• 공업화학
• /
• 제23권3호
• /
• pp.344-347
• /
• 2012

본 연구에서는 기존 MgO의 염기세기를 증가시켜 전이에스테르화 반응에 있어 보다 좋은 활성을 가지는 촉매를 만들고자 하였다. MgO를 실험실에서 제조한 후 지지체로 사용하였으며 염기세기를 증가시키기 위하여 KF를 함침법으로 담지하였다. BET, XRD, XRF, $CO_2$ TPO로 촉매의 특성분석을 하였고, 대두유과 메탄올을 사용하여 바이오디젤을 합성한 후 지방산메틸에스테르 함유량을 측정함으로써 촉매의 활성을 알아보았다. 결과적으로, KF를 30% 담지한 촉매가 활성이 가장 좋은 것으로 나타났다. 이는 전이에스테르화 반응에서 중간세기 염기도가 더 많이 관여하기 때문으로 보인다.

• Bulletin of the Korean Chemical Society
• /
• 제27권11호
• /
• pp.1844-1850
• /
• 2006

Two types of catalyst samples were prepared, one sulfated zirconia and the other silica doped sulfated zirconia. The acidity tests indicate that sulfated zirconia doped with silica has higher concentration and strength of acidic catalyst sites than undoped sulfated zirconia. The acidic surface sites have been characterized using FTIR, NMR, pyridine adsorption, TPD, XRD and nitrogen adsorption. Doping with silica increased the concentration of surface Lewis and Brfnsted acid sites and resulted in generation of proximate acid sites.The activity test indicates that doping sulfated zirconia with silica increases both the acidity and catalytic activity for liquid phase dehydration of methanol at 413-453 K. Methanol is sequentially dehydrated to dimethyl ether and ethylene over both catalysts. Significant amounts of propylene are also formed over the silica-doped catalyst, but not over the undoped catalyst.

• 폴리머
• /
• 제31권6호
• /
• pp.474-478
• /
• 2007

다이사이클로펜타다이에닐 비스페놀 시아네이트 에스터 올리고머와 열가소성 수지인 폴리페닐렌에테르(PFE)를 복합체화함으로써 유전손실이 적은 고분자 기판소재를 제작하였다. 올리고머와 촉매의 경화반응을 분석하여 최적 촉매첨가량을 Zn 0.02 phr로 선정하고 이를 복합체 제작에 적용하였다. 올리고머와 PPE의 함량비를 변화시키며 제작된 복합체의 동박 박리 강도, gel content 등을 측정하였으며, GHz 대역에서의 유전율과 유전손실을 평가하였다. PPE의 함량은 박리 강도 및 유전특성에 큰 영향을 주었으나, 촉매의 함량에 따라서는 유전특성에 큰 차이가 없었다. 실험결과 박리 강도가 1 kN/m 이상이고, 1 GHz에서 유전손실이 0.004로 낮은 고분자 복합체 라미네이트를 얻을 수 있었다.

• 대한화학회지
• /
• 제66권5호
• /
• pp.349-361
• /
• 2022

Because hydrotreating (HDT) of FCC gasoline is one of the important processes used to prepare such gasoline for blending, the development of a catalyst for this process is of great interest. Currently, the industrial HDT of FCC gasoline consists of two stages and the creation of a new catalyst for one-stage HDT will make this process more efficient. Recently, our group has developed the CoMo/Al₂O₃-ASA catalyst and studied the influence of Si/Al ratio on the target reactions of HDT process. Despite the high selectivity and activity, the catalyst with ASA is not applicable in industry because of its low strength. The present work moves forward to study the influence of the ASA content in the catalyst support and clarify the possibility to develop the catalyst that combines high activity and selectivity in HDT reactions with successful performance. Here we show that the CoMo catalyst with ASA/Al₂O₃ molar ratio 1/1 in the support is the best combination for FCC gasoline hydrotreatment due to exceptional properties of the catalyst composition.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2021년도 가을 학술논문 발표대회
• /
• pp.107-108
• /
• 2021

In the global trend of countries around the world announcing the declaration of carbon neutrality, the development of low-carbon cement in the cement industry can be seen as a very important issue that can determine the future development of the cement industry in the future. Therefore, this study evaluated the strength characteristics of limestone cement paste with limestone powder of CaCO3 and refinery desulfurization waste catalyst of high Al₂O₃ content, and using a Minitab mixture design to optimize a limestone cement content. As a resuls it was confirmed that limestone cement paste with 5-10% of limestone powder and 1.25-2.5% of the waste catalyst exhibits similar compressive strength to that of OPC.

• 한국재료학회지
• /
• 제20권12호
• /
• pp.681-685
• /
• 2010

The application of flip chip technology has been growing with the trend of miniaturization of electronic packages, especially in mobile electronics. Currently, several types of adhesive are used for flip chip bonding and these adhesives require some special properties; they must be solvent-free and fast curing and must ensure joint reliability against thermal fatigue and humidity. In this study, imidazole and its derivatives were added as curing catalysts to epoxy resin and their effects on the adhesive properties were investigated. Non-isothermal DSC analyses showed that the curing temperatures and the heat of reaction were dependent primarily on the type of catalyst. Isothermal dielectric analyses showed that the curing time was dependent on the amount of catalysts added as well as their type. The die shear strength increased with the increase of catalyst content while the Tg decreased. From this study, imidazole catalysts with low molecular weight are expected to be beneficial for snap curing and high adhesion strength for flip chip bonding applications.

