Comparative Analysis on Property Improvement Using Fourier

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A comparative analysis on property improvement using FT- IR and NMR (1H and 13C) spectra of various biodiesel blended fuels I. Shancita, H. H. Masjuki, Md. Abul Kalam, S.S. Reham, and S.A. Shahir Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.5b02559 • Publication Date (Web): 10 May 2016 Downloaded from http://pubs.acs.org on May 12, 2016

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A comparative analysis on property improvement using FT- IR and NMR (1H and 13C) spectra of various biodiesel blended fuels I. Shancita1, H.H. Masjuki, M.A. Kalam2, S.S. Reham, S.A. Shahir Centre for Energy Sciences, Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia. Abstract The ever increasing energy demand has accelerated the research and development of renewable energy sources which can eventually decrease the dependence on fossil fuel reserve. Biodiesel, a renewable energy source, has received considerable attention as an alternative fuel for last few decades. In this study, biodiesels produced from two feedstocks were analyzed with fatty acid methyl ester (FAME) composition, fourier transform infrared (FT-IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy (1H and 13C) in order to improve their physicochemical properties and to find out the relationships among them. Here, the physicochemical properties of biodiesels produced from C. nucifera, and P. pinnata oils and their 5%, 10%, 20%, and 30% byvolume blends were compared with pure diesel (B0) according to ASTM D6751 standards. All of the biodiesels and their blends satisfied the conditions to be an alternative fuel with compared to diesel but pure C. nucifera biodiesel and their blends yielded more property improvement through their physicochemical property analysis and had the lowest carbon residue content. FAME composition, FT-IR and NMR spectra analysis ensured to have the better property of C. 1

Corresponding author. Department of Mechanical Engineering, University of Malaya, 50603, Kuala Lumpur, Malaysia.Tel.: +603 79674448; fax: +603 79675317 E-mail:[email protected] 2 Corresponding author. Department of Mechanical Engineering, University of Malaya, 50603, Kuala Lumpur, Malaysia.Tel.: +603 79674448; fax: +603 79675317 E-mail: [email protected]

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nucifera biodiesel and its blends through high ester content, transmittance and conversion rate respectively than P. pinnata biodiesel and thus regarded to be used commercially in diesel engine. Keywords: Cocos nucifera, Pongamia pinnata, FAME composition, Fourier transform infrared spectrometry, Nuclear magnetic resonance, carbon residue. Nomenclature FAME

Fatty acid methyl ester

FT- IR

Fourier transform infrared spectrometric

NMR

Nuclear magnetic resonance

ASTM

American society for testing and materials

CB5

5% coconut biodiesel+ 95% diesel

CB10


CB20


CB30


PB5

5% Pongamia pinnata biodiesel+ 95% diesel

PB10


PB20


PB30



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1. Introduction Nowadays, the lack of crude oil and emission of environmentally detrimental exhaust form combustion of diesel have shifted research attention towards renewable and alternative fuel sources, such as biodiesel. Biodiesel is a non-toxic, renewable, energy-efficient, biodegradable, non-flammable, and environment friendly source and is also low in sulfur content

1-3

. Biodiesel

exhibits similar properties to diesel and can be used as pure (B100) or blended with pure diesel in unmodified engines. Biodiesel also possesses high flash point values and positive energy balance because of lower fuel volatility and absence of alcohol

4-6

. Additionally, biodiesel

contains approximately 10% oxygen (by weight), which reduces hydrocarbon (HC), carbon monoxide (CO), particulate matter (PM), volatile organic compounds (VOCs), and sulfur dioxide (SOx) emissions

7-9

. Biodiesel, also known as fatty acid methyl ester, can be produced from

animal fat or vegetable oils through pyrolysis, transesterification, microemulsion, and dilution 1, 10, 11

. Biodiesel can be produced from edible and non-edible oil feedstocks. Although, the

extensive use of edible oils to produce biodiesel can cause major problems, such as high food price, higher feedstock cost and starvation in the developing countries, their better physicochemical properties as an alternative fuel can be more beneficial for clean environment. The most suitable option to reduce food shortage involves the use of non-edible oils as alternative to edible oil feedstocks 1, 8, 12. Pongamia pinnata is a multipurpose tree, whose seeds contain 30% to 40% oil. The tree is a cheap and widely available non-edible biodiesel source. Cocos nucifera is an edible biodiesel source and a popular biodiesel feedstock predominantly used in Asia 13-16. The quality of biodiesel depends on various factors, including their physical and chemical properties, the quality of feedstock, fatty acid composition, production process, post-production 3 ACS Paragon Plus Environment

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treatment, handling, and storage

17

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. Many researchers have analyzed the properties of different

biodiesels produced from edible and non-edible sources. Atabani et al.

18

reported the effect of

blending M. oleifera, C. nucifera and other biodiesels on the physicochemical properties of the final product. They observed improvement in kinematic viscosity, density, oxidation stabily and calorific value due to blending of biodiesels with diesel. P. pinnata is comparatively newer than the other two feedstocks mentioned earlier. Several studies have been conducted to determine the quality of biodiesel produced from this feedstock by analyzing its physicochemical properties, FT-IR spectrum and FAME composition, which revealed the similarity of the results with the present work 19, 20, 21. Tariq et al. 7 characterized fatty acid methyl ester and the conversion rate of triglycerides to methyl esters in biodiesel from rocket seed oil through 1H and

13

C NMR

spectroscopy analysis. In this study they confirmed the synthesis of biodiesel through FT-IR and NMR spectroscopy. Samios et al.

22

performed double-step transesterification to prepare

biodiesel from triglycerides; the resulted biodiesel was analyzed through 1H NMR to confirm purity and quality. Farooq et al.

23

analyzed waste cooking oil through 1H NMR and then

synthesized biodiesel from this oil to compare the conversion of waste cooking oil to methyl ester by using the bifunctional catalysts. The results showed improvement in transesterification reaction and the physicochemical properties of produced biodiesel was comparable with ASTM standard of specifications. Numerous studies have investigated the physicochemical properties and FT-IR and NMR spectra of biodiesel, but comparison between property improvement of C. nucifera, and P. pinnata biodiesels and the relationship of those properties with FAME composition, FT-IR and NMR spectra have yet to be presented. The main objectives of this study are to characterize the C. nucifera, and P. pinnata biodiesels and their blends through their physicochemical properties, 4 ACS Paragon Plus Environment

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FAME composition and FT-IR, NMR spectroscopy analysis and build a relationship of those physiochemical properties with those results obtained. These analysis methods were used here as they are well established and less time consuming for biodiesel characterization and these feedstocks were selected because of their availability in the South-east Asia and also to compare the edible and non-edible biodiesels properties by different methods. 2. Feedstock 2.1 Cocos nucifera (coconut) C. nucifera is a member of the genus Cocos and the Arecaceae family 24, 25. This tree is native in Malaysia, Indonesia, Myanmar, Philippines, Cambodia, Laos, Brunei, Thailand, Vietnam, and Singapore. The coconut tree grows up to30 m (90 ft) tall, with pinnate leaves of 4–6 m (13–20 ft) in length and pinnae of 60–90 cm in length. Old leaves break away cleanly, leaving the trunk smooth

24, 26

. The mean diameter of the tree is 30–40 cm at breast height, and the tree has a

terminal crown of leaves at the top. The tree grows at an altitude of about 520–900 m under a mean annual temperature of 20 °C to 28 °C and a mean annual rainfall of 1000–1500 mm

27, 28

.

