Design, Synthesis, Biological Evaluation and Molecular Docking of New Imidazo[2,1-b]oxazole and Imidazo[2,1-b]thiazole Derivatives as Antiproliferative Agents

Usama Mohamed Magdi Ammar University of Science & Technology (UST) 2020 국내박사

본 연구에서는 새로운 imidazo[2,1-b]oxazole및imidazo[2,1-b]thiazole 유도체들이 다양한 종류의 암에 대한 항증식제로 설계되었습니다. 좋은 수율을 얻기 위해 각기 다른 정제 과정을 이용하여amide-based N-substituted 유도체인 27a-f, 28a-k 및 29a-f (23개 목적 화합물), open chain sulfonamide-based N-substituted 유도체인 30a-f, 31a-p, 32a-m, 33a-s및 34a-e (59개 목적 화합물), cyclic sulfonamide-based N-substituted 유도체 35a-d, 36a-d (8개 목적 화합물)을 최적의 합성 경로를 통해 합성하였습니다. 모든 목적 화합물들은 National Cancer Institute (NCI, USA)에 활성 평가를 의뢰하였습니다. 그 중, 1 그룹에 대하여 각기 다른 9개 암 종류에 대한 NCI-60 human cancer cell lines 패널을 통해 in vitro one-dose test를 진행하였습니다. 대다수의 화합물들이 우수한 활성과 광범위한 스펙트럼의 항암 작용을 보여주었습니다. 화합물 31o, 31p, 32d, 34e, 36d는 9개 암 아형에 대해 강력한 활성을 보였습니다. 목적 화합물들의 IC50 값을 구하기 위해 화합물 27c, 29a, 29b, 31p, 32d, 34e, 36b 및 36d는 NCI-60 human cancer cell lines에 대해 five-dose test를 진행하였습니다. 우수한 활성을 보여주는 화합물을 선정하기 위해 BRAF kinase (야생형, WTBRAF 및 돌연변이형, V600EBRAF)와 CRAF kinase에 대해 In vitro 효소 저해 활성이 수행되었습니다. 대다수의 화합물은 야생형 BRAF(WTBRAF) 및 CRAF kinase보다 돌연변이 BRAF kinase (V600EBRAF)에 대해 좋은 저해 활성을 보여주었습니다. 화합물 34c, 34e, 36a, 36b는 single-digit nanomolar와sub-nanomolar 범위의 IC50 값을 나타내었습니다. 화합물 36b는A375 흑색종 이종이식을 한 수컷 생쥐의in vitro antiproliferative activity에 선정되었습니다. 연구를 통해 imidazooxazole 및 imidazothiazole 이 우수한 항암제를 개발하는 데에 유망한 scaffold라는 것을 알 수 있었습니다. In silico 분자 도킹 실험은 화합물의pharmacophoric 구조와 타깃 효소의 활성 자리(V600EBRAF) 간의 결합 모드를 통해 우수한 활성을 나타낼 화합물을 알아보기 위해서 진행되었습니다. 화합물30d, 33f, 33r 및 36b은 V600EBRAF binding 활성 포켓에서 5~6개의 뚜렷한 상호 작용 으로인하여 강력한 binding score들을 보여주었습니다. 본 연구를 통해 imidazo[2,1-b]oxazole및imidazo[2,1-b]thiazole 유도체는 후속 물질 분자 구조 최적화를 위한 주요한 핵심 구조라는 것을 알 수 있었습니다. In the present investigation, new imidazo[2,1-b]oxazole and imidazo[2,1-b]thiazole derivatives have been designed as potential antiproliferative agents against different types of cancer. The amide-based N-substituted derivatives 27a-f, 28a-k and 29a-f (23 target compounds), open chain sulfonamide-based N-substituted derivatives 30a-f, 31a-p, 32a-m, 33a-s and 34a-e (59 target compounds) and cyclic sulfonamide-based N-substituted derivatives 35a-d and 36a-d (8 target compounds) were synthesized in optimized synthetic pathway in order to give good yields in pure forms using different purification protocols. The structures of all target compounds were submitted to the National Cancer Institute (NCI), Bethesda, Maryland, USA, and a group of compounds was selected for in vitro anticancer one-dose-testing over a panel of NCI-60 human cancer cell lines of 9 different cancer types. Different compounds showed high potencies and broad spectrum anticancer activities. Compounds 31o, 31p, 32d, 34e and 36d were highly active against the nine cancer subtypes. Compounds 27c, 29a, 29b, 31p, 32d, 34e, 36b and 36d were selected for 5 dose testing against the NCI-60 human cancer cell lines in order to investigate the IC50 values of the target candidates. The in vitro enzyme inhibitory activity was investigated for the most active compounds against BRAF kinase enzyme (wild type, WTBRAF; and mutated type, V600EBRAF) and CRAF kinase enzyme. Most of the tested compounds exhibitied higher inhibitory activities against mutated BRAF kinase enzyme than wild type BRAF and CRAF kinase enzymes. Compounds 34c, 34e, 36a and 36b showed single-digit nanomolar and subnanomolar IC50 values. Compound 36b was selected for in vivo antiproliferative activity against A375 melanoma xenograft in male Hsd:Athymic Nude-Foxn1nu (Harlan co. (USA)) mice. The present study revealed that both imidazooxazole and imidazothiazole are promising scaffolds for developing potent anticancer agents. In silico molecular docking study was investigated for the most active compounds in order to investigate the possible binding modes between the pharmacophoric groups of the tested compounds and the binding groups of the target enzyme active site (V600EBRAF). Compounds 30d, 33f, 33r and 36b showed greatest binding scores with 5 to 6 visible interactions in the V600EBRAF binding active site pocket. The results revealed that imidazo[2,1-b]oxazole and imidazo[2,1-b]thiazole derivatives are considered key scaffolds for further molecular and structural optimization.

