Recovery of useful chemicals from paper sludge-derived tar by catalytic partial oxidation over zirconia-supporting iron oxide catalysts in steam atmosphere

To develop a method for converting paper sludge-derived tar to useful petroleum-related chemicals, the catalytic cracking of the tar over zirconia-supporting iron oxide catalysts (ZrO₂/FeO_x catalyst) in a steam atmosphere was examined. Useful aromatics such as toluene, ethylbenzene, and styrene are included in the tar at compositions of approximately 63% with the remaining 37% being unknown components. By applying the ZrO₂/FeO_x catalyst, the unknown components were effectively decomposed without decomposing the useful chemicals existing in the tar, and the concentrations of unknown components were decreased from 37 to 11%. Moreover, acetone and phenol were newly produced. The lattice oxygen of the FeO_x was the active site for the catalytic decomposition of the unknown components in the tar, and the ZrO₂ on FeO_x had activity for decomposing H₂O molecules, thereby yielding active oxygen species. The oxygen active species spilled over on the FeO_x surface to regenerate the oxygen defects formed during the reaction. Accordingly, the catalytic activity and stability were due to the consumption and regeneration of the lattice oxygen.