Decomposition of Mercuric Chloride and Application to Combustion Flue Gases

2004 ◽  
Vol 1 (3) ◽  
pp. 166 ◽  
Author(s):  
Jennifer Wilcox ◽  
Paul Blowers
Keyword(s):  
Mercuric Chloride ◽  
Rate Constants ◽  
Atmospheric Mercury ◽  
Water Soluble ◽  
Flue Gases ◽  
Basis Set ◽  
B3lyp Level ◽  
Combustion Modelling ◽  
Experimental Values ◽  
Relativistic Pseudopotentials

Environmental Context. The toxicity of the volatile metal mercury is well known; this Hg0 form accounts for about 99% of atmospheric mercury and the remainder the water-soluble oxidized (Hg+, Hg2+) form. The release of mercury from the atmosphere is measurable by a drop in the Hg0 levels, but to establish realistic scientific and regulatory standpoints the rate in which Hg0 converts to the oxidized forms needs to be understood. Conversely, from an industrial standpoint, understanding the rate at which the oxidized forms convert to Hg0 allows for better waste-scrubbing processes. Abstract. Theoretical rate constants and activation energies are predicted for the decomposition of mercuric chloride through the use of relativistic pseudopotentials for mercury at the B3LYP level of theory. The method and basis set combinations are validated through a comparison of theoretically determined geometries, frequencies, and reaction enthalpies to experimental values found in the literature. In addition, the theoretically predicted rate constants are compared to rate constants that have been predicted through combustion modelling of this reaction.

DFT Benchmark Study of the O--O Bond Dissociation Energy in Peroxides Validated with High-Level Ab-Initio Calculations

2019 ◽  
Author(s):  
Danilo Carmona ◽  
Pablo Jaque ◽  
Esteban Vöhringer-Martinez
Keyword(s):  
Reference Value ◽  
Basis Set ◽  
Basis Sets ◽  
Mean Deviation ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
The Mean ◽  
Experimental Values ◽  
High Level ◽  
Almost All

<div><div><div><p>Peroxides play a central role in many chemical and biological pro- cesses such as the Fenton reaction. The relevance of these compounds lies in the low stability of the O–O bond which upon dissociation results in radical species able to initiate various chemical or biological processes. In this work, a set of 64 DFT functional-basis set combinations has been validated in terms of their capability to describe bond dissociation energies (BDE) for the O–O bond in a database of 14 ROOH peroxides for which experimental values ofBDE are available. Moreover, the electronic contributions to the BDE were obtained for four of the peroxides and the anion H2O2− at the CBS limit at CCSD(T) level with Dunning’s basis sets up to triple–ζ quality provid- ing a reference value for the hydrogen peroxide anion as a model. Almost all the functionals considered here yielded mean absolute deviations around 5.0 kcal mol−1. The smallest values were observed for the ωB97 family and the Minnesota M11 functional with a marked basis set dependence. Despite the mean deviation, order relations among BDE experimental values of peroxides were also considered. The ωB97 family was able to reproduce the relations correctly whereas other functionals presented a marked dependence on the chemical nature of the R group. Interestingly, M11 functional did not show a very good agreement with the established order despite its good performance in the mean error. The obtained results support the use of similar validation strategies for proper prediction of BDE or other molecular properties by DF Tmethods in subsequent related studies.</p></div></div></div>

scholarly journals Crystal structure of a new monoclinic polymorph ofN-(4-methylphenyl)-3-nitropyridin-2-amine

2014 ◽  
Vol 70 (8) ◽  
pp. 58-61
Author(s):  
Aina Mardia Akhmad Aznan ◽  
Zanariah Abdullah ◽  
Vannajan Sanghiran Lee ◽  
Edward R. T. Tiekink
Keyword(s):  
Three Dimensional ◽  
Basis Set ◽  
Dihedral Angles ◽  
Asymmetric Unit ◽  
Acta Cryst ◽  
Common Features ◽  
Compound C ◽  
B3lyp Level ◽  
The Common ◽  
Independent Molecules

