A Novel Highly Stable Carbon Dioxide Hydrate from a New Synergic Additive Mixture: Experimental and Theoretical Surveys

Abstract

Gas hydrate technology is known as an alternative method for natural gas storage. Carbon dioxide hydrate has recently received growing attention due to its many applications. Additives such as cyclohexane (CH) (non soluble in water) and 1,3 dioxolane (DX) (soluble in water) are able to tackle thermodynamic and kinetic imitations of hydrate formation. This study attempts to study the synergic effect of the (DX)/(CH) mixture on the formation conditions of CO 2 hydrate systems. These two additives have a promoting effect; however, there is no experimental data on the effect of their mixture in this regard. All experiments were performed by pursuing a constant-volume−pressure search technique with a step heating approach in the pressure, temperature, and the DX mass fraction (w) ranges of (1−55) bar, (280−310) K, and (4.1, 10.1%), respectively. The mixture of DX and CH significantly improved the stability of hydrate formation compared to individual promoters. A thermodynamic framework based on the van der Waals−Platteeuw model was developed to predict the DX/CH−CO 2 hydrate phase equilibrium. The Peng− Robinson equation of state was applied to acquire CO 2 properties in the gas phase. The DX and CH activity coefficient was obtained through the NRTL model. The results of the proposed model were found to be in satisfactory accordance with the experimental phase equilibrium data with a low discrepancy of 2.83%.

Effects of Sea Salts on the Phase Behavior and Synthesis of Methane Hydrates + THF: An Experimental and Theoretical Study

“…In eq , the fugacity of the promoter (THF) in the aqueous phase could be evaluated as follows f normalp normalL = x normalp normalL γ normalp normalL P normalp normals normala normalt .25em exp ( v p L false( P − P normalp normals normala normalt false) R T ) Here, x p L , and γ p L represent the mole fraction and activity coefficient of the promoter in the aqueous phase. v p L denotes the molar volume of the promoter and R is the universal constant of gases…”

“…In eq , the fugacity of the promoter (THF) in the aqueous phase could be evaluated as follows Here, x p L , and γ p L represent the mole fraction and activity coefficient of the promoter in the aqueous phase. v p L denotes the molar volume of the promoter and R is the universal constant of gases…”

“…In eq 2, the fugacity of the promoter (THF) in the aqueous phase could be evaluated as follows 38 = i k j j j j j j y…”

Review on Cooperative Effect of Compound Additives on CO2 Hydrate Formation: Recent Advances and Future Directions

“…Lirio et al found that compared with the single-component additive THF, the combination of the thermodynamic additive THF and kinetic additive sodium dodecyl sulfate (SDS) can considerably shorten the induction time and increase the formation rate . Hassan et al showed that compared with a single additive, the mixture of cyclohexane (CH) and 1,3-dioxane (DIOX) has a considerable synergistic effect on the formation characteristics of CO 2 hydrate . Liu et al found that mixing a modified herringbone carbon nanotube (MWCNT-HB) and SDS further enhanced the heat and mass transfers during hydrate formation, which promoted CO 2 hydrate formation …”