Hydrolysis of Vegetable Oils to Fatty Acids Using BrÃ¸nsted Acidic Ionic

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Hydrolysis of vegetable oils to fatty acids using Brønsted acidic ionic liquids as catalysts Hui Luo, Kai Xue, Weiyu Fan, Chuan Li, Guozhi Nan, and Zhaomin Li Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/ie501524z • Publication Date (Web): 30 Jun 2014 Downloaded from http://pubs.acs.org on July 4, 2014

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Industrial & Engineering Chemistry Research

Hydrolysis of vegetable oils to fatty acids using Brønsted acidic ionic liquids as catalysts Hui Luo a, b, Kai Xue a Weiyu Fan a *, Chuan Li a, Guozhi Nan a, Zhaomin Li b a

State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao Shandong, China 266580

a

School of Petroleum Engineering, China University of Petroleum, Qingdao Shandong, China 266580

Weiyu Fan, E-mail: [email protected] Abstract: This work reports the hydrolysis of vegetable oils catalyzed by SO3H-functional Brønsted acidic ionic liquids at moderate hydrolysis temperature and reaction time. The results demonstrated that the catalytic activity of ionic liquids is in the sequence 1-(4-sulfonic group) butylcaprolactamium hydrogen sulfate ([HSO3-bCPL][HSO4]) > 1-(4-sulfonic group) butylpyridinium hydrogen sulfate ([HSO3-bPy][HSO4]) > 1-(4-sulfonic group) butyl-3-methylimidazolium hydrogen sulfate

([HSO3-

bMIM][HSO4]) > 1-(4-sulfonic group) butyltriethylaminium hydrogen sulfate ([HSO3-bTEA][HSO4]). In the batch reactor, the reaction conditions of the hydrolysis in the presence of [HSO3-bCPL][HSO4] were investigated and optimized. The yield of fatty acids was greater than 95 wt% at [HSO3bCPL][HSO4] dosage of 8 wt% (based on the weight of oil), water/oil molar ratio of 10:1, hydrolysis temperature of 180 °C, and hydrolysis time of 6 h. The catalytic performance of this ionic liquid remained excellent even after reuse six times. 1. Introduction

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Fatty acids (FAs) produced from the hydrolysis of vegetable oils and fats have been widely applied in the production of soaps, surfactants, lubricants, margarine, cosmetics, pharmaceuticals, etc.1 FAs can also be converted to biodiesel by esterification with alcohol to form fatty acid alkyl esters,2,

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or

decarboxylation to normal alkanes,4, 5 whose carbon chain length distribution is similar to a fossil diesel fuel. These biofuels are the ideal substitute for petroleum-based fuels and chemicals. The hydrolysis of vegetable oils or fats into FAs could be performed using a chemical method or biological (enzymatic) method. For the chemical method, the Colgate-Emery process is the best known industrial process, which is conducted at the operating temperatures of 250~330 °C and the reaction pressure of 5~6 MPa.6 This process is efficient and the triglycerides conversion is over 98%. Water especially in sub- and supercritical states is very effective, and the hydrolysis occurs rapidly at temperatures between 330 and 340 °C yielding 97% or better conversion.7, 8 However, at such high temperatures, the triglycerides would undergo undesired oxidation, dehydration, and interesterification leading to deterioration in the FAs.9, 10 To avoid such limitations, it is necessary that the hydrolysis of triglycerides was performed at the lower temperature. Generally, a catalyst can lower the activation energy of the reaction. For example, the Twitchell fat splitting process operated at milder conditions catalyzed by the Twitchell reagent, which comprises of hydrocarbons, oleic acid and concentrated sulphuric acid.11, 12 However, the use of strong homogeneous acids could increase corrosiveness and produce a large amount of industrial wastewater. Triglycerides splitting into FAs catalyzed by lipases could be carried out under mild conditions, usually at 35 °C and atmospheric pressure. However, this is a long-running operation, requiring 16 h to several days.13-15 Therefore, it is required to develop an efficient, economically beneficial, and environmentally friendly hydrolysis process which can overcome the need for long reaction time at the moderate temperature and exhibit higher yields of FAs. Ngaosuwan et al. had reported the application of solid acid catalysts, tungstated zirconia and Nafion resin nanoparticles supported on mesoporous silica, for the hydrolysis of tricaprylin.16 The reaction was carried out at 110 ~ 150 °C and atmospheric pressure in a semi batch reactor with continuous addition of ACS Paragon Plus Environment

