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Chemical Engineering and Processing 48 (2009) 1152–1156

Contents lists available at ScienceDirect

Chemical Engineering and Processing:Process Intensification

journa l homepage: www.e lsev ier .com/ locate /cep

iodiesel production from rapeseed deodorizer distillate in aacked column reactor

un Liu ∗, Ling Wangollege of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, PR China

r t i c l e i n f o

rticle history:eceived 30 December 2008eceived in revised form 31 March 2009

a b s t r a c t

In this study, a technical method investigating biodiesel production in a column reactor packed withcation exchange resin from rapeseed oil deodorizer distillate (RODD) was addressed. The results showedthat D002 cation exchange resin presented more efficiently catalytic activity than 002CR and 732 resins

ccepted 3 April 2009vailable online 10 April 2009

eywords:iodieselation exchange resin

in a packed column reactor. Biodiesel yield achieved over 96% under the optimal conditions: D002 resincatalyst dosage 18 wt.% (based on oil weight), oil to methanol molar ratio 1:9, reaction temperature 60 ◦C,and reaction time 4 h. When the packed resin catalyst was recovered, biodiesel yield was over 88% after10 repeated batch cycles (40 h). The comparison of biodiesel production in a packed column reactorand catalyzed by traditional sulfuric acid from RODD was also studied. It was concluded that biodiesel

umn r

apeseed oil deodorizer distillateacked column reactor

synthesis in a packed col

. Introduction

Fatty acid methyl ester (FAME or biodiesel) originating fromegetable oils and animal fats has received considerable atten-ion in recent years as a green and alternative fuel [1–2]. However,iodiesel has currently not been commercialized all over the worldecause of the high cost of feedstock oil [3]. One alternative wayo reduce the cost of biodiesel production is to employ wasteils such as cheap deodorizer distillates available from the refin-ng vegetable oils [4–5]. Due to the presence of considerable freeatty acids (FFAs) in such feedstock, alkaline homogeneous cat-lyzed process is not recommended. Because a large amount ofoap byproduct is formed during the reaction, basic alkaline pro-ess creates serious problem of product separation and ultimatelyowers the yield substantially [6–7]. Although homogeneous acidatalyzed process can be employed to produce biodiesel, this pro-ess is operated at high temperature and gives rise to seriousnvironmental and corrosion problems. In addition, the homoge-eous acid catalyst is difficult to be recycled as a result of highost production [8]. Enzymatic catalyzed process can overcomehese problems produced by based alkali and acid catalyzed pro-esses, but it has not been industrialized because of the high cost

f enzyme, low reaction rate and the operation instability [9–10]. Aatalyst-free production method such as supercritical alcohol haslso been proposed, but it requires high temperature (>300 ◦C) andigh pressure (>20 MPa), which not only needs expensive equip-

∗ Corresponding author. Tel.: +86 27 87792214; fax: +86 27 87792213.E-mail address: liuyunprivate@sina.com (Y. Liu).

255-2701/$ – see front matter © 2009 Elsevier B.V. All rights reserved.oi:10.1016/j.cep.2009.04.001

eactor would be a potential way for biodiesel production from RODD.© 2009 Elsevier B.V. All rights reserved.

ment investment, but also has security risks during the operation[11].

Biodiesel synthesis by heterogeneous solid catalyzed processhas recently attracted considerable attention because it offers sig-nificant advantages in eliminating separation, corrosion, toxicityand environmental problems [12–14]. The ion exchange resin withsulfonic acid group (–SO3H) as a heterogeneous catalyst has beenused to produce biodiesel in recent years, and a few papers havestudied the utility of ion exchange resin for biodiesel production[15–16]. Vicente et al. [17] utilized ion exchange resins (anionicAmberlyst A26 and A27 and cationic Amberlyst 15, Rohm and HaasCo., Philadelphia, PA) for the transesterification of sunflower oiland methanol, but the biodiesel yield was quite low. Although themake-up structure of Amberlyst 15 resin is similar to D002, theactivation energy calculated from a traditional Arrhenius plot is76.9 kJ mol−1 for Amberlyst 15 and 51.58 kJ mol−1 for D002 resin,which implies that the resin D002 is more suitable for conversion oilinto esters as heterogeneous catalyst. Shibasaki-Kitakawa et al. [18]reported the transesterification reaction of triolein with ethanolusing various ion exchange resin catalysts to produce ethyl oleate asa biodiesel, but biodiesel yield was only about 80% under the opti-mal conditions. To our knowledge, utilization of cation exchangeresin catalysts for biodiesel production from deodorizer distillatewith high content of FFAs has not been explored in detail so far.

