Selective mono-isopropylation of 1,3-propanediol with isopropylalcohol using heteropoly acid supported on K-10 clay catalyst

Article abstract of DOI:10.1016/j.cattod.2014.02.009

Catalytic hydrogenolysis/hydrogenation of bioglycerol leads to 1,2 and 1,3-propanediols, which can befurther valorized to industrially important products through a variety of reactions such as etherification, esterification and cyclization through acetalization. In the current work, selective mono-etherification of 1,3-propanediol (PDO) with isopropanol to 3-isopropyl-1-propanaol was systematically studied, using 20% w/w Cs_2.5H_0.5PW₁₂O₄₀/K-10 catalyst in an autoclave at 170°C. In a typical reaction, using 1:6 molratio of 1,3-PDO to isopropanol at 0.03 g/cm³ catalyst loading and 1000 rpm, 60% conversion wasachieved with 100% selectivity to the product. The catalyst was prepared by incipient wetness tech-nique and characterized by various techniques such as X-ray diffraction, surface area measurement byN₂ adsorption-desorption, FTIR, and SEM. Effect of various reaction parameters on conversion and selectivity was studied to establish kinetics and mechanism. The catalyst is robust and reusable. The overallprocess is green and clean.

Full text of DOI:10.1016/j.cattod.2014.02.009

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Selective mono-isopropylation of 1,3-propanediol with isopropyl
alcohol using heteropoly acid supported on K-10 clay catalyst
Ganapati D. Yadav∗, Devendra P. Tekale
Department of Chemical Engineering, Institute of Chemical Technology, Nathalal Parekh Marg, Matunga, Mumbai 40019, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Catalytic hydrogenolysis/hydrogenation of bioglycerol leads to 1,2 and 1,3-propanediols, which can be
further valorized to industrially important products through a variety of reactions such as etherification,
esterification and cyclization through acetalization. In the current work, selective mono-etherification of
1,3-propanediol (PDO) with isopropanol to 3-isopropyl-1-propanaol was systematically studied, using
20% w/w Cs2.5H0.5PW12O40/K-10 catalyst in an autoclave at 170 ◦C. In a typical reaction, using 1:6 mol
ratio of 1,3-PDO to isopropanol at 0.03 g/cm3 catalyst loading and 1000 rpm, 60% conversion was
achieved with 100% selectivity to the product. The catalyst was prepared by incipient wetness tech-
nique and characterized by various techniques such as X-ray diffraction, surface area measurement by
Received 3 November 2013
Received in revised form 7 January 2014
Accepted 10 February 2014
Available online xxx
Keywords:
Etherification
1,3-Propanediol
3-Isopropoxypropan-1-ol
Green chemistry
Heteropolyacids
N
2 adsorption–desorption, FTIR, and SEM. Effect of various reaction parameters on conversion and selec-
tivity was studied to establish kinetics and mechanism. The catalyst is robust and reusable. The overall
process is green and clean.
© 2014 Elsevier B.V. All rights reserved.
1. Introduction
also as fuel additives [6,7]. Properties of catalytic materials such as
acidity, hydrophilic and lipophilic balance, and surface area play
In the production of biodiesel, glycerol is co-produced to
the tune of 10% by weight. Unless glycerol is further con-
verted into valuable products, biodiesel production will not
be economically viable vis-à-vis petro-diesel [1,2]. Among
many of glycerol derivatives, 1,2- and 1,3-propanediols (PDO)
[3], acrolein [4] and acrylic acid are important bulk chem-
icals. 1,3-PDO is produced by the hydration of acrolein to
3-hydroxypropionaldehyde which on hydrogenation yields 1,3-
PDO. 1,3-Propanediol is used in several industrial product
s such as adhesives, laminates, coatings, composites, moldings,
aliphatic polyesters, copolyesters, solvents, antifreeze agent and
wood paint. It is growing with a compound annual growth rate
of 19.9% and is expected to reach $560 million by 2019 [5]. 1,3-PDO
can further be converted to various compounds by esterification,
etherification and acetalization using heterogeneous solid as well
as base catalysis. Many of the etherified derivatives of 1,3-PDO are
useful in various industries. For instance, mono isopropyl ether of
1-propanol finds application as solvent for printing and cleaning
lithographic printing plates, preparation of alcoholic solvent com-
positions in stripping off the photo-resist in electronic devices and
a vital role in controlling the selectivity of the etherification reac-
tion [8]. Primary alcohols react exothermically and easily at room
temperature in the presence of homogeneous catalysts such as
sulphuric acid whereas exothermicity decreases when secondary
alcohols are used. In the case of tertiary alcohol there is further
decrease in exotherm [9]. It is suggested that the nature of catalyst
support plays vital role in shifting the reaction equilibrium in for-
ward direction; for instance, in the case of montmorrilonite clay,
it adsorbs the water formed during the reaction and hence pro-
motes the forward reaction [10]. Not much work is reported on the
isopropylation of 1,3-PDO using solid acid catalysis.
