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A sustainable method to produce biodiesel through an emulsion formation induced by a high shear mixer
Fuel 189 (2017) 436–439
Contents lists available at ScienceDirect
Fuel journal homepage: www.elsevier.com/locate/fuel
Short communication
A sustainable method to produce biodiesel through an emulsion formation induced by a high shear mixer Manuel Sánchez-Cantú a,⇑, Lydia M. Pérez-Díaz a, Maribel Morales-Téllez a, Isamar Martínez-Santamaría a, Jazmín C. Hilario-Martínez b, Jesús Sandoval-Ramírez b a b
Laboratorio de biocombustibles, Facultad de Ingeniería Química, Benemérita Universidad Autónoma de Puebla, 72570 Puebla, Puebla, Mexico Facultad de Ciencias Químicas, Benemérita Universidad Autónoma de Puebla, 72570 Puebla, Puebla, Mexico
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
Biodiesel was obtained in 60 s and
normal conditions. The process consisted of an emulsion
production induced by a HSM process. Nanodroplets performed a fast and efficient mass-transfer among reactants.
NaOH/MeOH
HIGH SHEAR MIXING (Nanodroplets)
Soybean oil
RT, 60 s, 4000 rpm
BIODIESEL
GLYCERIN
a r t i c l e
i n f o
Article history: Received 2 August 2016 Received in revised form 24 October 2016 Accepted 25 October 2016 Available online 1 November 2016 Keywords: Biodiesel High shear mixer Soybean Nanodroplets Transesterification
a b s t r a c t This paper describes a sustainable alternative for biodiesel production. It consists in producing an emulsion by a high shear mixing process (4000 rpm) between two immiscible liquids (methanol and soybean oil), in the presence of NaOH as catalyst. This simplified process improved significantly the biodiesel production since the transesterification reaction was carried out at room temperature, in 60 s, at 22 °C and 1% catalyst concentration. The operation conditions allowed generating nanodroplets which acted as efficient mass-transfer reactors. The effect of the catalyst amount and conversions achieved after centrifugation and decantation were investigated. It was demonstrated that the highest conversion was achieved after total glycerin decantation which was completed after 3 h of settling. A quantitative conversion of triglycerides to methyl esters was achieved permitting the easy recovering of glycerin. Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction Energy diversification has become an important issue worldwide in the last years. In this sense, biomass-derived energy has a considerable technical potential among alternative energy ⇑ Corresponding author. E-mail address: [email protected] (M. Sánchez-Cantú). http://dx.doi.org/10.1016/j.fuel.2016.10.107 0016-2361/Ó 2016 Elsevier Ltd. All rights reserved.
resources for biofuels production and is an alternative for petroleum-derived fuels. Vegetable oils have been considered as a feasible feedstock for biofuel production due to their non-toxic and renewable characteristics. However, the main problem associated to the use of crude vegetable oils in diesel engines is their high viscosity causing problems such as engine ignition in cold weathers, plugging and
437
M. Sánchez-Cantú et al. / Fuel 189 (2017) 436–439 Table 1 Representative reports dealing with high shear mixers use for biodiesel production. Author(s)
Reactants/catalyst
Reaction temperature, °C
Reaction time, min
Conversion%
Shear speed, rpm
Reference
Noureddini et al.
Soybean oil Methanol NaOH
70
6.67
98
0–3600
[10]
McFarlane et al.
Soybean oil Methanol 30% Methanol/methylate
80
2
90
3000–4800
[11]
Da Silva et al.
Soybean oil Ethanol NaOH
78
12
99.26
7900
[12]
Choedkiatsakul et al.
Palm oil Methanol NaOH
N. R.
5
99.8
N. R.
[13]
N.R. = Not reported.
