高分散隔离活性位催化剂上甲烷等低碳烷烃的活化与选择转化

The activation and direct conversion of methane and other low alkanes is one of the most challenging research directions in the catalysis area of today’s world. In this research plan, transition metal-doping mesoporous materials and mesoporous-microporous composite zeolites are to be studied and prepared by direct and in-situ synthesis method. Moreover, the catalysts with stable, highly dispersed and isolated Pt or Pd active sites with atomic level dispersion on the two-dimensional materials of graphene or boron nitride are to be studied and synthesized via the bonding between noble metals and the surface vacancies of graphene or boron nitride. The controlling rules for the preparation of the designed catalysts are to be summarized. The activity for the conversion and reaction depth of low alkanes, selectivity to designed products, and stability of the catalysts can be controlled by tuning the density, the dispersion and chemical environments of active sites. We plan to deeply understand cooperating interaction mechanism of non-thermal plasma and catalysis for the conversion of methane. Especially, the structural changes of active sites during reaction and product distribution are to be investigated by means of combined in-situ Raman-IR-MS, in situ Synchronous Radiation, in situ (optical fiber) Laser Raman Spectroscopy, Laser-Induced Fluorescence Spectroscopy. The reaction mechanism are to be investigated and discussed by correlating the obtained results via the characterization with instrumentation and those obtained by theoretical calculation. And then the structure-performance relationships among the catalysts with highly dispersed and isolated active sites and the catalytic performance for the selective conversion of low alkane are to be established. The accurate design and construction of the confinement of active sites and electronic configurations can be realized. That will provide a scientific foundation for the designing of the efficient catalysts for the conversion of low alkanes.

甲烷等低碳烷烃的活化和直接选择转化是当今世界催化领域最具挑战性的研究方向之一。拟采用原位法研制高活性的过渡金属骨架掺杂的介孔、介微孔复合分子筛催化剂，利用石墨烯、氮化硼等二维材料表面的丰富缺陷位与贵金属原子成键研制高稳定性原子级高分散Pt、Pd隔离活性位催化剂，并总结制备规律。通过调变催化剂的活性位密度、分散度和微观化学环境调控低碳烷烃转化活性和反应深度，提高产物选择性和催化剂稳定性。深入认识低温等离子体-催化协同转化甲烷的作用机制；特别是利用原位Raman-IR-MS、原位同步辐射、原位（光纤）激光拉曼光谱、激光诱导荧光光谱等技术研究催化剂活性位点的结构变化及产物分布规律，并与理论计算相关联，探讨反应机理，进而在分子/原子水平上建立高分散隔离活性位催化剂与低碳烷烃选择转化催化性能之间的构效关系，实现活性位限域原子和电子结构的精准设计与构建，为低碳烷烃催化转化高效催化剂的设计提供科学依据。

天然气、页岩气中富含甲烷等低碳烷烃，将其选择氧化为高值含氧化合物和烯烃，具有重要的理论和现实意义。本项目系统性地设计、制备出多个系列高分散隔离活性位催化剂应用于甲烷直接选择氧化制含氧化合物和烷烃脱氢制烯烃反应。.金属有机框架（MOFs）材料不仅能构筑结构均一的高分散金属离子催化剂，而且是一类优良的仿生酶催化剂材料；发现采用疏水改性MOFs材料作为液相反应中的甲烷选择氧化催化剂，不仅克服了MOFs材料普遍不耐水的缺点，同时生成配位不饱和双核铜活性位点，催化剂的表征及密度泛函理论计算证明该位点在低温条件下高效解离H2O2生成Cu(II)-O活性位，能高效活化甲烷的C−H键，实现了10.67 mmol gcat.−1h−1的C1含氧化合物(CH3OH, CH3OOH)的高产率，对C1含氧化合物的选择性高达99.6%，同时，具有优异的稳定性。.在等离子体外场中低温甲烷选择氧化反应中，发现水蒸气和高分散PtOx/BN超轻催化剂的协同效应打破了CH4转化率和含氧化合物选择性之间的“跷跷板效应”, 总含氧化合物产率达到了106.5mmoloxygcat-1·h-1。系列等离子体外场条件下的原位光谱和反应结果表明：H2O促进在催化剂表面物种的选择氧化反应和含氧产物的脱附。.高比表面介孔SiO2限域的高分散VOx、MoOx物种在中高温下具有高的甲烷选择氧化性能。原位Raman等表征证明骨架掺杂的VOx和MoOx物种具有优异的抗积碳和生成选择性晶格氧物种的性能。.发现部分原位还原的纳米TiO2、Al2O3催化剂具有高的丙烷脱氢活性，揭示了氧空位和催化活性之间的线性关系，隔离的氧空位邻近配位不饱和金属-氧酸碱对是丙烷脱氢的活性位。建立了氧气脉冲实验测定氧化物表面和体相氧空位浓度的新方法。.以DMSN为载体制备了系列不同过渡金属掺杂的Pt/M-DMSN催化剂，过渡金属的种类和性质影响了Pt物种分散度及电子性质。其中，Fe助剂促进Pt物种的二次分散，且生成的PtFe合金促进了丙烯的脱附，显著提高催化剂丙烷脱氢稳定性。.通过石墨烯表面碳缺陷与助剂Sn协同调控，构建了原子级分散的Pt3团簇，低温高效活化丁烷C-H键，相较于单原子Pt1和纳米颗粒PtSn，Pt3团簇具有最高的丁烷转化速率与丁烯选择性。