Hydrolysis - Hydrogenation of soybean oil and tallow

doi:10.4236/ns.2011.37074

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Vol.3, No.7, 530-534 (2011) Natural Science

http://dx.doi.org/10.4236/ns.2011.37074

Hydrolysis—Hydrogenation of soybean oil and tallow

Gisel Chenard Díaz1, Rodolfo Salazar Perez1, Neyda de la Caridad Om Tapanes2, Donato

Alexandre Gomes Aranda1, Angel Almarales Arceo1

1GREENTEC Laboratory, Escola de Química, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil;

*Corresponding Author: [email protected]

2Department of Industrial Production, State University of the West in Brazil, Rio de Janeiro, Brazil;

*Corresponding Author:[email protected]

Received 12 March 2011; revised 15 April 2011; accepted 25 April 2011.

ABSTRACT

Hydrolysis reactions are of major importance to

the oleochemical industry in the production of

fatty acid and their derivates. Hydrolysis of trig-

lyceride from vegetable oil has been studied

under various parameters such as: heteroge-

neous catalyst, temperature, reaction time and

agitation speed. During the hydrolysis of soy-

bean oil and tallow using nickel catalysts on

alumina support was verified that the glycerol

produced worked as hydrogen donor, allowing

the hydrogenation of unsaturated fatty acids

produced. Maximum conversion was achieved

in 3 hours, catalysts 25% NiO/Al2O3, temperature

of 250°C and 270°C and 250 rpm.

Keywords: Hydrolysis; Soybean Oil; Tallow;

Hydrogenation; Saturated Fatty Acid; Selectivity

1. INTRODUCTION

Vegetable oils are composed by triglycerides. Every

triglyceride, or fat, contains three fatty acid chains attach

to a single glycerol molecule. These fatty acid chains can

be classified as saturated, monounsaturated and polyun-

saturated, depending on the type of chemical bonds pre-

sent. The hydrolysis of triglycerides produces fatty acids

and glycerol [1-4]. Saturated fatty acids have high rele-

vance in the food and oleochemical industries.

The glycerol can be used for hydrogen production by

catalytic reforming reaction using nickel or platinum

catalysts supported on alumina and silica [5].

This paper presents studies and results on producing

saturated fatty acid trough catalytic hydrolysis of soy-

bean oil and tallow. The catalysts used in the heteroge-

neous reactions were nickel supported on gamma alu-

mina, synthesized by the method of wet impregnation.

The reaction is shown in Figure 1.

2. EXPERIMENTAL

2.1. Reactants and Preparation of Catalysts

The raw materials used in this study are soybean oil

and tallow. The fatty acid profile of soybean oil and tal-

low are shown in Table 1.

The catalysts used in the heterogeneous reactions

were nickel supported on gamma alumina (5% NiO/

Al2O3, 10% NiO/Al2O3 and 25% NiO/Al2O3). To prepare

the catalyst of nickel supported on alumina was used as

metallic precursor a nickel nitrate salt (Ni(NO3)2.6H2O)

97.0% purity). A commercial alumina (100% purity) was

used as a catalyst support. In each experiment, 5, 10 and

25% of metal was loaded on alumina using wet impreg-

nation method.

Catalyst Characterization

The synthesized catalysts were characterized by tex-

tural analysis techniques, X-ray diffraction (DRX) and

X-ray fluorescence spectrometry (XRF).

Samples were analyzed using a commercial XRF in-

strument. The chemical compositions of Ni/Al2O3 cata-

lysts were measured and the results confirmed the cer-

tain amount of active metals on catalyst supports (Table

2).

Surface areas of catalysts were determined by apply-

ing the Brunauer-Emmett-Teller method (BET), for N2

physisorption at liquid nitrogen temperature (77 K). The

pore volume and average pore diameter were calculated

applying the Barrett-Joyner-Halenda (BJH) method [6].

Table 3 shows the results.

This area reduction is possibly due to partial pores

blockage of the support by the particles of nickel oxide

[7].The calcined catalysts displayed an isotherm of type

IV with H3-type hysteresis.

XRD patterns of the catalysts displays two crystalline

phases, one related to γ-alumina with amorphous struc-

ture characteristic (JCPDS 49-0063) and the other the

bunsenite NiO with cubic structure and space group

Fm3m (JCPDS 47-1049). In the case of catalyst 5% NiO

G. C. Díaz et al. / Natural Science 3 (2011) 530-534

531

Figure 1. Hydrolysis and hydrogenation of triglycerides.

Table 1. Fatty acid profile of raw materials.

