GPU For CO2 Research Articles

Carbon molecular sieve hollow fiber composite membrane derived from PMDA-ODA polyimide for gas separation

Carbon molecular sieve (CMS) membranes have excellent gas separation property over conventional polymeric membranes and superior anti-swelling property. PMDA-ODA polyimide has high thermal stability and good mechanical property. It has been extensively adopted as the precursor of CMS membrane. However, due to the insoluble nature, PMDA-ODA CMS membranes are limited to configurations like dense symmetric films or composite membranes using porous inorganic or metal substrates. In this work, CMS hollow fiber composite membranes based on an asymmetric PMDA-ODA hollow fiber were successfully prepared for the first time. The neat PMDA-ODA hollow fiber membrane was crosslinked by polyethyleneimine to alleviate pore collapsing during carbonization and then dip-coated by a PMDA-ODA PAA solution to seal the surface defects. The PDMA-ODA CMS composite hollow fiber membranes showed gas permeances of 93.4 GPU, 19.6 GPU, 6.5 GPU, and 4.7 GPU for CO2, O2, N2, and CH4, respectively, with an ideal selectivity of 14.4, 3.0, and 19.8 for CO2/N2, O2/N2, and CO2/CH4 gas pairs, respectively. The attractive gas separation property shows a great potential for industrial application.

Preparation and Characterization of Mixed Matrix Membrane based on Polysulfone (PSF) and Lanthanum Orthoferrite (LaFeO3) for Gas Separation

The aim of this study is to investigate the effects of polysulfone (PSF) and lanthanum orthoferrite (LaFeO3) incorporated mixed matrix membrane (MMM) on gas permeation and selectivity properties. PSF/LaFeO3 MMMs were prepared with various weights loading of LaFeO3. The membranes obtained were characterized using scanning electron microscope (SEM), thermal gravimetric analysis (TGA) and Fourier-transform infra-red (FT-IR). The gas transport properties of MMM were measured using single gas permeation set up (CO2, CH4, O2 and N2) at ambient temperature, and feed pressure of 2, 4 and 6 bar. The permeation test showed that the mixed matrix membrane exhibited high permeability. With increasing LaFeO3 weight loading to 1.0%, the highest permeability values were 47.74 GPU for CO2, 29.85 GPU for CH4, 57.56 GPU for O2, and 40.66 GPU for N2. The results also showed that by incorporating 1.0wt% of LaFeO3 into PSF matrix, the highest CO2/CH4 and O2/N2 selectivity of 1.60 and 1.42 respectively were obtained. Overall, all the resultants MMM showed higher permeability and selectivity compared to pure PSF membrane.

Expanded Porphyrins as Two-Dimensional Porous Membranes for CO2 Separation.

Porphyrin-based two-dimensional polymers have uniform micropores and close to atom-thin thicknesses, but they have not been explored for gas separation. Herein we design various expanded porphyrin derivatives for their potential application in membrane gas separation, using CO2/N2 as an example. Pore sizes are determined based on both van der Waals radii and electron density distribution. Potential energy curves for CO2 and N2 passing through are mapped by dispersion-corrected density functional theory calculations. The passing-through barriers are used to evaluate CO2/N2 separation selectivity. Promising subunits for CO2 separation have been selected from the selectivity estimates. 2D membranes composed of amethyrin derivatives are shown to have high ideal selectivity on the order of 10(6) for CO2/N2 separation. Classical molecular dynamics simulation yields a permeance of 10(4)-10(5) GPU for CO2 through extended 2D membranes based on amethyrin derivatives. This work demonstrates that porphyrin systems could offer an attractive bottom-up approach for 2D porous membranes.

