为研究具有良好活性的低温选择性催化还原催化剂,针对目前Mn基材料低温选择性催化还原脱硝催化剂研究的局限性,以超氧自由基促进光催化为理论基础,N掺杂改性非金属为研究思路,采用溶胶凝胶法及过量浸渍法制备了N掺杂MnOx/TiO2催化剂,用...为研究具有良好活性的低温选择性催化还原催化剂,针对目前Mn基材料低温选择性催化还原脱硝催化剂研究的局限性,以超氧自由基促进光催化为理论基础,N掺杂改性非金属为研究思路,采用溶胶凝胶法及过量浸渍法制备了N掺杂MnOx/TiO2催化剂,用于锅炉烟气脱硝。提出了氧浓度、[NH3]/[NO]以及空速对脱硝效率的影响,结合X射线衍射表征,获得了N掺杂催化剂的反应工艺参数和相应的晶型变化特性。研究结果表明,N掺杂后,催化剂脱硝活性明显,并对催化剂N掺杂量、Mn负载量及催化剂煅烧温度进行了优化,并对优化结果进行分析。在此基础上,考察了含氧量,得出在O2浓度5%、[NH3]/[NO]为1.2时,空速28 000 h 1,反应温度180℃的条件下,掺N量为1%以及Mn负载量为5%的N掺杂MnOx/TiO2催化剂的脱硝活性稳定在90%左右。展开更多
MnOx-TiO2, CeO2-MnOx-TiO2 and V2O5-MnOx-TiO2 catalysts for low-temperature NH3-SCR were prepared by sol-gel method. The results showed that both cerium and vanadium prevented the transformation ofanatase TiO2 to the m...MnOx-TiO2, CeO2-MnOx-TiO2 and V2O5-MnOx-TiO2 catalysts for low-temperature NH3-SCR were prepared by sol-gel method. The results showed that both cerium and vanadium prevented the transformation ofanatase TiO2 to the mille phase. The addition of vanadium oxide induced the segregation of crystalline Mn2O3, which contributed little to low-temperature SCR and ammonia oxidation, from the MnOx-TiO2 solid solutions. However, the selectivity of the V-containing catalyst was almost 100% due to the decreased ammonia consumption and enhanced adsorption capacity of ammonia on Bronsted acid sites at relatively high temperatures. The electron-donating effect of cerium reduced the Mn^4＋/Mn^3- ratio to some extent, resulting in a decreased activity for ammonia oxidation. This, in combination with the enhanced ammonia adsorption capacity by Ce^n＋ as additional Lewis acid sites, endowed the Ce-doped catalyst a higher N2 selectivity than MnOx-TiO2 despite the slightly elevated light-offtemperamre for NO conversion.展开更多
文摘为研究具有良好活性的低温选择性催化还原催化剂,针对目前Mn基材料低温选择性催化还原脱硝催化剂研究的局限性,以超氧自由基促进光催化为理论基础,N掺杂改性非金属为研究思路,采用溶胶凝胶法及过量浸渍法制备了N掺杂MnOx/TiO2催化剂,用于锅炉烟气脱硝。提出了氧浓度、[NH3]/[NO]以及空速对脱硝效率的影响,结合X射线衍射表征,获得了N掺杂催化剂的反应工艺参数和相应的晶型变化特性。研究结果表明,N掺杂后,催化剂脱硝活性明显,并对催化剂N掺杂量、Mn负载量及催化剂煅烧温度进行了优化,并对优化结果进行分析。在此基础上,考察了含氧量,得出在O2浓度5%、[NH3]/[NO]为1.2时,空速28 000 h 1,反应温度180℃的条件下,掺N量为1%以及Mn负载量为5%的N掺杂MnOx/TiO2催化剂的脱硝活性稳定在90%左右。
基金supported by the National Natural Science Foundation of China(51306046,51166004,51376073)the Fundamental Research Funds for the Universities of Henan Province(NSFRF140204)~~
文摘研究了Mn-W/TiO2用于NH3选择性催化还原NOx体系的催化反应性能,探索了不同温度条件下该催化剂对抗不同SO2浓度的抗毒性能。结果显示WO3能够增加活性酸中心的数量和酸性,是MnOx/TiO2非常有效的助催化剂。在气体体积空速(gaseous hourly space velocity,GHSV)为18900h-1时100～350℃范围内,Mn-W/TiO2催化剂还原NOx的转化率高达80.3%～99.6%,N2选择性达100%～98.7%。当反应气中有0.01%SO2和6%H2O时,120℃NOx转化率可维持在98.5%,当SO2浓度超过0.01%时,则需将反应温度升高到250℃以上才可消除其干扰,而当SO2浓度高达0.07%时,300℃下转化率可长期维持在99%,达到了商用V-W/TiO2催化剂的水平。对于NH3选择性还原NOx体系Mn-W/TiO2显示了极好的催化性能,是目前抗SO2毒性最强的催化剂之一。试验发现,低温条件下,SO2对Mn-W/TiO2催化剂的影响是可逆的,随着反应温度的提高,活性将自然恢复。
基金Project supported by 863 Project (2009AA06Z313,2010CB732304)
文摘MnOx-TiO2, CeO2-MnOx-TiO2 and V2O5-MnOx-TiO2 catalysts for low-temperature NH3-SCR were prepared by sol-gel method. The results showed that both cerium and vanadium prevented the transformation ofanatase TiO2 to the mille phase. The addition of vanadium oxide induced the segregation of crystalline Mn2O3, which contributed little to low-temperature SCR and ammonia oxidation, from the MnOx-TiO2 solid solutions. However, the selectivity of the V-containing catalyst was almost 100% due to the decreased ammonia consumption and enhanced adsorption capacity of ammonia on Bronsted acid sites at relatively high temperatures. The electron-donating effect of cerium reduced the Mn^4＋/Mn^3- ratio to some extent, resulting in a decreased activity for ammonia oxidation. This, in combination with the enhanced ammonia adsorption capacity by Ce^n＋ as additional Lewis acid sites, endowed the Ce-doped catalyst a higher N2 selectivity than MnOx-TiO2 despite the slightly elevated light-offtemperamre for NO conversion.