Botanically, the coconut fruit is a drupe, not a true nut. Similar to other fruits, coconuts contain three layers: exocarp, mesocarp, and endocarp. Exocarp and mesocarp comprise the “husk” of the coconut. The mesocarp is composed of fiber, called coir, which presents several traditional and commercial uses

24, 29, 30

. The fruit reaches up to 5 cm long and 3 cm wide and is roughly

ovoid. The nut is 2 cm to 2.5 cm in diameter and 3 cm to 4 cm in length. The fruits are initially green and turn brownish as they mature, whereas the yellow varieties change from yellow to brown 27, 28.


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2.2 Pongamia Pinnata Pongamia pinnata (L.) Pierre (karanja or honge) is a fast-growing native tree in India. The tree is a medium-sized evergreen tree and belongs to the Legumnosae or Pappilonaceae family. The tree contains a short crooked trunk with a broad crown of spreading or drooping branches. The tree normally grows in the Indian subcontinent and Southeast Asia and has been introduced in humid tropical countries, such as Malaysia, Indonesia, Australia, Philippines, New Zealand, China, and USA. P. pinnata is known as a nitrogen-fixing tree and normally used for traditional medicines, shade, animal fodder, green manure, timber, water–paint binder, ornaments, pesticides, fish poison, and fuel. P. pinnata has received considerable attention as a non-edible biodiesel feedstock because its seeds contain 30% to 40% of oil by weight, with reddish brown color 8, 31, 32

. Approximately 96.6% to 97% biodiesel can be produced from this tree by applying two

transesterification steps, and the properties of the product satisfy the ASTM standard 8, 15. 3. Biodiesel production Crude C. nucifera oil was purchased from the local market. P. pinnata oil was purchased from India. Other materials, reagents, and chemicals, such as methanol, H2SO4, KOH, and Na2SO4, were obtained from LGC Scientific Sdn. Bhd. (Malaysia). 3.1 Production of C. nucifera and P. pinnata biodiesels As C. nucifera and P. pinnata oils contain high free fatty acid (FFA), a two-step procedure, involving acid esterification and transesterification, was performed to produce biodiesels to reduce the high acid value of the feedstocks. In esterification, the molar ratio of methanol was maintained at 12:1 (50% v/v oil) and 1%(v/v oil) of sulfuric acid (H2SO4) was added to the preheated oils at 60 °C and 600 rpm for 3 h in a glass reactor to refine the crude C. nucifera and P. 6 ACS Paragon Plus Environment

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pinnata oils. After reaction completion, the products were transferred to a separation funnel, in which the esterified oils (lower layer) were separated from the upper layer. The upper layer included excess alcohol, sulfuric acid, and impurities. The lower layer was then loaded into a control rotary evaporator (IKA) and heated at 60 °C under vacuum conditions for 1 h to remove methanol and water from the esterified oils. In transesterification, the esterified oils were reacted with 25% (v/v oil) of methanol and 1% (m/m oil) of potassium hydroxide (KOH) and maintained at 60°C and 600 rpm for 2 h. After reaction completion, the produced biodiesels were deposited in a separation funnel for 12 h to separate glycerol from the biodiesels. The upper layer was washed three times with hot distilled water. The formed methyl ester was poured into a control rotary evaporator (IKA) to remove water and excess methanol and then dried using Na2SO4.The lower layer containing impurities and glycerol was drained. The produced methyl ester was filtered with qualitative filter paper to obtain the final product of biodiesels. 4. Properties of biodiesel Several important properties of biodiesels were compared with those of pure diesel to determine the suitability and quality of the former. Different biodiesels exhibit different properties, depending on their production from different feedstocks, fatty acid composition, production process, and post-production treatments. These factors affect the operation of unmodified diesel engines supplied with diesel–biodiesel blends. The most notable properties of biodiesel include kinematic viscosity, density, flash point, cloud and pour point, cold filter plugging point (CFPP), oxidation stability, and calorific value. The properties of biodiesel should be characterized according to the international standard specifications of ASTM D6751 or EN 14214.


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4.1 FAME composition FAME compositions of C. nucifera, and P. pinnata biodiesels were determined using gas chromatography (GC) analysis in an Agilent 7890A model equipped with a flame ionization detector with HP- INNOWax column. Table 1 presents the specifications of the GC analyzer. Table 1: Specifications of GC analyzer Property Linear velocity Carrier gas Column dimension HP-INNOWax column flow Column head pressure Detector temperature Injector Injection size

Specifications 35.3 cm/s at 100° C Helium at 33.86 psi 30 m × 0.25 mm × 0.25 µm 3.5 mL/min 33.86 psi 250 ° C Spilt injector, 50:1 spilt ratio 0.3 µL Oven temperature program

Initial temperature Temperature ramp 1 Temperature ramp 2

50 ° C for 0 min 20 ° C/min to 210 ° C for 18 min 20 ° C/min to 230 ° C, hold for 13 min

4.2 Blending diesel and biodiesels The produced biodiesels were blended with pure diesel in a homogenizer at 2000 rpm. The height of the homogenizer can be adjusted by fixing it with a clamp on a vertical stand. The biodiesel was mixed with diesel at the selected speed by controlling the speed selector at the top of the homogenizer. 5. Biodiesel characterization method The physicochemical properties of C. nucifera, and P. pinnata biodiesels and their biodiesel blends were measured according to the ASTM D6751 standard. Viscosity, density, calorific value, flash point, pour point, cloud point, oxidation stability, cetane number, acid value, iodine


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value, and CFPP were assessed. Cetane number, iodine value (IV), and saponification value (SV) were also determined using fatty acid composition utilizing several empirical equations

33, 34

presented below: CN = 46.3 + (5458/SV) - (0.225* IV)

(1)

SV = ∑ (560* Ai)/Mwi

(2)

IV = ∑ (254*Ai*D)/Mwi

(3)

where Ai is the weight percentage of each fatty acid component, D is the number of double bonds in each fatty acid, and Mwi is the molecular mass of each fatty acid component. Table 2 presents the details, including manufacturer information, of necessary equipment used to analyze biodiesel properties. Table 2: Summary of equipment used to measure biodiesel properties Property

Equipment

Manufacturer

Test method

Accuracy

Kinematic viscosity Density Flash point

SVM 3000 SVM 3000 Pensky-martens flash point automatic NPM 440 Cloud and Pour point tester automatic NTE 450 873 Rancimat

(Anton Paar, UK) (Anton Paar, UK) (Norma lab, France) (Norma lab, France) (Metrohm, Switzerland) (Normalab, France) (IKA, UK) (Mettler Toledo, Switzerland)

ASTM D445 ASTM D1298 ASTM D93

0.1% ±0.1 kg/m3 ±0.1° C

ASTM D2500 ASTM D97 EN ISO 14112

±0.1° C

ASTM D6371

±0.1° C

ASTM D240 ASTM D664

±0.001 MJ/kg ±0.001 mgKOH/g

Cloud and pour point Oxidation stability Cold filter plugging point Calorific value Acid value

Cold filter plugging point tester -automatic NTL 450 C2000 basic calorimeter Automation titration rondo 20

