The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Shigeki Kato - One of the best experts on this subject based on the ideXlab platform.
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Role of isomerization channel in unimolecular Dissociation Reaction H2CO→H2+CO: Ab initio global potential energy surface and classical trajectory analysis
The Journal of Chemical Physics, 2002Co-Authors: Takehiro Yonehara, Shigeki KatoAbstract:We constructed a full dimensional potential energy function of H2CO that can describe both the Dissociation and isomerization channels by the modified Shepard interpolation method. Ab initio calculations at the MP2/cc-pVTZ level were carried out to obtain the local potential functions at about 4700 points. The interpolant points were sampled by classical trajectory calculations and by the grid searches in the internal coordinate space. Classical trajectory calculations were performed to examine the intramolecular dynamics associated with the Dissociation as well as the product state distributions. The time scale of intramolecular vibrational energy randomization was much faster than that of the Dissociation Reaction. The Dissociation rate was obtained from the classical trajectory results and the effect of the isomerization channel on the Dissociation was estimated. The calculated rate constants were compared with those by Rice–Ramsperger–Kassel–Marcus theory.We constructed a full dimensional potential energy function of H2CO that can describe both the Dissociation and isomerization channels by the modified Shepard interpolation method. Ab initio calculations at the MP2/cc-pVTZ level were carried out to obtain the local potential functions at about 4700 points. The interpolant points were sampled by classical trajectory calculations and by the grid searches in the internal coordinate space. Classical trajectory calculations were performed to examine the intramolecular dynamics associated with the Dissociation as well as the product state distributions. The time scale of intramolecular vibrational energy randomization was much faster than that of the Dissociation Reaction. The Dissociation rate was obtained from the classical trajectory results and the effect of the isomerization channel on the Dissociation was estimated. The calculated rate constants were compared with those by Rice–Ramsperger–Kassel–Marcus theory.
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role of isomerization channel in unimolecular Dissociation Reaction h2co h2 co ab initio global potential energy surface and classical trajectory analysis
Journal of Chemical Physics, 2002Co-Authors: Takehiro Yonehara, Shigeki KatoAbstract:We constructed a full dimensional potential energy function of H2CO that can describe both the Dissociation and isomerization channels by the modified Shepard interpolation method. Ab initio calculations at the MP2/cc-pVTZ level were carried out to obtain the local potential functions at about 4700 points. The interpolant points were sampled by classical trajectory calculations and by the grid searches in the internal coordinate space. Classical trajectory calculations were performed to examine the intramolecular dynamics associated with the Dissociation as well as the product state distributions. The time scale of intramolecular vibrational energy randomization was much faster than that of the Dissociation Reaction. The Dissociation rate was obtained from the classical trajectory results and the effect of the isomerization channel on the Dissociation was estimated. The calculated rate constants were compared with those by Rice–Ramsperger–Kassel–Marcus theory.We constructed a full dimensional potential energy function of H2CO that can describe both the Dissociation and isomerization channels by the modified Shepard interpolation method. Ab initio calculations at the MP2/cc-pVTZ level were carried out to obtain the local potential functions at about 4700 points. The interpolant points were sampled by classical trajectory calculations and by the grid searches in the internal coordinate space. Classical trajectory calculations were performed to examine the intramolecular dynamics associated with the Dissociation as well as the product state distributions. The time scale of intramolecular vibrational energy randomization was much faster than that of the Dissociation Reaction. The Dissociation rate was obtained from the classical trajectory results and the effect of the isomerization channel on the Dissociation was estimated. The calculated rate constants were compared with those by Rice–Ramsperger–Kassel–Marcus theory.
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full dimensional quantum dynamics study on the mode specific unimolecular Dissociation Reaction of hfco
Journal of Chemical Physics, 2000Co-Authors: Takeshi Yamamoto, Shigeki KatoAbstract:The mode specificity of the unimolecular Reaction of HFCO is studied by six-dimensional quantum dynamics calculations. The energy and mode dependency of the Dissociation rate is examined by propagating a number of wave packets with a small energy dispersion representing highly excited states with respect to a specific vibrational mode. The wave packets are generated by applying a set of filter operators onto a source vibrational state. All the information necessary for propagating the wave packets is obtained from a single propagation of the source state, thus allowing a significant decrease of computational effort. The relevant spectral peaks are assigned using the three-dimensional CH chromophore Hamiltonian. The resulting Dissociation rate of the CH stretching excited state is in agreement with that obtained from a statistical theory, while the rates of the out-of-plane bending excited states are about one order of magnitude smaller than the statistical rates. A local-mode analysis also shows that the ...
