In the last years membrane processes for gas separation are gaining a larger acceptance in industry and in the market are competing with consolidated operations such as pressure swing absorption and cryogenic distillation. The key for new applications of membranes in challenging and harsh environments (e.g., petrochemistry) is the development of new tough, high performance materials. The modular nature of membrane operations is intrinsically fit for process intensification, and this versatility might be a decisive factor to impose membrane processes in most gas separation fields, in a similar way as today membranes represent the main technology for water treatment. This review highlights the most promising areas of research in gas separation, by considering the materials for membranes, the industrial applications of membrane gas separations, and finally the opportunities for the integration of membrane gas separation units in hybrid systems for the intensification of processes.

Membrane Gas Separation: A Review/State of the Art

3.2. Preparation 4090 3.3. Intermediate Layers 4090 3.4. Support 4090 3.5. Modification 4091 3.5.1. Silica Membrane Modification 4091 3.5.2. Membrane Structure Modification 4092 3.6. Operational Stability 4092 4. Zeolite Membranes 4092 4.1. Membrane Growth Methods 4093 4.2. Permeation and Gas Transport 4093 4.3. Defect Site Diffusion/Nonzeolitic Pores 4094 4.4. Thin Films 4094 4.5. Zeolite Membrane Modification 4094 4.6. CO2 Sequestration in H2 Separations 4095 4.7. Manufacturing 4095 5. Carbon-Based Membranes 4096 5.1. Carbon Membrane Preparations 4097 5.2. Carbon Membrane Post-treatment 4097 5.3. Carbon Membrane Module Construction 4097 5.4. Selective Surface Flow Membranes 4097 5.5. Disadvantages of Carbon Membranes 4098 5.6. Molecular Sieving Carbon Membranes 4098 5.7. Carbon Nanotubes 4099 6. Polymer Membranes for H2 Separations 4100 6.1. Dense Polymeric Membranes 4100 6.2. Hydrogen Selective Polymeric Membranes 4101 6.3. H2 versus CO2 Selective Polymeric Membranes 4103

Membranes for hydrogen separation.

CO2-selective polymeric membranes containing amines in crosslinked poly(vinyl alcohol)

Facilitated transport of CO2 in novel PVAm/PVA blend membrane

With the growing concern about global warming placing greater demands on improving energy efficiency and reducing CO2 emissions, the need for improving the energy intensive, separation processes involving CO2 is well recognized. The US Department of Energy estimates that the separation of CO2 represents 75% of the cost associated with its separation, storage, transport, and sequestration operations. Hence, energy efficient, CO2 separation technologies with improved economics are needed for industrial processing and for future options to capture and concentrate CO2 for reuse or sequestration. The overall goal of this review is to foster the development of new adsorption and membrane technologies to improve manufacturing efficiency and reduce CO2 emissions. This study focuses on the power, petrochemical, and other CO2 emitting industries, and provides a detailed review of the current commercial CO2 separation technologies, i.e., absorption, adsorption, membrane, and cryogenic, an overview of the em...

State-of-the-art Adsorption and Membrane Separation Processes for Carbon Dioxide Production from Carbon Dioxide Emitting Industries

The facilitated transport of CO2 through ion exchange membranes containing organic amine counterions was studied. Steady state CO2 fluxes were measured from pure gas streams and mixtures with CH4. Facilitation factors for CO2 up to 26.7 were calculated from transport data. Transport measurements were binary mixtures of CO2 and CH4 yielded ratios of CO2 flux to CH4 flux ranging from 29.0 to 264. Conversion of flux ratios to permeabilities yielded separation factors up to 551 for CO2 over CH4, which are compared to literature data for polymeric membranes. The transport data support a mobile, reactive-carrier facilitated transport mechanism with a carbamate zwitterion complex. Effective diffusivities for CO2 and the carrier-gas complex were determined from transport data. A reaction equilibrium model predicted facilitation factors that were in very good agreement with experimental values. Potential applications are also discussed.

G. M. Ginley

Papers

Facilitated transport of CO2 in ion exchange membranes