6. Weigh the product.
7. Add 5 ml acetone into the product sample to form the product sample as a
homogeneous phase.
8. Prepare a sample for GC analysis. This sample contains 1 g of product, 1 g of internal standard solution (0.2 g of heptadecanoic acid dissolved in 9.8 g of acetone) and 8 g acetone.
Composition analysis
The composition of product samples was analyzed by a gas chromatography (GC) equipped with flame-ionization detector (FID). The specification and the operating conditions of GC are listed as follows.
Model : VARIAN CP 3800 (the highest operating temperature : 723.15 K) Injector: 573.15 K
Oven: 435.15 K for 30 min －＞ 20 K / min 463.15 K for 4 min －＞ 25 K / min 513.15 K for 8 min
Detector: 573.15 K Carrier gas : Helium Flow rate : 1 ml / min
Split ratio : initial 100 for 5 min －＞ 20 for 41 min
Column : Select biodiesel for FAME, CP9080, Varian ( 30 m*0.32 mm ID, max.
temperature = 523.15 K) 3-1-5 GC calibration
The calibration curve of oleic acid to heptadecanoic acid (internal standard) is shown in Figure 3-2. The unreacted oleic acid was calculated from the calibration result and then the conversion of oleic acid was calculated from eq. (3-1).
0
where XA is the conversion of oleic aicd, NA is the number of moles of the unreacted oleic acid in the product stream per min, NA0 is the initial number of moles of oleic acid in the feed per min.
3-2 Results and discussion
The esterification of oleic acid with methanol is given by eq. (3-2),
Oleic acid + Methanol Methyl oleate +Water k1
k2
(3-2)
A B C D
where A is oleic acid, B is methanol, C is methyl oleate, and D is water. The constants of k1and k2are the rate constants of the forward and the backward reactions,
respectively. To enhance the reaction toward the methyl oleate formation, methanol is in large excess.
In the continuous reacting system, the residence time（τ）is calculated from eq. (3-3)
v0
where mix,at reaction condition is the density of mixture of oleic acid and methanol at
reaction condition, mix, at roomtemperatureand delivered pressure is the density of mixture of oleic acid and methanol measured by density meter. V is the volume of the reactor (subtracting the volume of stainless steel tailings packing), Winletis the mass flow rate of the feed, fsyringe pumpis the volumetric feeding rate of the syringe pump, v0is the total volumetric flow rate in the reactor under the experimental conditions. The density of feed stream (mix,at reaction condition ) was estimated from the density of the constituent components with neglecting the volume change of mixing. To calculate densities of the feed stream, the density of oleic acid was estimated from the
correlation as shown in Figure 3-3, while the density of methanol was calculated from NIST Chemistry Webbook (Table 3-2). The experimental results are reported in Table 3-3.
3-2-1 Feed composition effect
The feed composition effect is shown in Figure 3-4. The conversion of oleic acid increases with increasing B0* at the same residence time, except for the first two data points, where the residence times are sufficiently short. The equilibrium
conversion of oleic acid increases from 0.93 to 0.97 with B0* increasing from 2 to 5.
It is feasible for the methyl oleate formation as methanol is in large excess.
3-2-2 Temperature effect
The effect of temperature is illustrated in Figure 3-5. The graph shows that the reaction rate, conversion of oleic acid and equilibrium conversion increase with increasing the reaction temperature at fixed feed composition and pressure. Therefore, the esterification of oleic acid with methanol is an endothermic reaction.
3-2-3 The effect of phase of methanol
The effect of phase of methanol on the kinetic behavior of the esterification is also investigated. Since the critical conditions of methanol are 512.6 K and 80.9 bar, methanol at 533 K and 100 bar should exist at supercritical condition, whereas the other two reaction conditions are near critical condition of methanol. The equilibrium conversions are about 0.97 at different reaction temperatures, while Figure 3-5 shows that the reaction rate and the time to reach equilibrium conversion are substantially faster in supercritical condition of methanol. At the subcritical condition of methanol, it needs to take more than 1 hour to approach the equilibrium conversion. As a
consequence, it is favorable for the esterification of free fatty acid with supercritical methanol.
3-3 Correlation of kinetic data
The kinetic data were correlated with a power law model for the synthesis of
methyl oleate. The mass-balance equation with respect to oleic acid around the tubular reactor is given by eqs. (3-4) to (3-6).
