Impact of Heavy Hydrocarbons on Natural Gas Sweetening Using

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The impact of heavy hydrocarbons on natural gas sweetening using perfluorinated polymeric membranes. Colin A Scholes, Geoffrey W Stevens, and Sandra E. Kentish Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.6b01823 • Publication Date (Web): 23 Jun 2016 Downloaded from http://pubs.acs.org on July 4, 2016

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Industrial & Engineering Chemistry Research

The impact of heavy hydrocarbons on natural gas sweetening using perfluorinated polymeric membranes. Colin A. Scholes*, Geoffrey W. Stevens and Sandra E. Kentish Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC), Department of Chemical & Biomolecular Engineering, The University of Melbourne, VIC, 3010, Australia

Abstract Membranes that are resistant to heavy hydrocarbons are of particular interest in natural gas sweetening; the removal of acidic gases such as CO2, from methane. The perfluorinated polymers, Teflon AF1600 and Hyflon AD60, are studied here for this purpose because of their unusual solvent resistance properties. The sorption of hexane and toluene vapor in both perfluorinated polymers was observed to follow standard dual-mode sorption behaviour at activities less than 0.8, while multilayer absorption was observed for unity activity. However, the corresponding Henry’s law constants for both hydrocarbons were reduced compared to other classes of glassy polymeric membranes. This was attributed to the solvent resistant properties of the perfluorinated polymers. Under mixed gas conditions, it was observed that the CO2 permeability for both perfluorinated polymers was reduced compared to the single gas permeability, attributed to competitive sorption from CH4. However, CH4 permeability increased slightly for both membranes under mixed gas conditions. Adding hydrocarbon vapors to the mixed gas feed resulted in only small changes to the CO2 and CH4 permeability through both perfluorinated polymers, indicating both perfluorinated polymers have potential as hydrocarbon resistant membranes in natural gas sweetening.

Keywords: Teflon AF1600, Hyflon AD60, toluene, hexane, carbon dioxide * Corresponding author: [email protected]

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1. Introduction Polymeric membranes are used commercially in natural gas sweetening to separate CO2 from methane 1

. Natural gas generally contains heavy hydrocarbons, which are known to reduce membrane separation

performance because of competitive sorption and plasticization 2. In particular, plasticization by aromatic hydrocarbons can significantly reduce the membrane operating lifetime. As such, many membrane processes have pretreatment stages to remove the majority of condensable hydrocarbons and water. The development of membranes that are resistant to these hydrocarbons are of significant interest, as they have the potential to reduce pretreatment processing requirements and therefore make membrane technology more economically competitive. Amorphous perfluoropolymers such as Teflon AF and Hyflon AD are an interesting class of polymers, because the perfluorinated structure means these polymers are insoluble in many organic solvents

3, 4

.

As such, they have a low tendency towards swelling and plasticization in the presence of condensable organics 5.Our previous research has also highlighted water permselectivity behavior that differs from other classes of glassy polymers 6. Perfluoropolymers are known for their thermal and chemical stability because of the very stable carbon – fluorine bond 7. Teflon AF and Hyflon AD polymers are two such polymers that have both been studied for CO2 separation

7-10

, as well as organic vapor separation

11-15

.

Important for membrane separation, the bulky substituted dioxole moiety in these polymers reduces chain mobility and limits crystallinity, producing amorphous polymeric films with high fractional free volume

16

(Figure 1). However, the impact of hydrocarbon vapors on their performance in CO2

separation from CH4 has not been reported. Figure 1

In this investigation, the sorption behavior of hexane and toluene within Teflon AF1600 and Hyflon AD60 are reported, along with the separation performance of the perfluorinated polymers for CO2 separation from CH4 in the presence of these vapors. This is to mimic a natural gas sweetening process and provide insight into the suitability of both perfluorinated polymers for this application. As both Teflon AF1600 and Hyflon AD60 are glassy polymers, the total concentration of absorbed gas within a glassy polymer film (C) can be described by 17: C = C + C

(1) 2 ACS Paragon Plus Environment

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where CH is sorption of gas within the microvoids, and can be approximated by the standard Langmuir adsorption relationship dependent on the gas fugacity, : C =

(2)

C’H is the maximum adsorption capacity, while b is the ratio of rate coefficients of adsorption and desorption, or Langmuir affinity constant. CD is the concentration of gas dissociated within the polymer matrix and is proportional to the gas pressure through the Henry's Law constant (kD). Hence, the dualmode sorption of gases with glassy polymer films is written as: C = k +

(3)

For condensable vapors such as hexane or toluene, non-ideal behaviour can occur at higher activities. These effects can be most accurately modelled through the use of equations of state such as FloryHuggins 18 or PC-SAFT; or cluster models such as the engaged species induced clustering (ENSIC) model 19

. However, all these models require multiple parameters to be determined, which is not always

possible with limited sorption data. The permeability of gas A through the micro-void region can be impeded relative to movement through the Henry’s law region, and hence only a fraction (FA) of the micro-void concentration is mobile

20

.

