Modeling Dissociation Pressure of Semi-Clathrate Hydrate Systems Containing CO2, CH4, N2, and H2S in the Presence of Tetra-n-butyl Ammonium Bromide

2019 ◽  
Vol 44 (1) ◽  
pp. 15-28 ◽  
Author(s):  
Mohammad Mesbah ◽  
Ebrahim Soroush ◽  
Mashallah Rezakazemi
Keyword(s):  
Gas Phase ◽  
Mass Fraction ◽  
Guest Molecule ◽  
Clathrate Hydrate ◽  
Clathrate Hydrates ◽  
Ammonium Bromide ◽  
Guest Molecules ◽  
Dissociation Pressure ◽  
Tuning Parameters ◽  
Langmuir Adsorption

Abstract In this study, the phase equilibria of semi-clathrate hydrates of methane (CH4), carbon dioxide (CO2), nitrogen (N2), and hydrogen sulfide (H2S) in an aqueous solution of tetra-n-butyl ammonium bromide (TBAB) were modeled using a correlation based on a two-stage formation mechanism: a quasi-chemical reaction that forms basic semi-clathrate hydrates and adsorption of guest molecules in the linked cavities of the basic semi-clathrate hydrate. The adsorption of guest molecules was described by the Langmuir adsorption theory and the fugacity of the gas phase was calculated by Peng–Robinson (PR) equation of state (EOS). The water activity in the presence of TBAB was calculated using a correlation, dependent on temperature, the TBAB mass fraction, and the nature of the guest molecule. These equations were coupled together and form a correlation which was linked to a genetic algorithm for optimization of tuning parameters. The results showed an excellent agreement between model results and experimental data. In addition, an outlier diagnostic was performed for finding any possible doubtful data and assessing the applicability of the model. The results showed that more than 97 % of the data were reliable and they were in the applicability domain of the model.

Structural Transition of Trimethylamine Hydrate by Methane or Hydrogen Inclusion

2020 ◽  
Author(s):  
Minjun Cha
Keyword(s):  
Structural Transition ◽  
Guest Molecule ◽  
Clathrate Hydrate ◽  
Hydrogen Gas ◽  
Time Dependent ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
X Ray ◽  
Inclusion Process ◽  
Diffraction Patterns

<p>Recently, several alkylamine hydrates have been studied in an effort to reveal the structural transitions from semi- to ‘canonical’ clathrate hydrate in the presence of secondary guest molecules. Trimethylamine (TMA) is known to form the semi-clathrate hydrate, and it has been reported that the structural transition of the TMA semi-clathrate hydrate may not occur in the presence of hydrogen gas as a secondary guest molecule. This paper reports the structural transition of trimethylamine(TMA) hydrate induced by the type of guest molecules. Powder X-ray diffraction patterns of (TMA + H<sub>2</sub>) hydrates show the formation of hexagoanl P6/mmm hydrate, but those of (TMA + CH<sub>4</sub>) hydrates indicate the formation of cubic Fd3m hydrate. Without gaseous guest molecule, the crystal structure of pure TMA hydrate is identified as hexagonal P6/mmm. Therefore, inclusion of gaseous methane in TMA hydrate can induce the structural transition from hexagonal to cubic hydrate or the formation of metastable cubic hydrate. To clearly reveal this possibility, we also check the time-dependent structural patterns of binary (TMA + CH<sub>4</sub>) hydrates from 1 to 14 days, and the results show that the structural transition of TMA hydrate from hexagonal P6/mmm to cubic Fd3m hydrate structure can occur during the methane inclusion process.</p>

The Rotational Oscillations of Tetrahydrofuran in Tetrahydrofuran Clathrate Hydrate

1973 ◽  
Vol 51 (24) ◽  
pp. 4062-4071 ◽  
Author(s):  
D. D. Klug ◽  
E. Whalley
Keyword(s):  
Gas Phase ◽  
Low Frequency ◽  
Clathrate Hydrate ◽  
Water Molecules ◽  
Dielectric Measurements ◽  
Effective Dipole Moment ◽  
Orientational Disorder ◽  
Guest Molecules ◽  
Rotational Oscillations ◽  
Good Agreement

The absorptivity of tetrahydrofuran clathrate hydrate in the range 70–7 cm−1 has been measured at several temperatures in the range 17–80 K. There are two broad bands with maxima at 25 and 38 cm−1 which are due to the rotational oscillations of tetrahydrofuran molecules in their cages. The integrated absorptivity yields an effective dipole moment for the oscillation of 1.63 D, which is close to the gas-phase value. The negative second moment of the absorptivity yields the contribution 0.105 ± ~0.007 to the low-frequency refractive index, in good agreement with a less accurate value from dielectric measurements. The orientational disorder of the water molecules causes a distribution of potentials hindering the rotational oscillations of the guest molecules, and a detailed analysis of the shapes of the bands yields directly the distribution of force constants for the oscillations.

