Artigo publicado nos anais do Congresso Brasileiro de Macaúba, em 2013.

1. I Congresso da Macaúba: Consolidação da Cadeia Produtiva
Centro Universitário de Patos de Minas, 5 a 7 de novembro de 2013.
ETHYLIC ESTERIFICATION OF FREE FATTY ACIDS CONTENT IN MACAUBA 1 PALM OIL (ACROCOMIA aculeata) CATALYZED BY CATIONIC RESINS 23
DANIEL BASTOS DE REZENDE1; MARIA HELENA CAÑO DE ANDRADE1; VÂNYA 4 MÁRCIA DUARTE PASA1 5
6
INTRODUCTION 78
The classic process for biodiesel production is based on a reaction called transesterification, 9 in which a vegetable oil or animal fat, consisting mainly of triacylglycerols, reacts with alcohol 10 (methanol, ethanol or other short-chain alcohol) in the presence of a catalyst generating molecules 11 of biodiesel and glycerol (KNOTHE et al., 2005). For economic and technical reasons, it is used a 12 homogeneous alkaline catalyst, usually sodium hydroxide or sodium methoxide (MIAO et al., 13 2009). Despite of the technical simplicity, there are restrictions in using alkali homogeneous 14 catalyst, such as the use of low acidity raw material, up to 1.0% w/w of oleic acid, and low water 15 content (NEIJI et al., 2009). 16
Macauba palm is a native perennial tree, largely found in Minas Gerais State and other 17 regions in Brazil, with high oil productivity (4000-5000 kg/ha). However, the extractive way of 18 harvest generates a raw material of high acidity, thus not suitable for biodiesel producing by 19 conventional processes (COSTA et al., 2009). 20
Esterification reactions catalyzed by cationic resins have been tested to reduce de acidity of 21 the oil, reacting the free fatty acids with an alcohol and producing a akyl ester. In the present study, 22 commercial cationic resin Purolite CT275DR was tested as catalysts for the esterification of free 23 fatty acids contained in an Macauba palm oil, extracted from the pulp of the fruit of Macauba palm 24 tree, with acidity of 40.8% w/w of oleic acid. The alcohol used in this study was the ethanol. The 25 cationic resin PK208 from Mitsubishi and Methanol were used just for comparison purposes. 26 27
MATERIAL AND METHODS 28 29
The Macauba pulp oil with acidity of 40.8% w/w was supplied by the Macauba Laboratory 30 installed on the Chemical Engineering Department of the Federal University of Minas Gerais. The 31 alcohols used for esterification were the ethanol 99.3% and the methanol 99.8%. The cationic resins 32 evaluated as catalyst were the CT275DR manufactured by Purolite Ion Exchange Resins and the 33 PK208 manufactured by Mitsubishi Chemical Corp., with exchange capacity of 6.2 x 103 and 1.2 x 34 103 meq/m3. 35
1 Federal University of Minas Gerais – daniel.rezende@fiat.com.br; cano@deq.ufmg.br; vanya@ufmg.br
1

2. I Congresso da Macaúba: Consolidação da Cadeia Produtiva
Centro Universitário de Patos de Minas, 5 a 7 de novembro de 2013.
A rotary evaporator whose vertical condenser and condensate collecting flask were replaced 36 by a Liebig condenser, was used as a reactor, as shown in Figure 1. The reactor system was 37 maintained in a bath with a controlled temperature. After the reaction, the resins were removed by 38 vacuum filtration, the alcohol was recovered by vacuum distillation and phase separation was 39 promoted by centrifugation. 40 41
Figure 1: Schematic representation of the rotary reactor, used in this study. 42 43
The free fatty acids conversion into alkyl esters was evaluated by gas chromatography (GC) 44 and acid-base titration. The deacidification tests followed a design of experiments with three 45 factors, molar rate alcohol:oil, reaction time and temperature, and two levels, using values based on 46 preliminary tests. The design of experiments is shown in Table 1, reactions E01 to E08. The 47 software Minitab 14 was used to evaluate de results. The amount of resins used in all tests was 20% 48 w/w of the total weight of reagents and catalyst, according to preliminary tests. Under the same 49 conditions of reaction E08, new reactions have been proposed for evaluating the PK208 resin and 50 the use of methanol, E09 and E10, just for comparison purposes. 51 52
Table 1: Esterification tests using Macauba pulp oil with an initial acidity of 40.8% w/w. 53
#
Alcohol
Resin
Molar rate alcohol:oil
Time (hours)
Temp. (°C)
E01
Ethanol
CT275DR
10
6
60
E02
Ethanol
CT275DR
10
6
90
E03
Ethanol
CT275DR
20
6
60
E04
Ethanol
CT275DR
10
8
90
E05
Ethanol
CT275DR
10
8
60
E06
Ethanol
CT275DR
20
6
90
E07
Ethanol
CT275DR
20
8
60
E08
Ethanol
CT275DR
20
8
90
E09
Ethanol
PK208
20
8
90
E10
Methanol
CT275DR
20
8
90
1 Federal University of Minas Gerais – daniel.rezende@fiat.com.br; cano@deq.ufmg.br; vanya@ufmg.br
2

