Polyvinyl acetate/poly(amide-12-b-ethylene oxide) blend membranes for carbon dioxide separation

In this paper,blend membranes from polyvinyl acetate(PVAc)and block copolymer poly(amide-12-b-ethylene oxide)(Pebax1074)are prepared by solution casting and solvent evaporation method.Although they are homogeneous on a macro-scale,the observations from DSC and SEM indicate micro-phase separation for PVAc/Pebax1074 blend membranes.With the increase of Pebax1074 content,gas permeabilities of CO2,H2,N2and CH4all increase greatly.PVAc/Pebax1074 blend membranes with high PVAc content are appropriate for CO2/CH4separation.The temperature dependence of gas permeability is divided into rubbery region and glassy region.The activation energies of permeation in rubbery region are smaller than those in glassy region,and they all decrease with increasing Pebax1074 content.For N2,H2and CH4,their gas permeation properties are mainly influenced by the dual-mode sorption and hydrostatic pressure effect.But for CO2,its permeability increases with the increase of pressure due to CO2-induced plasticization effect,which is more obvious for PVAc/Pebax1074 blend membranes with high PVAc content.

Poly(amide-6-b-ethylene oxide)/[Bmim][Tf2N] blend membranes for carbon dioxide separation

Poly（amide-6-b-ethylene oxide）（Pebax1657）/1-butyl-3-methylimidazo-lium bis[trifluoromethyl）sulfonyl]-imide（[Bmim][Tf2N]） blend membranes with different [Bmim][Tf2N] contents were prepared via solution casting and solvent evaporation method. The permeation properties of the blend membranes for CO2, N2,CH4 and H2 were studied, and the physical properties were characterized by differential scanning calorimeter（DSC） and X-ray diffraction（XRD）. Results showed that [Bmim][Tf2N] was dispersed as amorphous phase in the blend membranes, which caused the decrease of Tg（PE） and crystallinity（PA）. With the addition of [Bmim][Tf2N], the CO2 permeability increased and reached up to approximately 286 Barrer at 40 wt%[Bmim][Tf2N], which was nearly double that of pristine Pebax1657 membrane. The increase of CO2 permeability may be attributed to high intrinsic permeability of [Bmim][Tf2N], the increase of fractional free of volume（FFV） and plasticization effect. However, the CO2 permeability reduced firstly when the [Bmim][Tf2N]content was below 10 wt%, which may be due to that the small ions of [Bmim][Tf2N] in the gap of polymer chain inhibited the flexibility of polymer chain; the interaction between Pebax1657 and [Bmim][Tf2N]decreased the content of EO units available for CO2 transport and led to a more compact structure. For Pebax1657/[Bmim][Tf2N] blend membranes, the permeabilities of N2, H2 and CH4decreased with the increase of feed pressure due to the hydrostatic pressure effect, while CO2 permeability increased with the increase of feed pressure for that the CO2-induced plasticization effect was stronger than hydrostatic pressure effect.

Efficient acetylene/carbon dioxide separation with excellent dynamic capacity and low regeneration energy by anion-pillared hybrid materials

Adsorptive separation of acetylene/carbon dioxide mixtures by porous materials is an important and challenging task due to their similar sizes and physical properties.Here,remarkable acetylene/carbon dioxide separation featuring a high dynamic breakthrough capacity for acetylene(4.3 mmol·g^(–1))as well as an ultralow acetylene regeneration energy(29.5 kJ·mol^(–1))was achieved with the novel TiF_(6)^(2–)-pillared material ZU-100(TIFSIX-bpy-Ni).Construction of a pore structure with abundant TiF_(6)^(2–)anion sites and pores with appropriate sizes enabled formation of acetylene clusters through hydrogen bonds and intermolecular interactions,which afforded a high acetylene capacity(8.3 mmol·g^(–1))and high acetylene/carbon dioxide uptake ratio(1.9)at 298 K and 1 bar.Moreover,the NbO_(5)^(2–)anion-pillared material ZU-61 investigated for separation of acetylene/carbon dioxide.In addition,breakthrough experiments were also conducted to further confirm the excellent dynamic acetylene/carbon dioxide separation performance of ZU-100.

Analysis of CO₂Pressure Swing Adsorption Simulation by Considering the Transport Phenomena in the Adsorber

This study focused on CO2 separation technology with adsorption. This paper describes the analysis carried out by a CO2 pressure swing adsorption simulation to scale up the absorber. An unsteady one-dimensional balance model was constructed by considering the material, energy, and momentum. In the CO2 breakthrough test, the beginning time and CO2 concentration at outlet of CO2 breakthrough in the calculation were almost equivalent to that of experiment results. The correlation consistency of the calculation results with the analysis model and the experimental results obtained by a bench scale experiment was evaluated. The transport phenomena in the adsorber were investigated at the adsorption, rinse, and desorption steps according to the calculation results. The starting time of CO2 breakthrough obtained by the analysis is equal to that obtained by the adsorption breakthrough experiment. This confirms that the CO2 adsorption, and the temperature and velocity distribution in the adsorber, change as a function of the adsorption, rinse, and desorption steps, respectively. Additionally, the CO2 concentration of the captured gas and the amount of CO2 quantity were 93.4% per day and 2.9 ton/day, respectively. These values are equal to those obtained by the bench scale experiment.

Auxiliary ligand-directed assembly of a non-interpenetrated cage-within-cage metal-organic framework for highly efficient C_(2)H_(2)/CO_(2) separation

The development of metal-organic frameworks(MOFs)with highly efficient adsorption and separation of acet-ylene is very important and challenging in chemical industry due to the explosive nature of acetylene.Porous MOFs can be constructed by inserting a second auxiliary ligand,which allows the use of large ligands to construct non-interpenetrated structures and increase pore utilization.Herein,SNNU-205 is successfully synthesized,which connects two sets of interpenetrated structures to form a double walled cage-within-cage structure by using the introduction of a second auxiliary ligand.The modified pore environment enables SNNU-205 to efficiently selectively adsorb C_(2)H_(2)over CO_(2).At 298 K and 1 atm,SNNU-205 can uptake much more C_(2)H_(2)(76.3 cm^(3)g1)than CO_(2)(47.3 cm^(3)g^(-1)),resulting in a high substance ratio of C_(2)H_(2)-to-CO_(2)(1.6).More importantly,the ideal adsorbed solution theory selectivity calculations and column breakthrough tests further indicate SNNU-205 to be promising adsorbents for C_(2)H_(2)adsorption and purification.