The invention relates to a process and apparatus for separation of gas mixtures with reduced maintenance costs. The process and the apparatus consist of a feed stream separation stage (1), and a retentate separation stage (2), of which both are membrane separation stages, wherein the first retentate stream (7) is heated to temperature higher than the temperature of the feed stream (5), before it is introduced to the retentate separation stage (2), and the total capacity of the membranes used in the retentate separation stage (2) is higher than the total capacity of the membranes used in the feed stream stage (1).

A zeolite membrane complex includes a porous support, and a zeolite membrane formed on the support. The zeolite membrane includes a zeolite crystal phase constituted by a plurality of zeolite crystals, and a dense grain boundary phase, which is a region between the plurality of zeolite crystals. A density of at least part of the grain boundary phase is smaller than a density of the zeolite crystal phase. A width of the grain boundary phase is 2 nm or more and 10 nm or less. Accordingly, it is possible to realize high permeability and high separating performance, and high durability of the zeolite membrane.

This ionic liquid-containing laminate includes a porous layer having affinity with ionic liquids (C), said layer holding an ionic liquid-containing liquid (A) within voids therein, and a porous layer lacking affinity with ionic liquids (B). The porous layer having affinity with ionic liquids (C) may include an inorganic material (e.g., metal oxide particles having an average particle size of 0.001 to 10 μm on a number basis). The ionic liquid-containing liquid (A) may include an ionic liquid containing cations selected from ammonium, imidazolium and phosphonium cations, and anions selected from fluorine-containing anions, cyano-containing anions and amino acid-derived anions. The porous layer having affinity with ionic liquids (C) may include 1 to 100 volume parts of the ionic liquid-containing liquid (A) with respect to 100 volume parts of voids therein. The ionic liquid-containing laminate is easily formable, and is able to stably hold (or fix) the ionic liquid while maintaining said liquid in a liquid state.

Seed crystals are crystals of zeolite to be attached onto a support in production of a zeolite membrane complex including the support and a zeolite membrane formed on the support. The specific surface area of the seed crystals is not smaller than 10 m.sup.2/g and not larger than 150 m.sup.2/g. The strength obtained from a crystal component at a diffraction angle 2θ indicating a maximum peak in a range of diffraction angle 2θ from 12° to 25° in an X-ray diffraction pattern obtained by emitting X-ray to the seed crystals is not less than once and not more than 30 times that obtained from an amorphous component. It is thereby possible to improve adherence of the seed crystals to the support.

A feed containing methane and nitrogen gas is processed in a three-stage membrane system, each stage of which is selective for methane over nitrogen. The methane enriched permeate from the first stage is removed as product gas. The methane-depleted residue from the second stage is purified in second and third cascaded stages to provide second and third permeates and second and third residues. The third stage permeate is recycled to the feed.

A free standing liquid membrane is disclosed that can selectively separate objects based on the kinetic energy value of the objects such that either an object having a first kinetic energy value can pass through the free standing liquid membrane while retaining the membrane and/or an object having a second kinetic energy value is prevented from passing through the membrane while retaining the membrane. Advantageously, the free standing liquid membrane can remain intact for seconds to hours with multiple objects passing through the membrane.

A method for producing a gas separation membrane includes a step of leaving a dispersion liquid to stand still, the dispersion liquid being obtained by mixing zeolite microcrystalline bodies formed from MFI zeolite and graphene oxide with pure water, and covering the periphery of the zeolite microcrystalline bodies with the graphene oxide; a step of drying the dispersion liquid after being left to stand to obtain a powder; a step of subjecting the powder to a reduction treatment of the graphene oxide by means of heating; and a step of pressure-forming the powder after the reduction treatment so as to be formed into a membrane form.

Provide are an ionic liquid composition for a carbon dioxide separation membrane, a carbon dioxide separation membrane retaining the composition in voids, and a carbon dioxide concentration apparatus provided with the carbon dioxide separation membrane that can be used to separate carbon dioxide from high partial pressure to low partial pressure. The permeability of CO.sub.2 and CO.sub.2 selectivity ratio of the carbon dioxide separation membrane can be improved, and carbon dioxide from high partial pressure to a low partial pressure of 1 kPa or lower can be selectively separated and recycled by using an ionic liquid composition prepared by combining: an ionic liquid (I) that is an aminium having one or more primary or secondary amino groups and an ethylenediamine or propylenediamine backbone in the cation; and an ionic liquid (II) in which the cation has no primary or secondary amino group and the anion is an oxoacid anion.

New carbon nanomaterials, preferably titanium carbide-derived carbon (CDC) nanoparticles, were embedded into a polyamide film to give CDC/polyamide mixed matrix membranes by the interfacial polymerization reaction of an aliphatic diamine, e.g., piperazine, and an activated aromatic dicarboxylate, e.g., isophthaloyl chloride, supported on a sulfone-containing polymer, e.g., polysulfone (PSF), layer, which is preferably previously prepared by dry/wet phase inversion. The inventive membranes can separate CO.sub.2 (or other gases) from mixtures of CO.sub.2 and further gases, esp. CH.sub.4, based upon the generally selective nanocomposite layer(s) of CDC/polyamide.

A process for preparing a microcapillary carbon molecular sieve membrane may include extruding a polyvinylidene chloride polymer to a thickness from 10 μm to 1,000 μm to form an extruded polymeric microcapillary film, wherein the extruded polymeric microcapillary film comprises a first end, a second end, and one or more microcapillaries extending from the first end to the second end; pre-treating the extruded polymeric microcapillary film at a temperature from 100° C. to 200° C. for a time from 1 hour to 48 hours to form a pre-treated polymeric microcapillary film; and pyrolizing the pre-treated polymeric microcapillary film at a temperature from 200° C. to 1,500° C. for a time from 15 minutes to 5 hours to form the microcapillary carbon molecular sieve membrane.