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water at low flow rates. Satyarthi et al. had adopted solid Fe-Zn double-metal cyanide (DMC) complexes as the catalyst for hydrolysis of edible and non-edible vegetable oils and animal fat, and the yield of FAs was greater than 73 wt% at temperatures of 190 °C, autogenous pressure and with 5 wt% of catalyst.17 Nevertheless, their catalytic performance is less than ideal and the conversion of triglycerides does not arrive to 80 %. In addition, these solid acid catalysts would be easily inactivated in recycling. It is a known fact that ionic liquids (ILs) have attracted significant interest and applied successfully as environmentally friendly solvents and catalysts due to their favorable properties. Several ILs, especially SO3H-functional Brønsted acidic ionic liquid, have reported numerous applications for the transesterification of vegetable oils and many other reactions,18-23 because they have high acidity and possess properties of both homogeneous (e.g., without diffusion limitation) and heterogeneous (e.g., readily separable and reusable) catalysts. Nevertheless, an example of direct using ionic liquid as a catalyst for the hydrolysis of oils or fats to FAs is absent from the literature. In this work, several SO3H-functional Brønsted acidic ILs with different nitrogen groups were prepared (as seen in Figure 1) and used for the hydrolysis of edible and non-edible vegetable oils into FAs. The effects of reaction conditions on the hydrolysis of vegetable oils catalyzed by the selected ILs were extensively studied.

Figure 1. Structures of the four Brønsted acidic ILs adopted in this work.


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2. Experimental Section 2.1. Materials Jatropha oil was obtained from China Petroleum Bio-Energy Co. Ltd. Cottonseed oil, Tung oil, rapeseed oil, and soybean oil were purchased locally. Acid value and saponification value of the vegetable oils were listed in Table 1. Triethylamine (AR purity), 1-methyl imidazole (AR purity), pyridine (AR purity), caprolactam (AR purity) and 1,4-butane sultone (AR purity) were purchased from Sinopharm Group Co. Ltd. Standard fatty acid (FA), triglyceride (TG), diacylglycerol (DG) and monoglyceride (MG) samples were purchased from Sigma-Aldrich (Shanghai) Trading Co. Ltd. Table 1. Acid value (AV) and saponification value (SV) of the vegetable oils. Vegetable oils

AV (mg KOH/g)

SV (mg KOH/g)

Molecular weight

Jatropha oil

21.40

222.8

835.7

Cottonseed oil

0.98

195.4

865.5

Tung oil

4.53

191.7

899.2

Rapeseed oil

1.72

185.2

917.3

Soybean oil

0.51

193.5

872.1

Molecular weight = (56.1 × 1000 × 3) / (SV - AV)

2.2. Preparation of SO3H-functional Brønsted acidic ILs The ILs were prepared according to the modification of a reported procedure.21-23 Triethylamine, 1methyl imidazole, pyridine, or caprolactam was stirred solvent free with equal-mole 1,4-butane sultone, respectively, at 60 °C for 24 h. The reaction mixture was then washed several times with toluene and dry evaporated under vacuum (80 °C) for 4 h, giving the zwitterion as a white powder. Afterward, equalmole concentrated sulfuric acid was added dropwise to the zwitterions, and the mixture was vigorously stirred at 80 °C for about 8 h until the zwitterions dissolved. The resultant heavy viscous oil was washed thoroughly with toluene and ether and dry evaporated under vacuum (80 °C) for 4 h to attain the SO3Hfunctional Brønsted acidic ILs.


