非晶复合氧化物中低温脱硝活性位和机理研究

Nitrogen oxides (NOx) contribute much to acid rain,photochemical smog and the depletion of tropospheric ozone.In China, after the SO2 emission has been under control in the National Eleventh Five-Year Plan, the total amount of NOx emission will be limited during the National Twelfth Five-Year Plan. The selective catalytic reduction (SCR) of NOx with NH3 is widely used and commercial technology for the removal of NOx. Therein, the SCR catalyst is the most important. Due to the demand for catalysts which are active at low and medium temperatures in NOx removal in the areas of industrial boilers and kilns, diesel engines and power plants (in the case of the fact that deNOx facilities are placed behind precipitator or deSO2), the amorphous Ce-Ti mixed oxides were found to be active, which suggests that the SCR properties are not associated with the crystallinity but with the short-range order of oxides. In this project, the active catalysts were first characterized by various techniques. Secondly, the acidity and reaction dynamics were investigated. Then, the temperature-programmed surface reactions of NOx and NH3 were conducted using in situ FTIR spectroscopy-on line mass spectrometer. Finally, the active sites, reaction intermediates and mechanism were confirmed in combination with above results. The elucidation of such questions will be crucial to develop new and highly active catalysts especially at low and medium temperatures.

氮氧化物（NOx）是造成酸雨、光化学烟雾和臭氧层破坏的主要污染物。我国在"十一五"脱硫取得阶段性成果之后，"十二五"期间将对NOx排放进行总量控制。氨（NH3）选择性催化还原是目前国际上公认和应用最广泛的商业化方法，而催化剂就是该工艺的核心。本项目针对工业锅炉和炉窑、柴油车和燃煤电厂(脱硝装置放置在除尘器或脱硫之后)等对中低温催化剂的需求，发现了具有较高活性的非晶Ce-Ti复合氧化物催化剂。这充分说明脱硝活性并不与催化剂的结晶有关，而与催化剂的近程有序结构有关。本项目首先通过各种表征确认该体系催化剂的结构，然后对催化剂的表面酸性和反应动力学进行研究，特别是通过NOx和NH3程序升温表面反应的原位光谱和在线质谱技术，发现反应中间物种，并以动力学数据做支撑，确定活性位，探讨可能具有的规律性，从而阐述不同成分和结构催化剂的作用机理，并用于指导研究具有更高中低温活性的新型催化剂。

氮氧化物是造成当前突出环境问题-灰霾的主要污染物，其排放主要来自固定源如燃煤锅炉和移动源如机动车尾气排放。目前控制氮氧化物的工业化技术为氨选择性催化还原(SCR)，由于商业化催化剂V2O5–WO3(MoO3)/TiO2体系含有毒成分V，低温活性也有待提高，因此新型催化剂的研发一直在进行中，而对反应机理的研究反过来又能指导催化剂的研发。该项目发现了氧化物基SCR催化剂具有短程有序结构的活性位，并在Ce-Ti, Moa-Fe2O3和WaFeOx体系中得到证明。意大利米兰理工大学E. Tronconi和I. Nova教授将Ce-O-Ti活性位写入Springer出版的专著“Urea-SCR Technology for deNOx After Treatment of Diesel Exhausts”中。该方面的工作还被美国VerticalNews以“来自济南大学的研究揭示了环境科学与技术的新发现”为题专门报道。该项目还构建了双功能VaMnOx复合氧化物低中温脱硝催化剂，提出了NH2中间物种的转移机制，并经DFT计算证实。在此基础上，发展了Cu-SAPO-44微孔分子筛催化剂。在50000 h-1空速和175-550 oC范围内，Cu-SAPO-44具有90%以上的NOx去除率，接近100%的N2选择性，并具有较好的水热稳定性，这部分工作在ChemCatChem上作为封面文章highlight。通过改进合成方法，首次使用TEPA与TMHD复合模板剂结合的方法合成了SAPO-44以及不同Cu含量的Cu-SAPO-44。为了降低成本，使用价格低廉的CHA代替了价格昂贵的TMHD，并采用TEPA与CHA复合模板剂结合的方法合成了可控Cu含量的Cu-SAPO-44。最后，主持完成了山东省环保产业协会立项的“节能型焦化烟气高效氧化吸收脱硫脱硝一体化技术”中试项目，推动产业化工作。