Li/MgO Catalysts Doped with Alio-valent Ions. Part I: Structure, Composition, and Catalytic Properties

Fourier-transform infrared and X-ray diffraction analyses of the hydration reaction of pure magnesium oxide and chemically modified magnesium oxide

The magnesium hydroxide/magnesium oxide (Mg(OH)₂/MgO) system is a promising chemical heat storage system that utilizes unused heat at the temperature range of 200–500 °C. We have previously reported that the addition of lithium chloride (LiCl) and/or lithium hydroxide (LiOH) promotes the dehydration of Mg(OH)₂. The results revealed that LiOH primarily catalyzed the dehydration of the surface of Mg(OH)₂, while LiCl promoted the dehydration of bulk Mg(OH)₂. However, the roles of Li compounds in the hydration of MgO have not been discussed in detail. X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) techniques were used to analyze the effects of adding the Li compounds. The results revealed that the addition of LiOH promoted the diffusion of water into the MgO bulk phase and the addition of LiCl promoted the hydration of the MgO bulk phase. It was also observed that the concentration (number) of OH⁻ affected hydration. The mechanism of hydration of pure and LiCl- (or LiOH)-added MgO has also been discussed.

The effect of LiCl and LiOH on the hydration of MgO was investigated by XRD and FT-IR measurements, which can help to identify dopants that can effectively catalyze the Mg(OH)₂ dehydration and MgO hydration processes.

Nanosheet-Like Ho2O3 and Sr-Ho2O3 Catalysts for Oxidative Coupling of Methane

In this work, Ho2O3 nanosheets were synthesized by a hydrothermal method. A series of Sr-modified Ho2O3 nanosheets (Sr-Ho2O3-NS) with a Sr/Ho molar ratio between 0.02 and 0.06 were prepared via an impregnation method. These catalysts were characterized by several techniques such as XRD, N2 adsorption, SEM, TEM, XPS, O2-TPD (temperature-programmed desorption), and CO2-TPD, and they were studied with respect to their performances in the oxidative coupling of methane (OCM). In contrast to Ho2O3 nanoparticles, Ho2O3 nanosheets display greater CH4 conversion and C2-C3 selectivity, which could be related to the preferentially exposed (222) facet on the surface of the latter catalyst. The incorporation of small amounts of Sr into Ho2O3 nanosheets leads to a higher ratio of (O− + O2−)/O2− as well as an enhanced amount of chemisorbed oxygen species and moderate basic sites, which in turn improves the OCM performance. The optimal catalytic behavior is achievable on the 0.04Sr-Ho2O3-NS catalyst with a Sr/Ho molar ratio of 0.04, which gives a 24.0% conversion of CH4 with 56.7% selectivity to C2-C3 at 650 °C. The C2-C3 yield is well correlated with the amount of moderate basic sites present on the catalysts.

Study of the microstructure and antibacterial properties of MgO with doped defects

In this paper, in order to effectively utilize salt lake magnesium resources, we focused on a functional material containing magnesium, i.e. magnesium oxide, MgO, which is a type of antibacterial material. Through a first-principles study from the atomic level, the microstructure of MgO containing doped point defects of different elements was studied. The relationship between the microscopic structure of the material and its special antibacterial function was explored. The results are as following: the interstitial impurities in MgO are more helpful than substituted impurities for the improvement of the electronic structure. The analysis of the influence of different doping elements on the microstructure confirmed theoretically that Ag and Cu have the same highly active antimicrobial properties with the same change of microstructure, thereby confirming the relationship between microstructure and antimicrobial activity. The results of the simulations match the experimental results, thereby theoretically demonstrating the relationship between defects and antibacterial activities and providing further insight into the nature of the antibacterial mechanism.