CH_(4)-CO_(2)重整反应用Ni基合金催化剂研究进展

Research progress on Ni-based alloy catalysts in CH_(4)-CO_(2)reforming reaction

CH_(4)-CO_(2)重整反应可以将CH_(4)和CO_(2)两种温室气体转化为理论上n(H2)/n(CO)=1的合成气,对于高效利用天然气资源和实现双碳目标具有重要意义。该反应常用的Ni基催化剂因其成本低、活性高,具备良好的应用潜力,但较为严重的烧结和积炭问题使其容易失活,稳定性至今无法达到工业化要求。通过在Ni中添加另一种金属形成合金是一种有效地提升Ni基催化剂稳定性的方法。为了加深对Ni基合金催化剂在CH_(4)-CO_(2)反应中作用机制的认识,并对今后研究提供指导,对近年来Ni基合金CH_(4)-CO_(2)催化剂的研究进展进行了综述。适量的贵金属(Ru、Pt和Rh等)或非贵金属(Co、Fe和Cu等)掺杂均可有效提升Ni基催化剂的抗烧结和抗积炭能力。贵金属一方面本身具有优秀的活性和稳定性,另一方面可改变Ni基催化剂的表面微观性质,发挥协同作用;非贵金属则大部分本身不具备显著催化活性,主要通过形成合金改变Ni的表面性质,进而影响还原或反应过程的机理。总结得到提升Ni基合金稳定性的机理包括:通过占据Ni台阶位抑制CH_(4)裂解,改变Ni金属原子电子云密度调控CH_(4)和CO_(2)吸附的活化能从而促进表面积炭的氧化消除,抑制烧结从而提高活性金属分散度,通过改变表面原子结构特征抑制积炭形核等,而对于Ni基合金表面微观结构特征和影响因素的深入理解是未来重要的研究方向。

CH_(4)-CO_(2)reforming reaction can convert two greenhouse gases,CH_(4)and CO_(2),into syngas with a theoretical n(H2)/n(CO)=1,which is of great significance for the efficient utilization of natural gas resources and the realization of the two-carbon goal.Commonly used Ni-based catalysts for this process have good application potential due to their low cost and high activity.However,serious sintering and carbon deposits problems make them easy to be inactivated,and their stability cannot meet the industrial requirements.Adding another metal to Ni is an effective way to enhance the stability of Ni-based catalysts.In order to deepen the understanding of the mechanism of Ni-based alloy catalysts in the CH_(4)-CO_(2)reaction and provide guidance for future research,the research progress of Ni-based alloy CH_(4)-CO_(2)catalysts in recent years was reviewed.It is found that an appropriate amount of noble metals(Ru,Pt,Rh,etc.)or non-noble metals(Co,Fe,Cu,etc.)doping can effectively improve the sintering and carbon deposits resistance of Ni-based catalysts.On the one hand,noble metals themselves have excellent activity and stability,and on the other hand,they can also change the surface microscopic properties of Ni-based catalysts and play a synergistic role.Most of the non-noble metals themselves do not have significant catalytic activity,and mainly change the surface properties of Ni by forming alloys,thereby affecting the mechanism of reduction or reaction process.The mechanisms of improving the stability of Ni-based alloys are summarized as follows:inhibiting CH_(4)cracking by occupying the Ni step,adjusting the activation energy of CH_(4)and CO_(2)adsorption by changing the density of Ni metal atom electron clouds to promote the oxidation elimination of surface carbon,inhibiting sintering to improve the dispersity of active metals and inhibiting the nucleation of carbon deposits by changing the characteristics of surface atomic structure,etc.A deeper understanding of the surface microstructure characteristics and influencing factors of Ni-based alloys is an important research direction in the future.