Keggin type heteropolyacids (HPAs) have been used in many
organic reactions as homogeneous catalysts and their structures
are well known [11,12]. However, HPAs in unsupported form
are plagued with low activity, poor stability and rapid deactiva-
tion. Various supports like montmorillonite clay, alumina, zirconia,
mesoporous silica, mesoporous aluminosilicates and carbon have
been used to improve the stability and efficacy of HPAs. [12].
Dodecatungstophosphoric acid (H3PW12O40) supported on K-10
clay was found be a better catalyst in etherification reactions
[13,14]. Kimura et al. [15] have reported that acidic cesium salts
of HPAs are highly water tolerable catalyst, whereas our labora-
tory demonstrated a novel procedure to generate nano-catalyst
Cs2.5H0.5PW12O40 (Cs-DTP) in situ within K-10 clay support which
can be reused repeatedly without loss of activity [16,17]. 20% w/w
∗
Corresponding author. Tel.: +91 22 3361 1001; fax: +91 22 3361 1002/1020.
E-mail addresses: gd.yadav@ictmumbai.edu.in, gdyadav@yahoo.com
(G.D. Yadav).
http://dx.doi.org/10.1016/j.cattod.2014.02.009
0920-5861/© 2014 Elsevier B.V. All rights reserved.
Please cite this article in press as: G.D. Yadav, D.P. Tekale, Selective mono-isopropylation of 1,3-propanediol with isopropyl alcohol
using heteropoly acid supported on K-10 clay catalyst, Catal. Today (2014), http://dx.doi.org/10.1016/j.cattod.2014.02.009

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2.2. Catalyst synthesis
2
Nomenclature
K-10 Clay (Fluka) was of H+ type. Approximately 10 g of K-10
A
Reactant species A; 1,3-propanediol
clay was oven dried to 120 ◦C for 1 h. 0.2808 g (1.671 × 10−3 mol) of
CsCl was weighed accurately and dissolved in 10 cm3 of methanol.
This volume of solvent used was approximately equal to the pore
volume of the catalyst. The solution was added to the previously
dried and accurately weighed 8 g of K-10 clay to form slurry. The
slurry was stirred vigorously and air-dried. The resultant material
was then dried in oven at 120 ◦C for 2 h. This was then fur-
ther subjected to impregnation by an alcoholic solution of 2 g
(6.688 × 10−4 mol) of DTP in 10 cm3 of methanol. The solution was
added to the previously treated K-10 clay with CsCl again to form
slurry. The slurry was stirred vigorously and air-dried. The pre-
formed catalyst was dried in oven at 120 ◦C for 2 h and then calcined
at 300 ◦C for 3 h.
AS
B
BS
E
ES
W
CA, CB
Chemisorbed A
Reactant species B; isopropyl alcohol
Chemisorbed B
3-Isoproxy-propan-1-ol
Chemisorbed product
Water
Concentration of A and B (mol/cm3)
CA0, CB0 Initial concentration of A and B (mol/cm3)
CAS, CBS Concentration of A and B on solid catalyst surface
(mol/g-cat)
CES, CWS Concentration of E and W at solid catalyst surface
(mol/g-cat)
CS
Ct
Concentration of vacant sites (mol/g-cat)
Total concentration of sites (mol/g-cat)
Rate of disappearance of A (mol cm−3 min−1
2.3. Experimental setup
−rA
)
KA
Equilibrium constant for adsorption of A on catalyst
The reactions were conducted in a 100 cm3 capacity Parr reactor
equipped with a four-bladed pitched-turbine impeller. The tem-
perature was maintained at 1 ◦C of the desired value with the
help of an in-built proportional integral differential (PID) con-
troller. Predetermined quantities of desired reactants were added
and a known amount of catalyst was charged in to the reactor
and temperature was raised to desired value. An initial sample
was withdrawn and agitation was started. Additional samples were
withdrawn at periodic time intervals up to 3 h to monitor the reac-
tion.
