1
|
Kazi SH, Sheraz MA, Anwar Z, Musharraf SG, Ahmed S, Bano R, Mirza T, Heo K, Na JH. Photolysis of tolfenamic acid in aqueous and organic solvents: a kinetic study. RSC Adv 2024; 14:21383-21397. [PMID: 38979457 PMCID: PMC11228578 DOI: 10.1039/d4ra01369g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Accepted: 06/27/2024] [Indexed: 07/10/2024] Open
Abstract
Tolfenamic acid (TA) is a non-steroidal anti-inflammatory drug that was studied for its photodegradation in aqueous (pH 2.0-12.0) and organic solvents (acetonitrile, methanol, ethanol, 1-propanol, 1-butanol). TA follows first-order kinetics for its photodegradation, and the apparent first-order rate constants (k obs) are in the range of 0.65 (pH 12.0) to 6.94 × 10-2 (pH 3.0) min-1 in aqueous solution and 3.28 (1-butanol) to 7.69 × 10-4 (acetonitrile) min-1 in organic solvents. The rate-pH profile for TA photodegradation is an inverted V (∧) or V-top shape, indicating that the cationic form is more susceptible to acid hydrolysis than the anionic form of TA, which is less susceptible to alkaline hydrolysis. The fluorescence behavior of TA also exhibits a V-top-shaped curve, indicating maximum fluorescence intensity at pH 3.0. TA is highly stable at a pH range of 5.0-7.0, making it suitable for formulation development. In organic solvents, the photodegradation rate of TA increases with the solvent's dielectric constant and solvent acceptor number, indicating solute-solvent interactions. The values of k obs decreased with increased viscosity of the solvents due to diffusion-controlled processes. The correlation between k obs versus ionization potential and solvent density has also been established. A total of 17 photoproducts have been identified through LC-MS, of which nine have been reported for the first time. It has been confirmed through electron spin resonance (ESR) spectrometry that the excited singlet state of TA is converted into an excited triplet state through intersystem crossing, which results in an increased rate of photodegradation in acetonitrile.
Collapse
Affiliation(s)
- Sadia Hafeez Kazi
- Department of Pharmaceutics, Baqai Institute of Pharmaceutical Sciences, Baqai Medical University Karachi-75340 Pakistan
| | - Muhammad Ali Sheraz
- Department of Pharmaceutics, Baqai Institute of Pharmaceutical Sciences, Baqai Medical University Karachi-75340 Pakistan
| | - Zubair Anwar
- Department of Pharmaceutical Chemistry, Baqai Institute of Pharmaceutical Sciences, Baqai Medical University Karachi-75340 Pakistan
| | - Syed Ghulam Musharraf
- Third World Center for Science and Technology, H.E.J. Research Institute of Chemistry, University of Karachi Karachi-75270 Pakistan
| | - Sofia Ahmed
- Department of Pharmaceutics, Baqai Institute of Pharmaceutical Sciences, Baqai Medical University Karachi-75340 Pakistan
| | - Raheela Bano
- Dow College of Pharmacy, Dow University of Health Sciences (Ojha Campus) Karachi Pakistan
| | - Tania Mirza
- Department of Pharmaceutical Chemistry, Baqai Institute of Pharmaceutical Sciences, Baqai Medical University Karachi-75340 Pakistan
| | - Kyuyoung Heo
- Reliability Assessment Center, Korea Research Institute of Chemical Technology Daejeon 34114 Republic of Korea
| | - Jun-Hee Na
- Department of Convergence System Engineering, Chungnam National University Daejeon 34134 Republic of Korea
| |
Collapse
|
2
|
Liu W, Zheng X, Xu Q. Supercritical CO 2 Directional-Assisted Synthesis of Low-Dimensional Materials for Functional Applications. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2301097. [PMID: 37093220 DOI: 10.1002/smll.202301097] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 04/07/2023] [Indexed: 05/03/2023]
Abstract
Supercritical CO2 (SC CO2 ), as one of the unique fluids that possess fascinating properties of gas and liquid, holds great promise in chemical reactions and fabrication of materials. Building special nanostructures via SC CO2 for functional applications has been the focus of intense research for the past two decades, with facile regulated reaction conditions and a particular reaction field to operate compared to the more widely used solvent systems. In this review, the significance of SC CO2 on fabricating various functional materials including modification of 1D carbon nanotubes, 2D materials, and 2D heterostructures is stated. The fundamental aspects involving building special nanostructures via SC CO2 are explored: how their structure, morphology, and chemical composition be affected by the SC CO2 . Various optimization strategies are outlined to improve their performances, and recent advances are combined to present a coherent understanding of the mechanism of SC CO2 acting on these functional nanostructures. The wide applications of these special nanostructures in catalysis, biosensing, optoelectronics, microelectronics, and energy transformation are discussed. Moreover, the current status of SC CO2 research, the existing scientific issues, and application challenges, as well as the possible future directions to advance this fertile field are proposed in this review.
Collapse
Affiliation(s)
- Wei Liu
- Henan Institute of Advanced Technology, Zhengzhou University, Zhengzhou, 450052, P. R. China
| | - Xiaoli Zheng
- College of Materials Science and Engineering, Zhengzhou University, Zhengzhou, 450001, P. R. China
| | - Qun Xu
- Henan Institute of Advanced Technology, Zhengzhou University, Zhengzhou, 450052, P. R. China
- College of Materials Science and Engineering, Zhengzhou University, Zhengzhou, 450001, P. R. China
| |
Collapse
|
3
|
Zhou Y, Xu Q. Supercritical CO 2-induced anti-nanoconfinement effect to obtain novel 2D structures. Phys Chem Chem Phys 2023; 25:3607-3616. [PMID: 36254862 DOI: 10.1039/d2cp03565k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Space confined reactions have emerged as a viable strategy for achieving important and fascinating properties in functional materials. Various scaffolds have been reported so far for confinement and it gives rise to the phenomenon of nanoconfinement, where the energetics and kinetics of catalytic reactions can be modulated upon confining the catalysts in a particular site. Although various systems have been reported so far for confinement, emphasis has been placed on the concept of space confinement, and the changes in the confined space itself are neglected. Strikingly, this critical issue would be touched on and revealed by supercritical CO2 (SC CO2) that is used in confined geometries. Herein, we define the structural changes of confined spaces induced by SC CO2 as an anti-nanoconfinement effect, which can bring about a series of variations together with electronic band and structural transformation. Moreover, progress in the design and applications of the anti-nanoconfinement effect is traced, and there is a discussion of emerging issues that have yet to be explored to achieve a future direction to develop more novel two-dimensional (2D) structures.