±0.01 h


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6. Results and discussion 6.1 FAME composition of produced biodiesels Table 3 represents the FAME composition results from C. nucifera and P. pinnata biodiesels. The unsaturated fatty acid composition of C. nucifera and P. pinnata biodiesels were 8.8% and 74.3% respectively, in which the percentage of total monounsaturated fatty acid was 7.3% and 52.1% respectively. The monounsaturation occurred mainly due to the presence of methyl oleate C18:1 (7.3%) and the remaining unsaturation was for the polyunsaturated fatty acids which contained only the methyl linoleate C18:2 (1.5%) in case of C. nucifera biodiesel and for P. pinnata biodiesel the monounsaturated fatty acid comprises with methyl oleate C18:1 (50.9%) and methyl eiosenoate C20:1 (1.2%). The remaining unsaturation was due to the presence of methyl linoleate C18:2 (18.2%) and methyl Linolenate C18:3 (4.0%) polyunsaturated fatty acid. The saturated fatty acid composition of C. nucifera and P. pinnata biodiesels were 91.2% and 52.1% respectively. In C. nucifera biodiesel the total saturated fatty acid mainly contained methyl octanoate C8:0 (7.6%), methyl decanoate C10:0 (5.5%), methyl laurate C12:0 (47.4%), methyl myristate C14:0 (18.8%), methyl palmitate C16:0 (8.7%), methyl stearate C18:0 (2.7%) and methyl archidate C20:0 (0.1%). Meanwhile, P. pinnata biodiesel had predominantly saturated fatty acid of methyl palmitate C16:0 (9.7%), methyl stearate C18:0 (6.8%), methyl archidate C20:0 (1.6%) and methyl behenate C22:0 (5.6%). FAME composition has advantages on biodiesel and its blends quality and cold flow properties. The monounsaturated fatty acid present in biodiesel blends can improve fuel ignition quality and stability at low temperature. Although, high monounsaturated fatty acid is responsible for high oxidation stability, C. nucifera biodiesel had high oxidation stability than P. pinnata biodiesel


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having low monounsaturated fatty acid due to its natural antioxidant property. Moreover, C. nucifera biodiesel had higher cetane number than P. pinnata biodiesel because of its low polyunsaturated fatty acid content, which may also lead to low level nitrogen oxides (NOx) emissions 35. On the other hand, with the presence of saturated fatty acid alkyl ester in biodiesel blends the cetane number, cloud point and stability of those fuels increase. C. nucifera biodiesel had better cloud point and stability than P. pinnata biodiesel because of high total saturated fatty acid methyl ester 36-38. Meanwhile, P. pinnata biodiesel had high amount of saturated fatty acids of C16:0 and C18:0 and very long chain fatty acid of C22:0 than C. nucifera biodiesel which is responsible for very bad cold flow properties of P. pinnata biodiesel as they have high melting points. FAME composition of C. nucifera, and P.pinnata biodiesels can be compared with the previous works 14, 19, 36, 37, 39-41. Table 3: Fatty acid methyl ester (FAME) composition of C. nucifera and P. pinnata biodiesels Sl. no. 1 2 3 4 5 6 7 8 9 10 11 12

FAME Methyl hexanoate Methyl octanoate Methyl decanoate Methyl laurate Methyl myristate Methyl palmitate Methyl palmitoleate Methyl stearate Methyl Oleate Methyl Linoleate Methyl Linolenate Methyl archidate

Molecular weight 130.18

Formula

Structure 6:0

CB100 (wt%) 0.4

PB100 (wt%) -

CH3(CH2)4COOCH3

158.24

CH3(CH2)6COOCH3

8:0

7.6

< 0.1

186.29

CH3(CH2)8COOCH3

10:0

5.5

< 0.1

214.34 242.39

CH3(CH2)10COOCH3 CH3(CH2)12COOCH3

12:0 14:0

47.4 18.8

< 0.1 < 0.1

270.45

CH3(CH2)14COOCH3

16:0

8.7

9.7

268.43

CH3(CH2)5CH=CH(CH2)7COOCH3

16:1

< 0.1

< 0.1

298.50 296.49 294.47

CH3(CH2)16COOCH3 CH3(CH2)7CH=CH(CH2)7COOCH3 CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOCH3

18:0 18:1 18:2

2.7 7.3 1.5

6.8 50.9 18.2

292.46

CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOCH3

18:3

< 0.1

4.0

326.56

CH3(CH2)18COOCH3

20:0

0.1

1.6


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13 14 15 16 17

Methyl eiosenoate Methyl Behenate Methyl erucate Methyl Lignocerate Other Saturation Monounsaturated Polyunsaturated Total

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324.54

CH3(CH2)7CH=CH(CH2)9COOCH3

20:1

< 0.1

1.2

354.61

CH3(CH2)20COOH

22:0

< 0.1

5.6

352.59 382.66

CH3(CH2)7CH=CH(CH2)11COOH CH3(CH2)22COOH

22:1 24:0

< 0.1

1.6

91.2 7.3

0.4 52.1 52.1

1.5

22.2

100%

99.6%

6.2 Characterization of biodiesels Physicochemical properties of crude C. nucifera and P. pinnata oils, pure biodiesels and diesel– biodiesel blends were tested and compared with the ASTM D6751 standards. Table 4 represents the important physicochemical properties of crude oils and Table 5 shows the detailed physicochemical properties of pure C. nucifera (CB100), and P. pinnata (PB100) biodiesels and their 5%, 10%, 20% and 30% by-volume blends with pure diesel. All the properties of crude oils, C. nucifera, and P. pinnata biodiesels and their respective blends satisfied the requirements according to the ASTM D6751 standard. As these biodiesels and their respective blends exhibited similar properties to pure diesel, they can be used as alternative fuel in unmodified diesel engines. 6.3 Property analysis of biodiesels Figures 1 to 5 show the improvement in properties of pure C. nucifera (CB100) and P. pinnata (PB100) biodiesels, as well as their 5%, 10%, 20%, and 30% by-volume blends with pure diesel, in terms of kinematic viscosity, density, oxidation stability, flash point, calorific value and cold filter plugging point (CFPP). 12 ACS Paragon Plus Environment

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Table 4: Physicochemical properties of crude C. nucifera, and P. pinnata oils Property

Units

Standard

Coconut

Pongamia

Kinematic viscosity at 40°C Dynamic viscosity at 40°C

mm²/s mPa.s

27.036 24.530

44.174 40.806

Density at 15°C Flash point Cloud point Pour point Oxidation stability Acid value Calorific value Cold filter plugging point

Kg/m3 °C °C °C h mg KOH/g MJ/kg °C

ASTM D445 ASTM D7042 ASTM D1298 ASTM D93 ASTM D2500 ASTM D97 EN ISO 14112 ASTM D664 ASTM D240 ASTM D6371

907.800 at 40° C 226.5 14 8 40.71 7.25 38.847 20

941.2 230.5 2 -1 13.47 9.343 37.546 24


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Table 5: Physicochemical properties of C. nucifera, and P. pinnata biodiesels and their blends Property

Units

Stand ard

AST M D675 1

CB100

PB100

CB5

PB5

CB10

PB10

CB20

PB20

CB30

PB30

Diesel

Kinematic viscosity at 40°C

mm²/ s

AST M D445

1.9-6

2.7089

5.0347

3.4508

3.5596

3.3752

3.6146

3.2588

3.7365

3.1527

3.8547

3.7160

Dynamic viscosity at 40°C

mPa.s

-

2.3175

4.3989

2.8301

2.9230

2.7746

2.9778

2.6899

3.0980

2.6133

3.2161

3.0484

Density at 15°C

Kg/m

AST M D704 2 AST M D129 8 AST M D93 AST M D250 0 AST M D97 EN ISO 14112 AST M D613 AST

860894

875.2

894.7

839.7

838.9

841.9

843.3

846.4

849.3

849.1

854.8

839.1

130 min

166.5

222.5

87.5

87.5

94.5

90.5

92.5

91.5

91.5

91.5

77

-3 to 12

1

13

3

4

8

5

8

7

8

9

2

-15 to -16

-3

5

-1

2

-1

2

-14

3

-11

3

1

3h min

8.14

6.70

40.96

12.08

40.83

12.04

12.28

21.20

12.37

16.80

12.36

47 min

65.77

56.13

-

-

-

-

-

-

-

-

48

≤0.5

0.373

0.393

-

-

-

-

-

-

-

-

0.266

3

Flash point

°C

Cloud point

°C

Pour point

°C

Oxidation stability

h

Cetane number

Acid value

-

mg


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Iodine value

Saponification value Calorific value

KOH/ g g I/100 g MJ/k g

Cold filter plugging point

°C

Carbon (C)

