Changes in the Electrical Conductivity and Catalytic Property of Vanadium Iron Borophosphate Glasses with Crystallization

차재민,정화진,류봉기 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.10

Glasses were prepared in the V2O5−P2O5−B2O3 system containing Fe2O3 and were crystallized to examine the changes in the structure, as well as the catalytic and the electrical properties. The glasses were annealed in a graphite mold at a temperature above the glass transition temperature for 1 h and were heat-treated at the crystallization temperature for 1 h, 6 h and 12 h, respectively. Fourier-transform infrared spectroscopy (FTIR) was employed to analyze the structural changes of the V−O bonds after crystallization while the X-ray photoelectron spectroscopy (XPS) analysis indicated a decrease in V5+ and an increase in V4+ amounts. The X-ray diffraction (XRD) analysis indicated that a new crystalline phase of non-stoichiometric Fe0.12V2O5 was formed after 1 h of heat treatment. Structural changes induced by the crystallization were analyzed by determining the molecular volume from the sample density. The conductivity and the catalytic property were examined based on the migration of V and Fe ions exhibiting different valence states with crystallization. Both the conductivity and the catalytic property improved after the samples had been crystallized at the crystallization peak temperature (Tp). Furthermore, as compared to the sample heat treated for 1 h, the conductance and catalytic properties were improved for samples crystallized at Tp for 6 h and 12 h.

The effect of CNTs on V-Ce/TiO2 for low-temperature selective catalytic reduction of NO

윤재랑,김민재,이승재,류인수,정순관,이규복,전상구 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.9

Carbon nanotubes (CNTs) are widely utilized as catalyst promoters because of their unique structure andelectrical properties. In this study, CNTs were added as a promoter to V-Ce/TiO2 (VCT), which is a commercial catalystused for the NH3-SCR reaction. We investigated the role of CNTs in the V-Ce/TiO2-CNTs (VCTC) catalyst. Therefore,we characterized them using X-ray diffraction (XRD), N2 adsorption/desorption experiments, thermogravimetricanalysis (TGA), transmission electron microscopy (TEM), temperature-programmed reduction of H2 (H2-TPR), temperature-programmed desorption of NO/NH3 (NO/NH3-TPD), X-ray photoelectron spectroscopy (XPS), and in situFourier transform infrared spectroscopy (FT-IR). Higher NO conversion and N2 selectivity were achieved in the VCTCcatalyst than in the VCT catalyst, confirming the favorable effect of CNTs on the NH3-SCR reaction. Additionally,CNTs considerably influenced the crystal structure formation of the metal oxides located on the catalyst surface. Consequently,metal-metal and metal-support undergo distinct interactions, thereby positively influencing catalytic characteristicssuch as redox properties, oxidation state, acid sites, and the formation of nitrate species.

Novel Mn^II coordination compounds constructed from benzoate and various bipyridyl ligands: Magnetic property and catalytic activity

Hwang, I.H.,Jo, Y.D.,Kim, H.Y.,Kang, J.,Noh, J.Y.,Hyun, M.Y.,Kim, C.,Kim, Y.,Kim, S.J. Pergamon Press 2012 Polyhedron Vol.42 No.1

Three new Mn<SUP>II</SUP>-benzoates coordination polymers containing various bipyridyl ligands (3,3'-dipicoylamine (3), 3-methylisoquinoline (4), and 4,4'-dithiopyridine (5)) and a [Mn<SUB>6</SUB>(O<SUB>2</SUB>CPh)<SUB>10</SUB>(μ<SUB>4</SUB>-OH)<SUB>2</SUB>(CH<SUB>3</SUB>OH)<SUB>3</SUB>(H<SUB>2</SUB>O)].1.5(C<SUB>4</SUB>H<SUB>4</SUB>N<SUB>2</SUB>) cluster (1) have prepared and their structures were determined. The bipyridyl ligands can act as bridging ligands to produce 1-D or 2-D polymeric compounds. The pyrazine produced a Mn<SUB>6</SUB> cluster molecule, and 3-methylisoquinoline did a benzoate-bridged 1-D Mn<SUP>II</SUP> compound. The Mn<SUB>6</SUB> cluster (1) and 1-D Mn<SUP>II</SUP> compounds (3) and (4) show antiferromagnetic property. The compounds 1, 3, and 4 have catalyzed efficiently the transesterification of a variety of esters, while 5 has displayed a very slow conversion. The thermal stabilities of these complexes were also examined.