Collapse
Affiliation(s)
- Yannan Zhou
- College of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450052, P. R. China.
| | - Qun Xu
- College of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450052, P. R. China. .,Henan Institute of Advanced Technology, Zhengzhou University, Zhengzhou 450052, P. R. China
| |
Collapse
|
4
|
Wang H, Stillinger FH, Torquato S. Realizability of iso- g2 processes via effective pair interactions. J Chem Phys 2022; 157:224106. [DOI: 10.1063/5.0130679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
An outstanding problem in statistical mechanics is the determination of whether prescribed functional forms of the pair correlation function g2( r) [or equivalently, structure factor S( k)] at some number density ρ can be achieved by many-body systems in d-dimensional Euclidean space. The Zhang–Torquato conjecture states that any realizable set of pair statistics, whether from a nonequilibrium or equilibrium system, can be achieved by equilibrium systems involving up to two-body interactions. To further test this conjecture, we study the realizability problem of the nonequilibrium iso- g2 process, i.e., the determination of density-dependent effective potentials that yield equilibrium states in which g2 remains invariant for a positive range of densities. Using a precise inverse algorithm that determines effective potentials that match hypothesized functional forms of g2( r) for all r and S( k) for all k, we show that the unit-step function g2, which is the zero-density limit of the hard-sphere potential, is remarkably realizable up to the packing fraction ϕ = 0.49 for d = 1. For d = 2 and 3, it is realizable up to the maximum “terminal” packing fraction ϕ c = 1/2 d, at which the systems are hyperuniform, implying that the explicitly known necessary conditions for realizability are sufficient up through ϕ c. For ϕ near but below ϕ c, the large- r behaviors of the effective potentials are given exactly by the functional forms exp[ − κ( ϕ) r] for d = 1, r−1/2 exp[ − κ( ϕ) r] for d = 2, and r−1 exp[ − κ( ϕ) r] (Yukawa form) for d = 3, where κ−1( ϕ) is a screening length, and for ϕ = ϕ c, the potentials at large r are given by the pure Coulomb forms in the respective dimensions as predicted by Torquato and Stillinger [Phys. Rev. E 68, 041113 (2003)]. We also find that the effective potential for the pair statistics of the 3D “ghost” random sequential addition at the maximum packing fraction ϕ c = 1/8 is much shorter ranged than that for the 3D unit-step function g2 at ϕ c; thus, it does not constrain the realizability of the unit-step function g2. Our inverse methodology yields effective potentials for realizable targets, and, as expected, it does not reach convergence for a target that is known to be non-realizable, despite the fact that it satisfies all known explicit necessary conditions. Our findings demonstrate that exploring the iso- g2 process via our inverse methodology is an effective and robust means to tackle the realizability problem and is expected to facilitate the design of novel nanoparticle systems with density-dependent effective potentials, including exotic hyperuniform states of matter.
Collapse
Affiliation(s)
- Haina Wang
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
| | - Frank H. Stillinger
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
| | - Salvatore Torquato
- Department of Chemistry, Department of Physics, Princeton Institute of Materials, and Program in Applied and Computational Mathematics, Princeton University, Princeton, New Jersey 08544, USA
- School of Natural Sciences, Institute for Advanced Study, 1 Einstein Drive, Princeton, New Jersey 08540, USA
| |
Collapse
|
5
|
Wang Y, Liu G. Inhomogeneity Effects on Reactions in Supercritical Fluids: A Computational Study on the Pyrolysis of n-Decane. JACS AU 2022; 2:2081-2088. [PMID: 36186566 PMCID: PMC9516705 DOI: 10.1021/jacsau.2c00359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/19/2022] [Revised: 08/24/2022] [Accepted: 08/24/2022] [Indexed: 06/16/2023]
Abstract
Supercritical fluids exhibit peculiar inhomogeneity, which strongly affects reaction behaviors in them. However, explanations for inhomogeneity and its effect on reactions are both ambiguous so far. Here, we provide an atomic-level understanding of inhomogeneity effects on reactions via the computational method, with the example of n-decane pyrolysis under supercritical conditions. We describe the characteristic pyrolysis behaviors through collective variable-driven hyperdynamics (CVHD) simulations and explain the inhomogeneity of supercritical n-decane as the coexistence of gas-like and liquid-like atoms by a trained machine learning classifier. Due to their specific local environment, the appearance of liquid-like atoms under supercritical conditions significantly increases the type and frequency of bimolecular reactions and eventually causes changes in product distributions. Future research with this method is expected to extend the effect of inhomogeneity on other reactions under supercritical conditions or other condensed phases.
Collapse
Affiliation(s)
- Yutong Wang
- Key
Laboratory for Green Chemical Technology of Ministry of Education,
School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Guozhu Liu
- Key
Laboratory for Green Chemical Technology of Ministry of Education,
School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
- Haihe
Laboratory of Sustainable Chemical Transformations, Tianjin 300192, China
- Zhejiang
Institute of Tianjin University, Ningbo, Zhejiang 315201, China
| |
Collapse
|
6
|
Structure and Properties of Supercritical Water: Experimental and Theoretical Characterizations. J 2021. [DOI: 10.3390/j4040049] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Water in the supercritical region of the phase diagram exhibits a markedly different structure and properties from that at ambient conditions, which is useful in controlling chemical reactions. Nonetheless, the experimental, as well as theoretical, characterization of the substance is not easy because the region is next to the critical point. This article reviews the experimental as well as theoretical studies on water in the supercritical region and its properties as a solvent for chemical reactions, as carried out by the authors and based on small-angle X-ray scattering and the statistical mechanics theory of molecular liquids, also known as reference interaction-site model (RISM) theory.
