Pil Kim

Synthesis and characterization of mesoporous alumina as a catalyst support for hydrodechlorination of 1,2-dichloropropane: Effect of catalyst preparation method

A mesoporous alumina was synthesized by a posthydrolysis method. The prepared mesoporous alumina was found to have randomly ordered pores, and retained relatively high surface area with narrow pore size distribution centered at ca. 4 nm. Nickel precursors were then supported on the mesoporous alumina by an impregnation (Ni-IMP) and vapor deposition (Ni-VD) method. Several characterizations were carried out in order to investigate physical and chemical properties of mesoporous alumina and supported Ni catalysts. TPR, XPS, and UV-DRS measurements revealed that the Ni-IMP catalyst retained much more amounts of surface nickel aluminate-like species than the Ni-VD sample. TPD experiments also showed that nickel aluminate species affected the adsorption amounts of reactant (1,2-dichloropropane). In the hydrodechlorination of 1,2-dichloropropane (DCPA), DCPA conversion over the Ni-VD catalyst was about two times higher than that over the Ni-IMP catalyst at 300 °C. It is probably due to the fact that the Ni-VD catalyst, which had low contents of nickel aluminate species compared to the Ni-IMP catalyst, exhibited higher degree of reduction than the Ni-IMP catalyst at pretreatment conditions. The difference in DCPA conversion between two catalysts was closely related to the degree of reduction of nickel species and the amounts of adsorption of DCPA onto the catalyst as well.

A novel method for synthesis of a Ni/Al2o3 catalyst with a mesoporous structure using stearic acid salts

Nickel stearate was used as a chemical template and metal source for the easy-and-fast preparation of Ni/Al2O3 catalyst with a mesoporous structure. Ni-Nx and Ni-Hx were prepared using an NH4OH-treated precipitate and a HCl-treated solution as the chemical template, respectively, and these materials show only the effect of the chemical template, a regular pore size distribution. Ni-Nx with both a developed framework and textural porosity show a larger surface area and pore volume but a less irregular pore structure than Ni-Hx which shows a well-developed framework porosity. The 27Al NMR MAS analysis showed that nickel oxide supported on active alumina allows Ni2+ ions to diffuse into the surface lattice vacancies of the alumina spinel structure. Such a migration of metal ions may be limited to the first few layers of the supports, but leads to the production of hard-to-reduce metal oxide (i.e. a high metal-to-support interaction). Ni-Nx was also found to have a more dispersed nickel particle configuration than Ni-Hx after reduction.

Finely-dispersed Ni/Cu catalysts supported on mesoporous silica for the hydrodechlorination of chlorinated hydrocarbons

Abstract Ni/Cu and Ni catalysts supported on the mesoporous silica were prepared via grafting, metal adsorption and calcination steps. The prepared catalyst was characterized using XRD, TEM, N 2 sorption, and SAXS. Pore structure of the support was maintained throughout the preparation procedures. In addition, no specific metal particle image was appeared in XRD, because the metal particles are highly dispersed in the support as a very small size. Hydrodechlorination of TCEa (Trichloroethane) was selected as a model system to test the catalytic activity and selectivity to VCM. The activity of Ni/Cu-E-SBA is higher than that of Ni-E-SBA. The decrease in activity of Ni/Cu-E-SBA was much slow, because copper was added in the Ni catalyst. Cu may plays an important role to retard the deactivation by, such as coking. Further research is on progress. 97% selectivity to VCM was achieved after about 600min on Ni/Cu-E-SBA catalyst.

Preparation of NaCl-incorporated plugged mesoporous silica using a cost-effective precursor and applications to the hydrodechlorination of chlorinated hydrocarbons

The preparation of SBA-15 type plugged mesoporous silica using an inexpensive silica source in a two-step process is described. The resulting material was used as a catalyst support for a hydrodechlorination (HDC) reaction. The structure and morphology of the mesoporous silica and catalysts were determined using trasmission electron microscopy (TEM), small angle X-ray scattering (SAXS) and scanning electron microscopy (SEM). The contents and particle size of the metal incorporated into the catalysts were measured by ICP atomic emission spectrometry (ICP-AES) and X-ray diffraction analysis (XRD). The material (hereafter referred to as 2MS) included about 2% Na in the form of NaCl. The pore structures of SBA-15 and 2MS were similar but 2MS showed an atypical plugged shape of the N2 desorption isotherm. Furthermore, the pore wall thickness was quite high (5 nm), and particles were large and in close proximity to each other in the 2MS. The micropore area ratio measured using a t-plot method was large, over 25%. When a 2MS-supported palladium catalyst was used for hydrodechlorination of 1,1,2-trichloroethane, the catalyst had a stronger resistance to deactivation.