100
Conversion %
80
60
40
20
0 0.2
0.4
0.6
0.8
1.0
Catalyst percentage Fig. 1. Conversion of soybean oil vs catalyst concentration, determined immediately after centrifugation.
gumming of filters and tubings, coking of injector nozzles, among others [1]. To reduce the viscosity of vegetable oils several methods such as dilution, microemulsion, pyrolysis, and transesterification have been evaluated, being the last one the most studied option [2,3]. Transesterification involves the reaction between an alcohol (mainly methanol), and an ester, v. gr. the triacylesters present in vegetable oils and animal fats, to generate a new ester (mainly methyl esters), in the presence of a catalyst. It is worth mentioning that a large number of methodologies have been developed looking
A
B
C
for its sustainability. Those methodologies include reactive distillation [4], supercritic conditions [5], reactive extraction column [6], microwave [7] and ultrasound assistance [8]. However, although great progress has been achieved there is still a long road ahead. A viable alternative for biodiesel production is represented by an emulsion production promoted by high shear mixers. Those mixers are generally used for homogenization, solubilization, emulsification, powder wet-out, grinding and particle size reduction. The mixers are comprised of a rotor that turns at high speed within a stationary stator, mechanically shearing particles and droplets, expelling the material at high velocity into the surroundings and creating intense hydraulic shear [9]. The use of high shear mixers in biodiesel production is scarce in the literature. Some representative reports are presented in Table 1. It is worthwhile to remark that although high-shear mixing could simplify substantially biodiesel production the use of temperature is still required. In this paper an innovative methodology for biodiesel manufacture at room-temperature and ambient pressure based only of an emulsion production between the raw materials (soybean oil and methanol) and the catalyst is reported. The effect of the catalyst amount and biodiesel/glycerin separation procedure (centrifugation and decantation) were studied. 2. Materials and methods 2.1. Materials Technical grade methanol was purchased from Meyer and dried using metallic magnesium turnings and iodine. Soybean oil was
D
E
Fig. 2. Biodiesel separation from glycerin/NaOH (lower layer), in a separation funnel: (A) 0 min, (B) 1 h, (C) 2 h, (D) 3 h and (E) 4 h.
438
M. Sánchez-Cantú et al. / Fuel 189 (2017) 436–439
100
Conversion %
98 96 94 92 90 88 86 0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Catalyst percentage Fig. 3. Conversion percentage vs catalyst concentration, determined after 3 h of settling.
purchased from Aceites y Proteínas El Calvario, Tehuacán (Puebla, México), and was used as received without further purification. Sodium hydroxide (98.2% purity) was procured from Golden Bell. Dispersions were performed using a ROSS HSM-100 LCI high shear mixer with a fine screen stator head dispersion attachment. 2.2. Characterization 2.2.1. Proton Nuclear Magnetic Resonance (1H NMR) 1 H NMR spectra were measured on a Bruker 300 MHz spectrometer in deuterated chloroform (CDCl3). The residual solvent signal (7.26 ppm) was used as shift reference. The chosen signals for integration were those of the methoxyl group in the fatty acid methyl esters (FAMEs) (3.66 ppm, singlet) and the methylene protons from the residual soybean oil glyceric triesters (4.14– 4.27 ppm, two doublet of doublets). Conversion was calculated from the integrated areas of the aforementioned signals following the procedure described by Knothe [14]. 2.3. Transesterification reaction 400 mL of soybean oil, 100 mL of methanol (6:1 MeOH/oil molar ratio) were placed into a 1 L glass vessel. The amount of NaOH varied from 0.1 to 1 wt% (respective to the reactants mass). Then, the mixture was dispersed at 4000 rpm for 60 s at 22 °C. A temperature increase of 2 °C was identified after dispersion. Afterwards, a 10 mL emulsion sample was centrifuged at 7000 rpm during 60 s to separate the oil-methanol-BD layer from the glycerin phase. Then, the sample was immersed in ice to stop reaction and analyzed immediately by 1H NMR. On the other hand, the rest of the crude was transferred to a 500 mL separation funnel to allow biodiesel and glycerin decantation. After settling the upper layer (biodiesel) was analyzed by 1H NMR.