Collapse
|
7
|
Dasgupta N, Shin YK, Fedkin MV, van Duin A. ReaxFF molecular dynamics simulations of electrolyte-water systems at supercritical temperature. J Chem Phys 2020; 152:204502. [PMID: 32486685 DOI: 10.1063/5.0006676] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
We have performed ReaxFF molecular dynamics simulations of alkali metal-chlorine pairs in different water densities at supercritical temperature (700 K) to elucidate the structural and dynamical properties of the system. The radial distribution function and the angular distribution function explain the inter-ionic structural and orientational arrangements of atoms during the simulation. The coordination number of water molecules in the solvation shell of ions increases with an increase in the radius of ions. We find that the self-diffusion coefficient of metal ions increases with a decrease in density under supercritical conditions due to the formation of voids within the system. The hydrogen bond dynamics has been interpreted by the residence time distribution of various ions, which shows Li+ having the highest water retaining capability. The void distribution within the system has been analyzed by using the Voronoi polyhedra algorithm providing an estimation of void formation within the system at high temperatures. We observe the formation of salt clusters of Na+ and K+ at low densities due to the loss of dielectric constants of ions. The diffusion of ions gets altered dramatically due to the formation of voids and nucleation of ions in the system.
Collapse
Affiliation(s)
- Nabankur Dasgupta
- Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Yun Kyung Shin
- Department of Mechanical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Mark V Fedkin
- Department of Mechanical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Adri van Duin
- Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| |
Collapse
|
8
|
Ng Pack G, Rotondaro MC, Shah PP, Mandal A, Erramilli S, Ziegler LD. Two-dimensional infrared spectroscopy from the gas to liquid phase: density dependent J-scrambling, vibrational relaxation, and the onset of liquid character. Phys Chem Chem Phys 2019; 21:21249-21261. [PMID: 31538165 DOI: 10.1039/c9cp04101j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ultrafast 2DIR spectra and pump-probe responses of the N2O ν3 asymmetric stretch in SF6 as a function of density from the gas to supercritical phase and liquid are reported. 2DIR spectra unequivocally reveal free rotor character at all densities studied in the gas and supercritical region. Analysis of the 2DIR spectra determines that J-scrambling or rotational relaxation in N2O is highly efficient, occurring in ∼1.5 to ∼2 collisions with SF6 at all non-liquid densities. In contrast, N2O ν3 vibrational energy relaxation requires ∼15 collisions, and complete vibrational equilibrium occurs on the ∼ns scale at all densities. An independent binary collision model is sufficient to describe these supercritical state point dynamics. The N2O ν3 in liquid SF6 2DIR spectrum shows no evidence of free rotor character or spectral diffusion. Using these 2DIR results, hindered rotor or liquid-like character is found in gas and all supercritical solutions for SF6 densities ≥ρ* = 0.3, and increases with SF6 density. 2DIR spectral analysis offers direct time domain evidence of critical slowing for SF6 solutions closest to the critical point density. Applications of 2DIR to other high density and supercritical solution dynamics and descriptions are discussed.
Collapse
Affiliation(s)
- Greg Ng Pack
- Department of Chemistry, Boston University, Boston, MA 02215, USA. and Photonics Center, Boston University, Boston, MA 02215, USA
| | - Matthew C Rotondaro
- Department of Chemistry, Boston University, Boston, MA 02215, USA. and Photonics Center, Boston University, Boston, MA 02215, USA
| | - Parth P Shah
- Department of Chemistry, Boston University, Boston, MA 02215, USA. and Photonics Center, Boston University, Boston, MA 02215, USA
| | - Aritra Mandal
- Department of Chemistry, University of Colorado, Boulder, CO 80309, USA
| | - Shyamsunder Erramilli
- Photonics Center, Boston University, Boston, MA 02215, USA and Department of Physics, Boston University, Boston, MA 02215, USA
| | - L D Ziegler
- Department of Chemistry, Boston University, Boston, MA 02215, USA. and Photonics Center, Boston University, Boston, MA 02215, USA
| |
Collapse
|
9
|
Shi SJ, Pan YH, Wang SF, Dai ZW, Gu L, Wu QY. Aluminosilicate Nanotubes Embedded Polyamide Thin Film Nanocomposite Forward Osmosis Membranes with Simultaneous Enhancement of Water Permeability and Selectivity. Polymers (Basel) 2019; 11:E879. [PMID: 31091763 PMCID: PMC6572521 DOI: 10.3390/polym11050879] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 05/05/2019] [Accepted: 05/08/2019] [Indexed: 11/16/2022] Open
Abstract
Nanocomposite membranes are strongly desired to break a trade-off between permeability and selectivity. This work reports new thin film nanocomposite (TFN) forward osmosis (FO) membranes by embedding aluminosilicate nanotubes (ANTs) into a polyamide (PA) rejection layer. The surface morphology and structure of the TFN FO membranes were carefully characterized by FTIR, XPS, FESEM and AFM. The ANTs incorporated PA rejection layers exhibited many open and broad "leaf-like" folds with "ridge-and-valley" structures, high surface roughness and relatively low cross-linking degree. Compared with thin film composite (TFC) membrane without ANTs, the TFN membrane with only 0.2 w/v% ANTs loading presented significantly improved FO water permeability, selectivity and reduced structural parameters. This promising performance can be mainly contributed to the special ANTs embedded PA rejection layer, where water molecules preferentially transport through the nanochannels of ANTs. Molecular dynamic simulation further proved that water molecules have much larger flux through the nanotubes of ANTs than sodium and chloride ions, which are attributed to the intrinsic hydrophilicity of ANTs and low external force for water transport. This work shows that these TFN FO membranes with ANTs decorated PA layer are promising in desalination applications due to their simultaneously enhanced permeability and selectivity.