The title compound, C12H11N3O2, is a second monoclinic polymorph (P21, withZ′ = 4) of the previously reported monoclinic (P21/c, withZ′ = 2) form [Akhmad Aznanet al.(2010).Acta Cryst.E66, o2400]. Four independent molecules comprise the asymmetric unit, which have the common features of asyndisposition of the pyridine N atom and the toluene ring, and an intramolecular amine–nitro N—H...O hydrogen bond. The differences between molecules relate to the dihedral angles between the rings which range from 2.92 (19) to 26.24 (19)°. The geometry-optimized structure [B3LYP level of theory and 6–311 g+(d,p) basis set] has the same features except that the entire molecule is planar. In the crystal, the three-dimensional architecture is consolidated by a combination of C—H...O, C—H...π, nitro-N—O...π and π–π interactions [inter-centroid distances = 3.649 (2)–3.916 (2) Å].

scholarly journals A new mechanism for atmospheric mercury redox chemistry: Implications for the global mercury budget

2017 ◽  
Author(s):  
Hannah M. Horowitz ◽  
Daniel J. Jacob ◽  
Yanxu Zhang ◽  
Theodore S. Dibble ◽  
Franz Slemr ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Wet Deposition ◽  
General Circulation ◽  
Gulf Coast ◽  
Circulation Model ◽  
Redox Chemistry ◽  
Ocean General Circulation Model ◽  
Atmospheric Mercury ◽  
Water Soluble ◽  
Second Stage

Abstract. Mercury (Hg) is emitted to the atmosphere mainly as volatile elemental Hg0. Oxidation to water-soluble HgII controls Hg deposition to ecosystems. Here we implement a new mechanism for atmospheric Hg0 / HgII redox chemistry in the GEOS-Chem global model and examine the implications for the global atmospheric Hg budget and deposition patterns. Our simulation includes a new coupling of GEOS-Chem to an ocean general circulation model (MITgcm), enabling a global 3-D representation of atmosphere-ocean Hg0 / HgII cycling. We find that atomic bromine (Br) of marine organobromine origin is the main atmospheric Hg0 oxidant, and that second-stage HgBr oxidation is mainly by the NO2 and HO2 radicals. The resulting lifetime of tropospheric Hg0 against oxidation is 2.7 months, shorter than in previous models. Fast HgII atmospheric reduction must occur in order to match the ~ 6-month lifetime of Hg against deposition implied by the observed atmospheric variability of total gaseous mercury (TGM ≡ Hg0 + HgII(g)). We implement this reduction in GEOS-Chem as photolysis of aqueous-phase HgII-organic complexes in aerosols and clouds, resulting in a TGM lifetime of 5.2 months against deposition and matching both mean observed TGM and its variability. Model sensitivity analysis shows that the interhemispheric gradient of TGM, previously used to infer a longer Hg lifetime against deposition, is misleading because southern hemisphere Hg mainly originates from oceanic emissions rather than transport from the northern hemisphere. The model reproduces the observed seasonal TGM variation at northern mid-latitudes (maximum in February, minimum in September) driven by chemistry and oceanic evasion, but does not reproduce the lack of seasonality observed at southern hemisphere marine sites. Aircraft observations in the lowermost stratosphere show a strong TGM-ozone relationship indicative of fast Hg0 oxidation, but we show that this relationship provides only a weak test of Hg chemistry because it is also influenced by mixing. The model reproduces observed Hg wet deposition fluxes over North America, Europe, and China, including the maximum over the US Gulf Coast driven by HgBr oxidation by NO2 and HO2. Low Hg wet deposition observed over rural China is attributed to fast HgII reduction in the presence of high organic aerosol concentrations. We find that 80 % of global HgII deposition takes place over the oceans, reflecting the marine origin of Br and low concentrations of marine organics for HgII reduction, and most of HO2 and NO2 for second-stage HgBr oxidation.

A Study on Pathway and QSPR Models for Debromination of PBDEs with Pseudopotential Method

2014 ◽  
Vol 997 ◽  
pp. 25-32 ◽  
Author(s):  
Ling Yun Li ◽  
Yi Miao Lin ◽  
Ji Wei Hu
Keyword(s):  
Rate Constants ◽  
Polybrominated Diphenyl Ethers ◽  
Reaction Rate ◽  
Linear Regression Analysis ◽  
Basis Set ◽  
Pseudopotential Method ◽  
Computational Time ◽  
Least Squares Regression ◽  
Reaction Rate Constants ◽  
Qspr Study