separation and afterwards products characteristics are verified [15]. The reaction mixture appearance (1% catalyst amount) throughout settling time (0–180 min) is shown in Fig. 2. Initially, the emulsion was uniform (no alcohol layer was observed) and it was only broken by glycerin decantation. In this sense, a full separation between glycerin and crude biodiesel was accomplished within 3 h. However, it is worth mentioning that phases’ transparency was observed until 12 h. The conversion percentages achieved after 180 min of settling were determined (see Fig. 3). Although the conversions achieved after 60 s of high shear mixing were lower than the required by EN 14214 requirements (96.5%), except where 1% catalyst was used, after glycerin settling conversions of 96.9% and 99.1% were obtained with 0.6% and 0.75% of catalyst amount. In the literature it is generally reported that the base-catalyzed transesterification reaction between soybean oil and methanol with ratios up to 6:1 MeOH/oil is carried out at temperatures in the 40–80 °C range, catalyst concentration of 0.2–0.9% and reaction times of 30–90 min [15–17]. In this sense, it is recognized that high temperatures and quite long reaction times are required when oils such as soybean, rapeseed, palm and sunflower oil are used for biodiesel production [15]. Our results indicate that reaction time was shortened and transesterification could be conducted at room temperature and atmospheric pressure. Our results are evidently close related to the emulsion formation which causes the formation of oil and alcohol/catalyst nanodroplets, encapsulating one into the other, where reactants and the catalyst are in a very close contact minimizing mass transfer resistance thus shifting the reaction equilibrium towards the transesterification products (biodiesel and glycerin), shortening reaction time. In this sense, although droplet sizes were not determined, Bora et al. have reported that nanodroplets with average size of 44.74 nm and as small as <5 nm, can be produced even using magnetic stirrers at 350 rpm [18]. 4. Conclusions A simple and sustainable methodology for biodiesel production was developed using 60 s of dispersion, 6:1 MeOH/oil molar ratio and 1.0 wt% of catalyst. After centrifugation a quantitative conversion to biodiesel was achieved. The most important finding is that a high mass transfer operation involving nanodroplets is produced by means of a high shear mixer emulsion, spinning at 4000 rpm. To the best of our knowledge, this is the first time that biodiesel is produced by a simplified methodology. This new method provides a viable alternative for biodiesel production either in a batch or in a continuous way. Acknowledgements Maribel Morales-Téllez and Jazmín C. Hilario-Martínez thank Consejo Nacional de Ciencia y Tecnología (CONACyT) for the granted Master and Ph. D. scholarships, respectively.
3. Results and discussion As it can be seen in Fig. 1, conversion percentages achieved after centrifugation increased (3.8%, 72.4%, 84.8%, 85.1%, 90.4%, 95.1% and 96.8%) with the catalyst amount (0.1%, 0.25%, 0.35%, 0.5%, 0.6%, 0.75% and 1%). As specified in the experimental section, after the batch high shear mixing process a sample was taken and centrifuged to verify reaction conversion. In this context, although biodiesel/glycerin separation can be carried out by centrifugation after reaction the products are generally transferred to a settling tank to allow their
References [1] Harwood HJ. Oleochemicals as a fuel: mechanical and economic feasibility. J Am Oil Chem Soc 1984;61:315–24. [2] Agarwal AK. Biofuels (alcohols and biodiesel) applications as fuels for internal combustion engines. Prog Energy Combust 2007;33:233–71. [3] Knothe G, Krahl J, Van Gerpen J. The biodiesel handbook. Champaign (IL): AOCS Press; 2005. [4] Prasertsit K, Mueanmas C, Tongurai C. Transesterification of palm oil with methanol in a reactive distillation column. Chem Eng Process 2013;70:21–6. [5] Pinnarat T, Savage PE. Assessment of noncatalytic biodiesel synthesis using supercritical reaction conditions. Ind Eng Chem Res 2008;47:6801–8.
