Author's Accepted Manuscript

Agro-industrial acidic oil as a renewablefeedstock for biodiesel production using(1R)-(-)-camphor-10-sulfonic acid

Adeeb Hayyan, Mohd Ali Hashim, MaanHayyan

PII: S0009-2509(14)00160-2DOI: http://dx.doi.org/10.1016/j.ces.2014.03.031Reference: CES11593

To appear in: Chemical Engineering Science

Received date: 6 July 2013Revised date: 20 January 2014Accepted date: 12 March 2014

Cite this article as: Adeeb Hayyan, Mohd Ali Hashim, Maan Hayyan, Agro-industrial acidic oil as a renewable feedstock for biodiesel production using(1R)-(-)-camphor-10-sulfonic acid, Chemical Engineering Science, http://dx.doi.org/10.1016/j.ces.2014.03.031

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1

Agro-industrial acidic oil as a renewable feedstock for biodiesel production using (1R)-(-)-camphor-10-sulfonic acid

Adeeb Hayyana,b*, Mohd Ali Hashima,b, Maan Hayyanb,c

aDepartment of Chemical Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia bUniversity of Malaya Centre for Ionic Liquids (UMCiL), University of Malaya, Kuala Lumpur 50603, Malaysia

cDepartment of Civil Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia

*Email: adeeb.hayyan@yahoo.com, Phone: +6-012-3002949, Fax: +6- 03-79675311.

Abstract

A mixture of low grade industrial oils such as acidic crude palm oil (ACPO) and sludge palm oil (SPO) was used for biodiesel

production. A novel organic acid such as (1R)-(-)-Camphor-10-sulfonic acid (10-CSA) was introduced as a catalyst for esterification

reaction. 10-CSA shows high activity as a catalyst in the reduction of free fatty acid (FFA) and high conversion of fatty acid methyl

ester (FAME). The effects of reaction temperature, reaction time and molar ratio on FFA reduction and FAME conversion were

studied. The FFA content was reduced from 8% to less than 1% using optimum conditions. The final product (biodiesel fuel) produced

from treated oils (ACPO and SPO) meets international biodiesel standards such as EN 14214 and ASTM D6751. This is the first time

10-CSA has been introduced as a catalyst for esterification reaction. This catalyst can treat a wide range of acidic raw materials for

biodiesel production. 10-CSA is a promising catalyst and can be used for various chemical reactions.

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Keywords: Acidic crude palm oil; biodiesel; esterification; sludge palm oil; (1R)-(-)-Camphor-10-sulfonic acid.

1. Introduction

The sustainability of agro-industrial feedstocks for biodiesel production is the main drawback in the commercialization of biodiesel

fuel. Therefore, abundant feedstock must be industrially available for biodiesel production. Many attempts have been made using

different types of low grade oils with high acidity to produce biodiesel fuel, such as industrial low grade palm oil (Hayyan et al.,

2013a; Hayyan et al., 2013b), acidic coconut oil (Nakpong and Wootthikanokkhan, 2010), palm oil fatty distillate (Chongkhong et al.,

2007), acidic oils extracted from seeds such as tobacco or rubber seeds (Veljkovic et al., 2006; Ramadhas et al., 2004), and waste oils

such as waste cooking oils (Canakci et al., 2007), waste tallow or waste animal fats (Canakci and van Gerpen, 2001). Sludge palm oil

(SPO) was used as a renewable feedstock in the preparation of biodiesel fuel (Hayyan et al., 2010a). SPO is an attractive feedstock

with which to produce biodiesel fuel because SPO is usually generated from palm oil mills as a by-product of milling processing. SPO

is an industrial low grade oil which usually contains high FFA content (Hayyan et al., 2011a). Recently, Hayyan et al., (2011b) used

acidic crude palm oil as an industrial feedstock for biodiesel production. Acidic crude palm oil (ACPO) is a low grade oil that is

usually rejected from palm oil refineries due to high free fatty acid (FFA) content of over 5%. SPO and ACPO are low grade oils that

usually contain high FFA content. Usually, SPO has FFA content higher than that of ACPO. The FFA content of any raw material

proposed for biodiesel production should be as low as possible (Freedman et al., 1984; Canakci et al., 2007; Ding et al., 2012). The

acceptable limit of FFA content for transesterification reaction was reported to be 1% or 2% (Hayyan et al., 2013b; Hayyan et al.,

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2011a). However, the mixing of ACPO with SPO as potential raw materials for biodiesel production has not yet been studied. The

mixture of these two industrial raw materials can reduce the cost of biodiesel production. Reduction of the FFA content using

esterification reaction is essential before transesterification reaction (Canakci and van Gerpen, 2001). Common homogenous acids

used for the esterification reaction are trifluoromethanesulfonic acid (Hayyan et al., 2013a), sulfuric acid, p-toulenesulfonic acid

(PTSA) (Di Serio et al., 2008), ethanesulfonic acid (Hayyan et al., 2011b) and methanesulfonic acid (Hayyan et al., 2012).

