Patent Publication Number: US-2015087869-A1

Title: Capture of trifluoromethane using molecuar sieves

Description:
This application claims priority under 35 U.S.C. §119(e) from, and claims the benefit of, U.S. Provisional Application No. 61/708,651 filed 2 Oct. 2012, which is by this reference incorporated in its entirety as a part hereof for all purposes. 
    
    
     TECHNICAL FIELD 
     The invention relates to the field of greenhouse gas emission reduction. More specifically, the invention provides a method for capturing trifluoromethane from a gaseous mixture using molecular sieves, such as zeolites or activated carbon. 
     BACKGROUND 
     Chlorodifluoromethane (R-22) is widely used as a propellant and refrigerant, and is also a versatile intermediate in the synthesis of organofluorine compounds. Chlorodifluoromethane is typically prepared by reacting chloroform with HF. A by-product of this reaction is trifluoromethane (R-23), which has a very high global warming potential (i.e., GWP=11,700 relative to CO 2  GWP=1). Therefore, methods to capture the trifluoromethane produced in the chlorodifluoromethane manufacturing process are needed to prevent its release into the atmosphere. 
     Zeolites are high capacity, selective sorbents that have been widely used for capturing a variety of chemical compounds, including hydrofluorocarbons. For example, Yoshida et al. (JP 2011194337 A) describe a method for removing hydrofluorocarbons such as CH 3 F and/or CHF 3  from the exhaust gas discharged from the manufacturing process of a semiconductor or a liquid crystal using a binder-less X type zeolite. Corbin et al. (U.S. Pat. No. 5,523,499) describe a process for purifying a hexafluoroethane product containing CClF 3  and/or CHF 3  impurities using zeolites. Additionally, Thomas et al. (U.S. Pat. No. 7,597,744) describe the use of molecular sieves to reduce the amount of trifluoromethane present in a mixture of trifluoromethane and trifluoroiodomethane. However, zeolites have not been used to capture trifluoromethane produced in the chlorodifluoromethane manufacturing process. 
     SUMMARY 
     In one embodiment, there is provided herein, a method for capturing trifluoromethane from a gaseous mixture comprising the step of: contacting the gaseous mixture with at least one molecular sieve at a pressure of about 0.1 MPa to about 4.8 MPa and a temperature of about 273 K to about 323 K for a period of time sufficient for the molecular sieve to remove at least a portion of the trifluoromethane; 
     wherein:
         (a) the gaseous mixture is a vent stream from a chlorodifluoromethane manufacturing process, said gaseous mixture consisting essentially of trifluoromethane and nitrogen, oxygen, argon, and/or carbon dioxide; and   (b) the molecular sieve has a pore opening of at least about 5 Angstroms and has a Sanderson electronegativity of less than or equal to about 2.75.       

    
    
     DETAILED DESCRIPTION 
     As used above and throughout the description of the invention, the following terms, unless otherwise indicated, shall be defined as follows: 
     The term “gaseous mixture”, as used herein, refers to a mixture of gases in a vent stream from a chlorodifluoromethane manufacturing process. The gaseous mixture consists essentially of trifluoromethane and nitrogen, oxygen, argon, and/or carbon dioxide. The gaseous mixture may also contain small amounts of chlorodifluoromethane and/or HCl, typically less than 5 wt %. 
     The terms “capture” and “capturing”, as used herein, refer to the removal of at least a portion of the trifluoromethane from a gaseous mixture by sorption by a molecular sieve, such as a zeolite. 
     Disclosed herein is a method for capturing trifluoromethane from a gaseous mixture in a vent stream from a chlorodifluoromethane manufacturing process using molecular sieves, such as zeolites or activated carbon. The method is useful for reducing emissions of trifluoromethane, which has a high global warming potential (i.e., GWP=11,700 relative to CO 2  GWP=1). 
     Molecular Sieves 
     Molecular sieves are well known in the art and are defined by R. Szosak [ Molecular Sieves Principles of Synthesis and Identification , Van Nostrand Reinhold, NY (1989), page 2]. Zeolites, a class of molecular sieves, are crystalline, highly porous materials. They can be generically described as complex aluminosilicates characterized by a three-dimensional pore system. The zeolite framework structure has corner-linked tetrahedra with Al or Si atoms at centers of the tetrahedra and oxygen atoms at the corners. Such tetrahedra are combined in a well-defined repeating structure comprising various combinations of 4-, 6-, 8-, 10-, and 12-membered rings. The resulting framework structure is one of regular channels and cages, which has a pore network that is useful for separation or purification purposes. The size of pore opening is critical to the performance of zeolite in separation or purification applications, since this characteristic determines whether molecules of certain size can enter and exit the zeolite pore system. 
     The size of the pore opening that controls access to the interior of the zeolites is determined not only by the geometric dimensions of the tetrahedra forming the pore opening, but also by the presence or absence of ions in or near the pore. For example, in the case of zeolite A, access can be restricted by monovalent ions, such as Na +  or K + , which are situated in or near 8-member ring openings as well as 6-member ring openings. Access can be enhanced by divalent ions, such as Ca 2+ , which are situated only in or near 6-member ring openings. Thus, the potassium and sodium salts of zeolite A exhibit pore openings of about 3 Angstroms and about 4 Angstroms respectively, whereas the calcium salt of zeolite A has a pore opening of about 5 Angstroms. 
     The Sanderson electronegativity model (see R. T. Sanderson, “Chemical Bonds and Bond Energy”, 2 nd  ed., Academic Press, New York, 1976; R. T. Sanderson, “Electronegativity and Bond Energy”, J.  Amer. Chem. Soc.  1983, 105, 2259-2261; W. J. Mortier, “Zeolite Electronegativity Related to Physicochemical Properties”,  J. Catal.  1978, 83, 138-145) furnishes a useful method for classifying inorganic molecular sieves based on their chemical composition. In accordance with this invention the preferential sorption of trifluoromethane by molecular sieves can be correlated with their intermediate electronegativity (i.e., their S int , the geometric mean of the electronegativities) as determined by the Sanderson method based upon chemical composition. According to Barthomeuf (D. Barthomeuf, “Acidity and Basicity in Zeolites”, In Catalysis and Adsorption in Zeolites, G. Ohlmann et al., eds., Elsevier (1991), pages 157-169), an apparent S int  break point between acidity and basicity is at about 3.5 (based on Sanderson (1976)) or 2.6 (based on Sanderson (1983)). In other words, generally, zeolites with S int  less than about 2.6 (based on Sanderson (1983) tend to exhibit base properties, while those with S int  greater than about 2.6 are acidic. Example S int  values are provided in Table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Intermediate Sanderson Electronegativities 
               