Before charging the reactants, the reactor was purged with
nitrogen to vent the air and to ensure inert atmosphere. The reac-
tions were conducted at desired temperature; speed of agitation
and without any solvent. In a typical reaction, 0.065 mol of 1,3-PDO
was reacted with 0.390 mol of 2-propanol (1:6 mol ratio of 1,3-
PDO to 2-propanol) with 1.09 g of catalyst; this makes 0.03 g/cm3
loading of the catalyst with respect to total reaction volume) at
1000 rpm at 170 ◦C.
surface (cm3/mol)
KB
k2
KE
Equilibrium constant for adsorption of B on catalyst
surface (cm3/mol)
Surface reaction rate constant ((cm6 mol−1 g-
cat−1 min−1
)
Equilibrium constant for adsorption of E on catalyst
surface (cm3/mol)
kR
Reaction rate constant (cm6 mol−1 g-cat−1 min−1
)
on
KW
Equilibrium constant for adsorption of
catalyst surface (cm3/mol)
Initial mole ratio of B to A.
Vacant site
W
M
S
t
w
XA
Time, min
Catalyst loading (g/cm3 of liquid phase)
Fractional conversion of A
Clear liquid samples were withdrawn at regular time intervals
by reducing the speed of agitation to zero and allowing catalyst to
settle at the bottom of the reactor. Analysis of the reaction samples
was performed by gas chromatography (GC) on a Chemito-1000
model. BPX-5, 30 m × 0.25 mm internal diameter glass column was
used for the analysis in conjunction with a flame ionization detec-
tor. Quantification of data was done through internal standard
method. The product was confirmed by GC–MS (Perkin Elmer
Instrument, Clarus 500) with BP-1 capillary column (0.25 mm i.d.,
30 m length) and EI mode of MS. All experiments were done in trip-
licate and the average values are reported. The standard deviation
was 2.5%.
Cs-DTP/K10 was found to be the best in a number of reactions.
Lower loadings have been studied earlier by us and it was found
that 20% w/w DTP/K-10 is the best which on substitution with Cs
renders higher surface area and increases total acidity per unit mass
of support [13,14]. The function of support is to enhance the uni-
form distribution of catalyst on pore walls of K-10 and also to add
to the overall acid strength of the catalyst. However, with increase
in loading of Cs-DTP beyond 20% w/w on K-10, the surface area was
decreased due to clogging of some fine pores of support by Cs-DTP
particles. Since 20% w/w Cs-DTP/K10 was better than unsupported
dodecatungstophosphoric acid (DTP) and Cs-DTP as well as K-10
clay supported DTP, it was used as standalone catalyst in this study.
The current work describes selective mono isopropylation of
1,3-PDO using 20% w/w Cs-DTP/K-10 catalyst under solvent-free
reaction condition. The catalyst was characterized by various tech-
niques such as X-ray diffraction, surface area measurement by N2
adsorption–desorption, FTIR, and SEM.
2.4. Catalyst characterization
2.4.1. FT-IR study
FT-IR study of the catalyst was carried out with a Perkin-Elmer
instrument. Samples were mixed in KBr and pressed to prepare thin
pellets. Pellets were subjected to number of scans before recording
2. Experimental
the spectra at a resolution of 2 cm−1 between 4000 and 350 cm−1
.
2.1. Chemicals
2.4.2. BET-surface area analysis
All the chemicals were procured from reputed firms and used
without any further purification. 1,3-propanediol (99%), cesium
chloride (99.9%), 2-propanol and dodecatungstophosporic acid
hexahydrate were procured from M/s. s. d. Fine Chemicals, Mum-
bai, India. Synthesis grade methanol was procured from Merck Ltd.
Montmorillonite-K-10 was obtained from Fluka, Germany.
Surface area measurement was carried by nitrogen adsorption
on Micromeritics ASAP 2010 instrument. BET measurements were
carried out at 77 K, after pre-treating the sample under high vacuum
at 300 ◦C for 4 h. Surface area and pore volume of the fresh as well
as spent catalysts were derived from N2 adsorption–desorption
isotherms using the conventional BET and BJH methods.
