碳材料用于低温选择性催化还原脱硝的研究进展

选择性催化还原技术是目前消除NOx的主流技术。碳材料作为自然界广泛存在的一种材料,具有比表面积大、化学稳定性好、结构可调控和表面可改性等优点,广泛应用于低温选择性催化还原反应。综述不同类型碳材料包括活性炭、活性炭纤维、碳纳米管、石墨烯和多孔碳在低温选择性催化还原中的应用,介绍碳材料作为活性组分和催化剂载体的使用情况,讨论表面化学改性对催化NOx性能的影响,阐述碳材料在加快反应速率和提升催化剂抗硫中毒方面的独特性能,并展望碳材料作为新型载体材料在低温选择性催化还原中的应用前景。     

Promotional effect of CO pretreatment on CuO/CeO2 catalyst for catalytic reduction of NO by CO

The CuO/CeO2 catalysts were investigated by means of X-ray diffraction(XRD),laser Raman spectroscopy(LRS),X-ray photoelectronic spectroscopy(XPS),temperature-programmed reduction(TPR),in situ Fourier transform infrared spectroscopy(FTIR) and NO+CO reaction.The results revealed that the low temperature(150 °C) catalytic performances were enhanced for CO pretreated samples.During CO pretreatment,the surface Cu+/Cu0 and oxygen vacancies on ceria surface were present.The low valence copper species activated the adsorbed CO and surface oxygen vacancies facilitated the NO dissociation.These effects in turn led to higher activities of CuO/CeO2 for NO reduction.The current study provided helpful understandings of active sites and reaction mechanism in NO+CO reaction.     

我国氮氧化物排放控制及脱硝催化剂研究进展

氮氧化物(NOx)对大气环境造成的危害已成为影响生态环境和经济社会可持续发展的重要因素,其来源主要集中在火电、玻璃、陶瓷、水泥、钢铁和焦化行业等固定污染源以及机动车、船舶和飞机等移动污染源。实践表明,催化脱硝是NOx减排的最有效手段。介绍我国NOx污染现状,并结合不同领域和行业的烟气特点,阐述NOx的治理情况和研究难点。在此基础上,围绕NOx催化消除这一共性问题,根据不同行业间实际工况的共性和差异性,分别以NH_3-SCR(固定源脱硝)和NO+CO(移动源脱硝)两种催化脱硝技术为主线,系统综述固定源(中高温、低温、抗中毒)及移动源(汽油车和柴油车)中脱硝催化剂的研究进展,并对不同领域相应脱硝催化剂可能的发展方向进行展望。     

超低温（< 150℃）SCR脱硝技术研究进展

以氨为还原剂的选择性催化还原（SCR）技术是工业脱硝的主流技术。我国已形成在180~420℃（包含低温和中高温）范围内具有良好应用效果的SCR技术及其催化剂体系,但超低温段（< 150℃）仍有待突破。超低温SCR脱硝通常位于“除尘-脱硫”工艺之后,具有烟气组成简单、能耗少、改造成本低等优点,吸引了研究人员的广泛关注。在简要分析不同行业烟气排放特征及治理现状的基础上,总结了150℃以下具有良好SCR活性的催化剂体系（锰基、钒基、铬基和活性炭基）,重点对催化剂的抗水、硫、碱金属和硝铵中毒性能进行了探讨,并介绍了该领域最近的一些中试/侧线试验研究进展情况,最后对这一技术的未来发展方向进行了展望。     

CeO2改性对CuO/SBA-15催化剂结构及其催化活性的影响

采用浸渍法在Ce-SBA-15载体上负载活性组分CuO,制备一系列不同配比的CuO/Ce-SBA-15催化剂,运用XRD、TEM、N2吸附、TPR、CO-IR等手段考察催化剂CuO/Ce-SBA-15的物理化学性质,并对其进行CO氧化催化活性的测试。活性测试结果表明,CeO2对SBA-15载体的改性有效地提高了CuO/SBA-15催化剂在CO氧化反应中的催化活性。XRD结果表明:CeO2对SBA-15载体的改性可以促进氧化铜在载体表面的分散;进一步结合H2-TPR、CO-IR表征结果,CeO2促进了CuO在载体表面的还原,这些都有利于催化活性的提高。     

原位拉曼和红外技术对二氧化铈脱硝催化剂硫酸化处理过程的研究

NH_3选择性催化还原NOx技术的关键是催化剂,其中,理解催化剂的硫中毒机制是获取抗硫中毒催化剂的有效方法。借助原位拉曼和红外表征考察氧化态、还原态CeO_2催化剂在二氧化硫、氧气处理气氛中体相和表面硫酸盐以及氧缺陷的变化。NH_3-SCR催化反应结果表明,硫酸化还原态CeO_2具有较优的脱硝性能,这主要来源于还原态CeO_2上的缺陷,有利于氧化SO_2,产生表面硫酸盐,增强催化剂酸性,同时抑制体相硫酸盐的生成,促进NH_3-SCR反应的进行。     

Influence of MnO2 modification methods on the catalytic performance of CuO/CeO2 for NO reduction by CO

In order to investigate the influence of MnO2 modification methods on the catalytic performance of CuO/CeO2 catalyst for NO reduction by CO,two series of catalysts(xCuyMn/Ce and xCu/yMn/Ce) were prepared by co-impregnation and stepwise-impregnation methods,and characterized by means of X-ray diffraction(XRD),Raman spectra,H2-temperature programmed reduction(H2-TPR),in situ diffuse reflectance infrared Fourier transform spectra(in situ DRIFTS) techniques.Furthermore,the catalytic performances of these catalysts were evaluated by NO+CO model reaction.The obtained results indicated that:(1) The catalysts acquired by co-impregnation method exhibited stronger interaction owing to the more sufficient contact among each component of the catalysts compared with the catalysts obtained by stepwise-impregnation method,which was beneficial to the improvement of the reduction behavior;(2) The excellent reduction behavior was conducive to the formation of low valence state copper species(Cu+/Cu0) and more oxygen vacancies(especially the surface synergetic oxygen vacancies(SSOV,Cu+-□-Mn(4–x)+)) during the reaction process,which were beneficial to the adsorption of CO species and the dissociation of NO species,respectively,and further promoted the enhancement of the catalytic performance.Finally,in order to further understand the difference between the catalytic performances of these catalysts prepared by co-impregnation and stepwise-impregnation methods,a possible reaction mechanism(schematic diagram) was tentatively proposed.