Binary Diffusion Coefficients of Platinum(II) Acetylacetonate in

Article pubs.acs.org/jced

Binary Diffusion Coefficients of Platinum(II) Acetylacetonate in Supercritical Carbon Dioxide Chang Yi Kong,† Tomoya Siratori,† Guosheng Wang,‡ Takeshi Sako,† and Toshitaka Funazukuri*,§ †

Department of Applied Chemistry and Biochemical Engineering, Graduate School of Engineering, and Research Institute of Green Science and Technology, Shizuoka University, 3-5-1 Johoku Naka-ku, Hamamatsu 432-8561, Japan ‡ College of Chemical Engineering, Shenyang University of Chemical Technology, 11st. Shenyang Economic and Technological Development Zone, Shenyang, 110142, China § Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo, 112-8551, Japan ABSTRACT: Binary diffusion coefficients (D12) and retention factors (k) of platinum(II) acetylacetonate at infinitesimal concentration in supercritical (sc) carbon dioxide (CO2) were measured by the chromatographic impulse response method with a poly(ethylene glycol) coated capillary column at temperatures from (308.15 to 343.15) K and pressures from (8.5 to 40.0) MPa, and D12 in liquid ethanol at temperatures from (298.15 to 333.15) K and atmospheric pressure by the Taylor dispersion method. As has been seen for our previously reported data on other metal complexes measured in sc CO2 and organic solvents, the D12 data in sc CO2 and liquid ethanol were represented by a function of temperature and solvent viscosity. The D12 values for metal complexes were not related to the solute molecular weights. The k values in sc CO2 were expressed by a function of temperature and CO2 density.

reliable D12 values can be determined in the CIR method.12 In the case when the response curves without tailing are obtained, the diffusion coefficients determined in both methods are almost consistent.12 Moreover, in the CIR method an ethanol solution of Pt(acac)2 can be injected because the ethanol and Pt(acac)2 are chromatographically separated in the polymercoated diffusion column. Thus, in the present study at infinitesimal concentration the values of D12 and retention factors (k) of platinum acetylacetonate(II) in sc CO2 were measured by the CIR method, and D12 in liquid ethanol by the Taylor dispersion method. Moreover, the validities of predictive correlations as a function of temperature and solvent viscosity, and that of temperature and CO2 density, respectively, were examined.

1. INTRODUCTION Organometallic complexes are widely used for metal deposition, impregnation, and composites as transport media of metal in supercritical (sc) fluids due to the high solubility as compared to the metal itself.1−3 In particular, a platinum complex, such as platinum acetylacetonate (Pt(acac)2), is an important compound used in the impregnation and deposition of platinum or its nanoparticles onto surface of catalysts or precursors.3−8 For the optimization and design of these processes, diffusion coefficients of platinum complexes in sc CO2 are needed. However, no data have been reported yet in the literature. We have already measured at infinitesimal concentration binary diffusion coefficients (D12) of various metal complexes such as ferrocenes,9,10 Co(acac)3,10,11 Pd(acac)2,10,11 Rh(acac)3,10 and Ru(acac)310 in sc CO2 and/or liquid organic solvents by the chromatographic impulse response (CIR) method and/or the Taylor dispersion method. Both methods are transient response techniques in which a solute species is injected to a solvent flowing in a capillary column and the solute concentration is monitored downstream as a response signal. The parameters, diffusion coefficient in the Taylor dispersion method, and diffusion coefficient and retention factor in the CIR method are determined as to fit the response curve calculated from the theoretical model to that measured experimentally. An uncoated capillary column and a polymer-coated capillary column are employed in the Taylor dispersion and CIR methods, respectively. When the response curve tails due to adsorption of a solute species onto the inner walls of a diffusion column in the Taylor dispersion, the tailing can be reduced, and more © 2013 American Chemical Society