Nanosilica and H-Mordenite incorporated Poly(ether-block-amide)-1657 membranes for gaseous separations

Two types of inorganic fillers – nanosilica and H-Mordenite were embodied into the Poly(ether-block-amide)-1657 polymer matrix to prepare mixed matrix membranes. Effect of filler loading and applied feed pressure on the performance of membranes was investigated. The distribution of fillers in the polymers, structural characteristics and interaction of fillers with polymer in membranes were scrutinized by SEM, FTIR and XRD. Single gas permeance of CO2, N2, H2 and O2 through the membranes was determined at ambient temperature (30°C). The embodiment of nanosilica into the polymer matrix enhanced the permeance of all gases and it was found that CO2 diffuses significantly through the nanosilica and polymer matrix when compared to other gases. For 0.3wt.% Si/Pebax membrane, with increasing pressure from 10 to 30kg/cm2, permeance enhanced from 8.9 to 36.1GPU for CO2, 1.1 to 3.5GPU for H2, 0.49 to 1.3GPU for O2 and 0.12 to 0.43GPU for N2. The effect of H-Mordenite loading had revised the permeance from 1.1 to 5.4GPU for CO2, 0.56 to 0.87GPU for H2, 0.09 to 0.39GPU for O2 and 0.03 to 0.205GPU for N2. With increasing pressure, a significant enhancement in selectivity of CO2/N2 was noticed for both Si/Pebax and H-Mordenite/Pebax membranes. Thus Pebax mixed matrix membranes provide a possible means for separation of CO2/N2 and enrichment of O2 and N2 from the air.

CO2 Selectivity of a new PDMS/PSf Membrane Prepared at Different Conditions

Effect of water/solvent mixtures as coagulation medium with differing solvent content, coagulation bath temperature (CBT) and different coagulants on the gas permeation performance of polysulfone (PSf) membrane were investigated. The CO2/CH4 , H2/CO2 and CO2/N2 separation performance of membranes were studied by a constant pressure gas permeation experimental set up. The PSf membrane prepared at the CBT of 25°C (10-45°C range) showed the best gas separation performance with ideal selectivities of 43.9 and 39.8 for CO2/N2 and CO2/CH4 , respectively, and permeance of 21.5 GPU for CO2 at P=10bar. By increasing of the DMAc solvent into the gelation bath, ideal selectivities of CO2/CH4 and CO2/N2 have been reduced dramatically from 39.8 to 12.6 and 43.9 to 14.5, respectively at T=25°C and P=10bar. Using methanol as a coagulant resulted in less selective membrane compared with ethanol and water. But, the H2 and CO2 permeances were about 3 and 9 times more than those of ethanol and water coagulants, respectively. The coated membranes were given different heating temperature to investigate the suppression of undesirable CO2 plasticization. The membranes were stabilized against CO2 plasticization after heattreatment process.

Gas permeation properties of polyamide membrane prepared by interfacial polymerization

Interfacial polymerization technique has been widely employed to prepare reverse osmosis (RO) and nanofiltration (NF) membranes. The present study explores the possibility of preparing a polyamide membrane by interfacial polymerization and its utilization for the separation of CO2 and H2S from CH4. A novel ultraporous substrate of polysulfone (PSF) was prepared by phase inversion technique from a solution containing 18% PSF and 4% propionic acid in dimethyl formamide (DMF) solvent. Thin film composite (TFC) polyamide membrane was synthesized on PSF substrate from the reaction between meta-phenylene diamine in an aqueous media and isophthaloyl chloride in hexane. The membrane prepared was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) to study intermolecular interactions, crystallinity, thermal stability and surface morphology, respectively. Gas permeabilities of pure CO2, H2S, CH4, O2, and N2 gases were measured using the indigenously built permeation cell incorporated into a high-pressure gas separation manifold. At the feed pressure of 1 MPa, the membrane exhibited permeances of 15.2 GPU for CO2 and 51.6 GPU for H2S with selectivities of 14.4 and 49.1 for CO2/CH4 and H2S/CH4 systems, respectively. The observed N2 permeance of 0.95 GPU was close to that of CH4. The corresponding O2 permeance was 5.13 GPU with a reasonably high O2/N2 selectivity of 5.4. The effect of feed pressure on polyamide membrane performance was examined. Further, molecular dynamics (MD) simulations were employed to compute the cohesive energy density (CED), solubility parameter (δ) and sorption of CO2, H2S, CH4, O2, and N2 gases in polyamide membrane to corroborate theoretical study with experimentally determined gas transport properties.