Solid CO2-philes as potential phase-change physical solvents for CO2

The binary phase behavior of mixtures of CO2 and highly CO2-philic solids has been determined at 298 K. The solids include sugar acetates (β-d-galactose pentaacetate, β-d-ribofuranose tetraacetate, α-d(+)-glucose pentaacetate, d-(+)-sucrose octaacetate), tert-butylated aromatics (2,4-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, 3,5-di-tert-butylphenol, 1,2,4-triacetoxybenzene), and a highly oxygenated cyclic compound (1,3,5-trioxane). The results are presented in the form of phase behavior (Px) diagrams at 298 K that exhibit either one (vapor–liquid–solid, VLS) or two (vapor–liquid–liquid, VL1L2 and vapor–liquid–solid, VL2S) three-phase equilibrium lines.Ternary phase behavior at 298 K has also been determined and presented in the form of a pseudo-binary Px diagram for mixtures of an equimolar gas blend of CO2 and H2 and each of these CO2-philic solids and several other previously identified highly CO2-philic compounds. Only four compounds, sucrose octaacetate, 1,3,5-tri-tert-butylbenzene, 2,4-di-tert-butylbenzene, and 1,3,5-trioxane, melted at 298 K in the presence of the CO2/H2 mixture at three-phase vapor–liquid–solid pressures ranging between 6 MPa and 10 MPa. These four compounds are candidates for the selective absorption of CO2 from a CO2/H2 mixture using solid compounds that can melt and selectively absorb CO2.

Figure optionsDownload as PowerPoint slideHighlights
► Physical solvents for CO2 capture are examined.
► Solvents fall under two classifications: tert-butylated aromatics or sugar acetates.
► Binary phase behavior diagrams of CO2 and each solid solvent.
► Ternary phase behavior diagrams of equimolar CO2/H2 and each solid solvent.