Please cite this article in press as: G.D. Yadav, D.P. Tekale, Selective mono-isopropylation of 1,3-propanediol with isopropyl alcohol
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Table 1
3
2.4.3. X-ray diffraction study
Crystallinity and textural patterns of the catalysts were studied
by XRD analysis using a Bruker AXS powder diffractometer D8 with
BET surface area, pore volume and pore diameter analysis.
Catalyst
BET surface area
(m2/g)
Single point total
pore volume
(cm3/g)
BET average
pore diameter
(4 A/V by) (nm)
˚
Cu-K␣ (1.54 A) radiation.
K-10
273.01 0.84
239.61 0.45
223.49 0.52
0.392
0.330
0.308
5.749
5.518
5.558
2.4.4. Scanning electron microscopy
Fresh Cs-DTP/K-10
Regenerated
Cs-DTP/K-10
Surface morphology of the catalyst was captured by SEM (SU 30
microscope, JEOL, Japan). The sample was dried and mounted on
specimen studs and sputter coated with a thin film of platinum to
make the surface conducting.
loop of type H3, which is characteristic of mesoporous solid. Partial
substitution of H by of Cs into H3PW12O40 leads to the forma-
tion of nanoparticles of Cs2.5H0.5PW12O40 which are insoluble and
trapped within the pore space of K-10 clay. Thus, the surface area
of supported Cs-DTP on K-10 clay increases to 207 m2/g from orig-
inal DTP/K-10 [16] (Table 1). This leads to stability of the catalyst.
Okuhara et al. [20] have disclosed that alkali exchange with pro-
ton of HPA results in enhanced activity, better stability and higher
surface area of heteropoly acids. The partial incorporation of Cs+
ion in place of H+ in dodecatungstphosphoric acid supported on
montmorillonite K-10 results in enhancement of catalytic activity
and also change in surface structural properties such as pore vol-
ume, pore diameter and surface area (Table 1). Salts of small cations
( like group A) are highly soluble in water while salts of large cations
(like Cs of group B) are completely insoluble in aqueous medium
and any organic solvents, making them useful for heterogeneous
reactions.
3. Results and discussion
3.1. Catalyst characterization
3.1.1. FT-IR study
Primary structures of supported DTP and cesium salt of
DTP were identified by comparing their FT-IR absorbance
bands to those of bulk unsupported K-10, DTP on K-10 and
Cs2.5H0.5PW12O40 which show characteristic IR bands at approxi-
mately 1080 cm−1 (P O in central tetrahedral), 984 cm−1 (terminal
W
O), 897 cm−1 and 812 cm−1 (W
O W) associated with the
asymmetric vibrations in the Keggin polyanion [16,17] (Fig. 1).
However, Cs2.5H0.5PW12O40 is characterized by the split in the
W
O band, suggesting the direct interaction between the poly
anion and Cs+. FT-IR spectra of 20% w/w DTP on K-10 and 20% w/w
Cs2.5H0.5PW12O40/K-10 indicate that the primary Keggin structure
is preserved in both the cases on K-10 support. When the charac-
teristic peaks of unsupported HPA and K-10 are superimposed, the
peaks for the supported catalysts appear without any shift in the
peak position. Sharp peak at 1631 cm−1 indicates the presence of
H3O+ ion (bronsted acidity). In DTP, water is present as water of
crystallization while in case of Cs2.5H0.5PW12O40/K-10, it indicates
the presence of partial H+ ion directly attached to the polyanion
(· · ·O H) and is present in K-10 and possibly as H3O+ [18,19].
BET surface area study of Cs2.5H0.5PW12O40/K-10 catalyst was
also carried out to verify any morphological change in the catalyst
after the reaction. The results showed a very marginal change in the
surface area, pore volume and pore diameter of the catalyst after
the reaction. These results support the fidelity of pore structure of
the catalyst on repeated use.
3.1.3. X-ray diffraction study
X-ray diffraction study of catalyst was carried out before and
after the reaction (Fig. 2). After the experiment was over, the cat-
alyst was recovered by filtration, washed thoroughly and refluxed
in methanol to remove the product and unreacted reactants. The
catalyst was then calcined at 300 ◦C. It was observed that there was
no crystallographic change in the catalyst during the reaction. Bulk
DTP is crystalline in nature. Also, the Keggin structure was pre-
served during proton exchange of bulk DTP with Cs+ ion. The XRD
of K-10 shows a sharp peak at 2ꢀ = 26.2, belonging to quartz and
there is no effect on the 2ꢀ value even after loading the K-10 clay
3.1.2. BET-surface area analysis
Table 1 shows results of BET surface area analysis of the catalysts.
