posted on 2021-02-17, 02:03authored byMingyang Li, Cheng Zhang, Liman Fan, Yongfu Lian, Xiaoyu Niu, Yujun Zhu
Coral-like
lanthanum manganese oxides (LayMnOx) with a hierarchical structure
nanosphere were successfully prepared using a simple method, which
presented a high-efficiency catalytic performance for toluene combustion.
Among them, La0.08MnOx with
the Mn3O4 phase exhibits superior catalytic
activity, such as a lower T95 value (218
°C), excellent H2O resistance, and catalytic stability.
The effects of La addition on the bulk and surface physicochemical
properties of LayMnOx were investigated by sorts of characterization including X-ray
diffraction, scanning electron microscopy, transmission electron microscopy,
N2 adsorption–desorption, temperature-programmed
reduction with H2, temperature-programmed desorption of
O2, X-ray photoelectron spectroscopy, and so forth. The
results demonstrate that the doping of La can induce the variation
of physicochemical properties and the formation of more surface oxygen
species and high valence state amorphous manganese oxides, improving
low-temperature reducibility, which facilitates good catalytic activity
for La0.08MnOx. A series of
in situ diffuse reflectance infrared Fourier transform spectroscopy
experiments for toluene adsorption were performed on the La0.08MnOx catalyst pretreated under different
atmosphere conditions to investigate the role of oxygen species and
the reaction processes. The results indicate that the abundant surface
oxygen species over La0.08MnOx can make the rapid formation of benzoic acid species, further transfer
into CO2 and H2O, which is considered as the
key factor in the activation and oxidation of toluene.