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티타늄 함유 제올라이트 베타 촉매의 합성, 물성조사 및 반응특성 연구
윤보상,안화승 한국화학공학회 2002 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.40 No.1
티타늄 함유 제올라이트 베타(Ti-beta) 촉매를 5가지 수열합성 방법과 알콕사이드 또는 메탈로센을 티타늄 원으로 이용한 2가지 후처리 grafting방법으로 제조하여 제조 방법에 따른 물성 차이를 연구하였다. 모든 촉매의 UV-Vis 스펙트럼에는 제올라이트 격자구조 내에 고립되어 존재하는 티타늄에 해당하는 220㎚의 흡수밴드가 관찰되었으며, grafting 시킨 경우 나노크기의 TiO_2 cluster에 기인하는 240-320㎚의 흡수 밴드가 함께 관찰되었다. 결정 입자는 dry-gel 방법과 seed를 사용한 경우 50㎚이하, 액상 전구체의 수열합성에 의한 기존 방법이나 TiO_2/SiO_2 xcrogel 전구체를 사용한 경우는 200㎚, 불산 분위기 합성에서는 2-5㎛의 평균 입자 크기를 나타내었으며, 분자체 결정에 대한 수율은 Ti-beta(F^-)>Ti-veta(seed)>Ti-Al-beta(xerogel)>Ti-Al-beta(dry-gel)>Ti-Al-beta(conventional)의 순서로 조사되었다. Cyclohexene의 epoxidation 반응은 Ti-Al-beta(conventional), Ti-beta(seed)>Ti-Al-beta(xerogel), Ti-Al-beta(dry-gel)>Ti-beta(F^-)의 순서로 전화율이 나타났으며, epoxide에 대한 선택성은 Ti-Al-beta(xerogel)<Ti-Al-beta(conventional)<Ti-Al-beta(dry-gel)<Ti-beta(seed)<Ti-beta(F^-)의 순서로 증가하였다. Epoxide의 선택성은 알루미늄 함량과 표면의 소수성 정도에 영향을 받음을 확인할 수 있었다. Cyclohexene의 전화율과 epoxide의 선택성은 모든 촉매에서 CH_3CN을 용매로 사용할 때가 CH_3OH보다 높게 나타났다. A critical evaluation of synthesis recipes reported for the large pore zeolite Ti-beta was conducted after a series of titanium containing zeolite beta were prepared by five different hydrothermal synthesis and in two post-synthetic grafting methods using alkoxide or metallocene as a titanium precursor. All Ti-beta prepared by different synthesis routes showed a narrow charge transfer band centered at ca. 220㎚ in UV-Vis spectra, typical of Ti sites isolated in zeolite framework. For those prepared by grafting, the absorption band at 240-320㎚ attributed to nano-sized TiQ clusters were also detected. Particle size of Ti-Al-beta(dry-gel) and Ti-beta(seed) were below 20㎚; Ti-Al-beta(conventional) and Ti-Al-beta(xerogel) below 200㎚; and Ti-beta(F^-) ca. 2-5㎛. Yield of zeolite crystals decreased in the order Ti-beta(F^-)>Ti-veta(seed)>Ti-Al-beta(xerogel)>Ti-Al-beta(dry-gel)>Ti-Al-beta(conventional). For cyclohexene epoxidation, conversions varied in the order Ti-Al-beta(conventional), Ti-beta(seed)>Ti-Al-beta(xerogel), Ti-Al-beta(dry-gel)>Ti-beta(F^-)> with epoxide selectivity in the order Ti-Al-beta(xerogel)<Ti-Al-beta(conventional)<Ti-Al-beta(dry-gel)<Ti-beta(seed)<Ti-beta(F^-). The epoxide selectivity was affected by aluminum content and hydrophobicity of the material. Cyclohexene conversions and epoxide selectivities were higher in aprotic CH_3CN solvent than in CH_3OH.
인장력을 받는 CT형강 고력볼트 접합부의 감소계수 U값에 관한 연구
윤성호,김진숙,김원식,신영록,김보영,최문식 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.2(구조계)
The purpose of this experimental study is to investigate the validity of code equation and table to calculate the reduction coefficient for effective net area in the limit state design code of steel structure and offer the basic research data for the effective net area of tee shape members in tension. The experimental tests were performed by loading the specimens through the flange with high strength bolt. Length of connection, number of bolt and the eccentricity are the parameters in test. According to result, the failure loads in test is less than predicted loads and it well showed when the predicted loads are based on reduction coefficient of the table in code. The lateral buckling of stem occurred in the members with big eccentricity and it reduce the failure loads. Therefore, we thought that an additional tests and research on the factors of effective net area is required.
