Man Sig Lee

Synthesis of TiO2/SiO2 nanoparticles in a water-in-carbon-dioxide microemulsion and their photocatalytic activity

TiO2 and TiO2/SiO2 nanoparticles were prepared by controlled hydrolysis of titanium tetraisopropoxide and tetraethylorhtosilicate in water-in-carbon-dioxide microemulsion using ammonium carboxylate perfluoro-polyether (PFPE-NH4) as a surfactant. These particles were characterized by HRTEM, XRD, FT-IR, TGA and DTA. The particles calcined at 500°C were identified as a nanocrystalline anatase phase, regardless of the titanium tetraisopropoxide/teraethylorthosilicate (TTIP/TEOS) molar ratio. The crystallite size decreased with an increase of the silica content. From FT-IR analysis, the band for Ti-O-Si vibration was observed and the band intensity for Si-O-Si vibration increased with an increase of the silica content. The micrographs of HRTEM showed that the TiO2/SiO2 nanoparticles had a spherical morphology with a narrow size distribution and the lattice fringe was 0.35 nm, which corresponds to the lattice spacing of (101) plane in the anatase phase. In addition, TiO2/SiO2 particles showed higher photocatalytic activity than pure TiO2 and the TiO2/SiO2 (80:20) particles showed the highest activity on the photocatalytic decomposition of p-nitrophenol.

Surfactant effects on SF6 hydrate formation

Sulfur hexafluoride (SF(6)) has been widely used in a variety of industrial processes, but it is one of the most potent greenhouse gases. For this reason, it is necessary to separate or collect it from waste gas streams. One separation method is through hydrate crystal formation. In this study, SF(6) hydrate was formed in aqueous surfactant solutions of 0.00, 0.01, 0.05, 0.15 and 0.20 wt% to investigate the effects of surfactants on the hydrate formation rates. Three surfactants, Tween 20 (Tween), sodium dodecyl sulfate (SDS) and linear alkyl benzene sulfonate (LABS), were tested in a semi-batch stirred vessel at the constant temperature and pressures of 276.2 K and 0.78 MPa, respectively. All surfactants showed kinetic promoter behavior for SF(6) hydrate formation. It was also found that SF(6) hydrate formation proceeded in two stages with the second stage being the most rapid. In situ Raman spectroscopy analysis revealed that the increased gas consumption rate with the addition of surfactant was possibly due to the increased gas filling rate in the hydrate cavity.

Synthesis of Nanosized TiO2-Ag-SiO2 Sols by Modified Sol-Gel Method and their Application for Methane Hydrate Formation

Nanosized TiO2-Ag-SiO2 sols were prepared with modified sol-gel method using reduction agent. The physical properties of the prepared particles were investigated by TEM, XRD and FT-IR. The titanium tetraisopropoxide (TTIP, 98% Aldrich), teraethylorthosilicate (TEOS, 98% Aldrich) and silver nitrate were used as precursors of titania, silica and silver, respectively. Sodium citrate tribasic dihydrate (C6H5Na3.2H2O, Aldrich) was used as a reduction agent. This paper presents the effect of nanosized TiO2-Ag-SiO2 sols on the formation of methane hydrate in a semi-batch vessel. The micrographs of TEM showed that the TiO2-Ag-SiO2 particles possessed a spherical morphology with a narrow size distribution. The crystallite size of particles decreased with an increasing the SiO2 content. In addition, the water solution with 1.0 wt% of TiO2-Ag-SiO2 particles acted as promoter for methane hydrate formation.

Effects of Organic Additives on the Residual Stress of Ni and Ni Alloys Electrodeposited from the Sulfamate Bath

The residual stress in the deposits of Ni and Ni alloys was estimated from the deflection of one side deposited test strips (Specialty testing & Development Co.). 2,6-Naphthalene- disodiumsulfate (2,6-NDS) and 1,3,6-Naphthalenetrisodiumsulfate (1,3,6-NTS) were adopted instead of saccharin and , among the three additives, the lowest residual stress was obtained with 1,3,6-NTS. However, to adjust compressive stress, certain quantity of amine additives such as MEA (Monoethanolamine), DEA (Diethanolamine) and TEA(Triethanolamine) were added stepwise to the bath containing 1,3,6-NTS while electrodepositon proceeded. Effects on reducing residual stress was in order of MEA<DEA<TEA, which seemed to have a connection with lone pair and basicity of the nitrogen attached to the amine additives. The highest Vickers hardness was attained with the Ni-Co alloy deposit from the Ni-Co(Ni:80g/L-Co:4.8g/L) bath and the cobalt content of the deposit was 28.4%(wt./wt.). Properties and cobalt content of the deposits were evaluated and analyzed with SEM, XRD, EDS and ICP respectively.

