Fluorinated pyridinium and ammonium cationic surfactants

Article abstract of DOI:10.1016/j.jfluchem.2016.05.003

New classes of partially fluorinated cationic surfactants, including pyridinium sulfonates and ammonium hydrochlorides have been prepared in which a fluoroalkyl chain is interrupted either by ether oxygen (-O-), or by methylene (-CH₂-) units. These surfactants are obtained from multi-step syntheses via intermediate fluoroalkyl ethylene iodides (RfO(CF₂CF₂)nCH₂CH₂I, Rf = C₃F_7, C₂F_5, n = 1-3 or Rf(CH₂CF₂)m(CH₂CH₂)n, Rf = C₄F₉, C₆F_13m = 0-2, n = 1-2) or fluoroalkyl iodides (RfI, Rf = C₃F₇O(CF₂CF₂)₃I, C₆F₁₃). The surface activities of these fluorinated cationic surfactants were examined and compared to commercially available fluorinated cationic surfactants used as additives in oil field applications. Some examples demonstrated good performance relative to controls yet are more fluorine efficient because they have lower fluorine content than their perfluoroalkyl analogues. For the ammonium hydrochlorides, the effect of different spacer groups between the cation and the fluorinated chain including ethylene, butylene and isopropylidene on surface activity was also examined.

Full text of DOI:10.1016/j.jfluchem.2016.05.003

Accepted Manuscript
Title: Fluorinated Pyridinium and Ammonium Cationic
Surfactants
Author: Allison Yake Tanya Corder Kenneth Moloy Tim
Coope Charles Taylor Ming Hung Sheng Peng
PII:
S0022-1139(16)30105-1
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.jfluchem.2016.05.003
FLUOR 8773
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Revised date:
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27-4-2016
2-5-2016
Please cite this article as: Allison Yake, Tanya Corder, Kenneth Moloy, Tim
Coope, Charles Taylor, Ming Hung, Sheng Peng, Fluorinated Pyridinium
and Ammonium Cationic Surfactants, Journal of Fluorine Chemistry
http://dx.doi.org/10.1016/j.jfluchem.2016.05.003
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Fluorinated Pyridinium and Ammonium Cationic Surfactants
Allison Yake1 Tanya Corder1, Kenneth Moloy2, Tim Coope3, Charles Taylor1,
,
Ming Hung2 and Sheng Peng1*
1 The Chemours Company, Experimental Station, Wilmington, DE 19803, USA
2 E. I. DuPont de Nemours & Co., Experimental Station, Wilmington, DE 19803, USA
3 University of Bristol, Faculty of Engineering, Bristol BS8 1TR, UK
* Corresponding author: phone: (+ 1)-302-695-3097; Fax: (+ 1)-302-695-8347; E-mail:
sheng.peng@chemours.com
1

Highlights
Partially fluorinated pyridinium and ammonium cationic surfactants are

described.
The fluorinated chains are interrupted by -CH2- or -O- groups.
Aqueous surface tension and foaming of select candidates are
comparable to commercial benchmarks.


2

Graphical abstract
Syntheses of partially fluorinated pyridinium and ammonium cationic
surfactants containing methylene (-CH2-) or ether (-O-) groups are reported. The
aqueous surface tension reduction and foaming properties of these surfactants
are also described.
3

Abstract
New classes of partially fluorinated cationic surfactants, including
pyridinium sulfonates and ammonium hydrochlorides have been prepared in
which a fluoroalkyl chain is interrupted either by ether oxygen (-O-), or by
methylene (-CH2-) units. These surfactants are obtained from multi-step
syntheses via intermediate fluoroalkyl ethylene iodides (RfO(CF2CF2)nCH2CH2I,
Rf=C3F7, C2F5, n=1-3 or Rf(CH2CF2)m(CH2CH2)n, Rf=C4F9, C6F13 m=0-2, n=1-2)
or fluoroalkyl iodides (RfI, Rf=C3F7O(CF2CF2)3I, C6F13). The surface activities of
these fluorinated cationic surfactants were examined and compared to
commercially available fluorinated cationic surfactants used as additives in oil
field applications. Some examples demonstrated good performance relative to
controls yet are more fluorine efficient because they have lower fluorine content
than their perfluoroalkyl analogues. For the ammonium hydrochlorides, the effect
of different spacer groups between the cation and the fluorinated chain including
ethylene, butylene and isopropylidene on surface activity was also examined.
Keywords:
Fluorosurfactant, Fluorinated pyridinium salt, Fluorinated ammonium
hydrochloride, Surface tension, Foaming, Oil field.
4