Recently, ionic liquids (ILs) were applied for the esterification of crude palm oil (CPO) (Man et al., 2013). Deep eutectic solvent

(DES) have also been applied at the upstream and downstream stages of biodiesel production (Hayyan et al., 2013c; Hayyan et al.,

2010b). Many studies applied lipase enzyme as a biological catalyst in the esterification and transesterification reactions (Kuan et al.,

2013). Common heterogeneous acids used in biodiesel production are ferric sulfate (Mengyu et al., 2009), glycerol-based carbon

catalyst (Prabhavathi Devi et al., 2009), and cation-exchange resins (Feng et al., 2010). However, there is no reported study on the

application of (1R)-(-)-camphor-10-sulfonic acid (10-CSA) for the reduction of FFA in a mixture of ACPO and SPO.10-CSA is an

organic hygroscopic acid formed in white powder and a relatively stable acid compared to acids in liquid form. Therefore, this study

aims to investigate the catalyst activity of 10-CSA, as well as to find the optimum conditions of other operating conditions such as

reaction time, molar ratio, and reaction temperature. The final product was characterized and compared according to ASTM 6751 and

EN 14214.

2. Methods

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2.1. Materials and chemicals

ACPO and SPO were acquired from a local mill in the state of Selangor in Malaysia. Methanol and potassium hydroxide (KOH)

pellets all of laboratory grades were purchased from R&M Chemicals (Malaysia). (1R)-(-)-camphor-10-sulfonic acid (C10H16O4S) was

purchased from Merck Sdn Bhd, Malaysia.

2.2. Methodology

Fatty acid profile and some physical properties of ACPO mixed with SPO was studied and reported. Single factor optimization was

used for design of experiments. The targeted FFA content in this study was fixed at 1%. A mixture of ACPO and SPO was heated in

an oven at a temperature 70oC for 2-3 h. The preheated oils were then transferred into a batch chemical reactor with reflux condenser

for the pre-treatment reaction using 10-CSA catalyst, after which transesterification reaction using KOH was carried out. In the

transesterification reaction, fixed conditions were used, such as 1% KOH to treated oil, 10:1 methanol to treated oil, 60oC reaction

temperature and 60 min reaction time. After validation of optimum conditions the catalyst recycling process was studied to investigate

the catalytic activity of 10-CSA. The recycling process was done by separation of used catalyst and methanol for the next experiment

and to treat the FFA content in fresh acidic oil. The recycling was done without addition of any new fresh catalyst. After alkaline

transesterification reaction, the mixture of oil, excess methanol and glycerol was evaporated using rotary evaporator. The mixture of

crude biodiesel and glycerol was separated in a separating funnel. After separation, the upper material consisted of fatty acid methyl

ester (FAME), while the lower layer contained the crude glycerol. The upper phase (crude biodiesel) was washed with hot water in

order to remove the traces of alkaline catalyst, soap and the free glycerol.

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2.3. Analytical analysis

The fatty acid compositions of the ACPO mixed with SPO were determined using Agilent Technologies 7890A gas chromatograph

equipped with 5975C mass spectrometer; the capillary column was DB-wax 122–7032. Helium was used as carrier gas with a flow

rate of 1 ml/min, measured at 50 °C; the run time was 35 min. Ester content was analyzed using GC/FID (Perkin Elmer Clarus 500),

split-splitless mode of injector, capillary column-polyethylene glycol wax phase, isotherm oven at 250 oC. The characteristics of

ACPO mixed with SPO were determined according to the Malaysian Palm Oil Board Test Methods (Kuntom et al., 2005) and

according to the American Oil Chemist’s Society (AOCS) official method Ca 5a-40 commercial fats and oils (AOCS, 1997).

