(118i) Decomposition of Carbon Dioxide Over Zinc Ferrite Nanoparticles with Methane Recycling

The decomposition of CO₂ over zinc ferrite nanoparticles (ZFNs) at 573 K was studied and the oxidation states of Fe and Zn species were investigated using XANES/EXAFS of fresh and reduced ZFNs with fine structure analyses. Oxygen deficiency in ZFNs was obtained by reducing the ZFNs catalyst in hydrogen. Oxygen deficient ZFNs were found highly active to decompose CO₂ within few minutes. Decomposition of CO₂ was occurred by the incorporation of oxygen in the vacancies of ZFNs and deposition of carbon occurred on the surface. The deposited carbon was converted into methane upon treatment with hydrogen while regenerating used ZFNs to oxygen deficient ZNFs. Oxygen and carbon rather than CO were produced in the decomposition process. Furthermore, the deposited carbon on the surface converts into methane (methanation) upon treatment with H₂ (hydrogenation) while regenerating used ferrite to oxygen deficient ferrite. The complete decomposition of CO₂ was possible because of higher surface-to-volume ratio of ZFNs than bulk zinc ferrite. The pre-edge XANES spectra of Fe in ZFNs exhibits an absorbance feature at 7115 eV for the 1s to 3d transition which is forbidden by the selection rule in case of perfect octahedral symmetry. The EXAFS data showed that the fresh ZFNs had two central Fe atoms coordinated by primarily Fe–O and Fe–Fe with bond distances of 1.89 Å and 3.05 Å, respectively. It also revealed that the ZFNs maintained its spinel structure after reduction at 573 K, even though a minor amount of zinc metal was formed. Recovery of valuable methane by decomposition of CO₂ over ZFNs with recycling heat energy of offgas produced from power generation plant or steel industry is also an appealing resource recovery alternative.