Controllability of Non-thermal Effect in Low Current Arc Plasma and Its Applications in Fuel Conversion : 저전류 아크 플라즈마에서의 저온 플라즈마 효과 제어 가능성 및 이를 이용한 연료 전환 공정

DINH DUY KHOE University of Science and Technology (UST) 2019 국내박사

Computational modeling and design for the development of environment-friendly power systems: 1.5 MW coal-natural gas co-firing boiler, 250 kg/day hydrogen production system, and 5 kW-class solid oxide fuel cell power system

Iman rahimipetroudi University of Science and Technology (UST) 2022 국내박사

Climate change around the world has a profound impact on the global environment and the activities of life and has become a major global problem. Fossil fuels, in particular coal, is the most widely used fuel, especially in the field of power generation, and considered to be the main contributor to climate change and air pollution due to its high-intensity carbon levels. On the other hand, because worldwide fossil-fuel resources are significantly diminishing, however, energy consumption around the world is intensifying. Researchers agree that hydrogen and fuel cell technologies are contributing significantly to the transition to a low-carbon society, given their performance and flexibility in comparison with fossil fuel combustion technologies. Therefore, due to growing concern over the environmental impacts of coal-fired power facilities in continuous operation, an effective transition to more efficient units is required. Thus having good knowledge of the designs and configurations of the burners in boilers will be helpful to realize further improvements in the combustion characteristics and to comply with NOx emission standards. Besides, with the increase in the number of hydrogen vehicles worldwide, localized hydrogen refueling stations (HRS) are required, and empirical and technological improvements are therefore essential to overcome technological challenges related to durability, reliability, convenience, and supply network efficiency. In addition, before full-scale commercialization of SOFC power system, system-level design and operation glitches must be resolved. Accordingly, the main objective of this dissertation are computational modeling and design for the development of environment-friendly power systems in response to energy demands and low emissions for a sustainable future. This study composed of five chapters. In chapter one, background and an overview of power systems conditions that impact the global environment are given. The second chapter of the dissertation is focused on developing and designing an effective state-of-the-art dual-fuel pulverized coal (PC)-natural gas (NG) burner for use in dual-fuel fired power plant boiler utilities. The novelty of these study results, relate to burner modifications that are cost-effective, do not require large and complex additional structures, and incorporate a variety of technologies including fuel-air staging, flow swirling, preheating, and co-firing to increase performance and minimize emissions. The work reported in this chapter includes experimental and numerical modeling to study the effect of different operating conditions, excess air ratio, fuel staging, and NG blending. An optimal experimental design using a response surface methodology was also adopted to examine the significance of the operating parameters. Analysis of variance indicates that the regression equation can correctly represent the responses (p-value < 0.0001). It is also indicated that the excess air ratio and percentage of preheated PC have significant effects on NOx emissions (p < 0.005). The optimal conditions were determined to include an excess air ratio of 1.2 and 50 % PC injection into the preheating stream. Meeting these conditions, the predicted average NOx emission was 430±3.1 ppm and the average measured NOx emission 436±11.2 ppm, with 6% O2. Moreover, further reduction of NOx emission by up to 50% highlights the beneficial approach of NG co-firing. This design allows intensifying of recirculation and a mixture of fuels and oxidizers appropriate for improving the combustion characteristics significantly. The third chapter provides a comprehensive study of the effect of a developed co-firing burner and its front-wall, opposed-wall, and tangential firing arrangements on the performance improvement and emissions reduction of coal-natural gas combustion in a boiler. Understanding the combustion characteristics inside a boiler is essential to increase the efficiency and reduce environmental-related concerns. The novelty of this work is associated with a detailed analysis of the effectiveness of a developed co-firing coal-natural gas burner and the arrangements of the burners in the boiler for efficient combustion. Comparisons were made between the three main types of firing; front-wall, the