• Applied Chemistry for Engineering
• /
• v.7 no.2
• /
• pp.261-268
• /
• 1996

Various $Cu/SiO_2$ catalysts with copper concentration ranging from 0 to 50wt% were prepared by kneading method for the steam reforming of methanol. These catalysts were calcined at temperatures in the range of $400^{\circ}C{\sim}900^{\circ}C$ and then reduced in a $H_2$ atmosphere in the range of $150^{\circ}C{\sim}350^{\circ}C$. Steam reforming of methanol was carried out at atmospheric pressure over a temperature range of $200^{\circ}C{\sim}400^{\circ}C$, steam/methanol molar ratio of 0.4~1.6 and W/F of 3~25 g.-cat.hr./mol. Characterization of the catalysts was studied using IR, BET and XRD. Using copper nitrate as a precursor for catalysts, pH in the preparation of catalysts had a great effect on the catalytic activity, but pH in the preparation of catalysts, calcination temperature, and reducing temperature in $H_2$ atmosphere had no effect on the product distribution. Optimum copper concentration, calcination temperature and reducing temperature were 40wt%, $700^{\circ}C$ and $300^{\circ}C$, respective)y. Reaction temperature for maximum $H_2$ production was $275^{\circ}C$, and the formation of methane which lowered quantity and quality of $H_2$ would be inhibited below $275^{\circ}C$. $Cu^{\circ}-Cu_2O$ might be active species in $Cu/SiO_2$ catalyst.

• Korean Journal of Materials Research
• /
• v.4 no.6
• /
• pp.669-680
• /
• 1994

Oxidation behaviour of TiAl intermetallic compounds with the addition of Cr, V, Si, Mo, or Nb was investigated at 900~$1100^{\circ}C$ under the atmospheric environment. The reaction products were examined by XRD, SEM equipped with WDX. The weight gain by continuous oxidation increased with the addition of Cr or V, but there was less weight gain when Mo, Si or Nb was added individually. he oxidation rate of Cr- or V-added TiAl was always larger than that of TiAI. However, oxidation rate of Si-, Mo- or Nb-added TiAl was almost same or smaller than that of TiAI. Thus, it is concluded that the addition of Cr or V did not improve the oxidation resistance, whereas the addition of Si, Mo or Nb improved the oxidation resistance. Oxides formed on TiAl with Mo, Si, and Nb were found to be more protective, resulting from the decrease in diffusion rate of the alloying elements and oxygen. Nb strengthened the tendency to form $AI_{2}O_{3}$ in the early stage of oxidation, due to the continuous $AI_{2}O_{3}$ layer formation and dense $Tio_{2}+AI_{2}O_{3}$ layer. According to the Pt-marker test of TiAI- 5wt%Nb, oxygen diffused mainly inward while oxides were formed on the substrate surface. Upon thermal cyclic oxidation at $900^{\circ}C$, it is shown that the addition of Cr or Nb improved the adherence of oxide scale to the substrate.

• Journal of Energy Engineering
• /
• v.15 no.1 s.45
• /
• pp.52-59
• /
• 2006

This paper examined the conversion of methane to hydrogen and other higher hydrocarbons using dielectric barrier discharge with AC pulse power. Two metal electrodes of a coaxial-type plasma reactor were separated by gas gap and an alumina tube. The inner electrode was located inside the alumina tube. The alumina tube was located inside the stainless steel tube, which was used as the outer electrode. Effect of feed gas composition (methane, oxygen, argon, water and helium), flow rate, applied frequency, input volt-age on methane conversion and product distribution were studied. The major products of plasma chemical reactions were ethylene, ethane, propane, buthane, hydrogen, carbon monoxide and carbon dioxide. The increment of applied voltage and the usage of inert gas as the background (helium and argon) enhanced the selectivity of hydrocarbons and methane conversion. The addition of water in the feed stream enhanced the conversion of methane and yield of hydrogen. Higher voltage leads to higher yield of $C_2H_6,\;C_3H_8,\;C_4H_{10}$ and yield or $C_2H_2\;and\;C_2H_4$ appeared highly in lower voltage.

• Journal of Korean Society of Environmental Engineers
• /
• v.37 no.8
• /
• pp.492-497
• /
• 2015

VOCs (Volatile Organic Compounds) are generally generated in the painting process, or at the company and laundry where use organic solvents. The VOCs consist of various hydrocarbons and has low calorific value due to its dilution with atmospheric air. Therefore, the VOCs are difficult to burn by a conventional fuel combustor. In this study, a novel plasma dump combustor was proposed for the treatment of low calorific VOC gases. This combustor was designed a combination of the characteristics in a plasma burner, a dump combustor and a 3D matrix burner. The combustor has good structure for maintaining enough residence time and reaction temperature for stable flame formation and VOC destruction. For investigating the performance characteristics of the plasma dump combustor, an experiment was achieved for VOC feed rate, VOC injector position, etc. Toluene was used as a surrogate of VOC. The novel combustor gave better performance than a conventional combustor, showing that VOC destruction rate and energy efficiency were 89.64% and 12.27 kg/kWh respectively, at feeding rate of 450 L/min of VOC of 3,000 ppm of toluene concentration.