Further, the presence of another gas or vapor will compete for sorption to the micro-voids region, which can be accounted for within the Langmuir adsorption term. The permeability of gas A in the presence of gas B can then be determined through Fick’s Law based on a competitive Langmuir model 21: P =

k +

− k +

(4)

where A is the fugacity of gas A, subscript 1 and 2 denote feed and permeate side respectively, DA the diffusivity of gas A, and FA is the fraction of the micro-void concentration of gas A that is mobile 20.

2. Experimental Amorphous Teflon AF1600 (copolymer of 65 mol% 2,2-bis-trifluoromethyl-4,5-difluoro-1,3-dioxole and 35 mol% tetrafluoroethylene) was purchased from DuPont (USA), Hyflon AD60 (copolymer of 60 mol% 2,2-bis(trifluoromethyl)-4-fluoro-5-trifluoromethoxy-1,3-dioxole with 40 mol% tetrafluoroethylene) was purchased from Solvay (Japan) and both were used as supplied. Dense films were prepared for both 3 ACS Paragon Plus Environment


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perfluorinated polymers from 10 wt% solutions in the fluorinated solvent PF5060 (3M, Australia) through controlled evaporation at room temperature in a fumehood covered by a Petri dish. The final film thickness of both polymeric membranes was on average 120 µm, used for both sorption and permeability measurements. All films were dried under vacuum at 40 oC for 3 days, after which no extra mass loss was observed. To minimize any age dependent behavior, all membranes were used within 5 days of drying. Physical properties are provided in Table 1. Table 1

Gas sorption measurements of CO2 and CH4 in the perfluorinated polymers have previously been reported by the authors 22. In the present work, hexane and toluene sorption isotherms up to a vapor activity of 0.8 were measured on a Gravimetric Sorption Analyzer (GHP-FS, with a Cahn D-200 balance, VTI Scientific Instruments, Florida) operating in flow mode. Helium, the carrier gas, flowed through the sample chamber at slightly greater than atmospheric pressure. The helium entered from two streams, one dry, the other passed through a hydrocarbon bubbler set at the temperature of the experiment, which saturated the helium with the hydrocarbon. Hydrocarbon activity within the sample chamber was achieved by varying the flowrate ratio of the dry and vapor rich gas streams, and by incrementally adjusting this ratio, different vapor activities were obtained. Mass uptake was observed over time and equilibrium was assumed to be reached when the mass of the polymer film and sorbed hydrocarbon vapour did not fluctuate outside of a 0.05% confidence range for a 30 min period. Sorption of liquid hexane and toluene (activity = 1) was determined at 35 oC by simple immersion studies where the membrane was removed at time intervals, wiped of surface liquid and weighed. The experiment continued until the weight had stabilised. The resulting mass uptake (M(t)) was then evaluated to determine the Fickian diffusion component (ϕ ) and the component due to relaxation processes (ϕ (t)) 23, 24. These relaxation processes are related to slow redistribution of available free volume with the film through segmental motion of the polymer chain, which enables additional vapor to be sorbed 26. #($) #%

= ϕ + ϕ (t)

(5)


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The Fickian diffusion coefficient (DA) was determined from Equation 6, based on the Fickian part of the uptake curve25, where M(t) is the membrane and hydrocarbon mass with time, M∞ is the membrane and hydrocarbon mass at very long time and I is the thickness of the membrane sample. #($) #%

=1−

' (* ) ( $ ∑/ exp − ( *01 (* ) .

(6)

Single gas permeabilities were undertaken on a variable pressure constant volume apparatus as previously reported 27. Single gas measurements were undertaken with a feed pressure of 1000 kPa at 35 oC. Mixed gas permeability measurements were undertaken on a constant pressure variable volume instrument, which has also been previously reported 28. For toluene and hexane vapour experiments, the hydrocarbon was added to the feed gas through a bubbler arrangement, with the feed gas at total 1000 kPa, comparable to our previous work 22. The hydrocarbon activity of the feed gas was varied by adjusting the bubbler temperature relative to that of the membrane cell (35 oC). Vapor concentration polarization was not an issue for these polymeric membrane systems, but to ensure good flow conditions the feed flowrate was at 100 mL/min and the helium sweep gas was at 24 mL/min, which are comparable to our previous hydrocarbon vapor study

29

. Pure CO2 (Industrial grade), pure CH4 (High

purity) and 10% CO2 in CH4 mixed gas where obtained from Coregas (Australia). Gas permeate flowrate was measured through a universal flowmeter (Agilent Technologies ADM3000) and composition through gas chromatography (Varian CP-3800, with Molecular sieve and PORAPAK Q columns). Steady state permeability conditions was confirmed by monitoring the change in CO2 and CH4 permeability over time exposed to the hydrocarbon vapour at each activity. Hexane and toluene in the permeate stream could not be detected, and as such hexane and toluene permeability through both membranes could not be determined. Error margins in all cases are determined from the standard deviation of three data sets.

3. Results and Discussion 3.1 Hydrocarbon solubility and Diffusivity in perfluorinated polymers Sorption of liquid hexane and toluene into Teflon AF1600 and Hyflon AD60 occurred over a period of over 24 hours. As has been observed with other workers, there were two clear sorption regimes evident when the sorbed mass of toluene was plotted on a square root time basis (Figures 2 and 3). The first 5 ACS Paragon Plus Environment


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regime corresponds to Fickian diffusion, described through Equation 6. The second regime is indicative of polymer relaxation, which occurred once toluene concentration exceeded around 90% of its final value. Polymer relaxation was less evident when hexane was the penetrant, with this evident only once the polymer concentration exceeded 95% of its final concentration for AF1600. There was insufficient accuracy in the data to determine if polymer relaxation occurred for hexane in Hyflon AD60, but if it did so, it was only once the polymer concentration exceeded 97% of the final value.