Wt%

Hydrogen (H)

Wt%

Oxygen (O)

Wt%

C/H ratio Empirical formula

-

M D664 EN 14111 AST M D240 AST M D637 1 AST M D529 1 AST M D529 1 AST M D529 1 -

-

9.28

86.46

-

-

-

-

-

-

-

-

-

-

253.19 39.770

186.41 38.190

44.853

44.774

44.585

44.427

44.05

43.734

43.515

43.041

45.669

-

+4

20

+3

+3

+4

+3

+5

+5

+4

+7

+3

-

71.6

74.0

84.52

84.64

83.84

84.08

82.48

82.96

81.12

81.84

85.2

-

13.3

12.4

14.73

14.68

14.65

14.56

14.5

14.32

14.35

14.08

14.8

-

15.1

13.6

0.755

0.68

1.51

1.36

3.02

2.72

4.53

4.08

0

-

5.39 C5.97H1 3.19O0.9

5.97 C6.17H1 2.3O0.85

5.74 C7.04H1 4.61O0.05

5.77 C7.05H14.5 6O0.04

5.72 C6.99H14.5 3O0.09

5.77 C7H14.45 O0.085

5.69 C6.87H14.3 9O0.19

5.79 C6.91H14.2 1O0.17

5.65 C6.76H14.2 4O0.28

5.81 C6.82H13.97 O0.26

5.76 C7.1H14 .68

4

6.3.1 Kinematic viscosity Viscosity of liquid fuels means the resistivity of flow of the fuel of their composing layers. It is caused by the intermolecular attraction forces of liquid fuel. It is one of the most important properties of biodiesel as it influences the fuel injection system specially the spray 15 ACS Paragon Plus Environment

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Page 16 of 49

atomization, penetration of the injected jet, air-fuel mixture combustion quality at low temperatures. Biodiesels have higher viscosity than diesel fuel because of the presence of electronegative oxygen which makes the biodiesels more polar than diesel 8, 17, 31. Figure 1 represents improvement in the kinematic viscosity of two biodiesels, and diesel–biodiesel blends at 40° C. The kinematic viscosity of pure biodiesel (B100) was quite similar to that of pure diesel. In this case, P. pinnata biodiesel showed the highest viscosity, whereas C. nucifera biodiesel demonstrated the lowest viscosity, which was even lower than that of pure diesel. All 5% biodiesel–diesel blends presented lower viscosity than pure diesel. The P. pinnata blend showed slightly higher viscosity than the other blends, whereas the C. nucifera blend showed the lowest viscosity. A similar trend was observed in all the 10%, 20%, and 30% biodiesel–diesel by-volume blends. In these cases, the P. pinnata blend exhibited the higher viscosity, whereas the C. nucifera blend exhibited the lower viscosity in all cases than diesel. Hence, C. nucifera biodiesel and its blends exhibited the lowest viscosity among all the fuels (including diesel) and penetrated easily during spray atomization in the combustion chamber, produce less deposits and engine wear. These results have the similarity with previous works 18-20, 28, 39, 40.


Page 17 of 49

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Energy & Fuels

6.3.2 Density Density is the measure of mass per unit volume of a solid or liquid. According to the standard state of determination 15°C is the temperature that should be maintained during measuring density. It is an important parameter for fuel property as because it affects the fuel atomization and combustion which indicates the ignition quality of a fuel in diesel engine. The density of biodiesel is normally higher than diesel as the density of biodiesel depends on its fatty acid composition, molar mass, water content, purity and temperature

17, 31

. Figure 2 shows the

improvement in density of two biodiesels, and diesel–biodiesel blends compared with pure diesel at 15°C. Compared with B100, P. pinnata biodiesel presented the highest density, whereas C. nucifera biodiesel showed the lowest density. C. nucifera biodiesel possessed lower density than pure diesel. Low density enhances fuel atomization and combustion quality; thus, C. nucifera biodiesel is a more suitable alternative to diesel compared with the other biofuels. In all biodiesel–diesel blends, the P. pinnata biodiesel–diesel blends showed the highest density, whereas the C. nucifera biodiesel–diesel blend showed lower density than pure diesel. C. nucifera biodiesel blends also exhibited low viscosity and density than P. pinnata biodiesel blends because of low viscosity and density of pure C. nucifera biodiesel. Most previous works can be comparable with these results 18-20, 28, 36, 40. 6.3.3 Oxidation stability Oxidation stability affects the biodiesel quality by oxidizing during storage for distribution or in the fuel system. In fact, it influences the tendency of degradation of biodiesel. As biodiesels are fatty acid methyl ester they oxidize automatically to form aldehydes, ketons and resins, which makes the fuel useless to run in the engine. The oxidization rate of biodiesel depends on


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Page 18 of 49

temperature, fatty acid composition, reaction catalyst, radiation intensity, light etc 17, 31. Figure 3 shows the improvement in the oxidation stability of two biodiesels and diesel–biodiesel blends compared with pure diesel. The oxidation stability range of pure biodiesel (B100) was considerably lower than that of pure diesel and other blends. C. nucifera biodiesel showed the highest oxidation stability. Meanwhile, for all 5% by-volume blends with diesel, the C. nucifera biodiesel–diesel blend exhibited the highest oxidation stability. In 10% blends, the C. nucifera biodiesel–diesel blend showed almost the same result as 5% blend, whereas the P. pinnata biodiesel–diesel blend showed the lowest oxidation stability characteristics. However, oxidative stability was nearly identical in 20% and 30% by-volume blends of biodiesel with diesel. In both cases, the P. pinnata blends showed the highest duration of resistance to oxidation. Among the low-volume-percentage diesel–biodiesel blends, C. nucifera biodiesel and its blends exhibited the highest oxidation stability. For high-volume-percentage diesel–biodiesel blends, P. pinnata biodiesel exhibited the highest oxidation stability. Hence, biodiesel blends demonstrated higher oxidation stability than pure diesel but was not comparable with pure biodiesel (B100). These results have the consistency with the previous works 18-20, 28, 36, 40.


Page 19 of 49

Kinematic viscosity (mm²/s)

Kinematic viscosity improvement 6 5 4 3 2 1 0 B100

B30

B20

Coconut

B10

Pongamia

B5

B0

Diesel

Fig. 1: Improvement in kinematic viscosity at 40° C of biodiesels, and diesel–biodiesel blends compared with pure diesel

Density improvement 900 Density (kg/m³)

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Energy & Fuels

880 860 840 820 800 B100

B30

B20

Coconut

B10

Pongamia

B5

B0

Diesel

Fig 2: Improvement in density at 15° C of biodiesels, and diesel–biodiesel blends compared with pure diesel


Energy & Fuels

Oxidation stability improvement 42 Oxidation Stability (h)

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Page 20 of 49

36 30 24 18 12 6 0 B100

B30

Coconut

B20

B10

Pongamia

B5

B0

Diesel

Fig 3: Improvement in oxidation stability at 110° C of biodiesels, and diesel–biodiesel blends compared with pure diesel 6.3.4 Flash point Flash point indicates that temperature at which it will ignite when it revealed to an ignition source such as a spark or flame. It is a very important property to measure the hazardous level of fuel as it influences fuel storability, transportability and distribution. It does not affect the combustion process and it varies inversely with fuel's volatility. Biodiesels have higher flash point than diesel which has the range of flash point between 55- 67° C. High flash point renders biodiesels safe for storage, transportation, and handling. Moreover, high flash point indicates the absence of alcohol, which decreases the value of flash point, in biodiesel 17, 31. Figure 4 presents the flash point improvement in two biodiesels and diesel–biodiesel blends compared with pure diesel. Pure biodiesel (B100) presented higher flash point than pure diesel. All the biodiesels under study exhibited high flash point values. Among all biodiesels, P. pinnata biodiesel exhibited the highest flash point value and C. nucifera biodiesel the lowest value. The flash point 20 ACS Paragon Plus Environment

Page 21 of 49

values of the two biodiesels were considerably higher than that of pure diesel. Similarly, the flash point values of all blended fuels were higher than that that of pure diesel. In the first three blends (5%, 10%, and 20%), the C. nucifera blend presented the highest flash point. For the 30% biodiesel–diesel blends, all the two biodiesels exhibited the same flash point value, all the results have similarity with previous works 18-20, 28, 36, 40.

