磺酸(LAS)两种清洗剂配合超声波震荡方法对其进行清洗再生,并结合活性测试以及多种表征手段,研究清洗剂浓度及组配方式和清洗时间对钙中毒催化剂的活性恢复及物化性能变化的影响。结果表明:0.01 mol/L的EDTA水溶液辅助超声波震荡清洗30 min取得较好的再生效果,清洗再生后的催化剂脱硝活性在400℃达到85%以上,恢复到新鲜催化剂活性的近90%,并且CaSO_4的去除率达到92%以上,钒和钨的残余率分别为99.4%和98.3%。此外,增加少量的LAS可以微弱地提升CaSO_4的去除率和催化剂的脱硝活性。清洗再生机理研究表明,EDTA可以较好地恢复催化剂的微孔结构、去除表面条带状硫酸钙涂覆层、恢复催化剂表面Lewis酸位以及1 680 cm~(-1)处的Br?nsted酸位。EDTA和LAS均可以有效提高催化剂的氧化还原能力。
For commercial V_2O_5-WO_3/TiO_2 selective catalytic reduction(SCR) denitration catalyst for simulating calcium poisoning,two complexing agents, i.e., ethylenediaminetetraacetic acid(EDTA) and surfactant Dodecylbenzenesulfonic acid(LAS), were selected to clean and regenerate the calcium-poisoned samples with the assistance of ultrasonic oscillation. The effects of concentration of cleaning agent, the combined ratio of cleaning agents and cleaning time on the catalytic performance and physio-chemical properties of the poisoned catalysts were investigated. The results show that aqueous solution of 0.01 mol/L EDTA is assisted by ultrasonic cleaning for 30 min to obtain the effective regeneration. The NOx conversion of Ca-poisoned catalyst can reach r 85% at 400 ℃, the recovery of the fresh counterpart can be 90%, the removal rate of CaSO_4 is over 92% and the residual rates of vanadium and tungsten are 99.4% and 98.3%, respectively. The addition of a small amount of LAS can improve the removal rate of CaSO_4 and the denitration activity of the catalyst. In addition, the cleaning and regeneration mechanism was also analyzed. It is indicated that EDTA can restore the microporous structure of the catalyst, remove the surface banded calcium sulfate coating layer and recover the Lewis acid sites and the Br?nsted acid sites at 1 680 cm~(–1). EDTA and LAS both can effectively improve the redox ability of the catalyst.
引文
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