Mixed gas plasticization phenomena in asymmetric membranes

This thesis describes the thorough investigation of mixed gas transport behavior of asymmetric membranes in the separation of feed streams containing plasticizing gases in order to gain more insights into the complicated behavior of plasticization. To successfully\ud employ gas separation membranes in (new) applications containing plasticizing feed streams, membranes with improved stability have to be developed. Fundamental knowledge on the complicated behavior of plasticization in the separation of these gas streams using asymmetric membranes is an important issue in this development

Influence of Pyrolysis Parameters on the Performance of CMSM

Carbon hollow fiber membranes have been prepared by pyrolysis of a P84/S-PEEK blend. Proximate analysis of the precursor was performed using thermogravimetry (TGA), and a carbon yield of approximately 40% can be obtained. This study aimed at understanding the influence of pyrolysis parameters—end temperature, quenching effect, and soaking time—on the membrane properties. Permeation experiments were performed with N2, He, and CO2. Scanning electron microscopy (SEM) has been done for all carbon hollow fibers. The highest permeances were obtained for the membrane submitted to an end temperature of 750°C and the highest ideal selectivities for an end temperature of 700°C. In both cases, the membranes were quenched to room temperatur

Super selective membranes in gas-liquid membrane contactors for olefin/paraffin separation

In the present paper, selective composite membranes containing sulfonated poly(ether ether ketone) (SPEEK) layers on top of a hydrophobic, polypropylene support are applied as absorber and desorber in a gas¿liquid membrane contactor system for the separation of paraffins and olefins. The water present in the absorption liquid swells the hydrophilic polymer sufficiently, making the membranes olefin-selective. As a result, even at high liquid velocities where the membrane determines the selectivity of the process, high selectivities can be obtained in combination with high productivities. Continuous contact between the absorption silver nitrate solution and the SPEEK layer prevents the layer from drying out and subsequent loss of selectivity. Previously, unknown high ethylene/ethane selectivities (>2700) are obtained in combination with reasonable ethylene productivities (7.6×10¿10 cm3/cm2 s Pa (1×10¿6 cm3/cm2 s cmHg))

Olefin-selective membranes in gas-liquid membrane contactors for olefin/paraffin separation

The application of olefin-selective membrane materials in gas-liquid membrane contactors for the separation of paraffins and olefins using a silver nitrate solution as the absorption liquid turned out to be very successful, especially with respect to the olefin/paraffin selectivity obtainable. Composite hollow-fiber membranes with a top layer of a highly permeable block copolymer of poly(ethylene oxide) (PEO) and poly(butylene terephthalate) (PBT) are prepared and applied in a gas-liquid membrane contactor for the separation of paraffins and olefins using a silver nitrate solution as the absorption liquid. The water present in the absorption liquid swells the hydrophilic polymer sufficiently. This prevents drying out of the layer and enables the partitioning of silver ions into the polymer matrix, making it olefin-selective. Ethylene permeabilities obtained are comparable to the values found for membranes with nonselective, elastomeric top layers (40-50 barrer). Selectivities, however, are more than 20 times higher. Independent of the liquid flow rate, a selectivity of 165 is obtained for PEO/PBT-coated membranes. This makes the application of olefin-selective membranes in a membrane contactor for olefin/paraffin separations very attractive

CO2 permeation properties of poly(ethylene oxide)-based segmented block copolymers

This paper discusses the gas permeation properties of poly(ethylene oxide) (PEO)-based segmented block copolymers containing monodisperse amide segments. These monodisperse segments give rise to a well phase-separated morphology, comprising a continuous PEO phase with dispersed crystallised amide segments. The influence of the polyether phase composition and of the temperature on the permeation properties of various gases (i.e., CO2, N2, He, CH4, O2 and H2) as well as on the pure gas selectivities were studied in the temperature range of −5 °C to 75 °C. The CO2 permeability increased strongly with PEO concentration, and this effect could partly be explained by the dispersed hard segment concentration and partly by the changing chain flexibility. By decreasing the PEO melting temperature the low temperature permeabilities were improved. The gas transport values were dependant on both the dispersed hard segment concentration and the polyether segment length (length between crosslinks). The gas selectivities were dependant on the polyether segment length and thus the chain flexibility