Synthesis of mesoporous γ-aluminas of controlled pore properties using alkyl carboxylate assisted method

Abstract Mesoporous γ-alumina (MA) was prepared by alkyl carboxylate assisted method. Pore properties of MAs could be controlled by carbon tail length of template, the molar ratio of sec-butanol to isooctane or water to aluminum precursor, and calcination conditions. The crystalline phase of MA after calcinations was γ-AI 2 O 3 . The pore size of MAs decreased from 7.7 nm to 3.5 nm with the decrease in the ratio of water to aluminium ion, while the pore uniformity was enhanced. Isooctane as a co-solvent acted as an expander of the pores. In addition, as increasing the molar ratio of sec-butanol to isooctane, pore size increased from 2.3 nm to 3.5 nm and both pore uniformity and framework porosity was improved.

Toxicity Assessment of Titanium (IV) Oxide Nanoparticles Using Daphnia magna(Water Flea)

Objectives Titanium dioxide (TiO2), a common nanoparticle widely used in industrial production, is one of nano-sized materials. The purpose of this study was to determine the acute and chronic toxicity of TiO2 using different size and various concentrations on Daphnia magna. Methods In the acute toxicity test, four concentrations (0, 0.5, 4, and 8 mM) for TiO2 with 250 or 500 nm and five concentrations (0, 0.25, 0.5, 0.75, and 1 mM) for TiO2 with 21 nm were selected to analyze the toxic effect to three groups of ten daphnia neonates over 96 hours. In addition, to better understand their toxicity, chronic toxicity was examined over 21 days using 0, 1, and 10 mM for each type of TiO2. Results Our results showed that all organisms died before the reproduction time at a concentration of 10 mM of TiO2. In addition, the exposure of anatase (21 nm) particles were more toxic to D. magna, comparing with that of anatase (250 nm) and rutile (500 nm) particles. Conclusions This study indicated that TiO2 had adverse impacts on the survival, growth and reproduction of D. magna after the 21days exposure. In addition, the number of test organisms that were able to reproduce neonates gradually were reduced as the size of TiO2 tested was decreased.

Comparison of Mesoporous Aluminas Synthesized using Stearic Acid and Its Salts

Mesoporous aluminas, X-MAs (X=Na, Mg, and Ni) were prepared using stearic acid and its salts as templates. Sodium stearate, which is more soluble than stearic acid, was an effective template for preparing Na-MA. The characteristics of Mg-MA prepared using cost-effective template (magnesium stearate) were similar to those for an MA prepared using stearic acid. Mg ions were easily exchanged with Ni ion by treatment with an acid or base. Thus, nickel incorporated alumina (Ni-MA) could be directly prepared using nickel stearate, which was acting as a chemical template and a metal source. The MA and X-MAs had a similar pore size (3.6 nm), a narrow pore size distribution (DFWHM∼1 nm), and a γ-alumina phase. In addition, bimetallic Ni-MAn catalysts were prepared and applied to the partial oxidation methane as a potential application.

Synthesis of mesoporous alumina by using a cost-effective template

A salt of stearic acid, i.e., magnesium stearate [(C17H35COO)2Mg], can be used as a chemical template for the formation of mesoporous alumina, and is a less expensive reagent than stearic acid. Mesoporous alumina prepared using this cost-effective surfactant shows similar pore properties with respect to pore size (3.5 nm) and surface area (above 300 m2Vg) to that prepared using stearic acid. In addition, textural porosity, arising from non-crystalline intraaggregate voids and spaces, was effectively removed by the addition of magnesium nitrate. The entire transformation from aluminum hydroxide to active alumina was performed at 550 °C, and the crystallinity of the product was confirmed by powder XRD analysis.27A1 MAS NMR result shows the phase of mesoporous alumina is the γ-alumina form.

Controlling the pore sizes of SBA-15 mesoporous silica by the addition of poly(propylene oxide)

Abstract Poly(propylene oxide) (PPO) was added during the synthesis of SBA-15 type mesoporous silica in order to increase the pore diameter. Synthesized mesoporous materials showed different morphologies and pore properties compared to the SBA-15 mesoporous silica without PPO addition due to the presence of PPO. The pore properties were affected by the amount of added PPO in the synthetic mixtures and those values were increased compared to the SBA-15 without PPO addition. The hexagonal pore structure of the SBA-15 mesoporous silica was not altered by the PPO addition, which was confirmed by the TEM and SAXS analysis. However, size of the primary particles was increased in the axial direction resulted in a longer particles.

Development of a Priority Substances List for Integrated Environmental Management

The Ministry of the Environment in Korea supports investigation of various substances that are potential contaminants of the environment and could cause adverse effects on the environment and/or human health and to list Priority Substances (PSL). The present study for PSL is aimed at estimating the new PSL for industrial areas or assessing the risk of refining processes for selecting priority substances in order to obtain better criteria of quality data. The present study lists 81 major priority substances among 106 candidate substances and scores with weight factors to CHEMS-1 based on amounts of materials in circulation and emissions levels. Of the 81 chemicals, 80% are classified as carcinogens, potentially causing acute oral toxicity among those within the 1st grade of data quality criteria for materials. For data quality criteria of items, BOD or hydrolysis half-life is the lowest 40% and acute oral toxicity is the highest 90%.