Synthesis of Zn/Al mixed-oxide catalyst for carbonylation of glycerol with urea

Zn/Al mixed oxide was prepared by the coprecipitation or the hydrothermal method under different conditions and used as catalyst for synthesis of glycerol carbonate by carbonylation of glycerol with urea. The physical properties of the prepared Zn/Al mixed oxide particles were investigated, as well as their activity as catalyst in the mentioned synthesis. The dried Zn/Al mixed-oxide particles prepared by the coprecipitation method showed higher activity in synthesis of glycerol carbonate than those prepared by the hydrothermal method. The Zn/Al mixed oxide prepared by the coprecipitation method without NaNO3 showed the highest catalytic activity in synthesis of glycerol carbonate.

Synthesis of Palladium Nanoparticles in Various Carbon Materials

The outstanding properties of Pd-base catalysts make is attractive for applications in various field, such as hydrogen storage, catalysis, fuel cell, chemical sensing and so forth. Therefore, research studies have been carried out on its preparation and characterization. Commonly, the Pd must be deposited on support materials with a large surface area to provide high metal dispersion and a high electrical conductivity to facilitate electron transfer, which carbon materials. The purpose of this study is to investigate not only synthesis of various carbon materials(graphene, carbon nanotube(CNT), active carbon, carbon black) supported Pd but also the confirmation of the properties. The characterization of Pd catalysts composites was performed by X-ray diffra ction(XRD), Brunauer-Emmett-Teller(BET), scanning electron microscopy (SEM) and transmission electron microscopy(TEM). According to TEM image, Pd nanoparticles were highly dispersed on surface of graphene

Synthesis of Polyglycerol Fatty Acid Ester for Insulating Oil

Offshore wind power is eco-friendly new regeneration energy producing electricity using a strong wind of the sea. Offshore wind power consists of pitch controller, nacelle, blade and transformer. Insulating oil for transformer needed to low pour point, high flash point and biodegradable considering the low temperature of the sea and environmental pollution. In this study, polyglycerol fatty acid ester was prepared polyglycerol and fatty acid using various catalysts for insulating oils. We investigated the effect of catalysts on the yield of polyglycerol fatty acid ester. In addition, we were measured the pour point and flash point of the prepared polyglycerol fatty acid ester.

Surface Modification of SiO2 for Highly Dispersed Pd/SiO2 Catalyst

Surface modification of SiO₂ supports was shown to significantly affect the properties of Pd/SiO₂ catalysts. The surface of SiO₂ can be modified by various pretreatment methods. In this study, the effect of different calcination temperatures on support surface was investigated. Pd supported on pretreated SiO₂ was characterized by H2 temperature-programmed reduction (TPR), XRD, CO chemisorption measurements, and field-emission transmission electron microscopy (FE-TEM). The silanol group (-OH), which is one of the functional groups of SiO₂, interferes with the reduction of palladium because it strongly bonds with palladium ions (-PdO) during the preparation of the catalyst. Due to the complete removal of silanol (Si-OH) groups following calcination at 700 °C, the metal reducibility was enhanced, and the catalyst pretreated at this calcination temperature exhibited the highest metal dispersion of 13.02%. Further, to confirm the catalytic activity of the prepared catalysts, hydrogenation of D-glucose was conducted. The HPLC results demonstrated that Pd/SiO₂_700 has the highest catalytic activity toward hydrogenation of D-glucose. Therefore, it was confirmed that the removal of silanol groups increase the metal dispersion and catalytic activity of Pd/SiO₂ catalyst.

The Effect of Support Pretreatment with Ammonia on Pd/SiO2 Catalyst

We have reported the effect of support pretreatment with ammonia on Pd/SiO2 catalyst in this study. SiO2 was pretreated with ammonia water to increase the Pd dispersion before the preparation of Pd/SiO2 catalysts. The effect of support pretreatment with ammonia on Pd/SiO2 catalyst was investigated by XRD, FT-IR, N2-adsorption and FE-TEM. The Pd supported on pretreated SiO2 were characterized by XRD, CO-chemisorption and FE-TEM. The pretreatment of SiO2 with ammonia water lead to decrease of silanol groups (Si-OH) up to temperature 200 °C. This decline of silanol groups on the SiO2 affects highly dispersed Pd/SiO2 as 6.52 %. The result showed that the decrease of silanol group on the SiO2 was favorable for the Pd dispersion. It is reason that absence of the silanol groups contribute to the high metal reducibility.

The Preparation of Highly Dispersed Pd/Gamma-Al2O3 Catalyst: The Relation of Attracting-Repelling Force and Pd Dispersion

The purpose of this study is to present the effect of attracting-repelling force on the dispersion and particle size of palladium (Pd) between Pd and γ-Al2O3. The Pd supported on γ-Al2O3 catalyst were prepared by deposition-precipitation method with two different ways. From the CO-Chemisorption results, Pd/γ-Al2O3 (R2-FM) catalyst has the highest Pd dispersion of 43.16%. The results showed that particle size and distribution of Pd influenced by the surface charge state of γ-Al2O3 support, indicating relation of attracting-repelling force between Pd precursor and γ-Al2O3 surface.