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The 1H NMR data for [HSO3-bTEA][HSO4]: 1H NMR (500 MHz, D2O, TMS): δ ppm 0.943 (t, 9H), 1.755 (m, 4H), 2.613 (t, 2H), 2.939 (t, 2H), 3.006 (m, 6H). The 1H NMR data for [HSO3-bMIM][HSO4]: 1

H NMR (500 MHz, D2O, TMS): δ ppm 1.468 (m, 2H), 1.696 (m, 2H), 2.674 (t, 2H), 3.561 (s, 3H),

3.894 (t, 2H), 7.031 (s, 1H), 7.146 (s, 1H), 8.365 (s, 1H). The 1H NMR data for [HSO3-bPy][HSO4]: 1H NMR (500 MHz, D2O, TMS): δ ppm 2.005 (m, 2H), 2.034 (s, 3H), 4.346 (t, 2H), 7.641 (d, 2H), 8.111 (t, 1H), 8.447 (d, 2H). The 1H NMR data for [HSO3-bCPL][HSO4]: 1H NMR (500 MHz, D2O, TMS): δ ppm 1.463 (m, 4H), 1.609 (d, 2H), 1.705 (m, 2H), 2.067 (q, 2H), 2.336 (t, 2H), 3.105 (t, 2H), 3.178 (t, 2H), 4.456 (t, 2H). The NMR spectral data of the ionic liquids agreed with their designed structures (Figure 1). 2.3. Hydrolysis reaction The hydrolysis reaction was carried out in batch mode using a 250 mL autoclave with a thermostat, a mechanical stirrer, and a sampling outlet. Vegetable oils, deionized water, and the ionic liquid were poured into the reactor and heated to the desired temperature for a certain time at stirring rate of 1500 rpm. After the reaction, the mixture was cooled to room temperature and transferred to a separatory funnel. The lower layer consisted of glycerol, water and ionic liquid was separated from the upper phase by decantation. The upper layer was then washed several times with hot deionized water and dried over anhydrous sodium sulphate, giving the produced FAs. The acid value determination of the products was carried out using the standard potentiometric titration method.24 The composition of products was analyzed by thin layer chromatography coupled with a flame ionisation detector (TLC-FID), and the TLC–FID instrument used for this work was an Iatroscan MK-6 (Iatron Laboratories, Tokyo, Japan). The samples and standards were dissolved in chloroform, and 1µL aliquot of the solutions was placed to the original point of each chromarod with a 1.5 µL glass syringe. A rack of ten chromarods were developed in a TLC chamber using the first solvent (benzene : chloroform : acetic acid = 150 : 60 : 2, v/v/v) until the solvent front reached the height of 7 cm. The chromarods were removed from the chamber and dried with low flow nitrogen in a dryer. The chromarods were then placed in the second solvent (benzene : hexane = 50:50, v/v) chamber and ACS Paragon Plus Environment

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developed to the height of 10 cm. The chromarods were removed and dried in the dryer and then analyzed in the FID system at the hydrogen flow rate of 160 mL/min, the atmospheric air flow rate of 2 L/min, and scanning speed of 3.0 cm·s-1. Standard FA, TG, DG and MG samples were first examined in order to qualitatively identify the product components and estimate their concentration. A typical chromatogram of the product was presented in Figure 2.

Figure 2. A typical TLC–FID chromatogram of the hydrolysis products. 3. Results and Discussion 3.1. Effect of different catalysts on the hydrolysis Hydrolysis of triglycerides takes place in three consecutive, reversible steps, where TG is first converted into DG then into MG and finally into glycerol, generating one mol of FA at each step.25, 26 Therefore, FA, MG and DG would be found in the hydrolysates. As already mentioned, non-catalyzed hydrolysis is conducted at high temperatures and high pressures, and a catalyst is necessary to lower the activation energy so that the hydrolysis reaction can effectively take place at the lower temperature. The effects of the different catalysts on the hydrolysis of Jatropha oil are presented in Table 2, at catalyst


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dosage of 6 wt % (based on the weight of oil), water/oil molar ratio of 10, hydrolysis temperature of 170 °C and reaction time of 8 h. As a typical industrial acid catalyst, concentrated sulphuric acid was adopted for comparison with the ILs in this work. The data in Table 2 show that the hydrolysis of Jatropha oil exhibited a better TG conversion utilizing the ILs as catalyst than the case of concentrated sulphuric acid. It can be expected that the ILs are more suitable than concentrated sulphuric acid as an acid catalyst in the hydrolysis. Table 2. Hydrolysis of Jatropha oil on different catalysts. Reaction conditions: water/oil (molar ratio) = 10, hydrolysis temperature = 170 °C, reaction time = 8 h, catalyst = 6 wt% of oil. TG conversion