Surface area of K-10 was 273.01 m2/g, which is higher than that of
Cs2.5H0.5PW12O40/K-10 (239.61 m2/g). The pore size distribution
plot of catalysts suggests that the average pore size for catalysts is in
the range of 5.0–6.5 nm suggesting that pore size of the catalysts lies
in the mesoporous region, i.e. >2 nm. The adsorption–desorption
isotherms for K-10, DTP/K-10 and Cs2.5H0.5PW12O40/K-10 show
that they have the form of Type IV isotherm with the hysteresis
Fig. 2. XRD patterns of used Cs-DTP/K-10, K-10, Bulk DTP, and Cs-DTP/K-10 cata-
lysts.
Fig. 1. FT-IR patterns of (a) unsupported K-10, (b) 20% w/w DTP/K-10 and (c) 20%
w/w Cs-DTP/K-10.
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Fig. 3. SEM images of (a) fresh Cs-DTP/K-10 catalyst and (b) used Cs-DTP/K-10.
CH3
HO
O
CH3
Acid Catalyst
HO
+
HO
OH
1, 3-propanediol
-
H2O
CH3
3-isopropoxypropan-1-ol
CH3
2-propanol
Scheme 1. Isopropylation of 1,3-propanediol.
either with DTP or with Cs exchange. From the background XRD
reflection for K-10, it is inferred that K-10 is amorphous in nature.
It was observed that while impregnating DTP on K-10 some crys-
tallinity of DTP was lost. In order to study the effect of repeated
use on textural pattern of Cs2.5H0.5PW12O40/K-10, XRD of the cat-
alyst was recorded after the use. On comparing the XRD pattern of
used catalyst with that of fresh, no change in textural pattern and
crystallinity was observed. This also confirmed the stability of the
catalyst.
peak for monoisopropylated 1,3-propanediol. The peak at m/z 59 is
the base peak for isopropoxy cation after the ether cleavage. This
confirmed that there was no di-etherified product (Fig. 4).
3.2.1. Proof of absence if external mass transfer resistance
It was necessary to study the effect of external mass trans-
fer resistance. Therefore effect of speed of agitation was studied
to ascertain the absence of external resistance to mass transfer.
Reactions were carried out in the range of 800–1200 rpm with
0.03 g/cm3 catalyst loading at 170 ◦C. Fig. 5 shows that the 1,3-PDO
conversion remained practically the same after 800 rpm, which
suggested the absence of external resistance to mass transfer. To
be on safer side, further experiments were carried out at 1000 rpm.
3.1.4. Scanning electron microscopy
Fig. 3 shows the SEM images of the Cs-DTP/K-10 catalyst before
(Fig. 3a) and after the reaction (Fig. 3b). No change in catalyst sur-
face morphology was observed after the reaction. In conclusion,
SEM study reveals that morphological properties of the catalyst
remain unaffected after the reaction.
3.2.2. Effect of catalyst loading
In the absence of external mass transfer resistance, the rate of
reaction is directly proportional to catalyst loading based on the
entire liquid phase volume. The catalyst loading was varied over
a range of 0.02–0.04 gm/cm3 of the total reaction volume. Fig. 6
shows that the conversion increases with increase in the number
active sites and remains the same at 0.03 g/cm3 onwards, beyond
which the number of active sites was more than required. Hence
further experiments were carried out at 0.03 g/cm3 of catalyst load-
ing.
3.2. Etherification reaction
Scheme 1 shows the overall reaction in the presence of an acid
catalyst.
The control experiments showed that only a single product, 3-
isoproxypropan-1-ol was formed under experimental conditions.
The reasons are as follows. The cracking of isopropanol to propylene
and water and formation of diisopropyl ether (DIPE) in situ, both of
which are alkylating agents, have been studied by us independently
[21,22]. The dehydration of IPA was studied over a broad range of
temperature (110–150 and 180–220 ◦C) which showed that DIPE
although formed at lower temperature, cracks faster than IPA.
