Iron and chromium based oxides for residual methane abatement under realistic conditions A study on sulfur dioxide poisoning and steam induced inhibition

Miguel Garcia Vazquez, Ke Wang, Juan Maria González-Carballo, David Brown, Philip Landon, Robert Tooze, Francisco Rafael Garcia Garcia

Research output: Contribution to specialist publicationArticle


A series of iron and chromium-based oxides were used as catalysts for the total oxidation of residual methane under realistic after-treatment conditions. This study operated with sulfur dioxide, steam and methane concentrations similar to those typically found in natural gas turbines and natural gas-powered vehicle exhausts (around 4.6 ppmV of sulfur dioxide and 10%vol of steam alongside 312 ppmV of methane balanced in air). The catalysts were synthesised using the citrate sol-gel method and characterised by BET, XRD, TPR, in situ UV-vis, in situ DRIFTS, SEM, EDX, TEM and TGA under flowing air. The performance of the catalysts was tested at atmospheric pressure and operating temperatures between 450°C and 550°C using three different reactant mixtures: i) 366 ppmV of methane balanced in air, ii) 347 ppmV of methane and 5.1 ppmV of sulfur dioxide balanced in air, iii) 312 ppmV of methane, 4.6 ppmV of sulfur dioxide and 10%vol steam balanced in air. This study revealed that the iron:chromium ratio has a profound impact on the performance of the catalysts. The XRD characterisation revealed that the iron and chromium-based oxides are solid solutions of hematite and eskolaite. Furthermore, the iron oxide-rich catalysts (60%mol to 80%mol iron content) contain an additional phase, which was identified as a metastable FeCr2O4 mixed oxide with spinel structure. In terms of catalytic activity, resistance to sulfur poisoning and sensitivity towards steam inhibition, these two catalysts were superior to pure iron oxide and comparable to pure chromium oxide. Under dry conditions, these two catalysts achieved higher methane conversion levels than pure chromium oxide, suggesting that the metastable FeCr2O4 spinel gives rise to improved catalytic performance. Finally, this study has proven that the sulfur resistance characteristic of chromium oxide is maintained in iron and chromium-based oxides with a chromium oxide loading as low as 20% mol, resulting in similarly effective catalysts with a lower cost, a reduced environmental impact and a considerable reduction in the health hazards associated with the exposure to chromium.

Original languageEnglish
Specialist publicationApplied Catalysis B: Environmental
Publication statusPublished - 15 Nov 2020


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