Densities and Speeds of Sound of Jatropha curcas Biodiesel + (C4

Jul 31, 2012 - Department of Chemistry, Maharshi Dayanand University, Rohtak-124001, India. ABSTRACT: Densities (ρmix) and speeds of sound (umix) for...
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Densities and Speeds of Sound of Jatropha curcas Biodiesel + (C4−C5) Alkan-1-ol Binary Mixtures Satish Kumar,*,† Vinod Kumar Sharma,‡ Wonsub Lim,† Jae Hyun Cho,† and Il Moon*,† †

Department of Chemical and Biomolecular Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 120-749, Republic of Korea ‡ Department of Chemistry, Maharshi Dayanand University, Rohtak-124001, India ABSTRACT: Densities (ρmix) and speeds of sound (umix) for binary blends of Jatropha curcas biodiesel (1) + n-butanol or n-pentanol (2) were measured at T = (288.15 to 308.15) K and atmospheric pressure, over the entire composition range, with the help of a density and sound velocity meter (DSA 5000 M, Anton Paar). The density values were used to evaluate the excess molar volumes VEmix. The Redlich−Kister polynomial equation was adopted to compute and correlate the results, and a good agreement has been observed between experimental and calculated values. It has been observed that the ρ and u values of pure components and their binary blends decreased with respect to temperature. Further, results have been analyzed in terms of molecular forces functioning between biodiesel and alcohols.

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INTRODUCTION Growing energy demand, surging oil prices, reducing oil reserves, and greenhouse gas emissions associated with the use of fossil fuels have sparked renewed interest to find out sustainable and renewable alternative fuels. Therefore, a significant amount of research works have been carried out regarding the search of alternative fuel sources throughout the world, with stress on biofuels that have the additional benefit of being renewable.1−4 Biofuels derived from agricultural feedstocks have the potential to decrease the world’s dependence on oil imports, support indigenous agronomic industries and improve farming profits, and moreover, have capability of reducing exhaust gas emissions. Among those vegetable oils, their transesterified (biodiesel) and fermented products (bioalcohols) have been anticipated as very proficient fuels. Biofuel production is a speedily developing industry in various parts of the globe.5 One of the major problems associated with the use of vegetable oils as diesel fuel is their high viscosity, approximately 10 to 20 times higher than standard diesel fuel.6 This problem can be resolved by converting (chemically modifying) vegetable oils to biodiesel, which have similar characteristics to diesel fuel. Biodiesel has considerably diverse properties than vegetable oils and have improved engine performance. Currently, biodiesel is the most commonly admitted alternative fuel because of its technical, ecological, and strategic benefits. It has improved biodegradability, low toxicity, and better lubricity in contrast to diesel fuels.6 Additionally, biodiesel is totally miscible with diesel fuel, allowing its blending with diesel fuel in any amount. However, biodiesel has some disadvantages such as high prices, higher viscosity, and poor cold flow properties. Mixing © 2012 American Chemical Society

of biodiesel with oxygenated compound like alcohols is one of the approaches to outweigh the disadvantages of vegetable oils and biodiesel in engine operations. Hence, it is essential to recognize the basic assets of blends. Further, knowledge of the fluid properties (density, viscosity, speed of sound, etc.) is significant for various engineering applications. These properties are significant with regard to the appliance design and process control. Out of these fluid properties, density plays a significant role. Density is a fuel property which affects the engine operation. Many fuel properties such as cetane number and gross heating value are interrelated with density.7 This property does also effects the efficacy of fuel.8,9 The correct prediction of biodiesel densities is a prime requirement for the right composition of an acceptable blend of biodiesel with other fuels, with the aim of synthesizing biodiesel as per required standards10,11 at nominal production costs. Moreover, physicochemical properties of biodiesel and its blends provide an important tool for understanding the nature of intermolecular forces existing between biodiesel constituents and development of numerous equipment industries, and such data are scarce in literature. J. curcas biodiesel is a complex mixture of organic compounds, separated into ranges by their boiling points so its density is irreproducible mainly due its nonreproducible composition. However, the thermophysical data for different compositions of biodiesels would be helpful in the designing of cost-effective biorefineries and other chemical processes. Received: February 6, 2012 Accepted: July 16, 2012 Published: July 31, 2012 2236