Electrochemical Behavior of Pt-Ru Catalysts on Zeolite-templated Carbon Supports for Direct Methanol Fuel Cells

Lim, Tae-Jin,Lee, Seul-Yi,Yoo, Yoon-Jong,Park, Soo-Jin Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.12

Zeolite-templated carbons (ZTCs), which have high specific surface area, were prepared by a conventional templating method using microporous zeolite-Y for catalyst supports in direct methanol fuel cells. The ZTCs were synthesized at different temperatures to investigate the characteristics of the surface produced and their electrochemical properties. Thereafter, Pt-Ru was deposited at different carbonization temperatures by a chemical reduction method. The crystalline and structural features were investigated using X-ray diffraction and scanning electron microscopy. The textural properties of the ZTCs were investigated by analyzing $N_2$/77 K adsorption isotherms using the Brunauer-Emmett-Teller equation, while the micro- and meso-pore size distributions were analyzed using the Barrett-Joyner-Halenda and Harvarth-Kawazoe methods, respectively. The surface morphology was characterized using transmission electron microscopy and inductively coupled plasma-mass spectrometry. The electrochemical properties of the Pt-Ru/ZTCs catalysts were also analyzed by cyclic voltammetry measurements. From the results, the ZTCs carbonized at $900^{\circ}C$ show the highest specific surface areas. In addition, ZTC900-PR led to uniform dispersion of Pt-Ru on the ZTCs, which enhanced the electro-catalytic activity of the Pt-Ru catalysts. The particle size of ZTC900-PR catalyst is about 3.4 nm, also peak current density from the CV plot is $12.5mA/cm^2$. Therefore, electro-catalytic activity of the ZTC900-PR catalyst is higher than those of ZTC1000-PR catalyst.

Electrochemical Behavior of Pt-Ru Catalysts on Zeolite-templated Carbon Supports for Direct Methanol Fuel Cells

Tae-Jin Lim,이슬이,유윤종,박수진 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.12

Zeolite-templated carbons (ZTCs), which have high specific surface area, were prepared by a conventional templating method using microporous zeolite-Y for catalyst supports in direct methanol fuel cells. The ZTCs were synthesized at different temperatures to investigate the characteristics of the surface produced and their electrochemical properties. Thereafter, Pt-Ru was deposited at different carbonization temperatures by a chemical reduction method. The crystalline and structural features were investigated using X-ray diffraction and scanning electron microscopy. The textural properties of the ZTCs were investigated by analyzing N2/77 K adsorption isotherms using the Brunauer-Emmett-Teller equation, while the micro- and meso-pore size distributions were analyzed using the Barrett-Joyner-Halenda and Harvarth-Kawazoe methods, respectively. The surface morphology was characterized using transmission electron microscopy and inductively coupled plasma-mass spectrometry. The electrochemical properties of the Pt-Ru/ZTCs catalysts were also analyzed by cyclic voltammetry measurements. From the results, the ZTCs carbonized at 900 °C show the highest specific surface areas. In addition, ZTC900-PR led to uniform dispersion of Pt-Ru on the ZTCs, which enhanced the electro-catalytic activity of the Pt-Ru catalysts. The particle size of ZTC900-PR catalyst is about 3.4 nm, also peak current density from the CV plot is 12.5 mA/cm2. Therefore, electro-catalytic activity of the ZTC900-PR catalyst is higher than those of ZTC1000-PR catalyst.

In Search of Engineered Prokaryotic Chlorophyllases: A Bioinformatics Approach

Ebrahim Sharafi,Jamshid Farmani,Ali Pakdin Parizi,Ali Dehestani 한국생물공학회 2018 Biotechnology and Bioprocess Engineering Vol.23 No.5

Chlorophyllase (Chlase) is considered as the first and most important enzyme in chlorophyll degradation pathway. Although there is abundant information regarding plant Chlases and their biological functions, comparatively little is known about their prokaryotic counterparts. In the present study, we employed several bioinformatics tools to assess the phylogenetic relationships in bacterial and cyanobacterial Chlases as well as predicting their molecular and physicochemical properties. The phylogenetic tree analysis classified the bacterial and cyanobacterial chlorophyllases into three distinct clades. All bacterial and cyanobacterial chlorophyllases possessed at least one alpha/ beta hydrolase family domain (pfam12695). Cyanobacterial chlorophyllases pI analysis indicated that they generally have acidic pH, while the pI of bacterial chlorophyllases ranged from acidic (4.58) to highly basic (10.78). Cyanobacterial chlorophyllases generally contained 1 disulfide bond, while bacterial chlorophyllases averagely contained 3 disulfide bonds. Interestingly, while cyanobacterial chlorophyllases contained one or two N-glycosylation sites, bacterial chlorophyllases contained higher numbers of N-glycosylation sites (6 and 7). The findings of the present study would be useful in paving the road for sophisticated engineering of prokaryotic chlorophyllases for biotechnological applications. It was also exhibited that catalytic triad (serine, glutamate or aspartate and histidine) is a critical factor for chlorophyllase activity.

Catalytic Degradation of waste HDPE over Acidic Catalysts with Different Pore Sizes

Lee, Kyong-Hwan,Shin, Dae-Hyun 한국공업화학회 2003 Journal of Industrial and Engineering Chemistry Vol.9 No.5

The catalytic degradation of waste high-density polyethylene (HDPE) over solid acid catalysts (zeolite Y, silica-alumina (SA), fluid catalytic cracking (FCC) catalyst) with different physicochemical pro-perties in a stirred semi-batch reactor at 450℃ was investigated. The product yield and composition of the liquid product were compared for three catalysts. Zeolite Y with mainly micropores showed the highest gas yield and lowest liquid yield, despite its mild acidic properties, while the SA catalyst with only mesopores showed a higher liquid yield than zeolite Y. Among the three catalysts, the FCC catalyst with a bimodal pore size distribution and mild acidic properties exhibited the best catalytic performance for liquid yield. The catalysts containing zeolite Y enhanced the production of the aromatic component. These results suggest the proper physicochemical properties for a catalyst to enhance the catalytic degradation of waste plastics into useful liquid products.

