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Production of Monoacylglycerols from FullyHydrogenated Palm Oil Catalyzed by HydrotalciteLoaded with K2CO3Zhen Zhang a , Xiang Ma a , Yong Wang a , Rian Yan a & Manman Liu aa Department of Food Science and Engineering, College of Science and Engineering , JinanUniversity , Guangzhou , ChinaAccepted author version posted online: 04 Jun 2014.

To cite this article: Zhen Zhang , Xiang Ma , Yong Wang , Rian Yan & Manman Liu (2014): Production of Monoacylglycerolsfrom Fully Hydrogenated Palm Oil Catalyzed by Hydrotalcite Loaded with K2CO3 , Chemical Engineering Communications, DOI:10.1080/00986445.2013.853294

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Production of Monoacylglycerols from Fully Hydrogenated Palm Oil Catalyzed by Hydrotalcite Loaded with K2CO3

Zhen Zhang1, Xiang Ma1, Yong Wang1, Rian Yan1, Manman Liu1

1Department of Food Science and Engineering, College of Science and Engineering,

Jinan University, Guangzhou, China

Corresponding author: Yong Wang, Department of Food Science and Engineering, College of Science and Engineering, Jinan University, 601 Huangpu Avenue West,

Guangzhou, 510632, China, E-mail : twyong@jnu.edu.cn

Abstract

This study reports a new method of producing high-purity monoacylglycerols (MAGs) by

glycerolysis of fully hydrogenated palm oil (FHPO) catalyzed by hydrotalcite loaded

with K2CO3 (K2CO3/HT). The effects of reaction temperature, reaction time, catalyst

(K2CO3/HT) loading, and mass ratio of FHPO to glycerol on glycerolysis were

investigated. The selected conditions included a reaction temperature of 200 °C,

K2CO3/HT loading at 0.8 wt.% (FHPO mass), a 5:2 mass ratio of FHPO to glycerol, and

a reaction time of 2 h. Under these selected conditions, the yield of MAGs in the

acylglycerol phase reached 46.8 wt.%. A two-stage molecular distillation was introduced

to purify MAGs, and the final MAG product was obtained with a purity of 96.6 wt.% and

a recovery of 96.8%. Furthermore, the recycled K2CO3/HT was reactivated with restored

catalytic efficiency through impregnation, carbonation, and recalcination.

KEYWORDS: hydrotalcite loaded with K2CO3; glycerolysis; molecular distillation;

monoacylglycerols

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Abbreviations: MAG, monoacylglycerol; DAG, diacylglycerol; TAG,

triacylglycerol; FFA, free fatty acid; FHPO, fully hydrogenated palm oil; GC, gas

chromatography; HT, hydrotalcite; X-RD, X-ray diffraction; IR, infrared spectroscopy;

SEM, scanning electron microscope; FAME, fatty acid methyl ester

INTRODUCTION

Monoacylglycerols (MAGs) are important types of nonionic amphiphilic emulsifiers that

are widely used in hydrophobic food systems, pharmaceuticals, cosmetics, household

preparations, and chemical industries. MAGs, particularly the saturated ones, exhibit

several advantages, such as excellent emulsifying properties as well as reduced odor and

taste.

The common catalytic preparation of MAGs can be classified into chemical and

enzymatic methods. According to previous studies, the latter approach is usually mild

(Lee et al., 2006; Watanabe et al., 2004). Byun et al. (2007) reported an esterification

scheme of fish oil fatty acids with glycerol in which lipase was used as catalyst. In that

study, MAG content reached 68 wt.% after 72 h of reaction. However, this approach had

several drawbacks, which include long reaction time and high catalyst cost. More

importantly, enzymatic catalysis cannot be applied to produce saturated MAGs because

the high melting point of fully hydrogenated oil may induce the deactivation of certain

kinds of commercial lipases. By contrast, the chemical method is widely used in

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industrial MAG production. In the glycerolysis of fully hydrogenated oil, homogeneous

alkalis, such as sodium hydroxide and potassium hydroxide, are the most commonly used

catalysts (Samios et al., 2009). Studies showed that although different homogeneous

alkalis can be employed in preparing MAGs (Noureddini et al., 2004), such alkalis would

cause undesired saponification. Therefore, the synthetic products require further

neutralization, thereby making the separation process more difficult and the industrial

production costs more expensive (Yee et al., 2011; Kansedo et al., 2009).

