Hoey Kyung Park

Photocatalytic reduction of carbon dioxide using Co3O4 nanoparticles under visible light irradiation

Photocatalytic reduction of carbon dioxide under visible light irradiation was carried out with Co3O4 powders suspended in water. A Pyrex glass batch reactor of 10mL in volume was used with a 21 W LED lamp of 510 to 620 nm in wave length as light source, and the reaction time was held at 4 h. The major products were formic acid and formaldehyde; the production rates were 4.53 μmol g−1h−1 and 0.62 μmol g−1h−1 for formic acid and formaldehyde, respectively. Carbon monoxide and methane were detected in trace amounts. The occurrence of the photo-reduction with Co3O4 is against the expectation from the valence band edge of Co3O4 in the literature. Possible causes for the contradictory result are discussed.

Prospective application of carbon-silica derived from SiC-Si sludge as a support for Fe catalysts

A unique carbon-silica (30 wt%) material was prepared by H2O activation at 700 °C for 8 h with the carbon derived from SiC-Si sludge and the in-situ hydrolysis of the SiCl4 trapped in the pores of the carbon into silica. The BET surface area of the carbon-silica was 1,750 m2/g and the pore volume by QSDFT was 1.13 cm3/g, 40% of which stemmed from micropores smaller than 2 nm with 60% from mesopores between 2 nm and 50 nm. The activated carbon-silica was loaded with Fe by means of chemical vapor infiltration (CVI) and incipient wetness impregnation (IWI). A hydrogen temperature-programmed reduction test showed that the activated carbon-silica is a prospective support material for Fe catalysts and that the dispersion of Fe in the carbon-silica is higher with CVI than with IWI.

Separation of triethoxysilane from tetraethoxysilane by batch distillation in a packed column

A batch distillation of a crude tetraethoxysilane containing 8mol% triethoxysilane was performed in a glass packed column, 2.54 cm in diameter and 1m in height. Two distillate rates, 3.0mL/min and 6.0mL/min, were used and the reflux ratio was varied up to 3.0. Experimental data were compared with predicted values by Pro/II, a process simulator widely used in the chemical industry. The differential condensation of the vapor in the packed column due to heat losses from the vapor to the column internals and to the surroundings affected the separation efficiency seriously so that a considerable discrepancy was observed between experimental data and prediction by Pro/II in which such heat-loss effects are unaccountable. A model was developed to explain the effect of the differential condensation. For a larger distillation unit scaled up by 100 times where the heat-loss effect is regarded to be minimal, Pro/II simulations were performed to produce 99.9% TEOS with varying reflux ratio, number of stage, and feed composition.

Comparative Study on the Estimation of CO 2 absorption Equilibrium in Methanol using PC-SAFT equation of state and Two-model approach.

The thermodynamic models, PC-SAFT (Perturbed-Chain Statistical Associated Fluid Theory) state equation and the Two-model approach liquid activity coefficient model NRTL (Non Random Two Liquid) + Henry + Peng-Robinson, for modeling the Rectisol process using methanol aqueous solution as the CO2 removal solvent were compared. In addition, to determine the new binary interaction parameters of the PC-SAFT state equations and the Henrys constant of the two-model approach, absorption equilibrium experiments between carbon dioxide and methanol at 273.25K and 262.35K were carried out and regression analysis was performed. The accuracy of the newly determined parameters was verified through the regression results of the experimental data. These model equations and validated parameters were used to model the carbon dioxide removal process.In the case of using the two-model approach, the methanol solvent flow rate required to remove 99.00% of CO2 was estimated to be approximately 43.72% higher, the cooling water consumption in the distillation tower was 39.22% higher,and the steam consumption was 43.09% higher than that using PC-SAFT EOS. In conclusion, the Rectisol process operating under high pressure was designed to be larger than that using the PC-SAFT state equation when modeled using the liquid activity coefficient model equation with Henrys relation. For this reason, if the quantity of low-solubility gas components dissolved in a liquid at a constant temperature is proportional to the partial pressure of the gas phase, the carbon dioxide with high solubility in methanol does not predict the absorption characteristics between methanol and carbon dioxide.