3. Results and discussion

3.1. Characterization of ACPO mixed with SPO ACPO and SPO separately were used as raw materials for biodiesel production (Hayyan et al., 2011b; Hayyan et al., 2013a). The

current study introduced a mixture of ACPO and SPO as raw material to produce biodiesel. In the mixture of ACPO and SPO the

percentage of SPO was very low compared to ACPO. A small portion of SPO such as 0.20-0.30 wt% (SPO to ACPO) was sufficient

to increase the ACPO from 4.8% to 8-9% due to high FFA content of SPO (e.g. 20.39%). Table 1 shows the fatty acid compositions of

ACPO mixed with SPO. The physical properties of ACPO mixed with SPO are close to ACPO properties. The high concentration of

FFA content indicates that the oil is non-edible. The peroxide value of ACPO and SPO is high compared to other types of industrial

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oils due to long storage time. These two oils have a high content of moisture and impurities. These types of oils are industrially

available, and are therefore cheap compared to other types of oils such as waste cooking oil from restaurants.

3.2. Effect of 10-CSA dosage

The effect of 10-CSA on the reduction of FFA content in ACPO is illustrated in Figure1. The acid has a good catalytic activity,

rapidly reducing the FFA from 8% to 1.38% and 1.02% using 0.75wt% and 1wt% of 10-CSA to oil. Figure 1 also shows that the

optimum catalyst dosage is 1.5%, and at this point, FFA can be reduced to 0.8% while the FFA conversion was 90%. In fact, the FFA

can be reduced to 0.6% with 92.5% conversion possible with 2% catalyst. The target of this study is to give an overview of the effect

of catalyst dosage on the FFA reduction. Thus, it is very important to select the dosage of catalyst based on the low catalyst

consumption. Therefore, 1.5% was selected as the optimum dosage of catalyst for the treatment process. Hayyan et al., (2012) found

1% of methanesulfonic acid to ACPO to be the optimum catalysts dosage in the esterification reaction. A phosphonium-based deep

eutectic catalyst was recently applied in the treatment of low grade palm oil; a study by Hayyan et al. (2013c) also found 1% to be the

optimum dosage of catalyst. 10-CSA shows high catalytic activity almost similar to methanesulfonic acid and phosphonium-based

deep eutectic catalyst in the treatment of oils with 8%-10% FFA content.

3.3. Effect of molar ratio

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Theoretically, methylation requires one mole of methanol for each mole of FFA (Ding et al., 2012). Practically, more than 1 mole is

needed for an esterification reaction for FFA reduction in acidic oils such as ACPO and SPO. Figure 2 shows the effect of molar ratio

on the FFA conversion and reduction. As illustrated by Figure 2, different runs were conducted using different molar ratios (methanol

to ACPO mixed with SPO). The molar ratio was optimized within the range of 2:1 to 14:1. FFA to FAME conversion was almost

constant at high loading of methanol (10:1-15:1). Figure 2 shows that 10-CSA has very high catalytic activity even at low loading of

methanol such as 2:1. At this low molar ratio the FFA content was decreased from 8% to 3.63%. Nevertheless, the FFA content

reduced from 8% to 1.23% using 8:1, which is still higher than 1%. A value of 8:1 was not sufficient to reduce the FFA content to

below 1%, while 10:1 showed a better result. The FFA conversion to FAME using 10:1 was 87.50%. Therefore, the 10:1 molar ratio

was selected as the optimum ratio for the treatment of high FFA content in ACPO mixed with SPO. This molar ratio was selected by

many studies in the pre-treatment of a wide range of acidic oils (Hayyan et al., 2010a; Hayyan et al., 2011b).

3.4. Effect of reaction temperature

The reaction temperature was optimized in the range of 40oC to 80oC as shown in Figure 3. This figure shows the effect of reaction

temperature on FFA conversion and reduction. The lowest temperature (40oC) reduced the FFA content from 8% to 4.80%, while a

reaction temperature of 50oC significantly reduced the FFA content to 2.88%. Alternatively, a higher reaction temperature such as

80oC decreased the FFA content to 2.25%. A minimum reaction temperature is required mainly to save energy during reaction and to

ensure the treated oil can be transesterified. Thus, 60oC seems to be a suitable reaction temperature in the treatment of ACPO mixed

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with SPO. According to the results 60oC can also be used on an industrial scale to save energy and reduce the evaporation of

methanol. A reaction temperature of 60oC was used and reported as the optimum temperature by many studies in the esterification

reaction (Hayyan et al., 2010a; Hayyan et al., 2011a).