Expressing the rate equation in terms of conversion of oleic acid ( XA) yields,
where r is the reaction rate of oleic acid,A is the residence time, k and1 k is2 the rate constants of the forward and the backward reactions,Kxis the equilibrium
concentration ratio, C is the concentration of the component i. Introducing eq. (3-6)i into eq. (3-4) and ntarctica the equation to obtain the following equation:
The rate constant k and equilibrium concentration ratio1 K were determined fromx the kinetic data correlation with eq. (3-7) by using MATLAB. The objective function of the data correlation is given by
where N is the number of data points. The correlated results are reported in Table 3-4.
The calculated results from the kinetic model at different temperatures and at different feed molar ratios are compared with experimental values in Figure 3-6 and Figure 3-7, respectively. The power law model correlated the kinetic data to the AAD no greater than 3 %. The rate constant of the forward reaction jumps five-fold from subcritical to supercritical states of methanol. The rate constants of the forward and the backward reactions are expressed in the Arrhenius form and plotted in Figure 3-8.
The rate constants of the forward and the backward reactions are expressed in terms of temperature in the supercritical and the subcritical regions, respectively, as given below.
The activation energies of the esterification in subcritical state of methanol are E0,f = 54.7 kJ mol-1and E0,r = 32.2 kJ mol-1,while the effective molar heat of reaction is about 22.5 kJ mol-1. The activation energies of the esterification in supcritical state are E0,f = 176.9 kJ mol-1and E0,r = 132.3 kJ mol-1,while the effective molar heat of reaction is about 44.6 kJ mol-1. It indicates that the esterification is an endothermic reaction from heat of reaction and the reaction rate in the supercritical state of methanol is much faster than in the subcritical state.
3-4 Transesterification of waste cooking oil (WCO) with methanol
The transesterification of oils with methanol and the esterification of fatty acids with methanol will be taking place simultaneously if the feedstock contains certain amount of FFA. To investigate the influence of feedstock in presence of FFA, refined sunflower oil and WCO were used as a reactant, respectively. Fig. 3-9 shows that the FAME yield is about 0.65 at= 4 min using the WCO as feedstock. It takes much longer time (= 40 min) to reach the same yield when refined sunflower oil was used as feedstock. The highest FAME yield was 0.90 at= 19 min. It is indicated that the presence of FFA can even enhance the production rate of FAME through the
non-catalytic reactions with supercritical methanol. Using this non-catalytic supercritical method, we do not need to remove FFA and water from the feedstock before entering the reactor. It allowed us to use low grade feedstock to produce FAME.
3-5 Conclusions
The kinetic behavior has been studied for the non-catalytic esterification of oleic
acid with methanol for biodiesel production. The experimental runs were conducted at temperatures from 493.15 K to 533.15 K and pressure of 100 bar under B0* (the molar ratios of methanol to oleic acid) from 2 to 5. It was found that the reaction rate increased with increasing reaction temperature and the equilibrium conversions increased from 0.93 to 0.97 by increasing B0* from 2 to 5 at 513.15 K and 100 bar.
The reaction rate and the time to reach the equilibrium conversion are much faster by using supercritical methanol. It is feasible to implement the esterification at
supercritical conditions of methanol. Additionally, the kinetic data were correlated well with a power law model and the kinetic parameters were also determined.
