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C_(1)-HVOCs 제거를 위한 Ru-Sn/γ-Al_(2)O_(3) 촉매 제조 및 반응성 평가
김영주,황운연,구기갑,김용렬,박종수,윤왕래 한국화학공학회 2004 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.42 No.1
HVOCs 제거에 사용되는 백금-팔라듐계보다 저렴한 촉매 개발을 목적으로 다양한 루테늄계 촉매를 제도하여 C_(1)-HVOCs 분해 특성 평가 실험을 수행하였다. 그 결과 Ru[2]-Sn[2]/γ-Al_(2)O_(3) 촉매가 가장 우수한 성능을 보였다. 구조 증진제인 주석은 흡착 산소의 양을 증가시키고, 다양한 산소 이온 종의 생성에 기여함을 알 수 있었다. HVOCs 분해 반응에 첨가되는 산소 원자는 주로 루테늄과 주석에 흡착되며, CH_(3) 등 HVOCs는 지지체인 γ-Al_(2)O_(3)의 브뢴스테드 및 루이스 산점에 흡착됨을 알 수 있었다. 흡착된 HVOCs의 염소와 브뢴스테드 산점의 수소 화학 결합에 의한 HCl의 생성 반응이 HVOCs 분해의 주 반응 기구임을 알 수 있었다. Various ruthenium(Ru) based catalysts, which were less expensive than Pt-Pd based catalysts, were prepared and their activity with C_(1)-HVOCs(Halogenated Volatile Organic Compounds) was evaluated. Ru[2]-Sn[2]/γ-Al_(2)O_(3) was found to have the most desirable effect on the destruction of HVOCs. Tin taken as a structural promoter was found to increase the amount of oxygen adsorption and to generate various oxygen ions. Oxygen atoms were found to be mainly adsorbed on the surface of ruthenium and tin and HVOCs such as CH_(3)Cl to adsorbed on Bronsted and Lewis acid sites of γ-Al_(3)O_(3) supports. It was found that the formation of HCl by the reaction of chlorine in HVOCs with hydrogen atom on Bronsted acid site was the main reaction mechanism in the destruction of HVOCs.
Seon Min Park,Eun Young Kim,Yong Lai Park,Chan Heun Park 한국유방암학회 2022 Journal of Breast Disease Vol.10 No.1
Purpose: This study investigated the correlation between non-mass-like enhancement (NME) observed on preoperative breast magnetic resonance imaging (MRI) and the actual pathological size of breast cancer. We further examined the effect of NME on the positive resection margins during partial mastectomy. Methods: We retrospectively collected data from breast cancer patients who underwent surgery between January 2018 and September 2020. Patients were divided into two groups based on their MRI findings: NME and no-NME (mass-like lesion only) groups. The medical records, including MRI findings and clinicopathological information of patients, were collected retrospectively, and correlations with pathologic results were analyzed. Propensity score matching was applied to develop comparable cohorts of the NME group and no-NME group. Results: This study included a total of 317 patients, with 66 and 251 patients in the NME and no-NME groups, respectively. The mean pathologic size of invasive lesion was significantly smaller than the mean lesion size in the NME group (1.55±1.39 cm vs. 3.45±1.81 cm, p<0.001). The mean pathologic size of ductal carcinoma in situ (DCIS) lesions was larger than that in the NME group but without statistical significance (3.91±2.67 cm vs. 3.50±1.79 cm, p=0.326). In the NME group, NME estimated DCIS size to within 1 cm in 20 patients (30.3%) and overestimated invasive lesion size by more than 1 cm in 31 patients (46.9%). NME (vs. no-NME; odds ratio [OR], 2.967; 95% confidence interval [CI], 0.878-10.025) showed a tendency to predict positive resection margins, but this was not statistically significant (p=0.080). Conclusion: NME findings on MRI showed a similar extent of DCIS lesions. NME findings on preoperative MRI should be considered an important factor for measuring the extent of tumors, especially in DCIS patients.
Co가 첨가된 Cu-Ce/γ-Al₂O₃ 촉매상에서 개질수소가스에 포함된 CO의 선택적 산화반응 : (I) 촉매 반응 및 특성 평가
박종원,이영우,정진혁,이득기,박용기,윤왕래 한국화학공학회 2003 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.41 No.4
r-Al₂O₃에 담지된 Cu-Ce 기준촉매에 조촉매로서 Co가 소량 첨가된 촉매를 제조하여 모사개질 가스(1% CO, 1% O₂, 60% H₂ in N₂ balance)의 선택적 CO 산화반응을 수행하였다. 조촉매 함량, 과잉산소율 λ(=2[O₂]/[CO])을 변화시켜가면서 반응온도에 따른 활성 및 선택도를 조사하였다. Cu-Ce 촉매의 함량 및 비율에 따른 최적 활성을 실험 조사한 결과, Cu-Ce(4:16 wt%) 촉매가 넓은 온도 범위인 175-220℃사이에서 99% 이상의 높은 CO 산회 활성을 보였으며, 이때의 CO 선택도는 50-80%로 나타났다. 또한 Co를 조촉매로 첨가한 Cu-Ce-Co(4.0:15.8:0.2 wt%) 촉매는 150-220℃의 넓은 온도 범위에서 Cu-Ce 촉매에 비하여 더욱 우수한 반응 활성(>99% CO 전환율)과 선택도(50-94%)를 나타내었다. 승온환원(CO-/H₂-TPR) 및 승온산화(TPO) 실험 결과, Cu-Ce-Co(4.0:15.8:0.2 wt%) 촉매의 경우 타 촉매에 비해 촉매의 산화/환원 특성이 가장 우수하며, CO에 대한 높은 흡착능을 나타냄을 알 수 있었다. Cu-Ce/γ-Al₂O₃, catalysts promoted with Co were prepared and tested for selective oxidation of CO in a H-rich stream. The effects of promoter content. degree of excess oxygen (λ) were investigated for activity and CO selectivity while changing temperatures. Among the various Cu-Ce catalysts having different metal loadings and composition, Cu-Ce (4:16 wt%) catalyst showed the highest activity (>T_(99)) and selectivities (80-50%) under wide temperature range of 175-220℃. When the Cu-Ce catalyst was further modified with 0.2 wt% Co as a promoter, the highest activity (>T_(99)) and selectivities (94-50%) was obtained over the wide temperature windows of 150-220℃. From CO/H₂-TPR and TPO. it was found that by the addition of 0.2 wt% Co on Cu-Ce catalyst, oxidation-reduction activity of catalyst was improved, which resulted in the increase of catalytic activity and selectivity of CO oxidation in excess H₂ environment.