1. Introduction
Fluorinated surfactants are a diverse class of surface activity agents. They
have a wide variety of applications due to their unique properties such as surface
tension reduction, wetting and leveling, exceptional stability in harsh
environments (high temperature, high and low pH), hydro- and oleophobicity, etc.
They are used as anti-blocking agents in architectural coatings, leveling and
wetting agents in paints, inks and floor finishes, aqueous firefighting foams, hard
surface cleaners, emulsifiers and dispersion aids for olefin polymerization, and
additives in oil and gas extraction fluids [1-9].
In contrast to their hydrocarbon counterparts, fluorinated surfactants often
exhibit significantly enhanced performance [8,10]. Hydrocarbon surfactants can
generally reduce aqueous surface tension to ca. 30 dyne/cm, whereas surface
tension reduction as low as 16 dyne/cm can be achieved with fluorosurfactants.
Moreover, at the same performance level, the use rate of fluorosurfacants is
much lower than that of hydrocarbon surfactants, 0.005-0.1 wt% versus 0.1-3
wt%, respectively. Fluorosurfactants possess outstanding stability in corrosive
environments. Fluorosurfactants have been designed to perform in organic,
acidic and basic media, while hydrocarbon surfactants are limited to aqueous
media. Furthermore the stability of the carbon fluorine bond also enables
fluorosurfacants to deliver performance at high temperatures and high pressures.
Fluorinated surfactants are comprised of two key structural components, a
-
hydro- and oleophobic perfluorinated carbon chain (e.g., F(CF2)n ), a hydrophilic
group, and optionally a spacer separating these two groups. In fluorinated
cationic surfactants, the cation is typically a quaternary ammonium group or a
protonated amine, including heterocycles [8]. Fluorinated cationic surfactants can
be highly effective surface tension reducing and foaming agents in acidic and salt
environments. Also, because they are positively charged they can be used to
modify negatively charged surfaces. For example, textile surfaces can be
5

modified with fluorinated cationic surfactants to reduce fiber-fiber, fiber-metal,
and fiber-ceramic coefficients of friction [11]. Fluorinated cationic surfactants are
additives in aqueous firefighting foams to improve foaming and formulation
drainage [8]. They also give improved yields in the emulsion polymerization of
olefins [12]. In the case of oil field applications, the oil and gas extraction is
conducted in a high temperature, high corrosion environment, and fluorinated
cationic surfactants function well in these extraction fluids due to their
outstanding thermal and chemical stability [9,13]. In this application, the positively
charged surfactant electrostatically absorbs to negatively charged surfaces such
as rock fines and sand proppant to reduce capillary forces and improve the
recovery of hydrocarbons (oil/gas) and/or the stimulation fluid used to open up
the formation. In addition, the cationic surfactant inhibits corrosion by forming a
protective film on the metal parts of the well [14].
Fluorinated surfactants are usually more expensive than hydrocarbon
surfactants. Although their unique performance attributes offset the added cost to
some degree, it is also desirable to increase the fluorine efficiency; i.e., boost the
performance of the surfactant so that lesser amounts of the expensive
fluorosurfactant are required to achieve the same or better level of performance.
It is thus desirable to reduce the chain length of the perfluoroalkyl groups or to
reduce the amount of fluorine within a partially fluorinated group, thereby
reducing the total fluorine present while still achieving the same or superior
surface effects.
Additionally, alternative fluorinated materials, including
surfactants, with improved environmental properties have been the subject of
significant recent attention and review [15-22].
We describe here the syntheses of a few novel fluorinated pyridinium
sulfonates and fluorinated ammonium chlorides in which the fluorinated carbon
chains are interrupted either by methylene (-CH2) or ether (e.g., -O-) linkages.
We further show that in comparison to their perfluorinated analogues, these
interrupted structures are more fluorine efficient with respect to their surface-
6

active properties. Such a design allows these surfactants to maintain the
chemical stability required for harsh application environments, while also
translating into reduced cost.
2. Results and Discussion
2.1 Synthesis of Fluoroalkyl Ethylene Iodides
The fluoroalkyl ethylene iodide synthesis is shown in Scheme 1 [23,24]. In
the case of fluoroalkyl chains interrupted with methylene groups, the thermal or
redox-initiated insertion of vinylidene fluoride (VDF) into fluoroalkyl iodide bonds
has been studied extensively by Ameduri and others [25-29]. Here a metal-
meditated vinylidene fluoride Insertion of fluoroiodide, followed by radical-
mediated ethylene insertion is employed [24]. Access to the fluorinated ethers
was accomplished by reaction of perfluorovinyl ether with I2 and IF5 to give the
fluorinated ether iodides [24], subsequent thermal telomerization with
tetrafluoroethylene to extend the chain length, and then insertion of one
equivalent of ethylene. The example of a double ethylene insertion in the case of
C6F13(CH2CH2)2I was achieved by reaction of C6F13I and ethylene in the
presence of radical initiator [30]. Fractional distillation was applied in each step
for material purification.
Insert Scheme 1
7

