封装型Pd基催化剂(M@PdX)@HC及其强化H2O2直接合成机制

氢氧直接合成H2O2过程绿色环保、工艺简单，但O2和H2O2分子中O-O键在Pd晶面上容易解离，降低H2O2选择性和产率，限制其工业化应用。本项目提出研究《封装型Pd基催化剂(M@PdX)@HC及其强化H2O2直接合成机制》，主要研究内容（1）研制高H2O2选择性和产率的封装型Pd基催化剂(M@PdX)@HC；（2）研究H2/O2在新型封装型Pd基催化剂的吸附相平衡和动力学、H2/O2/H2O2在孔道的扩散传质；（3）研究新型封装型Pd基催化剂直接合成H2O2的选择性、产率、稳定性与构效关系。研制催化剂核为电负性较强小分子（X）改性的M@PdX纳米球（M为非贵金属），具有大的活性表面、少的不饱和位点和d带电子密度，削弱O-O键的解离能力，使之能于常压下高效合成H2O2，是项目的特色和重要创新之处。项目的研究成果将为常压下氢氧直接合成过氧化氢的选择性和收率较低的难题提供新理论和技术基础。

Despite of the simpleness and environmental friendliness of the direct synthesis of H2O2 from oxygen and hydrogen, the industrialization of such process is still unable to advance. One of the reasons is the easy-occurring O-O bond cleavage in O2 and H2O2 molecules on the surface of Pd-based catalyst, resulting in the lower H2O2 selectivity and yield. To overcome this obstacle, we synthesized encapsulated Pd-based catalyst (M@PdX)@HC and studied its mechanism on enhancing the H2O2 direct synthesis. The mainresearch contents are: (1) the synthesis of (M@PdX)@HC with high H2O2 selectivity and yield; (2) the phase equilibrium and kinatics of H2O2 adsorption on the (M@PdX)@HC, and the mass-transfer of H2/O2/H2O2 in the porous structure. (3) the selectivity, yield, stability and structure-activity relationship of (M@PdX)@HC in the direct synthesis of H2O2. The core of the catalyst (M@PdX)@HC is a M@PdX nanosphere, where X is electronegative small molecule and M is non-precious metal. This nanosphere core has larger Pd exposure surface area, less unsaturated sites and lower electron density on d-orbital, which could reduce the O-O bond cleavage in O2 and H2O2. It is the characteristic and important innovation of the project. This result is the key achievement of this study and it provides a new theory and technology foundation for direct synthesis process of H2O2.