Enhanced catalytic performance of CeO2 confined inside carbon nanotubes for dehydrogenation of ethylbenzene in the presence of CO2

Abstract

Carbon nanotubes (CNTs) filled with CeO2 particles are prepared by wet impregnation assisted by capillary force. Compared to CeO2 outside CNTs, these composites show superior catalytic performance of oxidative dehydrogenation (ODH) of ethylbenzene (EB) to styrene in the presence of CO2. Transmission electron microscopy, temperature-programmed reduction, Raman and X-ray photoelectron spectroscopy are used to investigate the effect of CNT confinement on the catalytic performance of CeO2 inside CNTs. The results indicate that CNT tubular structure results in strengthened interaction between CeO2 and inner wall, which induces distortion and reducibility of CeO2 lattices to promote the activation of surface lattice oxygen and the formation of oxygen vacancy. The activated surface oxygen and oxygen vacancy from CeO2–CNT composites play an important role in two-step ODH reaction by promoting reverse water–gas shift reaction. In addition, CeO2 filled into shorter CNTs exhibits higher catalytic activities due to decreasing the diffusion resistance of reactants and products in CNT channels. The fact that CeO2–CNT composites exhibit excellent thermostability in the atmosphere of CO2 provides a positive choice for enhancing catalytic efficiency at elevated temperature using CNTs as supports.