Transesterification of methylbenzoate with alcohols catalyzed by natural phosphate

Article abstract of DOI:10.1080/00397910600591508

Transesterification of methylbenzoate with various alcohols was catalyzed by natural phosphate with or without solvent in heterogeneous media. The molar ratio of alcohol/ester, solvent effect, and weight of catalyst effect have been studied. We have found that the nature of alcohol and the reaction temperature play an important role in the transesterification process. The catalyst can be regenerated and reused without lost of activity. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910600591508

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Transesterification of Methylbenzoate with
Alcohols Catalyzed by Natural Phosphate
Fathallaah Bazi a , Hanane El Badaoui a , Samira Sokori a , Soumia Tamani a ,
Mohamed Hamza a , Saïd Boulaajaj a & Saïd Sebti a
a Laboratoire de Chimie Organique Catalyse et Environnement , Université
Hassan II‐Mohammedia, Faculté des Sciences Ben M′Sik , Casablanca,
Morocco
Published online: 21 Aug 2006.
To cite this article: Fathallaah Bazi , Hanane El Badaoui , Samira Sokori , Soumia Tamani , Mohamed Hamza ,
Saïd Boulaajaj & Saïd Sebti (2006) Transesterification of Methylbenzoate with Alcohols Catalyzed by Natural
Phosphate, Synthetic Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 36:11, 1585-1592
To link to this article: http://dx.doi.org/10.1080/00397910600591508
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Synthetic Communicationsw, 36: 1585–1592, 2006
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910600591508
Transesterification of Methylbenzoate with
Alcohols Catalyzed by Natural Phosphate
Fathallaah Bazi, Hanane El Badaoui, Samira Sokori,
Soumia Tamani, Mohamed Hamza, Sa¨ıd Boulaajaj,
and Sa¨ıd Sebti
Laboratoire de Chimie Organique Catalyse et Environnemen0t,
´ ´
Universite Hassan II-Mohammedia, Faculte des Sciences Ben M Sik,
Casablanca, Morocco
Abstract: Transesterification of methylbenzoate with various alcohols was catalyzed
by natural phosphate with or without solvent in heterogeneous media. The molar
ratio of alcohol/ester, solvent effect, and weight of catalyst effect have been studied.
We have found that the nature of alcohol and the reaction temperature play an
important role in the transesterification process. The catalyst can be regenerated and
reused without lost of activity.
Keywords: Heterogeneous catalysis, natural phosphate, regeneration, transesterification
The transesterification is an important synthetic process used as an alternative
method to synthesize various carboxylic esters.[1] It has wide academic as well
as industrial applications. The transesterification reaction is an essential part of
the manufacturing process of polyethylene terephtalate.[2] It has also
been applied to produce biodiesel.[3,4] In this reaction, the carboxylic ester
is transformed into others through interchange of the alkoxy moiety.
Catalysts accelerate the equilibrium process; strong Brønsted acid or base
catalysts are usually used.
Received in Poland October 6, 2005
¨
Address correspondence to Saıd Sebti, Laboratoire de Chimie Organique Catalyse
´
´
et Environnement, Universite Hassan II-Mohammedia, Faculte des Sciences Ben
M0Sik B.P. 7955, 20702 Casablanca, Morocco. Tel.: þ 212 61 46 48 19; Fax: þ212
22 24 96 72; E-mail: saidsebti@yahoo.fr and s.sebti@univh2m.ac.ma
1585

