A porous filter includes a porous laminate in which a plurality of biaxially stretched porous sheets made of PTFE are stacked. The Gurley number G and the bubble point B (kPa) of the porous laminate satisfy the following expressions (1) and (2):

log G>3.710.sup.3B0.8(1)

log G<4.910.sup.3B+0.45(2).

Asymmetric membrane structures are provided that are suitable for various types of separations, such as separations by reverse osmosis. Methods for making an asymmetric membrane structure are also provided. The membrane structure can include at least one polymer layer. Pyrolysis can be used to convert the polymer layer to a porous carbon structure with a higher ratio of carbon to hydrogen.

Asymmetric membrane structures are provided that are suitable for various types of separations, such as separations by reverse osmosis. Methods for making an asymmetric membrane structure are also provided. The membrane structure can include at least one polymer layer. Pyrolysis can be used to convert the polymer layer to a porous carbon structure with a higher ratio of carbon to hydrogen.

Asymmetric membrane structures are provided that are suitable for hydrocarbon reverse osmosis of small hydrocarbons. Separation of para-xylene from ortho- and meta-xylene is an example of a separation that can be performed using hydrocarbon reverse osmosis. Hydrocarbon reverse osmosis separations can be incorporated into a para-xylene isomerization and recovery system in a variety of manners.

Provided is an acidic gas-containing gas treatment separation membrane in which an intermediate layer provided on a support member is optimized, and which can treat and separate a gas mixture containing acidic gas and methane gas and/or nitrogen gas into the gas components, and thereby efficiently obtain acidic gas or methane gas and/or nitrogen gas. The acidic gas-containing gas treatment separation membrane includes an inorganic porous support member, an intermediate layer containing a polysiloxane network structure material and formed on a surface of the inorganic porous support member, and a separation layer containing a hydrocarbon group-containing polysiloxane network structure material and formed on the intermediate layer.

A spiral separation membrane element includes a water collection tube; a separation membrane wound around the water collection tube, having a feed-side surface and a permeate-side surface, and including a band-shaped region on at least one end of the feed-side surface in an axial direction of the water collection tube; and a channel material fused to the band-shaped region.

A method for producing a porous polyimide film comprises: forming a first un-burned composite film wherein the first film is formed on a substrate using a first varnish that contains (A1) a polyamide acid or a polyimide and (B1) fine particles at a volume ratio (A1):(B1) of from 19:81 to 45:65; forming a second un-burned composite film wherein the second film is formed on the first film using a second varnish that contains (A2) a polyamide acid or a polyimide and (B2) fine particles at a volume ratio (A2):(B2) of from 20:80 to 50:50 and has a lower fine particle content ratio than the first varnish; burning wherein an un-burned composite film composed of the first film and the second film is burned, thereby obtaining a polyimide-fine particle composite film; and a fine particle removal step wherein the fine particles are removed from the polyimide-fine particle composite film.

An ion exchange membrane has multiple layers of ionic polymers which each contain substantially different chemical compositions. i.e. varying side chain lengths, varying backbone chemistries or varying ionic functionality. Utilizing completely different chemistries has utility in many applications such as fuel cells where for example, one layer can help reduce fuel crossover through the membrane. Or one layer can impart substantial hydrophobicity to the electrode formulation. Or one layer can selectively diffuse a reactant while excluding others. Also, one chemistry may allow for impartation of significant mechanical properties or chemical resistance to another more ionically conductive ionomer. The ion exchange membrane may include at least two layers with substantially different chemical properties.

The present invention relates to a technology for manufacturing a nanocomposite membrane comprising a graphene oxide coating layer with a thickness of 1 nm to 50 nm, which is formed on various supports and has nanopores, and a reduced graphene oxide nanocomposite membrane, and applying the membranes to gas separation. The graphene oxide nanocomposite membrane for gas separation of the present invention has excellent gas permeability and selectivity at the same time, and especially, excellent hydrogen gas permeability and hydrogen gas selectivity compared with carbon dioxide, and the reduced graphene oxide nanocomposite membrane has remarkably enhanced hydrogen gas permeability and hydrogen gas selectivity compared with carbon dioxide, and thus the membranes are applicable as a gas separation membrane in an industrial field involving a hydrogen separation process. Furthermore, a graphene oxide nanocomposite membrane for gas separation can be provided, in which strong binding force between a support and a graphene oxide coating layer is induced by modifying surfaces of various supports and thus the graphene oxide coating layer is not easily delaminated.

A method for preparing a homogeneous braid-reinforced (HMR) PPTA hollow fiber membrane combines PPTA hollow tubular braids with PPTA surface separation layer. The method includes following steps of: (1) preparing the PPTA hollow tubular braids, wherein the PPTA hollow tubular braids which are made from PPTA filament yarns are woven by a two-dimensional braided method, the outer diameter of the PPTA tubular braids is 1-2 mm; (2) preparing the PPTA casting solution as the surface separation layer, wherein the 1-3 wt % PPTA resin, 0-2 wt % inorganic particles and 10-20 wt % pore-forming agents are mixed into 75-89% inorganic acid solvent, stirred for 1-3 hours at 70 C.-90 C. to form homogeneous and transparent casting solution; and (3) preparing reinforced PPTA hollow fiber membrane, wherein the casting solution as the surface separation layer is evenly coated on the surfaces of the PPTA hollow tubular braids through spinneret, and they are immersed in a coagulation bath for solidified formation.