Minchitha et al.
Design of Sulphate Modified Solid Acid Catalysts for Transesterification of Diethyl Malonate with BA
ester is transformed into another ester through the inter
change of an alkoxy moiety between an ester and alcohol.
to evaluate the correlation between the physico-chemical
properties of the catalysts and their catalytic activities.
In the present study a transesterification reaction between
diethyl malonate (DEM) and benzyl alcohol (BA) was cho-
sen. The selected reaction generates benzyl malonates, as
the transester products which are industrially important
active pharmaceutical ingredients.
The catalytic materials are systematically characterized
for their physico-chemical properties to evaluate their rela-
tionship with catalytic acidity. Further, total yield of the
transester (mono and dibenzyl malonates) and their selec-
tivity were optimized by conducting the reactions under
different experimental conditions. Kinetics of the reactions
was studied and hence activation energy of the reaction
with different catalysts was evaluated.
ꢀ
ꢀ
R−COOR +H−OR → R−COOR +H−OR
Transesterification is an equilibrium process; hence occur
essentially by a simple mixing of the reactants. However,
the reaction is accelerated in presence of an acid or a base
1
6
catalyst. A number of homogeneous and heterogeneous
catalysts1
7ꢀ18
have been investigated for their catalytic
activity in a variety of transesterification reactions by dif-
ferent research groups all over the globe. Heterogeneously
catalyzed reactions have a few advantages over homoge-
neous reactions such as less toxicity, simple product iso-
1
9–21
lation procedures and recyclability of the catalyst.
For
2
2
instance, Nagaraju and his team have reported synthe-
sis of salol using methyl salicylate with phenol in pres-
ence of solid acid catalysts via transesterification reactions.
Isoamyl salicylate was synthesized using methyl salicy-
late and isoamyl alcohol in presence of modified ZrO2,
SiO , Al O catalysts via vapour phase transesterification
2
. EXPERIMENTAL DETAILS
2
.1. Materials and Methods
2.1.1. Materials
Multiwalled carbon nanotubes (CNTs) and Mesoporous
carbon (MC) were procured from Nanocyl, Belgium
(99.5%) and Sigma Aldrich (99.95%), respectively. Zir-
conium hydroxide (96%), Silicon dioxide (98.5%), ben-
zyl alcohol (99%), diethyl malonate (95.5%) and sulphuric
acid (98%) were obtained from Merck India Pvt. Ltd.
Aluminium hydroxide (98%) was purchased from Across
chemicals.
2
2
3
2
3
reaction. In the same line of their research, transesteri-
fication of diethyl malonate and benzyl alcohol was car-
ried out using modified aluminophosphate for the synthesis
2
4
of benzyl ethyl malonate and dibenzyl malonate. Thim-
maraju et al., have prepared modified zirconia catalysts
for the synthesis of benzyl ethyl malonate and dibenzyl
malonate using diethyl malonate and benzyl alcohol was
IP: 5.101.222.185 On: Fri, 02 Nov 2018 18:46:55
reported. The same group also reporte dC toh pa yt rpi gh he nt :y Al sma lei cr iyc -a n Scientific Publishers
late could be synthesized via transesterification o Df em l iev t eh ry el d by2 I. n2 .g eP nr teap aration of Catalytic Materials
salicylate and phenol using honeycomb monolith coated
Sulphate ion modified CNTs, MC, Zirconia, Alumina and
Silica were prepared as described below.
2
5ꢀ26
with Mo(VI) ZrO catalysts.
2
It is evident from the reported literature that materials
with acidic and/or basic properties having porous texture
and high surface area are the preferred catalysts in trans-
estrification reactions. An analysis of the reported results
also indicates that the percentage yields and the selectivity
of the transester product depend on a number of pre and
post synthesis modifications made on the catalyst. This
being the case, similar catalysts studied by different groups
showed inconsistency in the results which are essentially
sporadic in nature. Keeping this point in view here we
have made an attempt to design and compare the catalytic
activity of a few materials with different textural and struc-
tural properties in transesterification reaction under similar
experimental conditions. The materials selected are those
which are commonly used as heterogeneous catalysts in
industrially important acid catalyzed reactions. Further a
few of the catalysts selected have not been so far investi-
gated for their catalytic activity in transesterification reac-
tion, and hence are novel.
In a typical procedure 2 g of the support (CNTs, MC,
zirconium hydroxide, aluminium hydroxide and silicon
dioxide) were weighed separately and treated with 5 mL
of 3 M H SO and mixed well in an agate mortar for
2
4
1 h to get a homogeneous paste. The paste was dried in
ꢁ
a hot air oven at 110 C for 12 h and finally powdered.
Further, sulphuric acid treated zirconium hydroxide, alu-
minium hydroxide and silicon dioxide samples were cal-
ꢁ
cined at 550 C for 5 h in a muffle furnace. The H SO
2
4
treated supports are henceforth represented as S-CNTs,
S-MC, S-ZrO , S-Al O and S-SiO . The percentage yield
2
2
3
2
of the sulphuric acid modified catalysts S-CNTs, S-MC,
S-ZrO , S-Al O and S-SiO was found to be 91%, 84.5%
2
2
3
2
and the rest being 100%.
2.3. Characterization of the Prepared Material
All the prepared materials were characterized to evaluate
their structural and textural properties using the follow-
ing techniques. Powder X-ray diffraction patterns (PXRD)
were recorded on a Panalytical Xpert pro X-ray diffrac-
tometer using Cu Kꢁ radiation (ꢂ = 0ꢃ154 nm) in the
The main objective of the present work is to com-
pare the catalytic activity of distinctly different catalysts
under similar experimental condition to evolve the nature
of the active sites responsible for an industrially important
organic transformation. This kind of study is also essential
ꢁ
ꢁ
2ꢄ range of 5 to 70 at 40 kV and a scanning rate of
ꢁ
2 /min. Brunauer, Emmett and Teller (BET) surface area
was determined from Quantachrome Nova-1000 surface
J. Nanosci. Nanotechnol. 18, 202–214, 2018
203