The studies on the limonene oxidation over the microporous TS-1 catalyst

Article abstract of DOI:10.1016/j.cattod.2015.11.008

The studies on the oxidation of limonene with 60 wt% hydrogen peroxide over the titanium silicalite TS-1 catalyst were carried out. The influence of the following parameters was examined: the temperature 0-120 °C, the molar ratio of limonene/H₂O₂ = 1:2-5:1, methanol concentration 60-95 wt%, TS-1 content 0.25-8 wt% and the reaction time 15 min to 11 days. The studies showed that the most beneficial conditions for the obtaining of high selectivity of 1,2-epoxylimonene, at simultaneously high values of the conversion of reactants and the efficiency of hydrogen peroxide, are as follows: the temperature 80 °C, the molar ratio of limonene/H₂O₂ = 1:1, the methanol concentration 80 wt%, the TS-1 content 3 wt% and the reaction time 10 days. Moreover, the research showed that the process of limonene oxidation is very complicated, because during this process also other very useful oxygenated derivatives of limonene can be obtained, for example: perillyl alcohol, carveol, carvone and 1,2-epoxylimonene diol. The studies on the reuse of the TS-1 catalyst showed that it is very stable catalyst at the studied conditions and it can be recycled to the oxidation process at least three times.

Full text of DOI:10.1016/j.cattod.2015.11.008

G Model
CATTOD-9899; No. of Pages9
ARTICLE IN PRESS
Catalysis Today xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Catalysis Today
journal homepage: www.elsevier.com/locate/cattod
The studies on the limonene oxidation over the microporous
TS-1 catalyst
Agnieszka Wróblewska∗, Edyta Makuch, Piotr Mia˛dlicki
Institute of Organic Chemical Technology, West Pomeranian University of Technology, Szczecin, Pulaskiego 10, PL 70-322 Szczecin, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
The studies on the oxidation of limonene with 60 wt% hydrogen peroxide over the titanium silicalite TS-1
catalyst were carried out. The influence of the following parameters was examined: the temperature
0–120 ◦C, the molar ratio of limonene/H2O2 = 1:2–5:1, methanol concentration 60–95 wt%, TS-1 content
0.25–8 wt% and the reaction time 15 min to 11 days. The studies showed that the most beneficial con-
ditions for the obtaining of high selectivity of 1,2-epoxylimonene, at simultaneously high values of the
conversion of reactants and the efficiency of hydrogen peroxide, are as follows: the temperature 80 ◦C,
the molar ratio of limonene/H2O2 = 1:1, the methanol concentration 80 wt%, the TS-1 content 3 wt% and
the reaction time 10 days. Moreover, the research showed that the process of limonene oxidation is very
complicated, because during this process also other very useful oxygenated derivatives of limonene can
be obtained, for example: perillyl alcohol, carveol, carvone and 1,2-epoxylimonene diol. The studies on
the reuse of the TS-1 catalyst showed that it is very stable catalyst at the studied conditions and it can be
recycled to the oxidation process at least three times.
Received 31 August 2015
Received in revised form
10 November 2015
Accepted 12 November 2015
Available online xxx
Keywords:
Limonene oxidation
1,2-Epoxylimonene
Carveol
Carvone
Perillyl alcohol
TS-1
© 2015 Elsevier B.V. All rights reserved.
1. Introduction
one vinylidene side group (the position of 8–9) [1–6]. The positions
of these unsaturated bonds are presented below:
Terpenes are renewable natural resources which are readily
available in the large scale. The examples of the compounds which
belong to the terpene family are: limonene, camphene, pinene,
vitamin A, steroids, carotenoids and natural rubber. Nowadays,
a special attention is directed to limonene, a natural, cheap and
easy available compound. This compound can be obtained in
large quantities from the orange peels (biomass and renewable
source), which are the waste product from the orange juice indus-
try. The purity of limonene obtained from orange peels reaches
97% and its word production amounts to 110–165 million pounds
per year. Limonene can be used as a fragrance, flavor, insecti-
cide or renewable solvent for coatings – replacing aromatic or
mineral oils. But the main application of limonene is the utiliza-
tion of this compound as a very valuable intermediate for organic
syntheses.
7
1
6
5
2
3
4
8
10
9
limonene
One of the main ways of transformation of limonene to valuable
compounds is its oxidation (including epoxidation) with hydrogen
peroxide or t-butyl hydroperoxide (TBHP) in the presence of vari-
ous heterogeneous catalysts, especially, titanium silicate catalysts.
But the literature shows that the limonene oxidation process is very
complicated and during this process it is possible to obtain a lot
of products. The main reaction is the epoxidation of the unsatu-
rated bond at the position of 1–2 in the limonene molecule and
The high reactivity of limonene is mainly connected with the
presence in the molecule of this compound two double bonds: one
vinylene group allocated in the cyclic ring (the position 1–2) and
∗
Corresponding author.