2. EXPERIMENTAL SECTION 2.1. Chemicals. The chemicals used in this study are listed in Table 1. These were used without further purification. 2.2. Procedures. The apparatus for the CIR measurements is substantially the same as that reported in our previous study.9,11−13 An open capillary diffusion column (UACW-15W1.0F, the Frontier Laboratories Ltd., Japan, radius R = 0.265 mm, length L = 16.248 m, and coil radius Rcoil = 155.0 mm) was employed as a chromatographic column in this study. It was Received: April 3, 2013 Accepted: September 25, 2013 Published: October 15, 2013 2919

dx.doi.org/10.1021/je400313n | J. Chem. Eng. Data 2013, 58, 2919−2924

Journal of Chemical & Engineering Data

Article

the column. In the case of the Taylor dispersion let k = 0 in eq 1. In this study, the curve fitting technique was used in determining the D12 and k values simultaneously in the CIR method and the D12 values in the Taylor dispersion method as to minimize the root-mean-square (rms) fitting error ε, which is a criterion for fit defined by eq 2,16,17 between the measured cexp(t) and predicted c(t) curves.

Table 1. Name, Source, and Purity of Chemicals Employed in This Study chemical name

source (location)

platinum acetylacetonate ethanol

Sigma-Aldrich Japan (Tokyo, Japan) Wako Pure Chemical Ind. (Tokyo, Japan) Marukyo Sanso (Hamamatsu, Japan)

carbon dioxide a

puritya

further purification

99%

none

99.50%

none

99.99%

none

t

The values were reported by the manufacturers.

ε=

∫t 2 (cexp(t ) − c(t ))2 dt 1

t

∫t 2 (cexp(t ))2 dt 1

chemically bonded on the column inner surface with poly(ethylene glycol) 20 M (PEG20M, polymer thickness of 1 μm), which was utilized as a stationary phase. When the Taylor dispersion measurement was carried out, the diffusion column was replaced with a bright annealed 316 stainless-steel column (GL Sciences Inc., Japan, R = 0.416 mm, L = 16.634 m, and Rcoil = 157.5 mm). Carbon dioxide used as a mobile phase was fed by a syringe pump (260D, ISCO) to a preheating column, an injector (model 7520, equipped with a 1.0 μL rotor, Rheodyne), and the diffusion column, all of which were immersed in a constant temperature water bath (T-105, Thomas Kagaku Co., Ltd., Japan). The temperature was maintained at the prescribed value within ± 0.01 K. The pressure of the system was regulated within mainly ± 5 kPa, ± 10 kPa at most, by the syringe pump and a back pressure regulator (model SCF-Bpg/M with modification, JASCO, Japan). A packed column was installed as a damper upstream at the regulator to stabilize the pressure of the system. Note that the pressure drop throughout the diffusion column was less than 5 kPa. Once the system had reached the desired temperature and pressure, a single pulse of Pt(acac)2 dissolved in ethanol (1.0 μL of a 8.0 g·L−1 ethanol solution of Pt(acac)2) was loaded through the injector into the column for each measurement. The chromatographic peaks were monitored with a detector (MD 1510, JASCO, Japan) by scanning at wavelengths from (200 to 350) nm, and the flow rate of CO2 was measured with a soap bubble flow meter. Measurements were made at (308.15, 313.15, 323.15, 333.15, and 343.15) K and pressures from (8.51 to 40.00) MPa. 2.3. Analyses. When a solute component is pulse-injected into a fluid which is at fully developed laminar flow in a polymer coated capillary column in the CIR method or in an uncoated capillary column in the Taylor dispersion, the response curve of a solute concentration is governed by a fundamental equation, and the average concentration c(t) is described as follows:9,11−15 ⎧ u0 ⎪ L − 1+kt ⎛ m ⎞ 1 ⎜ ⎟ c(t ) = exp⎨− ⎝ πR2 ⎠ (1 + k) 4πat 4at ⎪ ⎩

(

2

where t1 and t2 correspond to the times at the front and latter 10 % peak heights, respectively, of the measured curve.