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Table 1. Description of Chemical Samples

a

chemical name

source

J. curcas biodiesel n-butanol n-pentanol

Synthesis Merck Merck

initial mass fraction purity

purification method

final mass fraction purity

analysis method

0.99 0.99

glass separatory funnel distillation distillation

0.997 0.998 0.998

GC-FIDa density measurement density measurement

Gas chromatography with flame ionization detection.

stearate were the major saturated fatty acid methyl esters (FAMEs) of J. curcas biodiesel. It is comprised of around 80 % unsaturated FAMEs. Further, the average molecular weight of J. curcas biodiesel was determined and found to be 289.5 g·mol−1. Density and Speed of Sound Measurement. The blends were formulated by weight with the help of a Mettler mass balance (Switzerland, AE-200). The accuracy of measurement was ± 0.0001 g. The most evaporative constituent (alcohol) was introduced first directly into the airtight, stoppered 5·10−6 m3 glass bottle, and its weight was taken. The second constituent was then inserted into the bottle through the lid with the help of a syringe. This technique avoids the momentous evaporation and contamination that may lead to composition uncertainties. The probable uncertainties in mole fraction by this method have been estimated to be lesser than 0.001. Densities (ρ) and speed of sound (u) measurements for pure constituents and their binary system at T = (288.15 to 308.15) K were performed using a density and

Therefore, we determined the densities and speed of sound values for binary mixtures of J. curcas biodiesel + n-butanol and n-pentanol at T = (288.15 to 308.15) K and ambient pressure. The aim of our work is to furnish new experimental data about densities, acoustic velocity, and the excess molar volumes VEmix for binary blends of J. curcas biodiesel with n-butanol and n-pentanol at T = (288.15 to 308.15) K and ambient pressure over complete range of composition.

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EXPERIMENTAL SECTION Chemicals and Their Purification. n-Butanol (AR grade, mass fraction w = 0.99, Merck) and n-pentanol (AR grade, mass fraction w = 0.99, Merck) were further cleaned.12 The purities of the purified liquids were verified by calculating their densities at T = (288.15 to 308.15 ± 0.01) K. These were in good agreement with their analogous literature values.13−24 Pure H2SO4 (Merck, mass fraction w = 0.98) was utilized as a catalytic agent for transesterification reaction. A further description of chemicals has been reported in Table 1. Biodiesel Synthesis. J. curcas seeds were collected from Haryana region (India), and oil was extracted from the collected seeds. Almost 278 g of oil was obtained from 1000 g of seeds (27.8 % oil content). Transesterification of J. curcas oil (triglycerides consisting of three chains of fatty acids all linked via a glycerin molecule) was carried out in a batch reactor to synthesize J. curcas biodiesel. The reactor is comprised of a 2.5 L reaction vessel equipped with a powered agitator (Kika Werke), a propeller, thermometer, and refluxing condenser. To synthesize biodiesel and regulate reaction temperature, a hot water circulation bath was used. The acid catalyzed transesterification was carried out for synthesizing the biodiesel. To carry out acid catalyzed transesterification reaction to produce fatty acid methyl esters (FAMEs), the chemical name of biodiesel, the reactor was filled with J. curcas oil, and H2SO4 in methanol was added to the reaction mixture. The reaction mixture was refluxed at 55 °C for 24 h. After completion of transesterification process, the resulting glycerin was removed with the help of a separatory funnel. The synthesized biodiesel (a mixture of methyl esters) was cleaned three times with hot 0.1 % aqueous tannic acid solution. The left-over water and methanol were separated on a rotary evaporator at atmospheric pressure. Biodiesel Characterization. In the transesterification reaction, for biodiesel synthesis, the fatty acids were cleaved from the glycerol to produce free fatty acids which further fused to either methyl or ethyl alcohol, depending on the type of alcohol used in the manufacturing process. Different fats or oils are comprised of diverse type of fatty acid chains. Hence, the investigation of the composition of biodiesel is required. The composition of the synthesized biodiesel was analyzed by gas chromatography with flame ionization detection (GC-FID). The carrier gas used in this technique was helium, and the gas line was furnished with oxygen. The J. curcas biodiesel was found to have methyl oleate, linoleate, palmitate, and stearate as reported in Table 2. Methyl palmitate and