Several researchers have previously tried to replace homogeneous catalysts by

heterogeneous ones to catalyzed transesterification in biodiesel production (Melero et al.,

2009; Di Serio et al., 2008; Lotero et al., 2005; Sivasamy et al., 2009). Results showed

that the utilization of heterogeneous catalysts promoted catalytic efficiency and presented

several advantages, such as the prevention of saponification and the process of

neutralization, which requires downstream processing equipment. Consequently, the

separation of catalysts would significantly become more convenient, and the industrial

costs would be reduced (Marchetti et al., 2008).

Corma et al. (1998) studied the production of MAGs by glycerolysis of fats with solid

base catalysts, including some hydrotalcites. However, the free hydrotalcites required a

high reaction temperature (240℃), a high amount of catalyst (4 wt%), and a high mole

ratio of glycerol to vegetable oil (12:1).

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This study employed hydrotalcite loaded with K2CO3 (K2CO3/HT), in the experimental

preparation of MAGs. First, K2CO3 and HT were used to produce K2CO3/HT, which was

then characterized and confirmed by X-ray diffraction (XRD), infrared (IR) spectroscopy,

and scanning electron microscopy (SEM). Then, a series of experiments was conducted

to evaluate the effects of reaction temperature, reaction time, K2CO3/HT loading amount,

and mass ratio of fully hydrogenated palm oil (FHPO) to glycerol on the preparation of

MAGs. Finally, the MAGs were purified by two-stage molecular distillation.

MATERIALS AND METHODS

Materials

FHPO was provided by Cardlo Biochemical Technology Co., Ltd. (Guangzhou, China).

HT was obtained from Tiantang Chemical Co., Ltd. (Shaoyang, Hunan, China). Glycerol

(>99%), acetone (>99.5%), and potassium carbonate (>99%) were purchased from Fuyu

Chemical Co., Ltd. (Tianjin, China).

K2CO3/ HT Preparation

HT, which can be expressed by the formula [Mg1-xAlx(OH)2](CO3)x/n. nH2O, was used as

precursor and supporter because of its alkalescence and double-layered structure

(Cantrell et al., 2005; Trakarnpruk et al., 2008; Xi et al., 2008; Zeng et al., 2008; Antunes

et al., 2008). According to a previously published work ( Jiang et al., 2009), the catalyst

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was prepared as follows: HT (25.0 g) and potassium carbonate (5.0 g) were poured into a

250 mL flask containing 100.0 g of distilled water. The flask was then immersed in oil

bath at 80 °C for 24 h and was only stirred during the first hour. Then, the formed slurry

was dried in an oven for 5 h and calcined at 600 °C for 6 h after grinding. The final solid

base catalyst was expressed as K2CO3/ HT.

Characterization Of K2CO3/HT

K2CO3/HT was characterized by an MSAL XD-2 X-ray diffractometer (Bragg Science

and Technology Co., Ltd., Beijing, China) with Cu Ka radiation (λ = 0.15418 nm) at 36

kV and 20 mA from 10° to 80°. The JSM-6490 scanning electron microscope (JEOL,

Japan) was used to observe K2CO3/HT at a magnification of 20 000. IR spectroscopy was

conducted using a 640-IR spectrometer (Varian, USA), which obtained over 32 scans of

each spectrum in the transmission mode in the range of 4000 cm-1 to 400 cm-1 with a

resolution of 1 cm-1. Thin film samples were used for qualitative IR investigation using

the KBr pellet technique. Potassium, sodium, magnesium, and aluminum contents in the

products were determined by inductively coupled plasma atomic emission spectroscopy

(Optima 2000DV ICP-AES, Perkin Elmer Co., USA).