In this paper, a new technical method using a column reactor

packed with cation exchange resin was employed to investigate thebiodiesel synthesis from rapeseed oil deodorizer distillate (RODD).Three different type cation exchange resins (D002, 002CR and 732)were used to evaluate their catalytic activities for biodiesel prepara-tion. Effects of several crucial variables were also addressed, such as

Y. Liu, L. Wang / Chemical Engineering an

Table 1Physicochemical properties of RODD feedstock (mean ± std, n = 3).

Indexes Value

Moisture (wt.%) 0.05 ± 0.001Free fatty acid (wt.%) 48.80 ± 1.46Acid value (AV) (mg-KOH/g-oil) 97.61 ± 1.87

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Saponification value (mg-KOH/g-oil) 155.60 ± 1.65Ester value (mg-KOH/g-oil)) 68.01 ± 1.09Triglycerides (wt.%) 32.91 ± 0.76Total glycerol (wt.%) 3.72 ± 0.05

eaction temperature from 40 to 80 ◦C, molar ratio of oil/methanolrom 1:3 to 1:15, reaction time from 2 to 6 h, and cation exchangeesin catalyst dosage varying from 10 to 26 wt.% (based on oileight) packed in the column. The operating stability of the resin

atalyst after recovery was examined, and the comparison of theiodiesel synthesis in a column reactor and catalyzed by sulfuriccid from RODD was also presented.

. Materials and methods

.1. Materials

RODD was produced by Yiyue Factory of Oils and Fats in Jinzhou,ubei Province of China. Major physicochemical properties of theODD feedstock were listed in Table 1.

Cation exchange resins D002, 002CR and 732 used as catalystsere from the Chemical Factory of Tianjin University, China. Theajor physical properties of the three cation exchange resins were

iven in Table 2.Before catalyzed reaction, the resins should be pretreated. The

xperimental resin was firstly immersed into 5% HCl–ethanol mix-ure solvent for 30 min, and eluted with absolute ethanol till theH of the eluting solvent was neutral, and then dried in an oven at0 ◦C for 2 h.

Methanol (A.R. grade) with 99.5% purity and sodium sulfate (A.R.rade) with 95% purity were from Tianjin Siyou Chemical Factory,ianjin, China. Concentration sulfuric acid (A.R. grade) with 98.2%urity was from Hangzhou Reagent Chemical Factory, Hangzhou,hina. Standard FAME of 99% chromatographically purity, such asethyl tridecanoate, methyl myristate, methyl palmitate, methyl

tearate, methyl oleate, methyl linoleate, and methyl linolenate

ere input from Sigma–Aldrich Co. (St. Louis, MO, USA).

.2. Packed column reactor and operating procedures

Fig. 1 showed the experimental rig of the packed column reactor.

ig. 1. Experimental equipment of the packed column reactor. The experimentaletup consisted of glass column reactor (1), water-jacket (2), pump (3), tank (4),hermostat water bath (5), circulation (6), TYGON tube (7), and sample acceptor (8).

d Processing 48 (2009) 1152–1156 1153

The water-jacketed glass column (Shenshi Chemical Co., Wuhan,China) with an internal diameter of 11 mm and height of 30 cmwas vertically placed. The column was packed with cation exchangeresin. The RODD and methanol mixture solution was put into thesolvent tank and supplied to the bottom of the column at a constantflow rate of 1 mL/min using a BT00-300M peristaltic pump (KejianPeristaltic Pump Co., Ltd., Changzhou, China). The column reactortemperature was controlled by a thermostat water bath to keep thetemperature around 40–80 ◦C with an error of ±2 ◦C.