Fatty acid profile Soybean oil Content %

(m/m)

Tallow Content %

(m/m)

Myristic (C14:0) < 0,5 1.0 - 6.0

Palmitic (C16:0) 7.0 - 14.0 20.0 - 37.0

Stearic (C18:0) 1.4 - 5.5 25.0 - 40.0

Oleic (C18:1) 19.0 - 30.0 31.0 - 50.0

Linoleic (C18:2) 44.0 - 62.0 1.0 - 5.0

Linolenic (C18:3) 4.0 - 11.0 -

Table 2. XRF-results of the composition of catalysts.

Catalyst NiO (%) Al2O3 (%) Impurities

5% NiO/Al2O3 5.33 94.62 0.05

10% NiO/Al2O3 11.47 88.47 0.06

25% NiO/Al2O3 25.73 73.88 0.09

Table 3. Morphologic characteristic of catalysts obtained.

Catalyst BET

(m2/gcat)

Pore volume

(cm3/gcat)

Average pore

diameter (ǻ)

5% NiO/Al2O3 175.38 0.48 85.68

10% NiO/Al2O3 164.56 0.44 84.60

25% NiO/Al2O3 160.53 0.40 84.06

phase has peaks less visible because it has the least

amount of NiO in the catalyst (Figure 2).

2.2. Reaction Procedure – Hydrolysis of

Soybean Oil and Tallow

Reactions were performed in a stainless steel 300 mL

batch reactor (Parr Instruments 4842), maximum pres-

sure of 3000 psi and equipped with a sample withdrawal,

stirring, and heating system. Stirring velocity was kept

constant (250 rpm). Reaction mixture consisted of 100 g

of raw material and 100 g of water, providing a water/

raw material molar ratio of 1.

Reagents were introduced together with the appropri-

ated catalyst mass (10% w/w, in relation raw material)

and time of reaction (1 and 3 hours) was considered

when required temperature (250˚C and 270˚C) was

reached. Products were obtained after 1 and 3 hours of

the reaction.

Figure 2. XRD patterns of commercial Al2O3, commercial nio

and synthesized NiO/Al2O3 catalysts.

2.3. Product Analysis

The goal is to verify the hydrogenation of fatty acids

formed, for this, three analyses will be conducted to de-

fine the production of fatty acids. These are: Free fatty

acid content (FFA), total glycerol and iodine value.

The composition of fatty acid was determinated by

gas chromatography (ASTM D 6584, EN ISO 14105,

EM ISSO 14106). It was also determinated total glycerol

and iodine value. Enzymatic method was used to evalu-

ate total glycerol of samples [8].

3. RESULTS AND DISCUSSION

Hydrolysis results of soybean oil and tallow at 250

and 270˚C in one hour of reaction are shown in the Ta-

bles 4, and in three hours in the Tables 5. It is noted in

the tables that in one hour of reaction, the values of acid-

ity and iodine are very similar for all experiments (cata-

lyzed and not catalyzed). This effect was observed for

both raw materials.

Results obtained in the reactions without catalyst and

catalyzed with 5 and 10% nickel oxide, did not change

significantly when increasing the reaction time of 1 hour

for 3 hours. (Tables 4 and 5).

In experiments using 25% NiO/Al2O3 were observed

changes in fatty acid profiles produced. After 3 hours of

reaction, iodine value decreased due to saturation of

double bonds (Tables 5). The iodine value decreased 47

and 63% for hydrolysis of soybean oil at 250 e 270C

respectively, and 52 and 70% for tallow [9].

The hydrogenation in-situ was confirmed with the gas

chromatograph analysis. The chromatogram suggest that

occurs preferential hydrogenation of more unsaturated

fatty acids. The fatty acid composition of the hydrolysis

products of soybean oil are reported in Figure 3 and for

tallow in Figure 4.

It was observed increase of saturated fatty acids in the

hydrolysis of soybean oil, 48 and 66% in reactions at

G. C. Díaz et al. / Natural Science 3 (2011) 530-534

532

Table 4. Soybean oil and Tallow hydrolysis (Reaction time: 1h, Catalysts: 5, 10 and 25% of NiO/Al2O3).

