Clathrate-Based CO₂ Capture from Co₂-Rich Natural Gas and Biogas

Abstract

In this study, clathrate-based CO2 capture was investigated in the presence of thermodynamic promoters such as tetrahydrofuran (THF) and tetra-n-butyl ammonium chloride (TBAC) for upgrading CO2-rich natural gas and biogas. The phase equilibria, gas uptakes, gas composition measurements, and spectroscopic analyses of CH4 (50%), CO2 (50%), and promoter clathrates were examined with a primary focus on the effects of thermodynamic promoters on clathrate stability and cage filling behavior. The addition of THF and TBAC significantly enhanced the thermodynamic stability of CH4 (50%) and CO2 (50%) clathrates. 13C NMR and Raman spectroscopy clearly revealed that CO2 and CH4 are enclathrated in the clathrate cages. THF solutions demonstrated a faster growth rate of clathrates, but CO2 was less selective than CH4 in the THF clathrate phase due to the lower thermodynamic stability of the CO2 and THF clathrate compared to the CH4 and THF clathrate. TBAC solutions produced higher CO2 selectivity in the semiclathrate phase due to the presence of distorted small cages, which have a strong preference for CO2 molecules. The experimental results demonstrated that CO2 selectivity in the clathrate phase can be influenced by the thermodynamic stability, cage shape and dimension, and cage filling behavior in the presence of thermodynamic promoters, and thus, a suitable promoter and their optimum concentration should be carefully determined in designing and operating clathrate-based CO2 capture from natural gas or biogas.

Development and Continuous Operation of a Bench‐Scale System for the Production of O3 + O2 + CO2 Hydrates

“…The application of clathrate hydrate (hydrate) in gas separation and molecular storage techniques has already been proposed and investigated [11][12][13][14][15][16][17]. As a molecular storage technology, hydrates containing O 3 have been used [18][19][20][21][22][23][24][25].…”

Kinetic Selectivity of SF6 during Formation and Dissociation of SF6 + N2 Hydrates and Its Significance in Hydrate-Based Greenhouse Gas Separation

“…A more detailed description of the experimental apparatus and procedure is available in our previous papers. 7,9,14,23,24 Calculation Methods. The formation of the SF 6 + N 2 hydrate was simulated using the GROMACS source code.…”

“…16,19−21 Hydrate-based gas separation (HBGS) has been proposed as one of the promising methods for capturing greenhouse gases, and its feasibility has been confirmed by several researchers. 7,[10][11][12][13][14]16 According to our previous study, the hydrate method required a remarkably lower initial SF 6 concentration and pressure than the liquefaction method to provide a specified recovery ratio of SF 6 . 14 Many previous HBGS studies have focused on the equilibrium-stage separation covering phase equilibria of mixed clathrate hydrates, separation efficiency at an equilibrium state, and the equilibrium recovery ratio.…”

“…Guest molecules are trapped in these host cages, which are stabilized through van der Waals interaction between water molecules and guest molecules. , Clathrate hydrates have three common structures [structure I (sI), structure II (sII), and structure H], which are composed of different numbers of small and large cages that are differently sized and shaped. , The types of hydrate structure and the degree of guest occupancy in cages are generally determined from the thermodynamic conditions and the size and physico-chemical nature of guest molecules. Clathrate hydrates have been applied in the various fields of energy and environment: for instance, gas storage and transportation, CO 2 capture and storage, cold energy storage, desalination, and greenhouse gas separation due to their unique guest-incorporating features. − …”

Analysis of the Dissolution of CH4/CO2-Mixtures into Liquid Water and the Subsequent Hydrate Formation via In Situ Raman Spectroscopy

“…The formation of gas hydrates from CH 4 /CO 2 -mixtures has been extensively studied over the past three decades [16][17][18][19]. Some works report on the kinetics and selectivity of the gas hydrate formation process [20,21]. In some studies, liquid nitrogen [22] or coolant circulation [23] combined with gas chromatography were utilized for measuring gas compositions in a solid phase.…”