Beyond 150 ◦C, diisopropyl ether cracks to form both these products
which are consumed to form the mono-ether. Mono-isopropylation
of 1,3-propanediol requires higher temperature (170 ◦C). So the
formation of di-ether product, 1,3-diisopropoxy propanediol even
requires much higher temperature. GC–MS results shows the m/z
peak at 118 (M++1) in +ve ESI mode assigned to molecular ion
3.2.3. Effect of 1-3PDO to isopropyl alcohol mole ratio
The effect of mole ratio (Fig. 7) of 1,3-PDO to isopropyl alco-
hol ratio in the range of 01:02–01:08 was studied under otherwise
similar conditions. Conversion of 1,3-PDO increased, as isopropyl
alcohol concentration was increased with respect to 1,3-PDO.
3.2.4. Effect of temperature
The effect of temperature on 1,3-PDO conversion was studied
from 160 to 180 ◦C. It was observed that the initial rate of reaction
increased with increase in temperature (Fig. 8). Above 170 ◦C some
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Fig. 4. GC–MS spectra of reaction mass.
marginal increase in the final conversion of 1,3-PDO was observed,
although the initial rate had increased and therefore 170 ◦C was
taken as optimum.
publications [23]. It is necessary to understand the reaction mech-
anism to develop a suitable model. Scheme 2 depicts the reaction
mechanism involving adsorption of reactant species on the cata-
lyst surface. The lone pair of electron on oxygen of one hydroxyl
group of 1,3-PDO attacks on the secondary carbon of 1,3-PDO to
form mono isopropyl ether of 1,3-PDO. The reaction mechanism is
considered to be followed by weak adsorption on the catalyst sur-
face, surface reaction and desorption from the surface as shown in
Scheme 2.
3.3. Reaction mechanism and kinetic model
The effect of various parameters showed that the reaction
was free from both external mass transfer and intra-particle
diffusion limitations. Theoretical calculations were done with ref-
erence to effect of each parameter as discussed in some of our
Fig. 5. Effect of speed of agitation. Catalyst loading: 0.03 g/cm3, temperature: 170 ◦C,
glycerol:BA mole ratio:: 1:6 reaction duration 3 h. (ꢀ) 1000 rpm; (ꢁ) 800 rpm; (ꢂ)
1200 rpm.
Fig. 6. Effect of catalyst loading. 1,3-PDO to i-PA mole ratio: 1:6, speed of agi-
tation: 1000 rpm, temperature: 170 ◦C, reaction duration: 3 h. (ꢀ) 0.02 g/cm3; (ꢁ)
0.03 g/cm3; (ꢂ) 0.04 g/cm3.
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Scheme 2. Isopropylation of 1,3-PDO.
Adsorption of 1,3-PDO (A) on the vacant site S is given by
The total concentration of the sites, Ct is expressed as
Ct = CS + CAS + CBS + CES + CWS
or
K
A
(6)
(7)
A + SꢃAS
(1)
Similarly, adsorption of isopropyl alcohol (B) on the vacant site is
represented as
Ct = KACACS + KBCBCS + KECECS + KW CW CS
K
B
or, the concentration of vacant sites,
B + SꢃBS
(2)
Ct
Surface reaction of AS with BS on the adjacent sites leads to for-
mation of 3-isopropoxy-1-propanol (ES) and water (WS) on the
catalytic sites
CS
=
(8)
1 + KACA + KBCB + KECE + KW CW
If surface reaction controls the rate of reaction, then the rate of
reaction of A is given by
K
2
AS + BSꢃES + WS
(3)
dCA
−rA = −
= k2CASCBS − k2ꢀ CESCWS
(9)
Desorption of 3-isopropoxy-1-propanol and water is shown as
dt
ES1ꢃ/KEE + S
(4)
(5)
k2{KAKBCACB − (KEKW CECW )/K2}Ct2
−dCA
=
(10)
2
1/K
W
dt
(1 + KAKC + KBCB + KECE + KW CW
)
WS ꢃ W + S
Fig. 7. Effect of mole ratio of 1,3-PDO to i-PA. Speed of agitation: 1000 rpm, tem-
perature: 170 ◦C, catalyst loading: 0.03 g/cm3, reaction duration: 3 h. (ꢀ) 01:04; (ꢁ)
01:06; (ꢂ) 01:08.
Fig. 8. Effect of temperature. 1,3-PDO to i-PA mole ratio::1:6, catalyst loading:
0.03 g/cm3, speed of agitation: 1000 rpm, reaction duration: 3 h. (ꢀ) 160 ◦C; (ꢁ)
170 ◦C; (ꢂ) 180 ◦C.
