Solubility Measurement and Correlation of Carbon Monoxide (CO) in

Article pubs.acs.org/jced

Solubility Measurement and Correlation of Carbon Monoxide (CO) in Butyraldehydes: n‑Butyraldehyde and iso-Butyraldehyde A. Young Jeong, Hang-Kyu Cho, and Jong Sung Lim* Department of Chemical and Biomolecular Engineering, Sogang University, C.P.O. Box 1142, Seoul 100-611, South Korea ABSTRACT: The solubility of carbon monoxide (CO) in two isomeric butyraldehydes, n-butyraldehyde and iso-butyraldehyde, which are the products of a hydroformylation reaction in which CO is used as a reactant, was measured by using a variable-volume view cell equilibrium apparatus. The CO solubility was determined by measuring the bubble or cloud point pressures of various CO mole fractions at 10 K intervals from 303.15 to 373.15 K. We found that the solubilities of CO increased with increasing pressures and temperatures and that CO was more soluble in the iso-form (iso-butyraldehyde) than in the n-form (n-butyraldehyde). The measured data was calculated with the PR-EoS incorporated with the conventional van der Waals one-fluid mixing rule. Our measured data showed relatively good agreement with the calculated results with an AAD-p (%) of 2.38% for CO + n-butyraldehyde and 1.57% for the CO + iso-butyraldehyde system. antioxidants, flavors, tanning agents, and perfumes.9,11,12 isoButyraldehyde is an isomer of n-butyraldehyde obtained as a side-product from the hydroformylation process of propylene. For producing 2,2-dimethyl-1,3-propanediol (neopentylglycol), which is eco-friendly and is used in the synthesis of polyesters, paints, lubricants, and plasticizers,9,13 it can be reacted with formaldehyde. As a reactant, CO is one of the core components in the hydroformylation of propylene in which it reacts with propylene to form n-butyraldehyde and iso-butyraldehyde. In this process, the solubility of CO in the products, reactants, and solvents is an important parameter required for understanding the reaction kinetics and the issues related to process control since the solubility highly influences both the reaction rate and product composition. Nonetheless, almost all the studies on the solubility of CO have been conducted only on reactants or solvents.14 As we know on, the solubility data of CO in nbutyraldehyde have not yet been published in the open literature. For iso-butyraldehyde, Polyakov et al.15 had reported the CO solubility data at the temperature range from 293.15 to 393.15 K in 1989, but their data were limited in pressure up to 25.3 MPa and CO mole fraction of 0.282. In this work, solubility of CO in n-butyraldehyde and isobutyraldehyde, which are the isomeric products of hydroformylation of propylene, is studied. By measuring the bubble or cloud point pressure, we obtained the CO solubility data for various CO mole fractions at five equally spaced temperatures between 303.15 and 373.15 K. Furthermore, we correlated the experimental data with the PR-EoS, and the relevant binary parameters were suggested.

1. INTRODUCTION Because of oil depletion, the interest in converting various C1 chemicals (e.g., carbon monoxide, carbon dioxide, methane, syngas, and methanol) to produce valuable chemicals is increasing.1,2 This conversion process is referred to as C1 chemistry. C1 chemistry is expected to become a major field of interest for developing transportation fuels and chemical products in the coming future.3 Hydroformylation, also known as oxo synthesis, is a type of C1 chemistry. It involves carbon monoxide (CO) insertion.4 It is an important and widely studied industrial process for the production of aldehydes from alkenes.5,6 Nowadays, about more than 10 million ton industrial products are produced by hydroformylation per year.7 The oxo aldehydes are used as starting substances for synthesizing solvents, adhesives, plasticizers, pharmaceuticals, and agrochemicals.8,9 In the hydroformylation process, hydroformylation of propylene, which involves the insertion of CO to propylene, is used to produce about 75% of the world’s oxo chemicals.5,10,11 From the viewpoint of worldwide annual production, the most important hydroformylation process is the hydroformylation of propylene. Hydroformylation of propylene yields n-butyraldehyde and iso-butyraldehyde. Butyraldehyde or n-butyraldehyde is used to manufacture 2-ethylhexanol (2-EH) and n-butanol. 2-Ethylhexanol is a valuable intermediate for the chemical industry. It finds application in various plasticizers and is also used in the synthesis of specialty chemicals. Some industrial products that require n-butyraldehyde are bis(2-ethylhexyl) phthalate (DEHP), methyl amyl ketone, polyvinyl butyral (PVB), trimethylolpropane (TMP) and n-butyric acid. Butyraldehyde is also used in smaller applications such as the synthesis of intermediates for producing synthetic resins, medicines, insecticides, crop protectants, vulcanization accelerators, © 2017 American Chemical Society