Table 3-1 Fatty acid compositions of vegetable oil samples (Goering et al., 1982)
Vegetable oil Fatty acid composition, % by weight 16:0
Palmitic
18:0 Stearic
20:0 Arachidic
22:0 Behenic
24:0 Lignoceric
18:1 Oleic
22:1 Erucic
18:2 Linoleic
18:3 Linolenic
Corn 11.67 1.85 0.24 0.00 0.00 25.16 0.00 60.60 0.48
Cottonseed 28.33 0.89 0.00 0.00 0.00 13.27 0.00 57.51 0.00
Crambe 2.07 0.70 2.09 0.80 1.12 18.86 58.51 9.00 6.85
Peanut 11.38 2.39 1.32 2.52 1.23 48.28 0.00 31.95 0.93
Rapeseed 3.49 0.85 0.00 0.00 0.00 64.40 0.00 22.30 8.23
Soybean 11.75 3.15 0.00 0.00 0.00 23.26 0.00 55.53 6.31
Sunflower 6.08 3.26 0.00 0.00 0.00 16.93 0.00 73.73 0.00
Table 3-2 The density of methanol at various temperatures and a fixed pressure (NIST Chemistry Webbook)
T (K) P (bar) Density (g. cm-3)
493 100 0.53350
513 100 0.44966
533 100 0.17070
Table 3-3 Experimental results of the esterification of oleic acid with methanol
T = 493K T = 513 K T = 533 K T = 513 K T =513 K
P = 100 bar P = 100 bar P = 100 bar P = 100 bar P = 100 bar
θB0*= 5 θB0*= 5 θB0*= 5 θB0*= 2 θB0*= 3
CA0= 1.4727*10-3mol/cm3 CA0= 1.3463*10-3
mol/cm3 CA0= 7.4788*10-4mol/cm3 CA0= 1.8918*10-3mol/cm3 CA0= 1.6677*10-3mol/cm3
XAe= 0.97 XAe= 0.97 XAe= 0.97 XAe= 0.93 XAe= 0.96
τ τ τ τ τ
( min )
XA
( min )
XA
( min )
XA
( min )
XA
( min )
XA
3.7 0.55 3.2 0.66 1.7 0.72 3.5 0.68 3.2 0.66
5.7 0.66 4.9 0.75 2.6 0.83 5.1 0.75 5.1 0.76
10.5 0.80 9.2 0.87 4.8 0.92 10.5 0.83 9.9 0.87
16.3 0.86 14.2 0.92 7.5 0.95 16.1 0.87 14.9 0.90
22.4 0.90 19.6 0.94 10.3 0.96 21.3 0.89 19.9 0.92
33.4 0.93 29.2 0.95 15.3 0.97 31.8 0.90 30.8 0.93
Table 3-4 Correlated results of the kinetic data of esterification of oleic acid with methanol
Figure 3-1 Schematic diagram of the experimental apparatus
1. Feeding bottles 6. Thermostatic air bath 11. Pressure regulator 2. Syringe pump 7. Reactor 12. Pressure release cylinder 3. HPLC pump 8. Temperature indicator 13. Sample collector
4. Three-way valve 9. Pressure indicator 14. Ice bath 5. Preheater 10. Needle valve
0 5 10 15 20 Concentration ratio ( Oleic acid / Internal Standard ) 0
5 10 15 20 25
Integralarearatio(Oleicacid/InternalStandard)
Y = 1.1426 X R2= 0.9999
Figure 3-2 GC calibration for oleic acid using heptadecanoic acid as an internal standard
280 300 320 340 360 380
Temperature ( K ) 0.84
0.85 0.86 0.87 0.88 0.89
Density(g/cm3)
Y = -0.0007 X + 1.0918
R = 0.99999
Figure 3-3 Correlation of oleic acid density with temperature
0 10 20 30 40
(min)
0 0.2 0.4 0.6 0.8 1
XA
B0*= 5
B0*= 3
B0*= 2Figure 3-4 Kinetic behavior of esterification of oleic acid with methanol at 513 K and 100 bar under different feed compositions
0 10 20 30 40
( min )
0 0.2 0.4 0.6 0.8 1
XA
493 K 513 K 533 K
Figure 3-5 Kinetic behavior of the esterification of oleic acid with methanol at = 5 and 100 bar under different reactionB0* temperatures
0 10 20 30 40
min 0 0.2 0.4 0.6 0.8 1
XA
533 K 513 K 493 K Calc.
Figure 3-6 Comparison of correlated results with experimental values at 100 bar and = 5 under different reaction temperaturesB0*
0 10 20 30 40
( min )0 0.2 0.4 0.6 0.8 1
XA
B0*= 5
B0*= 3
B0* = 2 Calc.Figure 3-7 Comparison of correlated results with experimental values at 513 K and 100 bar under different feed compositions
1.84 1.88 1.92 1.96 2 2.04
103 / T ( K-1)
0 2 4 6
lnk
k1
k2
Figure 3-8 Rate constants of forward and backward reactions at different temperatures
0 4 8 12 16 20
(min)
0.2 0.4 0.6 0.8 1
FAMEYield
T = 573 K P = 100 bar
B0*= 25
Figure 3-9 The supercritical transesterification of WCO with methanol at 573 K, 100 bar and = 25.B0*
Chapter 4 Conclusions
In the present study, the kinetic behavior of biodiesel production via either non-catalytic transesterification or non-catalytic esterification was investigated.