• Journal of Energy Engineering
• /
• v.14 no.1
• /
• pp.1-10
• /
• 2005

The combustion reactivity of char depending on the pyrolysis pressure was investigated with Pressurized Thermogravimetric Analyser. The amounts of volatiles released at pyrolysis pressure of 1, 8 and 15 atm were, first, measured with Alaska, Adaro and Denisovsky coals. Reactivities of chars produced at var-ious pyrolysis pressure were evaluated at atmospheric pressure and 500℃, and analysed in terms of char crystal structure, surface area, pore characteristics and chemical composition of char. Finally, the combustion reactivities of three chars were examined at pressure of 1 atm, 8 atm and 15 atm. From this study, it was recognized that the amount of volatiles released decreases with increase in pyrolysis pressure, and reaction rate of char produced at higher pyrolysis pressure was lower than that at lower pyrolysis pressure. It might be resulted from the difference in char surface area and pore characteristics rather than char crystal structure and chemical characteristics. At 15 atm, kinetic parameters of Alaska char were obtained with the grain model, and these were 56.8 KJ/mole for activation energy and 222.34 (1/min) for frequency factor.

• Korean Journal of Materials Research
• /
• v.25 no.2
• /
• pp.75-80
• /
• 2015

The carbon dioxide($CO_2$) released while producing building materials is substantial and has been targeted as a leading contributor to global climate change. One of the most typical method to reducing $CO_2$ for building materials is the addition of slag and fly ash, like pozzolan material, while another method is reducing $CO_2$ production by carbon negative cement development. The MgO-based cement was from the low-temperature calcination of magnesite required less energy and emitted less $CO_2$ than the manufacturing of Portland cements. It is also believed that adding reactive MgO to Portland-pozzolan cements could improve their performance and also increase their capacity to absorb atmospheric $CO_2$. In this study, the basic research for magnesia cement using $MgCO_3$ and magnesium silicate ore (serpentine) as main starting materials, as well as silica fume, fly ash and blast furnace slag for the mineral admixture, were carried out for industrial waste material recycling. In order to increase the hydration activity, $MgCl_2$ was also added. To improve hydration activity, $MgCO_3$ and serpentinite were fired at $700^{\circ}C$ and autoclave treatment was conducted. In the case of $MgCO_3$ as starting material, hydration activity was the highest at firing temperature of $700^{\circ}C$. This $MgCO_3$ was completely transferred to MgO after firing. This occurred after the hydration reaction with water MgO was transferred completely to $Mg(OH)_2$ as a hydration product. In the case of using only $MgCO_3$, the compressive strength was 3.5MPa at 28 days. The addition of silica fume enhanced compressive strength to 5.5 MPa. In the composition of $MgCO_3$-serpentine, the addition of pozzolanic materials such as silica fume increased the compression strength. In particular, the addition of $MgCl_2$ compressive strength was increased to 80 MPa.

• Journal of Conservation Science
• /
• v.30 no.1
• /
• pp.95-101
• /
• 2014

Silver objects tarnish with black from reaction with sulfurous acid or hydrogen sulfide of atmospheric. Blackening of silver objects results from formation of silver sulfide($Ag_2O$) on the surface. Silver sulfide usually is usually removed by conservation treatment. There are several cleaning methods such as chemical, electrochemical and micro-abrasion cleaning, but all of them consume silver. This study investigated the safe and effective parameter of laser cleaning by test on silver coupons. Laser cleaning is a selective process for the removal of specific substances. At first, laser cleaning applied to plain silver coupons, which were not corroded, to find out the safe range of laser energy density. From results, plain silver coupons were not changed at 1064nm below $4.00J/cm^2$ and at 532nm below $2.39J/cm^2$. The corrosion layer(silver sulfide) of artifical corroded silver coupons was removed at 1064nm with $2.39J/cm^2$ by 5~10 pulses and at 532nm with $1.19J/cm^2$ by 5~10 pulses. The removal thickness of corrosion layer was about 13-25nm per a laser pulse using AES analysis. In addition, laser cleaning tested the tarnish silver rings based on the results of silver coupons. As a result of test, the black surface were clean successfully and gave luster of silver, which showed the application possibility of laser cleaning for silver objects.

