第二金属Fe对Ni-Fe/Al2O3催化CO2甲烷化性能影响

Effect of second metal Fe on the catalytic performance of Ni-Fe/Al2O3 for CO2 methanation

摘要:

采用水热合成法制备了Ni/Al2O3和Ni-Fe/Al2O3催化剂，通过实验与密度泛函理论（DFT）相结合的方式，探究了Fe与Ni的协同作用以及Fe的掺杂对CO2甲烷化的影响。实验结果表明，Ni-Fe催化剂具有更优异的催化性能，在375 ℃下，CO2转化率达到84.24%，CH4选择性达到83.53%。DFT计算表明，第二金属元素Fe的引入稀释了Ni-Fe表面并改变了Ni的电子性质，Ni-Fe表面不仅增强了CO2在催化剂表面的吸附，使CO2的活化程度更高，而且使H2的解离更容易，有利于加氢反应的进行。此外，Fe的引入还改变了CO2的反应途径，使反应向CH4生成方向进行，具体路径为：CO2*→HCOO*→HCOOH*→H2COOH*→H2CO*→H3CO*→CH4*。

Abstract:

CO2 methanation is an important measure to address current environmental issues. Ni-Fe bimetallic catalysts have been widely used in CO2 methanation reactions, but there is limited research on their synergistic effects and reaction mechanisms. In this paper, Ni/Al2O3 and Ni-Fe/Al2O3 catalysts were prepared by hydrothermal method and evaluated experimentally, and the effect of Fe doping on CO2 methanation was investigated through a combination of experiment and theory. The experimental results show that Ni-Fe catalyst has better catalytic performance, with a CO2 conversion rate of 84.24% and a CH4 selectivity of 83.53% at a temperature of 375 ℃. DFT calculations show that the introduction of the second metal element Fe dilutes the surface of Ni-Fe and alters its electronic properties. The Ni-Fe surface not only enhances the adsorption of CO2 on the catalyst surface, resulting in a higher degree of CO2 activation, but also makes the dissociation of H2 easier, which is conducive to the progress of hydrogenation reactions. In addition, the introduction of Fe also changes the reaction pathway of CO2, directing the reaction towards the generation of CH4, The specific pathway is CO2*→HCOO*→HCOOH*→H2COOH*→H2CO*→H3CO*→CH4*.