ri

S.raninee

, Lo

s pr

lyst. In the rst step, acid catalyzed esterication reduced the high FFA content of SPO to less than 2%with the different dosages of PTSA. The optimum conditions for pretreatment process by esterication

lower price of petroleum fuel (Antolin et al., 2002). Usually, ediblevegetable oils, such as palm oil, soybean, rapeseed, corn, sesameand sunower, are the prevalent feedstocks for biodiesel produc-tion. The high value of edible vegetable oils as a food productmakes production of biodiesel fuel very challenging as the cost ofraw materials accounts for 6070% of the total production cost ofbiodiesel fuel (Krawczyk, 1996; Ma and Hanna, 1999). Therefore,

sludge palm oil (SPO) from palm oil industries. The SPO is a by-product of the milling process and its annual production reaches41 million tonnes (Hayyan et al., 2008). The current applicationsof the SPO are to use in the low-grade soap production and boilerfuels. Some developing countries import for further renery tomaking animal feed supplementary, non-food application, etc.The use of SPO can lower the cost of biodiesel production signi-cantly, which makes SPO a highly potential alternative feedstockfor biodiesel production. The SPO usually contains high amountsof free fatty acid (FFA) that cannot be converted to biodiesel usingan alkaline catalyzed process. A number of researchers have

* Corresponding author. Tel.: +60 3 61964571; fax: +60 3 61964442.

Bioresource Technology 101 (2010) 78047811

Contents lists availab

T

elsE-mail addresses: zahangir@iium.edu.my, zahangir@yahoo.com (Md.Z. Alam).Biodiesel production from abundant bio-sources has drawn theattention of the academic as well as the industrial community inrecent years (Hayyan et al., 2010). In many countries, biodiesel isreceiving an upsurge interest as an alternative and renewable en-ergy due to diminishing petroleum reserves, increasing fuel pricesand rising environmental concerns. Biodiesel can be made fromrenewable biological sources such as vegetable oils, animal fats,etc. The main merits of using biodiesel as engine fuel are reducingthe reliance on petroleum fuel and reducing air pollutant emis-sions from diesel engines (Ma and Hanna, 1999; Wang et al.,2000; Durn et al., 2005; Demirbas, 2009). However, in spite ofthe favorable impact, the economic aspect of biodiesel productionis still a barrier for its development, mainly due to the current

Many attempts have been made to produce biodiesel from non-edible plant oils such as mahua (Ghadge and Raheman, 2005),tobacco (Veljkovic et al., 2006), rubber seed oil (Ramadhas et al.,2005), waste oils such as waste cooking oils (Leung and Guo,2006), waste tallow (Bhatti et al., 2008) and animal fats (Canakciand van Gerpen, 2001) as cheap feedstocks for biodiesel produc-tion. The sustainability of these feedstocks is a major drawbackto their potential for commercialization due to the limited quantityof generation. Therefore, an abundant resource (feedstock) isessential to be economically and commercially feasible for biodie-sel production.

Malaysia, as one of the biggest palm oil producers and exportersin the world, is producing large amounts of low-grade oil such asAvailable online 11 June 2010

Keywords:BiodieselSludge palm oilFree fatty acidToluene-4-sulfonic monohydrate acidTransesterication

1. Introduction0960-8524/$ - see front matter 2010 Elsevier Ltd. Adoi:10.1016/j.biortech.2010.05.045were 0.75% (w/w) dosage of PTSA to SPO, 10:1 M ratio, 60 C temperature, 60 min reaction time and400 rpm stirrer speed. The highest yield of biodiesel after transesterication and purication processeswas 76.62% with 0.07% FFA and 96% ester content. The biodiesel produced was favorable as comparedto EN 14214 and ASTM 6751 standard. This study shows a potential exploitation of SPO as a new feed-stock for the production of biodiesel.

