Zeolite Catalyzed n-Butyl Levulinate Synthesis
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O
containment, disposal and regeneration due to their corrosive
andtoxicnature. Theuseofheterogeneouscatalystsinorganic
synthesis has grabbed significant levels since they provide
green alternatives to homogeneous catalysts [17, 18]. Number
of other heterogeneous catalyst have been also reported for
this reaction such as heteropoly acids (HPAs) and supported
HPA [19]. It is worthy to note that, heteropolyacids (HPAs)
have been widely used in numerous acid-catalyzed esterifi-
cationreactionsduetotheirstrongBronstedacidity.However,
some of the major problems associated with HPAs in the bulk
form are their low surface areas (1–10 m2/g) and separation
problem from reactionmixture [20, 21]. Recently, Dharne and
Bokade [19] have reported the esterification of LA with
n-butanol to produce corresponding ester, n-butyl levulinate
using solid acid catalyst, dodecatungstophosphoric acid
(DTPA) supported on acid treated clay. They have observed
97 % LA conversion for two cycles. However, thereafter,
noticed drastic decrease in LA conversion due to increasing
leaching of DTPA from the support [19].
+
HO
OH
n-butanol
O
levulinic acid
Zeolite
O
O
O
+
H2O
n-butyl levulinate
Scheme 1 Zeolite catalyzed esterification of levulinic acid
HZSM-5 (SiO2/Al2O3 = 30) zeolites were obtained from
Sud-Chemie India Pvt Ltd., Vadodara, Gujarat, INDIA. The
phase purity and crystallinity of the zeolites were analyzed
by XRD (D8 Advanced Brucker AXS, Germany) with Cu Ka
radiation using nickel filter and Bruker Smart 6000 CCD
detector. Surface area measurement (BET method) was
carried out on Micromeritics Gemini at -196 °C using
nitrogen adsorption isotherms. Acidity of zeolites were
determined on Micromeritics Chemisorb 2720, by a tem-
perature programmed desorption (TPD) of ammonia.
Ammonia was adsorbed at 120 °C and then desorption was
carried out up to 700 °C at heating rate of 10 °C/min. Lev-
ulinic acid (98 %) and n-butanol (99 %) were obtained from
Alfa Aesar, Ward Hill, MA, USA. All the reagents used were
of analytical grade and used without further purification.The
solvents were distilled before use.
Zeolites are crystalline, highly ordered, microporous
aluminosilicates with intracrystalline channels and cages of
molecular dimensions [22]. Zeolites find wide applications
in production of petrochemicals, often replacing environ-
mentally unfriendly catalysts. The hydrogen form of zeolites
(prepared by ion-exchange) are powerful solid-state acids,
and used to catalyzed host of organic reactions, such as
isomerization, alkylation, and cracking. Excellent reviews
have been devoted to a large number of zeolite-catalyzed
organic reactions [23, 24]. For carrying out various kinds of
organic transformations, zeolite catalysts of different acid
strengths and textural properties are required.
Moreover, zeolite beta is widely being studied in liquid
phase organic transformations and some of the processes are
being commercialized [25]. The large pore beta (BEA) zeolite
is structurally disordered and its framework structure was
described as a three-dimensional intersecting channel system.
It is well known that, amongst the various zeolite, the unique
acid properties, mainly related to local defects, the optimal
pore dimensions and higher surface area make zeolite beta a
very promising catalyst in acid catalyzed shape selective
organic conversions [26, 27]. To the best of author’s knowl-
edge there are no reports available for the esterification of LA
using various acidic zeolites. The present work includes the
synthesis of n-butyl levulinate by esterification reaction of LA
with n-butanol using various acidic zeolites (Scheme 1).
2.2 Typical Procedure for the Esterification of LA
with n-Butanol
All zeolites were activated, by heating at higher temperature
of 550–550 °C for 3–4 h, before loading into the reactor.
Esterification reaction has been carried out in order to opti-
mize various reaction conditions such as reaction time, cat-
alyst concentration, molar ratio etc. All the reactions were
carried out in a round bottom flask attached to a condenser
and equipped with a magnetic stirrer under heating in an oil
bath. Typically, a 50 ml round-bottom flask was charged
with LA and n-butanol, both weighed sequentially, followed
by the addition of the desired amount of preactivated cata-
lyst. The reagent amounts were calculated according to the
desired molar ratio for each reaction. Then, the system was
heated up to 120 °C, the reaction was carried out, for 4–12 h
while stirring at 400 rpm and finally the products were col-
lected after removing the catalyst. After completion of the
2 Experimental
2.1 Catalyst Preparation and Characterization
The zeolites H-Beta [BEA; SiO2/Al2O3 = 25], H-Mordenite
[H-MOR; SiO2/Al2O3 = 20], H-Y (SiO2/Al2O3 = 5.1),
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