E-mail address: agnieszka.wroblewska@zut.edu.pl (A. Wróblewska).
http://dx.doi.org/10.1016/j.cattod.2015.11.008
0920-5861/© 2015 Elsevier B.V. All rights reserved.
Please cite this article in press as: A. Wróblewska, et al., The studies on the limonene oxidation over the microporous TS-1 catalyst,
Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.11.008

G Model
CATTOD-9899; No. of Pages9
ARTICLE IN PRESS
2
A. Wróblewska et al. / Catalysis Today xxx (2015) xxx–xxx
formation of 1,2-epoxylimonene. During the secondary reactions
the formation of the following by-products is observed (very often
at the appropriate conditions these reactions can be the main reac-
tions of this process): 1,2-epoxylimonene diol – the product of the
hydration of the epoxide ring in 1,2-epoxylimonene molecule, 8,9-
epoxylimonene and its diol (epoxidation and next hydration of the
epoxide ring at the position 8–9), carveol – the product of the allylic
oxidation at the position 6, carvone – the product of the oxida-
tive dehydrogenation of carveol molecule, 1–2,8–9-diepoxide and
its diol, perillyl alcohol – the product of the allylic oxidation at
the position 7 of limonene molecule, perillyl aldehyde and acid-
products of the oxidation of perillyl alcohol [4,5,7–11]. However,
the formation of perillyl alcohol as the predominant product was
observed mainly during oxidation of limonene in the presence of
bacteria, fungus and yeasts [12–15]. The possibility of the obtain-
ing the products of the cyclic allylic hydrogen abstraction and the
acyclic allylic hydrogen abstraction during the oxidation of ter-
penes (3-carene and ␣-pinene – compounds with the structure
similar to limonene) and especially limonene was described by
Rothenberg [16] and Wróblewska [17], respectively. Not only 1,2-
epoxylimonene but also other oxygenated derivatives of limonene
have a great advantage for many branches of the organic industry.
1,2-Epoxylimonene, its diol, carvone, carveol and perillyl alcohol
are very valuable intermediates which are applied in the production
of: flavors, perfumes, cosmetics, food additives [4,6,7], agrochemi-
cals, special fragrant polymers [18,19] and drugs used in the curing
of various kinds of cancer [20,21].
were used: hydrogen peroxide and TBHP [25,26]. The reaction was
performed in acetonitrile as the solvent and for the reaction time to
24 h. The following molar ratios of limonene/oxidizing agent were
used in these studies: the molar ratio of limonene/H2O2 = 1:1.3
and the molar ratio of limonene/TBHP = 1:1.6. For the reaction
with H2O2 the temperature of 70 ◦C and for TBHP the temperature
of 80 ◦C were applied. For all investigated oxidizing agents the
selectivity of 1,2-epoxylimonene was 100 mol%, but the conversion
of limonene amounted to 40 mol% for H2O2, and 60 mol% for TBHP.
The preliminary studies on the oxidation of limonene over
the TS-1 and Ti-SBA-15 catalysts (both catalysts were hydrother-
mally synthesized by the sol–gel method) were performed in the
glass reactor with the capacity of 25 cm3 equipped with the reflux
condenser, the thermometer and the magnetic stirrer and at the
following constant starting conditions: the temperatures of 0 ◦C,
40 ◦C, 80 ◦C and 120 ◦C, the molar ratio of limonene/H2O2 = 1:2,
methanol (solvent) concentration 80 wt% and the catalyst content
3 wt% [17]. The reaction time changed from 0.5 to 24 h. These
studies were only the preliminary studies which showed the pos-
sibility to perform the oxidation of limonene over the microporous
TS-1 catalyst (in spite of small pore size of this catalyst) and
over the Ti-SBA-15 mesoporous catalyst (it was possible to obtain
high selectivity of 1,2-epoxylimonene at the low selectivity of 1,2-
epoxylimonene diol). Moreover, these studies allow to propose the
possible mechanism of the formation of the appropriate products
of this process. It was observed during these studies that in almost
syntheses the main product of limonene oxidation process was not
1,2-epoxylimonene but perillyl alcohol.
There are few reports about utilization of the titanium silicate
catalysts in the liquid phase oxidation of limonene with hydrogen
peroxide or t-butyl hydroperoxide (TBHP). Until now the following
titanium silicalite catalysts were used in this process: Ti-MCM-41
[8,22–24], Ti-MMM-2 [10], Ti-SBA-15 [17,25,26] and TS-1 [17,26].
