Oxygen enrichment membrane

Considerable effort is being devoted to developing new polymeric membrane materials. A special type of oxygen-enrichment membrane has also been explored, which consists of a solvent immobilized within a microporous solid support (Fig. 7D). Dissolved in the liquid is a carrier... 

Fluorine compounds have an oxygen affinity. Accordingly, application of the fluorinated pitch-deposited film to an oxygen enrichment membrane material was examined. The compound was deposited on a porous substrate under the following deposition conditions. 

There are two properties to be improved in poly(TMSP) as oxygen-enrichment membrane i.e. the small P02/PN2 and the decrease of P02 with time. To raise the P02/PN2 ratio, modifications with F2 gas and CF4 plasma have been examined. Poly(dimethylsiloxane)... 

Under the tradename Copel LR Resin, silicone polycarbonates found applications ranging from oxygen enrichment membranes (including heart-lung machines), aerospace canopies and interlayers for bullet-proof glazing. They are prepared by the phosgenation of bisphenol A and chlorine terminated polydimethylsiloxane oligomer in methylene chloride with pyridine as a base acceptor (Eq. 7). 

Yamagiwa, K., Ohkawa, A. and Hirasa, O. 1994. Simultaneous Organic Carbon Removal and Nitrification by Biofilm Formed on Oxygen Enrichment Membrane. Journal of Chemical Engineering of Japan, 27,638-643. 

Hollow fiber-type oxygen enrichment membrane... 

Spiral-wound modules are much more commonly used in low pressure or vacuum gas separation appHcations, such as the production of oxygen-enriched air, or the separation of organic vapors from air. In these appHcations, the feed gas is at close to ambient pressure, and a vacuum is drawn on the permeate side of the membrane. Parasitic pressure drops on the permeate side of the membrane and the difficulty in making high performance hollow-fine fiber membranes from the mbbery polymers used to make these membranes both work against hollow-fine fiber modules for this appHcation. 

Vinyl neopentanoate is used in the preparation of adhesives and binders (44—46), optical materials for plastic lenses (47), gas permeable membranes for oxygen enrichment (48), and in coating appHcations (49,50). 

An internally-staged, gas-permeation module is used for the oxygen enrichment of air, using the flow arrangement shown in Fig. 5.206. Enrichment depends on differing membrane permeabilities for the oxygen and nitrogen to be separated. The permeation rates are proportional to the differences in component partial pressures. 

Oxygen Enrichment of Air. The U.S. produces approximately 15 million tons of oxygen from air each year (Ref. 12). Most of this production is accomplished cryogenically, and in large plants the cost is very low. Uses of oxygen in quantities of less than 10 tons per day, however, constitute a substantial share of this market. It is thought that membrane systems could economically enrich air at these smaller plant sizes. 

A comparison of the cost of oxygen-enriched air produced by membranes and by cryogenic separation shows that current membranes are generally uncompetitive. The only exception is for very small users in isolated locations, where the... 

Figure 8.29 Cost of oxygen-enriched air produced by membrane separation on an EP02 basis as a function of the oxygen permeability and oxygen/nitrogen selectivity of the membrane. The performance of today s best membranes is represented by the upper bound performance line from Robeson s plot (Figure 8.24) [35,47]. Reprinted from J. Membr. Sci. 62, B.O. Bhide and S.A. Stem, A New Evaluation of Membrane Processes for the Oxygen-enrichment of Air, p. 87. Copyright 1991, with permission from Elsevier...

Oxygen/nitrogen Oxygen enriched air Requires better membranes to become commercial. Size of ultimate market will depend on properties of membranes developed. Could be very large... 

R.W. Baker, I.C. Roman and H.K. Lonsdale, Liquid Membranes for the Production of Oxygen-Enriched Air-I. Introduction and Passive Liquid Membranes, J. Membr. Sci. 31, 15 (1987). 

Air O2/N2 Nitrogen-enriched air as inerting atmosphere Oxygen-enriched air for combustion enhancement Home medical oxygen enrichment for respiration therapy Practical to 99.5% Various degrees of enrichment up to 50% O2 Successful, but small market Need more selective membranes to reach higher nitrogen purity More selective membranes improves economics None... 

The high solubility and high stability of substituted polyacetylenes are the two most important properties which are not seen with polyacetylene. Consequently, stable membranes can be easily obtained by casting solutions of substituted polyacetylenes. This will greatly facilitate their application. Here, we refer to several functions of substituted polyacetylenes, which might be applied to oxygen enrichment of air, separation of ethanol-water mixtures, and so on. 

Membranes for gas separation have recently attracted much attention since membrane separation is one of promising energy-saving operations 104). For example, membranes for the oxygen enrichment of air, the isolation of helium, and the removal of C02 and S02 from natural gas are being intensively studied. The high gas permeability of substituted polyacetylenes, especially of poly[l-(triinethylsilyl)-l-propyne], is described below. 

---