Collapse
Affiliation(s)
- She-Ji Shi
- Faculty of Materials Science and Chemical Engineering, Ningbo University, Ningbo 315211, China.
| | - Ye-Han Pan
- Faculty of Materials Science and Chemical Engineering, Ningbo University, Ningbo 315211, China.
| | - Shao-Fei Wang
- Faculty of Materials Science and Chemical Engineering, Ningbo University, Ningbo 315211, China.
| | - Zheng-Wei Dai
- College of Material and Textile Engineering, Jiaxing University, Jiaxing 314001, China.
| | - Lin Gu
- Key Laboratory of Marine Materials and Related Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences; Ningbo 315201; China.
| | - Qing-Yun Wu
- Faculty of Materials Science and Chemical Engineering, Ningbo University, Ningbo 315211, China.
| |
Collapse
|
10
|
Nichele J, de Oliveira AB, Alves LSDB, Borges I. Accurate calculation of near-critical heat capacities C P and C V of argon using molecular dynamics. J Mol Liq 2017. [DOI: 10.1016/j.molliq.2017.03.120] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
11
|
Understanding the effect of biomass-to-solvent ratio on macroalgae (Saccharina japonica) liquefaction in supercritical ethanol. J Supercrit Fluids 2017. [DOI: 10.1016/j.supflu.2016.10.013] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
12
|
Asiaee A, Benjamin KM. Molecular simulation of CO chemisorption on Co(0001) in presence of supercritical fluid solvent: A potential of mean force study. J Chem Phys 2016; 145:084506. [DOI: 10.1063/1.4953171] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
13
|
Liu Z, Fang Z, Muroya Y, Fu H, Yan Y, Katsumura Y, Lin M. Local density augmentation of supercritical water probed by 4,4′-bpyH radical: A pulse radiolysis study. Chem Phys Lett 2016. [DOI: 10.1016/j.cplett.2016.05.059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
14
|
A Review of Laboratory-Scale Research on Upgrading Heavy Oil in Supercritical Water. ENERGIES 2015. [DOI: 10.3390/en8088962] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
15
|
Mukai SA, Koyama T, Tsujii K, Deguchi S. Anomalous long-range repulsion between silica surfaces induced by density inhomogeneities in supercritical ethanol. SOFT MATTER 2014; 10:6645-6650. [PMID: 25037983 DOI: 10.1039/c4sm00787e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Anomalous long-range repulsion, extending over several micrometres, emerged between silica surfaces around the ridge of density fluctuations in supercritical ethanol at temperatures and pressures near the gas/liquid critical point (T(c) = 241 °C, P(c) = 6.14 MPa). Analysis shows that augmentation of ethanol density around silica surfaces in the presence of density fluctuations facilitates dissociation of silanol groups, leading to long-range electrostatic repulsion in the nonpolar medium.
Collapse
Affiliation(s)
- Sada-atsu Mukai
- Research and Development Center for Marine Biosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka 237-0061, Japan.
| | | | | | | |
Collapse
|
16
|
Trukhan SN, Yudanov VF, Mart’yanov ON. The effect of clustering of VO2+ ions in sub- and supercritical water. An in situ EPR study. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B 2014. [DOI: 10.1134/s1990793113080113] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
17
|
Idrissi A, Vyalov I, Georgi N, Kiselev M. On the characterization of inhomogeneity of the density distribution in supercritical fluids via molecular dynamics simulation and data mining analysis. J Phys Chem B 2013; 117:12184-8. [PMID: 24015951 DOI: 10.1021/jp404873a] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
We combined molecular dynamics simulation and DBSCAN algorithm (Density Based Spatial Clustering of Application with Noise) in order to characterize the local density inhomogeneity distribution in supercritical fluids. The DBSCAN is an algorithm that is capable of finding arbitrarily shaped density domains, where domains are defined as dense regions separated by low-density regions. The inhomogeneity of density domain distributions of Ar system in sub- and supercritical conditions along the 50 bar isobar is associated with the occurrence of a maximum in the fluctuation of number of particles of the density domains. This maximum coincides with the temperature, Tα, at which the thermal expansion occurs. Furthermore, using Voronoi polyhedral analysis, we characterized the structure of the density domains. The results show that with increasing temperature below Tα, the increase of the inhomogeneity is mainly associated with the density fluctuation of the border particles of the density domains, while with increasing temperature above Tα, the decrease of the inhomogeneity is associated with the core particles.
Collapse
Affiliation(s)
- Abdenacer Idrissi
- Université de Lille 1 Sciences et Technologies , LASIR UMR8516 59655, Villeneuve d'Ascq Cedex, France
| | | | | | | |
Collapse
|
18
|
Yadav VK, Chandra A. Dynamics of supercritical methanol of varying density from first principles simulations: Hydrogen bond fluctuations, vibrational spectral diffusion, and orientational relaxation. J Chem Phys 2013; 138:224501. [DOI: 10.1063/1.4808034] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
19
|
Park S, Lee JH, Yoo KP, Shin MS. A semi-empirical molecular clustering based lattice model near to and far from the critical region. J IND ENG CHEM 2012. [DOI: 10.1016/j.jiec.2011.11.136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
20
|
|
21
|
Trukhan S, Yudanov V, Martyanov O. Electron spin resonance of VO2+ radical-ion in sub- and supercritical water. J Supercrit Fluids 2011. [DOI: 10.1016/j.supflu.2011.04.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
|
22
|
Lin M, Archirel P, Van-Oanh NT, Muroya Y, Fu H, Yan Y, Nagaishi R, Kumagai Y, Katsumura Y, Mostafavi M. Temperature Dependent Absorption Spectra of Br−, Br2•−, and Br3− in Aqueous Solutions. J Phys Chem A 2011; 115:4241-7. [DOI: 10.1021/jp1123103] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Mingzhang Lin
- Nuclear Engineering and Science Directorate, Japan Atomic Energy Agency, 2-4 Shirakata shirane, Tokaimura, Nakagun, Ibaraki 319-1195, Japan
| | - Pierre Archirel
- Laboratoire de Chimie Physique/ELYSE, Université Paris-Sud 11, UMR 8000, Bâtiment 349, Orsay, 91405 France
| | - Nguyen Thi Van-Oanh
- Laboratoire de Chimie Physique/ELYSE, Université Paris-Sud 11, UMR 8000, Bâtiment 349, Orsay, 91405 France
| | | | | | | | - Ryuji Nagaishi
- Nuclear Engineering and Science Directorate, Japan Atomic Energy Agency, 2-4 Shirakata shirane, Tokaimura, Nakagun, Ibaraki 319-1195, Japan
| | - Yuta Kumagai
- Nuclear Engineering and Science Directorate, Japan Atomic Energy Agency, 2-4 Shirakata shirane, Tokaimura, Nakagun, Ibaraki 319-1195, Japan
| | | | - Mehran Mostafavi
- Laboratoire de Chimie Physique/ELYSE, Université Paris-Sud 11, UMR 8000, Bâtiment 349, Orsay, 91405 France
| |
Collapse
|
23
|
A study of solvation of benzaldehyde and cinnamaldehyde in CO2 by molecular dynamics simulation. Chem Phys Lett 2010. [DOI: 10.1016/j.cplett.2010.04.046] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
24
|
Ghosh SK, Tsujii K. Unique diffusion behavior observed in supercritical ethanol. J Chem Phys 2010; 132:144503. [DOI: 10.1063/1.3373404] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
|
25
|
Lee JH, Han GS, Breitholz A, Yoo KP, Shin MS, Kim H. An empirical near-critical correction for a quasi-chemical nonrandom lattice fluid. KOREAN J CHEM ENG 2010. [DOI: 10.1007/s11814-009-0350-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
26
|
Kruse A, Dinjus E. Influence of Salts During Hydrothermal Biomass Gasification: The Role of the Catalysed Water-Gas Shift Reaction. ACTA ACUST UNITED AC 2009. [DOI: 10.1524/zpch.219.3.341.59177] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
Near-critical and supercritical water is an unusual reaction medium with extraordinary properties, varying with temperature and density. This opens the opportunity for new reactions and new technical processes. In the studies of synthesis reactions, total oxidation and biomass gasification interesting effects of salts are observed. These effects are assumed to be caused by complex formation, acidity/basicity or the presence of active hydrogen due to the water-gas shift reaction. The water-gas shift reaction is catalysed by salts and lead to the formation of hydrogen, which might react with other compounds.
