• Journal of the Korean Chemical Society
• /
• v.32 no.6
• /
• pp.543-548
• /
• 1988

The metal-support interaction was studied in 1∼5wt% copper supported on $\gamma-alumina$ and titania systems by temperature programmed reduction (TPR) and EPR. When the samples were treated with oxygen at $500^{\circ}C$, the relative area of H2-TPR peak at higher temperature increased with copper content for titania system whereas that of lower temperature increased for ${\gamma}$-alumina system. After oxygen treatment at $500^{\circ}C,\;{\gamma}$-alumina system showed a TPR peak at $300^{\circ}C$ while two peaks at 120 and $180^{\circ}C$ were found in titania system. A typical $Cu^{2+}$ EPR signal was observed on ${\gamma}$-alumina but very broad and small one on titania. From the results, it was suggested that the metal-support interaction increases in the order of silica < titania < ${\gamma}$-alumina and copper oxide has different loading characteristics depending on the supports.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.13 no.5
• /
• pp.181-187
• /
• 2005

The behavior of fox adsorption and desorption of the NOx storage catalyst supported on Ba additive were studied by the TPA/TPD experiments and reactivity tests. Applying the transient responses and NOx TPA/TPD test by CLD were effective methods to analyze the characteristics of the NOx storage catalyst. NOx variation of the NOx storage catalyst in the lean air/fuel conditions according to temperature was dominated by NOx adsorption and desorption rather than catalytic reduction. The presence of reductants in the lean mixture promoted the NOx desorption at the $500^{\circ}C$ higher temperature. The temperatures for maximum NOx conversion with CH4 and $C_3H_6$ as a rich spike reductant appear around $500^{\circ}C\;and\; 400^{\circ}C$ respectively.

• Korean Journal of Crystallography
• /
• v.9 no.1
• /
• pp.44-47
• /
• 1998

A reduction/oxidation reaction between A1 metal powder and SiO2 powder was performed by Self-propagating High-temperature Synthesis (SHS) reaction induced by microwave energy to produce a composite of Al2O3 and Si powders by using a 2.45 GHz kitchen model microwave oven. A Microwave Hybrid Heating(MHH) method was applied by using SiC powders as a suscepting material to raise the temperature of the disk samples and the heat increase rate of over 100℃/min were obtained before the reaction. The reaction started around 850℃ and the heat increase rate jumped to over 200℃/min after the reaction took place.

• Korean Chemical Engineering Research
• /
• v.60 no.4
• /
• pp.620-629
• /
• 2022

By varying various experimental conditions such as heating rate, molar hourly space velocity (MHSV), and nitridation reaction temperature, vanadium oxynitride was prepared through temperature programmed reduction/nitridation reaction (TPRN) of vanadium pentoxide and ammonia, and characterization were performed. In order to investigate the physico-chemical properties of the prepared catalyst, N₂ adsorption-desorption analysis, X-ray diffraction analysis (XRD), hydrogen temperature programmed reduction (H₂-TPR), temperature programmed oxidation (TPO), ammonia temperature programmed desorption (NH₃-TPD), transmission electron microscopy (TEM) was performed. Transformation of V₂O₅ with 5 m² g^-1 low specific surface area by reduction at 340 ℃ to V₂O₃ showed a high specific surface area value of 115 m² g^-1 by micropore formation. As the nitridation temperature increased beyond that, the specific surface area continued to decrease due to sintering. The nitridation reaction variable that had the greatest influence on the specific surface area was the reaction temperature, and the x + y value of VN_xO_y of a single phase approached from 1.5 to 1.0 as the nitridation reaction temperature increased. At a high reaction temperature of 680 ℃, the cubic lattice constant a was VN. close to the value. At 680 ℃, the highest nitridation temperature among the experimental conditions, the ammonia conversion rate was 93%, and no deactivation was observed.