Products distribution (wt%)

(wt%)

FA

H2SO4

87.1±0.6

56.3±2.0 7.9±0.3 22.9±1.1 12.9±0.6 122.9±2.3

[HSO3-bTEA][HSO4]

95.4±0.2

69.7±1.3 8.4±0.3 17.3±0.8 4.6±0.2

147.7±2.2

[HSO3-bMIM][HSO4]

96.2±0.2

79.3±1.0 4.1±0.2 12.8±0.6 3.8±0.2

167.5±2.0

[HSO3-bPy][HSO4]

97.5±0.1

82.0±0.8 4.5±0.2 11.0±0.5 2.5±0.1

173.1±3.2

[HSO3-bCPL][HSO4]

98.6±0.1

88.6±0.6 2.1±0.1 7.9±0.4

187.1±2.7

Products acid value

Catalyst MG

DG

TG

1.4±0.1

(mg KOH/g)

Furthermore, among all the ILs, the hydrolysis reaction showed the best TG conversion and FA yield with [HSO3-bCPL][HSO4] as the catalyst, which indicates that [HSO3-bCPL][HSO4] is the most active catalyst among those investigated ILs in this work. The cations of ILs has a significant impact on their catalytic performance, which is in the sequence [HSO3-bCPL][HSO4] > [HSO3-bPy][HSO4] > [HSO3bMIM][HSO4] > [HSO3-bTEA][HSO4]. Wu et al. compared the Brønsted acidity of ionic liquids and suggested that the Brønsted acidic strengths of the ionic liquids with different nitrogen groups increase in the order of pyridine > Nmethylimidazole > triethylamine.21 It is seen that the ILs with a higher Brønsted acidity are likely to be more efficient in the hydrolysis reaction. 3.2. Reaction Parameter Analysis ACS Paragon Plus Environment

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As described above, [HSO3-bCPL][HSO4] exhibited excellent catalytic performance for the hydrolysis. Therefore, the hydrolysis reaction in the presence of this ionic liquid was carried out under several operating conditions, such as hydrolysis temperature, hydrolysis time, water/oil molar ratio, and the dosage of ionic liquid. Details of these experiments are shown in Figure 3~5.

90

80

FA Yield (%)

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70 1:3 1:5 1 : 10 1 : 15

60

50

2

4

6

8

10

12

Time (h)

Figure 3. Effect of water/oil molar ratio on FAs yield at [HSO3-bCPL][HSO4] dosage of 6 wt% (based on the weight of oil) and hydrolysis temperature of 170 °C. Figure 3 illustrates the influence of the molar ratio of water to oil on the yield of FAs at [HSO3bCPL][HSO4] dosage of 6 wt % (based on the weight of oil) and hydrolysis temperature of 170 °C. As can be seen in Figure 3, the curvilinear trends obtained from the different water/oil molar ratios are similar: the yield of FAs increased with increasing the hydrolysis time, and would reach an almost constant value after about 8 h. Furthermore, FAs yield had a little difference at the beginning of hydrolysis (2 h). However, the difference became significantly obvious at the longer hydrolysis time (after 4 h), and FAs yield increased with water/oil molar ratio from 3:1 to 15:1. These trends are in good agreement with the hydrolysis reaction without the use of a catalyst as reported in the literature.26 When


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the hydrolysis equilibrium had reached after 8 h, the FAs yield became almost stagnant at 73.5 wt%, 81.4 wt%, 88.6 wt%, and 89.4 wt% for the water/oil molar ratio of 3:1, 5:1, 10:1, and 15:1, respectively. Stoichiometrically, one mol of TG will react with three moles of water (water/oil molar ratio = 3:1) to generate three mols of FA and one mol of glycerol. Excess water would be required to provide more opportunity for water molecules to attack TG molecules and drive the equilibrium of the reversible hydrolysis reaction towards the FAs and glycerol. However, further addition of water could no longer affect the FAs yield when water/oil molar ratio was increased from 10:1 to 15:1. Thus, the suitable water/oil molar ratio was chosen as 10:1.