In our study, substrate flow rate was 1 mL/min and operatingparameters (packed catalyst dosage, reaction time, temperature,oil/methanol molar ratio) were varied to investigate the influenceon biodiesel yield. Conversion reaction in the packed column reac-tor included esterification of free fatty acid and transesterificationof triglyceride, and esterification was the major reaction in theprocessing of the biodiesel production. After the completion ofreaction, the effluent solution from the top of the column was col-lected. The collected fraction was centrifuged and the supernatantwas conducted to determine the content of FAME in product usinggas chromatography (GC). According to the BF3/MeOH methoddescribed by Igarashi et al. [19], the feedstock oil was converted intomethyl esters completely and determined by GC. Biodiesel yield wasthe sum of FAME by transesterification and esterification reactionand calculated by the following equation:

Biodiesel yield (%) = FAMEproduct × Weightproduct (g)FAMEraw × Weightraw (g)

× 100 (1)

where FAMEproduct is the content of FAME in fraction product, %;FAMEraw is the content of FAME when feedstock oil was convertedinto methyl esters completely according to BF3/MeOH method, %;Weightproduct and Weightraw are the weight of fraction product andfeedstock oil, respectively, g.

2.3. GC determination of FAME

The content of FAME in product was analyzed by a GC-9790gas chromatography (Fuli Analytical Instrument Co. Ltd., Wen-lin, China). Its column is an Agilent INNOWAX capillary column(30 m × 0.25 mm i.d. × 0.25 �m, J&W Scientific, Folsom, CA, USA).Initial column temperature was 200 ◦C and kept it for 2 min, thenwas raised to 235 ◦C at the rate of 3 ◦C/min and maintained thistemperature for 1 min. The temperature of the injector and theflame ionization detector (FID) was 240 and 280 ◦C, respectively.The retention times of standard FAME for methyl tridecanoate,methyl myristate, methyl palmitate, methyl stearate, methyl oleate,methyl linoleate and methyl linolenate were 3.12, 5.46, 11.64, 15.81,16.24, 17.23 and 18.82 min, respectively. The average error for FAMEdetermination was less than 0.5%. The content of FAME were quanti-tatively determined using the concentration of methyl tridecanoate(C13:0, internal standard) and other standard FAME. All reporteddata was collected in triplicate, and the statistical analysis was per-formed using SAS 9.0 software (SAS Institute Inc., Cary, NC, USA).Analytical data were expressed as mean ± std.

3. Results and discussions

3.1. Screening of cation exchange resin catalyst

Cation exchange resins D002, 002CR and 732 were used to eval-uate their catalytic activity in order to choose the optimal resincatalyst for biodiesel production in our study. Fig. 2 showed the

effect of three different cation exchange resin catalysts on biodieselyield.

It could be seen that cation exchange resin D002 was moreactive, achieving biodiesel yield of 93.7 ± 1.12%, compared with43.8 ± 1.06% and 73.6 ± 1.04% for resin 002CR and resin 732, respec-

1154 Y. Liu, L. Wang / Chemical Engineering and Processing 48 (2009) 1152–1156

Table 2Major physical properties of three different cation exchange resins.

Properties D002 002CR 732

Make-up structure Macro-pore polystyrene Gel polystyrene Gel polystyreneCross-linking density (%) 32 38 35 ± 1Particle size (mm) 0.05 1.25 1.02Apparent density (g/dm3) 1.24–1.30 1.18–1.28 1.24–1.28Ion-exchange capacity (mmol/g) ≥4.0 5.0 4.5

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3

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Table 4Effect of oil/methanol molar ratio on biodiesel yield (mean ± std,n = 3).

Oil/methanol molar ratio Biodiesel yield (%)

1:3 79.14 ± 1.251:6 92.91 ± 1.161:9 96.85 ± 0.731:12 95.77 ± 0.251:15 95.12 ± 1.02

ig. 2. Effect of resin catalyst type on biodiesel yield. Conditions: feedstock amount0 g, substrate flow rate 1 mL/min, reaction temperature 60 ◦C, reaction time 4 h, aolar ratio of oil/methanol 1:8, and dosage of packed resin catalyst 15 wt.%.

ively. The huge difference in catalytic performance of the threeation exchange resin catalysts was expected to be closely relatedo the different make-up structure of the catalyst samples (seeable 2). The resin D002 is macro-pore cation exchange resin, whilehe resins 002CR and 732 are gel cation exchange resin in the pro-ess of reaction. It implied that macro-pore cation exchange resins suitable for biodiesel production.

Since the cation exchange resin D002 showed the best catalyticerformance, it was used as catalyst in our experiments.