3.5. Effect of reaction time

Insufficient reaction time leads to a decrease in the conversion rate of products (FAME) which consequently increases the cost of pre-

treatment processing. Figure 4 shows the effect of reaction time on the FFA reduction and conversion. As shown in Figure 4, the FFA

content decreased with an increase of reaction time. It was observed that the FFA content remains higher than the limit in the range of

10-30 min. In this range, no significant reduction in the FFA content or the FFA conversion to biodiesel was seen. On the other hand,

at 40 min of reaction time, the FFA content reduced significantly to less than 1%. Therefore, 40 min of reaction time is adequate to

drive the reaction towards completion.

3.6. Validation study, recycling and trasesterification reaction

The optimum conditions for the pre-treatment process were 1.5 wt% dosage of 10-CSA to oil, 10:1 molar ratio, 60 oC temperature,

and reaction time of 40 min. It is to be noted that the application of acidic catalysts in biodiesel production is still limited due to safety

issues and the high cost of acidic catalysts such as 10-CSA. This organic acid in powder form is safer than acids in liquid form.

Therefore, it can be recommended for use in other acidic reactions. Figure 5 shows the conversion of FFA to FAME at different

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catalyst recycle runs. In this study, 10-CSA was recycled and its activity was studied using the verified optimum conditions. The

catalyst was recycled for six consecutive runs without adding a new amount of catalyst. Table 2 shows the fatty acid profile of the

produced biodiesel, while Table 3 reports the characterization of biodiesel produced from ACPO mixed with SPO and according to

EN 14214 and ASTM D6751, this biodiesel meets both standard specifications.

4. Conclusion

This study shows that a mixture of ACPO and SPO is a viable agro-industrial feedstock for biodiesel production. The FFA content

was reduced from 8% to less than 1% using 1.5% wt% dosage of 10-CSA to oil, 10:1 molar ratio, 60 oC temperature, and reaction

time of 40 min. The produced biodiesel meets the international standard specifications of biodiesel fuel such as EN 14214 and ASTM

D6751. 10-CSA is a very active catalyst in the esterification of high FFA; therefore, it can be used to treat a wide range of acidic oils.

Acknowledgments

The authors would like express their thanks to the University of Malaya HIR-MOHE (D000003-16001), Centre for Ionic Liquids

(UMCiL) and the Bright Sparks Program at the University of Malaya for their support of this research. The authors would like to

express their thanks to Khor Gui Qing for her help in the experimental work.

References

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List of Figures:

Fig.1. Effect of 10-CSA dosageon the FFA reduction and conversion Fig.2. Effect of methanol ratio on the FFA reduction and conversion Fig.3. Effect of reaction tempratureon the FFA reduction and conversion Fig.4. Effect of reaction timeon the FFA reduction and conversion Fig.5. FFA conversion to FAME at different 10-CSA catalyst recycle runs

Table 1

Fatty acid composition of ACPO mixed with SPO

Fatty acids Structure Type of fatty acid Fatty acids wt%

Lauric acid C12:0 Saturated 0.38± 0.03Myristic acid C14:0 Saturated 1.03± 0.04 Palmitic acid C16:0 Saturated 44.88± 1.82 Palmitoleic C16:1 Unsaturated 0.38± 0.03

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Stearic acid C18:0 Saturated 3.90± 0.40 Oleic acid C18:1 Unsaturated 39.80± 1.87 Linoleic acid C18:2 Unsaturated 9.07± 1.00 Alpha-Linolenic acid C18:3 Unsaturated 0.24± 0.02 Arachidic acid C20:0 Saturated 0.32± 0.06

Table 2 Fatty acid composition of produced biodiesel

Fatty acids Structure Type of fatty acid Fatty acids

wt% Lauric acid methyl ester C12:0 Saturated 0.34± 0.02Myristic acid methyl ester C14:0 Saturated 1.40± 0.04 Palmitic acid methyl ester C16:0 Saturated 44.73± 1.94 Palmitoleic methyl ester C16:1 Unsaturated 0.37± 0.02 Stearic acid methyl ester C18:0 Saturated 3.95± 0.50 Oleic acid methyl ester C18:1 Unsaturated 39.52± 2.57 Linoleic acid methyl ester C18:2 Unsaturated 9.10± 1.00 Alpha-Linolenic methyl ester C18:3 Unsaturated 0.25± 0.02 Arachidic acid methyl ester C20:0 Saturated 0.34± 0.07