• Restorative Dentistry and Endodontics
• /
• 제17권1호
• /
• pp.36-54
• /
• 1992

The purpose of this study was to compare the shear bond strengths to ground dentin surfaces of four dentinal bonding agents in 193 teeth. Various dentin surfaces treated with four dentin bonding agents were attached with two restorative composite resins. The effectiveness of the bonding were tested by the monitoring the shear bond strength. The shear bond strengths were measured after 2 hours and 24 hours after surface conditioning with four dentin bonding agents. Effects of EDTA, the additive illumination, and sealer treatments without primer on bond strength to dentin surfaces were assessed. In addition the effects of the thickness of specimens ranging from 0.65 mm to 1.95 mm and the ratio of catalyst and base paste on the bond strength of chemical cure composite resin were estimated. The shear bond strength was determined by testing specimens in the Instron universal testing machine (Model No. 1122) at a crosshead speed of 1.0 mm/min. Following condusions were drawn: 1. The highest mean shear bond strengths of chemical cure composite resin to dentin conditioning with dentin bonding agents aged 2 hours were obtained, and then that was decreased with time followed by EDTA treatment. 2. In light cure composite resin, the shear bond strength was increased following dentin conditioning with bonding agents with time, irradiation time and EDTA treatment except in SB group. 3. The thicker the composite resin specimen was, the less the shear bond strength in chemical cure composite resin was. 4. In light cure composite resin, there was a little change in shear bond strength following dentin conditioning with bonding agents. 5. In chemical cure composite resin, the shear bond strength was the highest in the ratio of 1/1 of catalyst and base part. 6. Without a dentin primer, shear bond strength to dentin conditioned only with UB sealer was the highest among four sealers in light cure composite resin.

• 폴리머
• /
• 제33권4호
• /
• pp.290-296
• /
• 2009

본 연구에서는 에폭시(DGEBA)/폴리아미드/MPD/2E4MZ-CN 반응성 블렌드의 경화 촉진제 함량에 따른 블렌드계의 형태학적 특징 및 기계적 물성에 대해 고찰하였다. 본 블렌드계의 경화거동은 DSC, 기계적 강도는 UTM, 형태학적 특징 변화는 SEM을사용하여 관찰하였다. 이미다졸(2E4MZ-CN) 경화촉진제의 함량을 $0{\sim}3\;phr$까지 조절 하였으며, 경화 반응 온도는 $170^{\circ}C$에서 30분간 유지하였다. 경화 촉진제의 함량이 증가함에 따라 최대 발열 온도가 미세하게 감소하는 경향을 보였으며, 이는 에폭시와의 상용성이 우수한 폴리아미드에 의해 경화 반응이 거의 방해받지 않았음을 보여 준다. 폴리아미드 함량이 20 phr인 조건에서 에폭시 블렌드계는 co-continuous한 분산상을 보이며, 이 조건에서 경화 촉진제의 첨가에 의해 더욱 균일한 co-continuous한 분산상이 나타났다. 상압 플라즈마 표면처리에 의해 표면장력이 증가되어 집착력이 향상되었으며, 경화 촉진제의 함량이 2 phr에서 가장 우수한 집착력을 보여 20% 이상의 집착력 향상 효과가 있었다. 이것은 경화 촉진제에 의한 블렌드계의 형태학적 조절을 고려하면 구조용 접착제에서 보다 향상된 집착력과 연신율을 동시에 기대할 수 있음을 보여 준다.

• Bulletin of the Korean Chemical Society
• /
• 제22권3호
• /
• pp.263-266
• /
• 2001

Isopropylation of phenol with 2-propanol has been carried out over Na-exchanged ZSM-5 zeolites to determine the effect of catalyst acidity on phenol conversion and product selectivity. The acid type and strength of the catalyst such as Lewis, weak and strong Bronsted acid sites are measured by pyridine adsorbed XPS and the catalytic properties are interpreted in terms of the acid properties. The active site and mechanism for the reaction are suggested based on evidence of study from the reactant adsorbed FT-IR.

• Carbon letters
• /
• 제14권1호
• /
• pp.58-61
• /
• 2013

In this work, the effect of catalysts on the mechanical properties of carbon fibers-reinforced epoxy matrix composites cured by cationic latent thermal catalysts, i.e., N-benzylpyrazinium hexafluoroantimonate (BPH) was studied. Differential scanning calorimetry was executed for thermal characterization of the epoxy matrix system. Mechanical interfacial properties of the composites were studied by interlaminar shear strength (ILSS), critical stress intensity factor ($K_{IC}$), and specific fracture energy ($G_{IC}$). As a result, the conversion of neat epoxy matrix cured by BPH was higher than that of one cured by diaminodiphenyl methane (DDM). The ILSS, $K_{IC}$, $G_{IC}$, and impact strength of the composites cured by BPH were also superior to those of the composites cured by DDM. This was probably the consequence of the effect of the substituted benzene group of BPH catalyst, resulting in an increase in the cross-link density and structural stability of the composites studied.