Scheme 1 Synthesis of Fluoroalkyl Ethylene Iodides
2.2 Synthesis of Fluorinated Pyridinium Surfactants
o
The fluoroalkyl ethylene iodides were heated with pyridine at 80 C for 20
hours (Scheme 2). The resulting pyridinium iodide was filtered, washed with ethyl
acetate, and dried in the vacuum oven overnight. Yields range from 70 to 95%.
o
Treating this intermediate with p-toluene sulfonic acid in methanol at 70 C for
24-48 hours offered the final product in quantitative yields. In this step methyl
iodide and water are generated and constantly removed by distillation to drive the
reaction to completion (Scheme 3). These reactions are conveniently followed by
periodic gas chromatography of the distillate to monitor the methyl iodide removal.
In addition to driving the equilibrium to products, the water stripping may be
important to prevent leveling of the acid catalyst and potential inhibition of the
reaction rate.
8

Insert Scheme 2
Scheme 2 Synthesis of Fluorinated Pyridinium Surfactants
Insert Scheme 3
Scheme 3 Reaction of Fluorinated Pyridinium Iodides with p-Toluene Sulfonic
Acid
The above fluorinated pyridinium salts were subjected to performance
tests as 50 wt% solutions in methanol.
2.3 Synthesis of Fluorinated Ammonium Surfactants
9

Fluoroalkyl azides with an ethylene spacer were prepared in moderate
yields by the biphasic reaction of fluoroalkyl ethylene iodides and sodium azide in
o
the presence tetrabutylammonium bromide as phase transfer catalyst at 100 C.
Raney nickel and hydrazine reduction of the azide intermediates was used to
generate the free amines, followed by acidification with HCl to provide the
fluoroalkyl ammonium chlorides (Scheme 4).
Insert Scheme 4
Scheme 4 Synthesis of Fluorinated Ethylene Ammonium Surfactants
The synthesis of fluoroalkylamines with isopropylidene spacers was first
reported by Feiring [31]. The same methodology was applied here to prepare the
fluoroether analogues (Scheme 5). Thus, tetrabutylammonium nitropropanide
o
(generated from tetrabutylammonium hydroxide and 2-nitropropane at 85-95 C)
was used to convert C3F7O(CF2CF2)3I to C3F7O(CF2CF2)3C(CH3)2NO2. This was
then reduced to C3F7O(CF2CF2)3C(CH3)2NH2 with hydrogen over Pd/C catalyst.
10

After catalyst removal the amine was purified by distillation. HCl was added to
the amine to form the final ammonium chloride salt.
Insert Scheme 5
Scheme 5 Synthesis of Fluorinated Isopropylidene Ammonium Surfactants
2.3 Cationic Fluorosurfactant Performance
2.3.1 Surface Tension
2.3.1.1 Surface Tension in Deionized Water
The fluorinated pyridinium salt and fluorinated ammonium salts described
above were diluted into water at different concentrations for surface tension
measurement and evaluation (Table 1-2 and Figure 1-3).
Insert Table 1
Insert Figure 1
11

Table 1 Surface Tensions* (dyne/cm) of Fluorinated Pyridinium Cationic
Surfactants in Deionized Water at 23 oC
Concentration (wt% of surfactant)
Surfactants
F (wt %)
0.001
0.01
0.1
0.5
[C3F7OCF2CF2CH2CH2py][p-CH3C6H4SO3] (I-B)
[C4F9CH2CF2CH2CH2py][p-CH3C6H4SO3] (II-B)
[C4F9(CH2CF2)2CH2CH2py][p-CH3C6H4SO3] (III-B)
[C6F13CH2CF2CH2CH2py][p-CH3C6H4SO3] (IV-B)
[C6F13(CH2CF2)2CH2CH2py][p-CH3C6H4SO3] (V-B)
[RfCH2CH2py][p-CH3C6H4SO3] (Formulation I**)
[RfCH2CH2py][p-CH3C6H4SO3] (Formulation II***)
[C6F13CH2CH2py][p-CH3C6H4SO3] (VI-B)
37.1
37.3
39.5
43.1
44.5
43.2
43.4
41.4
46.3
72.1
72.1
64.9
67.7
41.0
43.1
21.6
22.8
72.3
69.5
64.2
68.9
67.8
59.9
45.6
34.7
43.0
40.6
30.5
18.3
18.8
18.1
18.2
19.5
17.2
18.3
17.5
17.6
65.9
60.9
51.4
30.6
27.5
17.2
18.8
17.0
[C8F17CH2CH2py][p-CH3C6H4SO3] (Control)
* The average of 10 replicates is reported; the standard deviation is <1 dyne/cm
** Formulation I is a mixture of IV-B and V-B (90:10 mol ratio)
*** Formulation II is a mixture of IV-B and V-B (80:20 mol ratio)
12