3. RESULTS AND DISCUSSION 3.1. Response Curve. Figure 1 shows typical response curves measured experimentally and calculated from eq 1 with a

Figure 1. Typical chromatographic response curves measured (solid) at a wavelength of 240 nm and calculated (dotted) for Pt(acac)2 in sc CO2 at 313.15 K and 11.00 MPa.

of 2.741·10−5 m2·s−1, k of 1.218, and u0 of 8.852·10−3 m·s−1 for Pt(acac)2 in sc CO2 at a wavelength of 240 nm, 313.15 K, and 11.00 MPa. The quality of fitting the theoretical curve to the experimental curve can be judged from the ε value, and intuitively from Figure 1. As shown, the injected ethanol solution of Pt(acac)2 was chromatographically separated into ethanol and Pt(acac)2 while flowing through the column due to different retention factors. It was in excellent agreement with ε of 0.67 % that was obtained between the experimentally measured and theoretically calculated curves for Pt(acac)2 using the CIR curve fitting technique. Note that the injected amount of Pt(acac)2 was 2.0·10−2 μmol in the present measurements. According to our previous study,16 D12 values of phenol were almost constant ranging from (5.9·10−5 to 3.2·10−1) μmol injected in sc CO2, and decreased in higher injected amounts at 313.15 K and 17.87 MPa in the CIR method. Thus, D12 values reported in this study can be considered as those at infinitesimal concentrations. 3.2. Reproducibility of Measurements. To examine the reproducibilities of D12 and k determined, six measurements were made at the same conditions, 313.15 K and 35.00 MPa, as listed in Table 2. The expanded uncertainties of D12 and k with a level of confidence 0.95 (the coverage factor, kp = 2.5717 for 5 degrees of freedom, i.e., 6-fold measurements) were 1.05 % and 0.49 %, respectively. The measurements of D12 and k were quite reproducible. 3.3. Effect of Wavelength. Figure 2 illustrates the effects of the wavelength from (200 to 350) nm on (a) absorbance at

⎫

) ⎪⎬ ⎪ ⎭

(1)

where a is the effective diffusivity: a=

(2)

2 2 D12 1 + 6k + 11k 2 u0 R + 3 1+k 48D12 (1 + k)

and t is the time, m is the injected amount of solute, R is the radius of the column, k is the retention factor, defined as the ratio of a solute amount in the polymer phase to that in the fluid phase, L is the distance between the injection and detection point, and u0 is the average velocity of the fluid flowing in 2920

dx.doi.org/10.1021/je400313n | J. Chem. Eng. Data 2013, 58, 2919−2924

Journal of Chemical & Engineering Data

Article

Table 2. Reproducibilities of D12 and k at 313.15 K and 35.00 MPa, together with DeSc1/2 and εa T/K

P/MPa

D12/10−8 m2·s−1

k

DeSc1/2

ε/%

313.15

35.00 35.00 35.00 35.00 35.00 35.00

0.560 0.570 0.571 0.557 0.561 0.563 0.564

0.2100 0.2100 0.2095 0.2088 0.2093 0.2074 0.2092

5.56 5.47 5.56 5.47 5.44 5.41

0.80 0.17 0.36 0.76 0.68 0.93

average

It can be observed that the determined k values are independent of wavelength and slightly varied, while the D12 values are almost constant. The response curves measured at a wavelength of 240 nm were employed to determine D12 and k values in the present study. 3.4. Effect of Flow Rate. Figure 3 indicates the effect of CO2 velocities u0 on the (a) D12 and (b) k values at 313.15 K

a

The relative expanded uncertainties with level of confidence 0.95 (the coverage factor kP = 2.571 for five degrees of freedom, i.e., 6-fold measurements) are 1.05 % for D12 and 0.49 % for k.