The diffusion

coefficients calculated from the Fickian part of the curve (Equation 6) are provided in Table 2.

Figure 2 Figure 3 Table 2

Alientev et al. 30, 31 have measured the diffusion coefficient of a number of penetrants in Teflon AF1600 and correlated these values with the penetrant critical volume. Extrapolation of their relationship to the critical volumes of hexane (366 cm3/mol) and toluene (314 cm3/mol32) would suggest diffusion coefficients consistent with those measured here. Toluene has a greater diffusion coefficient in both perfluorinated polymers because of its smaller critical volume compared to hexane which allows it to more easily penetrate into the membrane morphology. The greater diffusion coefficient observed for both hydrocarbons in Teflon AF1600 compared to Hyflon AD60 is associated with the greater FFV (Table 1), which results in less restricted mobility within the membrane morphology.

The sorption isotherms for hexane and toluene in Teflon AF1600 are provided in Figure 4, and for Hyflon in Figure 5. For both hydrocarbons in both perfluorinated polymers the isotherms are slightly concave to the vapor activity axis. A concave shape at low vapour activity is reflective of sorption of the hydrocarbon within the macrovoids of both perfluorinated polymers. The limited concavity in the present case suggests that this adsorption is small, with stronger sorption to the polymer matrix. Hexane has a stronger affinity for both perfluorinated polymers, which is attributed to its paraffin structure compared to the aromatic toluene. Above a vapor activity of 0.8 there is clear evidence of significant hexane sorption, as indicated by the substantial increase in sorbed amounts at activity of unity. This is consistent with the polymer relaxation process observed during the sorption experiments. For both membranes, the uptake of hexane increases dramatically at these high activities. This reflects hexane plasticizing and swelling both membranes at high vapor activity, and enabling significant sorption. In 6 ACS Paragon Plus Environment

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contrast, the perfluorinated polymers disrupt the potential for π-interactions between toluene molecules needed for toluene stacking and hence limiting strong sorption. Teflon AF1600 sorbs more hexane and toluene than Hyflon AD60 at the same vapor activity; which is attributed to the more open morphology of Teflon AF1600

14, 22, 30

. Comparison with literature is not possible, as to the best of the

authors’ knowledge no hydrocarbon isotherms for these perfluorinated polymers have previously been reported. However, Tokarev et al.

33

has reported hexane and toluene isotherms for Teflon AF2400,

which have similar behavior to that reported here; though the amount of vapor sorbed is greater because Teflon AF2400 has a higher fractional free volume than Teflon AF1600 and hence can accommodate more vapour within the Langmuir voids.

Figure 4 Figure 5

If more data were available, models such as the nonequilibrium lattice fluid model (NELF)

34

could be

used to investigate the entire isotherm. However, the data at lower activities, before the onset of multilayer sorption or of polymer relaxation processes could be readily fit to the more empirical dual mode sorption model. The fit to this equation is provided in Figures 2 and 3 and the resulting parameters are provided in Table 3 and 4 respectively. Also included in the tables are the parameters for the lighter gases CO2, N2 and CH4 previously reported, with analysis of the CO2 and CH4 sorption data discussed in the authors’ prior publication 22.

Table 3 Table 4

The Langmuir affinity constant (b) for both hexane and toluene in both perfluorinted polymers is greater than that of the lighter gases (CO2, CH4 and N2), consistent with their higher critical temperature. However, the values are a little lower than those reported for other classes of glassy polymers 2, where 7 ACS Paragon Plus Environment


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values of around 20 and 150 atm-1 are more common for hexane and toluene respectively. Such low affinity constants are consistent with the observed limited concavity of the sorption isotherm and can be attributed to the very low surface energy of perfluorinated polymers, which severely limits interactions between the hydrocarbons and with the micro-voids. The affinity constants of both hexane and toluene are lower for Hyflon AD60 compared to Teflon AF1600, which is attributed to the difference in chemical structure of the microvoid region between the two perfluorinated polymers (Figure 1). In particular, Hyflon AD60 has greater flexibility through the additional halogenated ether group, which results in more compact voidage region. The maximum Langmuir capacities of toluene are identical within error for the two perfluorinated polymers, implying that both membranes can accommodate similar amounts of toluene. Alternatively, hexane has a maximum Langmuir capacity in Teflon AF1600 that is almost half that of Hyflon AD60. This would be associated with the difference in free volume dimensions within the two perfluorinated polymers and importantly the ability of hexane to be packed into this voidage. The Henry’s law constants for both hydrocarbons are lower in Hyflon AD60 than Teflon AF1600, revealing that the chemical structure of Hyflon AD60 has weaker intermolecular interactions with both hydrocarbons than Teflon AF1600. This is attributed to the different structure and the extra halogenated ether group limiting interaction with either hydrocarbon. Interestingly, toluene has a greater Henry’s law constant than hexane for both perfluorinated polymers, implying that the aromatic structure has a greater intermolecular association with the fluorinated polymer chain than the paraffin structure. The Henry’s law constant can be expressed as a correlation with the Lennard-Jones potential well depth parameter (ε/κ) for the penetrating gas 35, 36: 23

