Ni(Co)-Mo双金属氮化物在多级孔硅铝分子筛中的原位封装及深度加氢脱硫性能

Ni(Co)-Mo bimetallic nitrides with small particle sizes have attracted increasing attention for their considerably improved catalytic performance of hydrodesulfurization. However, they tend to suffer from severe aggregation during catalytic reaction or thermal treatment because of their increased surface free energy at smaller sizes, resulting in suboptimal catalytic activity. Here, we develop a facile strategy to in situ confine Ni(Co)-Mo bimetallic nitrides with small sizes and high thermal stability in hierarchical aluminosilicate zeolites to generate high-efficient catalysts for hydrodesulfurization. Under hydrothermal/solvothermal conditions, the additive Ni(Co)/Mo complexes and polyoxometalates interact with the initial zeolitic gel and are encapsulated within the zeolite framework during the crystallization process. After calcination in NH3, the Ni(Co)-Mo bimetallic nitrides with small sizes are finally nano-confined inside the zeolites. The hydrogenated and mass transfer ability of the catalysts can be adjusted by tuning the sizes, morphology, and composition of Ni(Co)-Mo bimetallic nitrides and the acidic properties, mesopore distribution, and crystal sizes of hierarchical aluminosilicate zeolites. To account for the relationship between the structures of the Ni(Co)-Mo bimetallic nitrides with their catalytic performance, density functional theory calculations and X-ray absorption fine structure studies will be performed to study the hydrodesulfurization mechanism on the catalysts. This study will demonstrate a facile and in-situ synthesis strategy, which we believe will promote both fundamental understanding and future improvement of hydrodesulfurization catalysts.

小尺寸的Ni(Co)-Mo双金属氮化物因其独特的电子结构和高效的加氢脱硫催化性能而成为研究的热点。但小尺寸催化材料具有较高的表面能，在催化反应中易团聚失活。本项申请拟开发一种原位合成策略，利用分子筛优异的限域作用，合成多级孔硅铝分子筛封装小尺寸、高稳定性Ni(Co)-Mo双金属氮化物复合深度加氢脱硫催化剂。在水热/溶剂热条件下，通过引入与分子筛合成体系兼容的Ni(Co)/Mo配合物及多金属氧酸盐前驱体，使过渡金属配合物得以原位封装，并通过进一步氮化处理，实现小尺寸双金属氮化物在分子筛中的限域合成。通过调控Ni(Co)-Mo双金属氮化物的组成、尺寸、形貌以及多级孔硅铝分子筛的酸性、孔道尺寸及晶体尺寸，进一步提升复合催化剂的加氢能力和传质速率，以实现高效加氢脱硫催化。此外，结合理论计算与同步辐射表征等方法，深入认识催化剂微观结构与催化性能之间的关系，进一步指导深度加氢脱硫催化剂的合成。

钼基催化剂是一类高效的加氢脱硫催化材料，具有较小尺寸、较少层数的钼基催化剂可以暴露出更多可接触的活性位点，常常展现出更高的催化活性。探索简捷、高效的小尺寸钼基催化剂的限域合成方法，合成具有深度加氢脱硫性能的多级孔分子筛限域小尺寸、高稳定性镍钼双金属化合物催化剂是项目主要的研究内容。项目按照计划执行，构筑了具有优异纳米限域空间的多级孔分子筛材料，并开发了原位合成、表面曲率限域合成、中空结构限域合成等系列限域合成方法，利用分子筛等多孔材料优异的纳米空间限域作用，合成了一系列具有高加氢脱硫活性的复合催化剂材料。以二苯并噻吩作为模型化物对其深度加氢脱硫催化性能评价表明，利用限域合成策略所开发的复合催化剂体现出优秀的深度加氢脱硫催化活性及稳定性。研究发现，调节催化活性相尺寸和控制加氢脱硫催化过程中反应物和产物的传质对提升加氢脱硫反应性能起着至关重要的作用。通过对分子筛材料的晶体尺寸、孔道结构及中空结构的设计，成功调控了钼基双金属化合物催化活性相的尺寸和形貌，并有效提升了复合催化剂的深度加氢脱硫性能。本项目不仅有助于开拓复合催化剂材料合成的新路线，也为提高深度加氢脱硫催化剂催化活性与稳定性提供了新思路。