• Korean Chemical Engineering Research
• /
• v.54 no.5
• /
• pp.712-718
• /
• 2016

Platinum catalysts supported on the mesoporous material synthesized from Y zeolite were applied to synthesis of jet-fuel through n-octadecane hydroupgrading. The mesoporous aluminosolicate, $MMZ_{HY}$ was synthesized using Y zeolite as its framework source. The effect of the addition of Mg to $Pt/MMZ_{HY}$ catalyst for n-octadecane hydroupgrading was investigated. Catalyst characterization was performed with X-ray diffraction, $N_2$ adsorption, temperature-programmed reduction in hydrogen flow, temperature-programmed desorption of ammonia, and infrared spectroscopy of adsorbed pyridine. The high yield of jet-fuel over the $PtMg(2.0)/MMZ_{HY}$ can be attributed not only to the higher dispersion of Pt metal and higher reducibility, but also the higher amount of acid sites and higher strength of acid sites. The selectivity to iso-paraffin in the jet-fuel fraction could be reached above 80% over the optimized $PtMg/MMZ_{HY}$ catalyst.

• Journal of Hydrogen and New Energy
• /
• v.21 no.2
• /
• pp.89-97
• /
• 2010

$Al_2O_3$, $TiO_2$, $ZrO_2$, $Al_2O_3-TiO_2$, $Al_2O_3-ZrO_2$, 및 $TiO_2-ZrO_2$ 혼합 산화물을 지지체로 한 Ni 기반 혼합 산화물을 졸-겔법으로 제조하였다. 제조된 혼합 산화물은 1173K에서 열처리 한 후 구조적 특성 변화를 전자현미경 및 X-선 회절 분석을 이용하여 관찰하였으며, 수소를 이용한 승온 환원(TPR; temperature-programmed reduction) 실험을 통하여 1173K 까지 각 시료들의 환원 피크를 비교 고찰하였다. $Al_2O_3$ 또는 $TiO_2$ 가 혼합된 시료의 경우 1173K 에서의 열처리 후 니켈 알루미네이트 또는 니켈 티타네이트와 같은 새로운 결정상의 생성이 관찰되었으나 $ZrO_2$가 혼합된 경우에는 새로운 결정상의 생성이 관찰되지 않았다. TPR 결과에 의하면, $Al_2O_3$ 또는 $TiO_2$를 혼합된 시료의 경우 벌크 NiO의 TPR 결과와는 달리 생성된 새로운 결정상에 기인한 여러 개의 환원 피크가 나타났으나 $ZrO_2$를 혼합한 경우 벌크 NiO와 비슷한 환원 피크를 보였다. TPR 결과를 기초로 Arrhenius plot 으로부터 각 혼합 산화물들의 수소 환원 활성화 에너지를 도출하였다. $ZrO_2$를 지지체로 사용하는 경우 다른 혼합 산화물들보다 지지체로서 안정한 혼합 산화물상을 형성한다는 것을 지시하듯이 상대적으로 가장 낮은 활성화 에너지를 나타냈다.

• Korean Chemical Engineering Research
• /
• v.53 no.3
• /
• pp.372-381
• /
• 2015

The effect of preparation method on the catalytic activities of the $Ni/Al_2O_3$ catalysts on steam reforming of ethylene glycol was investigated. The catalysts were prepared with various preparation methods such as an incipient wetness impregnation, wet impregnation, and coprecipitation method. In the case of coprecipitation method, various precipitants such as KOH, $K_2CO_3$, and $NH_4OH$ were compared. The prepared catalysts were characterized by using $N_2$ physisorption, inductively coupled plasma-atomic emission spectroscopy, X-ray diffraction, temperatureprogrammed reduction, pulsed $H_2$ chemisorption, temperature-programmed oxidation, scanning electron microscopy, and thermogravimetric analysis. Among the catalysts reduced at 773 K, the $Ni/Al_2O_3$ catalyst prepared by a coprecipitation with KOH or $K_2CO_3$ as precipitants showed the best catalytic performance. The preparation method affected the particle size of Ni, reducibility of nickel oxides, catalytic performance (activity and stability), and types of coke formed during the reaction. The $Ni/Al_2O_3$ catalyst prepared by a coprecipitation with KOH showed the increasing catalytic activity with an increase in the reduction temperature from 773 to 1173 K because of an increase in the reduction degree of Ni oxide species even though the particle size of Ni increased with increasing reduction temperature.