Table 2. Composition of Fatty Acid Methyl Esters (FAMEs) Present in J. Curcas Biodiesel fatty acid methyl esters structure

composition (wt %)

common name

CH3(CH2)14COOCH3 CH3(CH2)16COOCH3 CH3(CH2)7CHCH(CH2)7COOCH3 CH3(CH2)4CHCHCH2CHC H(CH2)7COOCH3

16:0 (methyl palmitate) 18:0 (methyl stearate) 18:1 (methyl oleate) 18:2 (methyl linoleate)

15.88 6.15 41.85 35.32

Table 3. Comparison of Experimental and Literature Values of Densities (ρ) and Speed of Sound (u) for Pure J. curcas Biodiesel, n-Butanol, and n-Pentanol at T = (288.15 to 308.15) K and Atmospheric Pressure ρ/kg·m−3 component

T/K

exptl

lit.

exptl

J. curcas biodiesel

288.15 293.15 298.15 303.15 308.15 288.15 293.15 298.15 303.15 308.15 288.15 293.15 298.15 303.15 308.15

884.14 880.50 876.86 873.22 869.59 813.66 809.87 805.65 801.90 798.01 818.60 814.95 811.07 807.61 803.80

880.9013

1429.4 1411.3 1393.4 1375.6 1357.9 1274.2 1257.1 1239.2 1222.1 1209.0 1309.8 1292.7 1279.8 1258.1 1246.1

n-butanol

n-pentanol

2237

u/m·s−1

865.0014

805.6415 801.9116 798.0017

811.0820 807.6021 803.8022

lit.

1239.215 1222.018 1209.019

1280.023 1258.024 1246.022

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Table 4. Densities (ρmix) Excess Molar Volume (VEmix), and Speed of Sound (umix) for the J. curcas Biodiesel (1) + n-Butanol (2) Binary Mixture at T = (288.15 to 308.15) K and Atmospheric Pressure ρmix T/K

x1

288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15

0.0000 0.1152 0.1321 0.1445 0.2021 0.2830 0.3012 0.3642 0.3951 0.4265 0.4825 0.5152 0.5425 0.6320 0.6843 0.7244 0.7852 0.8672 0.9215 1.0000 0.0000 0.1152 0.1321 0.1445 0.2021 0.2830 0.3012 0.3642 0.3951 0.4265 0.4825 0.5152 0.5425 0.6320 0.6843 0.7244 0.7852 0.8672 0.9215 1.0000 0.0000 0.1152 0.1321 0.1445 0.2021 0.2830 0.3012 0.3642 0.3951 0.4265

kg·m

−3

813.66 838.11 840.73 842.52 849.86 857.89 859.53 864.10 866.10 867.97 870.93 872.46 873.66 877.03 878.66 879.76 881.19 882.70 883.44 884.14 809.87 834.04 836.66 838.46 845.79 853.86 855.40 860.12 862.14 864.01 866.99 868.54 869.73 873.10 874.74 875.84 877.30 878.85 879.66 880.50 805.65 829.86 832.49 834.30 841.67 849.79 851.33 856.09 858.11 860.06

VEmix·106 m ·mol 3

−1

0.000 −0.275 −0.307 −0.328 −0.421 −0.526 −0.567 −0.609 −0.635 −0.661 −0.697 −0.714 −0.725 −0.739 −0.725 −0.701 −0.637 −0.481 −0.324 0.000 0.000 −0.233 −0.263 −0.284 −0.370 −0.472 −0.493 −0.557 −0.584 −0.607 −0.643 −0.659 −0.667 −0.673 −0.656 −0.630 −0.565 −0.418 −0.279 0.000 0.000 −0.218 −0.246 −0.266 −0.348 −0.445 −0.463 −0.523 −0.547 −0.570

