Effective NO and SO2 removal from fuel gas with H2O2 catalyzed by Fe3O4/Fe0/Fe3C encapsulated in multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) have been used as catalysts or supports in many industrial applications. Therefore, we provide a low-cost and environmentally friendly route to synthesize MWCNTs from plastics and red mud (RM), which is beneficial to the disposal of waste-solid. This nano-materials (RM-CNTs) are used as novel catalysts for CGPO to remove SO 2 and NO from flue gas. It was unexpected that RM-CNTs exhibit a different catalytic pathway from the RM catalyst (traditional Fenton-like reaction) result from the constrained nano-scale reaction in which Fe 3 O 4 /Fe 0 /Fe 3 C nanoparticles were encapsulated in MWCNTs. Combined with various quenching experiments and characterization analysis, the catalytic mechanism of RM-CNTs was clarified: (1) the in-situ carbothermal reduction increased the activity of the catalysts (Fe 2 O 3 →Fe 3 O 4 →Fe 0 →Fe 3 C); (2) Fe 0 and Fe 3 O 4 can form a metal-semiconductor interface with extremely low resistance which can accelerate electron transfer; (3) Fe 3 C as heterogeneous Fenton catalyst was rarely reported. The experimental results indicated that the activity of Fe-C bond was closely related to the type of carbon substrate during the formation process; (4) MWCNTs encapsulated Fe 3 O 4 /Fe 0 /Fe 3 C particles exhibited excellent catalytic activity, which was due to the existence of 1 O 2 . • A novel catalytic gaseous peroxide oxidation (CGPO) catalyst synthesized by co-pyrolysis method using solid waste red mud (RM) and plastics as a precursor. • It was discovered for the first time that 1 O 2 mediated gas-phase Fenton-like process catalyzed by Fe 3 O 4 @Fe 0 @Fe 3 C nanoparticles encapsulated in multi-walled carbon nanotubes. • Fe 0 and Fe 3 O 4 can form a low resistance metal-semiconductor interface, which can promote the conversion of Fe 3+ to Fe 2+ . • The excellent catalytic activity of RM-CNTs depends on the type of carbon substrate and catalytic reaction inside MWCNTs.