Managing Hydrogen Bonding in the Clathrate Hydrate of the 1-Pentanol Guest Molecule

CrystEngComm ◽  
2021 ◽  
Author(s):  
Byeonggwan Lee ◽  
Jeongtak Kim ◽  
Kyuchul Shin ◽  
Ki Hun Park ◽  
Minjun Cha ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Guest Molecule ◽  
Clathrate Hydrate ◽  
Guest Molecules

It remains a difficult task to predict the hydrate structure and conformation of potential guest molecules in one of the three canonical hydrate lattices. 1-pentanol is characteristic of molecules that...

Far infrared absorption and rotational vibrations of the guest molecules in structure I clathrate hydrates between 4.3 and 100 K

1977 ◽  
Vol 55 (10) ◽  
pp. 1777-1785 ◽  
Author(s):  
John E. Bertie ◽  
Stephen M. Jacobs
Keyword(s):  
Ethylene Oxide ◽  
Guest Molecule ◽  
Signal To Noise Ratio ◽  
Michelson Interferometer ◽  
Far Infrared ◽  
Force Constants ◽  
Clathrate Hydrates ◽  
High Signal ◽  
Guest Molecules ◽  
Trimethylene Oxide

The infrared spectra between 330 and 15 cm−1 of the structure I clathrate hydrates of ethylene oxide, cyclopropane, and trimethylene oxide, at 4.3 K are presented. The spectra have an unusually high signal-to-noise ratio made possible by a Michelson interferometer and a silicon bolometer detector which operates at 1.2 K. Rotational vibrations of the guest molecules were observed at 65.0 and 35.6 cm−1 for ethylene oxide and at 69 and 50 cm−1 for trimethylene oxide. Inter-guest coupling of rotational vibrations is small and the two frequencies are assigned to vibrations about different inertial axes. The resulting force constants are 487 and 264 ferg rad−2 for ethylene oxide and 1190 and 1130 ferg rad−2 for trimethylene oxide and are discussed in relation to the barriers to reorientation of the guest molecule. The bands due to these vibrations are fairly sharp at 4.3 K, but are broad and poorly defined at 100 K. The guest and water vibrations interact predominantly through their transition dipoles, although the main contribution to the force constants of the rotational vibrations is from steric forces. The absorption by the water vibrations above 100 cm−1 is very similar for ethylene oxide and cyclopropane hydrates but significantly different for trimethylene oxide hydrate. Strong objections exist to the obvious interpretations of this difference which remains unexplained.

Component of Clathrate Hydrates Formed in CH4-TBAB-H2O System

2011 ◽  
Vol 383-390 ◽  
pp. 2883-2888 ◽  
Author(s):  
Liang Yang ◽  
Shuan Shi Fan ◽  
Xue Mei Lang ◽  
Yan Hong Wang ◽  
Dan Dan Bi
Keyword(s):  
Mass Fraction ◽  
Storage Capacity ◽  
Magnetic Suspension ◽  
Clathrate Hydrates ◽  
Methane Hydrates ◽  
Ammonium Bromide ◽  
Methane Storage ◽  
Maximum Value ◽  
Temperature And Pressure ◽  
The Ideal

Methane storage data of clathrate hydrates formed in ternary system, methane-tetra-n-butyl ammonium bromide-water (CH4-TBAB-H2O), was measured by a magnetic suspension weight adsorption instrument at the temperature of 273.64 ~ 278.23 K and the pressure of 2.01 ~ 7.07 MPa, for two concentration (20.8 wt % and 43.3 wt %) of TBAB solutions. The hydrates component was qualitatively analyzed. The results showed that the structure of CH4-TBAB semi-clathrate hydrates was deformed at high pressure possibly due to methane molecules replacing TBAB molecules and forming structure I true methane hydrates for the 20.8 wt % TBAB solutions at 273.64 K. For 43.3 wt % TBAB solutions, at the same experimental temperature and pressure, the maximum mass fraction of methane in CH4-TBAB-H2O clathrate hydrates was only 1.64 wt % which was less than the ideal maximum value (3.08 wt %). It showed that for the 20.8 wt % TBAB solutions, TBAB molecules were not replaced by methane molecules but both CH4-TBAB semi-clathrate hydrates and structure I true methane hydrates were formed simultaneously. For 43.3 wt % TBAB solutions, the reason of low methane storage capacity may be that the pressure was not high enough.

