Na2WO4-tuned manganese ore as a high-effective redox catalyst for selective hydrogen combustion in the presence of methane and benzene

Abstract

Selective hydrogen combustion in-situ can break the thermodynamic limit of methane dehydroaromatization, which enhances the yield of aromatic hydrocarbons at a given operating temperature. In this study, sodium tungstate (Na2WO4) was loaded on manganese ore by incipient wetness impregnation, which improved the selectivity of hydrogen combustion dramatically. The selectivity of hydrogen combustion (the percentage of lattice oxygen species involved in hydrogen combustion) is 86% and 53% for Na2WO4-tuned and pristine manganese ore at 750 °C, respectively. Introducing Na2WO4 causes a decrease in both the Mn(IV) fraction and oxygen vacancies in the surface layer as well as changes the crystal structure and the morphology of Mn ore. They are attributed to W ions substituting Mn ions, which makes benzene becomes more difficult to be activated compared with hydrogen at the metal oxide/Na2WO4 interface.