Figure 1 Aqueous Surface Tension of Fluorinated Pyridinium
Cationic Surfactants
The surface tension of deionized water is 72 dyne/cm at 23 oC. When the
above fluorinated pyridinium cationic surfactants are added at the specified levels,
they exhibited different level of surface tension reduction. As shown in Table 1
and Figure 1, surfactants I-B, II-B, III-B and VI-B are not as effective as the
control
example
[n-C8F17CH2CH2py][p-CH3C6H4SO3]
until
reaching
concentrations as high as 0.5%. IV-B performs equally to the control in the
concentration range 0.1-0.5%, but is inferior below 0.1%. V-B has the strongest
surface tension reduction among all the new surfactants, demonstrating
performance only slightly below the control at all tested concentrations. Mixtures
of IV-B and V-B give improved performance over pure IV-B, even with only small
amounts of V-B added.
13

Insert Table 2
Table 2 Surface Tensions* (dyne/cm) of Fluorinated Ammonium Cationic
Surfactants in Deionized Water at 23 oC
Concentration (wt% of surfactant)
Surfactants
F (wt%)
0.001
0.01
0.1
0.5
Group I
[C3F7OCF2CF2CH2CH2NH3][Cl] (I-D)
[C3F7O(CF2CF2)2CH2CH2NH3][Cl ](II-D)
[C3F7O(CF2CF2)3CH2CH2NH3][Cl] (III-D)
[C3F7O(CF2CF2)3C(CH3)2NH3][Cl] (IV-D)
[C2F5O(CF2CF2)2CH2CH2NH3][Cl] (V-D)
[C2F5O(CF2CF2)3CH2CH2NH3][Cl] (VI-D)
[RfCH2CH2 NH3][Cl] (Control**)
Group II
57.2
61.2
63.8
62.3
59.4
62.6
65.8
71.7
67.2
52
68.8
47.6
35.2
68.3
59.2
27.9
30.3
59.1
25.8
16.4
54.7
36.2
16.9
23.7
38.1
14.3
14.8
28
71.2
69.7
57.3
67.1
14.6
15.5
20.9
[C6F13CH2CH2NH3][Cl] (VII-D)
[C6F13(CH2CH2)2NH3][Cl] (VIII-D)
[C6F13C(CH3)2NH3][Cl] (IX-D)
61.8
57.8
59.7
61.5
65.8
70.1
70.9
71.4
65.7
67.1
64.4
54.9
63.9
48.1
30.3
47.8
33.4
38.3
29.1
23.7
23.8
15.1
18.5
14.9
20.9
[C6F13CH2CF2CH2CH2NH3][Cl] (X-D)
[RfCH2CH2 NH3][Cl] (Control**)
* The average of 10 replicates is reported; the standard deviation is <1 dyne/cm
** Rf is the mixture of C8F17 and C10F21 (45:55 mol ratio)
Insert Figure 2
Insert Figure 3
14

Figure 2 Aqueous Surface Tension of Fluoroether Ammonium
Cationic Surfactants (Group I)
15

Figure 3 Aqueous Surface Tension of Fluorinated (C6F13) Ammonium
Cationic Surfactants (Group II)
To more closely examine the correlation between surfactant structure and
surface tension, the surface tension results of fluorinated ammonium cationic
surfactants were divided into two structural groups. Group I ammonium
surfactants are a variety of fluoroethers of variable chain length and Group II
ammonium surfactants are centered on analogues with different spacers
between a fixed, linear C6F13 chain and the ammonium cation. From results
shown in Table 2 and Figure 2, in general the surface tension reduction capability
of a Group I surfactant is proportional to the fluoroether chain length and the
fluorine content. I-D, II-D and V-D show significant performance gaps compared
with the control surfactant (RfCH2CH2 NH3][Cl], where Rf is a mixture of n-C8F17
and n-C10F21). Excellent surface tension reduction is observed with III-D and VI-D,
16

