Messi Biology indicated that lithium/magnesium oxide catalysts and lithium/magnesium oxide nanocatalysts were prepared by primary wet impregnation and sol-gel method, respectively. The catalytic performance of the two lithium/magnesium oxide catalysts was compared for the methane oxidation coupling reaction. The characterization was carried out by X-ray diffraction, BET adsorption and transmission electron microscopy. The catalysts were tested at 973-1073 K and a total pressure of 101 kPa. The experimental results showed that the lithium/magnesium oxide nanocatalysts exhibited higher methane conversion, higher selectivity and higher yields of the main products (ethane and ethylene) than the common catalysts for the methane oxidation coupling reaction.
Effect of magnesium oxide on catalyst carrier stability
The XRD of the sample CoO-MoO3/r-alumina before and after the hydrothermal treatment showed that after the treatment at 8.0 MPa, high temperature and higher water vapor partial pressure, the catalyst phase with r-alumina as the catalyst carrier changed considerably, and in addition to the original characteristic peak of alumina, a very obvious low-angle diffraction spectrum peak appeared, i.e., the Al-oxygen In addition to the characteristic peak of alumina, a very obvious low-angle diffraction spectrum peak, i.e., the characteristic peak of AlOOH of Al-oxides, appeared, generating an aluminum-water compound similar to the structure of thin alumina.
From the SEM images of various samples before and after treatment, it can be seen that the catalyst carriers without MgO treatment not only have blurred boundaries after “hydrothermal” treatment, but also clearly show the blockage of precipitates in the voids.
The magnesium oxide treated sample showed no phase change. The internal particles of the catalyst carrier were intact and the boundary was clear, and no blockage of precipitates was observed. It fully indicates that some kind of reaction between magnesium oxide and part of r-alumina catalyst carrier has occurred to produce magnesium-alumina crystals or intermediate forms of structurally stable substances, thus improving the structural stability of the catalyst carrier