opposite-wall, and the tangential firing types. The characteristics of the flow, the coal particle motion, the temperature distribution, the concentrations of species, and NOx emission levels are examined. The results showed that each burner in the front-wall-fired type creates independent long flame zones. In an opposite-wall fired type, the flames of burners impinge upon the center of the furnace to create turbulence. Results show that front-wall and opposite-wall firing configurations exhibit hot peak zones and temperature imbalances near the furnace sidewall. This emphasizes the need for heavily swirling vanes in the main burner to shorten the flame length and mix the fuel and oxidant well for efficient combustion. The state-of-the-art tangentially fired configuration produced a fireball, ensuring thorough mixing in the furnace and allowing for the complete combustion and uniform distribution of the temperature such that NOx reduction occurs preferentially. Additionally, these results confirm the advantage of combusting coal with natural gas in the main burner, as doing so reduces NOx emissions up to 19%. The technological options identified offer potential for interested manufacturers, researchers, and others in related industries to improve the performance and reduce the emissions of industrial dual-fuel-fired combustion utilities. The fourth chapter focuses on developing and undertaking a comprehensive CFD analysis of an effective state-of-the-art 250 kg/day hydrogen generation unit for an on-site hydrogen refueling station (HRS), an essential part of the infrastructure required for fuel cell vehicles and various aspects of hydrogen mobility. This design consists of twelve reforming tubes and one newly designed metal fiber burner to ensure superior emission standards and performance. Experimental and computational modeling steps are conducted to investigate the effects of various operating conditions, the excess air ratio (EAR) at the burner, the gas hourly space velocity (GHSV), the process gas inlet temperature, and the operating pressure on the hydrogen production rate and thermal efficiency. The results indicate that the performance of the steam methane reforming reactor increased significantly by improving the combustion characteristics and preventing local peak temperatures along the reforming tube. It is shown that EAR should be chosen appropriately to maximize the hydrogen production rate and lifetime operation of the reformer tube. It is found that high inlet process gas temperatures and low operating pressure are beneficial, but these parameters have to be chosen carefully to ensure proper efficiency. Also, a high GHSV shortens the residence time and provides unfavorable heat transfer in the bed, leading to decreased conversion efficiency. Thus, a moderate GHSV should be used. It is shown that heat transfer is an essential factor for obtaining increased hydrogen production. This study addresses the pressing need for the HRS to adopt such a compact system, whose processes can ensure greater hydrogen production rates as well as better durability, reliability, and convenience. The fifth chapter deals with designing, analyzing, and optimizing for the development of a 5 kW-class solid oxide fuel cell (SOFC) power system using anode-off gas recycling. This system is evaluated through modeling and simulation of stacks, including the balance-of-plant equipment using Aspen Plus. A portion of the anode off-gases from the fuel cell stack is recycled in the proposed system to achieve higher efficiency. The remainder is reacted with the depleted oxidant in the afterburner. The thermal energy from the combustor is utilized in the steam generator, reformer, and heat exchangers to balance the heat requirements of the SOFC system. The model performs heat and mass balances and considers ohmic, activation, and concentration losses for the voltage calculation. In addition, sensitivity analyses of major operating parameters, such as anode off-gas recycling ratio (AOGRRatio), fuel utilization factor (Ufuel,i), operating temperature (Top), current density (j), and steam to carbon ratio (S/C) on the system performance, are investigated. It is found that anode off-gas recycling provides an alternative approach to eliminate the need for an external water supply during operation of the SOFC system and increase the electrical efficiency while still maintaining the fuel utilization rate of the stack at a permissible level. Key words: Computational modeling, Design, Environment-friendly, Power generation system, Coal-natural gas co-firing boiler, Hydrogen production system, Solid oxide fuel cell system, Emission reduction, Performance improvement

Degradation Analysis and Lifetime Prediction Modeling of Anode-Supported Solid Oxide Fuel Cell