1586
F. Bazi et al.
In a traditional homogeneous phase, the separation and recovery of the
catalysts is the main problem. In contrast, the development of active solid
catalysts is highly desirable in view of the increasing demands of green
and sustainable chemistry. In these conditions, the catalyst is easily
recovered and reused for the next reaction. In recent years different studies
have been conducted on the transesterification reaction promoted by hetero-
geneous catalysts such as zeolites,[5–7] clays,[8,9] TiO2/SiO2,[10] polymer-
supported lipase,[11] Mo-ZrO2,[12] Amberlyst-15,[13] and hydrotalcite.[14]
Because of the high cost or unavailability of the catalysts, their use on large
and industrial scales is still restricted. The natural heterogeneous catalysts
have recently attracted increasing interest. We have developed interesting
new catalysts based on natural phosphate (NP). This available ore has been
shown to be an active catalyst or support for many organic reactions such
as Knoevenagel condensation,[15] Claisen–Schmidt condensation,[16–19]
Michael
addition,[20–22]
Fridel–Crafts
alkylation,[23]
nucleoside
synthesis,[24] and flavanones synthesis.[25]
In the connection with our interest in the exploitation of phosphate
catalysts, we undertook the study of the transesterification reaction. In this
present article, the catalytic activity of NP is investigated in the transesterifi-
cation of the methylbenzoate with various alcohols (Scheme 1).
Natural phosphate comes from an extracted ore in the region of
Khouribga (Morocco). The fraction of 100–400-mm grain size has been
isolated, washed with water, calcined at 9008C for 2 h, washed again,
calcined at 9008C for 0.5 h, and ground (63–125 mm) to give the NP
catalyst. It was identified by X-ray diffraction, IR spectroscopy, and
chemical analysis. Surface area was determined by the BET method from
the adsorption–desorption isotherm of nitrogen (S ¼ 1.4 m2 g21) and total
pore volume was 0.005 cm3 g21. The acidic properties of NP have been
demonstrated in the Friedel–Crafts reaction.[15] Indeed, the monoalkyl
compounds of benzene and toluene have been obtained with yields of 42%
(24 h) and 91% (2 h), respectively, in the presence of NP.
As a test for our system, we examined the catalyzed reaction between
methyl benzoate and butanol to determine suitable reaction conditions. The
carboxylic esters with alcohols and catalyst were heating in toluene
medium. The reaction was monitored by GC. First, the solvent effect was
investigated using 0.1 g of NP, 2 mmol of methylbenzoate, 11 mmol of
butanol, and 3 ml of solvent. The conversions of methylbenzoate were 100,
Scheme 1.

Transesterification of Methylbenzoate
1587
84, 46, 31, 30, and 15% with toluene, hexane, diethylether, dichloromethane,
DMSO, and chloroform, respectively, after 48 h of reaction time. In the case of
cyclohexane, CCl4, THF, and dioxane, no transformation was observed. We
have chosen to continuous our study with toluene.
We have also studied the weight effect of NP. We have found that after
24 h of reaction time, the conversions were 41, 66, and 96% using 0.05, 0.1,
and 0.2 g of NP, respectively. Increasing the reaction time from 24 h to 48 h
caused reduction of NP weight and further increase of ester conversion.
Thus, with 0.01, 0.03, 0.05, 0.07, and 0.1 g of NP, the conversions obtained
were 27, 42, 84, 91, and 100%, respectively. It is well known that transester-
ification such as esterification is an equilibrium process that needs a large
excess of alcohol to be accomplished. Generally, the reaction was
conducted under refluxing conditions to remove the alcohol formed from
the reaction system. In our case, we have carried out the reaction without
removal of the methanol formed. The starting molar ratio of alcohol/ester
was studied. It can be seen from Figure 1 that methylbenzoate conversion
increases as the excess of butanol increases. Total conversion was obtained
using the molar ratio of butanol/methylbenzoate of 11/2.
The kinetic curve of methylbenzoate conversion, using optimum con-
ditions of 2 mmol of carboxylic ester, 11 mmol of butanol, 0.1 g of NP, and
3 ml of toluene (Figure 2) shows that the total conversion was obtained
after 48 h of reaction time.
The interest in the catalyst increases significantly when it can be reused.
Thus, we have carried out the transesterification, and the isolated catalyst was
reused without any treatment. The conversion decreased slightly and after four
uses, a conversion of only 30% of methylbenzoate was obtained. On the other
hand, the good stability of NP allows performing regeneration by a simple
Figure 1. Molar ratio of alcohol/ester effect in the transesterification of methyl-
benzoate with butanol catalyzed by NP.

1588
F. Bazi et al.
Figure 2. Kinetic curve of the transesterification of methylbenzoate with butanol
catalyzed by NP.
calcination treatment (7008C, 30 min) of the used catalysts without altering the
catalytic properties (Table 1).
Table 1. Reuse and regeneration of NP
Conversion (%)
With NP
reused
With NP
regenerated
Cycle
Fresh
100
89
100
98
1
2
3
71
36
96
95
To explore the scope of the present
catalytic system, the transesterification
of methylbenzoate with various alcohols
was investigated (Table 2).
As can be seen, the nature of alcohol affects the conversion obtained. This
transformation seems to be controlled by different factors. As expected, the
reaction is determined by substitution on alcohol. The transesterification
proceeds faster for primary alcohol (entries 1–6), and no reaction was
observed with secondary (entries 7, 8) and tertiary alcohol (entry 9). In the
cases of primary alcohol, it seems to us that the temperature exercises great
control on the reaction. Thus, with the alcohols 2a–d, the reaction temperature
was 1108C (refluxing of toluene) and the conversion observed was very high.
For the propan-1-ol 2e and ethanol 2f, the conversion obtained was 74 and

