Research progress of nickel-based catalysts for carbon dioxide methanation
ZHANG Xiaoli,GU Fangna,SU Fangbing,XU Guangwen
沈阳化工大学资源化工与材料教育部重点实验室中国科学院过程工程研究所多相复杂系统国家重点实验室沈阳化工大学能源与化工产业技术研究院
CO2甲烷化技术不仅可以实现CO2的循环利用,还能解决CO2排放带来的环境问题。近年来,Ni基催化剂因催化活性好、甲烷选择性高和价格低廉等优点被广泛应用于CO2甲烷化反应中。重点阐述了Ni颗粒的尺寸效应、表面微细结构、载体种类及物理化学性质(碱性位、氧空位、比表面积、孔结构和金属-载体间相互作用)对CO2甲烷化催化剂催化性能的影响,介绍了Ni基双金属合金、结构和电子型助剂对其催化性能的影响,归纳了不同催化剂上CO2甲烷化机理,剖析了Ni基催化剂失活的原因,论述了Ni基催化剂在光热催化CO2甲烷化中的应用,最后对CO2甲烷化催化剂未来研究方向进行了展望。通过对比不同体系获得的研究结果发现,CO2甲烷化反应为结构敏感性反应,Ni颗粒尺寸对催化剂活性有显著影响,然而不同研究得出的最佳Ni颗粒尺寸有明显差异,这可能与不同金属与载体间相互作用或不同制备方法导致的Ni颗粒表面微细结构(如不同晶面、缺陷位等)差异有关,Ni颗粒的尺寸效应有待深入研究;第二金属的加入形成Ni基双金属合金、助剂及研究金属-载体相互作用都有助于开发高稳定性的催化剂;载体表面丰富的碱性位及氧空位,有利于CO2吸附与活化,进而提高催化剂活性。目前,CO2甲烷化反应路径主要分为CO路径和甲酸盐路径,反应遵循的路径可能与反应条件(如温度、压力等)及催化剂表面性质(如羟基丰富度、O2-吸附位点等)有关。然而,关于助剂或载体与Ni物种间的纳米界面结构,以及采用不同助剂和载体对催化剂活性位点及CO2甲烷化反应路径的影响机制,尚缺乏较深入的认知。因此,需借助现场原位成像技术及光谱学技术对催化剂的表界面几何与电子结构进行精细、动态的结构剖析,建立动态结构与性能的构效关系,有利于指导设计合成特定结构的高效Ni基催化剂。
Carbon dioxide methanation is a promising technology for realizing the recycling of CO2 and solving the environmental problems caused by CO2 emissions. Ni-based catalysts have been widely used in CO2 methanation in recent years because of their good catalytic activity,high CH4 selectivity,and low price. The effects of Ni particle size effect,surface microstructure,support type and physicochemical properties (alkaline site,oxygen vacancy,specific surface area,pore structure and metal support interaction) on the catalytic performance of CO2 methanation catalyst were emphatically described. The effects of Ni-based bimetallic alloy,structure and electronic additives on its catalytic performance were introduced,the CO2 methanation mechanism on different catalysts were summarized,the reasons for the deactivation of Ni based catalysts were analyzed,and the application of Ni-based catalysts in photothermal catalytic CO2 methanation was discussed. Finally,the future research direction of CO2 methanation catalyst has been prospected. By comparing the results of different systems,it reveals that the CO2 methanation is a structure-sensitive reaction,in which Ni particle size has significant effect on the activity of the catalysts. However,the optimum Ni particle sizes obtained by different studies are various,which may be related to the difference of the surface microstructure (such as different crystal planes,defect sites,etc.) of Ni particles caused by the different interaction between metals and carriers or preparation methods. Thus,the size effect of Ni particles remains to be further studied. Moreover,the activity and stability of the Ni catalysts can also be improved by adding the second metal or promoters,or tuning the interaction between Ni particles and carriers. The abundant alkaline sites and oxygen vacancies on the surface of the support are conducive to CO2 adsorption and activation,so as to improve the activity of the catalyst. At present,the proposed mechanisms of CO2 methanation over Ni-based catalysts are mainly classified into CO pathway and formate pathway,which pathway followed may relate to the surface properties of the catalysts (such as the concentration of hydroxyl or O2-adsorption site,etc.) and reaction conditions (such as temperature,pressure,etc.). However,there is a lack of in-depth cognition about the nano-interface structure between promoters or carriers and Ni species,and the influence mechanism of different promoters and carriers on the catalytic active sites and the pathway of CO2 methanation. Therefore,it is necessary to make a fine and dynamic structural analysis of the surface interface geometry and electronic structure of the Ni-based catalyst using a series of in-situ imaging and spectroscopy techniques,and establish a dynamic structure activity relationship between structure and performance,which is conducive to the understanding of the above problems,and can also guide the design and synthesis of highly efficient Ni-based catalysts with specific structures.
carbon dioxide methanation;nickel-based catalyst;photothermal catalysis;second metal;support;catalytic activity
0 引言
1 Ni基催化剂
1.1 Ni颗粒的尺寸效应
1.2 Ni颗粒的表面微细结构
1.3 Ni基双金属合金
1.4 助剂对Ni基催化剂性能的影响
1.5 载体对Ni基催化剂性能的影响
1.6 金属与载体间相互作用(MSI)
2 Ni基催化剂CO2甲烷化机理
2.1 CO路线
2.2 甲酸盐路线
3 Ni基催化剂失活研究
3.1 烧结
3.2 中毒失活
4 Ni基催化剂在光热催化CO2甲烷化中的应用
5 结语与展望
主办单位:煤炭科学研究总院有限公司 中国煤炭学会学术期刊工作委员会