The studies on the oxidation of limonene over the Ti-MCM-41
catalyst were performed with such oxidizing agents as: hydrogen
peroxide and TBHP. Ti-MCM-41 catalyst used in the oxidation
of limonene was synthesized by the direct sol–gel method [8],
and also by grafting (Ti-grafted MCM-41) [22] or wetness and
vet impregnation [24]. The structure of the Ti-MCM-41 catalyst
obtained by the direct sol–gel method was silylated [23]. The
studies over the Ti-MCM-41 catalysts were performed at the
temperatures in the range of 70–85 ◦C, for the molar ratio of
limonene/H2O2 = 3.7:1 and for the reaction time in the range
of 0.5–7 h (in one case from 1 h to 24 h [22]). Over the direct
synthesized Ti-MCM-41 catalyst the selectivity of the epoxide
compounds (the sum of 1,2- and 8,9-epoxylimonene) was about
60 mol%. Carveol and carvone were formed with the selectivity of
20 mol%, diepoxylimonene with the selectivity of about 10 mol%
and glycols about 10 mol%. The conversion of limonene changed
from 36 to 80 mol%. Over the silylated Ti-MCM-41 catalyst the
results of limonene epoxidation were very close, and the only one
difference was a higher value of the hydrogen peroxide efficiency
[23]. The two other methods of Ti-MCM-41 preparation (wetness
and vet impregnation) do not cause important changes in the
catalyst activity, only a slight decrease in the epoxides selectivity
was observed [24]. The utilization of TBHP in the oxidation of
limonene caused that after the reaction time of 24 h the conversion
of limonene was 62 mol% and the selectivity of 1,2-epoxylimonene
amounted to 75 mol%. Over the Ti-MMM-2 catalyst the oxidation of
limonene was performed in acetonitrile as the solvent, at the tem-
perature of 60 ◦C and for the molar ratio of limonene/H2O2 = 1:2
[10]. These studies showed that the amount of the obtained epox-
ide compound was three times higher than the other products
and the amount of carvone was higher than carveol. Moreover,
in the post-reaction mixtures also perillyl alcohol was detected
[10]. During the studies over the Ti-SBA-15 catalyst synthesized
by grafting titanium on a SBA-15 structure two oxidizing agents
The aim of this work is the detailed studies on limonene oxida-
tion with 60 wt% hydrogen peroxide over the TS-1 catalyst – the
titanium silicate zeolite type material. This work is a continuation
of the paper [17], where were presented the preliminary studies for
the process of limonene oxidation over TS-1 catalysts but over this
catalyst the broad studies on limonene oxidation have not been per-
formedyet. Itwillbeveryinterestingtodescribethefullinfluenceof
the following technological parameters on the course of limonene
oxidation: the temperature, the molar ratio of limonene/H2O2,
methanol (solvent) concentration, the TS-1 catalyst content, and
the reaction time. It will be also helpful in the establishing of the
most beneficial conditions of 1,2-epoxylimonene obtaining, tak-
ing into account the values of the main functions describing this
process. Also very important is the presentation the conditions of
the formation the by-products of this process, because these by-
products very often can be the main products of limonene oxidation
process and they have a lot of applications. Also the possibility of
the reuse of the TS-1 catalyst was examined on this work.
2. Material and methods
The TS-1 catalyst was prepared according to the method
described by Thangaraj et al. [27]. The molar ration of Si/Ti in the
gel before crystallization was 64:1. The Ti content in this catalyst
was 3.01 wt%, the specific surface area amounted to 372 m2/g, the
size of the pores achieved 0.5 nm and the crystal size amounted to
0.5 ␮m. The full characteristic of this catalyst was presented in our
previous articles [17,28].
In the studies on the oxidation of limonene the following raw
materials were used: R-(+)-limonene (97%, Sigma), hydrogen per-
oxide (60 wt% water solution, Chempur), and methanol (solvent)
(analytical grade, Chempur). During these studies the influence
of the following parameters was tested: the temperature in the
range of 0–120 ◦C (the concentration of limonene amounted to
about 13.7 wt% and hydrogen peroxide 3.4 wt%), the molar ratio
of limonene/H2O2 = 1:2–5:1 (the values of limonene and hydro-
gen peroxide concentration in relation to the appropriate molar
Please cite this article in press as: A. Wróblewska, et al., The studies on the limonene oxidation over the microporous TS-1 catalyst,
Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.11.008

G Model
CATTOD-9899; No. of Pages9
ARTICLE IN PRESS
A. Wróblewska et al. / Catalysis Today xxx (2015) xxx–xxx
3
Table 1
The values of limonene and hydrogen peroxide concentration in relation to the appropriate molar ratio of reactants and methanol concentration.