• Korean Chemical Engineering Research
• /
• v.59 no.2
• /
• pp.281-295
• /
• 2021

In this study, the direct amination of ethanol was performed over impregnated Ni on SiO2-Al2O3 mixed oxide catalysts prepared by varying Si/(Si + Al) molar ratio to 30 mol%. To characterize the physico-chemical properties of the catalysts used, X-ray diffraction (XRD), N2-physisorption, temperature-programmed desorption of iso-propyl alcohol (IPA-TPD), temperature-programmed desorption of ethanol (EtOH-TPD), temperature-programmed reduction with H2 (H2-TPR), H2-chemisorption and transmission electron microscopy (TEM) were used. The acidic property was continuously increased until Si/(Si + Al) = 30 mol% in SiO2-Al2O3 mixed oxides used. The dispersion of Ni metal and surface area, acid characteristics of the supported Ni catalyst have a complex effect on the catalytic reaction activity. The low reduction temperature of nickel oxide and acidic properties were beneficial to the formation of acetonitrile. In terms of conversion of ethanol, Ni/SiO2-Al2O3 catalyst with a molar ratio of 10 mol% Si/(Si+Al) showed the highest activity and a volcanic curve based on it. The tendency of results were consistent in the metal dispersion and catalytic activity.

• Journal of the Korean Chemical Society
• /
• v.32 no.1
• /
• pp.22-29
• /
• 1988

The reaction of methanol-water mixture to $CO_2$ and $H_2$ on alkaline earth metal-copper-zinc oxide has been studied in the temperature range of 150 ${\sim}\;300^{\circ}C$. Generally the addition of the alkaline earth metal to Cu/ZnO resulted in an enhancement of selectivity for $CO_2$ formation and a reduction of catalytic activity. Measurable activities were found from 150$^{\circ}C$, 200$^{\circ}C$, and 250$^{\circ}C$ on Mg/Cu/ZnO, Ca/Cu/ZnO, and Ba/Cu/ZnO respectively. However, the highest selectivity for $CO_2$ formation was observed in Ba/Cu/ZnO catalyst at 250$^{\circ}C$. The effect of alkaline earth metal or ZnO on the reactivity was investigated using temperature programmed desorption of $CO_2$ or temperature programmed reduction with $H_2$ over catalysts respectively. It was found that $CO_2$ interacts more strongly in the sequence of MgO < CaO < BaO and ZnO decereases the reduction temperature of CuO. From the results, it was suggested that ZnO activates $H_2$ in the redox process of Cu component and alkaline earth metals adsorbs $CO_2$ in the catalytic process.

• Clean Technology
• /
• v.21 no.4
• /
• pp.248-256
• /
• 2015

MnO₂ was prepared by a hydrothermal process method in the range of 120-200 ℃ and 0.5-5 h, calcined at 300 ℃ after induction of precipitation using KMnO₄ and MnCl₂･4H₂O, and its catalytic activity was compared for CO oxidation. The catalysts were characterized using by X-ray diffraction, N₂-sorption, scanning electron microscopy, and temperature programmed reduction of H₂ or CO. The crystalline structure of pure α-MnO₂ or hybrid α/β-MnO₂ was controlled by the preparation conditions. The pure α-MnO₂ showed better catalytic activity and thermal stability than hybrid α/β-MnO₂. Especially, α-MnO₂ prepared at 150 ℃ for 1 h has the highest specific surface area 214 m² g^-1, reducibility and labile lattice oxygen species analyzed by H₂, CO-TPR, respectively. It also showed the best CO oxidation activity in both conditions of temperature programmed and isothermal reaction. The results came from the physicochemical properties of catalysts like the crystalline structure, specific surface area, reducibility and lattice oxygen species, and which are correlated with catalytic performance.