Several conclusions have been made which as follows.
For transesterification reaction
1. The kinetic experiments have been conducted for the transesterification of
sunflower oil with supercritical methanol by using CO2as a co-solvent. The ranges of operating conditions are θ (the molar ratios of methanol to triglyceride) fromB0 20 to 60, (the molar ratio of COE0 2to methanol) = 0.1, temperatures from 553 K to 593 K, and pressures from 100 bar to 250 bar.
2. The reaction rate increases with increasing temperature, but it is insensitive to pressure.
3. The presence of CO2didn’tenhance the reaction rate and increase the yield of FAME.
4. The FAME yield can reach as high as 70 % with θ = 25 andB0 = 0.1 inτ= 23E0 min at 593 K and 100 bar.
5. The kinetic data were correlated well with a power raw model and the kinetic parameters were also determined.
For esterification reaction
1. The kinetic experiments have been conducted for the esterification of oleic acid with methanol to produce biodiesel. The ranges of experimental conditions are
0*
B (the molar ratios of methanol to oleic acid) from 2 to 5, temperatures from 493 K to 533 K, and pressure at 100 bar.
2. The reaction rate increases with increasing reaction temperature and the
equilibrium conversion increases from 0.93 to 0.97 as B0* increasing from 2 to 5 at 513 K and 100 bar.
3. The reaction rate is significantly enhanced as the esterification was conducted at the supercritical condition of methanol. The supercritical process is applicable for
non-catalytic esterification for biodiesel production.
4. The kinetic data were correlated satisfactorily with a power law model and the kinetic parameters were then determined.
Nomenclature and units
AAD = average absolute deviations D
C B
A, , , = triglyceride, methanol, free fatty acid methyl esters, glycerol for
transesterification, respectively；oleic acid, methanol, methyl oleate, water for esterification, respectively
inlet
W = total mass flow rate of the feed（g min-1）
WFAME= total mass flow rate of FAME in the product stream（g min-1）
TG0
W = corresponding mass of triglyceride in the feed（g min-1）
= density of mixture（g cmmix -3） v0= volumetric flow rate ( cm3min-1)
Fi= molar flow rate of component i ( mol min-1)
0
θ = molar ratio of feed (methanol to triglyceride)B 0*
= molar ratio of feed (methanol to oleic acid)B 0
= molar ratio of feed (carbon dioxide to methanol)E TG0
C = corresponding concentration of triglyceride in the feed（kmol m-3） C = concentration of component i（kmol mi -3）
C = equilibrium concentration of component i（kmol mie -3） X = conversion of component ii
N = number of moles of component ii
N = number of data points
r = reaction rate of component i（kmol mi -3min-1or mol cm-3min-1） k = rate constant of forward reaction（m1 9kmol-3min-1or cm3mol-1min-1） k = rate constant of backward reaction（m2 9kmol-3min-1or cm3mol-1min-1） E0,f = activation energy of forward reaction（kJ mol-1）
E0,r= activation energy of backward reaction（kJ mol-1） R= gas constant（kJ mol-1K-1）
K = equilibrium concentration ratiox
V = volume of reactor（cm3）
T= temperature（K）
P= pressure（bar）
τ= residence time（min）
Subscripts
e = at equilibrium state f = forward reaction r= backward reaction i= component i
Superscripts
expt.= experimental value .
calc = calculated value Yield = the yield of FAME
References
Alenezi, R., Leeke, G. A., Winterbottom, J. W., Santos, R. C. D., Khan, A. R.,
“Esterification kinetics of free fatty acids with supercritical methanol for biodiesel production,”Energy Conversion and Management 51 (2010) 1055-1059.
Bertoldi, C., da Silva, C., Bernardon, J. P., Corazza, M. L., Filho, L. C., Oliveira, J. V., Corazza, F. C., “Continuous production of biodiesel from soybean oil in
supercritical ethanol and carbon dioxide as cosolvent,”Energy & Fuels 23 (2010) 5165-5172.