Molar ratio of limonene/H2O2
Limonene concentration (wt%)
Hydrogen peroxide concentration (wt%)
1:2
10.7
5.3
1:1.5
12.1
4.4
1:1
13.7
3.4
2:1
16.5
2.5
3:1
17.2
1.6
4:1
15.2
0.9
5:1
16.1
0.8
–
–
–
Methanol concentration (wt%)
60
65
70
75
80
85
90
95
Limonene concentration (wt%)
Hydrogen peroxide concentration (wt%)
27.4
6.8
24.1
6.0
20.5
5.1
17.2
4.2
13.7
3.4
10.4
2.5
6.9
1.7
3.5
0.9
ratio of reactants are presented in Table 1), the methanol (solvent)
concentration of 60–95 wt% (the values of limonene and hydro-
gen peroxide concentration in relation to the appropriate methanol
concentration are presented in Table 1), the TS-1 catalyst content
of 0.25–8 wt% (the concentration of limonene changed from 14.4 to
13.1 wt% and the concentration of hydrogen peroxide from 3.4 to
3.3 wt%) and the reaction time 15 min to 11 days (the concentration
of limonene amounted to about 13.7 wt% and hydrogen peroxide
3.4 wt%).
Moreover, the starting parameters were as follows: the molar
ratio of limonene/H2O2 = 1:1 (the concentration of limonene
amounted to about 13.7 wt% and hydrogen peroxide 3.4 wt%), the
methanol concentration of 80 wt%, the TS-1 catalyst content of
3 wt%, the reaction time 3 h, and the intensity of stirring 500 rpm.
The process was carried out in a glass reactor with the capacity
of 50 cm3 equipped with a reflux condenser, a thermometer and a
magnetic stirrer. The raw materials were introduced into reactor
in the following order: the TS-1 catalyst, limonene, methanol and
60 wt% water solution of hydrogen peroxide. The temperature was
achieved with help of silicone oil bath. During the studies also blank
experiment was done and it shows that hydrogen peroxide did not
oxidize limonene without the catalyst.
Samples at different reaction times were analyzed by GC-
method on the Focus apparatus with a flame-ionization detector
and fitted with the Restek Rtx-WAX capillary column filled with
polyethylene glycol. The detailed information about condition of
the GC analyzes are presented in our previous work [17]. Reac-
tion products were also identified by the GC–MS method. The
hydrogen peroxide conversion was measured by the iodometric
titration method. On the basis of the mass balances calculated for
each synthesis, the main functions describing the process were
catalyst content of 3 wt% and the reaction time 10 days. Three cycles
(runs) of the recycling of the catalyst were performed.
3. Results and discussion
The results of the studies on the influence of temperature on the
course of limonene oxidation were presented in Figs. 1 and 2.
Fig. 1 shows that during increasing of the temperature of
the limonene oxidation the conversion of limonene and the effi-
ciency of hydrogen peroxide conversion increase and take very
close and not very high values. The highest values these functions
are obtained at the temperature of 120 ◦C, 12 mol% and 17 mol%,
respectively. The conversion of hydrogen peroxide has the high-
est values for the lowest temperatures (above 90 mol%) and for the
higher temperatures it decreases. The comparison of two functions:
the efficiency of hydrogen peroxide conversion and the conversion
of hydrogen peroxide present that the most of hydrogen peroxide
amount undergoes an ineffective decomposition during the oxida-
tion process. This decomposition undergoes at the active centers
of Ti in the structure of the catalysts and also it can be a result of
the influence of temperature (the thermal decomposition). At the
higher temperatures this ineffective decomposition is hindered and
it can be probably caused by blocking the access of hydrogen per-
oxide molecules to the active centers od Ti by the great number of
organic molecules (limonene and the products of limonene trans-
formation) – at the higher temperatures the products of limonene
transformation are formed faster and in the greater amount. On
the other hand, the active centers of Ti not only can catalyze the
transformation of limonene by the reactions with hydrogen perox-
ide but also the ineffective decomposition of hydrogen peroxide.
The capability of Ti active centers to the ineffective decomposition
of hydrogen peroxide can be probably changed by the changing of
the temperature of the process performing. It is possible that at the
higher temperatures this second process is hindered but still it is
very significant. The phenomenon of the decomposition of hydro-
gen peroxide under influence of the raised temperatures should
also be taken into consideration but the quantitative establishing
this way of the ineffective decomposition of hydrogen peroxide is
difficult.
determined: the selectivities of the appropriate products (Sproduct/L
,
where l-limonene), the conversion of limonene (CL), the conversion
of hydrogen peroxide (CH 2 ) and the selectivity of transformation
O
to organic compounds in 2relation to hydrogen peroxide consumed
(the efficiency of hydrogen peroxide conversion) – Sorg. comp./H
.