2010 Elsevier Ltd. All rights reserved.

exploring ways to reduce the cost of rawmaterial is the main inter-est in recent biodiesel research.Received in revised form 11 May 2010Accepted 17 May 2010

acid (PTSA) as an acid catalyst in different dosages in the presence of methanol to convert free fatty acid(FFA) to fatty acid methyl ester (FAME), followed by a transesterication process using an alkaline cata-Sludge palm oil as a renewable raw mateby two-step processes

Adeeb Hayyan a, Md. Zahangir Alam a,*, Mohamed E.Noor Irma Nazashida Mohd Hakimi b, Yosri Mohd SiaBioenvironmental Engineering Research Unit (BERU), Department of Biotechnology EngP.O. Box 10, Kuala Lumpur 50728, Malaysiab Processing and Engineering, R&D Center Downstream, Sime Darby Research Sdn Bhd

a r t i c l e i n f o

Article history:Received 3 March 2010

a b s t r a c t

In this study, biodiesel wa

Bioresource

journal homepage: www.ll rights reserved.al for biodiesel production

Mirghani a, Nassereldeen A. Kabbashi a,b, Shawaluddin Tahiruddin b

ring, Faculty of Engineering, International Islamic University Malaysia,

t 2664 Jalan Pulau Carey, 42960 Pulau Carey, Kuala Langat, Selangor, Malaysia

oduced from sludge palm oil (SPO) using tolune-4-sulfonic monohydrate

le at ScienceDirect

echnology

evier .com/locate /bior tech

worked with feedstocks that have elevated FFA content and theymentioned that the oil should not contain more than 1% FFA foralkaline catalyzed transesterication reaction (Freedman et al.,1984; Liu, 1994; Canakci and van Gerpen, 2003; Lu et al., 2009).

Due to high FFA content in SPO, the alkali catalyzed transesteri-cation to produce biodiesel gives low biodiesel yield because FFAreacts with alkali to form soap, resulting in serious emulsicationand separation problems (Canakci and van Gerpen, 2001; Demir-bas, 2009). To resolve this problem, an alternative process usingan acid catalyst has been proposed and used as a pretreatment stepin different studies (Freedman and Pryde, 1982; Liu, 1994; Canakciand van Gerpen, 2001; Naik et al., 2008). The most commonly pre-ferred acid catalysts are sulfuric acid, hydrochloric acid, sulfonicacid and organic sulfonic acid such as p-toluene sulfonic acid(PTSA) (Ma and Hanna, 1999). The PTSA showed the highest cata-lytic activity as compared to benzenesulfonic acid and sulfuric acid(Guan et al., 2009). Ferric sulfate as solid acid has been used in

other reaction variables such as molar ratio, reaction time, temper-ature and stirrer speed on esterication reaction; and to evaluatethe biodiesel quality to be produced after transesterication

2.2. Production of biodiesel from SPO by two-step catalyzed processes

The production of biodiesel from SPO was carried out by two-step catalyzed processes i.e. esterication and transestericationreactions followed by the separation and purication processes.First the SPO was preheated because it usually exists in a semisolidphase at room temperature (30 2 C). The SPO was melted in anoven at 80 C and the preheated SPO was then transferred intothe reactor for pretreatment of SPO using PTSA (esterication),followed by an alkaline catalyzed transesterication process. Thenal step was separation and purication of biodiesel obtainedfrom the two reactions. A complete ow diagram on the processesfor biodiesel production from SPO is shown in Fig. 1.

2.2.1. Pretreatment of SPO by esterication reaction using PTSAThe acid catalyst PTSA was added into the preheated SPO at

different dosages in the presence of methanol to reduce the free

A. Hayyan et al. / Bioresource Technology 101 (2010) 78047811 7805reaction.

2. Methods

2.1. Raw materials and chemicals

The sludge palm oil (SPO) was collected fromWest Oil Mill, Car-ey Island, Selangor, Malaysia and was stored at 4 C. Methyl alcoholanhydrous 99.8% commercial grade was purchased from Mallinck-rodt Chemicals, USA; laboratory grades of toluene-4-sulfonicmonohydrate acid (C7H8O3SH2O) 99%, potassium hydroxide(KOH) 85% and magnesium sulfate (MgSO4) were purchased fromMerck Sdn Bhd, Malaysia.

Dosage of PTSA

0.5%

0.75%

1.0%

1.5%

2.0%

Biodiesel by EP at 0.5%

Biodiesel by EP at 0.75%

Biodiesel by EP at 1%

Biodiesel by EP at 1.5%

Biodiesel by EP at 2%

Pre-esterification process (EP) esterication of waste cooking oil, and results show high activityand conversion of FFA to FAME compared to sulfuric acid (Wanget al., 2006). The main drawback of using solid acid or heteroge-neous acid is the high cost. Therefore, in order to produce highquality biodiesel with low-cost and safer operating conditions,PTSA was proposed in this study to treat the SPO by an esterica-tion process followed by a transesterication process using potas-sium hydroxide as an alkaline catalyst.