5%NiO/Al2O3 10%NiO/Al2O3 25% NiO/Al2O3 Without catalyst

250˚C 270˚C 250˚C 270˚C 250˚C 270˚C 250˚C 270˚C

Soybean oil:

Glycerol content (%) 2.11 1.24 0.49 0.48 1.36 0.30 1.12 1.01

Acidity (%) 90.57 89.89 89.67 89.89 88.85 87.55 91.25 93.47

Iodine (mgI2/g) 132.22 124.41 130.66 133.01 122.44 139.43 136.82 140.14

Tallow:

Glycerol content (%) 0,01 0,00 0,52 0,14 0,26 0,32 0,37 0,32

Acidity (%) 85.12 88.53 80.26 87.14 89.16 87.77 84.04 89.05

Iodine (mgI2/g) 46,38 37,98 39,94 32,47 41,81 41,50 46.7 42,08

Table 5. Soybean oil and Tallow hydrolysis (Reaction time: 3h, Catalysts: 5, 10 and 25% of NiO/Al2O3).

5%NiO/Al2O3 10%NiO/Al2O3 25%NiO/Al2O3 Without catalyst

250˚C 270˚C 250˚C 270˚C 250˚C 270˚C 250˚C 270˚C

Soybean oil:

Glycerol content (%) 2.32 1.04 1.16 1.00 0.43 0.85 1.38 0.89

Acidity (%) 90.04 86.34 82.38 83.35 87.57 85.50 88.67 87.70

Iodine (mgI2/g) 152.25 141.89 139.72129.91 70.91 47.70 135.24 130.36

Tallow:

Glycerol content (%) 2.09 1.52 0.60 0.30 0.17 0.15 0.42 0.44

Acidity (%) 85.84 86.34 93.45 85.92 87.55 93.55 87.04 83.72

Iodine (mgI2/g) 41.95 47.48 44.25 35.89 14.64 10.62 30.39 35.59

0,00

10,00

20,00

30,00

40,00

50,00

60,00

70,00

80,00

C16:0

C18:0

C18:1

C18:2

C18:3

3ho u r1hour 2hour

ReactionTime

FattyAc i dComposition(% )

0,00

10,00

20,00

30,00

40,00

50,00

60,00

C16:0

C18:0

C18:1

C18:2

C18:3

3hour

1hour 2hour

ReactionTime

Fat tyAci dCompositio n(% )

(a) (b)

Figure 3. Fatty acid composition of hydrolysis – hydrogenation of soybean oil, using 25% NiO/Al2O3, reaction time: 3 h. (a)

Temperature: 250˚C (b) Temperature: 270˚C.

0,00

5,00

10,00

15,00

20,00

25,00

30,00

35,00

40,00

45,00

C16:0

C18:0

C18:1

C18:2

3hour

1hour 2hou r

ReactionTime

Fat t yAc i dC ompo s ition(%)

0,00

5,00

10,00

15,00

20,00

25,00

30,00

35,00

40,00

45,00

50,00

C16:0

C18:0

C18:1

C18:2

3ho ur

1hour 2ho ur

ReactionTime

FattyAc i dComposition(%)

(a) (b)

Figure 4. Fatty acid composition of hydrolysis – hydrogenation of tallow at 250C, using 25% NiO/Al2O3, reaction time: 3

h. (a) Temperature: 250˚C (b) Temperature: 270˚C.

G. C. Díaz et al. / Natural Science 3 (2011) 530-534

533

250 and 270˚C, respectively, being 17 and 20% in reac-

tions with tallow.

Changes in fatty acid profile is due to the hydrogena-

tion of double bonds of fatty acids produced. The glyc-

erol formed during the hydrolysis of triglycerides in soy-

bean oil and tallow acts as hydrogen donor. The catalytic

reforming of glycerol allowed in-situ generation of hy-

drogen, which is attracted to and reacts rapidly with the

double bonds.

During the 3 hours of hydrolysis of soybean oil, using

catalyst 25% NiO/Al2O3, are hydrogenated linoleic acid

and oleic acid [10]. Studies of the kinetics of hydrogena-

tion of these acids show that the rate of hydrogenation of

linoleic acid is greater than oleic and stearic [11-13].

Geometry configuration, chemical and physical char-

acteristics of catalyst will determine the selectivity, that

is possible observe by selectivity ratio of different fatty

acids.

Selectivity Hydrogenation means that hydrogen is

added first to the most unsaturated fatty acids. The high

selectivity denotes low level of polyunsaturated fatty

acids and high level of monounsaturated. The selectively

hydrogenated product is more resistant to oxidation due

to the preferential hydrogenation of polyunsaturated ac-

ids. In this study, selectivity can be defined as the con-

version of the linolenic acid to oleic acid, compared to

the conversion of linoleic acid to stearic acid.

Linolenic LinoleicOleicStearic

K1, K2 and K3 are kinetic constants.

It is observed that in the hydrolysis of soybean oil, li-

noleic acid was completely hydrogenated (more to 95%),

this results demonstrates the high selectivity of hydro-

genation. Similar result was shown in the reaction with

tallow, transforming linoleic acid into oleic acid.