which are equal to or better than the control even though both possess lower
fluorine content (mass basis). It is worth noting that III-D and IV-D exhibit
dramatic surface activity difference although the only structural difference is the
hydrocarbon spacer, ethylene vs. isopropylidene group, respectively. While III-D
excels in surface tension reduction, IV-D shows only moderate performance
especially the concentration range 0.001 to 0.1%. There two possible
explanations for this phenomenon [32]. The isopropylidene group interrupts the
crystalline structure of the surfactant, and thus surfactant IV-D does not align or
pack well at the liquid-air interface. As a result, the surface tension reduction is
not as effective as for III-D, which is better able to align/pack. It is also possible
that the isopropylidene group diminishes the hydrophilicity of the ammonium ion,
thus disrupting the hydrophilic-lipophilic balance.
As indicated in Table II and Figure III, the Group II ammonium surfactants
reduce the surface tension of water significantly. Although better performance
was obtained at higher concentrations, none of the members of this group of
surfactants outperform the control. Given the fixed fluorinated carbon chain
(C6F13), the differences seen among these surfactant are rather interesting.
Doubling the alkylidene spacer to butylene in VIII-D boosted its surface tension
reducing ability relative to the ethylene spacer in VII-D. The isopropylidene
spacer in IX-D provides performance lying between the ethylene and butylene
spacers. The best performer in this group is X-D in which the spacer is -
CH2CF2CH2CH2-. It appears that the dipole provided by difluoromethylene group
helps this matter, possibly by enhancing the ability of this surfactant to align and
pack at the air-water interface [32].
2.3.3.2 Surface Tension in Aqueous KCl and HCl
Surface tension measurement in 15% HCl and 2% KCl is used to indicate
surfactant efficacy in oil well applications. The 2% KCl solution mimics the salinity
of the fluids that are used to hydraulically fracture a well. The 15% HCl solution
17

emulates the acidic stimulation treatment fluids that are used to dissolve the
formation rock in wells. At a given concentration, the surfactant with the lower
surface tension will help provide improved fluid penetration and recovery for
oilfield stimulation fluids [9,33].
The fluorinated pyridinium surfactants were tested for surface tension as
2% KCl aqueous and 15% HCl aqueous solutions as a function of surfactant
concentration. These results are summarized in Tables 3-4 and Figures 4-5.
Insert Table 3
Insert Figure 4
Insert Table 4
Insert Figure 5
18

Table 3 Surface Tensions* (dyne/cm) of Fluorinated Pyridinium Cationic
Surfactants in 2% Aqueous KCl at 23 oC
Concentration (wt% of surfactant)
Surfactants
F (wt%)
0.001
0.01
0.1
0.5
[C3F7OCF2CF2CH2CH2py][p-CH3C6H4SO3] (I-B)
[C4F9CH2CF2CH2CH2py][p-CH3C6H4SO3] (II-B)
[C4F9(CH2CF2)2CH2CH2py][p-CH3C6H4SO3] (III-B)
[C6F13CH2CF2CH2CH2py][p-CH3C6H4SO3] (IV-B)
[C6F13(CH2CF2)2CH2CH2py][p-CH3C6H4SO3] (V-B)
[RfCH2CH2py][p-CH3C6H4SO3] (Formulation I**)
[RfCH2CH2py][p-CH3C6H4SO3] (Formulation II***)
[C6F13CH2CH2py][p-CH3C6H4SO3] (VI-B)
37.1
37.3
39.5
43.1
44.5
43.2
43.4
41.4
46.3
68.5
54.5
66.5
54.5
42.3
53.7
52.8
65.9
41.2
57.4
32.2
51.0
32.2
19.4
28.2
25.4
51.4
20.1
40.0
18.6
28.1
18.6
18.2
18.3
18.4
27.5
17.9
21.8
17.5
20.0
17.5
17.6
17.4
17.7
18.8
17.0
[C8F17CH2CH2py][p-CH3C6H4SO3] (Control)
* The average of 10 replicates is reported; the standard deviation is <1 dyne/cm
** Formulation I is a mixture of IV-B and V-B (90:10 mol ratio)
*** Formulation II is a mixture of IV-B and V-B (80:20 mol ratio)
19

Figure 4 Surface Tensions of Fluorinated Pyridinium Cationic
Surfactants in 2% KCl
20