Received: August 29, 2016 Accepted: January 16, 2017 Published: January 24, 2017 704

DOI: 10.1021/acs.jced.6b00765 J. Chem. Eng. Data 2017, 62, 704−711

Journal of Chemical & Engineering Data

Article

2. EXPERIMENTS 2.1. Materials. The n-butyraldehyde and iso-butyraldehyde were purchased from Sigma-Aldrich (U.S.A.). The high-purity carbon monoxide was attained from Dong-A Gas Co. in Korea. The purities of n-butyraldehyde, iso-butyraldehyde, and CO were 0.99, 0.995, and 0.9999 in mass fraction, respectively. The purity data were provided by the suppliers. We analyzed these three pure components with a gas chromatography (GC). The analyzed purities of n-butyraldehyde, iso-butyraldehyde, and CO were greater than 0.99, 0.995, and 0.9999 in mass fraction, respectively. Therefore, all substances were used without further purification (Table 1).

window and a movable piston inside, a hand pump, a magnetic stirring system, a borescope with a CCD camera, and an air bath. The system pressure was controlled by pressurizing or depressurizing the water behind the piston using a hand pump (HIP equipment Co., 50-6-15). Pressure was measured by a high-precision pressure gauge (Dresser Heise, CC-12-G-A02B) with accuracy of ±0.05 MPa and resolution of ±0.01 MPa. To measure the interior temperature of the cell within ±0.1 K, resistance temperature detector (RTD) temperature sensor was used. The phase behavior occurring interior of the cell could be observed by monitoring the video monitor connected to the CCD camera and bore scope (Olympus, R080-044-000-50) . 2.3. Experimental Procedure. First, the equilibrium cell was evacuated to remove any gases captured inside the cell. An aldehyde sample (n-butyraldehyde or iso-butyraldehyde) was then introduced into the cell. The accurate mass of the aldehyde sample was measured within ±1 mg using a precision balance (Precias, 1212 M). Then, a targeted mass of CO gas was introduced into the cell. The accurate mass of the CO gas loaded into the equilibrium cell could be obtained from the difference of weights between the CO sample cylinder before and after loading. To minimize any CO gas loss in the feed line, we made it as short as possible (about 5 cm), and after closing the CO cylinder valve the CO gas trapped in the line between the cell and CO cylinder valve was sent to the view cell by heating the feed line with a heat gun. According to the ISO guideline,25 we performed the uncertainty analysis for the composition measurement of each component. For a mixture with n1 moles of CO (1) and n2 moles of butyraldehyde (2), because n = n1 + n2 and x1 = n1/n, u(x1) (the uncertainty in x1) is represented as

Table 1. Sample Table initial mole fraction purity

purification method

final mole fraction purity

analysis method

chemical name

source

nbutyraldehyde isobutyraldehyde carbon monoxide

Aldrich

0.99

none

0.99

GCa

Aldrich

0.995

none

0.995

GCa

Dong-A Gas Co

0.9999

none

0.9999

GCa

a

Gas chromatography.