.2. Effect of amount of packed resin catalyst

The effect of amount of packed resin catalyst on biodiesel yieldas presented in Table 3.

It is well known that the presence of the catalyst increases theeaction rate of biodiesel production. In Table 3, when the packedmount of catalyst increased from 10 to 18 wt.% biodiesel yieldncreased gradually from 88.46 ± 1.09% to 96.96 ± 0.74%. However,here was slight decrease with the amount of packed resin increas-ng from 18 to 26 wt.%. This can be explained as a mixing effectetween reactant, product and resin solid catalyst. Although the

nitial reaction rate increased with the increase of resin catalyst, theoss amount of reactant (oil) and product (methyl ester) increased

ecause excessive resin will absorb more oil and methyl ester.herefore it was concluded that the 18 wt.% dosage of the resin wasptimal packed amount in our study.

Table 3Effect of amount of packed resin on biodiesel yield(mean ± std, n = 3).

Resin amount (%) Biodiesel yield (%)

10 88.46 ± 1.0914 95.61 ± 0.6718 96.96 ± 0.7422 96.14 ± 0.2426 96.17 ± 0.21

Conditions: feedstock amount 50 g, substrate flow rate1 mL/min, reaction temperature 60 ◦C, reaction time 4 h anda molar ratio of oil/methanol 1:9.

Conditions: feedstock amount 50 g, substrate flow rate 1 mL/min,reaction temperature 60 ◦C, reaction time 4 h and dosage of packedresin catalyst 18 wt.%.

3.3. Effect of the molar ratio of oil/methanol

The molar ratio of oil to methanol is another important param-eter affecting biodiesel yield. In fact, appropriately excessivemethanol could increase the reaction rate and promote the com-pletion of reaction. Table 4 illustrated biodiesel yield as a functionof oil/methanol molar ratios.

As shown in Table 4, biodiesel yield increased with the increas-ing of the oil/methanol molar ratio from 1:3 to 1:9. The maximumbiodiesel yield of 96.85 ± 0.73% was obtained at the oil/methanolmolar ratio of 1:9. The molar ratio beyond 1:9 had little influ-ence on biodiesel yield (from 96.85 ± 0.73% to 95.12 ± 1.02%). Inour preliminary work, increasing with the amount of methanolup to 25 moles per molar oil, the esters yield is lower than 90%(the value is 88.71%). While the molar ratio of oil/methanol isbelow 1:3, the esters yield is lower than 79.14%. Therefore, theamount range of the substrate from 6% to 14% (molar concentra-tion, or molar ratio of oil/methanol from 1:6 to 1:15) is efficientlyconverted into esters (more than 90%) by a given portion of thecatalyst, and the most suitable amount of substrate is 10% (molarconcentration, or 1:9 molar ratio of oil to methanol). The reasonwas that excessive methanol could interfere with the mass transferin the packed column by driving the combination of ester prod-uct and glycerol into monoglycerides, which increases the viscosityof mixture in the packed column. Therefore, 1:9 molar ratio of oilto methanol was optimal for biodiesel synthesis in a packed col-umn.

3.4. Effect of reaction temperature

As we know, reaction temperature is another important param-eter affecting biodiesel yield. In this case, a reaction varying thetemperature from 40 to 80 ◦C was employed and the same settingswere used for other operating parameters. The results obtainedwere shown in Table 5.

Shown in Table 5, when the temperature was increased from40 to 60 ◦C, the biodiesel yield increased from 82.14 ± 1.17% to96.41 ± 0.25%. This could be explained by the fact that high temper-ature speeds up the reaction rate and increases mass transfer in the

◦

packed column. However, beyond 65 C, methanol was vaporizedrapidly and formed a large number of bubbles inhibiting the masstransfer in the packed column, causing the decrease of biodieselyield. This is the reason that the biodiesel yield slightly decreasedfrom 96.41 ± 0.25% to 94.92 ± 1.43% with the reaction temperature

Y. Liu, L. Wang / Chemical Engineering and Processing 48 (2009) 1152–1156 1155

Table 5Effect of reaction temperature on biodiesel yield (mean ± std,n = 3).