100 90 80

FA Yield (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


70 2 wt% 4 wt% 6 wt% 8 wt% 10 wt%

60 50 40

2

4

6

8

10

12

Time (h)

Figure 4. Effect of [HSO3-bCPL][HSO4] dosage (based on the weight of oil) on FAs yield. Reaction conditions: water/oil molar ratio = 10:1; hydrolysis temperature = 170 °C. The effects of [HSO3-bCPL][HSO4] dosage on the hydrolysis of Jatropha oil are shown in Figure 4. Generally, the TG yield significantly with the increase in catalyst.27 As expected, the FAs yield was raised significantly from 72 wt% or less to over 92 wt% with an increase of the [HSO3-bCPL][HSO4] dosage from 2.0 to 8.0 wt% at the attainment of the hydrolysis equilibrium. When the catalyst dosage


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was greater than the 8.0 wt%, the equilibrium yield of FAs did not substantially increase. Thereby, the optimal dosage of [HSO3-bCPL][HSO4] was 8.0 wt%.

100 90 o

160 C

o

o

180 C

150 C 80

FA Yield (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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o

170 C o

190 C 70 60 50 40

2

4

6

8

10

12

Time (h)

Figure 5. Effect of hydrolysis temperature on FAs yield at [HSO3-bCPL][HSO4] dosage of 8 wt% and water/oil molar ratio of 10:1. The results in Figure 5 show that the effects of hydrolysis temperature on the FAs yield from Jatropha oil. Unquestionably, temperature is an important parameter for the hydrolysis reaction. As presented in Figure 5, the higher hydrolysis temperature provided the higher FAs yield, and could accelerate the attainment of hydrolysis equilibrium. The equilibrium yield of FAs increased from about 60 wt% to above 96 wt% when the hydrolysis temperature was increased from 150 °C to 180 °C. Thus as expected, hydrolysis is an endothermic reaction. However, the effect of hydrolysis temperature on the yield of FAs became smaller with an increase in temperature when the temperature is above 180 °C. Therefore, the appropriate temperature for the hydrolysis of Jatropha oil catalyzed by [HSO3-bCPL][HSO4] was 180 °C. The hydrolysis of different edible and non-edible oils using [HSO3-bCPL][HSO4] were performed under the optimized conditions and the results were stated in Table 3. It can be seen that [HSO3-


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bCPL][HSO4] is very active in the hydrolysis of the adopted vegetable oils, and the TG conversions more than 98 wt% and FAs yields greater than 95 wt % were obtained under the stated conditions. Table 3. Hydrolysis of the different vegetable oils. Reaction conditions: [HSO3-bCPL][HSO4] dosage = 8 wt% of oils, water/oil (molar ratio) = 10, hydrolysis temperature = 180 °C, reaction time = 6 h. TG conversion

Products distribution (wt%)

(wt%)

FA

Jatropha oil

99.6±0.1

Cottonseed oil

Products acid value

Vegetable oils MG

(mg KOH/g)

DG

TG

95.1±0.8 3.1±0.5

1.4±0.2

0.4±0.1 203.7±2.1

98.6±0.3

95.0±1.0 2.3±0.4

1.3±0.3

1.4±0.3 194.9±3.9

Tung oil

99.8±0.1

97.2±0.4 1.9±0.1

0.7±0.2

0.2±0.1 192.5±1.7

Rapeseed oil

98.8±0.3

96.1±0.8 1.7±0.3

1.0±0.2

1.2±0.3 185.3±3.4

Soybean oil

99.6±0.1

96.5±0.6 2.0±0.3

1.1±0.2

0.4±0.1 195.1±2.5

3.3. Lifetime Test of the ILs Catalyst One important aspect of all of the ILs as hydrolysis catalysts is that they can be reused. After initiation of the reaction, the ionic liquid was recovered by distillation in vacuum to remove the excess water and glycerol. The recovered catalytic efficiency of the ILs were investigated and shown in Figure 6. The yields of FAs from Jatropha oil catalyzed by the four ILs remained unchanged even after the catalysts had been reused for six times, which suggest they possess good stability as a catalyst for hydrolysis of the oils. At the same time, the order of their catalytic performance also had not changed after repeated use.