O
The studies on the possibility of the reuse (recycling) of the TS2-1
catalyst in the process of limonene oxidation were performed at the
conditions established first as the most beneficial for this process:
the temperature of 80 ◦C, the molar ratio of limonene/hydrogen
peroxide = 1:1, the methanol concentration of 80 wt%, the TS-1
2
Fig. 2 shows that the following directions of the transformation
of limonene during the reaction with 60 wt% hydrogen peroxide
and over the TS-1 catalyst are possible:
allylic oxidation
at position 7
1) epoxidation at position 1-2
1) allylic oxidation
and next hydration of the obatined 1,2-epoxide
at position 6
to 1,2-diol
and next oxidative
dehydrogenation of
the obatined carveol
to carvone
2) direct carvone
formation by oxidation
at position 6
7
2) direct fomation of 1,2-diol by hydroxylation
at positions 1 and 2
1
6
5
2
3
4
8
10
9
limonene
Please cite this article in press as: A. Wróblewska, et al., The studies on the limonene oxidation over the microporous TS-1 catalyst,
Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.11.008

G Model
CATTOD-9899; No. of Pages9
ARTICLE IN PRESS
4
A. Wróblewska et al. / Catalysis Today xxx (2015) xxx–xxx
The formation of the appropriate products (1,2-epoxylimonene,
1,2-epoxylimonene diol, carveol, carvone and perillyl alcohol) can
be described by the following equations:
second product (carvone) can be formed directly by the oxidation
of limonene at this position or by the oxidative dehydrogenation
carveol to carvone (the temperatures of 80 and 120 ◦C). Perillyl
alcohol is the only product of limonene oxidation at the position
7 (perillyl aldehyde or perillyl acid were not detected in the
post-reaction mixtures). The obtained results also show that
from the temperature of 40 ◦C and for the higher temperatures
the main product of the studied process is perillyl alcohol not
1,2-epoxylimonene. At the start of these studies as the basis of the
choosing of the most beneficial temperature for the next steps of
our studies were taken the following main functions describing
the oxidation process: the selectivity of 1,2-epoxylimonene, the
conversion of limonene and the efficiency of hydrogen peroxide
conversion. But our studies showed that: (1) the lowest temper-
atures at which the selectivity of the epoxide is very high are not
beneficial because very small values of the conversion of limonene
and the efficiency of hydrogen peroxide conversion are obtained
and (2) it is possible no one direction of the oxidation of limonene
in this process Thus, taking mainly into account: (1) low values of
the conversion of limonene and the efficiency of hydrogen peroxide
conversion and (2) the great importance of the other products of
this process (especially, perillyl alcohol), the temperature of 80 ◦C
was taken as the most beneficial for further studies on this process.
The results of the studies on the influence of the molar ratio
of limonene/hydrogen peroxide on the course of the process of
limonene oxidation are presented in Figs. 3 and 4.
Fig. 3 presents that the molar ratio of limonene/hydrogen per-
oxide has not significant influence on the conversion of limonene
which takes very small values. The greater influence this parame-
ter has on the conversion of hydrogen peroxide and the efficiency
of hydrogen peroxide conversion but the highest values of the effi-
ciency of hydrogen peroxide are obtained for the lowest values of
the hydrogen peroxide conversion (the molar ration of reactants
2:1 and 3:1). For the molar ratio amounted to 2 and higher limonene
molecules, which are in the excess in reaction medium, limit the
access of hydrogen peroxide molecules to the active centers, thus
the conversion of hydrogen peroxide decreases the same as the
efficiency of hydrogen peroxide conversion. For the molar ratios of
limonene/hydrogen peroxide below 1 high values of the conversion
of hydrogen peroxide can be a result of the thermal decomposition
of this oxidizing agent, thus hydrogen peroxide does not take part
in the oxidation reactions and the effective conversion of hydrogen
peroxide takes very small values.
OH
OH
O
+ H2O2
TS-1
+ H2O
-H2O
1,2-epoxylimonene diol
1,2-epoxylimonene
limonene
+ H2O2
TS-1
OH
OH
1,2-epoxylimonene diol
+ H2O2
TS-1
HO
O
+ 1/2H2O2
-H2O
-H2O
carvone
carveol
limonene
-2H2O
+ 2H2O2
TS-1
O
carvone
Fig. 4 shows that independent of the molar ratio of reactants the
main product of the process is perillyl alcohol. Excluding the molar
ratio of limonene/hydrogen peroxide = 1, the selectivity of perillyl
alcohol amounts always above 80 mol% (in one case 100 mol% – the
molar ratio of limonene/hydrogen peroxide = 1:2). All products of
the oxidation process (1,2-epoxylimonen, its diol, carveol, carvone
and perillyl alcohol) can be only obtained for the equimolecular
molar ratio of reactants and simultaneously at this molar ratio it
is possible to obtain the highest selectivity of 1,2-epoxylimonene
from the studied molar ratios. Taking into account the values of
the selectivities of the products of this process, especially 1,2-
epoxylimonene, the equimolecular molar ratio of reactants was
taken as the most beneficial at this stage of studies.