               
                 for Selected Molecular Sieves 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Approximate 
                   
               
               
                   
                 Molecular Sieve 
                 Composition 
                 S int   
               
               
                   
                   
               
               
                   
                 Zeolite 5A (Ca 2+ ) 
                 Ca 4 Na 4 Al 12 Si 12 O 48   
                 2.56 
               
               
                   
                 Zeolite A (Sr 2+ ) 
                 Sr 4 Na 4 Al 12 Si 12 O 48   
                 2.52 
               
               
                   
                 Zeolite A (Ba 2+ ) 
                 Ba 4 Na 4 Al 12 Si 12 O 48   
                 2.51 
               
               
                   
                 Zeolite A (Zn 2+ ) 
                 Zn 4 Na 4 Al 12 Si 12 O 48   
                 2.67 
               
               
                   
                 Zeolite A (Cd 2+ ) 
                 Cd 4 Na 4 Al 12 Si 12 O 48   
                 2.66 
               
               
                   
                 Zeolite LSX 
                 Na 73 K 22 Al 95 Si 97 O 384   
                 2.31 
               
               
                   
                 Zeolite 13X 
                 Na 86 Al 86 Si 106 O 384   
                 2.38 
               
               
                   
                 Zeolite NaY 
                 Na 56 Al 56 Si 136 O 384   
                 2.58 
               
               
                   
                 Zedolite HY 
                 H 56 Al 56 Si 136 O 384   
                 2.95 
               
               
                   
                   
               
            
           
         
       
     
     Molecular sieves suitable for use in the method disclosed herein have a pore opening of at least about 5 Angstroms and a Sanderson electronegativity of less than or equal to about 2.75 (based on Sanderson (1983)). 
     In some embodiments, the molecular sieve has a pore opening of about 5 Angstroms to about 9 Angstroms and a Sanderson electronegativity of less than or equal to about 2.75 (based on Sanderson (1983)). 
     In one embodiment, the molecular sieve is activated carbon. 
     In some embodiments, the molecular sieve is a zeolite. 
     In some embodiments, the zeolite is selected from one or more members of the group consisting of zeolite X, zeolite Y, zeolite LSX, and the divalent cation forms of zeolite A, such as Ca 2+ , Sr 2+ , Ba 2+ , Cd 2+ , and Zn 2+ . 
     In other embodiments, the zeolite is selected from one or more members of the group consisting of zeolite 5A and zeolite 13X. 
     In some embodiments, the zeolite is zeolite LSX. 
     Mixtures of any of the aforementioned zeolites may also be used in the method disclosed herein. 
     Zeolites are typically pre-treated before use by heating, optionally in a dry gas stream. The pre-treatment temperature is typically in the range of from about 100° C. to about 500° C. The dry gas stream is typically dry air or dry nitrogen. 
     Method for Capturing Trifluoromethane 
     The method disclosed herein is useful for capturing trifluoromethane from a gaseous mixture in a vent stream from a chlorodifluoromethane manufacturing process. Chlorodifluoromethane is prepared by reacting chloroform with HF according to the following reaction: 
       HCCl 3 +2HF→HCF 2 Cl+2HCl
 