Table 4 Surface Tensions (dyne/cm) of Fluorinated Pyridinium Cationic
Surfactants in 15% Aqueous HCl at 23 oC
Concentration (wt% of surfactant)
Surfactants
F (wt%)
0.001
67.0
0.01
54.8
0.1
0.5
[C3F7OCF2CF2CH2CH2py][p-CH3C6H4SO3] (I-B)
[C4F9CH2CF2CH2CH2py][p-CH3C6H4SO3] (II-B)
37.1
37.3
39.1
25.2
70.0
65.4
60.5
44.4
28.5
[C4F9(CH2CF2)2CH2CH2py][p-CH3C6H4SO3] (III-B) 39.5
49.1
29.9
29.3
20.0
22.8
19.0
[C6F13CH2CF2CH2CH2py][p-CH3C6H4SO3] (IV-B)
[C6F13(CH2CF2)2CH2CH2py][p-CH3C6H4SO3] (V-B) 44.5
[RfCH2CH2py][p-CH3C6H4SO3] (Formulation I**) 43.2
[RfCH2CH2py][p-CH3C6H4SO3] (Formulation II***) 43.4
43.1
51.7
41.7
51.5
50.5
63.7
37.9
19.1
18.6
19.7
19.6
26.8
19.2
18.6
18.9
18.8
22.8
18.4
26.0
24.4
47.8
19.2
[C6F13CH2CH2py][p-CH3C6H4SO3] (VI-B)
[C8F17CH2CH2py][p-CH3C6H4SO3] (Control)
41.4
46.3
* The average of 10 replicates is reported; the standard deviation is <1 dyne/cm
** Formulation I is a mixture of IV-B and V-B (90:10 mol ratio)
*** Formulation II is a mixture of IV-B and V-B (80:20 mol ratio)
21

Figure 5 Surface Tensions of Fluorinated Pyridinium Cationic
Surfactants in 15% HCl
The normal surface tension of 2% aqueous KCl is 73 dyne/cm and 76
dyne/cm for 15% aqueous HCl. Similarly to their performance in deionized water,
these surfactants showed vast performance differences. Compared to the control,
poor performance was obtained with I-B, II-B, III-B and VI-B. Good surface
tension reduction was observed with IV-B, and V-B performed as well as the
control. Again, IVB performance can be improved by formulating 10-20 wt% V-B
into IV-B.
2.3.3 Foaming
Foaming is an essential property of surfactants used as drilling fluid
additives as well as for foamed hydraulic fracturing stimulation activities.
Foaming during drilling aids in the removal of fines from the well around the drill
22

bit. If these fines are not efficiently removed, they can cause damage to the drill-
bit head, costing time and money [33,34]. The addition of the fluorosurfactant
boosts the drilling fluid foaming properties. The cutting bit is lubricated with
stable foam which aids in carrying cuttings up to the surface. Lower pressure can
be applied to the formulation when using a foam drilling fluid which is particularly
important when drilling into low pressure reservoirs. The unique thermal and
chemical stability of fluorinated surfactants render them well suited for harsh
drilling environments. The use of foams (with surfactants and minimal amounts of
water) in hydraulic fracturing allows for reduced water use, treatment, and
disposal, by improving the efficacy of the stimulation fluid removal from down
hole. The blender foaming test is used as an indicator of the amount of foam that
a sample produces as well as the persistence of that foam. The test is also
performed in 2% KCl aqueous and 15% HCl aqueous solutions to mimic the
stimulation fluid types that are pumped down hole into wells. The test results are
listed in Table 5-7.
Insert Table 5
Insert Table 6
Insert Table 7
23

Table 5 Foaming of Fluorinated Pyridinium Cationic Surfactants in Water
F
Foam Volume (mL)
Sample ID
(wt%)
37.1
37.3
39.5
43.1
44.5
43.2
43.4
41.4
46.3
t=30
sec
t = 5
min
t= 10 t =15
Initial
105
min
min
[C3F7OCF2CF2CH2CH2py][p-CH3C6H4SO3]
0
0
0
0
0
0
(I-B)
[C4F9CH2CF2CH2CH2py][p-CH3C6H4SO3]
(II-B)
108
105
100
106
105
103
98
0
0
[C4F9(CH2CF2)2CH2CH2py][p-CH3C6H4SO3]
(III-B)
10
93
105
97
98
13
100
5
0
0
[C6F13CH2CF2CH2CH2py][p-CH3C6H4SO3]
(IV-B)
87
97
88
84
7
77
91
73
74
2
75
73
65
68
0
[C6F13(CH2CF2)2CH2CH2py][p-CH3C6H4SO3]
(V-B)
[RfCH2CH2py][p-CH3C6H4SO3]
(Formulation I**)
[RfCH2CH2py][p-CH3C6H4SO3]
(Formulation II***)
[C6F13CH2CH2py][p-CH3C6H4SO3]
(VI-B)
[C8F17CH2CH2py][p-CH3C6H4SO3]
(Control)
106
97
86
73
* Sample was added to deionized water by weight based on solids of the additive in methanol to
make 100 mL 0.1% solution
** Formulation I is a mixture of IV-B and V-B (90:10 mol ratio)
*** Formulation II is a mixture of IV-B and V-B (80:20 mol ratio)
24

