abstract

The effect of H2 addition on CH4 decomposition over activated carbon (AC) catalyst was investigated. The results show that the addition of H2 to CH4 changes both methane conversion over AC and the properties of carbon deposits produced from methane decomposition. The initial methane conversion declines from 6.6% to 3.3% with the increasing H2 flowrate from 0 to 25 mL/min, while the methane conversion in steady stage increases first and then decreases with the flowrate of H2, and when the H2 flowrate is 10 mL/min, i.e. quarter flowrate of methane, the methane conversion over AC in steady stage is four times more than that without hydrogen addition. It seems that the activity and stability of catalyst are improved by the introduction of H2 to CH4 and the catalyst deactivation is restrained. Filamentous carbon is obtained when H2 is introduced into CH4 reaction gas compared with the agglomerate carbon without H2 addition. The formation of filamentous carbon on the surface of AC and slower decrease rate of surface area and pores volume may cause the stable activity of AC during methane decomposition.

Conclusions

The addition of hydrogen in methane obviously influences the catalytic performances of SM-AC and the carbon structure formed from methane decomposition. The stability of the carbon catalyst was significantly improved although the initial activity of SM-AC decreased when a certain amount of hydrogen was added to methane. The addition of hydrogen improves themethane decomposition over SM-AC but restricts the reaction at excessive amount. What's more, the filamentous carbon deposits are formed on surface of the AC catalyst with the introduction of hydrogen into methane besides the production of irregularly agglomerate carbon deposits. The part of surface area and pores are remained after CMHD, which may be the cause for higher stability of SM-AC in the presence of hydrogen. The combined action of the competitive adsorption of hydrogen and methane, the promotion of AC catalyst, and the inhibition of hydrogen to methane decomposition leads to the generation of filamentous carbon and limits the formation of irregularly agglomerate carbon deposits.