ρmix

umix −1

m·s

1274.2 1317.4 1322.7 1327.8 1341.7 1359.5 1364.3 1373.6 1378.3 1382.8 1390.0 1393.5 1396.6 1405.1 1409.8 1412.5 1416.8 1422.5 1425.3 1429.4 1257.1 1400.0 1306.3 1309.9 1325.4 1343.1 1346.6 1357.4 1362.0 1362.9 1373.2 1376.8 1379.7 1388.1 1392.6 1395.6 1399.9 1405.1 1407.9 1411.3 1239.2 1283.2 1288.4 1292.2 1307.6 1325.6 1329.2 1339.9 1344.7 1348.9

T/K

x1

298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15

0.4825 0.5152 0.5425 0.6320 0.6843 0.7244 0.7852 0.8672 0.9215 1.0000 0.0000 0.1152 0.1321 0.1445 0.2021 0.2830 0.3012 0.3642 0.3951 0.4265 0.4825 0.5152 0.5425 0.6320 0.6843 0.7244 0.7852 0.8672 0.9215 1.0000 0.0000 0.1152 0.1321 0.1445 0.2021 0.2830 0.3012 0.3642 0.3951 0.4265 0.4825 0.5152 0.5425 0.6320 0.6843 0.7244 0.7852 0.8672 0.9215 1.0000

kg·m

−3

863.01 864.56 865.78 869.19 870.86 871.99 873.48 875.10 875.94 876.86 801.90 826.09 828.70 830.51 837.86 845.96 847.49 852.23 854.26 856.14 859.15 860.71 861.92 865.35 867.02 868.17 869.68 871.36 872.24 873.22 798.01 822.21 824.82 826.61 833.91 841.95 843.48 848.19 850.22 852.10 855.13 856.71 857.94 861.45 863.19 864.38 865.96 867.70 868.61 869.59

VEmix·106

umix

m3·mol−1

m·s−1

−0.602 −0.613 −0.626 −0.630 −0.614 −0.590 −0.529 −0.391 −0.260 0.000 0.000 −0.210 −0.236 −0.254 −0.331 −0.420 −0.436 −0.489 −0.512 −0.531 −0.560 −0.571 −0.580 −0.580 −0.563 −0.543 −0.484 −0.360 −0.238 0.000 0.000 −0.206 −0.230 −0.245 −0.308 −0.377 −0.390 −0.431 −0.448 −0.463 −0.490 −0.503 −0.511 −0.526 −0.522 −0.511 −0.468 −0.360 −0.245 0.000

1356.0 1359.5 1362.6 1371.1 1375.4 1378.6 1382.7 1387.7 1390.5 1393.4 1222.1 1266.9 1272.2 1276.0 1291.6 1309.4 1312.9 1323.4 1327.9 1332.2 1339.0 1342.6 1345.5 1353.5 1357.7 1360.7 1365.0 1369.9 1372.7 1375.6 1209.0 1252.7 1258.0 1261.7 1276.9 1294.4 1297.8 1308.2 1312.6 1316.7 1323.2 1326.8 1329.4 1337.2 1341.3 1344.0 1348.0 1352.5 1355.2 1357.9

differs from region to region). The calculated uncertainties in density and acoustic velocity (speed of sound) values are ± 2·10−3 kg·m−3 and ± 0.1 m·s−1, respectively.

sound velocity meter (DSA 5000 M, Anton Paar). The instrument was calibrated with deionized water and air before each set of experimentation. The densities (ρ) and acoustic velocity (u) values of purified components are recorded in Table 3 and correlated with their corresponding literature values.13−24 Inconsistency in densities results and literature values of J. curcas biodiesel has been observed, and this may be due to its irreproducible composition (as the composition of J. curcas oil

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RESULTS AND DISCUSSION

J. curcas biodiesel (1) + n-butanol or n-pentanol (2) binary blends were prepared over whole composition range, and their 2238

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Table 5. Densities (ρmix), Excess Molar Volume (VEmix), and Speed of Sound (umix) for J. curcas Biodiesel (1) + n-Pentanol (2) Binary Mixtures at T = (288.15 to 308.15) K and Atmospheric Pressure ρmix T/K

x1

288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 288.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 293.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15