Boocock, D. G. B., Konar, S. K., Mao, V., Lee, C., Buligan, S., “Fast formationof high-purity methyl esters from vegetable oils,”JAOCS 75 (1998) 1167-1172.
Boocock, D. G. B., “Single-phase process for production of fatty acid methyl esters from mixtures of triglycerides and fatty acids,”Canadian Patent No.2,381,394, Feb.
22 (2001).
Bunyakiat, K., Makmee, S., Sawangkeaw, R., Ngamprasertsith, S., “Continuous production of biodiesel via transesterification from vegetable oils in supercritical methanol,”Energy & Fuels 20 (2006) 812-817.
Cerce, T., Peter, S., Weidner, E., “Biodiesel-transesterification of biodiesel oils with liquid catalysts: Thermodynamic properties of oil-methanol-amine mixtures,”Ind.
Eng. Chem. Res. 44 (2005) 9535-9541.
Chongkhong, S., Tongurai, C., Chetpattananaoadh, P., “Continuous esterification for biodiesel production from palm fatty acid distillate using economical process,”
Renewable Energy 34 (2009) 1059-1063.
Demirbas, A., “Biodiesel production from vegetable oils via catalytic and non-catalytic supercritical methanol transesterification methods,”Progress in Energy and
Combustion Science 31 (2005) 466-487.
Demirbas, A., “Biodiesel from sunflower oil in supercritical methanol with calcium oxide,”Energy Conversion and Management 48 (2007) 937-941.
Demirbas, A., “Comparsion of transesterification methods for production of biodiesel from vegetable oils and fats,”Energy Conversion and Management 49 (2008) 125-130.
D’Ippolito, S. A., Yori, J. C., Iturria, M. E., Pieck, C. L., Vera, C. R., “Analysis of a two-step, noncatalytic, supercritical biodiesel production process with heat
recovery,”Energy & Fuels 21 (2007) 339-346.
Fangrui, M., Milford, A. H., “Biodiesel production: A review,”Bioresource Technology 70 (1999) 1-15.
Freedman, B., Pryde, E. H., Mounts, T. L., “Variables affecting the yields of fatty esters from transesterified vegetable oils,”JAOCS 61 (1984) 1638-1643.
Freedman, B., Butterfield, R. O., Pryde, E. H., “Transesterification kinetics of soybean oil,”JAOCS 63 (1986) 1375-1380.
Gerpen, J. V., “Biodiesel processing and production,”Fuel Processing Technology 86 (2005) 1097-1107.
Goering, C. E., Schwab, A. W., Daugherty, M. J., Pryde, E. H., Heakin, A. J., “Fuel properties of eleven oils,”Trans. ASAE 25 (1982) 1472-1483.
Han, H., Cao, W., Zhang, J., “Preparation of biodiesel from soybean oil using supercritical methanol and CO2as co-solvent,”Process Biochemistry 40 (2005) 3148-3151.
Hawash, S., Kamal, N., Zaher, F., Kenawi, O., El Diwani, G., “Biodiesel fuel from Jatropha oil via non-catalytic supercritical methanol transesterification,”Fuel 88 (2009) 579-582.
He, H., Wang, T., Zhu, S., “Transesterification kinetics of soybean oil for production of biodiesel in supercritical methanol,”J. Am. Oil. Chem. Soc. 86 (2007) 442-447.
Holliday, R. L., King, J. W., List, G. R., “Hydrolysis of vegetable oils in sub- and supercritical water,”Ind. Eng. Chem. Res. 36 (1997) 932-935.
Ilham, Z., Saka, S., “Dimethyl carbonate as potential reactant in non-catalytic biodiesel production by supercritical method,”Bioresourse Tech. 100 (2009) 1793-1796.
Ilham, Z., Saka, S., “Two-step supercritical dimethyl carbonate method for biodiesel production from Jatropha curcas oil,”Bioresourse Tech. 101 (2010) 2735-2740.
Imahara, H., Minami, E., Hari, S., Saka, S., “Thermal stability of biodiesel in supercritical methanol,”Fuel 87 (2008) 1-6.
Imahara, H., Xin, J., Saka, S., “Effect of CO2/ N2addition to supercritical methanol on reactivities and fuel qualities in biodiesel production,”Fuel 88 (2009) 1329-1332.