Figure 3. The effect of CO2 velocity u0 on (a) the D12 values and (b) the k values for Pt(acac)2 in sc CO2 at 313.15 K and 11.00 MPa.

and 11.00 MPa in sc CO2, obtained at a wavelength of 240 nm. The diffusion coefficients reached the plateau value at the flow rates lower than 0.01 m·s−1, correspondingly DeSc1/2 = 7.32, where De is the Dean number, defined as = (2Ru0ρ/η)(R/Rcoil)1/2, and Rcoil is the coil radius of diffusion column. Note that the effect is less than 1 % when DeSc1/2 < 8,18 and the highest DeSc1/2 value for the data listed in Table 3 is 16.67 at 323.15 K and 10.50 MPa. According to the correction19 the effect on D12 value is ca. 7 %. On the contrary, k should not vary with the fluid velocity if the solute component instantly reaches equilibrium between the stationary phase and mobile phase. As expected and seen in Figure 3, the k values did not depend on u0, and the mean k value of 1.231 with a standard deviation of 0.015 was obtained over a wide fluid velocity. 3.5. Diffusion Coefficient and Retention Factor. The D12 and k values in sc CO2 measured by the CIR method and the D12 values in liquid ethanol by the Taylor dispersion method are listed in Tables 3 and 4, respectively, together with DeSc1/2 and fitting error ε. As seen for organic compounds and metal complexes reported in the literature, the D12 values increased with increasing temperature, and decreased with increasing pressure. The k values decreased with increasing temperature and pressure. In Figure 4 D12/T values for Pt(acac)2 in sc CO2 were plotted against CO2 viscosity at various temperatures, together with D12/T versus ethanol viscosity in liquid ethanol at atmospheric pressure using the Taylor dispersion method described in the present study. As seen for all compounds measured in our previous studies, D12/T is a function of solvent viscosity,

Figure 2. The effects of the wavelength on (a) absorbance at the maximum peak height, Amax, (b) D12, (c) k, and (d) ε for Pt(acac)2 in sc CO2 at 313.15 K and 11.00 MPa.

the maximum peak height of the response curve, Amax, (b) D12, (c) k, and (d) ε for Pt(acac)2 at each wavelength, 313.15 K, and 11.00 MPa in sc CO2 by the CIR method. All Amax values were lower than 0.05 AU over an entire range of wavelength, and the ε values were lower than 1 % which indicates a good fit.14,15 2921

dx.doi.org/10.1021/je400313n | J. Chem. Eng. Data 2013, 58, 2919−2924

Journal of Chemical & Engineering Data

Article

Table 3. D12 and k Values for Pt(acac)2 in CO2, together with DeSc1/2 and ε Measured by the CIR Methoda T/K

P/MPa

D12/10−8 m2·s−1

k

DeSc1/2

ε/%

308.15

8.51 9.00 10.00 11.00 12.00 15.00 20.00 25.00 30.00 35.00 40.00

0.998 0.923 0.869 0.814 0.783 0.701 0.643 0.596 0.555 0.526 0.507

2.344 1.599 1.060 0.824 0.709 0.494 0.347 0.267 0.235 0.202 0.188

7.12 7.70 7.38 6.40 7.40 7.65 6.91 6.03 6.71 6.07 6.41

0.74 0.88 0.82 0.64 0.76 0.96 0.64 1.00 0.75 0.55 0.93

9.00 9.50 9.71 10.00 10.50 11.00 12.00 12.50 14.00 15.05 16.00 17.50 19.52 20.00 25.00 29.14 30.00 35.00 40.00

1.296 1.126 1.096 1.034 0.991 0.935 0.883 0.860 0.832 0.804 0.768 0.767 0.717 0.703 0.650 0.591 0.600 0.564 0.538

7.398 2.956 2.419 1.973 1.461 1.231 0.953 0.845 0.669 0.573 0.527 0.458 0.379 0.380 0.295 0.233 0.240 0.209 0.185