Table 6 Foaming of Fluorinated Pyridinium Cationic Surfactants in 2% KCl
Aqueous Solution
Sample ID
Foam Volume (mL)
F
t=30
sec
t = 5 t= 10 t =15
(wt%)
Initial
117
110
110
110
106
110
113
104
111
min
min
min
[C3F7OCF2CF2CH2CH2py][ p-CH3C6H4SO3]
37.1
37.3
39.5
43.1
44.5
43.2
43.4
41.4
46.3
0
0
0
0
(I-B)
[C4F9CH2CF2CH2CH2py][ p-CH3C6H4SO3]
(II-B)
0
0
2
0
0
[C4F9(CH2CF2)2CH2CH2py][ p-CH3C6H4SO3]
(III-B)
71
0
0
[C6F13CH2CF2CH2CH2py][ p-CH3C6H4SO3]
(IV-B)
101
101
102
105
44
99
91
99
101
4
88
71
89
89
3
75
66
78
78
3
[C6F13(CH2CF2)2CH2CH2py][ p-CH3C6H4SO3]
(V-B)
[RfCH2CH2py][ p-CH3C6H4SO3]
(Formulation I)
[RfCH2CH2py][ p-CH3C6H4SO3]
(Formulation II)
[C6F13CH2CH2py][ p-CH3C6H4SO3]
(VI-B)
[C8F17CH2CH2py][ p-CH3C6H4SO3]
(Control)
101
101
81
76
* Sample was added to 2% KCl aqueous solution by weight based on solids of the additive in
methanol to make 100 mL 0.1% solution
25

Table 7 Foaming of Fluorinated Pyridinium Cationic Surfactants in 15% HCl
Aqueous Solution
Foam Volume (mL)
F
Sample ID
(wt%)
t=30 t = 5 t= 10 t =15
Initial
sec
min
min
min
[C3F7OCF2CF2CH2CH2py][ p-CH3C6H4SO3]
37.1
37.3
39.5
43.1
44.5
43.2
43.4
41.4
46.3
112
111
117
118
116
114
108
118
116
1
0
0
0
(I-B)
[C4F9CH2CF2CH2CH2py][ p-CH3C6H4SO3]
(II-B)
0
0
0
0
[C4F9(CH2CF2)2CH2CH2py][ p-CH3C6H4SO3]
(III-B)
102
105
107
108
102
103
106
41
21
11
[C6F13CH2CF2CH2CH2py][ p-CH3C6H4SO3]
(IV-B)
101
106
106
101
48
99
99
[C6F13(CH2CF2)2CH2CH2py][ p-CH3C6H4SO3]
(V-B)
106
106
101
28
106
106
101
19
[RfCH2CH2py][ p-CH3C6H4SO3]
(Formulation I)
[RfCH2CH2py][ p-CH3C6H4SO3]
(Formulation II)
[C6F13CH2CH2py][ p-CH3C6H4SO3]
(VI-B)
[C8F17CH2CH2py][ p-CH3C6H4SO3]
(Control)
106
106
106
* Sample was added to 15% HCl aqueous solution by weight based on solids of the additive in
methanol to make 100 mL 0.1% solution
The foaming tests follow the trends observed in the surface tension
studies. Thus, I-B, II-B and III-B did not provide persistent, stable foams in the
test. V-D showed equal performance to the control. IV-D performance was
between VI-D and V-D, and improvement can be obtained by formulating a small
percentage of V-D into IV-D. Overall V-D, Formulation I, and Formulation II
demonstrated comparable performance to the control. From a practical point of
view, using a mixture of IV-D and V-D is cost beneficial as these are coproducts
26

resulting from the insertion of vinylidene fluoride into 1,1,1,2,2,3,3,4,4,5,5,6,6-
tridecafluoro-6-iodohexane.
3. Conclusions
Fluorinated pyridinium and ammonium cationic surfactants have been
prepared in moderate to good yields, where the organofluorinated chain is
interrupted with methylene or ether oxygen groups and the hydrocarbon spacer
is ethylene, butylene or isopropylidene. These novel fluorosurfactants have
lower fluorine content (wt% basis) and therefore are more fluorine efficient than
their perfluoroalkyl analogues. Aqueous surface tension and foaming of these
new fluorinated cationic surfactants were tested.
4. Experimental
4.1 General
Nonfluorinated starting materials and solvents were obtained from Sigma-
Aldrich Inc., St. Louis, MO, EMD Chemicals Inc. (Merck KGaA, Darmstadt,
Germany) and Alfa Aesar, Ward Hill, MA. Perfluoroalkyl iodides, perfluorovinyl
ether, vinylidene fluoride, tetrafluoroethylene, and iodine pentafluoride were from
E. I. du Pont de Nemours. All reagents were used without further purification.
Nuclear magnetic resonance spectra of hydrogen nuclei were recorded
using a Bruker Avance DRX® (400 MHz) and fluorine-19 nuclei using a Bruker
Avance DRX® (376 MHz). Abbreviations for coupling patterns are as follows: s
(singlet), d (doublet), t (triplet), tt (triplet of triplets), q (quartet), quin (quintet) and
m (multiplet). Elemental analysis was performed by Micro Analysis Inc.,
Wilmington, DE 19808. Mass spectra (MS) were obtained using an Agilent
Technologies 5973 Network mass selective detector coupled to an Agilent
Technologies 6890N Network GC System. In this document: F wt% is the weight
percentage of fluorine in the pure active ingredient.
27