Keim, G. I., “Treating fats and fatty oils,”US Patent No. 2,383,601(1945)
Klopfenstein, W. E., Walker, H. S., “Efficiencies of various esters of fatty acids as diesel fuels,”JAOCS 60 (1983) 1596-1598.
Kaita, J., Mimura, T., Fukuoda, N., Hattori, Y., “Catalysts for transesterification,”US Patent 6,407,269, June 18 (2002).
Krawczyk, T., “Biodiesel-alternative fuel makes in roads but hurdles remain,”
INFORM 7 (1996) 801-829.
Kusdiana, D., Saka, S., “Biodiesel fuel from rapeseed oil as prepared in supercritical methanol,”Fuel 80 (2001a) 225-231.
Kusdiana, D., Saka, S., “Kinetics of transesterification in rapeseed oil to biodiesel fuel as treated in supercritical methanol,”Fuel 80 (2001b) 693-698.
Kusdiana, D., Saka, S., “Methyl esterification of free fatty acids of rapeseed oil as treated in supercritical methanol,”J. Chem. Eng. Jpn. 34 (2001c) 383-387.
Kusdiana, D., Saka, S., “Effect of water on biodiesel fuel production by supercritical methanol treatment,”Bioresourse Tech. 91 (2004) 289-295.
Lang, X., Dalai, A. K., Bakhshi, N. N., Reaney, M. J., Hertz, P. B., “Preparation and characterization of bio-diesels from various bio-oils,”Bioresource Tech. 80 (2001) 53-62.
Liang, X., Gong, G., Wu, H., Yang, J., “Highly efficient procedure for the synthesis of biodiesel from soybean oil using chloroaluminate ionic liquid as catalyst,”Fuel 80 (2009) 613-616.
Liu, Y., Wang, L., “Biodiesel production from rapeseed deodorizer distillate in a packed column reactor,”Chem. Eng. Proc. 48 (2009) 1152-1156.
Lotero, E., Liu, Y., Lopez, D. E., Suwannakarn, K., Bruce, D. A., Goodwin, Jr. J. G.,
“Synthesis of biodiesel via acid catalysis,”Ind. Eng. Chem. Res. 44 (2005) 5353-5363.
Lucena, I. L., Silva, G. F., Fernandes, F. A. N., “Biodiesel production by esterification of oleic acid with methanol using a water adsorption apparatus,”Ind. Eng. Chem.
Res. 47 (2008) 6885-6889.
Macario, A., Giordano, G., Onida, B., Cocina, D., Tagarelli, A., Giuffre, A. M.,
“Biodiesel production process by homogeneous / heterogeneous catalytic system using an acid-base catalyst,”Appl. Cata. A : Gen. 378 (2010) 160-168.
Marchett, J. M., Errazu, A. F., “Esterification of free fatty acids using sulfuric acid as catalysts in the presence of triglycerides,”Biomass and Bioenergy 32 (2008) 892-895.
Minami, E., Saka, S., “Kinetics of hydrolysis and methyl esterification for biodiesel production in two-step supercritical methanol process,”Fuel 81 (2006) 2479-2483.
Mittelbach, M., Silberholz, A., Koncar, M., “In novel aspects concerning
acid-catalyzed alcoholysis of triglycerides,”Oils-Fats-Lipids Proceeding of the 21st
World Congress of the International Society for Fats Research, The Hague, October (1995) 497-499.
Nelson, L. A., Foglia, T. A., Marmer, W. N., “Lipase catalyzed production of biodiesel,”JAOCS 73 (1996) 1191-1195.
NIST Chemistry WebBook, http://webbook.nist.gov/chemistry
Noureddini, H., Harkey, D., Medikonduru, V., “A continuous process for the
conversion of vegetable oils into methyl esters of fatty acids,”JAOCS 75 (1998) 1775-1783.
Patil, P. D., Gude, V. G., Deng, S., “Transesterification of camelina sative oil using supercritical and subcritical methanol with cosolvents,”Energy & Fuels 24 (2010) 746-751.
Pinnarat, T., Savage, P. E., “Assessment of noncatalytic biodiesel stnthesis using supercritical reaction conditions,”Ind. Eng. Chem. Res. 47 (2008) 6801-6808.