Flash point improvement 250 Flash point (°C)

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

Energy & Fuels

200 150 100 50 0 B100

B30

B20

Coconut

B10

Pongamia

B5

B0

Diesel

Fig. 4: Improvement in Flash point of biodiesels, and diesel–biodiesel blends compared with pure diesel


Energy & Fuels

Calorific value improvement 48 Calorific value (MJ/kg)

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

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46 44 42 40 38 36 34 B100

B30

B20

Coconut

B10

Pongamia

B5

B0

Diesel

Fig. 5: Improvement in calorific value of biodiesels, and diesel–biodiesel blends compared with pure diesel

6.3.5 Calorific value Calorific value or heating value is also an important property of fuel. Heating value is defined as the amount of heat exhausted by burning a unit quantity of fuel in presence of oxygen at a constant volume enclosure. The combustion products are carbon dioxide, sulfur dioxide, nitrogen and water. Biodiesels have lower heating value than diesel fuel because of the deviation in the hydrogen and carbon content and presence of high oxygen molecule that decreases the heating value about 10-13 percent in biodiesel than diesel. Heating value of biodiesel increases with its number of carbon atoms and decreases with its number of double bonds respectively. Calorific value, viscosity and cetane number of biodiesels increase with the increasing number of carbon chain length and decreases with increasing unsaturation level, where the tested total unsaturation (mono and poly) level of C. nucifera and P. pinnata biodiesel are 8.8% and 74.3% respectively 22 ACS Paragon Plus Environment

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Energy & Fuels

17, 31

. Although, P. pinnata biodiesel had higher unsaturated fatty acid methyl ester it had higher

viscosity because of having high oxygen content. Figure 5 shows the improvement in the calorific values of two biodiesels and diesel–biodiesel blends compared with pure diesel. Compared with pure biodiesel (B100), C. nucifera and P. pinnata biodiesels presented the higher and lower heating values, respectively, and their heating values were lower than that of pure diesel. Among the 5%, 10%, 20%, and 30% biodiesel–diesel blends, C. nucifera and P. pinnata showed highest value for 5% blends and lowest value for 30% blends. Pure biodiesels had lower heating value than all other blends and diesel. However, all the blends showed lower values than pure diesel, as a consequence of their higher oxygen and different hydrogen and carbon contents. Most of the results are comparable with previous works 18-20, 28, 36, 40. 6.3.6 Cold filter plugging point (CFPP) CFPP is defined as the lowest temperature at which the fuel filter plugged due to the formed wax or gel crystal of the fuel components. This causes to the obstruction of the fuel flow specially at low temperature. CFPP indicates the low temperature operability of the fuel. CFPP limits the fuel's filterability and it has a lower value than CP of a particular fuel. However, as CFPP measure associates rapid cooling condition it does not truly shows the fuels operational limit at low temperatures. CFPP depends on the climate of different regions or countries for a particular biodiesel produced from different feedstock

8, 17, 31

. Figure 6 represents the improvement in

CFPP of two biodiesels and diesel–biodiesel blends compared with pure diesel. In case of pure biodiesels, C. nucifera had lower CFPP value than P. pinnata. Among the 5%, 10%, 20%, and 30% biodiesel–diesel blends, C. nucifera had slight deviation and P. pinnata had large deviation of CFPP values. However, all the blends showed mostly similar CFPP values with diesel


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Page 24 of 49

including C. nucifera biodiesel blends had the nearest values with diesel CFPP. Those results can also be comparable with previous literatures 18, 19, 28, 36, 39, 40. 6.3.7 Elemental composition analysis Figure 7, 8 and 9 present the major element composition of two biodiesels and their blends with diesel. In general, biodiesels and biodiesel–diesel blends contain carbon, hydrogen, and oxygen, whereas pure diesel only contains carbon and hydrogen. High oxygen content in biodiesels influences complete combustion in the chamber by inducing the oxidation of unburned hydrocarbons. As such, CO and HC emissions are lower in biodiesels and diesel–biodiesel blends than that in conventional diesel because complete combustion consumes the formed ignitable mixture of unburned gases in the chamber. In all the biodiesels, diesel–biodiesel blends, and pure diesel, carbon constitutes the highest percentage among all elements. In the case of pure biodiesels, PB100 contained higher carbon percentage than CB100. Conversely, CB100 contained the higher oxygen content than PB100. Hydrogen content was nearly identical in all cases of pure biodiesels and their blends, with PB100 showing the lowest hydrogen content. In the 5%, 10%, 20%, and 30% blends of diesel and biodiesel, C. nucifera and P. pinnata exhibited the mostly similar percentage of carbon contents and C. nucifera exhibited slightly higher percentage of oxygen content. Therefore, C. nucifera biodiesel and their blends exhibited more complete combustion characteristics than the other biodiesel and blends. The results have the compatibility with previous works 17, 19.


Page 25 of 49

CFPP improvement 20

CFPP (°C)

15 10 5 0 B100

B30

Coconut

B20

B10

Pongamia

B5

B0

Diesel

Fig. 6: Improvement in cold filter plugging point of biodiesels, and diesel–biodiesel blends compared with pure diesel

Carbon percentage 86 83 Carbon (wt%)

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80 77 74 71 68 65 CB100 PB100 CB30 PB30 CB20 PB20 CB10 PB10 CB5

PB5 Diesel

C (wt%)

Fig. 7: Carbon percentage analysis of biodiesels and diesel–biodiesel blends with pure diesel


Energy & Fuels

Hydrogen percentage 15 Hydrogen (wt%)

14.5 14 13.5 13 12.5 12 11.5 11 CB100PB100 CB30 PB30 CB20 PB20 CB10 PB10 CB5

PB5 Diesel

H (wt%)

Fig. 8: Hydrogen percentage analysis of biodiesels and diesel–biodiesel blends with pure diesel

Oxygen percentage 16 14 Oxygen (wt%)

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

Page 26 of 49

12 10 8 6 4 2 0 CB100 PB100 CB30 PB30 CB20 PB20 CB10 PB10 CB5

PB5 Diesel

O (wt%)

Fig. 9: Oxygen percentage analysis of biodiesels and diesel–biodiesel blends with pure diesel


Page 27 of 49

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Energy & Fuels

6.4 Fourier transform infrared spectroscopy analysis of diesel and biodiesels Diesel and biodiesel were characterized through FT-IR by using a Perkin–Elmer biodiesel FAME analyzer connected with an MIR TGS detector. The spectrum range was 4000–450 cm−1, and resolution and scans were 4 cm−1 and 16, respectively. The spectrum was processed by espectrum software. Figures 10 depict the comparison of FT-IR scans for diesel, CB100 and PB100 respectively. Tables 6 shows the details of each functional group and percentage of transmittance of each absorbance peaks in pure diesel, CB100 and PB100 respectively. Figure 10 and Table 6 present strong absorbance peaks for pure diesel, CB100 and PB100 between 2850 and 3000 cm−1; these peaks correspond to the presence of the stretching vibration of the C-H bond of the alkane group. The other corresponding peaks of this alkane group were found between 1350 and 1480 cm−1, as well as between 700 to 720 cm−1, which are attributed to the C-H bending vibration and C-H rock vibration mode, respectively. All single bonds represent the saturated functional groups. The presence of strong absorbance peaks between 1735 and 1750 cm−1 represents the carbonyl group of the C=O bond, which is known as ester and consists of unsaturated functional groups. Moreover, strong peaks between 1000and1300 cm−1 correspond to the stretching vibration of the C-O bond of the ester group. The absence of any broad peaks of O-H stretching vibration of carboxylic acids in the region of 2500–3300 cm−1indicates the absence of moisture in those biodiesels and diesel.