4.2 Performance Test Methods
4.2.1 Surface tension was measured according to the American Society for
Testing and Materials ASTM D1331-56, using the Wilhelmy plate method on a
KRUSS K11 Version 2.501 tensiometer (KRUSS USA, Matthews NC) in
accordance with the vendor-provided instructions. A vertical plate of known
perimeter was attached to a balance, and the force due to wetting was
measured. Ten replicates were tested at each surfactant concentration, and the
following machine settings were used:
Method: Plate Method SFT
Interval: 1.0 s
Wetted length: 40.2mm
Reading limit: 10
Min Standard Deviation: 2 dynes/cm
Gr. Acc.: 9.80665 m/s2
Results are reported in dynes/cm (mN/m) and standard deviations were
less than 1 dyne/cm.
A stock solution is prepared for the highest concentration of
fluorosurfactant to be analyzed. The concentration of the solution is by percent
active ingredient, based on either weight percentage or fluorine content. This
stock solution is prepared in de-ionized water, 2% KCl, or 15% HCl depending on
the desired application for which the surface tension is being measured. The
stock solution is stirred overnight (for approximately 12 hours) to ensure
complete mixing. Additional concentrations of the fluorosurfactant for analysis
are made by diluting the stock solution. The diluted samples are shaken
thoroughly and then left undisturbed for 30 minutes. These samples are then
remixed and subjected to the analysis with the Krus 11 Tensiometer.
28

4.2.2 A modified version of ASTM D3519-88 was used to quantitfy foaming
performance. A blender, graduated cylinder, glass sample bottles and a stop
watch were employed. Samples (100 mL) of the fluorosurfactant at 0.1 wt%
concentration were prepared in deionized water, 2% KCl, and 15% HCl and
stirred overnight to ensure complete mixing. The blender was rinsed with
deionized water, then acetone, and then de-ionized water again. The test fluid
sample was added to the blender jar and the temperature recorded. The blender
was then run for 20 seconds at 50-60% power. After 20 seconds, the liquid and
foam were immediately poured into a 500 mL graduated cylinder. The initial liquid
and foam heights were measured immediately and then again at 5, 10 and 15
min intervals. During this time, any observations of the foam such as its density
or persistency were recorded. The variability in these foam height data is 10 mL.
4.3 Fluoroalkyl ethyl iodides RfCH2CH2I (Rf=C4F9CH2CF2, C4F9(CH2CF2)2,
C6F13CH2CF2, C6F13(CH2CF2)2), C6F13(CH2CH2)2I and C3F7OCF2CF2CH2CH2I
were prepared according to literature methods[23,24,30].
4.4 Synthesis of 1,1,2,2,3,3,4,4-octafluoro-1-iodo-4-(heptafluoropropoxy)butane
C3F7OCF2CF2CF2CF2I
and
1,1,2,2,3,3,4,4,5,5,6,6-dodecafluoro-1-iodo-6-
(heptafluoropropoxy)hexane C3F7OCF2CF2CF2CF2CF2CF2I
Tetrafluoroethylene (180 g, 1.8 mol) was introduced to an autoclave
charged with C3F7OCF2CF2I (600 g, 1.46 mol), and the reactor was heated at
230 ºC for 2 h. The reaction was repeated two more times. The products were
combined and isolated by vacuum distillation to provide C3F7OCF2CF2CF2CF2I
(370 g, 29%) and C3F7OCF2CF2CF2CF2CF2CF2I (234 g, 18%) based on
o
recovered starting material. C3F7OCF2CF2CF2CF2I: b.p. 63-66 C at 60 mmHg;
19F NMR (CDCl3, 376 MHz,): δ -65.63 - -65.75 (2F, m), -82.65 (3F, t, J=7.3 Hz), -
84.41 - -84.54 (2F, m), -85.34 - -85.47 (2F, m), -115.07 (2F, s), -125.49 - -125.61
(2F, m), -131.03 (2F, s); MS (PCI): 513(M++1); C7F15OI (511.88); Calc. C 16.41 F
19
55.67; Found C 16.57 F 56.95. C3F7OCF2CF2CF2CF2CF2CF2I: F NMR (CDCl3,
29