Namjo Jeong - One of the best experts on this subject based on the ideXlab platform.
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assessing the behavior of the feed water constituents of a pilot scale 1000 cell pair reverse electrodialysis with seawater and municipal wastewater effluent
Water Research, 2019Co-Authors: Kyosik Hwang, Haejun Jeong, Seungcheol Yang, Jiyeon Choi, Namjo JeongAbstract:Abstract Reverse electrodialysis (RED) has vast potential as a clean, nonpolluting, and sustainable renewable energy source; however, pilot-scale RED studies employing real waters remain rare. This study reports the largest RED (1000 cell pairs, 250 m2) with municipal wastewater effluent (1.3–5.7 mS/cm) and seawater (52.9–53.8 mS/cm) as feed solutions. The RED stack was operated at a velocity of 1.5 cm/s and the pilot plant produced 95.8 W of power (0.38 W/m2 total membrane or 0.76 W/m2cell pair). During operation of the RED, the inlet design of the stack, comprising thin spacers, and the water Dissociation Reaction at the cathode were revealed as vulnerabilities of the stack. Specifically, pressure drops at the fluid inlet parts had the most detrimental effects on power output due to clogged spacers around the inlet parts. In addition, precipitates resulting in inorganic fouling were inevitable during the water Dissociation Reaction due to significant potential generated by the stack in the cathode chamber. Na+ and Cl− accounted for the majority of ions transferred from seawater to wastewater effluent through ion exchange membranes (IEMs). Moreover, some divalent cations in seawater, Mg2+ and Ca2+, were also transferred to the wastewater effluent. Some organics with relatively low molecular weights in the wastewater effluent passed through the IEMs, and their hydrophobic properties elevated the specific UV absorbance (SUVA) level in the seawater.
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assessing the behavior of the feed water constituents of a pilot scale 1000 cell pair reverse electrodialysis with seawater and municipal wastewater effluent
Water Research, 2019Co-Authors: Kyosik Hwang, Haejun Jeong, Seungcheol Yang, Jiyeon Choi, Namjo JeongAbstract:Abstract Reverse electrodialysis (RED) has vast potential as a clean, nonpolluting, and sustainable renewable energy source; however, pilot-scale RED studies employing real waters remain rare. This study reports the largest RED (1000 cell pairs, 250 m2) with municipal wastewater effluent (1.3–5.7 mS/cm) and seawater (52.9–53.8 mS/cm) as feed solutions. The RED stack was operated at a velocity of 1.5 cm/s and the pilot plant produced 95.8 W of power (0.38 W/m2 total membrane or 0.76 W/m2cell pair). During operation of the RED, the inlet design of the stack, comprising thin spacers, and the water Dissociation Reaction at the cathode were revealed as vulnerabilities of the stack. Specifically, pressure drops at the fluid inlet parts had the most detrimental effects on power output due to clogged spacers around the inlet parts. In addition, precipitates resulting in inorganic fouling were inevitable during the water Dissociation Reaction due to significant potential generated by the stack in the cathode chamber. Na+ and Cl− accounted for the majority of ions transferred from seawater to wastewater effluent through ion exchange membranes (IEMs). Moreover, some divalent cations in seawater, Mg2+ and Ca2+, were also transferred to the wastewater effluent. Some organics with relatively low molecular weights in the wastewater effluent passed through the IEMs, and their hydrophobic properties elevated the specific UV absorbance (SUVA) level in the seawater.
Athanasios G Konstandopoulos - One of the best experts on this subject based on the ideXlab platform.