M. Sánchez-Cantú et al. / Fuel 189 (2017) 436–439 [6] Cadavid JG, Godoy-Silva RD, Narvaez PC, Camargo M, Fonteix C. Biodiesel production in a counter-current reactive extraction column: modelling, parametric identification and optimization. Chem Eng J 2013;228:717–23. [7] Leadbeater NE, Stencel LM. Fast, easy preparation of biodiesel using microwave heating. Energy Fuels 2006;20:2281–3. [8] Kalva A, Sivasankar T, Moholkar VS. Physical mechanism of ultrasoundassisted synthesis of biodiesel. Ind Eng Chem Res 2009;48:534–44. [9] Ross high shear mixers guide; July 16th, 2016.. [10] Noureddini H, Harkey D, Medikonduru V. A continuous process for the conversion of vegetable oils into methyl esters of fatty acids. J Am Oil Chem Soc 1998;75:1775–83. [11] McFarlane J, Tsouris C, Birdwell JFJ, Schuh DL, Jennings HL, Biotrago AMP, Terpstra SM. Production of biodiesel at the kinetic limit in a centrifugal reactor/separator. Ind Eng Chem Res 2010;49:3160–9. [12] Da Silva NL, Garnica JAG, Batistella CB, Maciel MR, Maciel FilhoR. Use of experimental design to investigate biodiesel production by multiple-stage Ultra-Shear reactor. Bioresour Technol 2011;102:2672–7. [13] Choedkiatsakul I, Ngaosuwan K, Assabumrungrat S, Tabasso S, Cravotto G. Integrated flow reactor that combines high-shear mixing and microwave irradiation for biodiesel production. Biomass Bioenergy 2015;77:186–91.
439
[14] Knothe G. Monitoring a progressing transesterification reaction by fiber-optic near infrared spectroscopy with correlation to 1H nuclear magnetic resonance spectroscopy. J Am Oil Chem Soc 2000;77:489–93. [15] Santori G, Nicola GD, Moglie M, Polonara F. A review analyzing the industrial biodiesel production practice starting from vegetable oil refining. Appl Energy 2012;92:109–32. [16] Wu L, Wei T, Tong Z, Zou Y, Lin Z, Sun J. Bentonite-enhanced biodiesel production by NaOH-catalyzed transesterification of soybean oil with methanol. Fuel Process Technol 2016;144:334–40. [17] Likozar B, Levec J. Transesterification of canola, palm, peanut, soybean and sunflower oil with methanol, ethanol, isopropanol, butanol and tert-butanol to biodiesel: modelling of chemical equilibrium, reaction kinetics and mass transfer based on fatty acid composition. Appl Energy 2014;123:108–20. [18] Bora P, Boro J, Konwar LJ, Deka D. Formulation of microemulsion based hybrid biofuel from waste cooking oil-A comparative study with biodiesel. J Energy Inst; 2015 [in press]. http://dx.doi.org/10.1016/j.joei.2015.07.001.
Contents lists available at ScienceDirect
Fuel journal homepage: www.elsevier.com/locate/fuel
Short communication
A sustainable method to produce biodiesel through an emulsion formation induced by a high shear mixer Manuel Sánchez-Cantú a,⇑, Lydia M. Pérez-Díaz a, Maribel Morales-Téllez a, Isamar Martínez-Santamaría a, Jazmín C. Hilario-Martínez b, Jesús Sandoval-Ramírez b a b
Laboratorio de biocombustibles, Facultad de Ingeniería Química, Benemérita Universidad Autónoma de Puebla, 72570 Puebla, Puebla, Mexico Facultad de Ciencias Químicas, Benemérita Universidad Autónoma de Puebla, 72570 Puebla, Puebla, Mexico
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
Biodiesel was obtained in 60 s and
normal conditions. The process consisted of an emulsion
production induced by a HSM process. Nanodroplets performed a fast and efficient mass-transfer among reactants.
