Experimental and Modeling Study on Phase Equilibria of Semiclathrate Hydrates of Tetra-n-butyl Ammonium Bromide + CH₄, CO₂, N₂, or Gas Mixtures

Abstract

Tetra-n-butyl ammonium bromide (TBAB) is most-widely used as a hydrate promoter in the separation of flue gases and CO 2 sequestration. Because of the complicacy of semiclathrate hydrate formed by TBAB aqueous solution and gases, few researchers have investigated the thermodynamic modeling of phase equilibria of semiclathrate hydrates. In this work, the CH 4 −N 2 hydrate dissociation conditions were determined in TBAB solution first, and then a thermodynamic model for gas hydrate proposed by Chen and Guo was extended for semiclathrate hydrates of gas mixtures in TBAB aqueous solution. The Patel-Teja equation of state (PT EoS) was used for calculation of the fugacity of the gas phase. To evaluate the activity of water and activity coefficients of TBAB in TBAB aqueous solution, a correlation on the basis of existing osmotic coefficient and activity coefficient values is employed. For modeling the hydrate phase, parameters for sII hydrates proposed in the Chen−Guo hydrate model were used to calculate the fugacity of gases in hydrate phase, and parameters of TBAB were obtained from the correlation with the literature dissociation data for the pure gas + TBAB + water system. Then the presented model was used to predict dissociation data for the gas mixtures + TBAB + water system, and the results show acceptable agreement with other literature data and the experimental data for CH 4 −N 2 in this work.

Modeling Tetra-n-butyl ammonium halides aqueous solutions with the electrolyte cubic plus association equation of state

“…These authors did not investigate the predictive ability of the model for TBAB related fluid systems. Other researchers [26,27,28] applied nonelectrolyte EOS plus empirical correlations for water activity.…”

Experimental and modeling study on the phase equilibria for hydrates of gas mixtures in TBAB solution

“…In this work, the following equation (Liao et al, 2013) is used to calculate the activity of water (a w ) in the TBAB aqueous solution:…”

“…Nonetheless, the extension of the model they proposed to the multi-component systems needs further study. Liao et al (2013) developed a modified model to calculate phase equilibria of TBAB semiclathrate hydratesþ CH 4 , CO 2 , N 2 or gas mixtures on the basis of the calculation of sII hydrate in the Chen and Guo model (Chen and Guo, 1998). Fukumoto et al (2014) used a thermodynamic approach proposed by Paricaud (2011) to determine the dissociation conditions of H 2 semiclathrate hydrates with TBAB, TBAF, TBPB and TBANO 3 salts.…”

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

“…Mohammadi et al [28] measured the semi-clathrate hydrate phase stability conditions of some gases in the presence of various mass fractions of TBAB. Liao et al [29] explicated the impact of TBAB on the semi-clathrate hydrates of some gases and employed the Chen-Guo model [30,31] to predict their experimental data. Roosta et al [32] perused the efficiencies of some promoters on the methane hydrate formation kinetics.…”