Preparation of layered double oxides encapsulated in carbon nanotubes to boost selective synthesis of higher alcohols from syngas: Modifying hydrogenation activity and restricting particle sizes by confinement effect

Abstract

In this work, CuZnAl layered double oxides (LDOs) were encapsulated in carbon nanotubes (CNTs) with different diameters by an ultrasonic-assisted sol-gel method. The CuZnAl LDOs filled in CNTs showed higher catalytic activity and good selectivity for higher alcohols. The catalysts were investigated by varied characterization technologies in order to explore confinement effect of CNTs. It is found that distortion of octahedral unit structure in LDH precursor is enhanced by confinement effect of CNTs. The electron-deficient inner surfaces of CNTs are responsible for the efficient dissociation of CO adsorbed inside CNTs. In addition, hydrogenation ability of the LDOs filled in CNTs is improved due to an obvious decrease in reduction temperature and auto-reduction effect of CNTs, and the restriction effect of CNTs on growth of LDO nanoparticles lead to a rise in their specific surface area. As mentioned above, the changes in structure and properties of LDOs loaded inside CNTs facilitate conversion of syngas into higher alcohols. Moreover, CNTs with small inner size show stronger confinement effect.