     Trifluoromethane is a by-product of this reaction, typically present at a level of less than 5 wt %. The chlorodifluoromethane is separated from the trifluoromethane by a distillation process, resulting in a mixture containing primarily trifluoromethane and HCl. The HCl is removed from the mixture by a scrubbing process which utilizes water. Residual trifluoromethane dissolved in the scrubbing solution is removed using inert gas such as air, argon, or nitrogen, resulting in a gaseous mixture consisting essentially of trifluoromethane and nitrogen, oxygen, argon, and/or carbon dioxide. The gaseous mixture may also contain small amounts of chlorodifluoromethane and/or HCl, typically less than 5 wt %. This gaseous mixture is typically vented into the atmosphere as a vent stream. However, it is desirable to capture the trifluoromethane in the vent stream to prevent its release into the atmosphere because of the very high global warming potential of trifluoromethane (i.e., GWP=11,700 relative to CO 2  GWP=1). 
     In the method disclosed herein, the gaseous mixture in the vent stream from a chlorodifluoromethane manufacturing process is contacted with at least one molecular sieve, described above, at a pressure of about 0.1 MPa to about 4.8 MPa, and a temperature of about 273 K to about 323 K for a period of time sufficient for the molecular sieve to remove at least a portion of the trifluoromethane present in the gaseous mixture. Ideally, substantially all of the trifluoromethane is removed by the molecular sieve. Suitable conditions for the capture of the trifluoromethane from the gaseous mixture may be determined by one skilled in the art using routine experimentation. In some embodiments, the gaseous mixture is contacted with the molecular sieve at a pressure of about 0.5 MPa to about 4.5 MPa, more particularly about 1.0 MPa to about 4.5 MPa, and more particularly about 2.0 MPa to about 4.5 MPa. 
     In some embodiments, the gaseous mixture is contacted with the molecular sieve at a temperature of about 283 K to about 323 K, more particularly about 298 K to about 323 K. 
     In the method disclosed herein, the molecular sieve may be contained in a stationary packed bed through which the gaseous mixture from the vent stream is passed. Alternatively, the molecular sieve may be used in the form of a countercurrent moving bed or in a fluidized bed for contacting the gaseous mixture from the vent stream. In these embodiments, the trifluoromethane is captured by the molecular sieve in the bed and the remaining components of the gaseous mixture pass through. 
     After capture of the trifluoromethane, the molecular sieve may be regenerated by heating with steam to release the sorbed trifluoromethane and reused in the method. The released trifluoromethane may be incinerated or liquefied by pressurizing for storage. Alternatively, the molecular sieve with the sorbed trifluoromethane may be incinerated for disposal. 
     EXAMPLES 
     The present invention is further defined in the following Examples. It should be understood that these Examples, while indicating preferred embodiments of the invention, are given by way of illustration only. From the above discussion and these Examples, one skilled in the art can ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various uses and conditions. 
     The meaning of abbreviations used is as follows: “min” means minute(s), “h” means hour(s), “mL” means milliliter(s), “μL” means microliter(s), “g” means gram(s), “mg” means milligram(s), “μg” means microgram(s), “Pa” means pascal(s), “kPa” means kilopascal(s), and “MPa” means megapascal(s). 
     Materials 
     Trifluoromethane (R-23, CHF 3 , purity &gt;99.995%, molecular weight 70.014 g mol −1 , CAS no. 75-46-7) was purchased from GTS-Welco (Allentown, Pa.). Zeolite 5A (theoretical “pseudo” unit cell composition Ca 4 Na 4 [(AlO 2 ) 12 (SiO 2 ) 12 ].xH 2 O, molecular weight 1681.05, CAS no. 69912-79-4) and Zeolite 13X ((theoretical unit cell composition Na 86 [(AlO 2 ) 86 (SiO 2 ) 106 ].xH 2 O, molecular weight 13418.38 g mol −1 , CAS no. 63231-69-6) were purchased from Aldrich (Milwaukee, Wis.). Zeolite LSX ((theoretical unit cell composition Na 73 K 22 (AlO 2 ) 95 (SiO 2 ) 97 .xH 2 O, molecular weight 13969.72 g mol −1 , CAS no. 68989-22-0) was obtained from Zeochem, L.L.C. (Louisville, Ky.). 
     The zeolites were activated by heating a 2 gram sample under vacuum at 648 K for 12 h. The heating rate to reach this temperature was 30 K min −1 . 
     Example 1 
     Sorption of Trifluoromethane by Zeolite 5A 
     This Example illustrates the sorption of trifluoromethane by Zeolite 5A at temperatures of 298 K and 323 K. The sorption was measured using a gravimetric microbalance. 
     The sorption measurements were made using a gravimetric microbalance (IGA-003 Multicomponent Analyzer, Hiden Isochema Ltd., Warrington WA5 7TN UK). The IGA design integrates precise computer-control and measurement of weight change, pressure and temperature to enable fully automatic and reproducible determination of gas sorption isotherms and isobars. The microbalance consists of an electrobalance with sample and counterweight components inside a stainless steel pressure-vessel. The balance has a weigh range of 0-100 mg with a resolution of 0.1 μg. 
     Approximately 50 mg of the zeolite was loaded into a quartz glass container inside the microbalance. The reactor was sealed and evacuated. The zeolites were further dried by heating for 24 h at 323 K until no noticeable mass change was detected. 
     An enhanced pressure stainless steel (SS316LN) reactor capable of operation to 2.0 MPa and 773.15 K was installed. The advantages of using a microbalance include the minimal sample size (&lt;100 mg) required, the ability to automate the measurement process to take several PTx data, and the flexibility to measure both sorption and desorption isotherms. When done properly, the gravimetric analysis provides a direct an accurate method for assessing both gas solubility and diffusivity. Two critical factors that must be considered include properly correcting for the buoyancy effects of the system and allowing sufficient time to reach equilibrium (i.e., no mixing is possible). 
     The IGA-003 can operate in both dynamic and static modes. All sorption measurements were performed in static mode. Static mode operation introduces gas into the top of the balance away from the sample, and both the admittance and exhaust valves control the set-point pressure. The sample temperature was measured with a resistance temperature device (RTD) with an accuracy of ±0.1 K. The RTD was calibrated using a standard platinum resistance thermometer (SPRT model 5699, Hart Scientific, American Fork, Utah, range 73 to 933 K) and readout (Blackstack model 1560 with SPRT module 2560). The Blackstack instrument and SPRT are a certified secondary temperature standard with a NIST traceable accuracy to ±0.005 K. Two isotherms of about 298 and 323 K were measured beginning with 298 K. Two pressure sensors were used for the measurements. Pressures from 10 −4  to 10 −2  MPa were measured using a capacitance manometer (MKS, model Baratron 626A) with an accuracy of ±0.015 kPa. Pressures from 10 −2  to 2.0 MPa were measured using a piezo-resistive strain gauge (Druck, model PDCR4010) with an accuracy of ±0.8 kPa. The Druck low-pressure transducer was calibrated against a Paroscientific Model 765-15A (Redmond, Wash.) pressure transducer (range 0 to 0.102 MPa, part no. 1100-001, serial no. 104647). The Druck high-pressure transducer was calibrated against a Paroscientific Model 765-1K (Redmond, Wash.) pressure transducer (range 0 to 6.805 MPa, part no. 1100-017, serial no. 101314). These instruments are also a NIST certified secondary pressure standard with a traceable accuracy of 0.008% of full scale. The upper pressure limit of the microbalance reactor was 2.0 MPa, and several isobars up to 2.0 MPa (0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.25, 0.50, 0.75, 1.0, 1.25, 1.5, 1.75 and 2.0 MPa) were measured. To ensure sufficient time to reach equilibrium, a minimum time of 10 h and a maximum time of 20 h were set for isotherms measured at 298 and 323 K. The total uncertainties in the solubility data due to both random and systematic errors have been estimated to be less than 0.006 mole fraction at given T and P. The equivalent uncertainty in molality for Zeolite 5A was 0.0036 mol·kg −1  at given T and P. 
     The corrected sorption (PTx) data for trifluoromethane by Zeolite 5A is shown in Table 2. In the table, x 1  is the mole fraction of trifluoromethane. Desorption isotherms were also measured at 298 and 323 K and the (PTx) data are included in Table 2. The trifluoromethane mass uptake versus time for sorption and desorption experiments between 0 and 2.0 MPa at 298 and 323 K indicate the sorption is reversible for Zeolite 5A. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Sorption Data for Trifluoromethane by Zeolite 5A 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                   
                 Molality/mol 
               