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Fig. 10: Comparison of FT-IR spectrum diagram of pure diesel, CB100, and PB100


Page 29 of 49

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Energy & Fuels

Table 6: FT-IR spectrum analysis of pure diesel, CB100 and PB100 Frequency range (cm-1)

Bond type

Functional group

Intensity

Assignment

Fuel

2850-3000

C-H stretching

Alkanes

Strong

1350-1480

-C-H bending

Alkanes

Medium

CH3, CH2 and CH (2 or 3 bands) CH2 and CH3 deformation

700-725 1735-1750

C-H rock C=O stretching

Alkanes Esters

Weak Strong

CH2 rocking C=O

1000-1300

C-O stretching O-H stretching

Esters

Two bands or more Strong, very board

O-C (2 bands)

Diesel, CB100, PB100 Diesel, CB100, PB100 Diesel, Diesel, CB100, PB100 CB100, PB100 -

2500-3300

Carboxylic acids

O-H (very board)

Peak (cm-1)

% Transmittance

Diesel 2954.89, 2922.9, 2853.41 1377.22, 1462.24

CB100 2923.93, 2854.26

PB100 2922.97, 2853.55

1464.54, 1436.06

722.04 1746.91

-

CB100 73.98, 81.95

PB100 65.923, 74.08

1462.97, 1435.92

Diesel 81.753, 64.65, 75.18 88.68, 92.94

92.58, 91.70

85.31, 83.55

1742.87

1741.66

98.17

76.17

66.58

1196.36, 1170.40 -

1195.72, 1168.30 -

-

89.542, 87.60 -

79.93, 75.44 -

-

Based on the transmittance FT-IR spectra, we can conclude that pure diesel mostly contain aliphatic compounds, whereas biodiesels mainly contain methyl ester compounds. The ester compounds are more abundant in biodiesels than that in pure diesel. The FTIR spectra of pure diesel and biodiesels are similar to each other, with slightly different peaks in certain regions. Among all the biodiesels and diesel, CB100 showed the highest percentage of transmittance. Hence, CB100 is more suitable alternative to pure diesel in an unmodified diesel engine. Numerous researchers characterized biodiesels through FT-IR spectroscopy and presented results


Energy & Fuels

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similar to those in the present study. Nabi et al.

19

Page 30 of 49

determined the properties of P. pinnata

biodiesel through FT-IR spectroscopy and showed a similar ester peak around 1741 cm−1 and between 1000 and 1300 cm−1. Farooq et al.

23

performed FT-IR analysis of waste cooking oil

and its biodiesel and showed the similarity of the spectra between them. Ndana et al.

42

stated

that the presence of C-H group in diesel and biodiesels affect the pour and cloud point properties; as such, these fuel samples exhibit poor cold flow properties during engine operation in cold weather. However, the presence of the unsaturated carbonyl group (C=O) in biodiesels maintains the liquid state of fuels but may cause oxidation during storage. Moreover, from the FT-IR spectrum of both of the biodiesels we can get the information about the stability and structure of them by observing the presence and nature of functional groups in the biodiesels. FT-IR spectrum can also be used for the determination of any contamination present in a very low percentage by finding any peak at 1170.83 cm-1 of C-N group (cyanide group) at stretching mode of vibration. Hence, there was no such peak found in both of the biodiesels, so it can be said that there are no impurities. The presence of single bonded functional groups of C-O and -C-H in both the PB100 and CB100 biodiesels is responsible for poor cold flow properties and PB100 biodiesel had bad cold flow properties than CB100 because of having less percentage of absorbance at those functional groups defined peaks. Moreover, the low value of absorbance at 1740 cm-1 of PB100 indicates the high unsaturated fatty acid presented in that biodiesel, hence PB100 had lower calorific value than CB100 as calorific value increases with decreasing unsaturation level. Moreover, CB100 has higher cetane number and oxidation stability because of high saturated fatty acid than PB100 as all the single bonds presented in that biodiesel represent the saturated fatty acid and it has high absorbance value at those peaks 43, 44.


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Energy & Fuels

6.5 NMR spectroscopy analysis of biodiesels NMR analysis of biodiesels was conducted by using a Bruker Ascend

TM

600 MHz NMR

spectrometer with a 5 mm PABBO BB probe for 1H and 13C NMR spectroscopy observation at 299 K. The spectra for 1H and 1

13

C were obtained at 600 MHz for 15 min and 5 h duration for

Hand 13C, respectively. Deuterated chloroform (CDCl3) was used as solvent. 1H and 13C spectra

were obtained with 30° pulse duration, a recycle delay of 1.0 s and 16 scans for 1H and 2.0 s and 6000 scans for 13C. 6.5.1 1H NMR analysis The 1H NMR spectra of PB100 and CB100 are shown in Figures 11 (a) and (b), respectively. These spectra also provide the information about hydrogen environment in the molecule. The proton NMR for PB100 had 8 hydrogen environment whereas CB100 had 5 hydrogen environment. The number of hydrogen type is the number of signals found in different chemical shifts. In Table 7 and 8 all the characteristics of 1H and 13C NMR chemical shifts of PB100 and CB100 are listed respectively. In these tables the type of splitting, spin-spin splitting, coupling constant and the proton abundance in percent are also presented. PB100 and CB100 showed the characteristic signal of CDCl3at 7.29 ppm and 7.28 ppm respectively

45

. In case of PB100, the multiplet signal at 5.36 ppm indicates the presence of

olefinic protons (-CH=CH-) bonded to carbon atoms, which had 5.5% of hydrogen abundance in PB100 biodiesel. The singlet signal at 3.7 ppm represents the methoxy protons of methyl ester (CH3COO-CH), which contains about 8.2% of hydrogen abundance and the triplet signal at 2.8 ppm which has 1.4% hydrogen abundance are due to bis-allylic proton (-C=C-CH2-C=C-) signal of the polyunsaturated fatty acid chain that are also attached to the carbon atoms in that 31 ACS Paragon Plus Environment

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biodiesel. Meanwhile, the triplet signal at 2.3 ppm are due to the presence of the α- methylene protons of ester (-CH2-COOMe) and contains about 5.5% hydrogen abundance in the biodiesel. The multiplet signal at 2.04 represents the α-methylene protons of the double bond (-CH2-C=C-) and triplet signal at 1.64 ppm represents β- methylene of ester (CH2-C-CO2Me) and they had 8.2% and 6.8% of hydrogen in that biodiesel. However, the quartet signals at 1.28 ppm which had 56.2% of hydrogen abundance and the triplet signal at 0.9 ppm of 8.2% hydrogen abundance indicate the protons of the methylene (-(CH2)n-) backbone of long fatty acid chains and the terminal methyl protons (C-CH3) respectively. 7, 23, 46. CB100 showed the characteristic signals at the same chemical shift as PB100, with certain exceptions at several shifts. In this case, no signals were found for olefinic protons (-CH=CH-), bis-allylic protons of unsaturated fatty acids and α-methylene protons of the double bond (-CH2C=C-) 7, 23, 46. Moreover, there was a pentent signal at 1.63 ppm which had 7.7% of hydrogen in CB100, a triplet signal at 1.3 which contains 61.5% hydrogen abundance and 0.89 ppm which had 11.5% of hydrogen abundance represent the β- methylene of ester (CH2-C-CO2Me) and the protons of the methylene (-(CH2)n-) backbone of long fatty acid chains, the terminal methyl protons (C-CH3) respectively.