k = k 1 e 45

(7)

where m is a universal constant, while kD0 is dependent upon the sorption medium. In Figure 6, Henry’s Law data for a range of polymers is plotted at 35oC as a function of ε/κ. It is clear that such a correlation fits the data, inclusive of the present results. Figure 6 suggests a value for m of 4.1 ± 0.3, which is lower than that predicted by Toi et al. of 6.67 ± 0.5 36. This difference may be because the Toi et al. study was limited to only four glassy polymers and a few gases, hence their data set was not as extensive as that utilized here.

Figure 6


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3.3 Gas permeability in perfluorinated polymers The single gas permeability of CO2 and CH4 through both Teflon AF1600 and Hyflon AD60 are provided in Table 5. The permeability of CH4 and CO2 in Teflon AF1600 are greater than the corresponding permeabilities in Hyflon AD60, because of greater FFV (Table 1). The Teflon AF1600 CO2 permeabilities are comparable with the literature

12, 30, 37

, but CH4 is half that reported by Alentiev et al. 38, which is

attributed to the film casting techniques, known to impact the performance of fluorinated polymers 31. For Hyflon AD60, the permeabilities are comparable to those reported by Jansen et al. Makhlouf et al.

37

12

, however

reported a lower CO2 permeability, believed to be associated with the lower

temperature of their measurement, 21 oC. Importantly, both membranes have selectivity for CO2 against CH4, and therefore have potential for CO2 separation from natural gas. The permselectivity of both Teflon AF1600 and Hyflon AD60 place these polymers in the middle range of glassy polymeric membranes for CO2 separation from methane 39.

Table 5

The mixed gas permeability in both Teflon AF100 and Hyflon AD60 under 90% CH4 – 10% CO2 feed conditions are provided in Table 6. These are undertaken at a total pressure of 1000 kPa, and hence the partial pressure driving force for both gases is lower than the single gas measurement. However, the authors’ have demonstrated in their previous paper that the permeability of CO2 and CH4 is relatively constant over this pressure range 6. For both membranes the CO2 permeability is slightly reduced relative to the single gas measurement, for Teflon AF1600 a reduction of 3% is observed and for Hyflon AD60 by 5%. A decrease in permeability between single and mixed gas measurements is common for glassy polymers, and can be attributed to competitive sorption from CH4 within the membranes reducing CO2 solubility. However, the small change observed here, within error of the single gas measurement, indicates that competitive sorption of CH4 upon CO2 is very minor, attributed to the low Langmuir affinity constants for both gases (Tables 2 and 3).

Table 6



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The CH4 permeability increases under mixed gas conditions. These increases are within measurement error, but may indicate slight plasticization of both membranes by CO2, leading to an increase in CH4 diffusivity through both membranes. Under mixed gas conditions, the ideal CO2/CH4 selectivity for both membranes decreases slightly compared to the single gas measurement, which is a result of the reduction in CO2 permeability observed and the slight increase in CH4 permeability. A decrease in ideal selectivity for mixed gas measurements is common for glassy polymeric membranes.

3.4 Perfluorinated polymers exposed to hexane vapor The permeability of both hexane and toluene through Teflon AF1600 and Hyflon AD60 could not be measured, as the permeate concentration was below the detection limit of the gas chromatograph. Based on reported hydrocarbon permeabilities in similar perfluorinated polymers

14, 16, 30

, it is expected

that both hexane and toluene permeabilities will be lower than CO2 for both perfluorinated polymers. For Teflon AF1600 there is a small decrease in CO2 permeability as the hexane activity increases (Figure 7). This change however is within error of the measurement in the absence of hexane at most activities and implies that hexane vapor sorption has little impact on Teflon AF1600 CO2 permeability. This is attributed to the low Langmuir affinity constant observed for hexane in Teflon AF1600, and hence competitive sorption effects are minor. For Hyflon AD60, there is a more measurable decrease in CO2 permeability upon exposure to hexane vapour (Figure 8). At the highest hexane vapor activity studied (0.67), CO2 permeability for Hyflon AD60 has decreased by 9%. This difference in behavior is due to the almost doubling in Langmuir affinity constant for hexane in Hyflon AD60 compared to Teflon AF1600 (Tables 3 and 4), and hence CO2 experiences a stronger competitive sorption effect. The effect of hexane competitive sorption on CO2 permeability in both Teflon AF1600 and Hyflon AD60 can be modelled through Equation 4 based on the data in Table 3 and 4, and the diffusivity and mobile fraction (FA) previously reported

22

. It is clear from Figures 7 and 8 that the resulting model does not follow the

experimental data, and over estimates the loss in CO2 permeability. This discrepancy is suggestive of hexane vapor plasticizing both polymers, increasing diffusion coefficients. However, there was only minor polymer relaxation in the presence of hexane in the sorption measurement (Figure 2), implying plasticization would be minor. Alternatively, the discrepancy with the model may be due to CO2