               
                 T/K 
                 P/MPa 
                 wt % 
                 100 x 1   
                 kg −1   
               
               
                   
               
            
           
           
               
            
               
                 Sorption 
               
            
           
           
               
               
               
               
               
            
               
                 298.1 
                 0.0024 
                 6.4 
                 62.1 
                 0.98 
               
               
                 298.1 
                 0.0053 
                 9.6 
                 71.8 
                 1.52 
               
               
                 298.1 
                 0.0069 
                 10.3 
                 73.3 
                 1.63 
               
               
                 298.1 
                 0.0109 
                 12.5 
                 77.4 
                 2.03 
               
               
                 298.1 
                 0.0202 
                 14.4 
                 80.1 
                 2.40 
               
               
                 298.1 
                 0.0301 
                 15.6 
                 81.6 
                 2.64 
               
               
                 298.1 
                 0.0400 
                 16.1 
                 82.2 
                 2.75 
               
               
                 298.1 
                 0.0503 
                 16.9 
                 83.0 
                 2.91 
               
               
                 298.1 
                 0.0750 
                 17.4 
                 83.5 
                 3.01 
               
               
                 298.1 
                 0.1002 
                 18.1 
                 84.2 
                 3.17 
               
               
                 298.1 
                 0.2501 
                 19.8 
                 85.5 
                 3.52 
               
               
                 298.1 
                 0.4999 
                 21.2 
                 86.6 
                 3.84 
               
               
                 298.1 
                 0.7499 
                 22.3 
                 87.3 
                 4.11 
               
               
                 298.1 
                 1.0026 
                 23.3 
                 88.0 
                 4.35 
               
               
                 298.1 
                 1.2513 
                 24.3 
                 88.5 
                 4.59 
               
               
                 298.1 
                 1.5007 
                 25.3 
                 89.0 
                 4.84 
               
               
                 298.1 
                 1.7507 
                 26.3 
                 89.5 
                 5.09 
               
               
                 298.1 
                 2.0012 
                 27.3 
                 90.0 
                 5.35 
               
            
           
           
               
            
               
                 Sorption 
               
            
           
           
               
               
               
               
               
            
               
                 323.1 
                 0.0026 
                 5.8 
                 59.8 
                 0.88 
               
               
                 323.1 
                 0.0057 
                 9.6 
                 71.9 
                 1.52 
               
               
                 323.1 
                 0.0090 
                 10.9 
                 74.7 
                 1.76 
               
               
                 323.1 
                 0.0113 
                 12.1 
                 76.7 
                 1.96 
               
               
                 323.1 
                 0.0209 
                 13.6 
                 79.1 
                 2.25 
               
               
                 323.1 
                 0.0307 
                 14.6 
                 80.4 
                 2.44 
               
               
                 323.1 
                 0.0402 
                 15.1 
                 81.1 
                 2.55 
               
               
                 323.1 
                 0.0503 
                 15.6 
                 81.6 
                 2.64 
               
               
                 323.1 
                 0.0752 
                 16.3 
                 82.4 
                 2.78 
               
               
                 323.1 
                 0.1000 
                 16.9 
                 83.0 
                 2.90 
               
               
                 323.1 
                 0.2498 
                 18.7 
                 84.7 
                 3.29 
               
               
                 323.1 
                 0.4997 
                 20.2 
                 85.9 
                 3.62 
               
               
                 323.2 
                 0.7495 
                 21.4 
                 86.7 
                 3.88 
               
               
                 323.1 
                 0.9994 
                 22.3 
                 87.3 
                 4.11 
               
               
                 323.1 
                 1.2520 
                 23.3 
                 87.9 
                 4.33 
               
               
                 323.1 
                 1.4992 
                 24.1 
                 88.4 
                 4.54 
               
               
                 323.1 
                 1.7524 
                 25.0 
                 88.9 
                 4.75 
               
               
                 323.2 
                 2.0030 
                 25.8 
                 89.3 
                 4.96 
               
            
           
           
               
            
               
                 Desorption 
               
            
           
           
               
               
               
               
               
            
               
                 323.1 
                 0.9991 
                 22.3 
                 87.4 
                 4.11 
               
               
                 323.1 
                 0.0998 
                 17.1 
                 83.2 
                 2.94 
               
               
                   
               
            
           
         
       
     
     Example 2 
     Sorption of Trifluoromethane by Zeolite 13X 
     This Example illustrates the sorption of trifluoromethane on Zeolite 13X at temperatures of 298 K and 323 K. The sorption was measured using a gravimetric microbalance using the method described in Example 1. 
     The equivalent uncertainties in molality for Zeolite 13X was 0.0004 mol·kg −1  at given T and P. The corrected sorption (PTx) data for trifluoromethane by Zeolite 13X is shown in Table 3. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Sorption Data for Trifluoromethane by Zeolite 13X 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                   
                 Molality/mol 
               
               
                 T/K 
                 P/MPa 
                 wt % 
                 100 x 1   
                 kg −1   
               
               
                   
               
            
           
           
               
            
               
                 Sorption 
               
            
           
           
               