This article focuses on the salt effects during hydrogen production by biomass gasification in supercritical water. This is a very interesting process to make use of “wet biomass”, which is up to now not applied in a technical process. Here salts influenced the main reactions pathways. Possible reasons are discussed.
Collapse
|
27
|
Skarmoutsos I, Guardia E. Local Structural Effects and Related Dynamics in Supercritical Ethanol. 1. Mechanisms of Local Density Reorganization and Residence Dynamics. J Phys Chem B 2009; 113:8887-97. [DOI: 10.1021/jp901020x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Ioannis Skarmoutsos
- Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, B4−B5 Campus Nord UPC, 08034 Barcelona, Catalonia, Spain
| | - Elvira Guardia
- Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, B4−B5 Campus Nord UPC, 08034 Barcelona, Catalonia, Spain
| |
Collapse
|
28
|
Skarmoutsos I, Dellis D, Samios J. The Effect of Intermolecular Interactions on Local Density Inhomogeneities and Related Dynamics in Pure Supercritical Fluids. A Comparative Molecular Dynamics Simulation Study. J Phys Chem B 2009; 113:2783-93. [DOI: 10.1021/jp809271n] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Ioannis Skarmoutsos
- Department of Chemistry, Laboratory of Physical Chemistry, University of Athens, Panepistimiopolis 157-71, Athens, Greece
| | - Dimitris Dellis
- Department of Chemistry, Laboratory of Physical Chemistry, University of Athens, Panepistimiopolis 157-71, Athens, Greece
| | - Jannis Samios
- Department of Chemistry, Laboratory of Physical Chemistry, University of Athens, Panepistimiopolis 157-71, Athens, Greece
| |
Collapse
|
29
|
|
30
|
Peng J, Castonguay TC, Coker DF, Ziegler LD. Ultrafast H[sub 2] and D[sub 2] rotational Raman responses in near critical CO[sub 2]: An experimental and theoretical study of anisotropic solvation dynamics. J Chem Phys 2009; 131:054501. [DOI: 10.1063/1.3186732] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
|
31
|
Jay-Gerin JP, Lin M, Katsumura Y, He H, Muroya Y, Meesungnoen J. Effect of water density on the absorption maximum of hydrated electrons in sub- and supercritical water up to 400 °C. J Chem Phys 2008; 129:114511. [DOI: 10.1063/1.2978955] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
|
32
|
Hou M, Zhang X, Han B, Song J, Liu G, Zhang Z, Zhang J. New topic of supercritical fluids: Local activity coefficients of supercritical solvent and cosolvent around solute. J Chem Phys 2008; 128:104510. [DOI: 10.1063/1.2838181] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
|
33
|
Husowitz B, Talanquer V. Solvent density inhomogeneities and solvation free energies in supercritical diatomic fluids: a density functional approach. J Chem Phys 2007; 126:054508. [PMID: 17302486 DOI: 10.1063/1.2432327] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Density functional theory is used to explore the solvation properties of a spherical solute immersed in a supercritical diatomic fluid. The solute is modeled as a hard core Yukawa particle surrounded by a diatomic Lennard-Jones fluid represented by two fused tangent spheres using an interaction site approximation. The authors' approach is particularly suitable for thoroughly exploring the effect of different interaction parameters, such as solute-solvent interaction strength and range, solvent-solvent long-range interactions, and particle size, on the local solvent structure and the solvation free energy under supercritical conditions. Their results indicate that the behavior of the local coordination number in homonuclear diatomic fluids follows trends similar to those reported in previous studies for monatomic fluids. The local density augmentation is particularly sensitive to changes in solute size and is affected to a lesser degree by variations in the solute-solvent interaction strength and range. The associated solvation free energies exhibit a nonmonotonous behavior as a function of density for systems with weak solute-solvent interactions. The authors' results suggest that solute-solvent interaction anisotropies have a major influence on the nature and extent of local solvent density inhomogeneities and on the value of the solvation free energies in supercritical solutions of heteronuclear molecules.
Collapse
Affiliation(s)
- B Husowitz
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA
| | | |
Collapse
|
34
|
Molecular-Based Modeling of Water and Aqueous Solutions at Supercritical Conditions. ADVANCES IN CHEMICAL PHYSICS 2007. [DOI: 10.1002/9780470141687.ch3] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/08/2023]
|
35
|
Skarmoutsos I, Samios J. Local density augmentation and dynamic properties of hydrogen-and non-hydrogen-bonded supercritical fluids: A molecular dynamics study. J Chem Phys 2007; 126:044503. [PMID: 17286483 DOI: 10.1063/1.2431370] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The local density inhomogeneities in neat supercritical fluids were investigated via canonical molecular dynamics simulations. The selected systems under investigation were the polar and hydrogen-bonded fluid methanol as well as the quadrupolar non-hydrogen-bonded carbon dioxide one. Effective local densities, local density augmentation, and enhancement factors were calculated at state points along an isotherm close to the critical temperature of each system (T(r)=1.03). The results obtained reveal strong influence of the polarity and hydrogen bonding upon the intensity of the local density augmentation. It is found that this effect is sufficiently larger in the case of the polar and associated methanol in comparison to those predicted for carbon dioxide. For both fluids the local density augmentation values are maximized in the bulk density region near 0.7rho(c), a result that is in agreement with experiment. In addition, the local density dynamics of each fluid were investigated in terms of the appropriate time correlation functions. The behavior of these functions reveals that the bulk density dependence of the local density reorganization times is very sensitive to the specific intermolecular interactions and to the size of the local region. Also, the estimated local density reorganization time as a function of bulk density of each fluid was further analyzed and successfully related to two different time-scale relaxation mechanisms. Finally, the results obtained indicate a possible relationship between the single-molecule reorientational dynamics and the local density reorganization ones.