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associating with the sorbed hexane within both perfluorinated polymers, as CO2 has a strong solubility in hexane

40

. This would increase the CO2 solubility within the membrane and counter some of the

competitive sorption effects of hexane. This interaction between CO2 and hexane within the membrane is not accounted for in the dual mode sorption model. A small increase in CH4 permeability is observed with increasing hexane vapor activity for Teflon AF1600 (Figure 9). These measurements are all within error of the value without hexane. Conversely, for Hyflon AD60, there is no change in the CH4 permeability as a result of exposure to hexane vapour (Figure 20). These results imply that little or no competitive sorption occurs between CH4 and hexane within both perfluorinated polymers, again reflecting the low Langmuir constants for hexane. The CO2/CH4 selectivity decreases for Teflon AF1600 to 11 and for Hyflon AD60 to 9. This represents only a slight change over the mixed gas result in the absence of the heavy hydrocarbon (Table 6). Importantly, for both perfluorinated polymers, the change in CO2 and CH4 permeability upon exposure to hexane vapor is considerably less than that observed for other glassy membranes 41.

Figure 7 Figure 8 Figure 9 Figure 10

3.5 Perfluorinated polymers exposed to toluene vapor For Teflon AF1600 there is a decrease in CO2 permeability upon exposure to toluene, which is more significant than that observed for hexane (Figure 7). This is attributed to greater competitive sorption by toluene, reflecting the greater critical temperature and thus the greater Langmuir affinity constant of toluene (Table 3). For Hyflon AD60 the decrease in CO2 permeability upon exposure to toluene is comparable to that observed for hexane (Figure 8). This similarity between toluene and hexane in Hyflon AD60 is due to the similarity in sorption of both hydrocarbons in the membrane as demonstrated in Figure 5. Hence both hydrocarbons have similarity in competitive sorption effect on CO2. The application of Equation 4 suggests that either plasticization by toluene of both perfluorinated polymers 11 ACS Paragon Plus Environment


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occurs and/or CO2 associated with sorbed toluene counteracts some of the effects of competitive sorption; as the model under predicts the experimental data; however not as much as that observed for hexane. The CH4 permeability in Teflon AF1600 is relatively constant with toluene activity, with a slight increase in permeability at higher toluene activity (Figure 9). These results are within error of the vapor free mixed gas measurement. For Hyflon AD60, the CH4 permeability decreases with increasing toluene vapor activity and hence there is clear evidence of competitive sorption (Figure 10). This difference between Teflon AF1600 and Hyflon AD60 result can only be attributed to the degree of plasticization induced by toluene being different for both membranes. Hence, Teflon AF1600 plasticizes more than Hyflon AD60 and the effect of toluene competitive sorption on CH4 in Teflon AF1600 is lost. The changing permeabilities in the presence of toluene alter the ideal CO2/CH4 selectivity of the perfluorinated polymers. Teflon AF1600 selectivity decreases to 11 at high toluene activity, while that for Hyflon AD60 remains constant at 10. However, these changes in both permeability and selectivity in the presence of toluene are also minor when compared to other classes of glassy polymeric membranes.

Conclusion The sorption isotherms of hexane and toluene within Teflon AF1600 and Hyflon AD60 demonstrate that dual-sorption behavior occurs for both hydrocarbons and perfluorinated polymers, but that the Langmuir sorption is limited. There is evidence of significant sorption only at very high vapour activity, and the Henry’s law constants for both hydrocarbons in both perfluorinated polymers reveal poor solubility. The CO2 – CH4 separation performance of Teflon AF1600 and Hyflon AD60 in the presence of hexane and toluene demonstrate that both perfluorinated polymers experience only a minor reduction in permselectivity. This is probably related to the limited Langmuir sorption and possibly due to CO2 sorption within the hydrocarbon itself. These results imply that both perfluorinated polymers have potential as membranes that are resistant to such heavy hydrocarbons in a natural gas sweetening application.

Acknowledgements


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Funding for this CO2CRC project is provided by the Australian Government through its Cooperative Research Centre program as well as the Particulate Fluids Processing Centre and Peter Cook Centre for CCS at the University of Melbourne.

