Abstract:
Disclosed herein are asymmetric multilayer carbon molecular sieve ("CMS") hollow fiber membranes and processes for preparing the membranes. The processes include simultaneously extruding a core dope containing a polymer and suitable nanoparticles, a sheath dope, and a bore fluid, followed by pyrolysis of the extruded fiber.
Abstract:
Methods of making inorganic membranes, for example, methods of making gamma-alumina inorganic membranes which can be useful for, for example, molecular level gas separations and/or liquid filtration are described.
Abstract:
Prepare a carbon molecular sieve membrane from a polyimide (e.g., a 6FDA/BPDA-DAM polyimide) that has a glass transition temperature of at least 400° C and includes a bridged phenyl compound for separation of hydrogen and ethylene from one another whether present as a pure mixture of hydrogen and ethylene or as components of a cracked gas. Preparation comprises two sequential steps a) and b). In step a), place a membrane fabricated from defect-free fibers of the polyimide in contact with an oxygen-containing atmosphere under conditions of time and temperature sufficient to produce a pre-oxidized and pre-carbonized polymeric membrane that is insoluble in hot (110 C) n-methylpyrolidone and at least substantially free of substructure collapse. In step b) pyrolyze the pre-oxidized and pre-carbonized membrane in the presence of a purge gas under conditions of time and temperature sufficient to yield a carbon molecular sieve membrane that has at least one of a hydrogen permeance and a hydrogen/ethylene selectivity greater than that of a carbon molecular sieve membrane prepared from the same membrane using only pyrolysis as in step b).
Abstract:
Hybrid membranes based on crystalline titanium dioxide containing fluorine atoms within the crystalline lattice comprising atoms of titanium and oxygen are described; these hybrid membranes are particularly suitable for the production of fuel cells and electrolysers. The titanium dioxide contained in them may be produced by a process comprising the following stages: (a) a titanium ore is reacted with a NH 4 HF 2 aqueous solution of; (b) the aqueous dispersion so obtained is filtered with subsequent separation of a solid residue and an aqueous solution containing titanium salts; (c) the aqueous solution so obtained is subjected to hydrolysis, said hydrolysis comprising a first stage at pH 6.5-8.0 and a second stage at pH 9-11; (d) the aqueous dispersion thus obtained is filtered and the solid residue is subjected to pyrohydrolysis at a maximum temperature of approximately 500°C, preferably approximately 450°C.
Abstract:
A method of manufacturing such gas separation membrane system that includes applying to a surface of a porous substrate a layer of a nanopowder of a gas-selective metal and, thereafter, heat-treating the resultant surface treated porous substrate to yield a heat-treated and surface-treated porous substrate suitable for use as a gas separation membrane system.
Abstract:
A gas separation membrane and a method of manufacturing such gas separation membrane that comprises a porous substrate treated with a layer of metal-coated inorganic oxide particles and with the layer of such metal-coated inorganic oxide particles being coated with an overlayer of a gas-selective material.
Abstract:
Methods for preparing a gas separation membrane system can include depositing a gas-selective membrane layer upon a surface of a tubular porous support, annealing the gas-selective membrane layer to form an annealed gas-selective membrane layer, polishing the annealed gas-selective membrane layer under a controlled polishing condition to form an abraded membrane surface, depositing another gas-selective membrane layer upon the abraded membrane surface of the tubular porous support, and successively iterating the annealing, polishing and depositing operations until a leak-tight membrane system is formed. The controlled polishing condition comprises utilizing a rotary fibrous buff that includes a plurality of abrasive particles adhered to a fibrous support with a polymeric binder.
Abstract:
Presented is a method for preparing a gas separation membrane system. This method involves depositing a membrane layer of gas-selective metal upon a tubular porous support followed by annealing the resulting layer of gas-selective metal. The resulting annealed membrane layer of gas-selective material is polished under a controlled polishing condition with an abrading medium that includes a structured abrasive article comprising a backing having bonded thereto an abrasive layer comprising a plurality of shaped abrasive composites that comprise abrasive grains dispersed in a polymeric binder. Another layer of gas-selective metal is then deposited upon the tubular porous support. The cycle of annealing, polishing and depositing is repeated through one or more cycles until a leak-tight membrane system is provided.
Abstract:
Carbon molecular sieves (CMS) membranes having improved thermal and/or mechanical properties are disclosed herein. In one embodiment, a carbon molecular sieve membrane for separating a first and one or more second gases from a feed mixture of the first gas and one or more second gases comprises a hollow filamentary carbon core and a thermally stabilized polymer precursor disposed on at least an outer portion of the core. In some embodiments, the thermally stabilized polymer precursor is created by the process of placing in a reaction vessel the carbon molecular sieve membrane comprising an unmodified aromatic imide polymer, filling the reaction vessel with a modifying agent, and changing the temperature of the reaction vessel at a temperature ramp up rate and ramp down rate for a period of time so that the modifying agent alters the unmodified aromatic imide polymer to form a thermally stabilized polymer precursor.