Composition Of FHPO

The composition of FHPO was identified as fatty acid methyl esters (FAMEs) by the

Agilent GC-7820A chromatograph equipped with a capillary column (DB-Wax, 10 m × 0.

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250 mm i.d., 0.1 µm in film thickness, Agilent Technologies Inc., Palo Alto, CA, USA).

The oil sample was converted into FAMEs by alkaline transesterification based on a

previous study (Wang et al., 2011). The detector temperature was 240 °C. The oven

temperature program was set as follows: initial temperature of 80 °C, increased to 220 °C

at 100 °C/min, and then to 240 °C at 60 °C/min. The solution (0.2 µL) was injected in

split mode with a split ratio of 100:1. All determinations were performed in duplicate,

and the results were expressed as mean values.

Acylglycerol Analysis

The glycerolysis products were analyzed by a gas chromatography (GC) system

equipped with a capillary column (DB-1HT, 15 m × 0. 250 mm i.d., 0.1µm in film

thickness, Agilent Technologies Inc., Palo Alto, CA, USA). The detector temperature was

set to 380 °C. The oven temperature program was set as follows: 50 °C for 1 min, then

increased to 100 °C at a rate of 50 °C/min, then to 220 °C at 50 °C/min, then to 290 °C at

15 °C/min, then increased by 40 °C/min until the temperature reaches 330 °C for 2 min,

and then by 20 °C/min until the temperature reaches 380 °C for 3 min. The solutions for

analysis were composed of 50 mg of the obtained product dissolved in 5 mL of acetone.

Approximately 0.5 µL of the solutions were injected.

The yield of acylglycerols were expressed as the percent content of the corresponding

peak area response compared with the total peak area using a flame ionization detector.

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All determinations were performed in triplicate, and the results were reported as mean ±

standard deviation.

Glycerolysis Reaction

Glycerolysis was performed under different operating conditions, which includes five

mass ratios of FHPO to glycerol (5:1, 10:3, 5:2, 2:1, and 5:3), different K2CO3/HT

loading amounts (FHPO mass = 0.2, 0.4, 0.6, 0.8, and 1.0 wt.%), five reaction

temperatures (170, 180, 190, 200, and 210 °C, and five reaction times (1, 1.5, 2, 2.5, and

3 h).

FHPO was mixed with glycerol and the catalyst in a round-bottom flask. The reaction

was conducted under vacuum pressure (~2000 Pa) using a water ring pump inserted

through a glass condenser with circulating tap water. The reactor was heated in a

thermostatic oil bath. A mechanical impeller with a plastic paddle rotating at 200 r/min

was used to stir the reaction mixture. After the glycerolysis reaction was completed, the

reaction mixture was cooled down and settled into two layers. The upper phase was

composed of acylglycerols, which was then analyzed by GC under the conditions of

MAG analysis. The lower phase primarily included the unreacted glycerol and the

catalyst for the recycle test.

Analysis Of Metal Contents

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Approximately 5.0 g of lower phase and 5.0 g of upper phase were carbonized in an

electric oven for 2 h and then transferred to a Muffle furnace for ashing at 600 °C for 4 h.

The ashed samples were dissolved in 5 mL of nitric acid and diluted to 50 mL by distilled

water. Potassium, magnesium, and aluminum contents in the diluted samples were

determined by ICP-AES. All determinations were performed in duplicate, and the results

were expressed as mean values.

Reactivation Of K2CO3/HT

After the first reaction, the glycerol phase (glycerol and K2CO3/HT) after readding the

amount of glycerol consumed in the previous reaction was continually used in the next

round of glycerolysis under the same conditions to monitor the activity of K2CO3/HT by

comparing the MAG yields. After the third round, the deactivated catalyst was filtered

out of the reaction mixture, and then was reactivated by impregnation in a K2CO3

solution (5 wt.%), carbonation (heated in an electric oven for 2 h to burn the residual

glycerol), and calcination under the catalyst preparation conditions mentioned above.