2.2. Experimental Apparatus. The experimental equipment for measuring the CO solubility was identical to that used in our former work16−22 and similar to the apparatus used in studies conducted by other groups.23,24 Figure 1 shows a

u(x1) = x1

u 2(n1) n12

+

u 2(n) n2

(1)

where u(n) and u(n1) are the uncertainties in measuring n and n1, respectively. In eq 1, u(n) is represented as u(n) =

u 2(n1) + u 2(n2)

(2)

where u(ni) = u(mi)/MWi, and mi and MWi are the mass and molecular weight of component i, respectively. u(mi) (the uncertainty in mi) can be obtained from u(mi) =

uA2 (mi) + uB2(mi)

(3)

where uA(mi) is the uncertainty from the repeatability in measuring mi and uB(mi) is the uncertainty from the accuracy of the balance used to measure mi. In our experiments, we employed uA(m1) = uB(m1) = 2 × 10−3 g for CO and uA(m2) = uB(m2) = 2 × 10−4 g for butyraldehyde. The resulted uncertainties of the composition measurement were presented in Tables 2 and 3. The CO−aldehyde mixture in the cell was magnetically stirred to facilitate the dissolution of the CO gas in the aldehyde. At the same time, using the hand pump the CO gas + aldehyde mixture in the cell was slowly compressed by compressing the water behind the piston and moving it toward the sapphire window; thus, the pressure in the cell was continuously increased. As the pressure increased, the CO gas dissolved into the aldehyde phase until the solution became a single, homogeneous, phase. Then, the pressure was slowly reduced at a rate of approximately 0.01 MPa/sec by

Figure 1. A schematic diagram of the experimental apparatus: (1) water for pressing; (2) hand pump; (3) pressure gauge; (4) piston; (5) sapphire window; (6) magnetic bar; (7) stirrer; (8) air bath; (9) variable-volume view cell; (10) light source; (11) borescope; (12) CCD camera; (13) monitor; (14) temperature gauge; (15) heater; and (16) heating controller.

schematic diagram of our experimental apparatus. It is described in detail in our previous publications16−22 and is described briefly here in. The bubble or cloud points of the CO + aldehyde mixtures were measured using a high pressure equilibrium view cell with maximum operating ranges of 150 MPa and 423.15 K. The apparatus was composed mainly of a high-pressure variable volume view cell containing a sapphire 705



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Table 2. Solubility Data for the CO (1) + n-Butyraldehyde (2) Systema mole fraction of CO, x1

standard uncertainty in CO mole fraction

0.035

0.007

0.086

0.0036

0.125

0.0028

0.165

0.0019

a

T/K

p/MPa

phase behavior

mole fraction of CO, x1


303.15 313.15 323.15 333.15 343.15 353.15 363.15 373.15 303.15 313.15 323.15 333.15 343.15 353.15 363.15 373.15 303.15 313.15 323.15 333.15 343.15 353.15 363.15 373.15 303.15 313.15 323.15 333.15 343.15 353.15 363.15 373.15

3.85 3.67 3.48 3.16 3.25 3.17 3.07 2.92 9.1 8.85 8.7 8.6 8.18 7.74 7.23 6.86 14.69 14.03 13.36 13.07 12.72 12.65 12.28 11.85 21.00 20.17 19.46 18.61 17.90 17.12 16.26 15.48

bb b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b b

0.267

0.0018

0.373

0.0007

0.412

0.0005

0.513

0.0003

T/K

p/MPa

Phase behavior

303.15 313.15 323.15 333.15 343.15 353.15 363.15 373.15 303.15 313.15 323.15 333.15 343.15 353.15 363.15 373.15 303.15 313.15 323.15 333.15 343.15 353.15 363.15 373.15 303.15 313.15 323.15 333.15 343.15 353.15 363.15 373.15

40.23 37.28 34.91 32.93 31.32 29.64 27.98 26.37 59.99 55.03 52.38 47.92 44.29 42.54 40.06 38.00 73.19 66.82 61.44 56.83 53.00 49.49 46.42 43.68 96.84 87.22 79.34 72.83 66.79 61.83 57.25 54.23

b b b b b b b b b b b b b b b b cc c c c c c c c c c c c c c c c

Standard uncertainties u are u(T) = 0.1 K, ur(p) = 0.01 (1% of the measured value). bBubble point. cCloud point.