0.0000 0.0998 0.1354 0.1989 0.2251 0.2868 0.3264 0.3644 0.4042 0.4521 0.4850 0.5311 0.5891 0.6320 0.6987 0.7469 0.8257 0.8965 0.9465 1.0000 0.0000 0.0998 0.1354 0.1989 0.2251 0.2868 0.3264 0.3644 0.4042 0.4521 0.4850 0.5311 0.5891 0.6320 0.6987 0.7469 0.8257 0.8965 0.9465 1.0000 0.0000 0.0998 0.1354 0.1989 0.2251 0.2868 0.3264 0.3644 0.4042 0.4521

kg·m

−3

818.60 837.01 842.02 849.55 852.23 857.76 860.84 863.35 866.01 868.73 870.43 872.60 875.04 876.63 878.78 880.11 881.91 883.10 883.71 884.14 814.95 832.90 837.88 845.44 848.15 853.76 856.90 859.60 862.16 864.89 866.61 868.77 871.17 872.74 874.85 876.16 877.95 879.20 879.90 880.50 811.07 828.87 833.84 841.41 844.14 849.80 852.94 855.66 858.23 861.00

VEmix·106 m ·mol 3

−1

0.000 −0.289 −0.368 −0.485 −0.528 −0.612 −0.660 −0.669 −0.735 −0.773 −0.796 −0.820 −0.842 −0.846 −0.822 −0.782 −0.660 −0.467 −0.272 0.000 0.000 −0.220 −0.291 −0.408 −0.452 −0.547 −0.604 −0.651 −0.695 −0.734 −0.758 −0.778 −0.789 −0.782 −0.743 −0.691 −0.560 −0.381 −0.215 0.000 0.000 −0.188 −0.254 −0.367 −0.412 −0.510 −0.565 −0.612 −0.655 −0.697

ρmix

umix −1

m·s

1309.8 1337.6 1345.8 1358.9 1363.7 1373.9 1379.3 1384.2 1388.9 1393.9 1396.9 1401.0 1405.5 1408.8 1413.1 1416.5 1420.8 1425.5 1427.1 1429.4 1292.8 1321.6 1329.9 1342.8 1347.5 1357.3 1360.6 1367.4 1372.1 1376.7 1379.8 1383.5 1388.4 1391.3 1395.6 1398.5 1403.1 1406.8 1407.1 1411.3 1279.8 1308.3 1316.7 1329.0 1333.7 1343.1 1348.0 1352.5 1356.7 1361.3

T/K

x1

298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 298.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 303.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15 308.15

0.4850 0.5311 0.5891 0.6320 0.6987 0.7469 0.8257 0.8965 0.9465 1.0000 0.0000 0.0998 0.1354 0.1989 0.2251 0.2868 0.3264 0.3644 0.4042 0.4521 0.4850 0.5311 0.5891 0.6320 0.6987 0.7469 0.8257 0.8965 0.9465 1.0000 0.0000 0.0998 0.1354 0.1989 0.2251 0.2868 0.3264 0.3644 0.4042 0.4521 0.4850 0.5311 0.5891 0.6320 0.6987 0.7469 0.8257 0.8965 0.9465 1.0000

kg·m

−3

862.71 864.88 867.28 868.84 870.96 872.27 874.08 875.40 876.17 876.86 807.61 825.28 830.20 837.69 840.39 845.97 849.08 851.78 854.32 857.07 858.78 860.96 863.38 864.97 867.12 868.47 870.35 871.71 872.52 873.22 803.80 821.39 826.29 833.75 836.42 842.00 845.11 847.98 850.37 853.12 854.85 857.04 859.48 861.09 863.28 864.66 866.58 868.00 868.84 869.59

VEmix·106

umix

m3·mol−1

m·s−1

−0.719 −0.736 −0.740 −0.728 −0.684 −0.627 −0.495 −0.329 −0.183 0.000 0.000 −0.179 −0.239 −0.338 −0.378 −0.460 −0.508 −0.549 −0.584 −0.622 −0.640 −0.659 −0.665 −0.658 −0.622 −0.576 −0.463 −0.313 −0.178 0.000 0.000 −0.160 −0.213 −0.304 −0.337 −0.413 −0.456 −0.493 −0.530 −0.563 −0.582 −0.599 −0.608 −0.605 −0.573 −0.534 −0.431 −0.293 −0.166 0.000