To corroborate quantitatively these results were cal-

culated the selectivities for hydrogenation of linoleic and

linolenic acids in the following reactions:

Table 6. SR of linoleic and linolenic acids during hydrolysis – hydrogenation of soybean oil and tallow at 250 and 270˚C, using 25%

NiO/Al2O3.

Temperature: 250C 270C

Reaction time (hours): 1 h 2 h 3 h 1 h 2 h 3 h

Soybean oil:

Linoleic acid

Lo 52.63 52.63 52.63 48.52 48.52 48.52

S 4.00 8.00 14.23 5.00 16.00 33.18

So 3.52 3.52 3.52 4.13 4.13 4.13

K2 = 1 – Lo 47.37 47.37 47.37 51.48 51.48 51.48

K3 = S – So 0.48 4.48 10.71 0.88 11.88 29.05

SR =K2/K3 98.22 10.57 4.42 58.83 4.33 1.77

Linolenic acid

Lno 2.28 2.28 2.28 3.75 3.75 3.75

O 31.00 40.00 69.23 31.90 38.00 51.29

Oo 30.29 30.29 30.29 31.30 31.30 31.30

K1 = 1 – Lno 97.72 97.72 97.72 96.25 96.25 96.25

K2 = O – Oo 0.71 9.71 38.93 0.60 6.70 19.98

SR =K1/K2 138.59 10.07 2.51 161.49 14.37 4.82

Tallow:

Linoleic acid

Lo 1.18 1.18 1.18 0.96 0.96 0.96

S 28.50 32.00 39.01 28.73 31.90 43.12

So 27.95 27.95 27.95 28.18 28.18 28.18

K2 = 1 – Lo 98.82 98.82 98.82 99.04 99.04 99.04

K3 = S – So 0.55 4.05 11.06 0.54 3.72 14.93

SR =K2/K3 181.21 24.43 8.94 182.22 26.65 6.63

G. C. Díaz et al. / Natural Science 3 (2011) 530-534

534

- Hydrolysis of soybean oil at 250˚C and 270˚C, using

25% NiO/Al2O3 as catalyst, at 1, 2 and 3 hours of reac-

tion time.

- Hydrolysis of tallow at 250˚C and 270˚C, using 25%

NiO/Al2O3 as catalyst, at 1, 2 and 3 hours of reaction

time.

Linoleic and linolenic acids selectivity was estimated

from the selectivity ratio (SR). SR was calculated using

Allen’s method [14] as original proposed by Albright

[15].

SR is defined as K2/K3, where K2 = l – Lo, K3 = S – So.

Lo and So represent the linoleic and stearic acid contents

in the original raw material and L and S in the hydro-

genated sample. In the same manner the selectivity ratio

(SR) regarding linolenic acid is calculated by: SR=K1/K 2,

K1 = 1 – Lno, K2= O – Oo, Lno and Oo represent the lino-

lenic and oleic acid contents in the original raw material

and Ln and O in the hydrogenated sample. The results

for soybean oil and tallow are reported in Table 6.

During the hydrogenation of raw materials the selec-

tivity ratios (SR) were high, thus can be assumed that the

reactions were selective under these conditions.

The selectivity can be increased with the temperature,

or by increasing the pressure and agitation. Analyzing

the influence of temperature on SR, it is observed that

increasing the temperature of the reaction of soybean oil

using catalyst 25% NiO/Al2O3 decreases the selectivity

of linoleic acid and increases the selectivity of linolenic

acid. In comparison, the temperature has not significant

influence on the reaction with tallow.

Results of high selectivity in hydrogenation of linoleic

acid and linolenic acid were observed only in reactions

catalyzed by 25% NiO/Al2O3, it is known that commer-

cially employed Ni catalyst has a limited linoleic selec-

tivity [15].

4. CONCLUSIONS

The hydrolysis of soybean oil and tallow were studied

in this paper. Hydrogenation occurs in-situ during the

hydrolysis, producing large amount of saturated and

mono unsaturated fatty acids, such as stearic and oleic

acids. These effects were best manifested under 3 hours

of the reaction and with the catalysts 25% NiO/Al2O3.

The glycerol formed during the hydrolysis behaves as

a hydrogen donor. The reform of the glycerol generates

the in-situ hydrogen, hydrogenating the fatty acids pro-

duced. High hydrogenation selectivity of linoleic and

linolenic acid were observed in the reactions using 25%

NiO/Al2O3. It was not observed hydrogenation of un-

saturated fatty acids during the hydrolysis using 5 and

10% NiO/Al2O3.

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