withdrawing the piston until the first gas bubble formed in the homogeneous liquid-phase solution. The bubble point pressure was defined as the pressure at which the first gas bubble came up from the liquid phase solution. To ensure consistency and reproducibility, we repeated each measurement at least three times. For the solutions with relatively large CO mole fractions, however, the cloud point behavior was observed instead of the bubble point behavior. We defined the cloud point pressure as the pressure at which the visual observation of the stirring bar in the cell is no longer possible. At the cloud point, the phase transition of the solution from a homogeneous phase to two liquid phases occurred and the solution became cloudy. Because the rate of pressure reduction was low, no effects of the pressure reduction on the measurement of the bubble or cloud point pressures were detected. For the temperature measurement, the combined uncertainty was 0.1 K and the relative standard uncertainty of the pressure measurement (ur(p)) was 0.01, that is 1% of the measured value. After one set of experiments at a certain mole fraction of CO were completed, a new experimental system was prepared by charging the cell with a suitable amount of CO. Then, the mole fraction of CO in this new experimental system was calculated and consecutive measurements performed according to the procedure described above.

3. MODELING Our measured CO solubility data were correlated with the Peng−Robinson equation of state (PR-EoS), which is one of the most popular among the numerous equations of state for practical application. The PR-EoS26 can be written as follows P=

a(T ) RT − V−b V (V − b) + b(V − b)

(4)

The binary parameters are calculated from the following quadratic mixing rules a=

∑ ∑ xixjaij i

j

aij = (aiiajj)1/2 (1 − kij)

b=

(5) (6)

∑ ∑ xixjbij i

j

⎛ bi + bj ⎞ bij = ⎜ ⎟(1 − lij) ⎝ 2 ⎠

(7)

(8)

In eq 7, bii = bi and bjj = bj and in eq 6 and 8, kij and lij are the binary interaction parameters 706



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Table 3. Solubility Data for the CO (1) + iso-Butyraldehyde (2) Systema mole fraction of CO, x1


0.070

0.0083

0.157

0.0029

0.256

0.0015

a

T/K

p/MPa

phase behavior

mole fraction of CO, x1


303.15 313.15 323.15 333.15 343.15 353.15 363.15 373.15 303.15 313.15 323.15 333.15 343.15 353.15 363.15 373.15 303.15 313.15 323.15 333.15 343.15 353.15 363.15 373.15

7.18 7.04 6.96 6.80 6.61 6.41 6.20 5.99 16.84 16.62 16.14 15.68 14.96 14.29 13.45 12.68 30.28 28.44 27.90 26.57 25.28 24.08 22.84 21.82

bb b b b b b b b b b b b b b b b b b b b b b b b

0.375

0.0011

0.452

0.0007

0.512

0.0003

T/K

p/MPa

phase behavior

303.15 313.15 323.15 333.15 343.15 353.15 363.15 373.15 303.15 313.15 323.15 333.15 343.15 353.15 363.15 373.15 303.15 313.15 323.15 333.15 343.15 353.15 363.15 373.15

48.48 45.00 43.00 41.48 38.95 36.00 34.22 32.41 61.66 57.36 53.04 49.47 46.75 44.03 41.48 39.17 68.64 63.01 58.25 54.37 50.98 47.14 43.79 40.83

b b b b b b b b cc c c c c c c c c c c c c c c c

Standard uncertainties u are u(T) = 0.1 K, ur(p) = 0.01 (1% of the measured value). bBubble point. cCloud point.

aii =

0.457235R2Tc2i Pci

N

F=

⎡ ⎛ ⎢1 + (0.37464 + 1.54226ωi − 0.26992ωi2)⎜⎜1 − ⎢⎣ ⎝

⎤ T ⎞⎥ ⎟⎟ Tci ⎠⎥⎦

i=1

2

0.077796RTci Pci

Table 4. Critical Properties and Acentric Factor of CO from Literature and Aldehydes from Literature27 Tc/K