Then, the activated catalyst was reemployed in the glycerolysis reaction under the

selected conditions. The changes in metal ion composition and crystal structure were

employed to indicate the decreased activity of the recycled K2CO3/HT.

Separation And Purification Of Mags

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A two-stage molecular distillation was performed in an MD80 molecular distillation

equipment (Handway Technology Co., Ltd., Guangzhou, China) to purify the MAGs. In

the first stage, free fatty acids (FFA) and glycerol in the acylglycerols were removed at

an evaporator temperature of 140 °C (Kawala et al., 2002; Cvengros et al., 2000). In the

second stage, the completely purified MAGs were obtained at an evaporator temperature

of 190 °C (Cvengros et al., 2000).

For the first stage of molecular distillation, 50.0 g of MAGs products were transferred to

the head tank and dehydrated at 80 °C until the vacuum reached 30 Pa. The evaporator

temperature, the vacuum, and the knifing rate were set to 140 °C, 0.1 Pa, and 300 r/min,

respectively. The products were separated into two phases: the light phase, which was

composed of fatty acids, and the heavy phase, which was composed of acylglycerols.

For the second stage of molecular distillation, 40.0 g of glycerides from the first

distillation stage were transferred to the head tank and dehydrated at 80 °C until the

vacuum reached 30 Pa. The evaporator temperature, vacuum, and knifing rate were set to

190 °C, 0.1 Pa, and 300 r/min, respectively. The acylglycerols were separated into two

phases: the light phase, which was composed of MAGs, and the heavy phase, which was

composed of diacylglycerols (DAGs) and triacylglycerols (TAGs). The samples of the

light phase were analyzed by GC. All determinations were performed in duplicate, and

the results were reported as mean values.

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RESULTS AND DISCUSSION

Analysis Of FHPO Composition

The FHPO composition was found in the feedstock (Table 1). Only three kinds of

saturated fatty acids, namely, myristic acid, palmitic acid, and stearic acid, were found in

the hard stock. The high content of palmitic acid (64.49 wt.%) indicated that the FHPO

was originally from palm stearin. FHPO is commonly used for the preparation of MAGs

because of its high palmitic acid content.

Characterization Of K2CO3/HT SEM Micrographs Of HT And K2CO3/HT

SEM was conducted to obtain images of K2CO3/HT. Figures 1a and 1b show the SEM

micrographs of the K2CO3/HT at a magnification of 20 000 before and after calcination,

respectively. As illustrated in Figure 1a, the surfaces of K2CO3/HT before calcination

were quite smooth and concrete. The layered structures of HT were also confirmed by the

thin flat crystals and the edges. However, after calcination, the layered structures of HT

became inferior. Figure 1b clearly shows that the morphology of K2CO3/HT is different

from that in Figure 1a. In general, the particle size of K2CO3/HT became larger than HT.

More importantly, needle-like and lepidoblastic crystals in K2CO3/HT were observed in

Figure 1b, indicating that K2CO3 was successfully incorporated into HT. Given that the

HT layered structures were optimized after being loaded by potassium, the specific

surface area increased accordingly (Teng et al., 2010).

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XRD Diffractograms Of HT And K2CO3/HT

Figure 2 shows the XRD diffractograms of calcined K2CO3/HT and HT with changing

diffraction angles. Strong typical HT peaks can obviously be observed at 2θ = 11.8°,

23.3°, 35.1°, 39.5°, 47.5°, 53.4°, and 61.1° in Pattern B, and these peaks confirmed the

double-layered structures of HT (Cantrell et al., 2005; Cavani et al., 1999). After

calcination, the HT layered structures were destroyed, and the calcined K2CO3/HT

presented certain typical features such as reflections at 2θ = 43° and 63°, which

correspond to periclase-like structures (Alvarez et al., 2010). A new crystal was obtained

based on these XRD patterns. This new crystal might consist of multiple metal oxides,

which is a viable reason to explain the excellent catalytic effects of K2CO3/HT on

glycerolysis (Teng et al., 2010).