Transesterification of Methylbenzoate
1589
57% when the temperature of the reaction was 97 and 788C, respectively.
These results suggest that the reaction temperature plays an important role
in the transesterification process.
Furthermore, we have examined the transesterification of methylbenzoate
with various alcohols without solvent. In this case, the reaction temperature
was determined by the boiling point of the alcohol. The results obtained
(Table 2) show that the same conversion of methylbenzoate was obtained
for all alcohols except for cyclohexanol. In this case, the conversion was
94% without solvent, whereas no reaction was observed in toluene. This
result can be explained also by the combined roles of the nature of alcohol
and reaction temperature. We can reasonably hypothesize that cyclohexanol,
as a secondary alcohol, gave no reaction at 1108C (refluxing of toluene)
whereas the transesterification become possible at 1608C (refluxing of
cyclohexanol). It should be noted that no transesterification was obtained
with isopropanol and tertiobutanol either with or without solvent. The
relatively low reaction temperature limited here by the boiling point of
these alcohols can explain this result.
In summary, we have studied the transesterification of methylbenzoate
with various alcohols catalyzed by the available natural phosphate. This
recycled catalyst can be used with or without solvent. High conversions
were observed with primary alcohol whereas the conversion can occur with
cyclohexanol when used without solvent. It seems that not only the nature
of the alcohol but also the reaction temperature exercise a great control on
the reaction. We have shown in this study that the natural material NP can
also catalyze efficiently the transesterification reaction.
Table 2. Transesterification of methylbenzoate with
various alcohols catalyzed by NP
Conversion (%)a
With
toluene
Without
solvent
Entry
1
Alcohol
n-C4H9OH
2a
2b
2c
2d
2e
2f
100
97
98
100
74
57
0
99
95
96
100
79
65
94
0
n-C6H13OH
n-C8H17OH
PhCH2OH
3
4
5
6
7
8
9
n-C3H7OH
C2H5OH
Cyclohexanol
(CH3)2CHOH
(CH3)3COH
2g
2h
2i
0
0
0
aConversion of methylbenzoate (GC) after 48 h of
reaction time.

1590
F. Bazi et al.
EXPERIMENTAL
Preparation of the Catalysts
NP comes from an extracted ore in the region of Khouribga (Morocco). The
fraction of 100–400-mm grain size has been isolated, washed with water,
calcined at 9008C for 2 h, washed again, calcined at 9008C for 0.5 h, and
ground (63–125 mm) to give the NP catalyst. The structure of calcined
phosphate NP is similar to that of fluorapatite Ca10(PO4)6F2, as shown by
the X-ray diffraction pattern and IR spectroscopy. The chemical composition
was determined as Ca (54.12%), P (34.24%), F (3.37%), Si (2.42%), S
(2.21%), C (1.13%), Na (0.92%), Mg (0.68%), Al (0.46%), Fe (0.36%), K
(0.04%), and other metals in the range under 6 ppm. The specific surface
area of NP was determined by the BET method from the adsorption–
desorption isotherm of nitrogen at its liquid temperature (77 K). The total
pore volume was calculated by the BJH method at P/P0 ¼ 0.98. The NP
shows a very low surface area (1–2 m2 g21) together with a low total pore
volume (VT ¼ 0.007 cm3/g).
Typical Procedure for Transesterification
Methylbenzoate (2 mmol), alcohol (11 mmol), and catalyst PN (0.1 g) were
refluxed without or with solvent (3 ml) for the specific time. The progress of
the reaction was monitored by GC. After the reaction, the catalyst NP was
isolated by filtration, and the total conversion was calculated by GC. The
excess alcohols and the solvent were removed under reduced pressure. The
required ester is purified by column chromatography (hexane/
ethylacetate ¼ 98/2) and analyzed by H1 NMR.
ACKNOWLEDGMENTS
Research Center for Studies on Mineral Phosphates (CERPHOS), Office
´
Cherifien des Phosphates (OCP) group is gratefully acknowledged.
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