Pc/MPa

ω

CO n-butyraldehyde iso-butyraldehyde

28.01 72.11 72.11

134.452 522.28 543.61

3.755 4.411 5.119

0.0398 0.409 0.170

(11)

pcalc i

4. RESULTS AND DISCUSSION In this study, the solubilities of CO in n-butyraldehyde and isobutyraldehyde were measured at 10 K intervals from 303.15 to 373.15 K and at pressures of up to 90 MPa. To obtain the solubility data, we measured the bubble (or cloud) point pressures of the CO + n-butyraldehyde and CO + isobutyraldehyde mixtures with different compositions at a fixed mole fraction of CO and temperature. The experimental data are illustrated in Tables 2 and 3 for the CO + n-butyraldehyde system and the CO + iso-butyraldehyde systems, respectively. Figure 2 shows the p−T isopleths of the CO−aldehyde systems. The solubility data are given in terms of the CO mole fraction (x1) in the CO (1) + aldehyde (2) mixtures. As shown in Tables 2 and 3 and Figure 2, the bubble (or cloud) point pressure decreased with increasing system temperature at a fixed mole fraction of CO, indicating that the CO solubility in aldehydes increases with temperature. Tables 2 and 3 also illustrate the behaviors of the phase transition (the bubble or cloud point) observed during the measurements. In the equilibrium cell, CO gas was gradually dissolved into the aldehyde phase as the pressure increased with a single homogeneous phase eventually being formed. When the homogeneous solution had formed in the cell, the system was slowly depressurized until phase separation occurred. As shown in Tables 2 and 3, when the mole fraction of CO was

For calculating the PR-EoS parameters, critical temperature (Tc), critical pressure (Pc), and the acentric factors (ω) of both components (i.e., CO and the butyraldehydes) were necessary. These properties are cited from the reliable scientific literature27 and shown in Table 4. Prior to the equilibrium

M/g·mol−1

pexp i

where N is the number of data points, and is the experimental and calculated pressure, respectively. To solve a nonlinear least-squares problem, we used UNLSF optimization routine in IMSL/Math Library.

(10)

material

|picalc − piexp | pexp i

(9)

bi =

∑

calculations, k12 and l12, the adjustable binary interaction parameters, were determined first for each system. With the PR-EoS, the measured p−x1 data at a given temperature for a CO + butyraldehydes system were correlated, and then a set of k12 and l12 parameters were determined by optimizing the following objective function 707



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Figure 3. p−x1 diagram of the (CO + aldehyde) mixtures at different temperatures for two different aldehydes: (a) CO + n-butyraldehyde; (b) CO + iso-butyraldehyde. The symbols are temperature: (▽), 303.15 K; (▼), 313.15 K; (□), 323.15 K; (■), 333.15 K; (△), 343.15 K; (▲), 353.15 K; (○), 363.15 K; and (●), 373.15 K; (☆), 313.15 K15; (+), 333.15 K15; (x), 353.15 K15; (★), 373.15 K15; (―), calculated by the PR-EoS model.

Figure 2. p-T isopleths of the (CO + aldehyde) mixtures at different mole fractions of CO. (a) CO + n-butyraldehyde (symbols are CO mole fraction): (×), 0.035; (●), 0.086; (◊), 0.125; (⧫), 0.165; (○), 0.267; (▲), 0.373; (△), 0.412; (★), 0.513. (b) CO + isobutyraldehyde: (□), 0.070; (♀), 0.157; (■), 0.256; (♂), 0.375; (☆), 0.452; (▼), 0.512.

≤0.373 in the CO + n-butyraldehyde system and ≤0.375 in the CO + iso-butyraldehyde system, bubble point behavior was observed. Conversely, in solutions with higher CO mole fractions, cloud point behavior was observed. Specifically, in solutions where the CO mole fraction was greater than or equal to 0.412 in the CO + n-butyraldehyde system and 0.452 in the CO + iso-butyraldehyde system, cloud point behavior was observed. Figure 2 also represents the relationship between the solubility of CO and the pressure. The solubilities of CO in both butyraldehydes increased with pressure at a fixed temperature. These results are illustrated in Figure 3. In Figure 3a,b, the equilibrium pressures of CO + n-butyraldehyde and CO + iso-butyraldehyde systems, respectively, are plotted as a function of the CO mole fraction at different temperatures. From the shape of the graphs in Figure 3 and the occurrence of cloud point in solutions with higher CO mole fractions (Tables 2 and 3), we propose that the CO + aldehyde systems exhibit type V behavior according to the Scott and van Konynenburg classification system.28,29 Figure 4 shows a schematic diagram of a Scott and van Konynenburg type V phase at temperatures above the critical point of the more volatile component. As illustrated schematically in Figure 4a, our measured bubble and cloud points in (Tables 2 and 3 and Figure 3) are similar to the