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Energy & Fuels

Fig: 11 (a)


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Fig: 11 (b) Fig. 11: 1H NMR spectra of (a) PB100 (b) CB100 The conversion percentage of crude oil to biodiesel methyl esters through transesterification can be obtained from the 1H NMR spectrum 47, 48. The yield of the transesterification reaction can be evaluated using the following equation:

100

(1)

where = the conversion of triglyceride feedstock to the corresponding methyl esters; = the integration value of the methoxy protons of methyl esters; and = the integration value of α- methylene protons.


Page 35 of 49

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Energy & Fuels

By using this equation, we calculated the percentage conversion of triglyceride feedstock to the corresponding methyl ester for P. pinnata, and C. nucifera biodiesels. The rates of conversion of P. pinnata and C. nucifera feedstock to the corresponding methyl esters were 97% and 98.7%, respectively. These yield percentages confirmed that all triglyceride feedstocks were successfully converted to the corresponding methyl esters and thus confirm the purity and quality of the produced biodiesels. 6.5.2 13C NMR analysis The

13

C NMR spectra of PB100 and CB100 are shown in Figures 12 (a) and (b) respectively.

For both biodiesels there are 6 signals for 6 different types of carbon. For PB100, the characteristic singlet signal at 174.24 ppm indicates the presence of the ester carbonyl carbon (COO-) of biodiesel. Unsaturation in methyl esters is indicated by olefinic carbons, which appear at the doublet signal of 129.75 ppm. The presence of the methoxy carbons of esters (C-O) is confirmed by the singlet signal at 51.41 ppm. The characteristic multiplet signal at 29.7 ppm are due to the presence of long carbon chain of methylene carbons of fatty acid methyl esters. Moreover, the terminal carbons of methyl moiety appear at 14.1 ppm. Meanwhile, CB100 showed the characteristics peaks almost similar to PB100 7, 9.


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Fig: 12 (a)


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Energy & Fuels

Fig: 12 (b) Fig. 12: 13C NMR spectra of (a) PB100 (b) CB100


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Table 7: Characteristics of 1H and 13C NMR chemical shifts of PB100 Type of proton

Type of compound

-CH=CH-

olefinic protons

CH3COOCH (-C=CCH2-C=C) -CH2COOMe

methoxy protons of methyl ester bis-allylic proton

-CH2C=C-

CH2-CCO2Me -(CH2)n-

(C-CH3)

α- methylene protons of ester α-methylene protons of the double bond β- methylene of ester Methylene protons of long fatty acid chain terminal methyl protons

Chemical shift, δ (ppm) 5.36

Type of splitting Multiplet

3.7

Singlet

2.8

Triplet

2.3

Triplet

2.04

Multiplet

1.64

Triplet

1.28

Quartet

0.90

Triplet

SpinSpin splitting 5H adjacent to C No H adjacent to C 2H adjacent to C 2H adjacent to C 6H adjacent to C

No of Hydrogen

2H adjacent to C 3H adjacent to C 2H adjacent to C

4

Coupling constant J (Hz) 31.01

Hydrogen abundance %H 5.5

Type of carbon -COO-

6

-

8.2

-

1

13.73

1.4

-C≡C-

4

15.13

5.5

C-O

6

36.52

8.2

-

5

14.44

6.8

-

41

28.86

56.2

6

13.41

8.2

Type of compound

Chemical shift, δ (ppm) 174.24

Type of splitting

129.75

Doublet

Sp carbon of alkayne

77.22

Triplet

51.41

Singlet

29.7

Multiplet

14.1

Singlet

-

methoxy carbons of esters methylene carbons of fatty acid methyl esters terminal carbons of methyl -

-

-

-

ester carbonyl carbon olefinic carbons

Singlet

-


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Energy & Fuels

Table 8: Characteristics of 1H and 13C NMR chemical shifts of CB100 Type of proton

Type of compound

-CH=CH-

olefinic protons

-CH3COO-CH

methoxy protons of methyl ester bis-allylic proton αmethylene protons of ester αmethylene protons of the double bond βmethylene of ester Methylene protons of long fatty acid chain terminal methyl protons

(-C=C-CH2C=C-) -CH2-COOMe

-CH2-C=C-

CH2-CCO2Me -(CH2)n-

(C-CH3)

Chemical shift (ppm) -

Type of splitting

SpinSpin splitting -

No of Hydrogen

Hydrogen abundance %H -

Type of carbon

Type of compound

-

Coupling constant J (Hz) -

-COO-

No H adjacent to C

3

-

11.5

-

ester carbonyl carbon olefinic carbons

3.7

Singlet

-

-

-

-

-

-

-C≡C-

2.3

Triplet

2H adjacent to C

2

15.03

7.7

C-O

-

-

-

-

-

-

-

1.63

Pentet

2

29.35

7.7

-

1.27

Triplet

4H adjacent to C 2H adjacent to C

16

24.21

61.5

0.89

Triplet

3

14.12

11.5

-

2H adjacent to C

Chemical shift (ppm) 174.3

Type of splitting

129.73

Doublet

Sp carbon of alkayne methoxy carbons of esters

77.23

Triplet

51.4

Singlet

29.59

Multiplet

14.08

Singlet

-

methylene carbons of fatty acid methyl esters terminal carbons of methyl -

-

-

Singlet

-

-


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From the NMR spectroscopy of both biodiesels we can predict the major physicochemical properties of those biodiesels that can measure the quality and sustainability to be used in diesel engine of those produced biodiesels. The characteristic peaks of olefinic proton, bis-allylic proton, terminal methyl protons from 1H NMR spectra of PB100 indicate the presence of monounsaturated and polyunsaturated fatty acid in that biodiesel. Meanwhile, the peaks of α and β- methylene protons of ester and methylene protons of long fatty acid chain represent the saturated fatty acid which have greater influence on C16:0 and C18:0 saturated fatty acid in the biodiesel. However, for CB100 biodiesel only the peak for terminal methyl protons was found and there were no peaks of olefinic and bis-allylic protons, which indicates a very few unsaturated fatty acids in that biodiesel. CB100 biodiesel had peaks for α and β- methylene protons of ester and methylene protons of long fatty acid chain which indicate the presence of more saturated fatty acid than unsaturated fatty acid in CB100 biodiesel. The cetane number of biodiesel increases with the increase in chain length and saturation level. As, CB100 has more saturated fatty acid it has higher cetane number than PB100, which in turn exhibit less NOx emissions for high cetane number. Moreover, with the increasing chain length and decreasing unsaturation the calorific value increases and that is why the calorific value of CB100 is higher than PB100, which is also responsible for less fuel consumption. Low temperature properties (CP, PP and CFPP) and kinematic viscosity of biodiesel also depend upon the saturation and unsaturation. With increasing unsaturation, the melting point and viscosity decrease and although PB100 has high unsaturation, it has bad cold flow properties and high viscosity than CB100 because of having high individual saturated fatty acid of C16:0 and C18:0. Moreover, oxidation stability increases with increased saturated fatty acid because they have the high resistant to oxidation. As, CB100 had higher saturated fatty acid it has higher oxidation stability than PB100.