References (1) Baker, R. W., Vapor and Gas Separation by Membranes. In Advanced Membrane Technology and Applications, Li, N. N.; Fane, A. G.; Ho, W. S. W.; Matsuura, T., Eds. John Wiley & Sons: Hoboken, 2008; pp 559 - 580. (2) Scholes, C. A.; Kentish, S. E.; Stevens, G. W. Effects of minor components in carbon dioxide capture using polymeric gas separation membranes. Sep. Purif. Reviews 2009, 38, 1-44. (3) Drobny, J. G., Technology of Fluoropolymers. CRC Press: Boca Raton, 2001. (4) Resnick, P. R.; Buck, W. H., Teflon AF amorphous fluoropolymers. In Modern fluoropolymers: High performance polymers for diverse applications, Scheirs, J., Ed. John Wiley & Sons: Chichester, 1997. (5) Prabhakar, R.; Freeman, B. D. Application of hydrocarbon-fluorocarbon interactions in membrane-based gas separation. Desalination 2002, 144, 79-83. (6) Scholes, C. A.; Kanehashi, S.; Stevens, G. W.; Kentish, S. E. Water permeability and competitive permeation with CO2 and CH4 in perfluoropolymeric membranes. Sep. Purif. Technol. 2015, 147, 203209. (7) Merkel, T. C.; Pinnau, I.; Prabhakar, R.; Freeman, B. D., Gas and vapor transport properties of perfluoropolymers. In Materials Science of Membranes for Gas and Vapor Separation, Yampolskii, Y. P.; Freeman, B. D., Eds. John Wiley & Sons: Chinchester, 2006. (8) Merkel, T. C.; Bondar, V.; Nagai, K.; Freeman, B. D. Hydrocarbon and perfluorocarbon gas sorption in poly(dimethylsiloxane), poly(1-trimethylsilyl-1-propyne) and copolymers of tetrafluoroethylene and 2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole. Macromolecules 1999, 32, 370-374. (9) Bondar, V. I.; Freeman, B. D.; Yampolskii, Y. P. Sorption of gases and vapors in an amorphous glassy perfluorodioxole copolymer. Macromolecules 1999, 32, 6163-6171. (10) Prabhakar, R. S.; Freeman, B. D.; Roman, I. Gas and vapor sorption and permeation in poly(2,2,4trifluoro-5-trifluoromethoxy-1,3-dioxole-co-tetrafluoroethylene). Macromolecules 2004, 37, 7688-7697. (11) Smuleac, V.; Wu, J.; Nemser, S. M.; Majumdar, S.; Bhattacharyya, D. Novel perfluorinated polymer-based pervaporation membranes for the separation of solvent/water mixtures. J. Membr. Sci. 2010, 352, 41-49. (12) Jansen, J. C.; Friess, K.; Drioli, E. Organic vapour transport in glassy perfluoropolymer membranes: A simple semi-quantitative approach to analyze clustering phenomena by time lag measurements. J. Membr. Sci. 2011, 367, 141-151. (13) Tang, J.; Sirkar, K. K. Perfluoropolymer membrane behaves like a zeolite membrane in dehydration of aprotic solvents. J. Membr. Sci. 2012, 421-422, 211-216. (14) Polyakov, A. M.; Starannikova, L. E.; Yampolskii, Y. P. Amorphous Teflons AF as organophilic pervaporation materials. Transport of individual components. J. Membr. Sci. 2003, 216, 241-256. (15) Polyakov, A. M.; Starannikova, L. E.; Yampolskii, Y. P. Amorphous Teflons AF as organophilic pervaporation materials. Separation of mixtures of chloromethanes. J. Membr. Sci. 2004, 238, 21-32. (16) Pinnau, I.; Toy, L. G. Gas and vapor transport properties of amorphous perfluorinated copolymer membranes based on 2,2-bistrifluoromethyl-4,5-difluoro-1,3-dioxole/tetrafluoroethylene. J. Membr. Sci. 1996, 109, 125-133. 13 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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(17) Petropoulos, J. H., Mechanisms and theories for sorption and diffusion of gases in polymers. In Polymeric gas separation membranes, Paul, D. R.; Yampolskii, Y., Eds. CRC Press: Boca Raton, 1994; pp 17-81. (18) Flory, P., Principles of Polymer Chemistry. Cornell University Press: Ithaca, NY, 1953. (19) Favre, E.; Clement, R.; Nguyen, Q. T.; Schaetzel, P.; Neel, J. Sorption of organic solvents into dense silicone membranes. Part 2. Development of a new approach based on a clustering hypothesis for associated solvents. J. Chem. Soc. Faraday Transact. 1993, 89, 4347-4353. (20) Paul, D. R.; Koros, W. J. Effect of partially immobilizing sorption on permeability and the diffusion time lag. J. Polym. Sci. Part B: Polym. Phys. 1976, 14, 675-685. (21) Koros, W. J. Model for sorption of mixed gases in glassy polymers. J. Polym. Sci. Part B: Polym. Phys. 1980, 18, 981-992. (22) Scholes, C. A.; Kanehashi, S.; Stevens, G. W.; Kentish, S. E. Water permeability and competitive permeation with CO2 and CH4 in perfluoropolymeric membranes. Sep. Purifi. Technol. 2015, 147, 203209. (23) Wind, J. D.; Sirard, S. M.; Paul, D. R.; Green, P. F.; Johnston, K. P.; Koros, W. J. Relaxation dynamics of CO2 diffusion, sorption, and polymer swelling for plasticized polyimide membranes. Macromolecules 2003, 36, 6442-6448. (24) Wessling, M.; Huisman, I.; Boomgaard, T. v. d.; Smolders, C. A. Dilation kinetics of glassy aromatic polyimides induced by carbon dioxide sorption. J. Polym. Sci. Part B: Polym. Phys. 1995, 33, 1371-1384. (25) Crank, J.; Park, G. S., Methods of measurement. In The mathematics of diffusion, Crank, J., Ed. Oxford University Press: London, 1975; pp 1-39. (26) Berens, A. R.; Hopfenberg, H. B. Diffusion and relaxation in glassy polymer powders: 2. Separation of diffusion and relaxation parameters. Polymer 1978, 19, 489-496. (27) Duthie, X.; Kentish, S. E.; Powell, C.; Nagai, K.; Qiao, G. G.; Stevens, G. W. Operating temperature effects on the plasticization of polyimide gas separaiton membranes. J. Membr. Sci. 2007, 294, 40-49. (28) Anderson, C. J.; Tao, W.; Scholes, C. A.; Stevens, G. W.; Kentish, S. E. The performance of carbon membranes in the presence of condensable and non-condensable impurities. J. Membr. Sci. 2011, 378, 117-127. (29) Scholes, C. A.; Jin, J.; Stevens, G. W.; Kentish, S. E. Hydrocarbon solubility, permeability, and competitive sorption effects in polymer of intrinsic microporosity (PIM-1) membranes. J. Polym. Sci. Part B: Polym. Phys. 2016, 54, 397-404. (30) Alentiev, A. Y.; Yampolskii, Y. P.; Shantarovich, V. P.; Nemser, S. M.; Plate, N. A. High transport parameters and free volume of perfluorodioxole copolymers. J. Membr. Sci. 1997, 126, 123-132. (31) Jansen, J. C.; Macchione, M.; Drioli, E. On the unusual solvent retention and the effect on the gas transport in perfluorinated Hyflon AD membranes. J. Membr. Sci. 2007, 287, 132-137. (32) CRC Handbook of Chemistry and Physics. CRC Press: Boca Raton, FL, 2015. (33) Tokarev, A.; Friess, K.; Machkova, J.; Sipek, M.; Yampolskii, Y. Sorption and diffusion of organic vapors in amorphous Teflon AF2400. J. Polym. Sci. Part B: Polym. Phys. 2006, 44, 832-844. (34) Minelli, M.; Sarti, G. C. Permeability and solubility of carbon dioxide in different glassy polymer systems with and without plasticization. J. Membr. Sci. 2013, 444, 429-439. (35) Hildebrand, J. H.; Scott, R. L., Regular Solutions. Prentice-Hall: Englewood Cliffs, NJ, 1962. (36) Toi, K.; Morel, G.; Paul, D. R. Gas sorption and transport in poly(phenylene oxide) and comparison with other glassy polymers. J. Applied. Polym. Sci. 1982, 27, 2997-3005. (37) Makhloufi, C.; Roizard, D.; Favre, E. Reverse selective NH3/CO2 permeation in fluorinated polymers using membrane gas separation. J. Membr. Sci. 2013, 441, 63-72.