Temperature (◦C) Biodiesel yield (%)

40 82.14 ± 1.1750 91.36 ± 1.0260 96.41 ± 0.2570 96.03 ± 0.4480 94.92 ± 1.43

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between production in a packed column reactor and catalyzedby sulfuric acid. But the major advantage of biodiesel synthe-sized in a packed column reactor was that no washing step isrequired for biodiesel further purification. In addition, the solid

Conditions: feedstock amount 50 g, substrate flow rate1 mL/min, reaction time 4 h, a molar ratio of oil/methanol 1:9and dosage of packed resin catalyst 18 wt.%.

urther increasing from 60 to 80 ◦C. Therefore, 60 ◦C was the optimaleaction temperature in our work.

.5. Effect of reaction time

To examine the effect of reaction time on biodiesel yield, a reac-ion at varying reaction time from 2 to 6 h was carried out and theesults were presented in Table 6.

Table 6 illustrated that biodiesel yield increased gradually from7.97 ± 1.07% to 96.13 ± 1.14% in the range of reaction periods fromto 6 h. However, a reaction time longer than 4 h did not change

he biodiesel yield (about 96%) any more because a relative equilib-ium conversion was achieved in the packed column reactor. Thus,he favorable reaction time was 4 h for our work. If the reactionime is further prolonged to 15 h in one reaction, the resin D002an be maintaining 84% catalytic activity of its original activity.hat is to say, in one reaction the ester yield decrease from 96%o 80.64% when resin D002 is used 15 h successively. Beyond 15 h,he esters conversion decreased rapidly because the moisture andil absorbed by the resin would hinder the conversion reaction.

.6. Operation stability of packed column reactor

As we know, if the esters conversion ratio is more than 85%,he catalyst resin can be used in the next batch. Therefore, the cat-lyst resin is not necessarily regenerated after each batch of therocess. However, because the RODD feedstock contained high con-ent of FFA (48.8 ± 1.46 wt.%), esterification was the major reactionn the processing of the biodiesel production. Esterification is aeversible reaction. The product H2O influences both the conver-ion and reverse reaction rate. It was reported that the conversionropped from 95.6% to 52.5% when the water content increasedrom 0% to 1.5% [20]. The drop of conversion ratio with moistureontent was caused by kinetic influence rather than the equilib-ium influence. In our preliminary study, the product H2O wasll absorbed by the resin D002 packed in the column reactor,

hich would greatly deactivate the catalytic activity of the resin002 by forming water layer on the hydrophilic surface prevent-

ng the access of the relatively hydrophobic substrate. In addition,he resin D002 also absorbs about 3 wt.% RODD oil. Therefore inrder to keep the good performance of the packed column reac-

Table 6Effect of reaction time on biodiesel yield (mean ± std, n = 3).

Reaction time (h) Biodiesel yield (%)

2 87.97 ± 1.073 93.74 ± 1.264 95.81 ± 1.055 96.09 ± 1.226 96.13 ± 1.14

Conditions: feedstock amount 50 g, substrate flow rate1 mL/min, reaction temperature 60 ◦C, a molar ratio ofoil/methanol 1:9 and dosage of packed resin catalyst 18 wt.%.

Fig. 3. Effect of repeated cycles on biodiesel yield. Conditions: feedstock amount50 g, substrate flow rate 1 mL/min, reaction temperature 60 ◦C, reaction time 4 h, amolar ratio of oil/methanol 1:9 and dosage of packed resin catalyst 18 wt.%.

tor, cation exchange resin D002 must be regenerated to dehydrateand de-oil for the next batch reaction. The regeneration proceduresof cation exchange resin D002 was carried out as the followingsteps, the packed column reactor was firstly defatted by elutingwith ether, and then dehydrated by eluting with absolute alco-hol.

Fig. 3 indicated that the resin D002 catalyst in the packed col-umn maintained efficient activity even after being reused for 10repeated cycles (40 h) and the biodiesel yield was still over 88%(from 96.45 ± 1.01% to 88.12 ± 1.67%).

It was found that the resin D002 still retained about 91.3% ofits original activity after ten cycles of successive reuse. Thus thecolumn reactor packed with the resin D002 has excellently oper-ational stability. This was because that the resin D002 has beendemonstrated to afford a high density of active –SO3H sites, whichis physically robust and little leaching of –SO3H group occurredduring the successive use.