MUHAMMAD ZUBAIR KHAN University of Science and Technology (UST) Korea, 2018 국내박사

Analyzing the Dynamics of Social Behaviors: Micro-simulation and Agent-Based Modeling Approaches

MAZHAR SAJJAD University of Science and Technology (UST) 2016 국내박사

Computer simulation is getting popularity in all fields of social sciences. The applications of these simulations in interdisciplinary fields like Sociology, Economics and Demography are intended to help us to understand the properties of complex social systems in a better way. Social simulation allows the study of the complexity inherent to these social phenomena. In the last few decades, statistical microsimulation modeling (MSM) and agent based modeling (ABM) has become one of the mainstream modeling techniques in many scientific fields. These modeling techniques aims to model the evolution of this complex social life from the bottom up, considering that individual behavior causing macro-level phenomena. Furthermore, these individual changes will also lead to an evolution of the whole population over time. This research study aims to study and understand the dynamics of family formation and childbirth processes of demographic behaviors through the development of a statistical and agent-based modeling approach in the context of Korea. It attempts to demonstrate the importance of individual based modeling and simulation tools within the scope of demographic planning, as well as in application of a variety of substantive research and planning regarding population dynamics. We know from various studies that socioeconomic status plays a major role in demographic decisions especially at the time of family formation and having childbirth. The thesis introduces two models of demographic applications using statistical microsimulation and agent-based modeling approaches. Analyzing these models we were able to identify some critical factors that have to be considered when studying socioeconomic status and their role for explaining observed demographic patterns. First, using microsimulation technique to analyze the family formation and childbirth transitions using socioeconomic status as the key force driving the marriage and childbirth processes. It demonstrates that aggregate behavior can endogenously emerge from the bottom up. Further, the model indicates the importance socio-economic factors: education and employment levels to take decisions about family formation and childbirth. Second, using a data-driven agent-based modeling technique analyzes the impact of socioeconomic factors on individual decisions about family formation and childbirth. In both transitions, the agents are heterogeneous in nature about age and socioeconomic factors: income and education. Further, our simulated results depict the patterns of the hazard of family formation and childbirth that observed at micro-level dynamics and explain how marriage and childbirth patterns changes overtime. The thesis work gives a strong insight to strengthen the extent of demographic analysis through statistical and data-driven agent-based modeling approaches.

Nanostructured Cathode Materials Based on Transition Metal Oxides for Rechargeable Lithium?Oxygen Batteries : 리튬 산소 이차전지용 전이금속기반 나노구조 양극 소재 연구

RIAZ AHMER Korea University of Science and Technology (UST) 2011 국내박사

There is a great deal of current interest in the development of rechargeable batteries with high energy storage capability due to an increasing demand for electric vehicles (EVs) with driving ranges comparable to those of gasoline-powered vehicles. Among various types of batteries under development, a Li–O2 battery delivers the highest theoretical energy density; thus, it is considered a promising energy storage technology for EV applications. Cathode (oxygen electrode) is the key component of Li–O2 battery as the major battery reactions, i.e., oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) occurs at its surface. Low round-trip efficiency, poor reversibility, and poor power capability are the major challenges faced by the cathodes of the Li–O2 battery. A cathode, which can overcome these challenges, is essential to success of the Li–O2 battery as a major energy storage technology of the future. The main purpose of this study is to develop such cathode materials (catalyst or framework) for the Li–O2 battery. Chapter 1 presents a brief introduction to the significance of Li–O2 batteries as a major energy storage technology for the future, its working principle, its different types and the challenges associated with this technology, which hinders its development. Chapter 2 describes a brief overview on the previous works performed so far; in the area of cathode material development for Li–O2 batteries. Chapter 3-5 presents my work in the field of development of cathode materials for the Li–O2 batteries. Chapter 3 deals with the urchin-like -MnO2 materials decorated with Au and Pd nanoparticles; which are developed for use as a cathode catalyst for rechargeable Li–O2 batteries with hybrid electrolytes. Au and Pd particles as large as 3 – 8 nm are uniformly dispersed on the vertically aligned nanorods of α–MnO2. The Au/α–MnO2 and Pd/α–MnO2 catalysts show excellent bi-functional activity for both oxygen reduction and evolution. A rechargeable Li–O2 battery with a hybrid electrolyte is constructed using the nanostructured composite catalysts. Charging and discharging experiments of the batteries indicate that the metal-decorated, urchin-like α–MnO2 can be used as an efficient bi-functional catalyst for rechargeable hybrid Li–O2 batteries. Chapter 4 deals with the carbon-free cobalt oxide cathodes for Li–O2 batteries; which are fabricated via an electrodeposition-conversion process. This synthesis process is flexible and different architectures of cobalt oxide is obtained by changing process parameters. The Co3O4-only cathodes show a remarkably reduced voltage gap (by ca. 550 mV compared to the carbon-only cathode) as well as excellent long-term cyclability. The excellent charging and cycling performance of the NN-Co3O4 cathode is due to its unique feature i.e., the absence of carbon having high reactivity with Li2O2. Chapter 5 deals with the carbon- and binder-free cathodes based on non-precious metal oxides; which are designed and fabricated for Li–O2 batteries. A novel structure of the oxide-only cathode having a high porosity and a large surface area is proposed that consists of numerous one-dimensional nanoneedle arrays decorated with thin nanoflakes. These oxide-only cathodes with the tailored architecture show high specific capacities and remarkably reduced charge potentials (in comparison with a carbon-only cathode) as well as excellent cyclability (250 cycles). It is demonstrated that various aspects of cathode design; like material selection, synthesis approach, synthesis parameters and nanostructure engineering greatly influence its electrochemical performance in Li–O2 batteries. A rationally designed cathode is essential for widespread commercialization of Li–O2 batteries. It is concluded that both chemical stability and physical properties like high surface area and porous structure of the cathode materials is very important to overcome the challenges faced by the cathodes of Li–O2 batteries.

