H2 production from a plasma-assisted chemical looping system from the partial oxidation of CH4 at mild temperatures

Abstract A plasma-assisted chemical looping system for the production of H 2 (PCLH) was investigated in this study. This system allows the partial oxidation of CH 4 at mild temperatures (573 to 773 K). Four active oxygen carriers: Fe 2 O 3 , NiO-impregnated Fe 2 O 3 (NiO/Fe 2 O 3 ), SrFeO 3-δ and NiO-impregnated SrFeO 3–δ (NiO/SrFeO 3-δ ) were compared, each working both as a packed material for the plasma reactor and an oxygen source for the partial oxidation of CH 4 . Similar conversions of CH 4 , and low yields of H 2 were obtained in Fe 2 O 3 and SrFeO 3-δ . It was concluded that in these cases, H 2 was mainly produced from direct cracking of CH 4 by plasma. In contrast, when using NiO/Fe 2 O 3 and NiO/SrFeO 3-δ , substantial production of H 2 was achieved. It is proposed that there is a synergistic effect between the catalyst and the oxygen carrier; the presence of the metallic Ni phase was responsible for catalysing the production of H 2 , and the oxygen from the support helped prevent the build-up of coke. As a result, the activity of Ni was continuously maintained for H 2 production. The chemical loop is closed with the oxygen carriers being regenerated in air with plasma and then used in the next looping cycle. The high H 2 production capability in NiO/Fe 2 O 3 was repeatable; whilst, NiO/SrFeO 3-δ deactivated in the second and third cycles. Amongst the temperatures studied, NiO/Fe 2 O 3 at 673 K resulted in the best performance for H 2 -rich gas production. A further increase in the operating temperature led to a total combustion of CH 4 .