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100

90

Yield (%)

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80 [HSO3-bTEA][HSO4] [HSO3-bMIM][HSO4]

70

[HSO3-bPy][HSO4] [HSO3-bCPL][HSO4]

60

1

2

3

4

5

6

Run

Figure 6. Effect of repeated use of the ILs on the hydrolysis of Jatropha oil at [HSO3-bCPL][HSO4] dosage of 8 wt%, water/oil molar ratio of 10:1, hydrolysis temperature of 180 °C, and hydrolysis time of 6 h. 4. Conclusion Production of FAs from the hydrolysis of various vegetable oils was carried out successfully at moderate hydrolysis temperature and reaction time using SO3H-functional Brønsted acidic ILs. [HSO3bCPL][HSO4] exhibited the highest TG conversion and FA yield, and the catalytic performance of ionic liquids is in the sequence [HSO3-bCPL][HSO4] > [HSO3-bPy][HSO4] > [HSO3-bMIM][HSO4] > [HSO3-bTEA][HSO4]. Complete conversion of TG and FAs yield greater than 95 wt% were obtained in the presence of [HSO3-bCPL][HSO4] at its dosage of 8 wt %, water/oil molar ratio of 10:1, hydrolysis temperature of 180 °C, and hydrolysis time of 6 h. The ionic liquids are reusable, and their catalytic performance remained unchanged over 6 cycles of use. Acknowledgment: This work was supported by National Natural Science Foundation of China (Grant No: 21106186).


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References: (1) Metzger, J. O.; Bornscheuer, U. Lipids as renewable resources: Current state of chemical and biotechnological conversion and diversification. Appl. Microbiol. Biot. 2006, 71, 13–22. (2) Minami, E.; Saka, S. Kinetics of hydrolysis and methyl esterification for biodiesel production in two-step supercritical methanol process. Fuel 2006, 85, 2479–2483. (3) Levine, R. B.; Pinnarat, T.; Savage, P. E. Biodiesel production from wet algal biomass through in situ lipid hydrolysis and supercritical transesterification. Energy Fuels 2010, 24, 5235–5243. (4) Wang, W. C.; Thapaliya, N.; Campos, A.; Stikeleather, L. F.; Roberts, W. L. Hydrocarbon fuels from vegetable oils via hydrolysis and thermo-catalytic decarboxylation. Fuel 2012, 95, 622–629. (5) Asomaning, J.; Mussone, P.; Bressler, D. C. Two-stage thermal conversion of inedible lipid feedstocks to renewable chemicals and fuels. Bioresource technol. 2014, 158, 55–62. (6) Barnebey, H. L.; Brown, A. C. Continuous fat splitting plants using the colgate-emery process. J. Am. Oil Chem. Soc. 1948, 25, 95–99. (7) Holliday, R. L.; King, J. W.; List, G. R. Hydrolysis of Vegetable Oils in Sub- and Supercritical Water. Ind. Eng. Chem. Res. 1997, 36, 932–935. (8) King, J. W.; Holliday, R. L.; List, G. R. Hydrolysis of soybean oil in a subcritical water flow reactor. Green Chem. 1999, 1, 261–264. (9) Rooney, D.; Weatherley, L. R. The effect of reaction conditions upon lipase catalysed hydrolysis of high oleate sunflower oil in a stirred liquid–liquid reactor. Process Biochem. 2001, 36, 947–953. (10) Murty, V. R.; Bhat, J.; Muniswaran, P. K. A. Hydrolysis of oils by using immobilized lipase enzyme: a review. Biotechnol. Bioprocess Eng. 2002, 7, 57–66. ACS Paragon Plus Environment

