Revealing the Nature of Active Oxygen Species and Reaction Mechanism of Ethylene Epoxidation by Supported Ag/α-AlO Catalysts.

The oxygen species on Ag catalysts and reaction mechanisms for ethylene epoxidation and ethylene combustion continue to be debated in the literature despite decades of investigation. Fundamental details of ethylene oxidation by supported Ag/α-AlO catalysts were revealed with the application of high-angle annular dark-field-scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy (HAADF-STEM-EDS), techniques (Raman, UV-vis, X-ray diffraction (XRD), HS-LEIS), chemical probes (CH-TPSR and CH + O-TPSR), and steady-state ethylene oxidation and SSITKA (O → O switch) studies. The Ag nanoparticles are found to carry a considerable amount of oxygen after the reaction.

Catalysis. Identification of molybdenum oxide nanostructures on zeolites for natural gas conversion.

Direct methane conversion into aromatic hydrocarbons over catalysts with molybdenum (Mo) nanostructures supported on shape-selective zeolites is a promising technology for natural gas liquefaction. We determined the identity and anchoring sites of the initial Mo structures in such catalysts as isolated oxide species with a single Mo atom on aluminum sites in the zeolite framework and on silicon sites on the zeolite external surface. During the reaction, the initial isolated Mo oxide species agglomerate and convert into carbided Mo nanoparticles.

An information retrieval system for medical records & documents.

The forms of the medical records are different from one institute to another. Moreover, medical records are always stored in free text. Consequently, medical records almost can not be logically analyzed and understood by machines.

Synthesis and characteristics of multi-walled carbon nanotubes-polyimide nanocomposite films.

The polyimide/multi-walled carbon nanotubes (PI/MWNTs) nanocomposite film has been successfully synthesized in this study. The source of MWNTs is prepared by chemical vapor deposition (CVD) method. Then the MWNTs are washed with acid for purification before being added into the polymer matrix.

Calorimetric studies on the thermal hazard of methyl ethyl ketone peroxide with incompatible substances.

In Taiwan, Japan, and China, methyl ethyl ketone peroxide (MEKPO) has caused many severe thermal explosions owing to its thermal instability and reactivity originating from the complexity of its structure. This study focused on the incompatible features of MEKPO as detected by calorimetry. The thermal decomposition and runaway behaviors of MEKPO with about 10wt.

Determination of the chemical nature of active surface sites present on bulk mixed metal oxide catalysts.

CH3OH temperature programmed surface reaction (TPSR) spectroscopy was employed to determine the chemical nature of active surface sites for bulk mixed metal oxide catalysts. The CH3OH-TPSR spectra peak temperature, Tp, for model supported metal oxides and bulk, pure metal oxides was found to be sensitive to the specific surface metal oxide as well as its oxidation state. The catalytic activity of the surface metal oxide sites was found to decrease upon reduction of these sites and the most active surface sites were the fully oxidized surface cations.

In situ UV-vis-NIR diffuse reflectance and Raman spectroscopy and catalytic activity studies of propane oxidative dehydrogenation over supported CrO3/ZrO2 catalysts.

The molecular structures, oxidation states, and reactivity of 3 and 6% CrO3/ZrO2 catalysts prepared by incipient wetness impregnation were examined under different conditions. The in situ Raman spectroscopic studies under dehydrated conditions reveal that the 3 and 6% CrO3/ZrO2 catalysts possess equal amounts of monochromate and polychromate species. Consequently, monolayer coverage on this ZrO2 support is about 3% CrO3.

The reaction pathway for the heterogeneous photocatalysis of trichloroethylene in gas phase.

Trichloroethylene (TCE) has been widely used in industry. It is considered a hazardous and carcinogenic air pollutant. In this investigation, TCE photocatalytic reactions were performed in a packed bed reactor configured as a continuous flow reactor and a FT-IR sample cell used as a batch reactor to determine the intermediates under irradiation by 365 nm UV light.

Pore structure of hydrating cement paste by magnetic resonance relaxation analysis and freezing.

Nuclear magnetic resonance relaxation analysis has been applied to interpret the evolution of microstructure in a cement paste during hydration. A basic understanding of the wet-dry and freeze-thaw processes of cement pastes has been developed. The pore structure evolution has been studied by the suppression of the freezing temperature of water and compared with spin-spin relaxation analysis performed at room temperature.

Surface magnetic relaxation in cement pastes.

Surface magnetic relaxation in porous media is usually attributed to hindered rotation or to paramagnetic impurities on the surface. In cement pastes, however, it seems reasonable to attribute surface relaxation to dipole interactions in water adsorbed as water of hydration on grain surfaces. The rate limiting factor would then be the exchange rate between mobile water in the pores and adsorbed water.

Application of spin-spin relaxation to measurement of surface area and pore size distributions in a hydrating cement paste.

Nuclear magnetic resonance (NMR) relaxation analysis has been applied to interpret the evolution of microstructure in a cement paste during hydration. Measurements of transverse magnetic relaxation were made in fully and partially filled white cement pastes for hydration times between 1 h and 6 mo. It was found that only the evaporable water molecules contributed to the echo amplitude in the NMR measurement, while both the evaporable and the hydrated water contribute to the amplitude of the free induction decay.