filled-circles and the open-circles, respectively. As can be seen in Figure 4, in solutions with a low mole fraction of CO, vapor− liquid equilibrium is reached. However, at higher CO mole fractions liquid−liquid equilibrium is reached instead. This appears to be the reason why cloud point behavior occurred at higher CO mole fractions in the CO + aldehyde systems. However, more experimental data is needed before a definitive statement can be made regarding the phase behavior in these systems. Figure 3 also shows that the solubilities of CO in the butyraldehydes increased with temperature at a fixed pressure. These experimental results deviate from most gas−liquid systems in that the gas solubility usually decreases when the temperature increases. However, this phenomenon has also been observed in many other experiments investigating the solubility of CO in alkanes or aldehydes.30−33 According to a report by Raeissi et al.,34 this “inverse” temperature effect is related to the low molecular weight and weak intermolecular interactions of gases such as hydrogen, oxygen, and nitrogen. From a thermodynamic perspective, this unusual phase behavior is related to a large difference in critical temperature between the gas and the liquid. In our present study, carbon monoxide is light and has weak intermolecular interactions, 708



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Table 5. Binary Interaction Parameters (k12, l12) for the Butyraldehydes System n-butyraldehyde 303.15 313.15 323.15 333.15 343.15 353.15 363.15 373.15

K K K K K K K K

iso-butyraldehyde

k12

l12

k12

l12

0.0577 0.0593 0.0631 0.0673 0.0635 0.0688 0.7641 0.0916

0.0030 0.0052 0.0078 0.0118 0.0089 0.0107 0.0153 0.0231

0.0789 0.0121 0.0052 0.0021 −0.0008 −0.0050 −0.0058 −0.0044

−0.0004 −0.0013 −0.0040 −0.0035 −0.0005 0.0004 0.0047 0.0098

temperature

Table 6. Average Absolute Deviations of Pressure (AAD-p (%)) between Experimental Data and Calculated Values for the (CO + Butyraldehydes) Systema AAD-p (%) temperature

n-butyraldehyde

iso-butyraldehyde

303.15 K 313.15 K 323.15 K 333.15 K 343.15 K 353.15 K 363.15 K 373.15 K Average

2.90 2.6 1.91 2.22 1.95 2.13 2.69 2.66 2.38

1.39 1.62 1.10 1.02 1.26 1.76 2.04 2.41 1.57

a

Standard uncertainties u are u(T) = 0.1 K, ur(p) = 0.01 (1% of the measured value). bAverage absolute deviation in percentage:

Figure 4. Schematic diagrams for type V phase behavior. (a) isothermal p−x−y diagram at temperature above the critical point of the more volatile component. The filled-circles represent our measured bubble point and the open-circles represent cloud point. (b) Scott−van Konynenburg p−T projection.

AAD% =

1 N

N

∑ i=1

|picalc − piexp | piexp

× 100 (N = number of data)

solubility of CO in the butyraldehydes over a wide range of pressures. Figure 5 illustrates a comparison between the solubility of CO in n-butyraldehyde and iso-butyraldehyde at 323.15 K. At pressures below 20 MPa, differences between the solubilities of CO in n-butyraldehyde and iso-butyraldehyde are negligible.