Therefore, biodiesel synthesized in a packed column reactordescribed in this paper can be conducted in another type of reactor,e.g. in a batch reactor and present a potential alternative methodfor further industrial scale.

3.7. Comparison of resin catalyst and sulfuric acid catalyst

Fig. 4 showed comparison of biodiesel synthesized in a packedcolumn reactor with that catalyzed by sulfuric acid from RODD.

It could be seen that the same biodiesel yield (96.8 ± 1.05%)

Fig. 4. Comparison of biodiesel synthesized in a packed column and catalyzed bysulfuric acid. Conditions of sulfuric acid catalyzed: temperature 60 ◦C, molar ratio ofoil/methanol was 1:12, agitation rate 200 rpm, concentration of acid catalyst 5 wt.%,and reaction time 4 h; Conditions in a packed column reactor: feedstock amount50 g, substrate flow rate 1 mL/min, reaction temperature 60 ◦C, reaction time 4 h, amolar ratio of oil/methanol 1:9 and dosage of packed resin catalyst 18 wt.%.

1156 Y. Liu, L. Wang / Chemical Engineering and Processing 48 (2009) 1152–1156

Table 7Part of the properties of biodiesel synthesis (mean ± std, n = 3).

Indexes Feedstock Sulfuric acid catalyzeda In a packed columnb DIN EN 14214c

Acid value (mg-KOH/g) 97.60 ± 1.86 1.31 ± 0.01 1.12 ± 0.01 0.5 maxGravity density (g/mL) (15 ◦C) 0.972 ± 0.07 0.901 ± 0.11 0.899 ± 0.07 860–900Content of triglycerides (%) 32.91 ± 1.02 13.41 ± 0.02 12.73 ± 0.02 –Viscosity (×10−6 m2/s) (40 ◦C) 35.62 ± 1.03 11.85 ± 0.04 10.51 ± 0.02 3.5–5.0

a Conditions of sulfuric acid catalyzed: feedstock amount 50 g, temperature 60 ◦C, molar ratio of oil/methanol was 1:12, agitation rate 200 rpm, concentration of acid catalyst5

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wt.%, and reaction time 4 h.b Conditions in a packed column: feedstock amount 50 g, substrate flow rate 1 mL

osage of packed resin catalyst 18 wt.%.c DIN EN 14214 stands for the standard of biodiesel in European.

esin catalyst packed in the column reactor can be regenerated andepeated to use as result of reducing the cost of biodiesel productionreatly.

Properties of biodiesel synthesized in a packed column reac-or and catalyzed by sulfuric acid was also evaluated and listed inable 7.

From Table 7, a great decrease of acid value and triglyceriden biodiesel product was obtained. The drop of acid value wasrom 97.6 mg-KOH/g-oil in RODD to below 1.4 mg-KOH/g-oil iniodiesel product, and the triglyceride content was decreased from2.91 wt.% in RODD to 12.73 wt.% in biodiesel product. However,

ts relatively high acid value and kinetic viscosity caused by highontent of triglyceride were still beyond the standard measured upy EN 14214. Thus, a further combined transesterification reactionhould be employed to convert triglycerides to methyl esters andurther to reduce the acid value.

. Conclusions

The present study clearly showed that cation exchange resin002 catalyst demonstrated higher activity than cation exchange

esin 002CR and 732 in packed column reactor. It showed highlyffective in converting high FFA-containing RODD to biodiesel byimultaneous esterification and transesterification. Under the opti-al conditions, biodiesel production from RODD with 48.80 wt.%

FA afforded the methyl ester yield of over 96%. The resin D002lso manifested very excellent operational stability and showedhe same efficient activity as conventional sulfuric acid catalyst foriodiesel production. From the analysis of properties of biodieselroduct, a further combined transesterification reaction should bemployed to reduce the acid value and the content of triglycerideselated to viscosity of biodiesel product by a packed column reac-or.

cknowledgements

The authors acknowledge the Analysis Center of Huazhong Uni-

ersity of Science and Technology (HUST) for the GC determinationnd its financial support from the Human Resource Departmentf HUST (0124170030) and Hubei Province Natural Science Foun-ation (2008CDB359), and authors thank Prof. Mingyue Ding anduandi Zhao for English spelling proofreading.

[

reaction temperature 60 ◦C, reaction time 4 h, a molar ratio of oil/methanol 1:9 and

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