具有空间位阻结构的低温SCR脱硝催化剂设计及其抗硫性能研究

Recently, the development of low temperature SCR deNOx catalysts has become the hot point in the field of flue gas NOx emission control. However, the poisoning effect of SO2 for these catalysts inhibits their real application. Based on this point, this proposal put forward a new design of catalyst to exclude SO2 from the SCR reaction system, preserving Lewis acidity sites and active oxygen, by space and acidic limitations with sulfated modifications on the surface of main active phase, thus enhancing the SO2 resistance of the catalysts. Firstly, based on the simulation results of density function theory (DFT), the MnOx nano-catalysts substituted with several metal elements (with strong affinity to sulfate species) were prepared by a continuous hydrothermal (using supercritical water) flow synthesis. And then, sulfate species were grafted onto the surface the resulting catalysts by pre-sulfation treatment. After that, the characterizations of the catalysts physiochemical properties regarding morphology, redox capacity, the distributions of acidic sites as well as their adsorption and catalytic performances for different reactants would be undertaken. The low-temperature SCR reaction performances as well as the SO2 tolerance would be then investigated to clarify the intrinsic structure-performance relationship. All these works would provide useful guidelines for preparing high active low-temperature SCR DeNOx catalysts with strong sulfur tolerance.

低温选择性催化还原（SCR）催化剂的开发是目前烟气脱硝领域的研究热点，但是催化剂SO2中毒的问题已成为其工业应用瓶颈。本申请针对低温SCR脱硝催化剂普遍存在的抗硫性能差的问题，在主要活性物质表面修饰硫酸根基团，通过空间位阻和酸性位组双重保护活性物质上的Lewis酸性位和活性氧免受SO2的侵蚀，达到抗SO2中毒的目的。本申请拟以密度泛函理论（DFT）等计算模拟结果为指导，利用连续超临界水热合成方法将与硫酸根基团有较强亲和力的元素高度分散在MnOx表面，再通过预硫酸化手段在催化剂表面结枝硫酸根基团，制备一系列具有空间位阻结构的Mn基低温SCR催化剂；表征催化剂形貌、氧化还原能力、酸性位分布情况以及对反应物质吸附/氧化能力，考察催化剂反应活性及抗硫性能，分析其内在构效关系，为开发具有良好抗硫性能的低温SCR脱硝催化剂提供实验和理论依据。

中低温选择性催化还原（SCR）脱硝催化剂的反应活性和抗硫性能的提升是烟气脱硝领域的研究热点。本项目通过改进制备方法、掺杂改性以及表面空间位阻基团构建等手段开发出了多种在宽温窗内具有良好脱硝活性和抗硫性能的中低温铈基SCR脱硝催化剂，并且通过BET、XPS、TEM以及TPD等表征手段对其低温活性和抗硫性能提升的原因进行了深入分析。研究结果表明：溶胶凝胶法制备的Ce-O-P催化剂以及Nb改性的Cu-Ce-Ti催化剂具有优异的中低温活性，主要是原因是酸性和氧化还原能力的增强，进而提升了低温下NH3的活化能力并抑制了高温下N2O的产生。进一步地，开发出了具有良好抗硫性能的Ca-Ce-O-P催化剂和Sb-Ce-Zr催化剂（250℃和100ppm SO2条件下，Ca-Ce-O-P催化剂可维持90%以上脱硝活性）。Ca或者Sb的原位掺杂点的活性氧组分提供了部分SO2优先吸附位点，在反应过程中构建了具有空间位阻结构的硫酸根基团保护层，抑制了SO2的对活性点位进一步侵蚀，从而提升了催化剂的抗硫能力。此外，还研究了烟气中其他干扰组分对开发出的铈基中低温催化剂反应性能的影响，并深入揭示了其不同的致催化剂失活的机制。这些工作的开展为铈基中低温催化剂的进一步开发和未来的工业化应用提供了理论指导。