점토광물을 이용한 산소환원의 전기화학적 촉매성에 관한 연구
오성훈,황진연,심윤보,이효민,윤지해 한국광물학회 2005 광물과 암석 (J.Miner.Soc.Korea) Vol.18 No.1
몇 가지 점토광물과 메틸바이올로젠 또는 메틸렌블루를 함유시킨 점토수식전극을 이용하여 산소환원에 대한 전기화학적 촉매성을 검토하였다. 점토광물로는 Na-몬모릴로나이트, Ca-몬모릴로나이트, 카오리나이트를 사용하였다. 점토수식전극은 유리탄소전극 표면에 점토 현탁액을 입히고 메틸바이올로젠을 흡착시킨 것을 사용하였으며, 전기화학적 산소환원의 정도는 순환 전압전류(cyclic voltammetry)으로 측정하였다. 실험결과, 다른 점토시료에 비하여 Na-몬모릴로나이트가 메틸바이올로젠의 흡착효과가 가장 크게 나타났고, 메틸바이올로젠을 흡착시킨 점토수식전극이 산소환원에 대한 촉매성이 월등히 우수하였다. 즉 촉매산소환원 피크가 242.6 ㎷ 만큼 +방향으로 이동하였다. 메틸바이올로젠을 흡착시킨 점토수식전극이 메틸렌블루를 흡착시킨 점토수식전극보다 산소환원에 대한 촉매성이 더 높게 나타났다. Ca-몬모릴로나이트의 경우는 변화가 없었으나 Na-몬모릴로나이트의 구조는 메틸바이올로젠의 흡착으로 변화되었다. 메틸바이올로젠- Na-몬모릴로나이트 점토수식전극을 현탁액의 점토 농도가 약 0.87 g/10 mL이고, 메틸바이올로젠의 수용액의 농도가 대략 2.5 mM일 때 산소환원 촉매 효과가 가장 탁월하였다. 지지전해질의 pH에 따른 점토수식 전극의 산소 환원 촉매성은 중성의 pH 범위(6.3과 8.3)에서보다 산성인 pH 3.7과 알칼리성인 pH12.7에서 월등히 크게 나타났다. The electrocatalytic reduction of O₂ was investigated with methyl viologen and methylene blue incorporated clay-modified electrodes. Clay suspensions were prepared with Namontmorillonite, Ca-montmorillonite, and kaolinite. The methyl viologen-clay modified electrodes were made by coating clay suspensions adsorbing methyl viologen on a glassy carbon electrode. Cyclic voltammetry were performed in aqueous media to investigate the electrocatalytic property of the modified electrode in reducing O₂. A Na-montmorillonite modified electrode showed the greatest adsorption capacity for methyl viologen. The modified electrode made of Na-montmorillonite suspension of 0.87 g/l0 mL and a 2.5 mM of methyl viologen solution showed the most effective electrocatalytic property, where the catalytic reduction potential was shifted by 242.6 ㎷ toward the positive potential. The electrocatalytic ability was more significant in acidic (pH=3.7) and alkaline (pH=12.7) media than the neutral pH range (6.3~8.3). The methyl viologen-Na-montmorillonite modified electrode had the good reproducibility and maintain the electrocatalytic property over 20 times reuse.
김윤철,이정우,김보영,강정아,임대승,이민수,김정희,성보영,최성준,성인환,전은석 충남대학교 의과대학 지역사회의학연구소 2000 충남의대잡지 Vol.27 No.1
Coronary stent implacement is known as an effective treatment in the intimal dissection after percutaneous transluminal coronary angioplasty and the prevention of restenosis. However, In-stent restenosis still remains a major concern in clinical stenting. The stents were placed in 103 patients from July 1996 to March 1999 and performed follow-up coronary angiograms in 59(57.3%) patients. To identify the clinical, angiographic and procedurerelated variables 'which predict late restenosis within the stented artery, 59 patients(58.3±9.9, M:F= 41:18) were studied. The clinical characteristics of the patients were stable angina in 23(39.0%), unstable angina in 14(23.7%), acute myocardial infarction in 21(35.6%) and old myocardial infarction in 1(1.7%). Coronary stenting was performed in 1 patient(1.7%) for primary lesion, 50 patients(84.7%) for suboptimal results after PTCA, 6 patients(10.2%) for bail-out procedure, and 2 patients(3.4%) for restenotic lesions. All patients were treated with aspirin and ticlopidinc. The follow-up angiograms were obtained at 7±4 months. The overall in-stent restenosis rate was 27.1%. The coronary angiographic findings were 32 single vessel(54.2%), 19 two vessel(32.2%) and 8 three vessel disease(13.6%). The angiographic morphological characteristics were type A in 33(55.9%), type B in 14(23.7%), type C in 12(20. 3%) cases. Variables of 16 patients with restenosis were compared with those of 43 patients without restenosis. Previously known predictors for in-stent restenosis were multiple stenting, stenting for restenotic lesions, residual stenosis after stenting, stenting for total occlusion lesions, reference diameter, balloon to vessel ratio, acute gain and minimal luminal diameter after procedure, design and characteristics of stents, ostial lesion of aorta, high pressure method for stenting, lesion length, diabetes mellitus, size of artheroma, saphenous vein grafts, ulcerlating lesions and calcified lesions. In this study, Reference diameter before stenting(2.43±0.54mm vs. 2.88±0.65mm, p=0.016) and balloon-to-artery ratio(1.28±0.26 vs. 1.11±0.18, p=0.006) were predictors for in-stent restenosis. 1) The overall in-stent restenosis rate was 27.1%. 2) In the analysis of predictors for in-stent restenosis, there was no significant differences in clinical, angiographic factors between group with restenosis and without restenosis. But, Only reference diameter before stenting and balloon-toartery ratio were predictors of late in-stent restenosis. In conclusion, stenting is effective revascularisation method for selected patients with ischemic heart disease, and to minimize in-stent restenosis rate, stent implanting is achieved in a large vessel on the basis of an artery-to-stnet ration of 1:1, if possible.