Collapse
Affiliation(s)
- Ioannis Skarmoutsos
- Laboratory of Physical Chemistry, Department of Chemistry, University of Athens, Panepistimiopolis 157-71, Athens, Greece
| | | |
Collapse
|
36
|
|
37
|
Ghosh SK, Alargova RG, Deguchi S, Tsujii K. Dispersion Stability of Colloids in Sub- and Supercritical Water. J Phys Chem B 2006; 110:25901-7. [PMID: 17181238 DOI: 10.1021/jp0656328] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dispersion stability of colloids has been investigated in sub- and supercritical water by measuring the hydrodynamic diffusion coefficients of the particles by means of dynamic light scattering. It is interestingly found that coagulation of the colloids in sub- and supercritical water is a universal phenomenon irrespective of the material of the colloids. Highly charged colloids were found to be more stable in water against high temperature. Numerical analysis reveals that the stability of the colloids at elevated temperature and pressure is primarily governed by the temperature dependence of the dielectric constant of the medium. The effect of the temperature dependence of the ion product of water (pKw) was found to be very little. Surface charge density and Stern potential may change with respect to temperature due to the readjustment of the ion concentration in the diffuse layer through the enhanced ion product and reduced dielectric constant of water. These are the secondary causes of the particle coagulations in sub- and supercritical water.
Collapse
Affiliation(s)
- Swapan K Ghosh
- Extremobiosphere Research Center, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka 237-0061, Japan.
| | | | | | | |
Collapse
|
38
|
Local density augmentation of excited 1-(dimethylamino)naphthalene in supercritical water. J Supercrit Fluids 2006. [DOI: 10.1016/j.supflu.2006.02.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
39
|
Shukla CL, Hallett JP, Popov AV, Hernandez R, Liotta CL, Eckert CA. Molecular Dynamics Simulation of the Cybotactic Region in Gas-Expanded Methanol−Carbon Dioxide and Acetone−Carbon Dioxide Mixtures. J Phys Chem B 2006; 110:24101-11. [PMID: 17125382 DOI: 10.1021/jp0648947] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Local solvation and transport effects in gas-expanded liquids (GXLs) are reported based on molecular simulation. GXLs were found to exhibit local density enhancements similar to those seen in supercritical fluids, although less dramatic. This approach was used as an alternative to a multiphase atomistic model for these mixtures by utilizing experimental results to describe the necessary fixed conditions for a locally (quasi-) stable molecular dynamics model of the (single) GXL phase. The local anisotropic pair correlation function, orientational correlation functions, and diffusion rates are reported for two systems: CO2-expanded methanol and CO2-expanded acetone at 298 K and pressures up to 6 MPa.
Collapse
Affiliation(s)
- Charu L Shukla
- School of Chemical and Biomolecular Engineering, School of Chemistry and Biochemistry, Specialty Separations Center, Center for Computational and Molecular Science and Technology, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | | | | | | | | | | |
Collapse
|
40
|
Skarmoutsos I, Samios J. Local Density Inhomogeneities and Dynamics in Supercritical Water: A Molecular Dynamics Simulation Approach. J Phys Chem B 2006; 110:21931-7. [PMID: 17064161 DOI: 10.1021/jp060955p] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Molecular dynamics atomistic simulations in the canonical ensemble (NVT-MD) have been used to investigate the "Local Density Inhomogeneities and their Dynamics" in pure supercritical water. The simulations were carried out along a near-critical isotherm (Tr = T/Tc = 1.03) and for a wide range of densities below and above the critical one (0.2 rho(c) - 2.0 rho(c)). The results obtained reveal the existence of significant local density augmentation effects, which are found to be sufficiently larger in comparison to those reported for nonassociated fluids. The time evolution of the local density distribution around each molecule was studied in terms of the appropriate time correlation functions C(Delta)rhol(t). It is found that the shape of these functions changes significantly by increasing the density of the fluid. Finally, the local density reorganization times for the first and second coordination shell derived from these correlations exhibit a decreasing behavior by increasing the density of the system, signifying the density effect upon the dynamics of the local environment around each molecule.
Collapse
Affiliation(s)
- Ioannis Skarmoutsos
- Department of Chemistry, Laboratory of Physical Chemistry, University of Athens, Panepistimiopolis 157-71, Athens, Greece
| | | |
Collapse
|
41
|
Hallett JP, Kitchens CL, Hernandez R, Liotta CL, Eckert CA. Probing the cybotactic region in gas-expanded liquids (GXLs). Acc Chem Res 2006; 39:531-8. [PMID: 16906749 DOI: 10.1021/ar0501424] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Gas-expanded liquids (GXLs) are a new and benign class of liquid solvents, which may offer many advantages for separations, reactions, and advanced materials. GXLs are intermediate in properties between normal liquids and supercritical fluids, both in solvating power and in transport properties. Other advantages include benign nature, low operating pressures, and highly tunable properties by simple pressure variations. The chemical community has only just begun to exploit the advantages of these GXLs for industrial applications. This Account focuses on the synergism of experimental techniques with theoretical modeling resulting in a powerful combination for exploring chemical structure and transport in the cybotactic region of GXLs (at the nanometer lengthscale).