16.11 11.75 6.26 9.25 7.08 6.28 5.92 5.64 7.66 5.55 6.98 6.76 5.50 6.35 7.18 5.78 6.75 5.41 5.03

0.52 0.30 0.90 0.78 0.57 0.71 0.78 0.99 0.93 0.54 0.87 0.25 0.12 0.50 0.75 0.81 0.48 0.62 0.55

10.50 11.00

1.559 1.366

10.092 5.180

16.67 8.03

0.92 1.02

313.15

323.15

P/MPa

D12/10−8 m2·s−1

k

DeSc1/2

ε/%

12.00 13.00 15.00 18.00 20.00 25.00 30.00 35.00 38.00

1.242 1.124 0.999 0.930 0.866 0.786 0.726 0.698 0.683

2.343 1.553 0.865 0.557 0.459 0.329 0.263 0.231 0.212

7.86 7.42 6.11 5.85 5.48 5.90 6.40 6.01 5.81

0.81 0.42 0.46 0.81 0.22 0.51 0.28 0.19 0.23

333.15

13.00 14.00 15.00 16.00 17.00 18.00 20.00 22.00 24.00 25.00 26.00 28.00 30.00 35.00 38.00

1.417 1.301 1.222 1.183 1.111 1.069 1.004 0.953 0.916 0.893 0.864 0.833 0.814 0.781 0.750

4.073 2.301 1.522 1.124 0.896 0.737 0.563 0.449 0.372 0.344 0.333 0.300 0.272 0.226 0.214

8.31 8.39 9.16 6.90 7.18 5.92 7.91 6.33 7.00 7.03 7.28 7.18 7.17 6.86 6.52

0.90 0.79 0.55 0.95 0.49 0.93 0.50 0.63 0.29 0.32 0.40 0.61 0.49 0.29 0.39

343.15

16.00 18.00 20.00 25.00 30.00 35.00

1.417 1.264 1.182 1.056 0.939 0.883

2.053 1.144 0.778 0.425 0.293 0.235

6.74 8.18 7.49 6.88 6.84 7.29

0.40 0.52 0.70 0.37 0.40 0.44

T/K

a

u(T) = 0.1 K, u(P) = 10 kPa. The relative expanded uncertainties with level of confidence 0.95 can be considered to be 1.05 % and 0.49 % for D12 and k, respectively, from the results in Table 2, although the D12 and k data listed in Table 3 were obtained in a single measurement.

Table 4. D12 Values for Pt(acac)2 in Ethanol, together with DeSc1/2 and ε Measured by the Taylor Dispersion Methoda T/K

P/MPa

D12/10−8 m2·s−1

DeSc1/2

ε/%

298.15 303.15 313.15 323.15 333.15

0.10 0.10 0.10 0.10 0.10

0.0735 0.0821 0.0979 0.124 0.142

6.36 4.17 8.44 4.69 8.28

0.80 0.59 0.67 0.45 0.51

a u(T) = 0.1 K, u(P) = 10 kPa. The relative expanded uncertainty with level of confidence 0.95 is 2.1 % for D12 with the coverage factor kp = 4.303 for 2 degree of freedom, i.e., 3-fold measurements.

and the plots were expressed by a straight line in logarithmic plots of D12/ T versus solvent viscosity,9−11,15,20 as follows: (D12 /m 2·s−1)/(T /K) = 9.520· 10−15(η/Pa· s)−0.8244

Figure 4. D12/T versus solvent viscosity for Pt(acac)2 in sc CO2 at various temperatures by the CIR method, and liquid ethanol by the Taylor dispersion method. In sc CO2: △, 308.15 K; ○, 313.15 K; □, 323.15 K; ▽, 333.15 K; ◊, 343.15 K. In ethanol: ◆, 298.15 K; ▲, 303.15 K; ●, 313.15 K; ■, 323.15 K; ▼, 333.15 K.

