Carbon molecular sieve pretreatment

Tin PS, Chung T-S, Hill AJ (2004) Advanced fabrication of carbon molecular sieve membranes by nonsolvent pretreatment of precursor polymers. Ind Eng Chem Res 43 (20) 6476-6483... 

Each of the beds contain two layers of molecular sieve. After leaving the air blower skid, the airstream enters the bottom of a vessel and passes through the pretreatment layer of molecular sieve. The pretreatment layer removes water vapor and carbon dioxide from the airstream. Both of these are feed stream contaminants that can damage the main bed permanently if allowed to pass beyond the guard layer. 

RO membranes including polymeric (PA-TFC membrane) and molecular sieve zeolite membranes were investigated for ion removal from the water produced at oil field and coal bed methane sites by a cross-flow RO process [78]. Pretreatments including NF and adsorption by active carbon were implemented. The study revealed that (1) most of permeation tests lasted only 3 months due to severe fouling, (2) multistage pretreatment is crucial to extend membrane life, and (3) only NF treatment could extend the membrane life to 6 months. 

From Na and Other Inert Gases. Adsorption isotherms for PH3 in mixtures with Na at 293 K were determined on various types of silica gel, activated carbon, and zeolites [3]. The removal from inert gases can be achieved by contact with silica gels [4], zeolites [4, 5], or activated carbon impregnated with CH3CN, picric acid, or maleic acid [4]. The adsorption on activated carbon pretreated with iodine compounds and sulfates or nitrates of ammonium and metals was used in [6]. Cu- or Ag-modified molecular sieves [7] or a soda-lime bed, which may contain nitrite salts, were also used as adsorbents [8]. The removal of PH3 by an aqueous solution of LiCl and HCIO4 was mentioned [9]. Its removal by oxidative methods is described in Section 1.3.1.5.4, p. 222. 

The feed gas preparation section typically includes refrigeration and molecular sieve adsorption for water removal and activated carbon adsorption for removal of sulfur compounds to acceptable levels. The pretreated feed gas enters the bottom of the absorber where it is contacted countercurrently with the active solvent. Gas leaving the top of the absorber, with a residual carbon monoxide concentration in the ppm range, is treated for solvent recovery. 

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