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Table 3: Specifications of produced biodiesel fuel

Properties Biodiesel from

ACPO mixed with SPO

EN 14214 ASTM D6751 Test

Method Limits Test

MethodLimits

Ester content 96% (mol mol−1) EN 14103 96.5 % (mol

mol−1) min

- -

Monoacylglycerol content

0.06% (mol mol−1)

EN 14105 0.80 % (mol

mol−1) max

- -

Diacylglycerols content

0.01% (mol mol−1)

EN 14105 0.20 % (mol

mol−1) max

- -

Triacylglycerols content

<0.01% (mol mol−1)

EN 14105 0.20 % (mol

mol−1) max

- -

Free glycerol content

<0.01% (mol mol−1)

EN 14105 0.02 % (mol

mol−1) max

ASTM D 6584

0.020 wt% max

Total glycerol content

0.05% (mol mol−1)

EN 14105 0.25 % (mol

mol−1) max

ASTM D 6584

0.240 wt % max

15

Water content 444 mg kg−1 EN ISO 12937

500 mg kg−1 max

ASTM D 2709

0.050 % (v/v) max

K content 1 mg kg−1max

EN 14108

5.0 mg kg−1max

UOP 391

5.0 mg kg−1max

P content 7.4 mg kg−1 max EN 14107 10.0 mg kg−1 max

ASTM D 4951

0.001 wt% max

Density (15 ◦C) 880 kgm−3 EN ISO 3675

860–900

kgm−3

- -

Flash point 183.0◦C EN ISO 3679

120 ◦C min

ASTM D 93

130 ◦C min

Cloud point 16◦C - - ASTM D 2500

Not specified

Sulphated ash <0.005 wt% ISO 3987 0.02 % (mol

mol−1) max

ASTM D 874

0.020 wt% max

Total contamination

0.008 mg kg−1 EN 12662 24 mg kg−1 max

- -

Iodine value 50.22 g I2·100 g−1 EN 14111 120 g I2·100

g−1 max

- -

Copper Strip Corrosion (3 hours at 50◦C)

Class 1

EN ISO 2160

Class 1 rating

ASTM D130

No. 3 max

16

Fig.1. Effect of 10-CSA dosageon the FFA reduction and conversion

0

20

40

60

80

100

0123456789

0 0.5 1 1.5 2 2.5 3 3.5 4

Con

vers

ion%

FFA

%

Dosage of 10-CSA (wt%)

FFA% Limit of FFA% Conv. of FFA to FAME

17

Fig.2. Effect of methanol ratio on the FFA reduction and conversion

0

20

40

60

80

100

0

1

2

3

4

5

6

7

8

9

0 2 4 6 8 10 12 14 16

Con

vers

ion%

FFA

%

Molar Ratio

FFA% Limit of FFA% Conv.% of FFA to FAME

18

Fig.3. Effect of reaction tempratureon the FFA reduction and conversion

0

20

40

60

80

100

0

1

2

3

4

5

6

7

8

9

0 10 20 30 40 50 60 70 80 90

Con

vers

ion%

FFA

%

Temperature oC

FFA% Limit of FFA% Conv.% of FFA to FAME

19

0

20

40

60

80

100

0

1

2

3

4

5

6

7

8

9

0 10 20 30 40 50 60 70

Con

vers

ion%

FFA

%

Reaction Time min

FFA% Limit of FFA% conv.% of FFA to FAME

20

Fig.4.Effect of reaction time on the FFA reduction and conversion

Fig.5. FFA Conversion to FAME at different 10-CSA catalyst recycle runs

0

10

20

30

40

50

60

70

80

90

1 2 3 4 5 6

Recycle runs 

Con

vers

ion

of F

FA

to F

AM

E (%

)

21

Research highlights of this study are: - A mixture of ACPO and SPO was introduced as a potential feedstock to produce biodiesel. - (1R)-(-)-camphor-10-sulfonic acid was used as a new catalyst for esterification. - The produced biodiesel meets the international standards of biodiesel.

(1R)

)-(-)-ca

Trans

ampho

Es

Alkalinesesterifi

r-10-su

Acidicsterifica

e ication

ulfonic

c ation

22

+ +

c acid

Biodies

sel

+

+

Biodiesel

Alkaline Transesterification

+(1R)-(-)-camphor-10-sulfonic acid

Acidic Esterification

Graphical Abstract (for review)