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(11) Lascaray, L. Industrial fat splitting. J. Am. Oil Chem. Soc. 1952, 29, 362–366. (12) Hartman, L. Effect of temperature on the twitchell fat splitting process and its catalysts. J. Am. Oil Chem. Soc. 1953, 30, 349–350. (13) Villeneuve, P. Plant lipases and their applications in oils and fats modification. Eur. J. Lipid Sci. Technol. 2003, 105, 308–317. (14) Sharma, S.; Gangal, S.; Rauf, A. Lipase mediated hydrolysis of Mimusops elengi and Parkinsonia aculeate seed oils for the determination of positional distribution of fatty acids. Ind. Crops Prod. 2009, 30, 325–328. (15) Mendes, A. A.; Oliveira, P. C.; Castro, H. F. Properties and biotechnological applications of porcine pancreatic lipase. J. Mol. Catal. B: Enzym. 2012, 78, 119–134. (16) Ngaosuwan, K.; Lotero, E.; Suwannakarn, K.; Goodwin Jr, J. G.; Praserthdam, P. Hydrolysis of triglycerides using solid acid catalysts. Ind. Eng. Chem. Res. 2009, 48, 4757–4767. (17) Satyarthi, J. K.; Srinivas, D.; Ratnasamy, P. Hydrolysis of vegetable oils and fats to fatty acids over solid acid catalysts. Appl. Catal., A-Gen. 2011, 391, 427–435. (18) Zhao, Y.; Long, J.; Deng, F.; Liu, X.; Li, Z.; Xia, C.; Peng, J.; Catalytic amounts of Brønsted acidic ionic liquids promoted esterification: study of acidity–activity relationship. Catal. Commun. 2009, 10, 732–736. (19) Tao, D. J.; Wu, Y. T.; Zhou, Z.; Geng, J.; Hu, X. B.; Zhang, Z. B. Kinetics for the esterification reaction of n-butanol with acetic acid catalyzed by noncorrosive brønsted acidic ionic liquids. Ind. Eng. Chem. Res. 2011, 50, 1989–1996. (20) Wang, H.; Wu, C.; Bu, X.; Tang, W.; Li, L.; Qiu, T. A benign preparation of sec-butanol via transesterification from sec-butyl acetate using the acidic Imidazolium ionic liquids as catalysts. Chem. Eng. J. 2014, 246, 366–372. ACS Paragon Plus Environment

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Page 15 of 15

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(21) Wu, Q.; Chen, H.; Han, M.; Wang, D.; Wang, J. Transesterification of cottonseed oil catalyzed by Brønsted acidic ionic liquids. Ind. Eng. Chem. Res. 2007, 46, 7955–7960. (22) Han, M.; Yi, W.; Wu, Q.; Liu, Y.; Hong, Y.; Wang, D. Preparation of biodiesel from waste oils catalyzed by a Brønsted acidic ionic liquid. Bioresource technol. 2009, 100, 2308–2310. (23) Zhang, L.; Xian, M.; He, Y.; Li, L.; Yang, J.; Yu, S.; Xu, X. A Brønsted acidic ionic liquid as an efficient and environmentally benign catalyst for biodiesel synthesis from free fatty acids and alcohols. Bioresource technol. 2009, 100, 4368–4373. (24) ISO 660: 2009. Animal and vegetable fats and oils – Determination of acid value and acidity. Geneva: ISO, 2009. (25) Patil, T. A.; Butala, D. N.; Raghunathan, T. S.; Shankar, H. S. Thermal hydrolysis of vegetable oils and fats. 1. Reaction kinetics. Ind. Eng. Chem. Res. 1988, 27, 727–735. (26) Kansedo, J.; Lee, K. T. Non-catalytic hydrolysis of sea mango (Cerbera odollam) oil and various non-edible oils to improve their solubility in alcohol for biodiesel production. Chem. Eng. J. 2014, 237, 1–7. (27) Madon, R. J.; Boudart, M. Experimental criterion for the absence of artifacts in the measurement of rates of heterogeneous catalytic reactions. Ind. Eng. Chem. Fundam. 1982, 21, 438–447.


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Hydrolysis of Vegetable Oils to Fatty Acids Using BrÃ¸nsted Acidic Ionic

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