The results of the studies on the influence of methanol con-
centration on the course of the process of limonene oxidation are
presented in Figs. 5 and 6.
The methanol (solvent) concentration in the range of 60–95 wt%
has not a significant influence on the conversion of limonene, the
conversion of hydrogen peroxide and the efficiency of hydrogen
peroxide conversion. On the other hand, the influence of methanol
concentration is visible taking into account the values of the
selectivities of the appropriate products. Below the concentration
of methanol 80 wt % but above 60 wt% four products are obtained:
CH2OH
+ H2O2
TS-1
-H2O
perillyl alcohol
limonene
The product of limonene epoxidation-1,2-epoxylimonene is
formed as the only product at the temperature of 0 ◦C, the increase
of the temperature causes the decrease of the selectivity of this
epoxide and increase in the values of the selectivities of diol of this
epoxide and the products of limonene oxidation at the positions:
6 (carveol, carvone) and 7 (perillyl alcohol). It shows that at higher
temperatures the epoxidation of unsaturated bond is hindered
and more preferred are oxidation reactions at positions 6 and 7.
Moreover, our results show that during limonene oxidation at the
position 6 we can obtain two products: carveol and carvone. The
Please cite this article in press as: A. Wróblewska, et al., The studies on the limonene oxidation over the microporous TS-1 catalyst,
Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.11.008

G Model
CATTOD-9899; No. of Pages9
ARTICLE IN PRESS
A. Wróblewska et al. / Catalysis Today xxx (2015) xxx–xxx
5
100
90
80
70
60
50
40
30
20
10
0
0
20
40
60
80
100
120
Temperature (ºC)
CL
CH2O2
Sorg comp/H2O2
Fig. 1. The influence of the temperature on the conversion of limonene (CL), the conversion of hydrogen peroxide (CH 2 ) and the efficiency of hydrogen peroxide conversion
O
2
(Sorg. comp./H
) – the molar ratio of limonene/H2O2 = 1:1, the methanol concentration of 80 wt%, the TS-1 catalyst content of 3 wt%, the reaction time 3 h, and the intensity of
O
2
stirring 500 r2pm.
1,2-epoxylimonene, its diol, carveol and perillyl alcohol – for
the methanol concentration of 60 wt% epoxide compound is not
formed. For the methanol concentration of 85 wt% three products
are obtained – 1,2-epoxylimonene diol, carveol and perillyl alcohol,
and above the concentration of methanol 85 wt% only two products
are detected in the post-reaction mixture – 1,2-epoxylimonene
diol and perillyl alcohol. These results show that the increase of
methanol concentration in the reaction mixtures does not limit the
hydration of the epoxide ring in the 1,2-epoxylimonene molecule
(or hydroxylation at the positions 1 and 2). On the other hand,
the increase in the amount of methanol molecules cusses that the
selectivity of perillyl alcohol rises which shows that the allylic
oxidation at the position 7 in the limonene molecule becomes more
preferable. It can be connected with the stability of the transition
state which is formed during the allylic oxidation at the position
7 (the detailed description of this structure is presented in the
paper [17] – transition state II). Probably, the methanol molecules
help to stabilize this transition state in which the formation of the
positive charge is observed. Without this positive charge the allylic
oxidation at the position 7 cannot undergo. Taking mainly into
account the values of the selectivity of the 1,2-epoxylimonene the
methanol concentration of 80 wt% was taken as the most beneficial
for the next stages of these studies.
The results of the studies on the influence of the TS-1 catalyst
content on the course of the process of limonene oxidation are
presented in Figs. 7 and 8.
The TS-1 catalyst content has not significant influence on the
conversion of limonene, the conversion of hydrogen peroxide and
the efficiency of hydrogen peroxide conversion. But this techno-
logical parameter influences on the selectivities of the obtained
products. Generally, the increase of the TS-1 catalyst content causes
increase in the number of the obtain products. For low TS-1
contents (to 2 wt%) the main products of the process are: peril-
lyl alcohol, 1,2-epoxylimonene and its diol. Carveol starts to be
detected in the post-reaction mixtures from the 2 wt% TS-1 con-
tent, and carvone is detected for the catalyst TS-1 content 3 wt%.
