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Thien An Le,Quoc Cuong Do,김영민,김태완,채호정 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.6
The emerging H2 economy faces storage and transport challenges, and the use of ammonia (NH3) as a COx-free source of H2 via NH3 decomposition has recently attracted attention. Noble Ru-based catalysts are considered the best choice for highly efficient NH3 decomposition; however, their high cost and limited availability are disadvantages in large-scale applications. Otherwise, among non-noble metal-based catalysts, Ni-based catalysts are the most active, and Ni is considered a good alternative candidate material for NH3 decomposition because of its low cost. At present, some challenges remain in efforts to improve the efficiency of both Ru- and Ni-based systems. This review covers recent developments regarding these catalysts and can serve as a comprehensive work for evaluating effective long-term strategies.
CO and CO2 methanation over Ni catalysts supported on alumina with different crystalline phases
Le, Thien An,Kim, Tae Wook,Lee, Sae Ha,Park, Eun Duck Springer-Verlag 2017 Korean Journal of Chemical Engineering Vol.34 No.12
<P>The effect of alumina crystalline phases on CO and CO2 methanation was investigated using alumina-supported Ni catalysts. Various crystalline phases, such as alpha-Al2O3, theta-Al2O3, delta-Al2O3, eta-Al2O3, gamma-Al2O3, and kappa-Al2O3, were utilized to prepare alumina-supported Ni catalysts via wet impregnation. N-2 physisorption, H-2 chemisorption, temperature-programmed reduction with H-2, CO2 chemisorption, temperature-programmed desorption of CO2, and X-ray diffraction were employed to characterize the catalysts. The Ni/theta-Al2O3 catalyst showed the highest activity during both CO and CO2 methanation at low temperatures. CO methanation catalytic activity appeared to be related to the number of Ni surface-active sites, as determined by H-2-chemisorption. During CO2 methanation, Ni dispersion and the CO2 adsorption site were found to influence catalytic activity. Selective CO methanation in the presence of excess CO2 was performed over Ni/gamma-Al2O3 and Ni/delta-Al2O3; these substrates proved more active for CO methanation than for CO2 methanation.</P>
Current Perspectives on the Effects of Plant Growth-promoting Rhizobacteria
Thien Tu Huynh Le(후인르티엔투),Sang Eun Jun(전상은),Gyung-Tae Kim(김경태) 한국생명과학회 2019 생명과학회지 Vol.29 No.11
근권은 식물 뿌리와 토양 미생물이 서로의 신호를 주고 받으며 끊임없이 상호반응하는 역동적인 장소이다. 근권 주위에서 식물의 생장과 생산성에 유익한 토양 미생물을 식물생장촉진근권미생물(Plant Growth Promoting Rhizobacteria, PGPR)이라 칭하며, 이 PGPR은 식물 전 생장기간동안 생물학적 및 비생물학적 스트레스에 대한 저항성, 식물 호르몬 조절, 영양분의 흡수와 이용 등에 영향을 끼침으로써 식물의 생장과 발달, 면역, 생산력 등중요한 생명 과정에 관여한다. 그리고, PGPR은 식물 생장을 유도하는 2차 대사산물이나 휘발성 유기 화합물을 생산하고, 식물의 뿌리 역시 식물 유해한 인자 혹은 병원성 인자에 대항하여 자신을 보호하거나 토양 성질 개선을 위해, PGPR을 유인하고 정착시키기 위한 물질을 생산, 분비한다. 그러므로, 식물과 PGPR 사이의 상호작용은 필수적이면서도 상호의존적이다. 현재까지, PGPR에 대한 많은 연구는 직간접적 개념에 대하여 공통적 또는 다양한 조건들에서 여러 방식으로 PGPR의 기능을 밝히는 방향으로 전개되어 왔다. 본 총설에서는 세포분열과 팽창, 분화에 의한 식물의 생장과 발달의 촉진, 식물생장조절인자와 호르몬의 유도, 영양물질의 고정, 용해, 무기화를 촉진하기 위한 PGPR의 역할과 전략을 소개하였다. 또한 PGPR와 토양 미생물군의 효과에 대한 현재까지의 연구 정보를 요약하였다. The rhizosphere is the active zone where plant roots communicate with the soil microbiome, each responding to the other’s signals. The soil microbiome within the rhizosphere that is beneficial to plant growth and productivity is known as plant growth-promoting rhizobacteria (PGPR). PGPR take part in many pivotal plant processes, including plant growth, development, immunity, and productivity, by influencing acquisition and utilization of nutrient molecules, regulation of phytohormone biosynthesis, signaling, and response, and resistance to biotic- and abiotic-stresses. PGPR also produce secondary compounds and volatile organic compounds (VOCs) that elicit plant growth. Moreover, plant roots exude attractants that cause PGPR to aggregate in the rhizosphere zone for colonization, improving soil properties and protecting plants against pathogenic factors. The interactions between PGPR and plant roots in rhizosphere are essential and interdependent. Many studies have reported that PGPR function in multiple ways under the same or diverse conditions, directly and indirectly. This review focuses on the roles and strategies of PGPR in enhancing nutrient acquisition by nutrient fixation/solubilization/mineralization, inducing plant growth regulators/phytohormones, and promoting growth and development of root and shoot by affecting cell division, elongation, and differentiation. We also summarize the current knowledge of the effects of PGPR and the soil microbiota on plants.