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hydrogen production via sulfur based thermochemical cycles part 3 durability and post characterization of silicon carbide honeycomb substrates coated with metal oxide based candidate catalysts for the sulfuric acid decomposition step
International Journal of Hydrogen Energy, 2012Co-Authors: George Karagiannakis, Christos Agrafiotis, Chrysoula Pagkoura, Athanasios G Konstandopoulos, Dennis Thomey, Lamark De Oliveira, Martin Roeb, Christian SattlerAbstract:Abstract This work is a follow-up of previous efforts reported on the synthesis of various single and mixed oxide materials and their evaluation as catalysts for the sulfuric acid Dissociation Reaction for the production of SO 2 and O 2 . The current work concerns the comparative assessment of Fe 2 O 3 , CuO, Cu–Fe, Fe–Cr, Cu–Al and Cu–Fe–Al mixed oxides coated as catalysts on silicon carbide monolithic honeycomb structures, with respect to sulfuric acid decomposition Reaction conditions for 100 h at 850 °C and ambient pressure, as well as their ex-situ characterization after such operation. The exposure conditions are representative to a potential future real application. The exposure time, although of relatively short-term, is adequate to extract safe conclusions on the stability and therefore to a large extent also on the suitability of the candidate oxide-based catalysts. All catalytic systems tested exhibited high SO 3 conversions reaching or exceeding 70%, for space velocities in the range of 5–35 h −1 . For some of the samples, the relatively high initial activity decreased by about 5–10 percentage points in the course of the 100 h testing, reaching stable mean values. It was concluded that Fe 2 O 3 , CuO and Fe–Cr mixed oxide retained their chemical and structural stability after exposure to Reaction conditions, while the other three mixed oxides studied suffered from significant phase decomposition phenomena. Based on the fact that the initial catalytic activity of the Fe–Cr mixed oxide, as identified in a previous comparative study among several materials, was found higher than the ones of Fe 2 O 3 and CuO and relatively close to the one of the highly active but costly Pt/Al 2 O 3 catalyst, the particular mixed oxide is considered a promising catalyst for the SO 3 Dissociation Reaction.
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hydrogen production via sulfur based thermochemical cycles part 1 synthesis and evaluation of metal oxide based candidate catalyst powders for the sulfuric acid decomposition step
International Journal of Hydrogen Energy, 2011Co-Authors: George Karagiannakis, Christos Agrafiotis, A Zygogianni, Chrysoula Pagkoura, Athanasios G KonstandopoulosAbstract:The present work concerns the synthesis of various single and mixed oxide materials and their study as catalysts for the sulfuric acid Dissociation Reaction via which the production of SO2 and O2 is achieved. This is the most energy intensive step of sulfur-based thermochemical cycles for the production of hydrogen. Commercial (i.e. FeO, Fe3O4 ,F e2O3, CuO, Cr2O3, g-Al2O3, Pt/g-Al2O3) and in-house binary and ternary compositions of the CueFeeAl system as well as FeeCr mixed oxide materials prepared by the Solution Combustion Synthesis (SCS) technique were comparatively tested. The materials were studied in
George Karagiannakis - One of the best experts on this subject based on the ideXlab platform.
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hydrogen production via sulfur based thermochemical cycles part 3 durability and post characterization of silicon carbide honeycomb substrates coated with metal oxide based candidate catalysts for the sulfuric acid decomposition step
International Journal of Hydrogen Energy, 2012Co-Authors: George Karagiannakis, Christos Agrafiotis, Chrysoula Pagkoura, Athanasios G Konstandopoulos, Dennis Thomey, Lamark De Oliveira, Martin Roeb, Christian SattlerAbstract:Abstract This work is a follow-up of previous efforts reported on the synthesis of various single and mixed oxide materials and their evaluation as catalysts for the sulfuric acid Dissociation Reaction for the production of SO 2 and O 2 . The current work concerns the comparative assessment of Fe 2 O 3 , CuO, Cu–Fe, Fe–Cr, Cu–Al and Cu–Fe–Al mixed oxides coated as catalysts on silicon carbide monolithic honeycomb structures, with respect to sulfuric acid decomposition Reaction conditions for 100 h at 850 °C and ambient pressure, as well as their ex-situ characterization after such operation. The exposure conditions are representative to a potential future real application. The exposure time, although of relatively short-term, is adequate to extract safe conclusions on the stability and therefore to a large extent also on the suitability of the candidate oxide-based catalysts. All catalytic systems tested exhibited high SO 3 conversions reaching or exceeding 70%, for space velocities in the range of 5–35 h −1 . For some of the samples, the relatively high initial activity decreased by about 5–10 percentage points in the course of the 100 h testing, reaching stable mean values. It was concluded that Fe 2 O 3 , CuO and Fe–Cr mixed oxide retained their chemical and structural stability after exposure to Reaction conditions, while the other three mixed oxides studied suffered from significant phase decomposition phenomena. Based on the fact that the initial catalytic activity of the Fe–Cr mixed oxide, as identified in a previous comparative study among several materials, was found higher than the ones of Fe 2 O 3 and CuO and relatively close to the one of the highly active but costly Pt/Al 2 O 3 catalyst, the particular mixed oxide is considered a promising catalyst for the SO 3 Dissociation Reaction.