Co가 첨가된 Cu-Ce/γ-Al₂O₃촉매상에서 개질수소가스에 포함된 CO의 선택적 산화반응 : (II) CO₂와 H₂O 의 영향 (II) CO₂and H₂O Effect
박종원,이영우,정진혁,이득기,박용기,윤왕래 한국화학공학회 2003 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.41 No.5
선택적 CO 산화촉매인 Cu-Ce/r-Al₂O₃ 촉매 및 조촉매로서 Co가 소량(0.2 wt.%) 첨가된 Cu-Ce-Co/r-Al₂O₃ 촉매에 대하여 모사개질 가스(1 vol.% CO+1 vol.% O₂+60 vol.% H₂in N₂balance) 내에 존재하는 CO₂와 H₂O가 선택적 CO 산화반응에 미치는 영향을 조사하였다. 이들 CO₂와 H₂O가 개질가스 내에 존재할 경우 촉매를 피독시켜 저온 산화활성이 크게 감소되어 최고 55℃의 반응온도 증가를 가져왔다. 이러한 저온 산화활성 감소가 일어나는 원인이 개질가스 중에 포함되어 있는 CO₂와 H₂O가 각각 혹은 상호 경쟁적으로 산화 활성점에 강하게 흡착하기 때문이라는 것을 CO₂와 H₂O의 승온탈착실험(TPD)을 통하여 확인할 수 있었다. Cu-Ce-Co/r-Al₂O₃ 촉매의 경우는 Cu-Ce/r-Al₂O₃에 비하여 CO₂와 H₂O가 동시에 존재하는 경우에 대한 피독 저항성이 상대적으로 우수하여 이들 피독물이 존재할 경우에도 99.9%의 CO가 전환되는 T_(99) 온도창이 210-225℃ 범위에서 존재하였다. Cu-Ce/r-Al₂O₃ and Cu-Ce-Co/r-Al₂O₃ promoted with 0.2wt% Co were prepared and their catalytic performance was evaluated for the selective oxidation of CO in a H₂-rich condition(1 vol.% CO+1 vol.% Ox+60 vol.% He in N2 balance). When CO₂ and H₂O were present in the reformed gas feed, both Cu-Ce/r-Al₂O₃ and Cu-Ce-Co/r-Al₂O₃ showed decrease in oxidation activity of CO at low temperatures especially under 200℃. Compared with the Cu-Ce/r-Al₂O₃, however, the Cu-CeCo/r-Al₂O₃ showed higher resistance for the CO₂ and H₂O and also there existed a temperature window of T_(99.9) from 210 to 225℃ corresponding to the conversion of 99.9% CO. From CO₂/H₂O-TPD, it can be concluded that the main cause for the decrease in catalytic activity may be attributed to the blockage of the active sites by competitive adsorption of water vapor and CO₂ with the reactant at low reaction temperatures.
Lai, Shen,Byeon, Seongjae,Jang, Sung Kyu,Lee, Juho,Lee, Byoung Hun,Park, Jin-Hong,Kim, Yong-Hoon,Lee, Sungjoo The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.39
<P>While preparing uniform dielectric layers on two-dimensional (2D) materials is a key device architecture requirement to achieve next-generation 2D devices, conventional deposition or transfer approaches have been so far limited by their high cost, fabrication complexity, and especially poor dielectric/2D material interface quality. Here, we demonstrate that HfO2, a high-K dielectric, can be prepared on the top surface of 2D HfS2 through plasma oxidation, which results in a heterostructure composed of a 2D van der Waals semiconductor and its insulating native oxide. A highly uniform dielectric layer with a controlled thickness can be prepared; the possibility of unlimited layer-by-layer oxidation further differentiates our work from previous attempts on other 2D semiconducting materials, which exhibit self-limited oxidation up to only a few layers. High resolution transmission electron microscopy was used to show that the converted HfO2/HfS2 hybrid structure is of high quality with an atomically abrupt, impurity- and defect-free interface. Density functional theory calculations show that the unlimited layer-by-layer oxidation occurs because oxygen atoms can barrierlessly penetrate into the HfS2 surface and the extracted sulfur atoms are absorbed into the oxygen vacancy sites within HfO2 under O-rich conditions. A top-gated field-effect transistor fabricated with the converted HfO2/HfS2 hybrid structure was found to exhibit a low interface trap density <I>D</I>it of 6 × 10<SUP>11</SUP> cm<SUP>−2</SUP> eV<SUP>−1</SUP> between the HfS2 channel and the converted HfO2 dielectric, and a high on/off current ratio above 10<SUP>7</SUP>. Our approach provides a low cost, simple, and ultraclean manufacturing technique for integrating 2D material into device applications.</P>