Gi Bo Han

Dynamic Hydrogen Production from Methanol/Water Photo-Splitting Using Core@Shell-Structured CuS@TiO2 Catalyst Wrapped by High Concentrated TiO2 Particles

This study focused on the dynamic hydrogen production ability of a core@shell-structured CuS@TiO2 photocatalyst coated with a high concentration of TiO2 particles. The rectangular-shaped CuS particles, 100 nm in length and 60 nm in width, were surrounded by a high concentration of anatase TiO2 particles (>4~5 mol). The synthesized core@shell-structured CuS@TiO2 particles absorbed a long wavelength (a short band gap) above 700 nm compared to that pure TiO2, which at approximately 300 nm, leading to easier electronic transitions, even at low energy. Hydrogen evolution from methanol/water photo-splitting over the core@shell-structured CuS@TiO2 photocatalyst increased approximately 10-fold compared to that over pure CuS. In particular, 1.9 mmol of hydrogen gas was produced after 10 hours when 0.5 g of 1CuS@4TiO2 was used at pH = 7. This level of production was increased to more than 4-fold at higher pH. Cyclic voltammetry and UV-visible absorption spectroscopy confirmed that the CuS in CuS@TiO2 strongly withdraws the excited electrons from the valence band in TiO2 because of the higher reduction potential than TiO2, resulting in a slower recombination rate between the electrons and holes and higher photoactivity.

Catalytic reduction of sulfur dioxide with carbon monoxide over tin dioxide for direct sulfur recovery process

SO(2) reduction by CO over SnO(2) catalyst was studied in this work. The parameters were the reaction temperature, space velocity (GHSV) and [CO]/[SO(2)] molar ratio. The optimal temperature, GHSV and [CO]/[SO(2)] molar ratio were 550 degrees C, 8000 h(-1) and 2.0, respectively. Under these conditions, the SO(2) conversion and sulfur selectivity were about 78% and 68%, respectively. The following reaction pathway involving two mechanisms was proposed in SO(2) reduction by CO over SnO(2) catalyst: in the first step involving Redox mechanism, the elemental sulfur was produced by the mobility of the lattice oxygen between SO(2) and SnO(2) surface. In the second step, COS was formed by the side reaction between elemental sulfur and CO or metal sulfide and CO. In the third step involving COS intermediate mechanism, the abundant elemental sulfur was produced by the SO(2) reduction by COS which was produced in the second step and was more effective reducing agent than CO.

Preparation and Reactivity Test of Nano Size ZnO for Removal of H2S and COS in a Gasified Fuel Gas

A nano-size zinc oxide was formulated for the effective removal of a very low concentration of sulfur compounds (H2S, COS) contained in a gasified fuel gas and their reactivity was also investigated in this study. They were prepared by a matrix-assisted method with various precursors. An active carbon was used for a matrix and zinc nitrate, zinc chloride, and zinc sulfate were selected as precursors. Zinc nitrate was the best precursor for the formulation of the nano-size zinc oxide in the experiments. The size of the formulated nano-size zinc oxides was in the range of 20-30 nm and its surface area was about 56.2 m2/g. From TGA(thermal gravity analysis) test, it was found that its sulfur capacity was about 5.83 gS/100 g-sorbent and sulfur absorption rate was about 0.363 gS/min·100 g-sorbent. Their reactivity increased with the smaller size and the larger surface area of the sorbents. Most prepared nano-size zinc oxides showed an excellent performance for the removal of not only H2S but also COS. Their absorption rate was faster than commercial zinc oxides. In order to investigate the sulfur absorption characteristics of zinc oxide, a experiments for the nano-size zinc oxides formulated from zinc nitrate precursors were carried out in a packed-bed reactor system over the temperature of 500 . It was concluded that the zinc oxide prepared by zinc nitrate as a precursor showed the highest sulfur removing capacity.

Effect of efficient supply of pure O2 concentrated by PSA-type O2 separator on improvement of indoor air quality

To minimize the cost and loss rate of energy artificial room ventilation system, the O2 separator was suggested for the flow of the excessive ventilation amount between indoor and outdoor because the pure O2 separated and concentrated by the O2 separator can be supplied with the ventilation amount minimized. How the O2 separator applies to ventilation and its operation characteristics were investigated by controlling under various conditions as well as the operation conditions optimized required for indoor air quality such as the concentration of CO2 and O2. Consequently, it was known that the O2 concentration was increased; however, the increase of the CO2 concentration was suppressed by the sufficient supply of O2 concentrated from the storage tank into the room despite the two persons’ breathing in the room having an inner volume of about 56 m3. Consequently, it was concluded that the supply system of the concentrated O2 which was stored into the tank after the production with the O2 separator can be applied to the room ventilation system for the improvement of the indoor air quality.

Performance test of PSA-type O2 separator for efficient O2 supply to room ventilation system combined with CO2 adsorption module

High purity O2 concentrated by the PSA-type O2 separator was applied to a room ventilation system combined with CO2 adsorption module to remove the indoor CO2 for the indoor air quality. And then the room was occupied by several persons to breathe for the O2 consumption and CO2 generation. As a result, the indoor air quality was improved by the ventilation system combined with the O2 supply and the CO2 adsorption module. It was due to the fact that the CO2 concentration was not steeply increased, but also even decreased and then the increasing rate of the O2 concentration with the O2 supply was simultaneously increased by the CO2 removal despite the CO2 generation and O2 consumption with the four persons’ breathing. As a representative result, in the case of supplying the high purity O2 of 30 L/min under using the CO2 adsorption module, the best performance with the highest increasing rate of O2 concentration and the lowest increasing rate of CO2 concentration was obtained among the various cases, and then the increasing rates of CO2 concentration and O2 concentration were −2.3 ppm/min and 33.3%/min, respectively.

A study on the SO2 reduction by CO over SnO2-ZrO2 catalysts

SO 2 which is an air pollutant causing acid rain and smog can be converted into elemental sulfur in direct sulfur recovery process (DSRP). SO 2 reduction was performed over catalyst. In this study, SnO 2 -ZrO 2 catalysts with Sn/Zr mole ratio were prepared by a co-precipitation method and CO was used as reduction agent. The reactivity profile of SO 2 reduction was investigated at the various reaction conditions. SnO 2 -ZrO 2 (Sn/Zr=2/1) catalyst showed the best performance for SO 2 reduction. As a result, SO 2 conversion and sulfur yield were about 100% and 97%, respectively, under the optimized conditions such as 325 °C and 10000 cm 3 /g -cat . h.