Improved Post-Dryout Heat Transfer Models in Developing Region and Deformed Fuel under large break loss-of-coolant accident

NGUYENNGOCHUNG University of Science and Technology (UST) 2018 국내박사

In nuclear reactor design and safety analysis, post-dryout heat transfer has been received great impetus on the thermal hydraulic concerns. The post-dryout heat transfer, which is characterized by a two-phase flow mixture of superheated vapor and dispersed droplets, exists in most of the sequence events during a hypothetical large-break loss-of-coolant accident (LB LOCA). In the present study, an improved heat transfer correlation has been developed from an extensive experimental dataset obtained from vertical tubes for the rediction of local wall temperature in the post-dryout region. The improved correlation modified the ellknown film-boiling look-up table to be applied to the developing post-dryout region. The newly-developed correlation has been validated using various postdryout datasets covering not only LB LOCA but also other pressurized conditions for different purposes. The wall temperature prediction results showed very good agreement to the experimental data except for some cases of low mass flux and heat flux inlet conditions. At the early stage of reflood in an LB LOCA, the dispersed droplets would be mostly evaporated due to the verheating process, and the cooling water from the emergency core cooling systems has not levelled up yet. Hence, the prevailing wall-to-vapor convective heat transfer plays the most important role on the heat removal process. Under the harsh conditions in the reactor core, the fuel cladding could become ballooned due to the increase in surface temperature and the difference between the inner and outer pressures of the fuel rod. The deformation of the fuel cladding would restrict the subchannel flow area resulting in severe flow blockage. In this work, a series of steam cooling experiments has been conducted to study the effect of flow blockage on the local wall-to-vapor convective heat transfer with consideration of fuel relocation phenomenon. The experimental results have been used to derive a new flow blockage model which is able to complement the conventional flow blockage model implemented in the COBRA-TF code. The new flow blockage model has been generalized to universally apply to different flow blockage configurations. The upward flow inside a partially blocked core would be redistributed leading to remarkable changes in local flow pattern. The local mass flux in the intact subchannels are remarkably larger than those in the blocked subchannels due to the flow bypass effect. Additionally, the turbulence intensity and vorticity downstream of the blockage in the blocked subchannel are greatly enhanced owing to the flow separation effect. As a result, the local heat transfer in the vicinity of flow blockage may significantly altered. In order to investigate the local flow pattern in the partially blocked core, a new experimental facility has been designed by the author and constructed in Korea Atomic Energy Research Institute. The Particle Image Velocimetry measurement technique was adopted to capture the