1364.1 1367.6 1371.8 1374.7 1379.1 1381.6 1385.8 1389.3 1391.5 1393.4 1258.0 1287.1 1296.8 1309.1 1314.0 1323.9 1329.3 1333.8 1338.2 1343.0 1345.9 1349.8 1354.0 1356.9 1361.2 1364.1 1368.2 1371.5 1373.6 1375.6 1246.2 1274.4 1282.9 1295.9 1300.3 1309.8 1315.1 1319.4 1323.9 1328.2 1331.3 1334.8 1338.9 1341.5 1345.5 1347.9 1351.6 1360.8 1356.4 1357.9

where ρmix is the density of the solution and x1, x2, M1, M2, ρ1, and ρ2 are the mole fractions, molar masses, and densities of the parent liquids 1 and 2, respectively. Such VEmix values of the studied binary blends along with their densities (ρmix) and speed of sound data (umix) are reported in Tables 4 and 5. Further, these values are plotted and presented in Figures 5 and 6, as a function of x1 (the mole fraction

density (ρmix) and ultrasonic speed of sound (umix) values were determined in the temperature range of (288.15 to 308.15) K and atmospheric pressure (reported in Tables 4 and 5 and plotted in Figures 1 to 4). These values were employed to determine excess molar volumes VEmix data via eq1 E (Vmix ) = (x1M1 + x 2M 2)/ρmix − (x1M1/ρ1) − (x 2M 2 /ρ2 )

(1) 2239

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of biodiesel). The VEmix values for binary mixture were fitted to Redlich−Kister polynomials25

where x1 and x2 represent the mole fraction of component 1 and 2 in the binary mixture of J. curcas biodiesel (1) + n-butanol or n-pentanol (2), while An (n = 0 to 2) are adjustable constraints of binary mixture and were evaluated by leastsquares technique by employing VEmix data of binary mixtures. These adjustable parameters and standard deviation σ(VEmix), defined by eq 3, are recorded in Table 6

2 E Vmix = x1(1 − x1)[ ∑ A n(2x1 − 1)n ] n=0

(2)

E E E σ(Vmix ) = [∑ (X(exptl) − X(calc.eq.2) )2 /(m − n + 1)]0.5

(3)

where m denotes the total number of experimental points; (n + 1) represents the number of A(n) constants of eq 2. The density values reported in Table 3 shows that densities of synthesized biodiesel are higher than those of n-butanol and n-pentanol and are decreasing with increasing temperature. Simultaneously, Figures 1 and 2 indicate that densities of biodiesel + n-butanol or n-pentanol and binary blends are also declining with respect to temperature while increasing continuously with increasing amount of biodiesel and vice versa. Figure 1. Densities, ρmix, values of J. curcas biodiesel (1) + n-butanol (2) at ★, T = 288.15 K; ●, T = 293.15 K; ⬟, 298.15 K; ◆, 303.15 K; ▲, 308.15 K and atmospheric pressure.

Figure 4. Speeds of sound, umix values of J. curcas biodiesel (1) + npentanol (2) at ☆, T = 288.15 K; ○, T = 293.15 K; ⬠, T = 298.15 K; ◇, T = 303.15 K; △, T = 308.15 K and atmospheric pressure.

Figure 2. Densities, ρmix, values of J. curcas biodiesel (1) + n-pentanol (2) at ☆, T = 288.15 K; ○, T = 293.15 K; ⬠, 298.15 K; ◇, 303.15 K; △, 308.15 K and atmospheric pressure.

Figure 5. Excess molar volumes, VEmix, values of J. curcas biodiesel (1) + n-butanol (2) at ★, T = 288.15 K; ●, 293.15 K; ⬟, 298.15 K; ◆, 303.15 K; ▲, 308.15 K and atmospheric pressure. The solid lines represent the values calculated from the Redlich−Kister equation.

