Gas and vapor separation

Commercial PDMS membrane modules for the separation of organics from gaseous streams in different processes are Usted in Table 20.3 [57,58]. 

Module type Membrane geometry Membrane Module (mVm ) 

Polyvinyl chloride production VCM monomer recovery from vent gas 99% of VCM 

Large fuel terminals Gasoline vapor recovery from air 95-99% of hydrocarbons 

Polyolefin production Hydrocarbon recovery from resin degassing 91% of hydrocarbon 50% of 

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Zeolite/polymer mixed-matrix membranes prepared from crosslinked polymers and surface-modified zeolite particles offered both outstanding separation properties and swelling resistance for some gas and vapor separations such as purification of natural gas. Hillock and coworkers reported that crosslinked mixed-matrix membranes prepared from modified SSZ-13 zeolite and 1,3-propane diol crosslinked polyimide (6FDA-DAM-DABA) synthesized from 2,2 -feis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, p-dimethylaminobenzylamine-and 3,5-diaminobenzoic acid displayed high CO2/CH4 selectivities of up to 47 Barrer and CO2 permeabilities of up to 89 Barrer under mixed gas testing conditions [71]. Additionally, these crosslinked mixed-matrix membranes were resistant to CO2 plasticization up to 450 psia (3100kPa). 

Yampol skii, Y., Pinnau, I. and Freeman, B.D. (eds) (2006) Materials Science of Membranes for Gas and Vapor Separation, John Wiley, Chichester. 

Valuable savings are possible even using available gas and vapor-separation membrane units, while aggressively pursuing development of nonaqueous RO and its larger energy payoffs over the next decade. Vapor-separation processes are operationally similar to gas-separation units but often use a moderate vacuum downstream, depending upon the vapor pressure of the components at the feed temperature. 

Various membrane operations are available today for a wide spectrum of industrial applications. Microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), gas and vapor separation (GS, VS), pervaporation (PV), dialysis (D), electrodialysis (ED) and membrane contactors (MCs) are only some of the best-known membrane unit operations. 

Pinnau, I., ed. (1999). Polymer Membranes for Gas and Vapor Separation Chemistry and Materials Science, ACS Symposium Series, 733, American Chemical Society, Washington, DC. 

Basic mechanisms involved in gas and vapor separation using ceramic membranes are schematized in Figure 6.14. In general, single gas permeation mechanisms in a porous ceramic membrane of thickness depend on the ratio of the number of molecule-molecule collisions to that of the molecule-wall collisions. In membranes with large mesopores and macropores the separation selectivity is weak. The number of intermolecular collisions is strongly dominant and gas transport in the porosity is described as a viscous flow that can be quantified by a Hagen-Poiseuille type law ... 

In a general way, most of ceramic membrane modules operate in a cross-flow filtration mode [28] as shown in Figure 6.18. However, as discussed hereafter, a dead-end filtration mode may be used in some specific applications. Membrane modules constitute basic units from which all sorts of filtration plants can be designed not only for current liquid applications but also for gas and vapor separation, membrane reactors, and contactors, which represent the future applications of ceramic membranes. In liquid filtration, hydrodynamics in each module can be described as one incoming flow on the feed side gf, which results in two... 

Figure 9.2 The four possible general mechanisms for selective-membrane-based gas and vapor separations [3]. Reproduced with permission of AlChE.

Basic mechanisms involved in gas and vapor separation using ceramic membranes are schematized in Figure 9.14. 

To protect intellectual property investments, membrane companies often patent families of polymers. For example, in the gas and vapor separation area, a family of polyimides were patented by DuPont [20] while their competitors Dow and Air Products patented families of polycarbonates [21] and polyarylates [22], respectively. 

Table 7.5 Mixed gas-permeation properties of PTMSP and PMP. Feed 2% butane in methane, feed pressure 10 bar, permeate pressure atmospheric, temperature 25 °C. From I. Pinnau et al. In Polymer Membranes for Gas and Vapor Separation, ACS Symposium Series 733 (1999), 56-67.

B.D. Freeman, I. Pinnau (Eds.), Polymer membranes for gas and vapor separation, ACS Symposium Series 733, Washington 1999. 

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