摘要
Cu-ZSM-5直接催化分解烟气中的NO具有潜在的应用前景。然而,高温的烟气中存在不同种类的碱金属,碱金属对Cu-ZSM-5催化分解NO的影响机制尚不清楚。采用液相浸渍法将碱金属Na,K负载到离子交换法制备的Cu-ZSM-5催化剂。探究了碱金属负载量对新鲜的CuZSM-5催化剂直接催化分解NO转化率的影响,并采用XRD,BET,SEM,TEM,XPS,H_(2)-TPR和O_(2)-TPD等表征技术手段对其催化剂骨架结构、孔隙规律、铜物种种类、化学吸附氧和活性物种中氧气的脱附进行分析。研究结果表明,在最佳反应温度550℃下,Cu-ZSM-5催化剂催化分解NO转化率为53%。随着碱金属Na,K负载量的提高,Cu-ZSM-5催化剂直接催化分解NO转换率有明显的抑制作用,且碱金属K造成催化剂NO转化率降低的幅度明显高于碱金属Na。碱金属K可以破坏的ZSM-5分子筛内部独特的三维交叉孔道结构,致使催化剂骨架结构坍塌,堵塞孔道,进一步阻碍了反应物NO与活性位点{Cu-O-Cu}^(2+)的接触,从而导致NO转化率降低。活性成分{Cu-O-Cu}^(2+)部位可以与碱金属Na,K相结合致使催化剂失活,使其转变为新的铜物种CuO微粒,且随着碱金属Na,K含量的增加,CuO数量也逐渐增多,CuO微粒可以占据催化剂孔道和覆盖在催化剂外表面,致使催化剂微孔比表面积和微孔孔容降低。碱金属Na,K抑制了催化剂活性成分{Cu-O-Cu}^(2+)与{Cu-O-Cu}^(2+)之间的氧化还原循环,进而阻碍了NO催化分解成N_(2)和O_(2)。
The direct catalytic decomposition of NO in flue gases by Cu-ZSM-5 has potential application.However,there are different kinds of alkali metals in high-temperature flue gas,and the mechanism of the effect of alkali metals on the catalytic decomposition of NO by the Cu-ZSM-5 is still unclear.In this paper,the alkali metals Na and K were loaded onto the Cu-ZSM-5 catalyst prepared by the ion exchange method using liquid phase impregnation.The effect of alkali metal loading on the direct catalytic decomposition of NO conversion of the fresh CuZSM-5 catalyst was investigated and its catalyst skeleton structure,pore pattern,copper species,chemisorbed oxygen and oxygen desorption from the active species were analyzed by means of characterization techniques such as the XRD,BET,SEM,TEM,XPS,H_(2)-TPR and O_(2)-TPD.The research results show that the conversion of NO for catalytic decomposition over the Cu-ZSM-5 catalyst is 53%at an optimum reaction temperature of 550℃.With the increase of alkali metal Na and K loading,the direct catalytic decomposition NO conversion rate of the Cu-ZSM-5 catalyst is significantly inhibited,and the alkali metal K causes a significantly higher reduction in the NO conversion rate of the catalyst than the alkali metal Na.The unique three-dimensional cross-pore structure within the ZSM-5 molecular sieve,which can be disrupted by alkali metal K,causes the catalyst skeleton structure to collapse,blocking the pore channels and further preventing the contact of the reactant NO with the active site{Cu-O-Cu}^(2+),leading to a reduction in the NO conversion.The active component{Cu-O-Cu}^(2+)site can combine with the alkali metals Na and K to deactivate the catalyst,transforming it into the new copper species CuO particles.And as the content of the alkali metals Na and K increases,the amount of CuO also gradually increases,and the CuO particles can occupy the catalyst pore channels and cover the outer surface of the catalyst,resulting in a reduction in the specific surface area and pore volume of the c
作者
孙瑞彬
王晓霏
张代鑫
刘丁赫
乔晓磊
金燕
樊保国
SUN Ruibin;WANG Xiaofei;ZHANG Daixin;LIU Dinghe;QIAO Xiaolei;JIN Yan;FAN Baoguo(College of Electrical and Power Engineering,Taiyuan University of Technology,Taiyuan030024,China)
出处
《煤炭学报》
EI
CAS
CSCD
北大核心
2022年第9期3493-3504,共12页
Journal of China Coal Society
基金
国家自然科学基金资助项目(U1810126,U1910214)。