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Energy & Fuels

Meanwhile, from13C NMR spectra the peaks of olefinic and terminal methyl carbon for both of the biodiesels ensure the presence of unsaturation in them 49-51. Based on the NMR spectra (both 1H and

13

C), we can conclude that both the biodiesels were

successfully obtained from their respective feedstocks, as indicated by the results of monitoring transesterification progress and conversion rate from feedstock to biodiesel methyl esters. Moreover, their physicochemical properties obtained from NMR spectra are also comparable with the experimental results. These results also confirm the quality and purity of produced biodiesels, which show similarity with the previous studies mentioned above. 6.5.3. Carbon residue analysis Carbon residue analysis of the biodiesels and pure diesel was performed based on the oxygen bomb calorimeter test for determining heat of combustion of fuels. The fuels placed in a crucible were burned in a metal chamber which was placed in a well-insulated water chamber. The heat produced from burning fuels was transferred to the water. The products of combustion inside the bomb calorimeter test were only CO2 and water by reacting with the oxygen. The CO2 left the samples as it is a gas and only water could be incorporated with the residue contents. After combustion was finished, the residues were heated at 60° C for 1h to remove the water from the residues. Then, the carbon residues of biodiesels were weighted and their images were captured. Figures 13 (a),(b) and (c)show the photographs of carbon residues in the crucible after burning P. pinnata, C. nucifera biodiesels and pure diesel, respectively. P. pinnata biodiesel formed less amount of carbon residue than pure diesel but C. nucifera biodiesel showed the lowest carbon residue formation among all investigated fuels, which could be due to the complete combustion of C. nucifera biodiesel than pure diesel and other biodiesels. Pure diesel produced the highest


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carbon residue because of incomplete combustion, which, in turn generating more fuel residues in the exhaust and increasing the emission level. Table 9 shows the weight and percentage of carbon residue produced from the burning of biodiesels and pure diesel. Among all the biodiesels, C. nucifera formed the lowest amount of carbon residue after burning, whereas pure diesel formed the highest amount. This result verifies that biodiesel is cleaner and safer to use as fuel in diesel engines.


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Energy & Fuels

(a)

(b)

(c) Fig. 13: Carbon residue in crucible after burning (photograph) (a) P. pinnata, (b) C. nucifera biodiesels, and (c) diesel


Energy & Fuels

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Table 9: Weight and percentage of carbon residue of biodiesels and pure diesel after burning

Weight of biodiesel used for burning (g) Weight of carbon residue after burning (g) Percentage of carbon residue (% m/m)

CB100 0.5617

PB100 0.5163

Diesel 0.5414

0.0003

0.0007

0.001

0.053

0.136

0.185

7. Conclusions In this study, the improvement in biodiesel properties was mainly discussed and their relationships were verified with the FAME composition, FT-IR and NMR spectroscopy analysis results. Those results ensured the quality and sustainability for applications in unmodified diesel engines. Prior to application, biodiesel must possess similar or, in certain cases, better properties than pure diesel. If the production of biodiesels can be sufficiently increased worldwide, then they can be commercially used as alternatives to diesel. Meanwhile, biodiesels can reduce the harmful effects of using fossil fuels but they have limitations of high production cost, energy efficiency variation, and various socio-economic conditions for the production of different biodiesel types from different feedstocks. Therefore, determining the production capability of biodiesels from various edible and non-edible feedstocks and comparing the properties of produced methyl ester by using varied and new analytical parameters are crucial, which was the motivation of this study. The main obtained results of this study are summarized as follows: C. nucifera biodiesels and its biodiesel–diesel blends exhibited the highest improvement in kinematic viscosity and density. Biodiesel blends showed higher oxidation stability 44 ACS Paragon Plus Environment

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Energy & Fuels

than diesel. 5% and 10% C. nucifera biodiesel–diesel blends exhibited the highest oxidation stability. P. pinnata, 20% and 30% diesel–biodiesel blends exhibited the highest oxidation stability. P. pinnata biodiesel exhibited the highest flash point among other fuels. In 5%, 10%, and 20% diesel–biodiesel blends, C. nucifera showed the highest flash point. Biodiesels exhibited lower heating values than pure diesel. C. nucifera biodiesel and its blends showed higher heating values than P. pinnata biodiesel blends. C. nucifera biodiesel blends had the highest consistency with diesel CFPP value. C. nucifera biodiesel and its blends presented the lowest carbon and highest oxygen content whereas P. pinnata biodiesel showed the opposite. C. nucifera biodiesel and their blends demonstrated better combustion characteristics, which are attributed to complete combustion, and reduced CO and HC emissions. Moreover, C. nucifera biodiesel showed the lowest carbon residue formation (0.053%) after burning. FAME composition, FT-IR and NMR spectroscopy results revealed the relation of them with biodiesel properties. C. nucifera biodiesel had the better physicochemical properties than P. pinnata biodiesel according to those results from analysis and also had the similarity with the experimental results. FT-IR analysis results depicted the quality of C. nucifera biodiesel for use in diesel engine because of its high ester content and similar functional groups to those of pure diesel and highest transmittance rate.


Energy & Fuels

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1

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H and 13C NMR results confirmed the successful conversion of triglyceride feedstock to

the corresponding methyl esters as well as the purity and quality of the produced biodiesels.C. nucifera biodiesel exhibited the highest conversion (98.7%) to biodiesel. 8. Acknowledgement The authors would like to acknowledge University of Malaya for financial support through High Impact Research grant UM.C/HIR/MOHE/ENG/60. References 1. Rahman, S. M. A.; Masjuki, H. H.; Kalam, M. A.; Abedin, M. J.; Sanjid, A.; Sajjad, H., Production of palm and Calophyllum inophyllum based biodiesel and investigation of blend performance and exhaust emission in an unmodified diesel engine at high idling conditions. Energy Conversion and Management 2013, 76, (0), 362-367. 2. Basha, S. A.; Raja Gopal, K., A review of the effects of catalyst and additive on biodiesel production, performance, combustion and emission characteristics. Renewable and Sustainable Energy Reviews 2012, 16, (1), 711-717. 3. Jayed, M. H.; Masjuki, H. H.; Kalam, M. A.; Mahlia, T. M. I.; Husnawan, M.; Liaquat, A. M., Prospects of dedicated biodiesel engine vehicles in Malaysia and Indonesia. Renewable and Sustainable Energy Reviews 2011, 15, (1), 220-235. 4. Atabani, A.; Badruddin, I. A.; Badarudin, A.; Khayoon, M.; Triwahyono, S., Recent scenario and technologies to utilize non-edible oils for biodiesel production. Renewable and Sustainable Energy Reviews 2014, 37, 840-851. 5. Hoekman, S. K.; Robbins, C., Review of the effects of biodiesel on NOx emissions. Fuel Processing Technology 2012, 96, 237-249. 6. Barabás, I.; Todoruţ, I.-A., Biodiesel quality, standards and properties. Biodiesel-Quality, Emissions and By-Products 2011, 3-28. 7. Tariq, M.; Ali, S.; Ahmad, F.; Ahmad, M.; Zafar, M.; Khalid, N.; Khan, M. A., Identification, FT-IR, NMR (1H and 13C) and GC/MS studies of fatty acid methyl esters in biodiesel from rocket seed oil. Fuel Processing Technology 2011, 92, (3), 336-341. 8. khan, T. M. Y.; Atabani, A. E.; Badruddin, I. A.; Badarudin, A.; Khayoon, M. S.; Triwahyono, S., Recent scenario and technologies to utilize non-edible oils for biodiesel production. Renewable and Sustainable Energy Reviews 2014, 37, (0), 840-851. 9. Basumatary, S.; Deka, D., Identification of fatty acid methyl esters in biodiesel from Pithecellobium monadelphum seed oil. Der Chemica Sinica 2012, 3, (6), 1384-1393. 10. Atabani, A. E.; Silitonga, A. S.; Badruddin, I. A.; Mahlia, T. M. I.; Masjuki, H. H.; Mekhilef, S., A comprehensive review on biodiesel as an alternative energy resource and its characteristics. Renewable and Sustainable Energy Reviews 2012, 16, (4), 2070-2093.


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