IR Spectra Of HT And Calcined K2CO3/HT

The IR spectra of calcined K2CO3/HT and HT are depicted in Figure 3. As shown in

Figure 3, the reconstruction of calcined K2CO3/HT induced a recovery of pristine HT

structures despite certain slight variations in peak positions. This result is in good

agreement with the data available in the literature (Gomes et al., 2011; Mokhtar et al.,

2012; Sharma et al., 2007). For example, the presence of both calcined K2CO3/HT and

HT structural hydroxyl groups in the brucite-like layer was confirmed by the appearance

of the band at around 3440 cm−1, as well as the strong bands at around 3440 and 1630

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cm−1, which belonged to the water molecules in the calcined K2CO3/HT and HT.

Moreover, the translation modes of hydroxyl groups, which are primarily influenced by

aluminum and magnesium cations, were also observed in the IR spectra of calcined

K2CO3/HT. The peak at around 1380 cm−1 indicated that the carbonate ions were still

present after calcination.

Production Of Mags By Glycerolysis Reaction Effects Of Reaction Time On The

Production Of Mags

Glycerolysis with FHPO:glycerol mass ratio of 5:2 using 0.8 wt.% K2CO3/HT was

conducted at 200 °C under different reaction time (Figure 4a). The MAG contents in the

acylglycerols were initially low (13.54 wt.%) during the first 1 h. During the next hour,

the MAG contents increased to 44.70 wt.%, which remained stable at around 44 wt.%

after 2 h. This result could be attributed to the acylglycerols reaching equilibrium within

2 h, and prolonging reaction time had marginal effects on the established equilibrium.

Therefore, the reaction time of 2 h was chosen for the subsequent production of MAGs.

Effects Of Reaction Temperature On The Production Of Mags

MAG contents were proportional to reaction temperature, exceeding 43 wt.% at 200 °C

(Figure 4b). The elevated temperature increases the probability of molecular collisions,

which increases the esterification reaction rate. However, a higher reaction temperature

would result in greater energy consumption and increase the tendency toward glycerol

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polymerization, which, according to a previous study, has a strong tendency of occurring

at temperatures exceeding 220 °C (Garti et al., 1981). Thus, the reaction temperature of

200 °C was considered acceptable for the subsequent production of MAGs.

Effects Of K2CO3/HT Loading Amount On The Production Of Mags

The yield of MAGs increased as the K2CO3/HT loading amount increased (Figure 4c).

As shown in Figure 4c, MAG content peaked at 46.80 wt.% when the loading amount of

K2CO3/HT reached 0.8 wt.%. The reaction occurs at the active sites formed in the

catalyst for the reactants. When the number of active sites is totally occupied by enough

reactants, catalysts are no longer required. Excess K2CO3/HT loading would not

contribute to glycerolysis. After considering both the cost and efficiency, the optimum

loading amount of K2CO3/HT was set to 0.8 wt.%.

Effects Of Mass Ratios Of FHPO To Glycerol On The Production Of Mags

The MAG contents peaked at 44.70 wt.% with a 5:2 mass ratio of FHPO to glycerol.

However, this value dramatically declined to below 20 wt.% when the mass ratio

continued to increase from 2:1 to 5:3 (Figure 4d). Theoretically, an excess of glycerol

should accelerate the positive reaction rate, which in turn increases the yield of MAGs.

Nevertheless, a high amount of glycerol in the reaction system may dilute K2CO3/HT and

increase the viscosity, consequently inhibiting the movement of K2CO3/HT between the

glycerol phase and the FHPO phase and decreasing the reaction rate. Consequently, the

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mass ratio of FHPO to glycerol of 5:2 was selected for the subsequent experiment.