The increase in the TS-1 content cases simultaneously the rising in
the hydration of the epoxide ring in 1,2-epoxylimonene molecule
Fig. 2. The influence of the temperature on the selectivities of the main products of limonene oxidation: (12EPL: 1,2-epoxylimonene; 12EPLDIOL: 1,2-epoxylimonene diol;
PA: perillyl alcohol) – the molar ratio of limonene/H2O2 = 1:1, the methanol concentration of 80 wt%, the TS-1 catalyst content of 3 wt%, the reaction time 3 h, and the intensity
of stirring 500 rpm.
Please cite this article in press as: A. Wróblewska, et al., The studies on the limonene oxidation over the microporous TS-1 catalyst,
Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.11.008

G Model
CATTOD-9899; No. of Pages9
ARTICLE IN PRESS
6
A. Wróblewska et al. / Catalysis Today xxx (2015) xxx–xxx
100
90
80
70
60
50
40
30
20
10
0
[1:2]
[1:1,5]
[1:1]
The molar ratio of L/H2O2
CL CH2O2 Sorg comp
[2:1]
[3:1]
[4:1]
[5:1]
Fig. 3. The influence of the molar ratio of limonene/hydrogen peroxide on the conversion of limonene (CL), the conversion of hydrogen peroxide (CH 2 ) and the efficiency
O
of hydrogen peroxide conversion (Sorg. comp./H 2 ) – the temperature of 80 ◦C, the methanol concentration of 80 wt%, the TS-1 catalyst content of 3 wt%2, the reaction time 3 h,
O
2
and the intensity of stirring 500 rpm (the concentration of limonene was 10.7, 12.1, 13.7, 16.5, 17.2, 15.2 and 16.1 wt% for the molar ratio of limonene/H2O2 = 1:2, 1:1.5, 1:1,
2:1, 3:1, 4:1 and 5:1, respectively).
(or hydroxylation at the positions 1 and 2). Taking into account
the values of the 1,2-epoxylimonene selectivity, the conversion of
limonene and the efficiency of hydrogen peroxide conversion the
TS-1 catalyst content of 3 wt% was taken as the most beneficial for
the examination of the influence of the reaction time on the course
of limonene oxidation.
The results of the studies on the influence of the reaction time
on the course of the process of limonene oxidation are presented
in Figs. 9 and 10.
Figs. 9 and 10 show that the reaction time is one of the most
important parameters of this process because it influences not
only on the values of the selectivities of the products of this
process but also on the conversions of the raw materials and the
efficiency of hydrogen peroxide conversion. The prolongation of
the reaction time to 11 days causes the increase in the values of the
conversion of limonene, the conversion of hydrogen peroxide, and
the efficiency of hydrogen peroxide conversion, and the highest
values of these functions are obtained for the time of 11 days –
Fig. 9. It results from Fig. 10 that for the reaction time of 45 min
and 1 h the whole amount of 1,2-epoxylimonene formed is trans-
formed to 1,2-epoxylimonene diol (or this compound is formed
by direct hydroxylation at positions 1 and 2) and the second
product of this process is perillyl alcohol. The prolongation the of
the reaction time causes the increase in the values of carveol and
1,2-epoxylimonene selectivities and the decrease in the selectivity
of perillyl alcohol. It shows that for shorter reaction time more
preferable is the epoxidation of the unsaturated bond at the posi-
tion of 1–2 and allylic oxidation at the position of 7, but during the
prolongation of the reaction time the tendency for oxidation of the
allylic position 6 rises the same as epoxidation of the unsaturated
bond at the position of 1–2 and moreover, for longer time the
1,2-epoxylimonene molecules are more stable in the post-reaction
mixture (their tendency for hydration process decreases or direct
hydroxylation at positions 1 and 2 undergoes slower). The analysis
Fig. 4. The influence of the molar ratio limonene/hydrogen peroxide on the selectivities of the main products of limonene oxidation: (12EPL: 1,2-epoxylimonene; 12EPLDIOL:
1,2-epoxylimonene diol; PA: perillyl alcohol) – the temperature of 80 ◦C, the methanol concentration of 80 wt%, the TS-1 catalyst content of 3 wt%, the reaction time 3 h, and
the intensity of stirring 500 rpm (the concentration of limonene was 10.7, 12.1, 13.7, 16.5, 17.2, 15.2 and 16.1 wt% for the molar ratio of limonene/H2O2 = 1:2, 1:1.5, 1:1, 2:1,
3:1, 4:1 and 5:1, respectively).
Please cite this article in press as: A. Wróblewska, et al., The studies on the limonene oxidation over the microporous TS-1 catalyst,
Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.11.008

G Model
CATTOD-9899; No. of Pages9
ARTICLE IN PRESS
A. Wróblewska et al. / Catalysis Today xxx (2015) xxx–xxx
7
100
90
80
70
60
50
40
30
20
10
0
60
65
70
75
80
85
90
95
Methanol concetration (wt %)
CL
CH2O2 Sorg comp/H2O2
Fig. 5. The influence of methanol concentration on the conversion of limonene (CL), the conversion of hydrogen peroxide (CH 2 ) and the efficiency of hydrogen peroxide
O
conversion (Sorg. comp./H 2 ) – the temperature of 80 ◦C, the molar ratio of limonene/H2O2 = 1, the TS-1 catalyst content of 3 wt2%, the reaction time 3 h, and the intensity of
O
2
stirring 500 rpm.