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hydrogen production via sulfur based thermochemical cycles part 1 synthesis and evaluation of metal oxide based candidate catalyst powders for the sulfuric acid decomposition step
International Journal of Hydrogen Energy, 2011Co-Authors: George Karagiannakis, Christos Agrafiotis, A Zygogianni, Chrysoula Pagkoura, Athanasios G KonstandopoulosAbstract:The present work concerns the synthesis of various single and mixed oxide materials and their study as catalysts for the sulfuric acid Dissociation Reaction via which the production of SO2 and O2 is achieved. This is the most energy intensive step of sulfur-based thermochemical cycles for the production of hydrogen. Commercial (i.e. FeO, Fe3O4 ,F e2O3, CuO, Cr2O3, g-Al2O3, Pt/g-Al2O3) and in-house binary and ternary compositions of the CueFeeAl system as well as FeeCr mixed oxide materials prepared by the Solution Combustion Synthesis (SCS) technique were comparatively tested. The materials were studied in
Takehiro Yonehara - One of the best experts on this subject based on the ideXlab platform.
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Role of isomerization channel in unimolecular Dissociation Reaction H2CO→H2+CO: Ab initio global potential energy surface and classical trajectory analysis
The Journal of Chemical Physics, 2002Co-Authors: Takehiro Yonehara, Shigeki KatoAbstract:We constructed a full dimensional potential energy function of H2CO that can describe both the Dissociation and isomerization channels by the modified Shepard interpolation method. Ab initio calculations at the MP2/cc-pVTZ level were carried out to obtain the local potential functions at about 4700 points. The interpolant points were sampled by classical trajectory calculations and by the grid searches in the internal coordinate space. Classical trajectory calculations were performed to examine the intramolecular dynamics associated with the Dissociation as well as the product state distributions. The time scale of intramolecular vibrational energy randomization was much faster than that of the Dissociation Reaction. The Dissociation rate was obtained from the classical trajectory results and the effect of the isomerization channel on the Dissociation was estimated. The calculated rate constants were compared with those by Rice–Ramsperger–Kassel–Marcus theory.We constructed a full dimensional potential energy function of H2CO that can describe both the Dissociation and isomerization channels by the modified Shepard interpolation method. Ab initio calculations at the MP2/cc-pVTZ level were carried out to obtain the local potential functions at about 4700 points. The interpolant points were sampled by classical trajectory calculations and by the grid searches in the internal coordinate space. Classical trajectory calculations were performed to examine the intramolecular dynamics associated with the Dissociation as well as the product state distributions. The time scale of intramolecular vibrational energy randomization was much faster than that of the Dissociation Reaction. The Dissociation rate was obtained from the classical trajectory results and the effect of the isomerization channel on the Dissociation was estimated. The calculated rate constants were compared with those by Rice–Ramsperger–Kassel–Marcus theory.
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role of isomerization channel in unimolecular Dissociation Reaction h2co h2 co ab initio global potential energy surface and classical trajectory analysis
Journal of Chemical Physics, 2002Co-Authors: Takehiro Yonehara, Shigeki KatoAbstract:We constructed a full dimensional potential energy function of H2CO that can describe both the Dissociation and isomerization channels by the modified Shepard interpolation method. Ab initio calculations at the MP2/cc-pVTZ level were carried out to obtain the local potential functions at about 4700 points. The interpolant points were sampled by classical trajectory calculations and by the grid searches in the internal coordinate space. Classical trajectory calculations were performed to examine the intramolecular dynamics associated with the Dissociation as well as the product state distributions. The time scale of intramolecular vibrational energy randomization was much faster than that of the Dissociation Reaction. The Dissociation rate was obtained from the classical trajectory results and the effect of the isomerization channel on the Dissociation was estimated. The calculated rate constants were compared with those by Rice–Ramsperger–Kassel–Marcus theory.We constructed a full dimensional potential energy function of H2CO that can describe both the Dissociation and isomerization channels by the modified Shepard interpolation method. Ab initio calculations at the MP2/cc-pVTZ level were carried out to obtain the local potential functions at about 4700 points. The interpolant points were sampled by classical trajectory calculations and by the grid searches in the internal coordinate space. Classical trajectory calculations were performed to examine the intramolecular dynamics associated with the Dissociation as well as the product state distributions. The time scale of intramolecular vibrational energy randomization was much faster than that of the Dissociation Reaction. The Dissociation rate was obtained from the classical trajectory results and the effect of the isomerization channel on the Dissociation was estimated. The calculated rate constants were compared with those by Rice–Ramsperger–Kassel–Marcus theory.