fluid motion inside a rod bundle containing partial flow blockage through a transparent test housing. The pressure drop caused by different flow blockage configurations as well as the information of local subchannel velocity have been recorded and analyzed. A new flow blockage pressure loss factor has been derived using Buckingham Pi theorem and regression technique, expressed as a function of flow blockage ratio, maximum flow blockage length, and divergence angle. The newly-developed flow blockage pressure loss factor has been used to improve the flow diversion model in the literature*. 원자로설계 및 안전해석에서 포스트드라이아웃 열전달은 열수력 분야에서 많은 연구가 진행되었다. 포스트드라이아웃 열전달은 대형냉각재상실사고 과정 가운데 과열 증기와 분산액적의 이상유동으로 특징지을 수 있다. 본 연구에서는 포스트드라이아웃 영역에서 국소벽면온도를 예측하기 위한 수직관 실험을 수행하여 기존 연구에 확장된 실험데이터를 제공하고, 개선된 열전달상관식을 제시하였다. 개선된 상관식은 잘 알려진 막비등 룩업 테이블(Look-up table)을 수정하여 개발되었으며, 포스트드라이아웃의 발달영역에 적용 가능하다. 새로 개발된 상관식은 대형냉각재상실사고뿐 아니라 다양한 가압조건의 포스트드라이아웃 실험데이터들을 기반으로 검증되었다. 그 결과 낮은 유량 및 열속조건을 제외하고는 벽면온도를 잘 예측함을 확인하였다. 대형냉각재상실사고의 재관수 초기에 분산액적은 과열증기로 인해 대부분 기화되며, 비상노심냉각계통을 통해 제공된 냉 수의 수위는 충분히 상승하지 않는다. 따라서 이 시기에는 주로 벽면-증기 대류열전달로 인해 잔열이 제거된다. 잔열이 잘 제거되지 못하는 가혹한 조건에서는, 피복재의 표면온도 상승 및 봉내외 압력차이로 인해 피복재가 팽창할 수 있다. 피복재 변형은 부수로 유로 면적을 제한하여 유동을 부분적으로 막을 수 있다. 본 연구에서는 핵연료재배치에 따른 유동부분막힘이 국소 벽면-증기 대류열전달에 어떤 영향을 미치는지 다양한 실험을 통해 확인하였다. 실험 결과를 기반으로 새로운 모델을 개발하였으며, 이는 COBRA-TF 코드에 삽입된 기존의 유동부분막힘 모델을 보완하는데 활용될 것으로 기대된다. 새로운 유동부분막힘 열전달 모델은 다양한 부분막힘 현상에 활용될 수 있도록 일반화되었다. 부분막힘 조건에서 상향유동은 국소유동패턴이 급격하게 바뀌며 재배치된다. 건전한 부수로의 유속은 우회유동 효과로 인해 부분적으로 막힌 부수로의 유속보다 상당히 빠르다. 더욱이 유동막힘 하류에서 난류강도 및 소용돌이도(vorticity)가 유동분리효과에 의해 급격하게 증가한다. 그 결과, 유동막힘 주변의 국소열전달이 크게 바뀐다. 유동부분막힘 조건에서의 국소유동패턴을 확인하기 위해, 새로운 실험장치를 설계 및 제작하였다. 이 때 PIV (Particle Image Velocimetry) 측정기법을 이용하여 봉다발 내 유동을 투명한 시험장치를 통해 관측하였다. 또한 다양한 유동막힘 조건 및 유속 조건하에서 압력강하 값도 측정하였다. 새로운 유동막힘 압력강하인자를 Buckingham Pi 정리와 회귀 기법 (Regression Technique)을 이용하여 유도하였다. 이는 유동막힘정도, 최대 유동막힘 길이, 확산각도의 함수로 제시되었다. 새로운 유동막힘 압력강하 인자는 유동분산모델을 개선하는데 활용될 수 있다.

Enhancement of low temperature NH3-SCR activity of Sb-V/CeO2-TiO2 catalyst by synthesis modification

DANH THI HUONG University of Science and Technology (UST)- KIST c 2016 국내석사

In this work, the synthesis of Sb-V/CeO2-TiO2 catalyst was modified by controlling pH under the addition of monoethanolamine solution. All the catalysts were systematically investigated for NOx reduction with NH3 at different reaction conditions and then characterized by XRD, BET-surface area, X-photoelectron spectroscopy, NO-TPD, NH3-TPD, H2-TPR and mass spectroscopy. Synthesis modification of Sb-V/CeO2-TiO2 catalyst exhibited noticeably higher NOx reduction activity at low temperatures (< 250 oC). The H2-TPR revealed the enhancement of reducible species for the modified catalyst at basic pH, followed by neutral pH and acidic pH, respectively. The catalyst synthesized at basic pH is persistent for NOx reduction with time that was confirmed by the time on stream durability test under SO2 and water. The Ce 3d XPS spectra of spent catalyst synthesized at basic pH was indicated more reduction of Ce4+ to Ce3+ at the presence of SO2. Mass spectroscopy results also reveal the presence of ammonium sulfalte or bisulfate salts which deactivate the catalyst.