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(38) Alentiev, A. Y.; Shantarovich, V. P.; Merkel, T. C.; Bondar, V. I.; Freeman, B. D.; Yampolskii, Y. P. Gas and vapor sorption, permeation and diffusion in glassy amorphous Teflon AF1600. Macromolecules 2002, 35, 9513-9522. (39) Robeson, L. M. The upper bound revisited. J. Membr. Sci. 2008, 320, 390-400. (40) Lay, E. N.; Taghikhani, V.; Ghotbi, C. Measurement and correlation of CO2 solubility in the systems of CO2 + toluene, CO2 + benzene and CO2 +n-hexane at near-critical and supercritical conditions. J. Chem. Eng. Data 2006, 51, 2197-2200. (41) Hasan, R.; Scholes, C. A.; Stevens, G. W.; Kentish, S. E. Effect of hydrocarbons on the separation of carbon dioxide from methane through a polyimide gas separation membrane. Ind. Eng. Chem. Res. 2009, 48, 5415-5419. (42) Lin, H.; Freeman, B. D. Gas solubility, diffusivity and permeability in poly(ethylene oxide). J. Membr. Sci. 2004, 239, 105-117. (43) Lin, H.; Freeman, B. D. Gas and vapor solubility in cross-linked poly(ethylene glycol diacrylate). Macromolecules 2005, 38, 8394-8407. (44) Scholes, C. A.; Chen, G. Q.; Lu, H. T.; Kentish, S. E. Crosslined PEG and PEBAX membranes for concurrent permeation of water and carbon dioxide. Membranes 2015, 6, 10.3390/membranes6010001. (45) Scholes, C. A.; Jin, J.; Stevens, G. W.; Kentish, S. E. Gas and water competitive sorption in high free volume polymeric membranes. J. Polym. Sci. Part B: Polym. Phys. 2015, 10.1002/polb.23689. (46) Li, P.; Chung, T.-S.; Paul, D. R. Gas sorption and permeation in PIM-1. J. Membr. Sci. 2013, 432, 50-57. (47) Chen, G. Q.; Scholes, C. A.; Doherty, C. M.; Hill, A. J.; Qiao, G. G.; Kentish, S. E. Modeling of the sorption and transport properties of water vapor in polyimide membranes. J. Membr. Sci. 2012, 409410, 96-104. (48) Kamiya, Y.; Naito, Y.; Terada, K.; Mizoguchi, K. Volumetric properties and interaction parameters of dissolved gases in poly(dimethylsiloxane) and polyethylene. Macromolecules 2000, 33, 3111-3119. (49) Arcella, V.; Colaianna, P.; Maccone, P.; Sanguineti, A.; Gordano, A.; Clarizia, G.; Drioli, E. A study of perfluoropolymer purification and its application to membrane formation. J. Membr. Sci. 1999, 163, 203-209.