The critical role of intrinsic physicochemical properties of catalysts for CO2 hydrogenation to methanol: A state of the art review

Ijaz Hussain,Umar Mustapha,Ahmed T. Al-Qathmi,Zuhair O Malaibari,Sarah Alotaibi,Samia,Khalid Alhooshani,Saheed A. Ganiyu 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.128 No.-

Catalytic hydrogenation is one of the most innovative techniques for reducing atmospheric carbon dioxide(CO2) by converting it into beneficial products such as methanol (CH3OH). CH3OH is an alternativefuel that offers a practical, effective, and efficient solution to the energy storage problem. Despite the significantadvances in the CO2 hydrogenation process, developing an appropriate and efficient catalytic systemremains a significant obstacle and challenge. Many review papers on catalyst development for CO2hydrogenation have been published, focusing on the influence of transition, noble metal-based catalysts,and process parameter. However, present knowledge of the mutually reinforcing correlations betweencatalytic properties and CO2 hydrogenation activity has to be enhanced. It is very important to have acomprehensive understanding of the relationship between catalytic performance and physicochemicalproperties in order to create a catalytic system that is both highly efficient and economically viable forcommercialization. Therefore, the focus of this review is on the synergistic interactions between catalyticCO2 hydrogenation activity and catalytic properties such as porosity, surface area, metal-support interaction,metal dispersion, oxygen vacancies, metal particle size, reducibility, and chemical composition acidity/basicity. Furthermore, this review examined and compared the most up-to-date findings on thehydrogenation of CO2 to CH3OH using various heterogeneous catalysts. It also discussed the challengesand prospects for improving CH3OH production by CO2 hydrogenation. Researchers and environmentalistsin academia and industry who are interested in finding ways to reduce CO2 emissions will find thisoverview to be a valuable resource.

Effect of CeO2 and B2O3 doping on the Structural, Optical and Catalytic Properties of Zinc Phosphate Glasses

( Jae Yeop Chung ),( Il Gu Kim ),( Bong Ki Ryu ) 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.11

We investigated the effect of CeO2 content on the catalytic behavior of (68-x)P2O5-32ZnO-xCeO2 (x = 0, 4, 8, 12, and 16 mol%) glasses. In addition, we confirmed the effect of the addition of B2O3 on the catalytic properties of (60-x)P2O5-32ZnO-8CeO2-xB2O3 (x = 0, 5, 10, 15 and 20 mol%) glasses. Using TGA, we confirmed that the catalytic activity of the (68-x)P2O5-32ZnO-xCeO2 glasses increased with CeO2 content. Furthermore, the catalytic activity of (60-x)P2O5-32ZnO-8CeO2-xB2O3 decreased until the B2O3 content attained 15 mol%, beyond which, it increased. The change in the catalytic properties in relation to the content of B2O3 and CeO2 was analyzed through FT-IR, XPS, optical band gap energy, and density.

A review on dry reforming of methane in aspect of catalytic properties

Jang, Won-Jun,Shim, Jae-Oh,Kim, Hak-Min,Yoo, Seong-Yeun,Roh, Hyun-Seog Elsevier 2019 CATALYSIS TODAY - Vol.324 No.-

<P><B>Abstract</B></P> <P>Because the whole world is under threat from climate change, 195 countries decided to reduce greenhouse gas (GHG) emissions by adopting the “Paris Agreement”. The mitigation and utilization of GHG have become the most significant challenges in the area of green energy research. One feasible solution is the reforming of methane with carbon dioxide (called dry reforming of methane, DRM) that converts the two main GHGs (CO<SUB>2</SUB> and CH<SUB>4</SUB>) into synthesis gas (H<SUB>2</SUB> and CO), which is a resource for the manufacture of useful value-added products. The main issue that needs to be addressed for DRM is the deactivation of catalysts by sintering and carbon formation. Design of a viable catalyst that exhibits high catalytic activity and stability, as well as resistance against deactivation, could be accomplished by making appropriate choices of active metal, support, promoter, structure and methods for preparation and activation. Numerous studies and reviews have dealt with various aspects of DRM. This review focuses on the physicochemical properties of the pertinent catalysts and their role in the catalytic performance needed for DRM. Specifically, the interaction between components, dispersion, particle size, basicity, oxygen storage capacity, reducibility, porosity and surface area are discussed. This study provides the understanding of catalytic properties and their correlation with catalytic performance needed for the rational design of catalysts and suitable for DRM.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Key factors for dry reforming of methane (DRM). </LI> <LI> Comprehensive review on role of catalytic properties for DRM. </LI> <LI> Rational and suitable design of catalysts for DRM. </LI> <LI> Interaction, size, basicity, oxygen storage capacity, reducibility and porosity. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>