Collapse
Affiliation(s)
- Jason P Hallett
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | | | | | | | | |
Collapse
|
42
|
Humayun R, Tomasko DL. High-resolution adsorption isotherms of supercritical carbon dioxide on activated carbon. AIChE J 2006. [DOI: 10.1002/aic.690461017] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
43
|
Minami K, Mizuta M, Suzuki M, Aizawa T, Arai K. Determination of Kamlet–Taft solvent parameters π* of high pressure and supercritical water by the UV-Vis absorption spectral shift of 4-nitroanisole. Phys Chem Chem Phys 2006; 8:2257-64. [PMID: 16688308 DOI: 10.1039/b516862g] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Kamlet-Taft solvent parameters, pi*, of high pressure and supercritical water were determined from 16-420 degrees C based on solvatochromic measurements of 4-nitroanisole. For the measurements, an optical cell that could be used at high temperatures and pressures was developed with the specification of minimal dead space. The low dead space cell allowed us to measure the absorption spectra of 4-nitroanisole at high temperature conditions before appreciable decomposition occurred. The behavior of pi* in terms of water density (pi* = 1.77rho- 0.71) was found to be linear, except in the near critical region, in which deviations were observed that could be attributed to local density augmentation. Excess density, which was defined as the difference between local density and bulk density, showed a maximum near the critical density of water. The frequencies of UV-Vis spectra of 4-(dimethylamino)benzonitrile and N,N-dimethyl-4-nitroaniline were correlated with pi* based on a linear solvation energy relationship (LSER) theory. Local density augmentation around 4-nitroanisole and that around 4-(dimethylamino)benzonitrile were similar but the augmentation observed around N,N-dimethyl-4-nitroaniline was larger.
Collapse
Affiliation(s)
- Kimitaka Minami
- National Institute of Advanced Industrial Science and Technology, Research Center for Compact Chemical Process, Nigatake, Miyagino-ku, Sendai, Japan.
| | | | | | | | | |
Collapse
|
44
|
Zhang Y, Yang J, Yu YX, Li YG. Structural and hydrogen bond analysis for supercritical ethanol: A molecular simulation study. J Supercrit Fluids 2005. [DOI: 10.1016/j.supflu.2005.04.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
45
|
Wang B, Han B, Jiang T, Zhang Z, Xie Y, Li W, Wu W. Enhancing the Rate of the Diels−Alder Reaction Using CO2 + Ethanol and CO2 + n-Hexane Mixed Solvents of Different Phase Regions. J Phys Chem B 2005; 109:24203-10. [PMID: 16375413 DOI: 10.1021/jp0553838] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The reaction rate of the Diels-Alder reaction between N-ethylmaleimide and 9-hydroxymethylanthrance in CO2 + ethanol and CO2 + hexane mixed solvents of different compositions were determined by in situ UV/vis spectroscopy at 318.15 K and different pressures. The density of the mixed solvents at different pressures was also determined and the isothermal compressibility was calculated using the density data. The activation volume of the reaction was calculated based on the dependence of rate constant (kc) on pressure. It was demonstrated that the kc was very sensitive to the pressure in the mixed solvents near the critical region and the kc increased dramatically as pressure approached dew points, critical point, and bubble points of the mixed solvents. However, the kc in the mixed solvents outside the critical region or in pure CO2 was not sensitive to pressure. At suitable conditions, kc could be 40 times larger than that in acetonitrile. The activation volume of the reaction was nearly independent of pressure as the pressure was much higher than the phase separation pressure of the mixed solvents, while it increased considerably as pressure approached the bubble points, critical point, and dew points from high pressure. The clustering of the solvent molecules with the reactants and the activated complex in the reaction systems near the phase boundary in the critical region may be the main reason for the interesting phenomena observed. This work also shows that, using pure CO2 as the solvent, the reaction cannot be carried out in the critical region of the solvent due to the limitations of the reactants, while it can be conducted in the critical region of mixed solvents of suitable compositions, where the solvents are highly compressible and the reaction rate can be tuned effectively by pressure.
Collapse
Affiliation(s)
- Bo Wang
- Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China
| | | | | | | | | | | | | |
Collapse
|
46
|
Hrnjez BJ, Sultan ST, Natanov GR, Kastner DB, Rosman MR. Prediction of Supercritical Ethane Bulk Solvent Densities for Pyrazine Solvation Shell Average Occupancy by 1, 2, 3, and 4 Ethanes: Combined Experimental and ab Initio Approach. J Phys Chem A 2005; 109:10222-31. [PMID: 16833315 DOI: 10.1021/jp054150d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We introduce a method that addresses the elusive local density at the solute in the highly compressible regime of a supercritical fluid. Experimentally, the red shift of the pyrazine n-pi electronic transition was measured at infinite dilution in supercritical ethane as a function of pressure from 0 to about 3000 psia at two temperatures, one close (35.0 degrees C) to the critical temperature and the other remote (55.0 degrees C). Computationally, stationary points were located on the potential surfaces for pyrazine and one, two, three, and four ethanes at the MP2/6-311++G(d,p) level. The vertical n-pi ((1)B(3u)) transition energies were computed for each of these geometries with a TDDFT/B3LYP/6-311++G(d,p) method. The combination of experiment and computation allows prediction of supercritical ethane bulk densities at which the pyrazine primary solvation shell contains an average of one, two, three, and four ethane molecules. These density predictions were achieved by graphical superposition of calculated shifts on the experimental shift versus density curves for 35.0 and 55.0 degrees C. Predicted densities are 0.0635, 0.0875, and 0.0915 g cm(-3) for average pyrazine primary solvation shell occupancy by one, two, and three ethanes at both 35.0 and 55.0 degrees C. Predicted densities are 0.129 and 0.150 g cm(-3) for occupancy by four ethanes at 35.0 and 55.0 degrees C, respectively. An alternative approach, designed to "average out" geometry specific shifts, is based on the relationship Deltanu = -23.9n cm(-1), where n = ethane number. Graphical treatment gives alternative predicted densities of 0.0490, 0.0844, and 0.120 g cm(-3) for average pyrazine primary solvation shell occupancy by one, two, and three ethanes at both 35.0 and 55.0 degrees C, and densities of 0.148 and 0.174 g cm(-3) for occupancy by four ethanes at 35.0 and 55.0 degrees C, respectively.
