基于C-H键活化构建烃类VOCs净化高效催化剂

In this project, it will focus on the high efficient VOCs catalysts: (1) Based on the understanding of the reaction mechanism, the research work on low temperature catalysts will be focused on the activation of C-H bonds of VOCs. The strong acidic site can promote the heterolytic cleavage of C-H bond and the precious metals can promote molecular oxygen activation, VOCs oxidation reaction should obey L-H mechanism over low temperature catalysts. In the construction of the low temperature catalysts, the active center for the C-H bond activation and the active center for molecular oxygen activation should be as close as possible. (2) In the aspect of catalyst stability, to enhance interaction between the active phase particles and supports to form one migration barrier simultaneously, it is to construct the “energy trap” on the surface to form another migration barrier, the two sorts of barrier can be superimposed to form a larger migration barrier (dual barrier), it can further improve the catalyst stability.（3）In the aspect of anti-poisoning, Cl- and SO2 are selected as the target poisons, the catalysts will be improved by introducing the acid site, it can accelerate Cl- or SO2 the desorption from the active site on catalyst surface. To synthesize the molecular sieve membrane on the surface of the active component, it will also improve the anti-poisoning ability of the catalyst. Considering the influence of water, the surface hydrophobicity of catalysts will be increased as much as possible to improve the stability and the poisoning resistance of the catalysts.

本项研究将围绕烃类VOCs净化高效催化剂开展工作：（1）在低温催化剂方面，基于对反应机理的理解，工作重点是从VOCs分子C-H键活化入手，拟采用高价离子（强“酸性”）促进C-H键发生异裂，同时，还要利用贵金属纳米粒子促进分子氧的活化，使反应按L-H机理进行。在构建低温催化剂时还要将C-H键活化中心与分子氧活化中心在空间上尽可能地接近。（2）在催化剂稳定性方面，一方面通过增强活性组分与载体之间的作用形成纳米粒子迁移势垒，再通过表面形成“能量肼”来构建另一个纳米粒子迁移势垒，两种势垒作用可叠加成一个更大的势垒（双势垒），可大幅度提高催化剂的稳定性。（3）在抗中毒方面，以Cl-和SO2为目标反应物，通过引入酸性位，加速Cl-或SO2从催化剂表面活性位脱附，提高催化剂的抗中毒性能。在活性相表面引入分子筛膜以提高催化剂抗中毒能力。考虑水的影响，尽可能地增强催化剂表面的疏水性，提高催化剂的稳定性。

与芳香烃类和含氧类VOCs相比，目前烃类VOCs，特别是C3H8等低碳烷烃净化所需的催化剂活性还不够高、催化剂的稳定性也不够理想。本项研究是以烃类VOCs净化高效催化剂为目标开展工作的，工作重点是研究这类污染物在催化剂上的活化机理，以及H2O、SO2和多种反应物共存条件下的催化剂失活机制，进而构建高活性VOCs催化剂。本项目实施期间取得了如下主要进展：（1）开发了一种流电沉积制备负载贵金属催化剂制备方法，与其它方法制备的催化剂相比，在相近贵金属负载量、相近贵金属粒径尺寸情况下，流电沉积方法能大幅度提升催化剂的活性，这主要源于其尺寸效应和电子效应。采用流电沉积法制备的GD-Pt/Co3O4其在甲苯催化燃烧反应中的T90仅为150℃；制备的GD-Pd/NiCo2O4显示出非常优异的活化C-H键能力，甲烷完全氧化T90仅为280℃；（2）利用“多重限域”效应，提高贵金属纳米粒子在载体表面迁移的能垒。设计制备的具有四种限域结构的Pt/CeO2/NiAl2O4/Al2O3@SiO2催化剂，经1000℃高温老化5h后其微观结构和催化活性并未发生明显改变，且可节省60%的贵金属；（3）镍的掺杂可提高Pd纳米粒子的稳定性，而采用具有疏水性的小孔分子筛S-1对纳米Pd粒子进行封装，既能提高了Pd纳米粒子的高温稳定性，也大幅度提上了催化剂的抗SO2中毒能力。本项目在执行期间发表论文5篇，申请发明专利2项；培养博士生2人，硕士生1人。