               
               
               
               
            
               
                 298.1 
                 0.0010 
                 12.3 
                 96.4 
                 2.01 
               
               
                 298.1 
                 0.0020 
                 14.3 
                 97.0 
                 2.39 
               
               
                 298.1 
                 0.0030 
                 15.4 
                 97.2 
                 2.60 
               
               
                 298.1 
                 0.0040 
                 16.0 
                 97.4 
                 2.73 
               
               
                 298.1 
                 0.0050 
                 16.5 
                 97.4 
                 2.83 
               
               
                 298.1 
                 0.0060 
                 16.9 
                 97.5 
                 2.91 
               
               
                 298.1 
                 0.0070 
                 17.2 
                 97.6 
                 2.97 
               
               
                 298.3 
                 0.0077 
                 17.4 
                 97.6 
                 3.00 
               
               
                 298.1 
                 0.0080 
                 17.5 
                 97.6 
                 3.03 
               
               
                 298.1 
                 0.0090 
                 17.7 
                 97.6 
                 3.07 
               
               
                 298.1 
                 0.0111 
                 18.0 
                 97.7 
                 3.15 
               
               
                 298.1 
                 0.0301 
                 19.3 
                 97.9 
                 3.41 
               
               
                 298.1 
                 0.0400 
                 19.7 
                 97.9 
                 3.50 
               
               
                 298.1 
                 0.0501 
                 20.0 
                 98.0 
                 3.57 
               
               
                 298.1 
                 0.1004 
                 20.9 
                 98.1 
                 3.78 
               
               
                 298.1 
                 0.2517 
                 22.3 
                 98.2 
                 4.10 
               
               
                 298.1 
                 0.5010 
                 23.6 
                 98.3 
                 4.41 
               
               
                 298.1 
                 0.7505 
                 24.7 
                 98.4 
                 4.68 
               
               
                 298.1 
                 1.0005 
                 25.6 
                 98.5 
                 4.92 
               
               
                 298.1 
                 1.2508 
                 26.6 
                 98.6 
                 5.16 
               
               
                 298.1 
                 1.5015 
                 27.5 
                 98.6 
                 5.42 
               
               
                 298.1 
                 1.7507 
                 28.5 
                 98.7 
                 5.68 
               
               
                 298.1 
                 2.0009 
                 29.4 
                 98.8 
                 5.96 
               
            
           
           
               
            
               
                 Sorption 
               
            
           
           
               
               
               
               
               
            
               
                 323.1 
                 0.0005 
                 5.8 
                 92.2 
                 0.88 
               
               
                 323.1 
                 0.0010 
                 7.9 
                 94.2 
                 1.22 
               
               
                 323.1 
                 0.0020 
                 10.2 
                 95.6 
                 1.62 
               
               
                 323.1 
                 0.0030 
                 11.5 
                 96.1 
                 1.85 
               
               
                 323.1 
                 0.0040 
                 12.5 
                 96.5 
                 2.04 
               
               
                 323.1 
                 0.0050 
                 13.3 
                 96.7 
                 2.18 
               
               
                 323.1 
                 0.0062 
                 13.9 
                 96.9 
                 2.30 
               
               
                 323.1 
                 0.0075 
                 14.4 
                 97.0 
                 2.41 
               
               
                 323.2 
                 0.0200 
                 16.6 
                 97.5 
                 2.85 
               
               
                 323.1 
                 0.0301 
                 17.5 
                 97.6 
                 3.02 
               
               
                 323.1 
                 0.0400 
                 18.0 
                 97.7 
                 3.13 
               
               
                 323.1 
                 0.0503 
                 18.4 
                 97.7 
                 3.22 
               
               
                 323.1 
                 0.1001 
                 18.9 
                 97.8 
                 3.32 
               
               
                 323.2 
                 0.2501 
                 20.5 
                 98.0 
                 3.69 
               
               
                 323.1 
                 0.5010 
                 22.0 
                 98.2 
                 4.03 
               
               
                 323.1 
                 0.7518 
                 23.1 
                 98.3 
                 4.29 
               
               
                 323.1 
                 1.0014 
                 24.1 
                 98.4 
                 4.53 
               
               
                 323.1 
                 1.2508 
                 25.0 
                 98.5 
                 4.75 
               
               
                 323.1 
                 1.5009 
                 25.9 
                 98.5 
                 4.99 
               
               
                 323.1 
                 1.7505 
                 26.8 
                 98.6 
                 5.22 
               
               
                 323.2 
                 2.0003 
                 27.6 
                 98.7 
                 5.44 
               
               
                   
               
            
           
         
       
     
     Example 3 
     Sorption of Trifluoromethane by Zeolite LSX 
     This Example illustrates the sorption of trifluoromethane by Zeolite LSX at temperatures of 298 K and 323 K. The sorption was measured using a gravimetric microbalance using the method described in Example 1. 
     The equivalent uncertainties in molality for Zeolite LSX was 0.0004 mol·kg −1  at given T and P. The corrected sorption (PTx) data for trifluoromethane by Zeolite LSX is shown in Table 4. Desorption isotherms were also measured at 298 and 323 K and the (PTx) data are included in Table 4. The trifluoromethane mass uptake versus time for sorption and desorption experiments between 0 and 2.0 MPa at 298 and 323 K indicate the sorption is reversible for Zeolite LSX. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Sorption Data for Trifluoromethane on Zeolite LSX 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                   
                 Molality/mol 
               
               
                 T/K 
                 P/MPa 
                 wt % 
                 100 x 1   
                 kg −1   
               
               
                   
               
            
           
           
               
            
               
                 Sorption 
               
            
           
           
               
               
               
               
               
            
               
                 298.1 
                 0.0010 
                 17.2 
                 97.6 
                 2.96 
               
               
                 298.1 
                 0.0020 
                 18.0 
                 97.7 
                 3.13 
               