The objectives of this study were to investigate the potential ofSPO as a low-cost feedstock in biodiesel production; to study theeffect of dosage of PTSA as a strong organic monohydrate acid withFig. 1. A complete ow diagram of the esterication, transesterication, purfatty acid (FFA) of SPO by converting it into fatty acid methyl ester(FAME) (Fig. 1). A batch esterication process was carried outusing single factor optimization to study the effect of PTSA in thedosage range (0.2510% wt/wt), molar ratio of methanol to SPO(6:120:1), reaction temperature (4080 C), reaction time (30120 min) and stirrer speed (200800 rpm). The effects of thoseparameters on FFA content, yield of treated SPO and FFA to FAMEconversion were measured to evaluate the esterication process.

2.2.2. Alkaline catalyzed transesterication reactionThe treated SPO by acid catalyzed esterication was considered

as the pre-treated material for transesterication process (Fig. 1).The process conditions for transesterication reaction weremaintained to the molar ratio of methanol to SPO 10:1, reactiontemperature 60 C, reaction time 60 min, stirrer speed 400 rpmand 1% wt/wt KOH. All experiments were performed in 1.5 L ofbatch reactor with reux condenser and all parameters were con-trolled by digital controller (Sartorius Stedim Biotech Malaysia SdnBhd).

2.2.3. Separation and purication of biodiesel obtained from two-stepcatalyzed processes

In order to remove excess methanol in the biodiesel, the wetcrude biodiesel was dried under vacuum with a rotary evaporator.The product was allowed to cool and equilibrate which resulted inseparation into two layers in a separating funnel. After 24 h sepa-ration time, the upper phase consisted of biodiesel, while the lowerlayer contained the glycerol. Finally, the biodiesel was washed

Purified Biodiesel

Transesterification Separation and

Biodiesel by TEP (0.5%)

Biodiesel by TEP (0.75%)Biodiesel by TEP (1%)

Biodiesel by TEP (1.5%)

Biodiesel by TEP (2%)process (TEP) Purification

ication processes for biodiesel production from sludge palm oil (SPO).

were oleic, palmitic, linoleic and stearic acid. Saturated fatty acidsin SPO were 47.17 wt% while unsaturated fatty acids were52.83 wt%. According to Canakci and van Gerpen (2001), highersaturated fatty acids in oils give a higher cetane number and theoil is less prone to oxidation. Due to its high percentage of satu-rated fatty acids and free fatty acids, SPO exists in semisolid phaseor solid phase at room temperature (30 2 C). Hence SPO hashigher pour and cloud points as compared to normal crude palmoil.

3.2. Acid catalyzed esterication process for biodiesel production

Esterication process was used in order to pretreat the SPO byconverting the high content of FFA to FAME using an acid catalyst.The initial content of FFA of the SPO used in this study was 22.33%,which would not be favorable for biodiesel production as the studyby Canakci and Van Gerpen (2001) indicated that transesterica-tion reaction will not occur if the FFA content in oil is more than3%. Therefore, the limit of FFA was set to a maximum of 2% forall esterication experiments. The major factors affecting the ester-ication process were dosages of PTSA, molar ratio of methanol toSPO, reaction temperature, reaction time and stirrer speed.

3.2.1. Effect of PTSA dosageTo nd the FFA content in SPO at target level (

an acceptable yield of treated SPO and decrease the cost of the pre-treatment process.

3.2.2. Effect of molar ratioMolar ratio is one of the important factors affecting the conver-

sion of FFA to FAME, as well as the overall production cost of bio-diesel. The esterication process needs more methanol thantransesterication; however, in practice, the molar ratio shouldbe higher than that of the stoichiometric ratio (3:1) or (1:1) in or-der to drive the reaction towards completion (Ramadhas et al.,2005). In this study, the molar ratio of methanol to SPO was variedfrom 6:1 to 20:1. Fig. 3 shows the effect of the molar ratio on thereduction of the FFA content in SPO, yield of treated SPO and con-version of FFA to FAME. The yield of treated SPO slightly increasedwhen the molar ratio increased from 6:1 to 10:1, and no signicant

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A. Hayyan et al. / Bioresource Technology 101 (2010) 78047811 7807treated SPO, 0.75 wt% of PTSA gave the FFA content of 2%, the yieldwith 96% of treated SPO, and conversion of FFA to FAME was 90.9%.At lower PTSA dosage (0.250.5%), the residual FFA content is high-er (46%) than the limit of 2% which would not be favorable to theconversion of pre-treated SPO into biodiesel. The excessive dosageof PTSA did not show any improvement of biodiesel yield and con-version of FFA, as the reaction might take place at equilibrium. Inaddition, the low strength of the catalyst might not be sufcientto provide enough catalytic activity to convert triacylglycerols tomethyl ester.