Neutral PBDEs congeners and their corresponding radical anions were studied with the pseudopotential method of stuttgart group (SDD) effective-core potentials basis set for the bromine atoms and the all-electron basis set for all other atoms. The pseudopotential method can be used for compounds containing heavy elements with relativistic effects and can reduce the computational time. The quantitative structure property relationship (QSPR) study was also performed in this work to develop models to predict the normolized reaction rate constants for the reductive debromination of polybrominated diphenyl ethers (PBDEs) by zero-valent iron (ZVI). The partial least squares regression (PLSR), principal component analysis-multiple linear regression analysis (PCA-MLR), and back propagation artificial neural network (BP-ANN) approaches were employed for the QSPR study between the molecular descriptors and the logarithm of normalized reaction rate constants of fourteen selected BDE congeners. The results show that the ANN models could be more satisfactorily to predict the rate constants than the PLSR and PCA-MLR models.

scholarly journals Quantum Calculations to Estimate the Heat of Hydrogenation Theoretically

2020 ◽  
Author(s):  
Ali Amir Khairbek
Keyword(s):  
Unsaturated Hydrocarbon ◽  
Experimental Results ◽  
Basis Set ◽  
Good Linear ◽  
Complete Basis ◽  
Complete Basis Set ◽  
Complete Basis Set Limit ◽  
The Mean ◽  
Experimental Values ◽  
Linear Correlations

Standard enthalpies of hydrogenation of 29 unsaturated hydrocarbon compounds were calculated in the gas phase by CCSD(T) theory with complete basis set cc-pVXZ, where X = DZ, TZ, as well as by complete basis set limit extrapolation. Geometries of reactants and products were optimized at the M06-2X/6-31g(d) level. This M06-2X geometries were used in the CCSD(T)/cc-pVXZ//M06-2X/6-31g(d) and cc-pV(DT)Z extrapolation calculations. (MAD) the mean absolute deviations of the enthalpies of hydrogenation between the calculated and experimental results that range from 8.8 to 3.4 kJ mol−1 based on the Comparison between the calculation at CCSD(T) and experimental results. The MAD value has improved and decreased to 1.5 kJ mol−1 after using complete basis set limit extrapolation. The deviations of the experimental values are located inside the “chemical accuracy” (±1 kcal mol−1 ≈ ±4.2 kJ mol−1) as some results showed. A very good linear correlations between experimental and calculated enthalpies of hydro-genation have been obtained at CCSD(T)/cc-pVTZ//M06-2X/6-31g(d) level and CCSD(T)/cc-pV(DT)Z extrapolation levels (SD =2.11 and 2.12 kJ mol−1, respectively).

Reaction kinetics of OH radicals with glutaric acid and adipic acid in the aqueous phase

2021 ◽  
Author(s):  
Liang Wen ◽  
Thomas Schaefer ◽  
Hartmut Herrmann
Keyword(s):  
Aqueous Phase ◽  
Adipic Acid ◽  
Rate Constants ◽  
Density Functional ◽  
Glutaric Acid ◽  
Radical Reaction ◽  
Basis Set ◽  
Oh Radicals ◽  
Oh Radical ◽  
Energy Barriers

