Synergistic Effect And Mechanism Of Sodium/Iron Bimetallic Catalyst For Gasification Of Coal Char

Demineralized lignite was used to study the synergistic effect and mechanism of the sodium/iron bimetallic catalyst during the gasification.The research mainly consists of three parts.First,gasification results showed that the reaction rate of steam gasification catalyzed by sodium/iron binary metal is higher than single metal catalyst,which indicates the synergistic effect.The influence of different content of sodium and iron was further investigated and the sample of 4.9%Fe-Char+9.4%Na2CO3 had the highest synergy.The influence of gasification temperature was subsequently studied and optimized at 750 ℃.Second,various methods were applied to analyze the changes of sodium/iron-containing char during the pyrolysis,heating and gasification period.The mechanism of synergistic effect was discussed.Iron mitigates the formation of crystalline sodium carbonate and helps sodium to generate more active intermediate during the gasification,thus hindering the evaporation of sodium.In the heating period,iron interacts with sodium,resulting in more active reducing a-Fe.Iron disperses uniformly over the char particle surface at the presence of sodium during the gasification,which also improves its catalysis.The sodium/iron bimetallic catalyst reacts with char more strongly with single catalyst,as it breaks the graphitic structure and helps to form more amorphous carbon components,thus increasing the activity of char.Besides,the bimetallic catalyst has a slight promotion on the mesopores of char.Third,different iron precursors were introduced to the iron-based chars to investigate their influence on the synergistic effect of sodium/iron bimetallic catalyst.The order of gasification rate of samples made by different precursors is FeSO4>FeCO3>Fe(OH)3>FeCl3>Fe(NO3)3.Among them,FeSO4-based char requires the lowest temperature to form sodium-iron-carbon structure and generates the most active intermediate,inhibiting the evaporation of sodium effectively.And much more mesopores is formed on the char,which increases its reactivity.