4 research outputs found
Metal-Ion Distribution and Oxygen Vacancies That Determine the Activity of Magnetically Recoverable Catalysts in Methanol Synthesis
Here,
we report on the development of novel Zn-, Zn–Cr-, and Zn–Cu-containing
catalysts using magnetic silica (Fe<sub>3</sub>O<sub>4</sub>–SiO<sub>2</sub>) as the support. Transmission electron microscopy, powder
X-ray diffraction, and X-ray photoelectron spectroscopy (XPS) showed
that the iron oxide nanoparticles are located in mesoporous silica
pores and the magnetite (spinel) structure remains virtually unchanged
despite the incorporation of Zn and Cr. According to XPS data, the
Zn and Cr species are intermixed within the magnetite structure. In
the case of the Zn–Cu-containing catalysts, a separate Cu<sub>2</sub>O phase was also observed along with the spinel structure.
The catalytic activity of these catalysts was tested in methanol synthesis
from syngas (CO + H<sub>2</sub>). The catalytic experiments showed
an improved catalytic performance of Zn- and Zn–Cr-containing
magnetic silicas compared to that of the ZnO–SiO<sub>2</sub> catalyst. The best catalytic activity was obtained for the Zn–Cr-containing
magnetic catalyst prepared with 1 wt % Zn and Cr each. X-ray absorption
spectroscopy demonstrated the presence of oxygen vacancies near Fe
and Zn in Zn-containing, and even more in Zn–Cr-containing,
magnetic silica (including oxygen vacancies near Cr ions), revealing
a correlation between the catalytic properties and oxygen vacancies.
The easy magnetic recovery, robust synthetic procedure, and high catalytic
activity make these catalysts promising for practical applications