&lt;p&gt;Dicarboxylic acids (DCAs) are widely distributed in atmospheric aerosols and cloud droplets and are mainly formed by the oxidation of volatile organic compounds (VOCs). For example, glutaric acid and adipic acid are two kinds of the DCAs that can be oxidized by hydroxyl radical (&amp;#8231;OH) reactions in the aqueous phase of aerosols and droplets. In the present study, the temperature- and pH-dependent rate constants of the aqueous OH radical reactions of the two DCAs were investigated by a laser flash photolysis-long path absorption setup using the competition kinetics method. Based on speciation calculations, the OH radical reaction rate constants of the fully protonated (H&lt;sub&gt;2&lt;/sub&gt;A), deprotonated (HA&lt;sup&gt;-&lt;/sup&gt;) and fully deprotonated (A&lt;sup&gt;2-&lt;/sup&gt;) forms of the two DCAs were determined. The following Arrhenius expressions for the T-dependency of the OH radical reaction of glutaric acid, k(T, H&lt;sub&gt;2&lt;/sub&gt;A) = (3.9 &amp;#177; 0.1) &amp;#215; 10&lt;sup&gt;10&lt;/sup&gt; &amp;#215; exp[(-1270 &amp;#177; 200 K)/T], k(T, HA&lt;sup&gt;-&lt;/sup&gt;) = (2.3 &amp;#177; 0.1) &amp;#215; 10&lt;sup&gt;11&lt;/sup&gt; &amp;#215; exp[(-1660 &amp;#177; 190 K)/T], k(T, A&lt;sup&gt;2-&lt;/sup&gt;) = (1.4 &amp;#177; 0.1) &amp;#215; 10&lt;sup&gt;11&lt;/sup&gt; &amp;#215; exp[(-1400 &amp;#177; 170 K)/T] and adipic acid, k(T, H&lt;sub&gt;2&lt;/sub&gt;A) = (7.5 &amp;#177; 0.2) &amp;#215; 10&lt;sup&gt;10&lt;/sup&gt; &amp;#215; exp[(-1210 &amp;#177; 170 K)/T], k(T, HA&lt;sup&gt;-&lt;/sup&gt;) = (9.5 &amp;#177; 0.3) &amp;#215; 10&lt;sup&gt;10&lt;/sup&gt; &amp;#215; exp[(-1200 &amp;#177; 200 K)/T], k(T, A&lt;sup&gt;2-&lt;/sup&gt;) = (8.7 &amp;#177; 0.2) &amp;#215; 10&lt;sup&gt;10&lt;/sup&gt; &amp;#215; exp[(-1100 &amp;#177; 170 K)/T] (in unit of L mol&lt;sup&gt;-1&lt;/sup&gt; s&lt;sup&gt;-1&lt;/sup&gt;) were derived.&lt;/p&gt;&lt;p&gt;The energy barriers of the H-atom abstractions were simulated by the Density Functional Theory calculations run with the GAUSSIAN package using the M06-2X method and the basis set m062x/6-311++g(3df,2p). The results showed that the energy barriers were lower at the C&lt;sub&gt;&amp;#946;&lt;/sub&gt;-atoms and are higher at the C&lt;sub&gt;&amp;#945;&lt;/sub&gt;-atoms of the two DCAs, clearly suggesting that the H-atom abstractions occurred predominately at the C&lt;sub&gt;&amp;#946;&lt;/sub&gt;-atoms. In addition, the ionizations can enhance the electrostatic effects of the carboxyl groups, significantly reducing the energy barriers, leading to the order of OH radical reactivity as &amp;#160;&lt; &amp;#160;&lt; . This study intends to better characterize the losing processes of glutaric acid and adipic acid in atmospheres.&lt;/p&gt;

Respirometric evaluation of the biodegradability of confectionary wastewaters

1995 ◽  
Vol 32 (12) ◽  
pp. 11-19 ◽  
Author(s):  
D. Orhon ◽  
G. Yildiz ◽  
E. Ubay Çokgör ◽  
S. Sözen
Keyword(s):  
Mathematical Model ◽  
Curve Fitting ◽  
Rate Constants ◽  
Hydrolysis Rate ◽  
Kinetic Coefficients ◽  
Experimental Values

Confectionary effluents are typical examples of strong wastes of biodegradable nature, quite suitable for respirometric analysis. Three different confectionary effluents have been subjected to a treatability-oriented characterization, mainly by means of respirometric methods, yielding meaningful results on COD fractionation and significant kinetic coefficients. Experimental values have been tested by a multi-component mathematical model using the endogenous decay approach and hydrolysis rate constants corresponding to the slowly biodegradable COD fractions have been evaluated using curve fitting.

Tests of second-generation and third-generation density functionals for electron affinities of the alkylthio radicals

2014 ◽  
Vol 13 (04) ◽  
pp. 1450030 ◽  
Author(s):  
Aifang Gao ◽  
Aiguo Li
Keyword(s):  
Dft Method ◽  
Absolute Error ◽  
Molecular Structures ◽  
Basis Set ◽  
Density Functionals ◽  
Electron Affinities ◽  
Generalized Gradient ◽  
Experimental Values ◽  
P Type ◽  
Good Agreement