Catalytic fixation of CO2 to urea derivatives and 2,5- furandicarboxylic acid

TRUONG CONG CHIEN University of Science and Technology- UST 2020 국내박사

Today, the climate change in the world is attributed to the emission of greenhouse gas. Among this, carbon dioxide (CO2) is considered as the most ubiquitous one in term of output due to the deforestation, fuel combustion and other anthropogenic activities. Therefore, mitigating the current CO2 emission has become one of the most top-priority targets for the worldwide community. Among a multiple of solutions to curtail the CO2 emission, the chemical fixation of CO2 into fuels and chemicals is regarded as the most promising routes to utilize CO2 with respect to green and sustainable point of view.Urea derivatives are an important class of organic molecule found in many industrial applications. Conventionally, the production of urea derivatives involves the employment of phosgene or isocyanates, which are extremely toxic and harmful to environment and human beings. Therefore, phosgene/isocyanatefree synthesis of urea derivatives via the exploitation of CO2 as a benign C1source would be more desirable in terms of green and sustainable chemistry.Although several advances in the carboxylation of CO2 with amines toward urea products have been made, these still suffer from some unavoidable disadvantages. To address these problems, we developed a novel catalyst defined as cesium salt of azo compound, which was found to be more active and stable than other benchmark catalysts for the carboxylation reaction. With the hexylamine and diamines as the model substrates, more than 92.5% yield of 1,3- dihexylurea and corresponding polyureas were achieved, respectively. In particular, the catalyst is thermally stable and can be recycled up to four times with no loss of activity. Currently, 2,5-furandicarboxylic acid (FDCA) is an important monomer for the manufacture of bio-based polymers which are regarded as an alternative polymeric material to conventional polymers derived from fossil fuel source. Today, most of the synthetic FDCA are obtained from the oxidation of HMF, however, the processes require the employment of precious metal-based catalysts. In some cases, the usage of bases and high pressure of oxidants (air and O2) are unavoidable. Recently, some trials on the carboxylation of 2-furoate metal salts to FDCA using CO2 have been attempted. Herein, we reported a novel pathway to prepare 2,5-FDCA in a desirable yield via the utilization of ionic liquid (1,2-dimethylimidazole-Furoic acid) under the presence of Cs2CO3.

A study on CO2 reduction pathways and performance evaluation of thermal power plant

ZELALEM TUMSA TEFERA University of Science and Technology (UST),Korea I 2018 국내박사