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Table Caption Table 1: Physical properties of Teflon AF1600 and Hylfon AD60. Table 2: Hydrocarbon diffusivity (x 1010 cm2/s) in perfluorinated polymers at 35 oC. Table 3: Dual-sorption parameters for hexane and toluene in Teflon AF1600 at 35 oC, along with CO2, CH4 and N2, previously reported by the authors 22. Table 4: Dual-sorption parameters for hexane and toluene in Hyflon AD60 at 35 oC, along with CO2, CH4 and N2, previously reported by the authors 22.

Table 5: Single gas permeability and CO2/CH4 selectivity in Teflon AF1600 and Hyflon AD60 membranes. Table 6: Mixed gas permeability and CO2/CH4 selectivity in Teflon AF1600 and Hyflon AD60 membranes, for a 90% CH4 – 10% CO2 feed mixture.


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Figure Caption Figure 1: Chemical structures of Teflon AF1600 and Hyflon AD60. Figure 2: Hexane sorption kinetics into Teflon AF1600 (•) and Hyflon AD60 (■) at 35 oC. Figure 3: Toluene sorption kinetics into Teflon AF1600 (•) and Hyflon AD60 (■) at 35 oC.

Figure 4: Hexane and toluene sorption isotherms in Teflon AF1600 at 35 oC. Figure 5: Hexane and toluene sorption isotherms in Hyflon AD60 at 35 oC.

Figure 6: Henry’s law constants as a function of Lennard-Jones potential well depth parameter (ε/κT) for Teflon AF1600 (•) and Hyflon AD60 (•), along with those reported for other polymeric membranes (о) 9, 42-48

and are fitted to Equation 8.

Figure 7: CO2 permeability (barrer) in Teflon AF1600 exposed to hexane and toluene vapor at various activities, for 90% CH4 – 10% CO2 feed at 1000 kPa and 35 oC. Lines correspond to fits of Equation 4 for hexane (— —) and toluene (– – –). Figure 8: CO2 permeability (barrer) in Hyflon AD60 exposed to hexane and toluene vapor at various activities, for 90% CH4 – 10% CO2 feed at 1000 kPa and 35 oC. Lines correspond to fits of Equation 4 for hexane (— —) and toluene (– – –). Figure 9: CH4 permeability (barrer) in Teflon AF1600 exposed to hexane and toluene vapor at various activities, for 90% CH4 – 10% CO2 feed at 1000 kPa and 35 oC. Figure 20: CH4 permeability (barrer) in Hyflon AD60 exposed to hexane and toluene vapor at various activities, for 90% CH4 – 10% CO2 feed at 1000 kPa and 35 oC.



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Tables

Teflon AF1600

Hyflon AD60

Density (g/cm3)

1.84

1.91

FFV

0.29

0.17

Tg (oC)

15630

11049

Table 1

Fickian Diffusion Coefficient (x 1010 cm2/s) Hexane

Toluene

Teflon AF1600

4.2

11.5

Hyflon AD60

2.3

9.5

Table 2

Lennard-

Critical

KD

Jones Well

Temperature

(cm3/cm3 atm)

Depth

(Tc)

C’H (cm3/cm3)

b (atm-1)

(ε/κ) CO2

195.2

304.2

1.22 ± 0.16

15.4 ±2.1

0.10 ± 0.02

CH4

148.6

148.6

0.42 ±0.08

8.1 ± 1.7

0.07 ±0.02

N2

71.4

126.2

0.20 ±0.05

14.8 ± 2.9

0.03 ±0.01

Hexane

399.3

507.3

40 ± 7

5.4 ± 3.8

6.9 ± 4.6

Toluene

410

591.8

104 ± 41

7 ± 1.7

19 ± 15

Table 3


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Lennard-

Critical

KD

Jones Well

Temperature

(cm3/cm3

Depth

(Tc)

atm)

C’H (cm3/cm3)

b (atm-1)

(ε/κ) CO2

195.2

304.2

0.78 ±0.12

9.1 ± 1.9

0.13 ± 0.02

CH4

148.6

148.6

0.31 ±0.08

2.9 ± 0.4

0.08 ±0.02

N2

71.4

126.2

0.22 ±0.05

4.5 ± 0.7

0.03 ± 0.01

Hexane

399.3

507.3

3.31 ± 0.02

9.49 ± 0.03

1.420 ± 0.003

Toluene

410

591.8

16.3 ± 0.05

6.5 ± 0.02

9.21 ± 0.01

Table 4

CO2

CH4

CO2/CH4

Teflon AF1600

505 ± 14

39 ± 0.9

13

Hyflon AD60

101 ± 3

9.6 ± 0.2

11

CO2

CH4

CO2/CH4

Teflon AF1600

489 ± 13

42 ± 2.1

12

Hyflon AD60

96 ± 5

10 ± 0.9

10

Table 5

Table 6



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Figures

Figure 1


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Figure 2



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Figure 3


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Figure 4



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Figure 5


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Figure 6



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Figure 7


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Figure 8



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Figure 9


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Figure 20



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Teflon AF1600 and Hyflon AD60 CO2 permeability not impacted by the presence of hexane and toluene vapor. 200x100mm (96 x 96 DPI)

ACS Paragon Plus Environment

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