It was reported that using 6.4 105 mol of PTSA as acid cata-lyst can decrease the FFA content in soybean oil from 20.5% to 1.1%and the yield obtained after reaction obtained was only 48% withthe reaction conditions of 12:1 M ratio, 180 C reaction tempera-ture, and 60 min reaction time (Di Serio et al., 2008). Guan et al.(2009) claimed that PTSA has a higher catalyst activity than otheracid catalysts such as benzenesulfonic acid and sulfuric acid, wherethe obtained yield was 97.1% using 4 wt% of PTSA in the presenceof dimethyl ether. In both studies, the consumption of PTSA andother reagents were high to obtain an acceptable yield as com-pared to the present study.

The economic feasibility of using PTSA has been calculated inorder to minimize the production cost. Catalyst consumption(CC) is a factor which plays an important and essential role inthe overall production cost of the biodiesel. The results of CC withdosage of catalyst and yield are shown in Table 3. The ndingsshowed that the high yield was achieved with a proportionally in-crease of catalyst dosage and CC at 0.75% and 7.81 mg/g, respec-

Dosage of PTSA, wt%

Fig. 2. Effect of dosages of PTSA on reduction of FFA content, yield of treated SPOand conversion of FFA to FAME.tively. After that, the yield was found to slightly increase withmaximum catalyst dosage (10%) and CC (110.1 mg/g), which indi-cates a higher production cost of biodiesel. It was found that7.8 mg of PTSA is required to produce 1 gm of treated SPO at0.75 wt% of PTSA, which consider a low amount of catalyst to give

Table 3Effect of dosages of PTSA on yield of treated SPO and catalyst consumption.

Dosage of catalyst (wt%) Yield (%) Catalyst consumption (mg/gm)

0 0 00.25 75.9 3.30.5 93.3 5.360.75 96 7.811 96.7 10.341.5 94 19.162 93 22.604 96 40.546 94.4 63.558 95 91.57

10 94.6 110.08change was observed with a higher molar ratio. An excess of meth-anol is used in order to obtain a higher yield but too large anamount of methanol would not be able to contribute to the reac-tion process due to the mass transfer limitation. On the other hand,a minimum of 10:1 M ratio was required to reduce the FFA contentof SPO from 22.33% to 2%, which is the limit of FFA for transesteri-cation reaction in this study. With an insufcient amount ofmethanol in the reaction, the reaction process tends to be slower,thus decreasing the amount of conversion. Therefore, 10:1 wasconsidered for the optimum ratio of methanol to SPO.

Di Serio et al. (2008) have used 12:1 M ratio to decrease the FFAcontent in soybean oil from 20.5% to 1.1% using PTSA as acid cata-lyst. Another study by Chongkhong et al. (2007) showed an 8:1 Mratio of methanol to palm fatty acid distillate with 1.8 wt% of sul-furic acid at 60 C and a retention time of 60 min. Veljkovic et al.(2006) found that the FFA content of tobacco seed oil was reducedfrom 17 wt% to less than 2 wt% using a molar ratio of 18:1 of meth-anol to oil.

3.2.3. Effect of reaction temperatureIn this study reaction temperature was varied from 40 to 80 C.

Fig. 4 presents the effect of reaction temperature on the FFA con-tent in SPO, yield of treated SPO and conversion of FFA to FAME.The results showed that the targeted FFA with high yield was ob-served at the reaction temperature of 60 C. High temperaturescould affect the reaction by increasing the kinetic energy duringthe process. Increased temperature gives energy to the moleculesto move faster; therefore, it is easier to break the carbon bond inthe glycerides with the help of alcohol and a catalyst during thereaction process. As temperature increases the kinetic energy inthe reaction process also increases and thus shortens the reactiontime. The temperatures of 40 and 50 C are considered as low tem-peratures and when a low reaction temperature was applied, the

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some of its methanol during reaction. At 60 C, a high yield of trea-

time is sufcient for the completion of esterication reaction,which gave 96% yield of treated SPO, 90.93% conversion of FFA toFAME and the FFA content decreased from 22.33% to 2%.