such as oxygen and nitrogen. Additionally, the critical temperature of carbon monoxide is 134.45 K and those of nbutyraldehyde and iso-butyraldehyde are 522.28 and 543.61 K, respectively. These large differences in critical temperature and the lightness and weakly interacting nature of the CO result in this “inverse” behavior. A detailed explanation of this “inverse” temperature effect can be found elsewhere.34 Our measured solubility data of CO in iso-butyraldehyde were compared graphically with the literature data15 in Figure 3 (b). The literature data15 were reported in 1989 and they showed a similar tendency with our experimental data with the average absolute deviation of pressure (AAD-p (%)) of 7.19. The experimental data were correlated with the PR-EoS combined with the conventional van der Waals mixing rule. The PR-EoS is a widely used EoS for practical applications. For each system, the binary interaction parameters were calculated at 10 K intervals from 303.15 to 373.15 K, and are given in Table 5. The experimental data (symbols) and the calculated results (solid lines) are illustrated in Figure 3. In Table 6, the average absolute deviations of pressure (AAD-p (%)) between the experimental and calculated data are shown. The AAD-p (%) values ranged from 1.02 to 2.69% and the average values were 2.38% for the CO + n-butyraldehyde system and 1.57% for the CO + iso-butyraldehyde system. These values are relatively small and were considered to be acceptable. Therefore, we concluded that the PR-EoS with the van der Waals mixing rule can be used satisfactorily to calculate the

Figure 5. Comparison of CO solubility in iso-butyraldehyde and nbutyraldehyde at 323.15 K. The symbols are aldehydes: (○), isobutyraldehyde; (●), n-butyraldehyde; (―), trend line. 709



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(7) Fleischer, I.; Wu, L.; Profir, I.; Jackstell, R.; Franke, R.; Beller, M. Towards the development of a selective ruthenium-catalyzed hydroformylation of olefins. Chem. - Eur. J. 2013, 19, 10589−10594. (8) Bohnen, H.-W.; Cornils, B. Hydroformylation of alkenes: an industrial view of the status and importance. Adv. Catal. 2002, 47, 1− 64. (9) Franke, R.; Selent, D.; Börner, A. Applied hydroformylation. Chem. Rev. 2012, 112, 5675−5732. (10) Reinius, H. K.; Suomalainen, P.; Riihimäki, H.; Karvinen, E.; Pursiainen, J.; Krause, A. O. I. o-alkyl-substituted triphenyl phosphines: activity and regioselectivity in rhodium-catalysed propene hydroformylation. J. Catal. 2001, 199, 302−308. (11) Cents, A. H. G.; Brilman, D. W. F.; Versteeg, G. F. Mass-transfer effects in the biphasic hydroformylation of propylene. Ind. Eng. Chem. Res. 2004, 43, 7465−7475. (12) Ko, A. N.; Hu, C. H.; Yeh, Y. T. Highly selective Pd/KX catalysts for low-pressure one-step synthesis of 2-ethylhexanal from nbutyraldehyde and hydrogen. Catal. Lett. 1998, 54, 207−210. (13) Matlack, A. Introduction to Green Chemistry, 2nd ed.; CRC Press: New York, 2010. (14) Still, C.; Salmi, T.; Mäki-Arvela, P.; Eränen, K.; Murzin, Y. D.; Lehtonen, J. Solubility of gases in a hydroformylation solvent. Chem. Eng. Sci. 2006, 61, 3698−3704. (15) Polyakov, A. A.; Tyvina, T. N.; Fokina, V. V. Compositions and molar volumes of solutions of carbon monoxide, methane, and isobutylene in isobutyraldehyde. Zh. Prikl. Khim. 1989, 62, 2378− 2380. (16) Kim, J. E.; Kim, H. J.; Lim, J. S. Solubility of CO2 in ionic liquids containing cyanide anions: [c2mim][SCN], [c2mim][N(CN)2], [c2mim][C(CN)3]. Fluid Phase Equilib. 2014, 367, 151−158. (17) Kim, S. A.; Yim, J. H.; Lim, J. S. High-pressure phase behavior of binary mixtures containing methylpyrrolidinium derivative ionic liquids and carbon dioxide. Fluid Phase Equilib. 2012, 332, 28−34. (18) Kim, J. E.; Kang, J. W.; Lim, J. S. Measurement of CO2 solubility in cyanide anion based Ionic Liquids; [c4mim][SCN],[c4mim][N(CN)2], [c4mim][C(CN)3]. Korean J. Chem. Eng. 2015, 32, 1678− 1687. (19) Yim, J. H.; Lim, J. S. CO2 solubility measurement in 1-hexyl-3methyl- imidazolium ([HMIM]) cation based ionic liquids. Fluid Phase Equilib. 2013, 352, 67−74. (20) Yim, J. H.; Song, H. N.; Lee, B. C.; Lim, J. S. High-pressure phase behavior of binary mixtures containing ionic liquid [HMP][Tf2N], [OMP][Tf2N] and carbon dioxide. Fluid Phase Equilib. 2011, 308, 147−152. (21) Yim, J. H.; Song, H. N.; Yoo, K. P.; Lim, J. S. Measurement of CO2 solubility in ionic liquids: [BMP] [Tf2N] and [BMP][MeSO4] by measuring bubble-point pressure. J. Chem. Eng. Data 2011, 56, 1197− 1203. (22) Song, H. N.; Lee, B. C.; Lim, J. S. Measurement of CO2 solubility in ionic liquids: [BMP][TfO] and [P14,6,6,6][Tf2N] by measuring bubble point pressure. J. Chem. Eng. Data 2010, 55, 891− 896. (23) Yoon, S. D.; Byun, H. S. Experimental measurement and correlation of phase behavior for the CO2+heptafluorobutyl acrylate and CO2+heptafluorobutyl methacrylate systems at high pressure. Korean J. Chem. Eng. 2014, 31, 522−527. (24) Lee, B. C.; Nam, S. G. High-pressure solubility of carbon dioxide in pyrrolidinium-based ionic liquids: [bmpyr][dca] and [bmpyr][Tf2N]. Korean J. Chem. Eng. 2015, 32, 521−533. (25) BIPM, IEC, ISO IFCC, and IUPAP IUPAC. OIML. Guide to the expression of uncertainty in measurement; International Organisation for Standardisation: Geneva, Switzerland, 1995. (26) Prausnitz, J. M.; Lichtenthaler, R. N.; Azevedo, E. G. D. Molecular thermodynamics of fluid-phase equilibria, 3rd ed., PrenticeHall: Upper Saddle River, NJ, 1999. (27) McLinden, M. O.; Klein, S. A.; Lemmon, E. W.; Peskin, A. P. Thermodynamic properties of refrigerants and refrigerant mixtures database (REFPROP) V.6.01; NIST: Washington, DC, 1998.

