Mobility Of O2 Research Articles

Effect of synergistic interaction between Ce and Mn on the CO2 capture of calcium-based sorbent: Textural properties, electron donation, and oxygen vacancy

The diffusion of CO2 and mobility of O2− are the keys to capture of CO2 for CaO-based sorbents. We present a (Ce-Mn)-doped calcium-based sorbent, and investigate the effect of Ce and Mn incorporation on CO2 capture. Interaction between Ce and Mn promotes electron donation from Ca atom to surface oxygen atoms. The stronger the electrons transfer, the stronger interaction between CaO and CO2 is, thus improving CO2 adsorption. Electron transfer between Ce and Mn facilitates oxygen vacancy generation, which improves diffusion and mobility of O2−. In addition, CeO2 and Ca2MnO4 prevent CaO crystallite growth and agglomeration. The (Ce-Mn)-doped sorbents exhibited excellent long-term durability with carbonation capacity of about 0.61 g-CO2/g-ads after 40 cycles.

Effect of micro-structure and oxygen vacancy on the stability of (Zr-Ce)-additive CaO-based sorbent in CO2 adsorption

This study describes the role of micro-structure and oxygen vacancy in CO2 adsorption over (Zr-Ce)-additive CaO. The sorbent was prepared by sol-gel and subjected to characterization in terms of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR). The sorbent (Ca/Zr/Ce=30:0.5:0.5) demonstrated an excellent CO2 capture capacity (0.65gCO2/gsorbent) up to 35 cycles. The enhanced performance is attributed to well-dispersed Ce2Zr2O7 crystallite particle which prevents CaO crystallite growth and agglomeration. The presence of flake microstructure with porosity, nanosized particles, and uniform distribution of Ca and the inert components are essential to the adsorption of CO2. The existence of Ce4+ in the crystal phase of Ce2Zr2O7 may create oxygen vacancy, which favors the diffusion of CO2 and mobility of O2−, further greatly facilitating the capture of CO2. The kinetics of CO2 adsorption was estimated by a double exponential method.

Mechanisms of Molecular Mobility of Oxygen and Nitrogen in Carbon Molecular Sieves

Molecular mobility of oxygen, O2, and nitrogen, N2, in Carbon Molecular Sieves, CMS, was investigated using the Frequency Response, FR, technique to identify mass-transfer mechanisms and related kinetic time constants. The FR data showed that O2 mobility in four types of CMS was dominantly controlled by surmounting surface-barrier resistances, whereas the mobility of both O2 and N2 in pellets of a fifth CMS type obeyed the Fickian diffusion model. Temperature and pressure dependences of surface-barrier penetration time constants were obtained for O2 and N2 in several of those CMS materials. The kinetic time constants of surface-barrier penetration were related to Langmuir-type rate constants, which indicates that kinetic behavior of O2 therein could also be interpreted in terms of a Langmuir-kinetics equation.

Analysis of Trace Amounts of Emitted Gases during Fracture of High-Purity Alumina under Ultrahigh Vacuum. Effects of Sintering Atmosphere and Sintering Time on Gas Emission Behavior.

The effects of sintering atmosphere and sintering time on gas emission behavior during fracture of high-purity Al2O3 were investigated under ultrahigh vacuum using a mass spectrometer to examine the behavior of gases in the material. The gas in the sintering atmosphere was predominantly emitted at the moment of fracture for all specimens. The total amount of gas emitted from a specimen sintered in O2 was less than that of a specimen sintered in air or Ar, showing that the mobility of O2 in the material was much higher than that of N2 or Ar. During prolonged sintering, the density of specimens decreased, while the amount of emitted gas increased. Entrapped gases in the sintered body were concluded to bring about the density decrease during grain growth.

Negative ions in liquid xenon

The structure and mobility of negative ions of oxygen in liquid Xe is investigated. It is shown that the strong exchange interaction of the outer, weakly bound electron of the negative ion with the surrounding liquid leads to a partial compensation of the electrostriction effect, and it prevents the formation of a solid cluster around the negative ion. A simple perturbative model describing the structure of the negative ion in the liquid matrix is developed. The mobility of O2− ions in liquid Xe on the saturation line is estimated. The reasons for the difference in mobility of negative and positive ions are discussed.

USb3O10 as a catalyst for the selective oxidation of propene. Dynamic interaction of the oxide surface with the gas phase

The dependence of catalytic performance on the surface dynamics of USb3O10 has been studied. The sequential treatment of USb3O10 with propene, oxygen and the reactant mixture under the experimental oxidation conditions has been studied using the pulse-microreactor method. The existence of two types of active site on the surface is proposed. Sites with highly coordinated oxygen are responsible for complete oxidation. On the other hand, unsaturated sites lead to a selective process. We also discuss the irreversible surface restructuring in relation to the observed low mobility of O2– ions.