新型类水滑石层状结构La2O2CO3担载的Ni纳米催化剂的可控制备及其甲烷二氧化碳重整制氢气与合成气的关键问题研究

Methane reforming of carbon dioxide (CRM) can effectively convert abundant natural resources, e.g., greenhouse gases and biomass gas, into syngas, mitigating the warming effect and energy crisis. Traditional Ni-based catalysts tend to deactivate due to coking and sintering during the high temperature reaction. Hexagonal La2O2CO3 is a layered dioxycarbonate with a hydrotalcite-like structure, which is stacked by alternate (La2O2)2+ and CO32- layers along the [001] direction. Its crystallographic plane has a relatively loose atomic configuration and uniform nanospatial distribution of active sites, which is extremely conductive to dispersing active metal phases and activating the acid molecules via exchanging with O2-/CO32- between two (La2O2)2+ layers. However, few applications of La2O2CO3 to CRM have been reported till now. In this study, the nanostructured Ni/La2O2CO3 catalyst is synthesized by straightforward coprecipitation and hydrothermal recipe, and investigated in CRM to explore the structure-property relationship and working mechanism. To tailor morphostructure and quantitatively expose the specific crystal planes can reinforce the working/participating mechanism of La2O2CO3 in the surface elementary reactions, thereby well establishing the dynamic equilibrium between the rates of formation/oxidization of the carbon intermediates and intrinsically inhibiting the coking. Optimizing the nanospatial distribution of metal impregnates over the support surfaces can well modulate the thermal growth mode of metal nanoparticles, strongly immobilizing the nickel nanoparticles on the specific crystal planes of La2O2CO3 with various morphologies, thus greatly strengthening the anti-sintering of nickel. Our study offers the alternative perspective and insight towards preparing the high-efficiency, coke-resistant, and sintering-durable nanocatalyst for the reforming reactions.

CH4和CO2重整（CRM）能有效利用温室气体、生物气等资源生成合成气，缓解温室效应和能源危机。传统镍催化剂易积炭烧结。La2O2CO3是由(La2O2)2+和CO32-层交替堆砌而成的类水滑石层状结构，拥有疏松的表面原子构型，均匀的活性位分布，这不但有利于活性金属相分散还能促进酸性分子与(La2O2)2+层间的O2-、CO32-交换而被活化；然而La2O2CO3在CRM中鲜有研究。本研究拟用简易方法合成Ni/La2O2CO3纳米材料，并探索其在CRM中的构效关系和作用机理。通过形貌可控裁剪、特定晶面定量暴露，强化La2O2CO3在表面基元反应中的作用机制，建立“碳过渡态的生成-消除速率间动态平衡”，解决积碳问题。优化浸渍硝酸盐在载体表面的纳米空间分布，调变金属热生长机制，实现镍在不同形貌La2O2CO3的特定晶面上稳固锚定，抑制镍烧结。本课题研究为开发新型高效催化剂提供了新思路。

针对本课题的主要内容和预期目标，课题组开展催化剂的设计、制备及反应的实验研究。课题严格按照计划执行，在系统整理和分析前人研究成果的基础上，通过各种实验等手段，基本实现了计划任务书中的预期目标。制备了一系列Ni基纳米结构催化剂，探讨了镧系稀土金属La或Ce等影响，考查了其甲烷二氧化碳反应制备氢气和合成气反应性能，取得不错实验结果，并为课题的进一步研究奠定了良好基础。课题内容共发表SCI刊物论文3篇，另外还有一篇SCI论文返修中。共培养硕士研究生4名，参加国际会议两次。