NaOH/MeOH
HIGH SHEAR MIXING (Nanodroplets)
Soybean oil
RT, 60 s, 4000 rpm
BIODIESEL
GLYCERIN
a r t i c l e
i n f o
Article history: Received 2 August 2016 Received in revised form 24 October 2016 Accepted 25 October 2016 Available online 1 November 2016 Keywords: Biodiesel High shear mixer Soybean Nanodroplets Transesterification
a b s t r a c t This paper describes a sustainable alternative for biodiesel production. It consists in producing an emulsion by a high shear mixing process (4000 rpm) between two immiscible liquids (methanol and soybean oil), in the presence of NaOH as catalyst. This simplified process improved significantly the biodiesel production since the transesterification reaction was carried out at room temperature, in 60 s, at 22 °C and 1% catalyst concentration. The operation conditions allowed generating nanodroplets which acted as efficient mass-transfer reactors. The effect of the catalyst amount and conversions achieved after centrifugation and decantation were investigated. It was demonstrated that the highest conversion was achieved after total glycerin decantation which was completed after 3 h of settling. A quantitative conversion of triglycerides to methyl esters was achieved permitting the easy recovering of glycerin. Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction Energy diversification has become an important issue worldwide in the last years. In this sense, biomass-derived energy has a considerable technical potential among alternative energy ⇑ Corresponding author. E-mail address: [email protected] (M. Sánchez-Cantú). http://dx.doi.org/10.1016/j.fuel.2016.10.107 0016-2361/Ó 2016 Elsevier Ltd. All rights reserved.
resources for biofuels production and is an alternative for petroleum-derived fuels. Vegetable oils have been considered as a feasible feedstock for biofuel production due to their non-toxic and renewable characteristics. However, the main problem associated to the use of crude vegetable oils in diesel engines is their high viscosity causing problems such as engine ignition in cold weathers, plugging and
437
M. Sánchez-Cantú et al. / Fuel 189 (2017) 436–439 Table 1 Representative reports dealing with high shear mixers use for biodiesel production. Author(s)
Reactants/catalyst
Reaction temperature, °C
Reaction time, min
Conversion%
Shear speed, rpm
Reference
Noureddini et al.
Soybean oil Methanol NaOH
70
6.67
98
0–3600
[10]
McFarlane et al.
Soybean oil Methanol 30% Methanol/methylate
80
2
90
3000–4800
[11]
Da Silva et al.
Soybean oil Ethanol NaOH
78
12
99.26
7900
[12]
Choedkiatsakul et al.
Palm oil Methanol NaOH
N. R.
5
99.8
N. R.
[13]
N.R. = Not reported.
100
Conversion %
80
60
40
20
0 0.2
0.4
0.6
0.8
1.0
Catalyst percentage Fig. 1. Conversion of soybean oil vs catalyst concentration, determined immediately after centrifugation.
gumming of filters and tubings, coking of injector nozzles, among others [1]. To reduce the viscosity of vegetable oils several methods such as dilution, microemulsion, pyrolysis, and transesterification have been evaluated, being the last one the most studied option [2,3]. Transesterification involves the reaction between an alcohol (mainly methanol), and an ester, v. gr. the triacylesters present in vegetable oils and animal fats, to generate a new ester (mainly methyl esters), in the presence of a catalyst. It is worth mentioning that a large number of methodologies have been developed looking
A
B
C
for its sustainability. Those methodologies include reactive distillation [4], supercritic conditions [5], reactive extraction column [6], microwave [7] and ultrasound assistance [8]. However, although great progress has been achieved there is still a long road ahead. A viable alternative for biodiesel production is represented by an emulsion production promoted by high shear mixers. Those mixers are generally used for homogenization, solubilization, emulsification, powder wet-out, grinding and particle size reduction. The mixers are comprised of a rotor that turns at high speed within a stationary stator, mechanically shearing particles and droplets, expelling the material at high velocity into the surroundings and creating intense hydraulic shear [9]. The use of high shear mixers in biodiesel production is scarce in the literature. Some representative reports are presented in Table 1. It is worthwhile to remark that although high-shear mixing could simplify substantially biodiesel production the use of temperature is still required. In this paper an innovative methodology for biodiesel manufacture at room-temperature and ambient pressure based only of an emulsion production between the raw materials (soybean oil and methanol) and the catalyst is reported. The effect of the catalyst amount and biodiesel/glycerin separation procedure (centrifugation and decantation) were studied. 2. Materials and methods 2.1. Materials Technical grade methanol was purchased from Meyer and dried using metallic magnesium turnings and iodine. Soybean oil was
D
E
Fig. 2. Biodiesel separation from glycerin/NaOH (lower layer), in a separation funnel: (A) 0 min, (B) 1 h, (C) 2 h, (D) 3 h and (E) 4 h.