(3)

where D12 is the binary diffusion coefficient at infinitesimal concentration, η is the solvent viscosity, and the average absolute relative deviation AARD = 4.35 % for 67 data points (62 in sc CO2 and 5 in liquid ethanol) for the present D12 values measured in sc CO2 at temperatures from (308.15 to 343.15) K and pressures from (8.51 to 40.00) MPa and in

liquid ethanol at (298.15 to 333.15) K and atmospheric pressure. The slope of −0.8244 is not equal to −1, when the Stokes−Einstein equation holds, and is similar to those for other metal complexes and organic compounds in sc CO2. 2922

dx.doi.org/10.1021/je400313n | J. Chem. Eng. Data 2013, 58, 2919−2924

Journal of Chemical & Engineering Data

Article

The effect of density on k for Pt(acac)2 measured by the CIR method with curve fitting in sc CO2 at temperatures from (308.15 to 343.15) K and pressures from (8.51 to 40.00) MPa is shown in Figure 5. The k values determined are also listed in

Figure 6. Comparison of the present D12 data of Pt(acac)2 with those of Co(acac)3 in sc CO2 in our previous study.11 ○, Pt(acac)2 at 313.15 K in the present study; □, Co(acac)3 at 313.15 K in our previous study;11 ●, Pt(acac)2 and ■, Co(acac)3 at 313.15 K and 11.00 MPa in sc CO2 in the present study, when a mixture of Pt(acac)2 and Co(acac)3 ethanol solution was injected.

Figure 5. The effect of CO2 density ρ on k for Pt(acac)2 in sc CO2 at (308.15, 313.15, 323.15, 333.15 and 343.15) K. △, 308.15 K; ○, 313.15 K; □, 323.15 K; ▽, 333.15 K; ◊, 343.15 K.

Co(acac)3 (solid square). Both compounds have almost the same slopes, and the intercept for Pt(acac)2 is higher than that for Co(acac)3 while the molecular weight of Pt(acac)2 is higher than that of Co(acac)3. Since the molecular size for metal complex is not related to its molecular weight, differently from organic compounds as has been seen,15,23 the actual molecular size in sc CO2 should be known.

Table 3. The k values simply decrease with increasing CO2 densities and temperatures, and were well correlated with temperature and CO2 density in eq 4 with AARD = 2.6 % for 62 data points, as follows: ln k = c1 + c 2(T /K) + c3 ln(ρ/kg· m−3) + c4[ln(ρ/kg· m−3)]2

4. CONCLUSIONS The chromatographic impulse response method with curve fitting was utilized to measure binary diffusion coefficients and retention factors of platinum(II) acetylacetonate at temperatures from (308.15 to 343.15) K and pressures from (8.51 to 40.00) MPa and infinitesimal concentration in sc CO2. The Taylor dispersion method was also employed to measure the binary diffusion coefficients at infinitesimal concentration in liquid ethanol at temperatures from (298.15 to 333.15) K and atmospheric pressure. The values of D12/T were correlated in sc CO2 and liquid ethanol with a function of solvent viscosity with AARD = 4.35 % for 67 data points. Differently from organic compounds, D12 values of metal complexes were not related to molecular weight of the compounds. The k values in sc CO2 were also expressed with a function of temperature and CO2 density with AARD = 2.6 % for 62 data points.

(4)

where k is dimensionless, T is in K, ρ is in kg·m−3, c1, c2, c3 and c4 are constant. The parameters, c1, c2, c3, and c4 determined are shown in Table 5. Note that the k value is not a physical Table 5. The Constants c1 to c4 in Equation 4 c1

