有序介孔碳化硅包覆镍纳米粒子的组装及其催化性能

Coal to Synthetic Natural Gas (SNG) is currently being emphatically developed in China. The main barrier of this technology is the deactivation of conventional Ni-based methanation catalysts, which is caused by the sintering of Ni particles and carbon deposition. To overcome these technical barriers, in this research, we proposed a strategy for assembling ordered mesoporous silicon carbide encapsulated nickel nanoparticles (denoted as Ni@OM-SiC) for methanation. The confinement effect of the mesoporous channels could effectively prevent the migration and aggregation of Ni particles, suppress the coke deposition on the active nickel surface as well, and the high heat conductivity of SiC support are beneficial to decrease the generation of hot spots in the catalyst bed, which endowed the catalyst with prospective catalytic performance. The main components of this research proposal are as follows: The structural properties of the support involving the size, morphology, quantity and distribution of the nickel nanoparticles will be well controlled, the evolutions of the chemical composition, phase structure and texture properties at micro-scale will be explored to make the chemical mechanisms of directed assembly and synthesis clear; the mass transfer process and interaction for reactant molecules will be analyzed systematically, the qualitative relation in multi-scale between catalyst structure and catalytic performance will be established; the inherent characteristic of the catalytic active center will be clarified, while the reasonable reaction kinetic model is to be proposed to ascertain the catalytic mechanism; the sintering behaviour of the confined Ni particles will be understood; and the scientific evidence that the confinement environment provided by the mesoporous channel exerts a spatial restriction on metal particles, hampering their sintering as well as coke formation and finally promote the catalytic activity will be investigated in detail, the bases for controlling the effect of confinement and its role played in designing catalyst are going to be revealed, which will lay scientific foundation to prepare highly efficient catalysts for methanation.

煤制天然气是我国重点发展的现代煤化工技术，烧结和积碳是导致镍基甲烷化催化剂失活的根本原因。本项目组装合成有序介孔碳化硅包覆镍纳米粒子Ni@OM-SiC催化剂，利用介孔孔道的限域效应限制镍颗粒的迁移和聚并、抑制镍表面的积碳现象，借助SiC强导热性减少催化剂床层中热点的产生，进而获得理想的催化效果。主要内容包括：控制载体的结构性质及镍纳米粒子的尺寸、形貌、数量和分布，发现微观层次化学组成、晶相结构、织构特性的演变过程，阐明定向组装合成的化学机制；分析反应物分子在催化剂微观结构的传递过程、相互作用规律，建立多尺度范围内催化剂活性与结构的关系；明确催化活性中心的本征结构，探明催化作用机理，建立详细的反应动力学模型；认识受限体系中金属镍的烧结行为；发现纳米孔道限制金属烧结、改变催化活性、抑制积碳反应的科学证据，揭示“限域效应”的调控基础及其在催化剂设计中的作用，为制备高性能甲烷化催化剂奠定科学基础。