Binary Ce–Mn oxides confined in carbon nanotubes as efficient catalysts for ethylbenzene dehydrogenation in the presence of carbon dioxide

Abstract

The present work was undertaken to investigate the influence of binary Ce–Mn species confined in carbon nanotube (CNT) channels on the catalytic properties for oxidative dehydrogenation of ethylbenzene (EB) to styrene utilizing CO₂ as a mild oxidant. 7.0 wt% of Ce–Mn oxides were filled in CNTs by an incipient wetness impregnation method. The texture and physicochemical properties of the as-prepared materials were characterized by TEM, XRD, H₂-TPR, Raman and XPS. The binary Ce–Mn oxides confined in CNTs exhibited much higher catalytic activities than those of single Ce or Mn. Among the catalysts tested, the sample CeMn-in-CNTs with Mn/(Ce + Mn) = 0.375 exhibited the highest conversion of EB and selectivity for styrene. The superior catalytic performance could be attributed to the fact that the doped Mn species could accelerate the oxidation of Ce³⁺ towards Ce⁴⁺ by the reduction of the high valence of Mn species, the occurrence of surface oxygen vacancy and activated oxygen resulting from migration of Mn, and the change of equilibrium caused by coupling a reverse water gas shift reaction.