Solar-driven biocatalytic C-hydroxylation through direct transfer of photoinduced electrons
Le, Thien-Kim,Park, Jong Hyun,Choi, Da Som,Lee, Ga-Young,Choi, Woo Sung,Jeong, Ki Jun,Park, Chan Beum,Yun, Chul-Ho The Royal Society of Chemistry 2019 GREEN CHEMISTRY Vol.21 No.3
<P>Despite the immense potential of P450s, the dependence on the nicotinamide cofactor (NADPH) and NADPH-P450 reductase (CPR) limits their employment in the chemical industry. Here, we present a visible light-driven platform for biocatalytic C-hydroxylation reactions using natural flavin molecules, especially flavin mononucleotide, as a photosensitizer. By employing visible light as a source of energy instead of the nicotinamide cofactor, the bacterial CYP102A1 heme domain was successfully applied for photobiocatalytic C-hydroxylation of 4-nitrophenol and lauric acid - in the absence of NADPH and CPR. We present a proof of concept that the photoactivation of flavins is productively coupled with the direct transfer of photoinduced electrons to the P450 heme iron, achieving photobiocatalytic C-hydroxylation reactions.</P>
Le, Thien An,Kim, Tae Wook,Lee, Sae Ha,Park, Eun Duck Elsevier 2018 CATALYSIS TODAY - Vol.303 No.-
<P><B>Abstract</B></P> <P>CO and CO<SUB>2</SUB> methanation over Na/Ni/SiO<SUB>2</SUB> and Na/Ni/CeO<SUB>2</SUB> catalysts with different Na contents (0, 0.1, and 1wt%) were studied. N<SUB>2</SUB> physisorption, H<SUB>2</SUB> chemisorption, temperature-programmed reduction with H<SUB>2</SUB>, CO<SUB>2</SUB> chemisorption, temperature-programmed desorption of CO<SUB>2</SUB>, temperature-programmed oxidation, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy were employed to characterize the catalysts. Even just 0.1wt% Na was observed to have a negative effect on CO methanation for the Na/Ni/SiO<SUB>2</SUB> and Na/Ni/CeO<SUB>2</SUB> catalysts owing to surface blockage of the Ni metal. The negative effect of Na on CO<SUB>2</SUB> methanation was also observed for the Na/Ni/CeO<SUB>2</SUB> catalysts. Conversely, Na exhibited a positive effect upon CO<SUB>2</SUB> methanation over the Na/Ni/SiO<SUB>2</SUB> catalysts. The different effect of Na on CO<SUB>2</SUB> methanation is closely related to the amount of CO<SUB>2</SUB> chemisorbed on the catalysts. Stable catalytic activity for CO and CO<SUB>2</SUB> methanation was observed for Ni/SiO<SUB>2</SUB>, Na/Ni/SiO<SUB>2</SUB>, and Ni/CeO<SUB>2</SUB>. However, the Na/Ni/CeO<SUB>2</SUB> catalyst was deactivated during CO methanation owing to coke formation following olefin production. However, this catalyst was stable for CO<SUB>2</SUB> methanation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CO methanation activity decreases with Na content over Na/Ni/SiO<SUB>2</SUB> and Na/Ni/CeO<SUB>2</SUB>. </LI> <LI> CO<SUB>2</SUB> methanation activity decreases with Na content over Na/Ni/CeO<SUB>2</SUB>. </LI> <LI> The promotional effect of Na on CO<SUB>2</SUB> methanation was confirmed over Na/Ni/SiO<SUB>2</SUB>. </LI> <LI> The addition of Na decreases the surface area of Na/Ni/SiO<SUB>2</SUB> and Na/Ni/CeO<SUB>2</SUB>. </LI> <LI> CO<SUB>2</SUB> methanation activity is related to the amount of CO<SUB>2</SUB> chemisorbed on the catalyst. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>