438
M. Sánchez-Cantú et al. / Fuel 189 (2017) 436–439
100
Conversion %
98 96 94 92 90 88 86 0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Catalyst percentage Fig. 3. Conversion percentage vs catalyst concentration, determined after 3 h of settling.
purchased from Aceites y Proteínas El Calvario, Tehuacán (Puebla, México), and was used as received without further purification. Sodium hydroxide (98.2% purity) was procured from Golden Bell. Dispersions were performed using a ROSS HSM-100 LCI high shear mixer with a fine screen stator head dispersion attachment. 2.2. Characterization 2.2.1. Proton Nuclear Magnetic Resonance (1H NMR) 1 H NMR spectra were measured on a Bruker 300 MHz spectrometer in deuterated chloroform (CDCl3). The residual solvent signal (7.26 ppm) was used as shift reference. The chosen signals for integration were those of the methoxyl group in the fatty acid methyl esters (FAMEs) (3.66 ppm, singlet) and the methylene protons from the residual soybean oil glyceric triesters (4.14– 4.27 ppm, two doublet of doublets). Conversion was calculated from the integrated areas of the aforementioned signals following the procedure described by Knothe [14]. 2.3. Transesterification reaction 400 mL of soybean oil, 100 mL of methanol (6:1 MeOH/oil molar ratio) were placed into a 1 L glass vessel. The amount of NaOH varied from 0.1 to 1 wt% (respective to the reactants mass). Then, the mixture was dispersed at 4000 rpm for 60 s at 22 °C. A temperature increase of 2 °C was identified after dispersion. Afterwards, a 10 mL emulsion sample was centrifuged at 7000 rpm during 60 s to separate the oil-methanol-BD layer from the glycerin phase. Then, the sample was immersed in ice to stop reaction and analyzed immediately by 1H NMR. On the other hand, the rest of the crude was transferred to a 500 mL separation funnel to allow biodiesel and glycerin decantation. After settling the upper layer (biodiesel) was analyzed by 1H NMR.
separation and afterwards products characteristics are verified [15]. The reaction mixture appearance (1% catalyst amount) throughout settling time (0–180 min) is shown in Fig. 2. Initially, the emulsion was uniform (no alcohol layer was observed) and it was only broken by glycerin decantation. In this sense, a full separation between glycerin and crude biodiesel was accomplished within 3 h. However, it is worth mentioning that phases’ transparency was observed until 12 h. The conversion percentages achieved after 180 min of settling were determined (see Fig. 3). Although the conversions achieved after 60 s of high shear mixing were lower than the required by EN 14214 requirements (96.5%), except where 1% catalyst was used, after glycerin settling conversions of 96.9% and 99.1% were obtained with 0.6% and 0.75% of catalyst amount. In the literature it is generally reported that the base-catalyzed transesterification reaction between soybean oil and methanol with ratios up to 6:1 MeOH/oil is carried out at temperatures in the 40–80 °C range, catalyst concentration of 0.2–0.9% and reaction times of 30–90 min [15–17]. In this sense, it is recognized that high temperatures and quite long reaction times are required when oils such as soybean, rapeseed, palm and sunflower oil are used for biodiesel production [15]. Our results indicate that reaction time was shortened and transesterification could be conducted at room temperature and atmospheric pressure. Our results are evidently close related to the emulsion formation which causes the formation of oil and alcohol/catalyst nanodroplets, encapsulating one into the other, where reactants and the catalyst are in a very close contact minimizing mass transfer resistance thus shifting the reaction equilibrium towards the transesterification products (biodiesel and glycerin), shortening reaction time. In this sense, although droplet sizes were not determined, Bora et al. have reported that nanodroplets with average size of 44.74 nm and as small as <5 nm, can be produced even using magnetic stirrers at 350 rpm [18]. 4. Conclusions A simple and sustainable methodology for biodiesel production was developed using 60 s of dispersion, 6:1 MeOH/oil molar ratio and 1.0 wt% of catalyst. After centrifugation a quantitative conversion to biodiesel was achieved. The most important finding is that a high mass transfer operation involving nanodroplets is produced by means of a high shear mixer emulsion, spinning at 4000 rpm. To the best of our knowledge, this is the first time that biodiesel is produced by a simplified methodology. This new method provides a viable alternative for biodiesel production either in a batch or in a continuous way. Acknowledgements Maribel Morales-Téllez and Jazmín C. Hilario-Martínez thank Consejo Nacional de Ciencia y Tecnología (CONACyT) for the granted Master and Ph. D. scholarships, respectively.