The majority of greenhouse gas emissions consist of energy related carbon dioxide (CO2) emissions. Meeting deep cuts in global CO2 emission is helpful to reduce the global warming and limit an average temperature rise below 2oC. There are some proposed ways to reduce the emission of CO2, such as partial replacement of fossil fuel with renewable fuels for power generation and carbon capture and storage (CCS). In this thesis, performance evaluation of thermal power plant during partial replacement of coal with different biomasses based on equal thermal share input was conducted. The study and comparison was carried out based on 500 MWe large scale coal power plants. This section investigates the effect of various biomass and coal co-combustion on the overall performance of power plant and reduction of CO2 emissions. A process simulation tool (gCCS) was used to simulate and analyse the whole system. The other option to reduce the supply side CO2 emission is carbon capture and storage. Oxy-combustion is an efficient approach to realize carbon capture and storage. In this thesis, an emerging approach for CO2 capture and storage, pressurized oxy-combustion, will be evaluated and discussed in detail. Further, the development of an advanced ultra-supercritical (AUSC) steam cycle under oxy-fuel environment was evaluated in order to reduce greenhouse gases and pollutant emission by increasing the power plant cycle efficiency and the rate of CO2 capture. Higher cycle efficiency requires less fuel consumption per unit output of the plant and resulted in emission reduction. The effects of coal characteristics (fuel switching) on the overall efficiency of coal power plant were also evaluated. In addition, the effects of pressurization on the efficiency of the power plant were also discussed in detail in comparison with the reference (atmospheric) combustion conditions. Heat integration was implemented in order to recover and integrate heat from the pressurized flue gas using flue gas condenser. The net plant efficiency increased by 6.02%, 3%, and 2.61% for an increase in pressure from atmospheric pressure up to 30 bars, in case of lignite, subbituminous, and bituminous coals, respectively. Around 90% of CO2 is also captured for storage. Moreover, the removals of other emission gases (SOx and NOx) are required to ensure effective transportation and storage of CO2 rich flue gas. In here, the simultaneous removal of SOx and NOx from the pressurized flue gas using a direct contact condenser was investigated during CO2 capture and purification. It focuses on parametric study of SOx and NOx removal during pressurized flue gas condensation using Aspen plus direct contact column model. The improved (modified) chemistry involved in this model reflects the-state-of-the-art SO¬x and NOx reaction mechanisms with particular emphasis on liquid phase chemistry. Liquid phase nitrous-sulfurous interactions were implemented in the process modelling of NOx and SOx removal unlike previous studies. The effects of pressure, water flow rate and recycle ratio on the removal efficiencies of SO¬x and NOx were also evaluated. The removal efficiency of NOx increased from 70% to 97% when the pressure increased from 15 bar to 30 bar whereas, 99.9% of SO2 was absorbed from the flue gas at 15 bar. The developed model was validated against different literature data depending on various parameters. Relatively, good agreement has been obtained between our model and design conditions in addition to related researches that will strength the proposed model. 에너지 산업에서 배출되는 온실가스 중 이산화탄소(CO2)는 가장 큰 비중을 차지한다. 화력발전내의 CO2 저감을 위해 화석 연료의 일부분을 바이오매스와 같은 신재생 에너지로 대체하고 배출되는 이산화탄소를 포집 및 저장(CCS)하는 방법이 주로 활용되고 있다. 본 연구에서는 500MWe 규모의 석탄 화력발전소를 대상으로 다양한 바이오매스와 석탄의 혼소 조건에 대한 열 평형 기반의 공정 성능 평가를 수행했다. 또한, 바이오매스와 석탄의 혼소에 따른 발전단의 성능과 CO2 배출 저감에 미치는 영향에 대해 조사하였다. CO2 배출량을 줄이기 위한 다른 방안으로 CCS 기술에 대해 평가를 진행했다. 순산소 연소는 CCS를 실현하기 위해 가장 효율적인 방법이다. 본 연구에서는 CCS를 효과적으로 활용하는 신 연소 기술인 가압 순산소 연소에 대한 새로운 접근법을 통해 세부적으로 평가 및 방안을 제시했다. 가압순산 소 조건에서 발전 사이클의 효율 향상과 온실 가스 및 오염물질 배출 저감을 위해 ASUC(Advanced Ultra-Supercritical) 스팀사이클을 개발하고 공정에 적용하여 평가를 진행하였다. 고효율의 사이클은 연료의 투입 소비량을 줄이고 배기가스의 배출량을 감소시킨다. 추가적으로 석탄 특성(연료 다변화)에 따른 석탄 발전소의 효율에 대한 영향성을 평가하였다. 또한, 상압 조건과 가압 조건(보일러 내 압력의 변화)에 따른 발전단 효율에 대해 비교 분석하였다. FGC(Flue gas Condenser) 시스템을 통해 배가스의 잠열 회수를 극대화하여 공정효율이 증가하였다. 상압에서 30bar로 압력을 증가시킬 때 공정 효율은 각각의 탄종에 따라 갈탄 6.02%, 아역청탄 3.0%와 역청탄 2.61%로 증가하였다. 모든 탄종에서 CO2 배출 저감 효과는 약 90%로 나타났다. CPU에서 효과적인 CCS를 달성하기 위해서는 NOx 와 SOx 같은 다른 배가스의 제거가 필수적이다. 따라서, 가압순산소 조건에서는 후단 설비(FGC)를 통해 배가스내 NOx와 SOx를 동시에 제거하는 방법을 조사하였다. 해석에 사용된 프로그램은 Aspen+이며 직접 접촉식 컬럼으로 설계하여 NOx, SOx와 유체의 화학 반응 메커니즘 및 pH의 변화를 고려하여 제거 효율을 분석하였다. 유체의 nitrous-sulfurous 작용은 선행 연구의 NOx, SOx 제거 공정 모델링을 사용하여 해석을 진행하였다. 또한, NOx, SOx의 제거 효율에 대한 압력, 물 유속 및 재순환 비에 따른 영향을 비교 분석 하였다. 그 결과, NOx의 제거 효율은 압력이 15-30 bar로 증가할 때 70-97%로 증가하였으며 SO2는 15bar에서 약 99%로 물(유체)에 포집되어 FGC 시스템을 통해 대부분 제거되는 결과가 나타났다. 개발된 모델은 다양한 매개 변수에 따라 선행 연구들과 비교 분석 및 검증을 진행하였으며 모델의 신뢰성을 확보하였다.