Collapse
Affiliation(s)
- Bruce J Hrnjez
- Department of Chemistry, Yeshiva University, New York, New York 10033, USA.
| | | | | | | | | |
Collapse
|
47
|
Idrissi A, Longelin S, Damay P, Leclercq F. Low-frequency Raman spectra of sub- and supercritical CO2: qualitative analysis of the diffusion coefficient behavior. J Chem Phys 2005; 123:94501. [PMID: 16164347 DOI: 10.1063/1.1992476] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
We report the results of the low-frequency Raman experiments on CO(2) which were carried out in a wide density range, along the liquid-gas coexistence curve in a temperature range of 293-303 K, and on the critical isochore of 94.4 cm(3) mol(-1) in a temperature range of 304-315 K. In our approach, the qualitative behavior of the diffusion coefficient D is predicted, assuming the following: first, that the low-frequency Raman spectra can be interpreted in terms of the translation rotation motions; second, that the random force could be replaced by the total force to calculate the friction coefficient; and finally, that the Einstein frequency is associated with the position of the maximum of the low-frequency Raman spectrum. The results show that the diffusion coefficient increases along the coexistence curve, and its values are almost constant on the critical isochore. The predicted values reproduce qualitatively those obtained by other techniques. The values of D were also calculated by molecular-dynamics simulation and they qualitatively reproduce the behavior of D.
Collapse
Affiliation(s)
- A Idrissi
- Centre d'Etudes et de Recherches Lasers et Applications, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France.
| | | | | | | |
Collapse
|
48
|
Chen J, Shen D, Wu W, Han B, Wang B, Sun D. Solvatochromic behavior of phenol blue in CO2+ethanol and CO2+n-pentane mixtures in the critical region and local composition enhancement. J Chem Phys 2005; 122:204508. [PMID: 15945753 DOI: 10.1063/1.1917747] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The UV-Vis spectra of probe phenol blue in CO(2)+ethanol and CO(2)+n-pentane binary mixtures were studied at 308.15 K and different pressures. The experiments were conducted in both supercritical region and subcritical region of the mixtures by changing the compositions of the mixed solvents. On the basis of the experimental results the local compositions of the solvents about phenol blue were estimated by neglecting the size difference of CO(2) and the cosolvents. Then the local composition data were corrected by a method proposed in this work, which is mainly based on Lennard-Jones sphere model. It was demonstrated that the local mole fraction of the cosolvents is higher than that in the bulk solution at all the experimental conditions. In the near critical region of the mixed solvents the local composition enhancement, defined as the ratio of cosolvent mole fraction about the solute to that in the bulk solution, increased significantly as pressure approached the phase boundary from high pressure. The local composition enhancement was not considerable as pressure was much higher than the critical pressure. In addition, in subcritical region the degree of composition enhancement was much smaller and was not sensitive to pressure in the entire pressure range as the concentration of the cosolvents in the mixed solvents was much higher than the concentration at the critical point of the mixtures.
Collapse
Affiliation(s)
- Jiawei Chen
- The Center for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China
| | | | | | | | | | | |
Collapse
|
49
|
Abbott AP, Corr S, Durling NE, Hope EG. Pressure Effects on Friedel-Crafts Alkylation Reactions in Supercritical Difluoromethane. Chemphyschem 2005; 6:466-72. [PMID: 15799471 DOI: 10.1002/cphc.200400363] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Dielectrometry is used as a novel technique for following the rate of a Friedel-Crafts alkylation reaction in supercritical (sc) difluoromethane. Although the process was not optimized, good product yields were obtained and reaction rates were found to be larger than in CO2 at comparable conditions. The reaction order is determined using the initial rate method and the reaction is shown to be first-order with respect to both anisole and t-butyl chloride. The reaction rate constant is unaffected by pressures above 120 bar but close to the critical pressure the value decreases with increasing pressure. It is also shown that the product distribution for the alkylation of anisole shows significant pressure dependence with substitution at the ortho-position being favored at lower pressures, which is ascribed to hydrogen bonding. This pressure dependency is not observed in sc CO2 or using toluene as a substrate, which supports the idea that hydrogen bonding may be important in the reaction mechanism. The effect of the different reagents and temperature on the rate of the alkylation reaction was also determined.
Collapse
Affiliation(s)
- Andrew P Abbott
- Chemistry Department, University of Leicester, Leicester LE1 7RH, UK.
| | | | | | | |
Collapse
|
50
|
Saitow KI, Sasaki J. Attractive and repulsive interactions among methanol molecules in supercritical state investigated by Raman spectroscopy and perturbed hard-sphere theory. J Chem Phys 2005; 122:104502. [PMID: 15836327 DOI: 10.1063/1.1858442] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The short-range structure of supercritical methanol (CH(3)OH) is investigated by measuring the spontaneous Raman spectra of the C-O stretching mode. The spectra are obtained at a reduced temperature, T(r)=T/T(c)=1.02 (522.9 K), which permits the neat fluid to be studied isothermally as a function of density. As the density increases, the spectral peaks shift toward the lower energy side and the spectra broaden. In the supercritical region, the amount of shifting shows nonlinear density dependence and the width becomes anomalously large. We use the perturbed hard-sphere model to analyze these density dependencies along the vibrational coordinate. The amount of shifting is decomposed into attractive and repulsive components, and the changes in attractive and repulsive energies are evaluated as functions of density and packing fraction, both of which are continuously varied by a factor of 120. Here we show that the shift amount consists principally of the attractive component at all densities, since the attractive energy is about eight times the repulsive energy. The density dependence of the widths is analyzed by calculating homogeneous and inhomogeneous widths as a function of density. The results show that, although vibrational dephasing and density inhomogeneity contribute similarly to the width at low and middle densities, at high density the main contributor turns out to be the vibrational dephasing. We estimate the local density enhancements of supercritical CH(3)OH as function of bulk density by two methods. The results of these analyses show common features, and both the estimated local density enhancements of CH(3)OH are considerably larger than the local density enhancements of simple fluids, i.e., those having nonhydrogen bonding. It is revealed that the local density of supercritical CH(3)OH is 40%-60% greater than the local densities of the simple fluids. We also estimate the local density fluctuation using the obtained values of attractive shift, inhomogeneous width, and local density. The density fluctuation in the vicinity of a vibrating molecule is compared to the fluctuation of bulk density, which is obtained from the thermodynamic calculation.
Collapse
Affiliation(s)
- Ken-ichi Saitow
- Department of Physics, Faculty of Science, Chiba University, Yayoi, Inage, Chiba 263-8522, Japan.
| | | |
Collapse
|