c2

c3

c4

T/K

N

AARD/%

31.780

−0.0211

−2.151

−0.257

308.15 313.15 323.15 333.15 343.15 Total

11 19 11 15 6 62

2.2 1.9 3.7 2.9 2.1 2.6

■

property but a characteristic parameter to influence the retention time of the peak. The k values can be related by the partial molar volume15,21 and the solubility22 of the solute. Figure 6 compares D12 values of Pt(acac)2 in the present study and Co(acac)3 in our previous study11 at 313.15 K in sc CO2, together with those of Pt(acac)2 and Co(acac)3 when a mixture of Pt(acac)2 and Co(acac)3 ethanol solution was injected at 313.15 K and 11.00 MPa in sc CO2 in the present study. Molecular weights of Pt(acac)2 and Co(acac)3 are (393.29 and 356.26) g·mol−1, respectively. To confirm the D12 values of Pt(acac)2 and Co(acac)3, 1.00 μL of a mixture of Pt(acac)2 (5.00 g·L−1) and Co(acac)3 (4.00 g·L−1) ethanol solution was injected in sc CO2 in the CIR method. Since the response curves for ethanol, Pt(acac)2, and Co(acac)3 were well separated chromatographically, the D12 data of both metal complexes were measured simultaneously. Clearly, each D12 datum of Pt(acac)2 and Co(acac)3 was consistent with those of each compound measured separately, and the D12 datum of Pt(acac)2 (designated in solid circle) was higher than that of

AUTHOR INFORMATION

Corresponding Author

*Tel.: +81-3-3817-1914. Fax: +81-3-3817-1895. E-mail: [email protected]. Funding

The authors are grateful to the Ministry of Education, Sports, Culture, Science and Technology of Japan for the financial support through Grant-in-Aid No. 22360325. Notes

The authors declare no competing financial interest.

■

REFERENCES

(1) Shah, P. S.; Husain, S.; Johnston, K. P.; Korgel, B. A. Nanocrystal arrested precipitation in supercritical carbon dioxide. J. Phys. Chem. B 2001, 105, 9433−9440. (2) Cabañas, A.; Long, D. P.; Watkins, J. J. Deposition of gold films and nanostructures from supercritical carbon dioxide. Chem. Mater. 2004, 16, 2028−2033.

2923

dx.doi.org/10.1021/je400313n | J. Chem. Eng. Data 2013, 58, 2919−2924

Journal of Chemical & Engineering Data

Article

supercritical fluid chromatography. J. Chromatogr. A 2012, 1250, 141− 156. (22) Kong, C. Y.; Sone, K.; Sako, T.; Funazukuri, T.; Kagei, S. Solubility determination of organometallic complexes in supercritical carbon dioxide by chromatographic impulse response method. Fluid Phase Equilib. 2011, 302, 347−353. (23) Funazukuri, T.; Kong, C. Y.; Kagei, S. Effects of molecular weight and degree of unsaturation on binary diffusion coefficients for lipids in supercritical carbon dioxide. Fluid Phase Equilib. 2004, 219, 67−73.

