Young-Sam Oh

Methane reforming over Ni/Ce-ZrO2 catalysts: effect of nickel content

The effect of Ni content on the Ni/Ce-ZrO2 catalyst has been investigated in the methane conversion reactions to syngas, such as oxy-reforming, steam reforming and oxy-steam reforming. Among the catalysts examined, Ni/Ce-ZrO2 catalyst with 15% Ni loading exhibits not only the highest catalytic activity and selectivity but also remarkable stability. The TPR results reveal that strong interaction between support and metal exists and that some part of NiO incorporates into the surface of the Ce-ZrO2 support. Combined with H2 chemisorption results, one may deduce that Ni surface area and the chemical environment of nickel, as well as the properties of the Ce-ZrO2 support, play very important roles in the catalytic activity and stability of Ni/Ce-ZrO2 catalysts. It seems that two kinds of active sites, i.e. one for methane and the other for steam or oxygen, are well-balanced on 15% Ni/Ce-ZrO2 catalyst.

Partial Oxidation of Methane over Nickel Catalysts Supported on Various Aluminas

Partial oxidation of methane (POM) was systematically investigated in a fixed bed reactor over 12 wt% Ni catalysts supported on α-A12O3, γ-A12O3 and θ-A12O3 which were prepared at different conditions. Results indicate that the catalytic activity toward POM strongly depends on the BET surface area of the support. All the Ni/ θ-Al2O3 catalysts showed high activity toward POM due to the less formation of inactive NiAl2O4 species, the existence of NiO, species and stable θ-Al2O3 phase. Although Ni/γ-Al2O3 showed the highest activity toward POM, long-time stability cannot be expected as a result of the deterioration of the support at higher temperature, which is revealed from BET results. From the reaction and characterization results, it is inferred that the optimal conditions for the preparation of θ-Al2O3 are 1,173 K and 12 h.

Thermodynamic design data and performance evaluation of the water + lithium bromide + lithium iodide + lithium nitrate + lithium chloride system for absorption chiller

Abstract Duhring (P–T–X) and enthalpy-concentration (H–X–T) diagrams of the H2O + LiBr + LiNO3 + LiI + LiCl (mole ratio of LiBr : LiNO3 : LiI : LiCl = 5 : 1 : 1 : 2) system were constructed by using the experimental data sets. Thermodynamic design data for a double-effect series-flow absorption chiller were calculated at various operating conditions [ 2≤Te≤14°C, 30≤Ta≤50°C, 30≤Tc≤50°C, T gh COP =0 ≤T gh ≤T gh (crystallization limit)] by a computer simulation. The proposed working fluid was found to be applicable to cycle operation of air-cooled absorption chiller with no crystallization problem at higher absorber temperature.

Solubilities, Vapor Pressures, and Heat Capacities of the Water + Lithium Bromide + Lithium Nitrate + Lithium Iodide + Lithium Chloride System

The optimum mole ratio of lithium salts in the H2O + LiBr + LiNO3 + LiI + LiCl system was experimentally determined to be LiBr : LiNO3 : LiI : LiCl = 5 : 1 : 1 : 2. The solubilities were measured at temperatures from 252.02 to 336.75 K. Regression equations on the solubility data were obtained with a least-squares method. Average absolute deviations of the calculated values from the experimental data were 0.15% at temperatures <285.18 K and 0.05% at temperatures ≥285.18 K. The vapor pressures were measured at concentrations ranging from 50.0 to 70.0 mass% and at temperatures from 330.13 to 434.88 K. The experimental data were correlated with an Antoine-type equation, and the average absolute deviation of the calculated values from the experimental data was 2.25%. The heat capacities were measured at concentrations from 50.0 to 65.0 mass% and temperatures from 298.15 to 328.15 K. The average absolute deviation of the values calculated by the regression equation from the experimental data was 0.24%.