               
                 298.1 
                 0.0030 
                 18.4 
                 97.8 
                 3.22 
               
               
                 298.1 
                 0.0040 
                 18.7 
                 97.8 
                 3.28 
               
               
                 298.1 
                 0.0050 
                 18.9 
                 97.8 
                 3.33 
               
               
                 298.1 
                 0.0051 
                 18.9 
                 97.8 
                 3.34 
               
               
                 298.1 
                 0.0060 
                 19.1 
                 97.9 
                 3.37 
               
               
                 298.1 
                 0.0070 
                 19.2 
                 97.9 
                 3.40 
               
               
                 298.1 
                 0.0080 
                 19.4 
                 97.9 
                 3.43 
               
               
                 297.8 
                 0.0090 
                 19.5 
                 97.9 
                 3.47 
               
               
                 298.1 
                 0.0106 
                 19.6 
                 97.9 
                 3.48 
               
               
                 298.1 
                 0.0103 
                 19.7 
                 97.9 
                 3.50 
               
               
                 298.1 
                 0.0205 
                 20.2 
                 98.0 
                 3.62 
               
               
                 298.1 
                 0.0248 
                 20.5 
                 98.0 
                 3.68 
               
               
                 298.1 
                 0.0303 
                 20.6 
                 98.1 
                 3.71 
               
               
                 298.1 
                 0.0402 
                 20.9 
                 98.1 
                 3.78 
               
               
                 298.1 
                 0.0501 
                 21.2 
                 98.1 
                 3.84 
               
               
                 298.1 
                 0.0498 
                 21.3 
                 98.1 
                 3.86 
               
               
                 298.1 
                 0.0999 
                 22.0 
                 98.2 
                 4.03 
               
               
                 298.1 
                 0.0998 
                 22.1 
                 98.2 
                 4.05 
               
               
                 298.1 
                 0.2500 
                 23.3 
                 98.3 
                 4.34 
               
               
                 298.1 
                 0.4999 
                 24.6 
                 98.4 
                 4.65 
               
               
                 298.1 
                 0.7494 
                 25.6 
                 98.5 
                 4.91 
               
               
                 298.1 
                 1.0001 
                 26.5 
                 98.6 
                 5.16 
               
               
                 298.1 
                 1.2498 
                 27.4 
                 98.7 
                 5.40 
               
               
                 298.1 
                 1.5002 
                 28.3 
                 98.7 
                 5.64 
               
               
                 298.1 
                 1.7496 
                 29.2 
                 98.8 
                 5.90 
               
               
                 298.1 
                 1.9996 
                 30.2 
                 98.8 
                 6.17 
               
            
           
           
               
            
               
                 Desorption 
               
            
           
           
               
               
               
               
               
            
               
                 298.1 
                 0.0998 
                 22.1 
                 98.2 
                 4.05 
               
               
                 298.1 
                 0.0498 
                 21.3 
                 98.1 
                 3.86 
               
            
           
           
               
            
               
                 Sorption 
               
            
           
           
               
               
               
               
               
            
               
                 323.1 
                 0.0010 
                 15.4 
                 97.3 
                 2.61 
               
               
                 323.1 
                 0.0020 
                 16.6 
                 97.5 
                 2.84 
               
               
                 323.1 
                 0.0030 
                 17.2 
                 97.6 
                 2.97 
               
               
                 323.2 
                 0.0040 
                 17.6 
                 97.7 
                 3.05 
               
               
                 323.2 
                 0.0050 
                 17.9 
                 97.7 
                 3.11 
               
               
                 323.1 
                 0.0056 
                 18.1 
                 97.7 
                 3.15 
               
               
                 323.1 
                 0.0060 
                 18.1 
                 97.7 
                 3.16 
               
               
                 323.2 
                 0.0070 
                 18.3 
                 97.8 
                 3.20 
               
               
                 323.1 
                 0.0080 
                 18.5 
                 97.8 
                 3.24 
               
               
                 323.1 
                 0.0090 
                 18.6 
                 97.8 
                 3.27 
               
               
                 323.1 
                 0.0102 
                 18.7 
                 97.8 
                 3.29 
               
               
                 323.1 
                 0.0099 
                 18.8 
                 97.8 
                 3.30 
               
               
                 323.1 
                 0.0106 
                 18.8 
                 97.8 
                 3.30 
               
               
                 323.1 
                 0.0204 
                 19.5 
                 97.9 
                 3.45 
               
               
                 323.1 
                 0.0248 
                 19.7 
                 97.9 
                 3.50 
               
               
                 323.1 
                 0.0304 
                 19.9 
                 98.0 
                 3.55 
               
               
                 323.1 
                 0.0402 
                 20.2 
                 98.0 
                 3.62 
               
               
                 323.1 
                 0.0501 
                 20.4 
                 98.0 
                 3.67 
               
               
                 323.1 
                 0.0498 
                 20.4 
                 98.0 
                 3.67 
               
               
                 323.1 
                 0.0998 
                 21.2 
                 98.1 
                 3.85 
               
               
                 323.1 
                 0.1000 
                 21.3 
                 98.1 
                 3.85 
               
               
                 323.1 
                 0.2499 
                 22.6 
                 98.3 
                 4.16 
               
               
                 323.1 
                 0.5000 
                 23.9 
                 98.4 
                 4.48 
               
               
                 323.1 
                 0.7499 
                 24.9 
                 98.5 
                 4.73 
               
               
                 323.2 
                 0.9996 
                 25.8 
                 98.5 
                 4.96 
               
               
                 323.1 
                 1.2515 
                 26.6 
                 98.6 
                 5.18 
               
               
                 323.2 
                 1.5003 
                 27.4 
                 98.7 
                 5.39 
               
               
                 323.2 
                 1.7526 
                 28.2 
                 98.7 
                 5.61 
               
               
                 323.1 
                 2.0026 
                 29.0 
                 98.8 
                 5.84 
               