According to the results of the experiments, the selected conditions for MAG production

are given as follows: 5:2 mass ratio of FHPO to glycerol, reaction temperature of 200 °C,

reaction time of 2 h, and 0.8 wt.% K2CO3/HT loading amount. Under such conditions,

the yield of MAGs was 46.8 wt.%. Throughout glycerolysis, the contents of MAGs and

DAGs were inversely proportional to the contents of TAGs. In addition, the contents of

FFA remained stable below 2% with K2CO3/HT as catalyst. Similarly, Echeverri et

al.(2011) studied the glycerolysis of soybean oil with glycerol catalyzed by NaOH, and

the yield of MAGs was 40 wt.% to 50 wt.%. However, the glycerolysis catalyzed by

NaOH was more prone to soap formation, and the presence of soaps in crude glycerol

would result in lower reaction rates and contribute to the difficult removal of FFA from

MAGs.

Metal Content

After glycerolysis, the mixture presented two phases. The lower phase primarily included

glycerol, whereas the upper phase was primarily composed of acylglycerols. Potassium,

magnesium, and aluminum contents in the two phases are presented in Table 2. As shown

in Table 3, the total contents of potassium, magnesium, and aluminum, and the mass

ratios of potassium to magnesium to aluminum was the same with K2CO3/HT, indicating

that a small amount of residual K2CO3/HT is present in the products. Some potassium

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(37.89 mg/L) in the upper phase was observed to be leaching to the products. Previous

studies have reported that during the production of biodiesel from sunflower oil catalyzed

by K-solid base catalyst, the potassium was found leaching because of the attack from

the hydroxyl groups in methanol molecules (Alonso et al., 2007). Therefore, the stronger

leaching of potassium observed in this study could be attributed to glycerol, which has

three hydroxyl groups in a molecule compared with the single hydroxyl group in a

methanol molecule.

Reactivation Of K2CO3/HT

The yields of MAGs with K2CO3/HT in the second and third cycle were 42.88 wt.% and

22.06 wt.%, respectively (Figure 5). However, MAG yield rebounded to 49.97 wt.%

when the reactivated K2CO3/HT was used.

According to Table 3, the proportion of Mg to Al was 1.60 in HT and K2CO3/HT before

calcination, and the value reached 1.78 in calcined K2CO3/HT because of the loss of

aluminum. After glycerolysis under the selected conditions, a decrease in the proportion

of Mg to Al was observed; this then recovered to 1.78 through reactivation. This

observation is in accordance with the research of Cantrell et al. (2005) who reported that

a relatively high proportion of Mg to Al is conducive to transesterification because the

incorporation of Mg correlates with the increase in intra-layer electron density, which is

associated with increased basicity. In addition, the proportion of potassium was 2.12,

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indicating that the loading of K2CO3 recovered significantly after reactivation.

Teng et al. (2010) reported that in biodiesel preparation from Jatropha curcas oils

catalyzed by K2CO3/HT, the catalyst could be reused for more than five times with

slightly declining catalytic activity, whereas the two peaks at 43.78° and 63.1° in the

XRD spectrograms became weaker and weaker. Figure 6 shows the XRD spectrograms

of recycled and reactivated K2CO3/HT. As shown in Figure 6, the main peaks of

K2CO3/HT still obviously exist. The peaks at 43.78° and 63.1° of the recycled K2CO3/HT

were weaker than those of the unused K2CO3/HT (Figure 2, Pattern A). By contrast, both

of the two peaks were very strong in the spectrograms of the reactivated K2CO3/HT,

demonstrating that the recycled K2CO3/HT’s catalytic activity was restored after

reactivation, and the crystal strength was regained.

Purification Of Mags

The MAGs obtained under the selected conditions were purified by molecular distillation.