3. Results and discussion As it can be seen in Fig. 1, conversion percentages achieved after centrifugation increased (3.8%, 72.4%, 84.8%, 85.1%, 90.4%, 95.1% and 96.8%) with the catalyst amount (0.1%, 0.25%, 0.35%, 0.5%, 0.6%, 0.75% and 1%). As specified in the experimental section, after the batch high shear mixing process a sample was taken and centrifuged to verify reaction conversion. In this context, although biodiesel/glycerin separation can be carried out by centrifugation after reaction the products are generally transferred to a settling tank to allow their
References [1] Harwood HJ. Oleochemicals as a fuel: mechanical and economic feasibility. J Am Oil Chem Soc 1984;61:315–24. [2] Agarwal AK. Biofuels (alcohols and biodiesel) applications as fuels for internal combustion engines. Prog Energy Combust 2007;33:233–71. [3] Knothe G, Krahl J, Van Gerpen J. The biodiesel handbook. Champaign (IL): AOCS Press; 2005. [4] Prasertsit K, Mueanmas C, Tongurai C. Transesterification of palm oil with methanol in a reactive distillation column. Chem Eng Process 2013;70:21–6. [5] Pinnarat T, Savage PE. Assessment of noncatalytic biodiesel synthesis using supercritical reaction conditions. Ind Eng Chem Res 2008;47:6801–8.
M. Sánchez-Cantú et al. / Fuel 189 (2017) 436–439 [6] Cadavid JG, Godoy-Silva RD, Narvaez PC, Camargo M, Fonteix C. Biodiesel production in a counter-current reactive extraction column: modelling, parametric identification and optimization. Chem Eng J 2013;228:717–23. [7] Leadbeater NE, Stencel LM. Fast, easy preparation of biodiesel using microwave heating. Energy Fuels 2006;20:2281–3. [8] Kalva A, Sivasankar T, Moholkar VS. Physical mechanism of ultrasoundassisted synthesis of biodiesel. Ind Eng Chem Res 2009;48:534–44. [9] Ross high shear mixers guide; July 16th, 2016.
439
[14] Knothe G. Monitoring a progressing transesterification reaction by fiber-optic near infrared spectroscopy with correlation to 1H nuclear magnetic resonance spectroscopy. J Am Oil Chem Soc 2000;77:489–93. [15] Santori G, Nicola GD, Moglie M, Polonara F. A review analyzing the industrial biodiesel production practice starting from vegetable oil refining. Appl Energy 2012;92:109–32. [16] Wu L, Wei T, Tong Z, Zou Y, Lin Z, Sun J. Bentonite-enhanced biodiesel production by NaOH-catalyzed transesterification of soybean oil with methanol. Fuel Process Technol 2016;144:334–40. [17] Likozar B, Levec J. Transesterification of canola, palm, peanut, soybean and sunflower oil with methanol, ethanol, isopropanol, butanol and tert-butanol to biodiesel: modelling of chemical equilibrium, reaction kinetics and mass transfer based on fatty acid composition. Appl Energy 2014;123:108–20. [18] Bora P, Boro J, Konwar LJ, Deka D. Formulation of microemulsion based hybrid biofuel from waste cooking oil-A comparative study with biodiesel. J Energy Inst; 2015 [in press]. http://dx.doi.org/10.1016/j.joei.2015.07.001.