• The Journal of Engineering Geology
• /
• v.20 no.1
• /
• pp.79-87
• /
• 2010

Field water qualities (temperature, pH, Eh, EC, DO) was monitored by 6 times March to September 2009 on background water (BW) and acid mine drainage (AMD0, AMD1, AMD2 and AMD3 points), and flow rate was measured on AMD0 point. Acid mine drainage flowed out from abandoned Ilgwang mine were high acid waters that lower than pH 3, and Eh component was ranged 400 to 600 mV. EC measured on acid mine drainage were higher over 10 times than background water, DO component was increased by reaction on the air during the water flow from AMD0 point to AMD4 point. Heavy metal concentrations in acid mine drainage were ordered Fe > Cu > Zn > Mn > As > Cd, and Fe concentration was highest for 81.870~474.30 mg/L. Monitoring periods measured maximum concentrations of heavy metals were May for As and Cd, June for Fe, July for Cu, Zn and Mn. The periods measured minimum concentrations were monitored April for Cd and Mn, September for Fe, Cu, Zn and As. Discharge mass of heavy metal components were calculated 53.44 kg for Fe, 6.25 kg for Cu, 5.26 kg for Zn, 2.13 kg for Mn, 0.14 kg for As and 0.04 kg for Cd, respectively. Total discharge mass of heavy metal components were calculated 67.26 kg for 1 day, and Fe component was taken 79% of total mass.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.17-18
• /
• 2011

Plasma in liquid phase has attracted great attention in the last few years by the wide domain of applications in material processing, decomposition of organic and inorganic chemical compounds and sterilization of water. The plasma in liquid is characterized by three main regions which interact each - other during the plasma operation: the liquid phase, which supply the plasma gas phase with various chemical compounds and ions, the plasma in the gas phase at atmospheric pressure and the interface between these two regions. The most complex region, but extremely interesting from the fundamental, chemical and physical processes which occur here, is the boundary between the liquid phase and the plasma gas phase. In our laboratory, plasma in liquid which behaves as a glow discharge type, is generated by using a bipolar pulsed power supply, with variable pulse width, in the range of 0.5~10 ${\mu}s$ and 10 to 30 kHz repetition rate. Plasma in water and other different solutions was characterized by electrical and optical measurements. Strong emissions of OH and H radicals dominate the optical spectra. Generally water with 500 ${\mu}S/cm$ conductivity has a breakdown voltage around 2 kV, depending on the pulse width and the repetition rate of the power supply. The characteristics of the plasma initiated in ultrapure water between pairs of different materials used for electrodes (W and Ta) were investigated by the time-resolved optical emission and the broad-band absorption spectroscopy. The deexcitation processes of the reactive species formed in the water plasma depend on the electrode material, but have been independent on the polarity of the applied voltage pulses. Recently, Coherent anti-Stokes Raman Spectroscopy method was employed to investigate the chemistry in the liquid phase and at the interface between the gas and the liquid phases of the solution plasma system. The use of the solution plasma allows rapid fabrication of the metal nanoparticles without being necessary the addition of different reducing agents, because plasma in the liquid phase provides a reaction field with a highly excited energy radicals. We successfully synthesized gold nanoparticles using a glow discharge in aqueous solution. Nanoparticles with an average size of less than 10 nm were obtained using chlorauric acid solutions as the metal source. Carbon/Pt hybrid nanostructures have been obtained by treating carbon balls, synthesized in a CVD chamber, with hexachloro- platinum acid in a solution plasma system. The solution plasma was successfully used to remove the template remained after the mesoporous silica synthesis. Surface functionalization of the carbon structures and the silica surface with different chemical groups and nanoparticles, was also performed by processing these materials in the liquid plasma.

• Applied Chemistry for Engineering
• /
• v.10 no.8
• /
• pp.1129-1135
• /
• 1999

The reduction of $SO_2$ by CO over supported cobalt catalysts was investigated within the temperature range of $350{\sim}550^{\circ}C$, initial $SO_2$ concentration of 1000~10000 ppm, $CO/SO_2$ molar ratio of 1.0~3.0 and space velocity of $5000{\sim}15000h^{-1}$. Several types of supports such as ${\gamma}-Al_2O_3$, $TiO_2$ were tested. The $SO_2$ conversion and selectivity to elemental sulfur were investigated using a differential fixed bed reactor at atmospheric pressure. The catalyst prepared by wet impregration of 5 wt % cobalt on ${\gamma}-Al_2O_3$ showed $SO_2$ conversion higher than 90% and COS yield lower than 6% at temperature above $400^{\circ}C$. The optimum $CO/SO_2$ molar ratio was investigated as 2.0. At higher $CO/SO_2$ molar ratio, the $SO_2$ conversion became higher but the main product was COS. The effect of $SO_2$ concentration and space velocity over $SO_2$ conversion and COS yield was not appreciable in the experimental range. The activated cobalt phase was detected as $CoS_2$ and the $CoS_2$ phase unchanged even after reaction.