            
           
           
               
            
               
                 Desorption 
               
            
           
           
               
               
               
               
               
            
               
                 323.1 
                 0.0998 
                 21.2 
                 98.1 
                 3.85 
               
               
                 323.1 
                 0.0498 
                 20.5 
                 98.0 
                 3.67 
               
               
                 323.1 
                 0.0049 
                 17.9 
                 97.7 
                 3.12 
               
               
                 323.2 
                 0.0010 
                 15.5 
                 97.3 
                 2.61 
               
               
                   
               
            
           
         
       
     
     Example 4 
     Sorption of Trifluoromethane in Activated Carbon 
     This Example illustrates the sorption of trifluoromethane by activated carbon at temperatures of 298 K and 323 K. The sorption was measured using a gravimetric microbalance using the method described in Example 1. 
     The activated carbon was synthesized from coal tar pitch. The pitch was stabilized by heating to 573 K. The carbon was activated by heating to about 1153 to 1173 K in the presence of potassium hydroxide (KOH) vapors. In order to dry the carbon and remove any residual KOH vapor or adsorbed gases from the pores, the activated carbon was heated in a vertical tube furnace at 623 K for 24 hours under vacuum. 
     The surface area and pore volume were measured by nitrogen adsorption/desorption measurements, performed at 77 K on a Micromeritics ASAP model 2420 porosimeter. Samples were degased at 423 K overnight prior to data collection. Surface area measurements utilized a five-point adsorption isotherm collected over 0.05 to 0.20 P/P 0  (P 0 =nitrogen saturation pressure) and analyzed via the BET method. (Brunauer et al.,  J. Amer. Chem. Soc.  60, 309-319, 1938) Total pore volume was determined by a single point measurement at P/P 0 =0.995. The BET specific surface area was 3206 m 2  g −1  with a Type I isotherm. The BET model has inaccuracies for micropore systems which can lead to condensation even at low relative pressure and, correspondingly, to an overestimation of the surface area (Kaneko, et al.,  Carbon  30, 1075-1088 1992). The BET specific surface area is a reproducible measurement, characteristic of the material, but possibly an overestimation of the total surface area. The total pore volume is 1.68 cm 3  g −1  with an average pore diameter of 2.0 nm. 
     The equivalent uncertainty in molality for activated carbon was 0.5 mol kg −1  at given T and P. The corrected solubility (PTx) data for R-23 in the activated carbon is shown in Table 5. Desorption isotherms were also measured at 298 and 323 K and the (PTx) data are included in Table 5. The R-23 mass uptake between 0 and 2.0 MPa at 298 and 323 K indicate the sorption is reversible. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Sorption Data for Trifluoromethane on Activated Carbon 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                   
                 Molality/mol 
               
               
                 T/K 
                 P/MPa 
                 wt % 
                 100 x 1   
                 kg −1   
               
               
                   
               
            
           
           
               
            
               
                 Sorption 
               
            
           
           
               
               
               
               
               
            
               
                 298.1 
                 0.0010 
                 0.76 
                 0.0013 
                 0.109 
               
               
                 298.1 
                 0.0020 
                 1.39 
                 0.0024 
                 0.199 
               
               
                 298.1 
                 0.0030 
                 1.96 
                 0.0034 
                 0.280 
               
               
                 298.1 
                 0.0040 
                 2.45 
                 0.0043 
                 0.350 
               
               
                 298.1 
                 0.0050 
                 2.93 
                 0.0051 
                 0.418 
               
               
                 298.1 
                 0.0060 
                 3.36 
                 0.0059 
                 0.480 
               
               
                 298.1 
                 0.0070 
                 3.76 
                 0.0067 
                 0.537 
               
               
                 298.1 
                 0.0080 
                 4.16 
                 0.0074 
                 0.594 
               
               
                 298.1 
                 0.0090 
                 4.55 
                 0.0081 
                 0.650 
               
               
                 298.1 
                 0.0102 
                 4.88 
                 0.0087 
                 0.697 
               
               
                 298.1 
                 0.0248 
                 9.22 
                 0.0171 
                 1.317 
               
               
                 298.1 
                 0.0498 
                 14.54 
                 0.0283 
                 2.077 
               
               
                 298.1 
                 0.0996 
                 21.90 
                 0.0459 
                 3.128 
               
               
                 298.1 
                 0.2438 
                 34.06 
                 0.0814 
                 4.865 
               
               
                 298.1 
                 0.4531 
                 42.87 
                 0.1140 
                 6.123 
               
               
                 298.1 
                 0.7492 
                 49.54 
                 0.1442 
                 7.076 
               
               
                 298.1 
                 0.9972 
                 53.10 
                 0.1626 
                 7.584 
               
               
                 298.1 
                 1.2489 
                 55.86 
                 0.1784 
                 7.978 
               
               
                 298.1 
                 1.4992 
                 58.06 
                 0.1919 
                 8.293 
               
               
                 298.1 
                 1.7494 
                 59.90 
                 0.2039 
                 8.555 
               
               
                 298.1 
                 1.9989 
                 61.45 
                 0.2147 
                 8.777 
               
            
           
           
               
            
               
                 Desorption 
               
            
           
           
               
               
               
               
               
            
               
                 298.1 
                 1.9963 
                 61.47 
                 0.2148 
                 8.780 
               
               
                 298.1 
                 1.7476 
                 59.91 
                 0.2040 
                 8.557 
               
               
                 298.2 
                 0.4431 
                 42.60 
                 0.1129 
                 6.084 
               
               
                 298.1 
                 0.2499 
                 34.49 
                 0.0828 
                 4.926 
               
               
                 298.1 
                 0.0998 
                 21.98 
                 0.0461 
                 3.139 
               
               
                 298.1 
                 0.0748 
                 18.64 
                 0.0378 
                 2.662 
               
               
                 298.1 
                 0.0499 
                 14.57 
                 0.0284 
                 2.081 
               