Figure 3. Speeds of sound, umix, values of J. curcas biodiesel (1) + nbutanol (2) at ★, T = 288.15 K; ●, T = 293.15 K; ⬟, T = 298.15 K; ◆, T = 303.15 K; ▲, T = 308.15 K and atmospheric pressure. 2240

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packing of the constituent of the mixtures in the mixed state as compared to the pure state.

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CONCLUSIONS The J. curcas biodiesel was synthesized, and its composition was evaluated by gas chromatography. The thermophysical properties such as densities (ρmix) and speeds of sound (umix) of J. curcas biodiesel (1) + n-butanol or n-pentanol (2) binary blends were evaluated with respect to mole fraction at T = (288.15 to 308.15) K and atmospheric pressure. The results reveal that the density of blends increases with an increase of mole fraction of biodiesel over investigated temperatures; however, the addition of n-butanol and n-pentanol to J. curcas biodiesel decreases the high density of biodiesel. Almost the same type of pattern has been noted for speed of sound data. Further, densities and speed of sound values have been reported to decrease with an increase of temperature. The experimental density values were utilized to analyze the excess molar volume VEmix. Further, these VEmix values were subjected to the Redlich−Kister polynomial equation to calculate the adjustable constraints together with standard deviations. The VEmix values obtained from Redlich−Kister polynomial equation are in good agreement with values calculated from the density data.

Figure 6. Excess molar volumes, VEmix, values of J. curcas biodiesel (1) + n-pentanol (2) at ☆, T = 288.15 K; ○, 293.15 K; ⬠, 298.15 K; ◇, 303.15 K; △, 308.15 K and atmospheric pressure. The solid lines represent the values calculated from the Redlich−Kister equation.

Table 6. Coefficients of Equation 2 along with Standard Deviations σ(VEmix) for Binary Mixtures at Different Temperatures T/K 288.15 293.15 298.15 303.15 308.15 288.15 293.15 298.15 303.15 308.15

A0·106 m3·mol−1 A1·106 m3·mol−1 A2·106 m3·mol−1 J. curcas Biodiesel (1) + n-Butanol (2) −2.841 −1.023 −1.142 −2.619 −0.919 −0.691 −2.455 0.854 −0.633 −2.279 −0.721 −0.631 −1.975 −0.770 −1.086 J. curcas Biodiesel (1) + n-Pentanol (2) −3.229 −1.153 −1.457 −3.068 −1.059 −0.337 −2.898 −0.912 0.130 −2.584 −0.863 −0.145 −2.349 −0.860 −0.171

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σ(VEmix)·106 m3·mol−1

AUTHOR INFORMATION

Corresponding Author

*Tel.: +82-2-2123-2761; fax: +82-2-312-6401. E-mail address: [email protected] (Satish Kumar); [email protected] (Il Moon).

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Funding

The authors are highly thankful to the Ministry of Education (MOE) of Korea through its BK21 Program and GAS Plant R&D Center funded by the Ministry of Land, Transportation and Maritime Affairs (MLTM) of Korean Government for funding this research work.

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Notes

The authors declare no competing financial interest.

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Due to the higher density of biodiesel related to diesel fuel, it is probable that sound velocity in biodiesel will be high as compared to diesel fuel, which can advance the injection timing. However, the lower density of n-butanol or n-pentanol can reduce this impact, resulting in a fine-tuning of this constraint of fuel injection system. This is indeed true as is evident from the densities and sound velocity data of biodiesel + n-butanol or n-pentanol binary mixtures, recorded in Tables 4 and 5. Further, results reported in Tables 4 and 5 and plotted in Figures 5 and 6 reveal that VEmix values are negative over the entire range of composition. The VEmix values are less negative at high temperatures as compared to low temperatures. However, for an equimolar mole fraction the VEmix values change as: n-pentanol > n-butanol. These negative VEmix values suggest strong molecular interactions between alcohol and biodiesel fatty acid methyl esters (FAMEs). The VEmix for the studied mixtures are due to cumulative effects arising from (i) dipole−dipole interactions between FAMEs, (ii) molecular arrangement, and (iii) rupture of associated molecular entities. The negative VEmix values for the investigated mixtures suggest that a contribution to VEmix due to dipole−dipole interactions is significant and there is a closer

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