The molecular structures and electron affinities of the R – S / R – S -( R = CH 3, C 2 H 5, n- C 3 H 7, n- C 4 H 9, n- C 5 H 11, i- C 3 H 7, i- C 4 H 9, t- C 4 H 9) species have been studied using 17 pure and hybrid density functionals (five generalized gradient approximation (GGA) methods, six hybrid GGAs, one meta GGA method and five hybrid meta GGAs). The basis set used in this work is of double-ζ plus polarization quality with additional diffuse s- and p-type functions, denoted by DZP++. The geometries are fully optimized with each DFT method and discussed. Harmonic vibrational frequencies are found to be within 3.5% of available experimental values for most functionals. Three different types of the neutral-anion energy separations have been presented. The theoretical electron affinities of alkylthio radicals are in good agreement with the experiment data. The M06 method is very good for the adiabatic electron affinity calculations, and the average absolute error is 0.0439 eV. The HCTH method performs better for EA prediction. The M06-HF, mPWPW91, VSXC and B98 are also reasonable. The most reliable adiabatic electron affinities are predicted to be 1.864 eV ( CH 3 S ), 1.946 eV ( C 2 H 5 S ), 1.959 eV (n- C 3 H 7 S ), 1.970 eV (n- C 4 H 9 S ), 1.982 eV (n- C 5 H 11 S ), 2.053 eV (i- C 3 H 7 S ), 1.991 eV (i- C 4 H 9 S ) and 2.100 eV (t- C 4 H 9 S ) at the M06/DZP++ level of theory, respectively.

Accuracy Assessment of the ROHF-CCSD(T) Calculationsof Dipole Moments of Small Radicals

1998 ◽  
Vol 63 (9) ◽  
pp. 1409-1430 ◽  
Author(s):  
Miroslav Urban ◽  
Pavel Neogrády ◽  
Juraj Raab ◽  
Geerd H. F. Diercksen
Keyword(s):  
Large Deviation ◽  
Theoretical Calculations ◽  
Dipole Moments ◽  
Accuracy Assessment ◽  
Open Shell ◽  
Basis Set ◽  
Coupled Cluster ◽  
Hartree Fock ◽  
Experimental Values

Dipole moments of a series of radicals, OH, NO, NS, SF, SO, PO, ClO, CN, LiO, NO2, and ClO2 were calculated by the Coupled Cluster CCSD(T) method with the single determinant restricted open shell Hartree-Fock (ROHF) reference. For all molecules theoretical dipole moments were carefully compared to experimental values. The size and the quality of the basis set were systematically improved. Spin adaptation in the ROHF-CCSD(T) method, largest single and double excitation amplitudes and the T1 diagnostics were considered as indicators in the quality assessment of calculated dipole moments. For most molecules the accuracy within 0.01-0.03 D was readily obtained. For ClO and CN the spin adaptation was necessary - its contribution was as large as 0.03-0.045 D. Large deviation from experiment is observed for OH in its A2Σ+ excited state (0.135 D) and especially for LiO in its 2Π ground state (0.22 D). No indication of the failure of theoretical calculations was found which leads to the conclusion that, even if there is still a space for the improvement of theoretical calculations, experimental values should be reconsidered.

Computational Procedure of Lattice Energy Using the Ab Initio MO Method

2003 ◽  
Vol 02 (02) ◽  
pp. 233-244 ◽  
Author(s):  
Kanade Nagayoshi ◽  
Tohru Ikeda ◽  
Kazuo Kitaura ◽  
Shigeru Nagase
Keyword(s):  
Ab Initio ◽  
Molecular Crystals ◽  
Lattice Energy ◽  
Computational Procedure ◽  
Basis Set ◽  
Full Account ◽  
Packing Structure ◽  
Donor Acceptor ◽  
Ab Initio Mo ◽  
Experimental Values

Recently, we have proposed a computational procedure for calculations of lattice energies of molecular crystals using the ab initio MO method. This procedure does not use potential functions and is applicable to a variety of molecular crystals. The procedure has been successfully applied to calculation of packing structure of electron donor-acceptor complex, H3N–BF3, and hydrogen bonding crystal, CH3OH. In this work, we present a full account of the computational procedure. This method is applied to the packing structure calculations of hydrocarbon crystals, C2H2, C2H4 and C6H6. The lattice parameters optimized at the MP2/6-311++G** level are in good agreement with the experimental values. The basis set dependence of the lattice constants is also discussed for several crystals.

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