摘要
选择性催化还原(SCR)技术以NH_(3)还原氮氧化物(NO_(x))生成N2和H2O,是实现NO_(x)超低排放的主流技术。现有SCR脱硝催化剂一般只适用于200℃以上的烟气脱硝,研发适用200℃以下的低温脱硝催化剂具有显著的节能降碳效益。采用溶胶-凝胶法制备CuO_(x)/SiO_(2)催化剂,通过控制焙烧气氛调节CuO_(x)的化学态,表明随着焙烧气氛中还原性的增强,CuO_(x)/SiO_(2)催化剂中结晶析出的Cu_(2)O物相增多,BET比表面积、孔容、Cu^(2+)/Cu比例逐步下降;在50%(体积分数)的O_(2)气氛中焙烧的CuO_(x)/SiO_(2)-O催化剂表面Cu^(2+)含量高,Cu^(2+)/Cu达到了87.5%(原子分数),在100~125℃的低温区间表现出较高活性;在1.0%(体积分数)的NH_(3)气氛中焙烧的CuO_(x)/SiO_(2)-1.0A催化剂表面则Cu^(+)含量高,Cu^(+)/Cu达到了57.0%(原子分数),在150~200℃的高温区间表现出较高活性,在200℃时NO转化率达到了90.2%;分析表明在低温区间Cu^(2+)发挥着主要作用,Cu^(2+)↔Cu^(+)的循环转变为主要的催化循环过程;在高温区间则可能Cu^(+)发挥着主要作用,而Cu^(2+)可能起次要作用,Cu^(2+)与Cu^(+)组分相互协调,可能同时存在着Cu^(2+)↔Cu^(+)和Cu^(+)↔Cu^(0)的催化循环过程。
Selective catalytic reduction(SCR)technology is the primary approach to achieving ultra-low emissions of nitrogen oxides(NO_(x)),using NH_(3) as a reducing agent to convert NO_(x) into N2 and H2O.However,the existing V2O5-WO_(3)(MoO_(3))/TiO_(2) catalysts generally works at high-temperatures typically ranging from 300 to 420℃,which fails to meet the requirement at low-temperature(100~200℃)for numerous non-coal power industries.The development of novel catalysts meeting the deNO_(x) at low-temperature have significant energy consumption and cost advantages due to being free from the reheating of flue gas.In this study,CuO_(x)/SiO_(2) catalysts were prepared using the sol-gel method,with the calcination atmosphere controlling to 50%O_(2)(volume fraction),standard N2,0.1%NH_(3)(volume fraction),0.4%NH_(3)(volume fraction),and 1.0%NH_(3)(volume fraction),resulting in samples denoted as CuO_(x)/SiO_(2)-O,CuO_(x)/SiO_(2)-N,CuO_(x)/SiO_(2)-0.1A,CuO_(x)/SiO_(2)-0.4A and CuO_(x)/SiO_(2)-1.0A,respectively.The phase composition was analyzed using X-ray diffraction(XRD),the morphology was observed through scanning electron microscopy(SEM),the specific surface area and pore structures were analyzed using a fully automated surface area and porosity analyzer(Micromeritics APSP 2460)via N2 adsorption-desorption tests,the surface elemental chemical states were analyzed using X-ray photoelectron spectroscopy(XPS),and the temperature-programmed desorption(NH_(3)-TPD)and temperature-programmed reduction(H2-TPR)tests were conducted using a fully automated temperature-programmed chemisorption analyzer(Micromeritics Autochem II 2920).XRD results indicated that the catalysts were primarily composed of amorphous structures,with the presence of Cu_(2)O in CuO_(x)/SiO_(2)-1.0A,CuO_(x)/SiO_(2)-0.4A,CuO_(x)/SiO_(2)-0.1A and CuO_(x)/SiO_(2)-N catalysts,evidenced by gradually decreasing diffraction peak intensities of Cu_(2)O.Notably,CuO_(x)/SiO_(2)-O catalyst calcined in 50%O_(2)(volume fraction)atmosphere exhibited no Cu_(2)O diffraction peak.This suggested that with an increased reducing ability in the calcination atmosphere,it was promoted of the formation of Cu_(2)O phase in CuO_(x)/SiO_(2) catalysts.This was further confirmed by H2-TPR tests,where the reducing ability of the calcination atmosphere led to a reduction in H2 consumption,indicating an increased Cu_(2)O phase.These catalysts exhibited a mesoporous structure,including both open and partially blocked mesopores.A comparison of the Brunauer-Emmett-Teller(BET)surface area and Barret-Joyner-Halenda(BJH)pore volume and average pore diameter of CuO_(x)/SiO_(2) catalysts revealed a gradual decrease with increasing reducing ability of the calcination atmosphere.XPS analysis demonstrated that with an enhanced reducing ability in the calcination atmosphere,the surface Cu_(2)O component content increased,the proportion of Cu^(+)increased,and Cu^(2+)/Cu ratio decreased.These findings indicated that the calcination atmosphere significantly influenced the phase,structure and chemical states of CuO_(x)/SiO_(2) catalysts,further impacting their catalytic efficiency.The catalytic performance of CuO_(x)/SiO_(2) catalysts for NO reduction was evaluated within the temperature range of 100~200℃.The results showed that CuO_(x)/SiO_(2)-O catalyst exhibited higher activity in the low-temperature range of 100~125℃,while CuO_(x)/SiO_(2)-1.0A catalyst exhibited higher activity in the high-temperature range of 150~200℃.CuO_(x)/SiO_(2)-O catalyst had a higher surface Cu^(2+)content which played a major role in the low-temperature range,while CuO_(x)/SiO_(2)-1.0A catalyst had a higher surface Cu^(+)content which played a major role in the high-temperature range.The coexistence of Cu^(2+)and Cu^(+)components in the catalysts contributed to their synergistic catalytic activity.In summary,CuO_(x)/SiO_(2) catalysts revealed excellent performance of deNO_(x) at low-temperature.The adjustment of the calcination atmosphere could control the physicochemical properties of the catalysts,thereby influencing their catalytic activity.The findings of this study provided valuable insights for the development of efficient low-temperature deNO_(x) catalysts for the ultraemission of flue gases.
作者
张柏林
杨泽宇
黄鸣天
张生杨
刘波
张深根
Zhang Bolin;Yang Zeyu;Huang Mingtian;Zhang Shengyang;Liu Bo;Zhang Shengen(Institute for Advanced Materials and Technology,University of Science and Technology Beijing,Beijing 100083,China;Shunde Innovation School,University of Science and Technology Beijing,Foshan 528399,China)
出处
《稀有金属》
CSCD
北大核心
2024年第11期1519-1528,共10页
Chinese Journal of Rare Metals
基金
国家自然科学基金青年基金项目(52204414)
国家节能低碳材料生产应用示范平台项目(TC220H06N)
佛山市人民政府科技创新专项资金项目(BK22BE001)
中央高校基本科研业务费专项资金项目(FRF-IDRY-20-005)资助