               
                 298.1 
                 0.0249 
                 9.30 
                 0.0173 
                 1.328 
               
               
                 298.1 
                 0.0099 
                 4.86 
                 0.0087 
                 0.694 
               
               
                 298.1 
                 0.0093 
                 4.72 
                 0.0084 
                 0.674 
               
               
                 298.1 
                 0.0080 
                 4.24 
                 0.0075 
                 0.606 
               
               
                 298.1 
                 0.0070 
                 3.85 
                 0.0068 
                 0.550 
               
               
                 298.1 
                 0.0060 
                 3.45 
                 0.0061 
                 0.493 
               
               
                 298.1 
                 0.0050 
                 3.01 
                 0.0053 
                 0.430 
               
               
                 298.1 
                 0.0040 
                 2.53 
                 0.0044 
                 0.361 
               
               
                 298.1 
                 0.0030 
                 2.03 
                 0.0035 
                 0.290 
               
               
                 298.1 
                 0.0020 
                 1.47 
                 0.0026 
                 0.210 
               
               
                 298.1 
                 0.0010 
                 0.84 
                 0.0015 
                 0.120 
               
            
           
           
               
            
               
                 Sorption 
               
            
           
           
               
               
               
               
               
            
               
                 323.2 
                 0.0010 
                 0.23 
                 0.0004 
                 0.033 
               
               
                 323.1 
                 0.0020 
                 0.55 
                 0.0010 
                 0.079 
               
               
                 323.1 
                 0.0030 
                 0.85 
                 0.0015 
                 0.121 
               
               
                 323.2 
                 0.0040 
                 1.14 
                 0.0020 
                 0.163 
               
               
                 323.2 
                 0.0050 
                 1.40 
                 0.0024 
                 0.200 
               
               
                 323.1 
                 0.0060 
                 1.65 
                 0.0029 
                 0.236 
               
               
                 323.2 
                 0.0070 
                 1.90 
                 0.0033 
                 0.271 
               
               
                 323.1 
                 0.0080 
                 2.15 
                 0.0038 
                 0.307 
               
               
                 323.1 
                 0.0090 
                 2.38 
                 0.0042 
                 0.340 
               
               
                 323.2 
                 0.0099 
                 2.53 
                 0.0044 
                 0.361 
               
               
                 323.2 
                 0.0248 
                 5.37 
                 0.0096 
                 0.767 
               
               
                 323.2 
                 0.0498 
                 9.05 
                 0.0168 
                 1.293 
               
               
                 323.1 
                 0.0746 
                 12.00 
                 0.0229 
                 1.714 
               
               
                 323.2 
                 0.0999 
                 14.63 
                 0.0286 
                 2.090 
               
               
                 323.1 
                 0.2488 
                 25.37 
                 0.0551 
                 3.624 
               
               
                 323.1 
                 0.4977 
                 35.54 
                 0.0864 
                 5.076 
               
               
                 323.2 
                 0.7493 
                 41.63 
                 0.1090 
                 5.946 
               
               
                 323.1 
                 0.9995 
                 45.77 
                 0.1265 
                 6.537 
               
               
                 323.3 
                 1.2428 
                 48.80 
                 0.1405 
                 6.970 
               
               
                 323.1 
                 1.4988 
                 51.36 
                 0.1534 
                 7.336 
               
               
                 323.1 
                 1.7492 
                 53.41 
                 0.1643 
                 7.628 
               
               
                 323.0 
                 1.9927 
                 55.13 
                 0.1741 
                 7.874 
               
            
           
           
               
            
               
                 Desorption 
               
            
           
           
               
               
               
               
               
            
               
                 323.2 
                 1.9912 
                 55.13 
                 0.1741 
                 7.874 
               
               
                 323.2 
                 1.7384 
                 53.37 
                 0.1641 
                 7.623 
               
               
                 323.2 
                 1.4931 
                 51.34 
                 0.1532 
                 7.333 
               
               
                 323.1 
                 1.2496 
                 48.88 
                 0.1409 
                 6.981 
               
               
                 323.2 
                 0.9997 
                 45.78 
                 0.1265 
                 6.539 
               
               
                 323.2 
                 0.7457 
                 41.57 
                 0.1088 
                 5.937 
               
               
                 323.1 
                 0.4995 
                 35.63 
                 0.0867 
                 5.089 
               
               
                 323.2 
                 0.2499 
                 25.50 
                 0.0555 
                 3.642 
               
               
                 323.2 
                 0.0999 
                 14.66 
                 0.0286 
                 2.094 
               
               
                 323.1 
                 0.0749 
                 12.12 
                 0.0231 
                 1.731 
               
               
                 323.1 
                 0.0498 
                 9.11 
                 0.0169 
                 1.301 
               
               
                 323.1 
                 0.0249 
                 5.45 
                 0.0098 
                 0.778 
               
               
                 323.1 
                 0.0099 
                 2.58 
                 0.0045 
                 0.368 
               
               
                 323.2 
                 0.0090 
                 2.43 
                 0.0042 
                 0.347 
               
               
                 323.2 
                 0.0080 
                 2.21 
                 0.0039 
                 0.316 
               
               
                 323.2 
                 0.0070 
                 1.98 
                 0.0035 
                 0.283 
               
               
                 323.1 
                 0.0060 
                 1.72 
                 0.0030 
                 0.246 
               
               
                 323.1 
                 0.0050 
                 1.48 
                 0.0026 
                 0.211 
               
               
                 323.2 
                 0.0040 
                 1.21 
                 0.0021 
                 0.173 
               
               
                 323.1 
                 0.0030 
                 0.93 
                 0.0016 
                 0.133 
               
               
                 323.1 
                 0.0020 
                 0.63 
                 0.0011 
                 0.090 
               
               
                 323.2 
                 0.0010 
                 0.31 
                 0.0005 
                 0.044