A study by Veljkovic et al. (2006) showed that esterication re-duced the FFA level from about 35% to less than 2% in 25 and50 min, with a molar ratio of 18:1 and 13:1, respectively. In thepresent study, FFA content was reduced from 22.33% to less than2% in 60120 min and 10:1 M ratio. Di Serio et al. (2008) reportedthat using 6.4 105 mol of PTSA as an acid catalyst can decreasethe FFA content in soybean oil from 20.5% to 1.1% and the yield ob-tained after reaction obtained was only 48%. The reaction conditionwas 12:1 M ratio, 180 C temperature, and 60 min reaction time.While the optimum reaction time was 60 min with the PTSA dos-

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7808 A. Hayyan et al. / Bioresource Technology 101 (2010) 78047811ted SPO (96%) was obtained, the FFA was reduced to 2%, and a90.93% conversion of FFA to FAME was achieved.

The ndings obtained are supported by Leung and Guo (2006).They found that temperatures higher than 50 C had a negative im-pact on the product yield for neat oil, but had a positive effect forwaste oil with higher viscosities. Guan et al. (2009) found that theyield of FAME reached 97.1% when the reaction was done at 80 C,using 4 wt% of PTSA in the presence of dimethyl ether with 2-hreaction time.

3.2.4. Effect of reaction timeIn order to complete the esterication reaction, sufcient con-

tact time must be provided. Fig. 5 shows the effect of reaction timeon the reduction of FFA content, yield of treated SPO and conver-sion of FFA to FAME. It was observed that the yield of treatedreaction did not fully completed. Hence, the results at 40 and 50 C,low yield of treated SPO, low conversion of FFA to FAME and highFFA content were obtained. On the other hand, results at 70 and80 C, a low yield of treated SPO was obtained because at highertemperatures more methanol evaporated and the reaction lost

0 20 40 60 80 100

Temperature, C

Fig. 4. Effect of reaction temperature on reduction of FFA content, yield of treatedSPO and conversion of FFA to FAME.SPO increased with an increase in reaction time as well as the con-version of FFA to FAME. After 30 min of reaction, the FFA contentwas 5.4%, which is higher than the limits of FFA for transesterica-tion reaction, whereas FFA content at 60 min up to 120 min wasless than 2% FFA. Therefore, in order to save the energy and to de-crease the cost of the pretreatment process, 60 min of reaction

very unstable condition in which some of methanol evaporates

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conv.% of FFA to FAME

Fig. 5. Effect of reaction time on reduction of FFA content, yield of treated SPOtreated SPO and conversion of FFA to FAME.and there is a lack of sufcient contact with the SPO during thereaction. In addition, high rates of revolution consume a lot of en-ergy, which would not be economic.

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Conv.% of FFA to FAMEage of 0.75% at reaction time, 60 C in order to obtain a high yieldof 96% which is double the results of the study by Di Serio et al.(2008).

3.2.5. Effect of stirrer speedIn order to achieve effective mass transfer between the reagents

and SPO during the esterication process, continuous mixing andsufcient reaction time have great consequence for a completereaction. An understanding of mixing effects on the kinetics ofthe reaction process is a valuable tool in the process scale-up anddesign. After adding the methanol and catalyst to the oil, stirringfor 510 min promotes a higher rate of conversion (Demirbas,2009).

Mixing intensity (stirrer rate) was investigated in the rangefrom 200 to 800 rpm. Fig. 6 shows the effect of stirrer speed onthe reduction of FFA content, yield of treated SPO and conversionof FFA to FAME. The results revealed that the stirrer rates of 200and 400 rpm were sufcient for the completion of estericationreaction and to decrease FFA content from 22.33% to 2%. However,the yield for 400 rpm was slightly higher than that for 200 rpm.Mixing signicantly affects the reaction rate; insufcient mixingcould lead to a very slow reaction rate, thus lowering the conver-sion value. Therefore, 400 rpm stirrer speed was selected as theoptimum stirrer speed in the pretreatment process of SPO. How-ever, too high a stirrer speed would negatively impact to the reac-tion as well. The results showed that increasing the stirrer speed to600 rpm, not only consumes more energy but also results in a low-er yield than that of 400 rpm. The conversion and FFA content afteresterication, however, were the same as with 400 rpm. The stirrerrate of 800 rpmwas not recommended because the FFA content in-creased above 2%, and both yields of treated SPO and conversion ofFFA to FAME decreased. It is believed that high mixing creates aFig. 6. Effect of stirrer speed on reduction of FFA content, yield of treated SPO andconversion of FFA to FAME.

ntent after transesterication reaction.