Modeling Phase Behavior of Semi-Clathrate Hydrates of CO2, CH4, and N2 in Aqueous Solution of Tetra-n-butyl Ammonium Fluoride

2019 ◽  
Vol 44 (2) ◽  
pp. 155-167 ◽  
Author(s):  
Mohammad Mesbah ◽  
Sanaz Abouali Galledari ◽  
Ebrahim Soroush ◽  
Masumeh Momeni
Keyword(s):  
Aqueous Solution ◽  
Ammonium Fluoride ◽  
Simplex Algorithm ◽  
Clathrate Hydrates ◽  
Guest Molecules ◽  
Tuning Parameters ◽  
Clathrate Compounds ◽  
System Temperature ◽  
Robinson Equation ◽  
Good Agreement

AbstractSemi-clathrate hydrates are members of the class of clathrate compounds. In comparison with clathrate hydrates, where the networks are formed only by H2O molecules, the networks of semi-clathrate hydrates are formed by mixtures of H2O and quaternary ammonium salts (QASs). The addition of QASs to the solution enables to improve the formation of semi-clathrate hydrates at much milder conditions comparing to clathrate hydrates. In this work, we study the phase equilibria of semi-clathrate hydrates of CH4, CO2, and N2gas in an aqueous solution of tetra-n-butyl ammonium fluoride (TBAF). An extension of the Chen–Guo model is proposed as a thermodynamic model. The Peng–Robinson equation of state (PREOS) was applied to calculate the fugacity of the gas phase and in order to determine the water activity in the presence of TBAF, a correlation between the system temperature, the TBAF mass fraction, and the nature of the guest molecules has been used. These equations were solved simultaneously and through optimizing tuning parameters via the Nelder–Mead simplex algorithm. The results are compared to experimental data and good agreement is observed.

scholarly journals Semi-clathrate hydrate phase stability conditions for methane + TetraButylAmmonium Bromide (TBAB)/TetraButylAmmonium Acetate (TBAA) + water system: Experimental measurements and thermodynamic modeling

2021 ◽  
Vol 76 ◽  
pp. 75
Author(s):  
Hamideh Irannezhad ◽  
Jafar Javanmardi ◽  
Ali Rasoolzadeh ◽  
Khayyam Mehrabi ◽  
Amir H. Mohammadi
Keyword(s):  
Phase Equilibrium ◽  
Aqueous Solutions ◽  
Mass Fraction ◽  
Tetrabutylammonium Bromide ◽  
Clathrate Hydrate ◽  
Clathrate Hydrates ◽  
Stability Conditions ◽  
Equilibrium Conditions ◽  
Hydrate Phase ◽  
Mass Fractions

One of the promising applications of clathrate/gas hydrates is the transport and storage of natural gas. Semi-clathrate hydrates have received more attention due to milder pressure/temperature stability conditions compared to ordinary clathrate hydrates. The most commonly reported semi-clathrate hydrates are formed from a combination of gas + water + quaternary ammonium salts. In this work, a total of 53 equilibrium data for semi-clathrate hydrates of methane + TetraButylAmmonium Bromide (TBAB)/TetraButylAmmonium Acetate (TBAA) aqueous solutions were experimentally measured. For TBAB, three concentrations including 0.0350, 0.0490, and 0.1500 mass fractions were used. For TBAA, a solution with a 0.0990 mass fraction was used. Additionally, the modified Chen–Guo model was applied to calculate the hydrate phase equilibrium conditions of methane + TBAB/TBAA aqueous solutions. The model can accurately calculate the aforementioned semi-clathrate hydrate phase equilibrium conditions with the Average Absolute Deviations ((AAD)T and (AAD)P) of 0.1 K and 0.08 MPa, respectively. The temperature increments for 0.0350, 0.0490, and 0.1500 mass fractions of TBAB are 7.7, 9.4, and 13.5 K, respectively. This value for 0.0990 mass fraction of TBAA is 6.2 K. Therefore, it is concluded that TBAB is a stronger hydrate promoter compared to TBAA.