As shown in Table 4, the contents of MAGs more than doubled after the two-stage

molecular distillation (46.80 wt.% to 96.66 wt.%), whereas the contents of DAGs

decreased to 2.95 wt.%, and no residual TAGs were detected. Fregolente et al. (2006)

also introduced a two-step molecular distillation to purify MAGs from an acylglycerol

mixture with relatively high pressure (16 Pa). For the first step in this method, MAGs

and residual glycerol were distilled from the acylglycerol mixture at an evaporator

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temperature of 250 °C. Then, the distillate from the first step was distilled at 170 °C to

remove the residual glycerol to obtain the final product with a purity of 90.88 wt.%.

CONCLUSION

Based on single factorial tests of glycerolysis, the selected conditions for MAG

production are listed as follows: 5:2 mass ratio of FHPO to glycerol, reaction

temperature of 200 °C, reaction time of 2 h, and 0.8 wt.% K2CO3/HT. After the two-stage

molecular distillation, the final product of MAGs with a purity of 96.6 wt.% was

obtained, and the recovery of MAGs was 96.8% after purification. Compared with

homogeneous base catalysts, K2CO3/HT as a heterogeneous solid base catalyst present

numerous advantages, which includes having less by-products, lower costs, the absence

of neutralization, and greater convenience. Furthermore, K2CO3/HT could be recycled by

reactivation, and 49.97 wt.% MAG was produced using the reactivated K2CO3/HT.

FUNDING

The financial support from the Ministry of Science and Technology of People’s Republic

of China under Grant 2011BAD02B04, and the Department of Science and Technology

of Guangdong Province under Grant 2012B091100035, are gratefully acknowledged.

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Table 1. Fatty acid composition of FHPO by GC analysis

Retention time（min） Fatty acid Relative content（%a）

2.30 Myristic acid 1.95

2.83 Palmitic acid 64.49

3.41 Stearic acid 33.56

aValues are means of two replicates.

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Table 2. The contents of potassium, magnesium and aluminum under selected conditions

for glycerolysis in the upper phase, the lower phase by the inductively coupled plasmaa

Content (mg/L) Potassium Magnesium Aluminum

Upper phase 37.89 1.24 1.91

Lower phase 34.37 91.45 51.51

aValues are means of two replicates.

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Table 3. The ratios of potassium, magnesium, aluminum in HT and K2CO3/HT in

different states by the inductively coupled plasma a

Potassium Magnesium Aluminum

HT 0.003 1.60 1

K2CO3/HT before calcination 0.92 1.60 1

K2CO3/HT 0.88 1.78 1

Recycled K2CO3/HT under selected

conditions for glycerolysis

0.08 1.52 1

Reactivated K2CO3/HT 2.12 1.78 1

aValues are means of two replicates.

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Table 4. Yield of the MAGs before and after distillation by GC analysisa

Content (wt-%) FFA MAGs DAGs TAGs

Crude MAGs under selected conditions for

glycerolysis

0.95 46.80 32.25 20.00

Light phase (Purified MAGs) 0.39 96.66 2.95 0.00

aValues are means of two replicates.

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Figure 1. SEM micrograph (20000×) of K2CO3/HT: a: K2CO3/HT before calcination; b:

K2CO3/HT after calcination.

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Figure 2. X-RD spectrum of K2CO3/HT: A- Calcined K2CO3/HT; B- HT.

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Figure 3. IR spectrum of Calcined K2CO3/HT and HT.

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Figure 4. (a): Effects of reaction time on the production of MAGs; (b): Effects of

reaction temperature on the production of MAGs; (c): Effects of K2CO3/HT loading

amount on the production of MAGs; (d): Effects of mass ratios of FHPO to glycerol on

the production of MAGs

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Figure 5. Content of MAGs catalyzed by K2CO3/HT with different states a (a Values are

means of two replicates).

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Figure 6. X-RD spectrum of recycled and reactivated K2CO3/HT.

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