Propane, n -butane and i-butane stabilization effects on methane gas hydrates

Abstract

The goal of this work is to analyse the hydrate equilibria of methane + propane, i-butane and n-butane gas mixtures. Experimental hydrate equilibrium data was acquired for various compositions of these components in methane, ranging from 0.5-6.8 mol%. Applying this information with the Clausius-Clapeyron equation, the extent of hydrate promotion was demonstrated quantitatively by calculating the slope of the equation and the dissociation enthalpy (ΔHd). Methane equilibria was found to be most sensitive towards propane and ibutane, where very small concentrations were sufficient to increase the thermodynamic conditions for hydrate equilibrium drastically. The degree of hydrate stabilisation, i.e. transition from sI to sII hydrate, was immediatethere was no detectable composition slightly above 0.0 mol% where propane or i-butane did not have a sII hydrate-promoting impact, although one was implied with the aid of Calsep PVTsim calculations. Addition of nbutane to methane was far less sensitive and was deemed inert from 0.0-0.5 mol%. It was concluded that the sII hydrate was favoured when the n-butane composition exceeded 0.5-0.75 mol%. The influence of composition on stability was quantified by determining the gradient of ΔHd versus mol% plots for the initial steep region that represents the increasing occupancy of the sII guests. Average gradients of 11.66, 26.64 and 43.50 kJ/mol.mol% were determined for n-butane, propane and i-butane addition to methane respectively. A hydrateinert range for propane/i-butane (in methane) was suspected according to the perceived inflection point when less 0.5 mol%, implying the gradient was very low at some minute concentration range starting at 0.0 mol%. Awareness of these sI to sII transition regions is beneficial to natural gas recovery and processing as a small percentage of these components may remain without being detrimental in terms of promoting the hydrate equilibria.

Geometric and Hydrophilic Effects of Oxirane Compounds with a Four-Carbon Backbone on Clathrate Hydrate Formation

“…Here, it should be also noted that both 33DMEB and 12EB/ c23EB exhibited higher promotion capacities than 22DMB 60,61 and n-butane, 62 respectively, despite the similarity in molecular sizes and geometries. This trend has consistently been reported in other (oxirane + CH 4 ) vs (simple alkane + CH 4 ) systems, such as PO vs propane, 17 EIB vs i-butane, 17 12ECP vs CP, 15 12ECH vs cyclohexane.…”

“…Equilibrium P–T conditions of the CH 4 hydrates (a) containing 33DMEB and 22DMB ( x = 0.029); (b) containing 12EB, c 23EB, t 23EB, DEB (x = 0.056), and n -butane. The data for none (simple CH 4 hydrate), 22DMB, , and n -butane (CH 4 / n -butane = 94.5/5.5) are from previous studies.…”

Toward a Robust, Universal Predictor of Gas Hydrate Equilibria by Means of a Deep Learning Regression

“…While there is an overlap between data used in this study and several others published in the field, other equilibrium data sources published in recent years or overlooked in the past have been included. All data sources have been referenced. ,,,,− …”

“…All equilibrium data used in this investigation have been obtained from the following sources. All sources of equilibrium data used in the development of models in this research have been referenced. ,,,,− It must be emphasized that not all data from each source is included in the dataset, for instance, several measurements from the popular Deaton and Frost study have been excluded due to a lack of separation of iso butane and n -butane.…”

Coexistence of Methane Hydrate and Gas Associated with the Difference in Thermodynamic Stabilities of Hydrate in the Pores of Sediments from Shenhu, South China Sea

“…They observed that the equilibrium curves shifted toward the higher-pressure region due to the combined effects of pores and electrolytes . Smith et al found that the equilibrium line of methane is sensitive to small concentrations (0.5 mol %) of propane and i-butane, and they further observed that the structural stability of sII hydrate intensifies as the concentration of propane and i-butane increases . A multitude of thermodynamic inhibitors and promoters has been identified to exert a notable impact on the hydrate equilibrium conditions, thereby influencing the formation and dissociation of hydrates. − Gas hydrate formation involves the consumption of gas and water.…”