ions (max) PTSA treated puried biodiesel

0.5% 0.75% 1% 1.5% 2%

63.71 76.62 75.80 54 4510.66 13.16 11.43 17 14.667.84 9.78 13.19 27.77 44.4481 95 90 89 960.49 0.48 0.39 0.18 0.08

echnology 101 (2010) 78047811 7809Pretreatment process using a stirrer rate of 400 rpm was uti-lized by Yuan et al. (2008) in the pretreatment of waste rapeseedoil with high FFA to produce biodiesel. Lifka and Ondruschka(2004) have studied the PTSA as an acid catalyst and differentmethods of mixing using a magnetic stirrer, ultrasound and ultra-turrax. The study found that ultrasonic mixing was lowest in en-ergy costs.

3.3. Alkaline catalyzed transesterication process

The rst phase of the study was to reduce the FFA of SPO by anacid catalyzed esterication process. Different dosages of PTSA(0.252%) were applied with other process conditions to evaluatethe FFA conversion at less than 2% from its initial content of22.33% which is favorable to a further transesterication process.In the second phase, pre-treated SPO after esterication is consid-ered as the pre-treated material for the transesterication processwhere triglycerides are converted to FAME using an alkaline cata-lyst. All pre-treated SPO materials with the dosages of PTSA (0.5%,0.75%, 1%, 1.5% and 2%) were further transesteried into biodieselusing an alkaline catalyst under these conditions: molar ratio ofmethanol to SPO 10:1, reaction temperature 60 C, reaction time60 min, stirrer speed 400 rpm and 1% wt/wt KOH.

The biodiesel yield, catalyst consumption and properties ofpuried biodiesel as well as glycerol content after alkaline cata-lyzed transesterication (based on pre-treated SPO with differentPTSA dosages) are shown in Table 4. The results showed that eachpre-treated SPO by PTSA dosage was evaluated in the production ofbiodiesel with its yield and properties. It was observed that a sig-nicant effect of the dosage of PTSA in the esterication reactionwas found towards the biodiesel yield from the transesterication

Table 4Yield, catalyst consumption and properties of puried biodiesel as well as glycerol co

Parameters Test method Unit Specicat

Yield of biodiesel Eq. (1) % Yield of glycerol Eq. (1) % CC Eq. (3) mg/gm Ester content EN14103 %(mol mol1) 96.5Monoacylglycerol EN14105 %(mol mol1) 0.8Diacylglycerols EN14105 %(mol mol1) 0.2Triacylglycerols EN14105 %(mol mol1) 0.2Free glycerol EN14105 %(mol mol1) 0.02Total glycerol EN14105 %(mol mol1) 0.25Acid value EN14104 mg KOH g1 0.5FFA AOCS 1997 %

Monoglycerides content 0.06% (mol mol1) EN 14105

echncontained 47.17 wt% of saturated fatty acids. These saturated fattyacids give biodiesel fuel advantages in terms of a higher cetanenumber and better oxidation stability; in contrast, saturated fattyacids shows disadvantages such as the fuel having a higher cloudpoint and pour point. The higher cetane number in biodiesel fromSPO increases the ignition quality and efciency of combustion anddecreases engine deposits results in the less smoke, lower exhaustemissions and lower engine wear. Due to higher saturated fattyacids in biodiesel from SPO, the oxidation stability provides longage of using biodiesel fuel and nally improves fuel economy.However, higher saturated fatty acids in biodiesel from SPO havingthe disadvantages with the higher cloud point and pour point if itis used in cold weather. It is associated with some problems suchas not easily to start and transferring the fuel from tank to theengine.

Fatty acids composition of biodiesel from SPO is presented inTable 5. It was found that the fatty acids composition of SPO was

Diglycerides content 0.00% (mol mol1) EN 14105Triglycerides content

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Sludge palm oil as a renewable raw material for biodiesel production by two-step processesIntroductionMethodsRaw materials and chemicalsProduction of biodiesel from SPO by two-step catalyzed processesPretreatment of SPO by esterification reaction using PTSAAlkaline catalyzed transesterification reactionSeparation and purification of biodiesel obtained from two-step catalyzed processes

Analytical analysis

Results and discussionCharacteristics of SPOAcid catalyzed esterification process for biodiesel productionEffect of PTSA dosageEffect of molar ratioEffect of reaction temperatureEffect of reaction timeEffect of stirrer speed

Alkaline catalyzed transesterification processCharacteristics of biodiesel from SPO after transesterification with purification process

ConclusionsAcknowledgementsReferences