Please cite this article in press as: G.D. Yadav, D.P. Tekale, Selective mono-isopropylation of 1,3-propanediol with isopropyl alcohol
using heteropoly acid supported on K-10 clay catalyst, Catal. Today (2014), http://dx.doi.org/10.1016/j.cattod.2014.02.009

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7
Fig. 9. Second order kinetics.
conversion (%)
Selectivity (%)
When the reaction is far away from the equilibrium
Fig. 10. Arrhenius plot.
k2Ct2KAKBCACB
dCA
−
=
(11)
(12)
ꢀ
ꢂ
ꢁ
2
dt
1 +
KiCi
kRwCACB
=
(1 + KiCi)2
where kRw = k2Ct2KAKB and w is catalyst loading.If the adsorption
constants are negligible, then above equation reduces to
dCA
−
= kRwCACB
(13)
(14)
dt
CB0
CA0
= M
The molar ratio of 1,3-PDO to isopropyl alcohol at time t = 0. Then,
Eq. (13) can be written in terms of fractional conversion as
dXA
= kRwCA0(1 − XA)(M − XA)
(15)
dt
This upon integration leads to
ꢃ
ꢃ
ꢄ
ꢄ
(M − XA)
ln
ln
= kRwCA0(M − 1)t
= k(M − 1)t
M(1 − XA)
(M − XA)
(16)
M(1 − XA)
Fig. 11. Reusability study of the catalyst. (ꢁ) Conversion (%); ( ) selectivity (%).
where, k = kRwCA0
.
Thus, a plot of ln((M − XA)/M(1 − XA)) vs time at different tem-
peratures for M = 6 was made. The data fit very well thereby
validating the model based on second order kinetics (Fig. 9). Arrhe-
nius plot (Fig. 10) of ln k vs 1/T was made to estimate the apparent
activation energy of the reaction. The apparent activation energy
was found to be 12.27 kcal/mol. The value of activation energy sug-
gests that the reaction was intrinsically kinetically controlled.
without making up the catalyst amount with fresh catalyst. There
were losses during filtration amounting to ∼3%. Optimized reac-
tion parameters were used to carry out reusability study of the
catalyst (Fig. 11). It was observed that the catalyst was thrice
reusable for this reaction and characterization of catalyst showed
that there no structural and chemical change had occurred in the
catalyst.
3.4. Catalyst reusability
4. Conclusion
Reusability of the catalyst was studied by filtering the cata-
lyst after the experiment was completed. The catalyst was washed
and refluxed with methanol (3×50 ml) in order to remove any
adsorbed material from the catalyst pores and surface. It was then
was dried at 120 ◦C for 3 h and reused for the reaction three times
Valorization of glycerol and its derivatives is needed to
make biodiesel production economical. 1,3-Propanediol, a very
important bulk chemical can be converted into a number of
derivatives. Isopropylation of 1,3-propanediol was carried to form
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3-isopropoxy-1-propanol by using 20% w/w Cs2.5H0.5PW12O40/K-
10 as catalyst. The catalyst was fully characterized to understand its
efficacy. It is a robust and reusable catalyst. The reaction was found
to be 100% selective under the experimental conditions. Effect of
different reaction parameters such speed of agitation, 1,3-PDO to
isopropyl alcohol mole ratio, catalyst loading, and temperature was
studied to optimize the reaction conditions. Reaction mechanism
was discussed with the development of kinetic model. Apparent
activation energy was found to be 12.27 kcal/mol. FT-IR and sur-
face area analysis of the used catalyst confirmed that catalyst was
stable and reusable.
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Acknowledgements
G. D. Yadav acknowledges the support from the R. T. Mody Dis-
tinguished Professor Endowment of ICT and J. C. Bose National
Fellowship of Department of Science and Technology, New Delhi
(GOI). Devendra P. Tekale gratefully acknowledges the senior
research fellowship under CSIR-NMITLI and UGC-SAP in Green
Technology, Delhi.
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Please cite this article in press as: G.D. Yadav, D.P. Tekale, Selective mono-isopropylation of 1,3-propanediol with isopropyl alcohol
using heteropoly acid supported on K-10 clay catalyst, Catal. Today (2014), http://dx.doi.org/10.1016/j.cattod.2014.02.009