CO\u3csub\u3e2\u3c/sub\u3e-Selective Membranes Containing Amino Groups

Novel compositions suitable for fabrication of CO2-selective membranes are disclosed. In one aspect, the present invention is directed to compositions comprising polyimide/polyamine blends and copolymers, and to compositions comprising interfacially polymerized polyamides. In another aspect this invention is directed to novel CO2-selective membranes comprising such polyimide/polyamine blends and copolymers, and to novel CO2-selective membranes comprising interfacially polymerized polyamides. In yet another aspect, the present invention is directed to a novel water-gas-shift (WGS) reactor comprising the novel CO2-selective membranes. Advantageously, the use of the novel CO2-selective membrane allows alteration of the normal WGS reaction equilibrium, shifting the reaction towards production of H2. Carbon dioxide on the high pressure, feed gas side of the membrane reactor reacts with the novel membranes of the present invention at the interface between the feed gas and the membrane. The reaction product permeates through the membrane to the interface between the feed gas and the low pressure side of the membrane, where the CO2 desorbs into the low pressure side and is removed

New facilitated transport membranes for CO2 capture and separation

We have synthesized new facilitated transport membranes comprising high-molecular-weight polyvinylamine (PVAm) as the fixed site carrier and aminoacid salt (e.g., piperazine glycinate (PG) or lithium glycinate (LG)) as the mobile carrier for facilitated transport of CO2. PVAm samples with different molecular weights were synthesized through free radical polymerization by adjusting the monomer concentration and initiator amount. The synthesized PVAm showed both a higher molecular weight and a higher solution viscosity than the commercially available PVAm (Lupamin® 9095 from BASF Corporation). The high viscosity of the PVAm solution at a low concentration allowed for the preparation of much thinner membranes. It could also help reducing penetration of the polymer solution into the pores of the substrate, further minimizing the mass transfer resistance. Consequently, a high CO2 permeance could be obtained from thin membranes with the thicknesses of 100 – 200 nm. The PVAm/PG blend solution was coated onto different substrates including polyethersulfone (PES) and polysulfone (PSf) substrates. Sodium dodecyl sulfate (SDS) surfactant was incorporated in the coating solution to improve the adhesion between the membrane layer and the substrate in some cases. The resultant PVAm/PG membranes exhibited a high CO2 permeance of about 1100 GPU and a high CO2/N2 mixed gas selectivity of more than 140 at the typical flue gas temperature of 57°C along with 17% water vapor, which is the desirable performance for post-combustion CO2 capture from coal-fired power plants

Oxidatively stable membranes for CO2 separation and H2 purification

CO2-selective facilitated transport membranes are well-known for providing remarkably high CO2/H2 selectivity along with high permeance at high temperatures (100 – 120oC). In some cases, it is desirable to use air as the sweep gas to enhance the driving force and membrane performance, and the membrane should be stable in the presence of oxygen. This work demonstrates the development of a new class of facilitated transport membranes containing quaternaryammonium hydroxide small molecules and quaternaryammonium hydroxide- and fluoride-containing polymers as mobile carriers and fixed-site carriers, respectively, for CO2 separation and H2 purification. The active nature of tetramethylquaternaryammonium hydroxide (TMAOH) as a mobile carrier was successfully demonstrated with the high CO2 permeance obtained by the TMAOH-containing membranes. However, the membrane performance was improved significantly by the incorporation of quaternaryammonium hydroxide- and/or fluoride-containing polymers in the membrane. The resulting hydroxide- and fluoride-containing membranes exhibited CO2 permeance \u3e 100 GPU and CO2/H2 selectivity \u3e 100 at 120oC using humid air as the sweep gas. The membrane composition was optimized, and the transport stability of the membrane was investigated. The membrane showed oxidatively stable during the 145-hour transport measurement at 120oC using air as the sweep gas. Furthermore, the effects of sweep steam content and membrane thickness were investigated. As the sweep steam content was increased (especially for steam content \u3e 50%), both CO2 permeance and CO2/H2 selectivity increased. As the membrane thickness was reduced from 15 µm to 2 µm, a sharp drop in the CO2/H2 selectivity was observed whereas the CO2 permeance did not seem to increase as prominently as the H2 permeance. In addition, the membrane was successfully scaled up using a roll-to-roll continuous membrane fabrication machine, and the scale-up membrane showed similar performance as the lab-scale membrane

Multiwalled carbon nanotube mixed matrix membranes containing amines for high pressure CO2/H2 separation

CO2-selective mixed matrix membranes capable of facilitated transport were synthesized for CO2/H2 separation at high pressures of at least 1.52 MPa and high temperatures above 373.15 K. A significant improvement in membrane stability was achieved by thoroughly dispersing multiwalled carbon nanotubes (MWNTs) as mechanical reinforcing fillers in a polyvinylalcohol matrix containing amines. With 2 wt% MWNTs incorporated, the membrane performance, including a CO2/H2 selectivity of 43 and a CO2 permeability of 836 Barrers (1 Barrer = 7.5 710 1211 cm3(STP) cm/(cm2 s kPa)), showed no change for 444 h (18.5 days) when operated at 1.52 MPa and 380.15 K. At the same conditions, the membrane containing 4 wt% acid-treated MWNTs also showed good stability. The membranes synthesized in this work are the first of this kind, displaying exceptional CO2/H2 separation performance and high tolerance to feed gas at high pressures and high temperatures. Potentially, they could be used in a stand-alone membrane unit for energy-efficient precombustion carbon capture from coal-derived syngas or in conjunction with water-gas-shift reaction for CO clean-up to produce high-purity H2 for fuel cells and to simultaneously capture CO2

Facilitated transport membranes containing amino-functionalized multi-walled carbon nanotubes for high-pressure CO<inf>2</inf> separations

In the present work, high-performance mixed matrix membranes containing amines have been developed for effective CO2 removal at high pressures (15\u201328 bar) and high temperatures (103\u2013121 \ub0C). The membrane was synthesized by compatibly embedding amino-functionalized multi-walled carbon nanotubes (AF-MWNTs) as mechanical reinforcing fillers in the crosslinked polyvinylalcohol-polysiloxane/amine blend. The surface functionalization of MWNTs allows strong coupling with the hydrophilic membrane matrix to form a nano-reinforced facilitated transport membrane, which achieved exceptional CO2 selectivity and permeability via the facilitated transport mechanism as well as attractive membrane stability via the incorporation of MWNTs. The synthesized membranes exhibited an average CO2 permeability of 957 Barrers coupled with high selectivities vs. H2 (56), CH4 (264), and N2 (384) at 107 \ub0C and 15 bar. The effects of AF-MWNT loading, high molecular weight species content, selective layer thickness, feed pressure, relative humidity, and temperature on membrane performance were thoroughly studied for a fundamental understanding of membrane properties. Furthermore, a mathematical model has been used to describe and explain the thickness-dependent CO2 transport behavior in the membrane. The combination of high CO2 permeability and good selectivities vs. CH4, H2, and N2, along with enhanced mechanical stability, makes the membrane a promising candidate for the gas separation applications at high pressures