Saka, S., Isayama, Y., “A new process for catalyst-free production of biodiesel using supercritical methyl acetate,”Fuel 88 (2009) 1307-1313.
Santacesaria, E., Tesser, R., Serio, M. D., Guida, M., Gaetano, D., Agreda, A. G.,
“Kinetics and mass transfer of free fatty acids esterification with methanol in a tubular packed bed reactor: A key pretreatment in biodiesel production,”Ind. Eng.
Chem. Res. 46 (2007) 5113-5121.
Shay, E. G., “Diesel fuel from vegetable oils : Status and opportunities,”Biomass and Bioenergy 4 (1993) 227-242.
Shibasaki-Kitakawa, N., Honda, H., Kuribayashi, H., Toda, T., Fukumura, T., Yonemoto, T., “Biodiesel production using anionic-exchange resin as heterogeneous catalyst,”Bioresource Technology 98 (2007) 416-421.
Shibasaki-Kitakawa, N., Tsuji, T., Chida, K., Kuba, M., Yonemoto, T., “Simple continuous production process of biodiesel fuel from oil with high content of free fatty acid using ion-exchange resin catalysts,”Energy & Fuels 24 (2010)
3634-3638.
Shimada, Y., Watanabe, Y., Samukawa, T., Sugihara, A., Noda, H., Fukuda, H.,
“Conversionof vegetable oil to biodiesel using immobilized candida ntarctica lipase,”JAOCS 76 (1999) 789-793.
Silva, C., Weschenfelder, T. A., Rovani, S., Corazza, F. C., Corazza, M. L., Dariva, C., Oliveria, J. V., “Continuous production of fatty acid ethyl esters from soybean oil in compressed ethanol,”Ind. Eng. Chem. Res. 46 (2007) 5304-5309.
Song, E. S., Lim, J. W., Lee, H. S., Lee, Y. W., “Transesterification of RBD palm oil using supercritical methanol,”J. Supercrit. Fluids 44 (2008) 356-363.
Sprules, F. J., Price, D., “Production of fatty esters,”US Patent 2 (1950) 366-494.
Tan, T. K., Lee, K. T., Mohamed, A. R., “Effects of free fatty acids, water content and co-solvent on biodiesel production by supercritical methanol reaction,”J. Supercrit.
Fluids 53 (2010) 88-91.
Tesser, R., Serio, M. D., Guida, M., Nsatasi, M., Santacesaria, E., “Kinetics of oleic acid esterification with methanol in the presence of triglycerides,”Ind. Eng. Chem.
Res. 44 (2005) 7978-7982.
Varma, M. N., Madras, G., “Synthesis of biodiesel from castor oil and linseed oil in supercritical fluids,”Ind. Eng. Chem. Res. 46 (2007) 1-6.
Velez, A., Hegel, P., Mabe, G., Brignole, E. A., “Density and conversion in biodiesel production with supercritical methanol,”Ind. Eng. Chem. Res. 49 (2010)
7666-7670.
Vicente, G., Coteron, A., Martinez, M., Aracil. J., “Application of the factorial design of experiments and response surface methodology to optimize biodiesel
production,”Industrial Crops and Products 8 (1998) 29-35.
Victor, F. M., George, A., Lawrence, L. T., “Biodiesel fuels through a continuous process of chicken fat supercritical transesterification,”Energy & Fuels 24 (2010) 253-260.
Vieitez, I., da Silve, C., Alckmin, I., Borges, G. R., Corazza, F. C., Oliveira, J. V., Grompone, M. A., Jachmanian, I., “Effect of temperature on the continuous
synthesis of soybean esters under supercritical ethanol,”Energy & Fuels 23 (2009) 558-563.
Viriya-empikul N., Krasae, P., Puttasawat, B., Yoosuk, B., Chollacoop, N.,
Faungnawakij, K., “Waste shells and mollusk and egg as biodiesel production catalysts,”Bioresource Tech. 101 (2010) 3765-3767.
Wang, L., Yang, J., “Transesterification of soybean oil with nano-MgO or not in supercritical and subcritical methanol,”Fuel 86 (2007) 328-333.
Wang, L., Yang, J., “Transesterification of soybean oil with nano-MgO or not in supercritical and subcritical methanol,”Fuel 86 (2007) 328-333.