However, at pressures greater than 20 MPa, the differences in CO solubility in these two systems become more apparent. CO was found to be more soluble in iso-butyraldehyde than in nbutyraldehyde. This finding appears to be closely related to the differences in the polarity of the butyraldehydes.35,36 In general, polar substances tend to dissolve easily in other polar substances. Iso-butyraldehyde is more polar than n-butyraldehyde. As CO is also a polar substance, it dissolves more easily in iso-butyraldehyde than in n-butyraldehyde. However, further studies are required to more fully determine the reasons for this solubility difference.

5. CONCLUSIONS The solubilities of CO in n-butyraldehyde and iso-butyraldehyde were measured using a variable-volume view cell equilibrium apparatus. Measurements were taken at 10 K intervals from 303.15 to 373.15 K. In the hydroformylation reaction of propylene, CO is used as a reactant and nbutyraldehyde and iso-butyraldehyde are isometric products. By measuring the bubble (or cloud) point pressures, the solubilities of CO in both aldehydes were determined. The measured data were correlated with the PR-EoS using the van der Waals mixing rules. The results calculated using the PR-EoS correlate well with the experimental data with an AAD-p (%) below 2.4%. The CO solubility in aldehydes was observed to increase with increasing temperature and pressure. Lastly, the results show that the CO solubility in aldehydes was greater in iso-butyraldehyde than in n-butyraldehyde.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel: +82 705 8918. Fax: +82 705 7899. ORCID

Jong Sung Lim: 0000-0002-1826-6216 Funding

This research was supported by C1 Gas Refinery Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (NRF-2016M3D3A1A01913262). Also, this research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2016R1D1A1B01013707). Notes

The authors declare no competing financial interest.

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REFERENCES

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Solubility Measurement and Correlation of Carbon Monoxide (CO) in

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