(3) Yoda, S.; Hasegawa, A.; Suda, H.; Uchimaru, Y.; Haraya, K.; Tsuji, T.; Otake, K. Preparation of a platinum and palladium/ polyimide nanocomposite film as a precursor of metal-doped carbon molecular sieve membrane via supercritical impregnation. Chem. Mater. 2004, 16, 2363−2368. (4) Lin, Y.; Cui, X.; Yen, C. H.; Wai, C. M. PtRu/carbon nanotube nanocomposite synthesized in supercritical fluid: A novel electrocatalyst for direct methanol fuel cells. Langmuir 2005, 21, 11474− 11479. (5) Lin, Y.; Cui, X.; Yen, C.; Wai, C. M. Platinum/carbon nanotube nanocomposite synthesized in supercritical fluid as electrocatalysts for low-temperature fuel cells. J. Phys. Chem. B 2005, 109, 14410−14415. (6) Yen, C. H.; Shimizu, K.; Lin, Y-Y; Bailey, F.; Cheng, I. F.; Wai, C. M. Chemical fluid deposition of Pt-based bimetallic nanoparticles on multiwalled carbon nanotubes for direct methanol fuel cell application. Energy Fuels 2007, 21, 2268−2271. (7) Puniredd, S. R.; Weiyi, S.; Srinivasan, M. P. Pd−Pt and Fe−Ni nanoparticles formed by covalent molecular assembly in supercritical carbon dioxide. J. Colloid Interface Sci. 2008, 320, 333−340. (8) Cangül, B.; Zhang, L. C.; Aindow, M.; Erkey, C. Preparation of carbon black supported Pd, Pt, and Pd−Pt nanoparticles using supercritical CO2 deposition. J. Supercrit. Fluids 2009, 50, 82−90. (9) Kong, C. Y.; Nakamura, M.; Sone, K.; Funazukuri, T.; Kagei, S. Measurements of binary diffusion coefficients for ferrocene and 1,1′dimethylferrocene in supercritical carbon dioxide. J. Chem. Eng. Data 2010, 55, 3095−3100. (10) Toriumi, M.; Katooka, R.; Yui, K.; Funazukuri, T.; Kong, C. Y.; Kagei, S. Measurements of binary diffusion coefficients for metal complexes in organic solvents by the Taylor dispersion method. Fluid Phase Equilib. 2010, 297, 62−66. (11) Kong, C. Y.; Gu, Y. Y.; Nakamura, M.; Funazukuri, T.; Kagei, S. Diffusion coefficients of metal acetylacetonates in supercritical carbon dioxide. Fluid Phase Equilib. 2010, 297, 162−167. (12) Kong, C. Y.; Funazukuri, T.; Kagei, S. Reliability of binary diffusion coefficients determined from tailing response curves measured by the Taylor dispersion method in the near critical region. J. Supercrit. Fluids 2008, 44, 294−300. (13) Funazukuri, T.; Kong, C. Y.; Murooka, N.; Kagei, S. Measurements of binary diffusion coefficients and partition ratios for acetone, phenol, α-tocopherol, and β-carotene in supercritical carbon dioxide with a poly(ethylene glycol)-coated capillary column. Ind. Eng. Chem. Res. 2000, 39, 4462−4469. (14) Kong, C. Y.; Funazukuri, T.; Kagei, S. Chromatographic impulse response technique with curve fitting to measure binary diffusion coefficients and retention factors using polymer-coated capillary columns. J. Chromatogr. A 2004, 1035, 177−193. (15) Funazukuri, T.; Kong, C. Y.; Kagei, S. Impulse response techniques to measure binary diffusion coefficients under supercritical conditions. J. Chromatogr. A 2004, 1037, 411−429. (16) Funazukuri, T.; Kong, C. Y.; Kagei, S. Measurement of binary diffusion coefficient from impulse response curve having extremely low absorbance intensity under supercritical condition by noise elimination technique. Fluid Phase Equilib. 2004, 220, 181−188. (17) Taylor, B. N.; Kuyatt, C. E. Guidelines for evaluating and expressing the uncertainty of NIST measurement results; NIST Technical Note 1297; U.S. Government Printing Office: Washington DC, September 1994. (18) Alizadeh, A.; Nieto de Castro, C. A.; Wakeham, W. A. The theory of the Taylor dispersion technique for liquid diffusivity measurements. Int. J. Thermophys. 1980, 1, 243−284. (19) Funazukuri, T.; Kong, C. Y.; Kagei, S. Correction of the secondary flow effect for binary diffusion coefficients using coated/ uncoated diffusion columns. Chem. Eng. Sci. 2004, 59, 3029−3036. (20) Funazukuri, T.; Kong, C. Y.; Kagei, S. Predictive correlation of binary diffusion and self-diffusion coefficients under supercritical and liquid conditions. J. Supercrit. Fluids 2008, 46, 280−284. (21) Kong, C. Y.; Funazukuri, T.; Kagei, S.; Wang, G.; Lu, F.; Sako, T. Applications of the chromatographic impulse response method in 2924

dx.doi.org/10.1021/je400313n | J. Chem. Eng. Data 2013, 58, 2919−2924