3. I Congresso da Macaúba: Consolidação da Cadeia Produtiva
Centro Universitário de Patos de Minas, 5 a 7 de novembro de 2013.
RESULTS AND DISCUSSION 54 55
The results of the esterification experiments are presented in Figure 2. According to acidity 56 values, the highest conversion was achieved in the most extreme condition tested, corresponding to 57 the reaction E08, which is comparable to the result obtained by reacting E04, with the same 58 conditions of temperature and reaction time, but with a lower molar ratio alcohol:oil. According to 59 the statistical analysis of the experiments, the acidity is significantly influenced only by 60 temperature, considering statistical significance at 5%. 61 62 63
Figure 2: Results of esterification reactions in order of decreasing acidity. 64 65
Comparing the resins, the results of E08 and E09 indicate a better performance with the use 66 of Purolite resin. This conclusive result can be associated with the exchange capacity parameter that 67 shows the quantity of the ion-exchangeable groups present in the resin. A design of experiments 68 comparing both resins must be performed to assure that assertion. 69
Considering the temperatures of 90 °C for ethanol and methanol tests, E08 and E10, the 70 results indicate satisfactory levels of acidity reduction with a slight advantage of ethanol on 71 methanol performance, according to acidity values. Considering the importance of producing 72 biodiesel from renewable sources, this result is quite satisfactory. 73
1 Federal University of Minas Gerais – daniel.rezende@fiat.com.br; cano@deq.ufmg.br; vanya@ufmg.br
3

4. I Congresso da Macaúba: Consolidação da Cadeia Produtiva
Centro Universitário de Patos de Minas, 5 a 7 de novembro de 2013.
Concerning the reusability of the resin, the conversion of the free fatty acids remained close 74 to the original value after five batches, washing the resin with ethanol between the reactions. More 75 detailed study regarding the reusability of the resin is being carried out. 76 77
CONCLUSIONS 78 79
Esterification reactions catalyzed by cationic resins achieved satisfactory reduction in the oil 80 acidity in a sample of macauba pulp crude oil with initial acidity of 40.8% w/w. The largest 81 reduction was achieved in the most extreme condition tested, the molar ratio ethanol:oil of 20:1, 82 bath temperature of 90 °C and reaction time of 8 hours, resulting in a final acidity of 2.2% w/w. 83 Better results were achieved with resin Purolite CT275DR than with Mitsubishi PK208 because of 84 its higher ion exchange capacity. It was observed that temperature is a key factor in the reaction 85 efficiency. 86
It was showed that the cation exchange resins can be an alternative with great potential as 87 catalysts for the esterification of free fatty acids, which can be used as a pre-treatment of raw 88 materials with high acidity in biodiesel production. 89 90
REFERENCES 91
92
COSTA, M. A., SILVA, P. S. C., VALLE, P. W. P. A., 2009. Bioenergia: Cadeia Produtiva e Co-93 produtos em Minas Gerais. Instituto de Estudos Pró-Cidadania – PRÓ-CITTÀ/SECTES, Belo 94 Horizonte. 95
KNOTHE, G., VAN GERPEN, J., KRALL, J., 2005. The Biodiesel Handbook. AOCS Press, 96 Champaign, Illinois. 97
MIAO, X., LI, R., YAO, H., 2009. Effective acid-catalyzed transesterification for biodiesel 98 production. Energy Conver Manage, doi:10.1016/j.enconman.2009.06.021. 99
NEIJI, S. B., TRABELSI, M., FRIKHA, M. H., 2009. Esterification of Fatty Acids with Short-100 Chain Alcohols over Commercial Acid Clays in a Semi-Continuous Reactor. Energies, 2009, 2, 101 1107-1117; doi:10.3390/en20401107. 102
1 Federal University of Minas Gerais – daniel.rezende@fiat.com.br; cano@deq.ufmg.br; vanya@ufmg.br
4