The anomalous halogen bonding interactions between chlorine and bromine with water in clathrate hydrates

2017 ◽  
Vol 203 ◽  
pp. 61-77 ◽  
Author(s):  
Hana Dureckova ◽  
Tom K. Woo ◽  
Konstantin A. Udachin ◽  
John A. Ripmeester ◽  
Saman Alavi
Keyword(s):  
Ab Initio ◽  
Halogen Bonding ◽  
Chem Phys ◽  
Clathrate Hydrate ◽  
Clathrate Hydrates ◽  
Water Molecules ◽  
Guest Molecules ◽  
X Ray ◽  
Covalent Interaction ◽  
Water Oxygen

Clathrate hydrate phases of Cl2 and Br2 guest molecules have been known for about 200 years. The crystal structure of these phases was recently re-determined with high accuracy by single crystal X-ray diffraction. In these structures, the water oxygen–halogen atom distances are determined to be shorter than the sum of the van der Waals radii, which indicates the action of some type of non-covalent interaction between the dihalogens and water molecules. Given that in the hydrate phases both lone pairs of each water oxygen atom are engaged in hydrogen bonding with other water molecules of the lattice, the nature of the oxygen–halogen interactions may not be the standard halogen bonds characterized recently in the solid state materials and enzyme–substrate compounds. The nature of the halogen–water interactions for the Cl2 and Br2 molecules in two isolated clathrate hydrate cages has recently been studied with ab initio calculations and Natural Bond Order analysis (Ochoa-Resendiz et al. J. Chem. Phys. 2016, 145, 161104). Here we present the results of ab initio calculations and natural localized molecular orbital analysis for Cl2 and Br2 guests in all cage types observed in the cubic structure I and tetragonal structure I clathrate hydrates to characterize the orbital interactions between the dihalogen guests and water. Calculations with isolated cages and cages with one shell of coordinating molecules are considered. The computational analysis is used to understand the nature of the halogen bonding in these materials and to interpret the guest positions in the hydrate cages obtained from the X-ray crystal structures.

scholarly journals Type II Clathrate Hydrate Formation in Cometary Ice Analogs in Vacuo

1992 ◽  
Vol 150 ◽  
pp. 437-438
Author(s):  
D. F. Blake ◽  
L. Allamandola ◽  
S. Sandford ◽  
D. Hudgins ◽  
F. Freund
Keyword(s):  
High Vacuum ◽  
Hydrate Formation ◽  
Clathrate Hydrate ◽  
Clathrate Hydrates ◽  
Type Ii ◽  
State Transformation ◽  
Solid State Transformation ◽  
Guest Molecules ◽  
Amorphous Ices ◽  
Analog Experiments

Clathrate Hydrates can be formed under high vacuum conditions by annealing vapor-deposited amorphous ices of the appropriate composition. When astrophysically significant H2O:CH3OH ices are deposited and annealed, Type II Clathrate Hydrates are formed which can hold up to 6 mole % large guest molecules such as methanol and 12 mole % small guest molecules such as CO2 and CO. The solid state transformation of amorphous mixed molecular ice into crystalline clathrate hydrate and its sublimation at higher temperatures may serve to explain heretofore anomalous mechanical and gas release properties observed in cometary ices and laboratory ice analog experiments.

scholarly journals Hydrogen Inter-Cage Hopping and Cage Occupancies inside Hydrogen Hydrate: Molecular-Dynamics Analysis

2020 ◽  
Vol 11 (1) ◽  
pp. 282
Author(s):  
Yogeshwaran Krishnan ◽  
Mohammad Reza Ghaani ◽  
Arnaud Desmedt ◽  
Niall J. English
Keyword(s):  
Molecular Dynamics ◽  
Energy Barrier ◽  
Guest Molecule ◽  
Arrhenius Equation ◽  
Dynamics Simulation ◽  
Type Ii ◽  
Large Cage ◽  
Guest Molecules ◽  
Simulation Time ◽  
Average Occupancy

The inter-cage hopping in a type II clathrate hydrate with different numbers of H2 and D2 molecules, from 1 to 4 molecules per large cage, was studied using a classical molecular dynamics simulation at temperatures of 80 to 240 K. We present the results for the diffusion of these guest molecules (H2 or D2) at all of the different occupations and temperatures, and we also calculated the activation energy as the energy barrier for the diffusion using the Arrhenius equation. The average occupancy number over the simulation time showed that the structures with double and triple large-cage H2 occupancy appeared to be the most stable, while the small cages remained with only one guest molecule. A Markov model was also calculated based on the number of transitions between the different cage types.

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