Fig. 6. The influence of methanol concentration on the selectivities of the main products of limonene oxidation: (12EPL: 1,2-epoxylimonene; 12EPLDIOL: 1,2-epoxylimonene
diol; PA: perillyl alcohol) – the temperature of 80 ◦C, the molar ratio of limonene/H2O2 = 1, the TS-1 catalyst content of 3 wt%, the reaction time 3 h, and the intensity of stirring
500 rpm.
100
90
80
70
60
50
40
30
20
10
0
0
0,5
1
1,5
2
2,5
3
3,5
TS-1 content (wt %)
CH2O2 Sorg comp/H2O2
4
4,5
5
5,5
6
6,5
7
7,5
8
8,5
CL
Fig. 7. The influence of the TS-1 catalyst content on the conversion of limonene (CL), the conversion of hydrogen peroxide (CH 2 ) and the efficiency of hydrogen peroxide
O
conversion (Sorg. comp./H 2 ) – the temperature of 80 ◦C, the molar ratio of limonene/H2O2 = 1, the methanol concentration of 802wt%, the reaction time 3 h, and the intensity
O
2
of stirring 500 rpm.
Please cite this article in press as: A. Wróblewska, et al., The studies on the limonene oxidation over the microporous TS-1 catalyst,
Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.11.008

G Model
CATTOD-9899; No. of Pages9
ARTICLE IN PRESS
8
A. Wróblewska et al. / Catalysis Today xxx (2015) xxx–xxx
Fig. 8. The influence of the TS-1 catalyst content on the selectivities of the main products of limonene oxidation: (12EPL: 1,2-epoxylimonene; 12EPLDIOL: 1,2-epoxylimonene
diol; PA: perillyl alcohol) – the temperature of 80 ◦C, the molar ratio of limonene/H2O2 = 1, the methanol concentration of 80 wt%, the reaction time 3 h, and the intensity of
stirring 500 rpm.
100
90
80
70
60
50
40
30
20
10
0
0
15 30 45 1 h 2 h 3 h 4 h 5 h
1
2
3
4
5
6
7
8
9
10 11
day daysdaysdaysdaysdaysdaysdaysdaysdaysdays
Reaction time
min min min min
CL
CH2O2 Sorg comp/H2O2
Fig. 9. The influence of the reaction time on the conversion of limonene (CL), the conversion of hydrogen peroxide (CH 2 ) and the efficiency of hydrogen peroxide conversion
O
2
(Sorg. comp./H 2 ) – the temperature of 80 ◦C, the molar ratio of limonene/H2O2 = 1, the methanol concentration of 80 wt%, the TS-1 content 3 wt% and the intensity of stirring
O
2
500 rpm.
Fig. 10. The influence of the reaction time on the selectivities of the main products of limonene oxidation: (12EPL: 1,2-epoxylimonene; 12EPLDIOL: 1,2-epoxylimonene diol;
PA: perillyl alcohol) – the temperature of 80 ◦C, the molar ratio of limonene/H2O2 = 1, the methanol concentration of 80 wt%, the TS-1 content 3 wt% and the intensity of
stirring 500 rpm.
Please cite this article in press as: A. Wróblewska, et al., The studies on the limonene oxidation over the microporous TS-1 catalyst,
Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.11.008

G Model
CATTOD-9899; No. of Pages9
ARTICLE IN PRESS
A. Wróblewska et al. / Catalysis Today xxx (2015) xxx–xxx
9
of the results obtained during the examinations of the reaction
time influence shows that taking into account the selectivity of
1,2-epoxylimonene, the conversions of reactants and the efficiency
of hydrogen peroxide conversion the most beneficial time for this
process perfuming is the time of 10 days.
The studies on the possibility of the reuse of the TS-1 catalyst in
the process of limonene oxidation performed at the most beneficial
conditions for this process, established at the previous stages of this
work showed that the catalysts can be recycled 3 times without loss
of the activity.
[4] A. Corma, S. Iborra, A. Velty, Chemical routes for the transformation of
biomass into chemicals, Chem. Rev. 107 (2007) 2411–2502.
[5] A. Pena, S. Veiga, M. Sapelli, N. Martinez, V. Marquez, E. Dellacassa, J. Bussi,
Limonene oxidation by molecular oxygen under solvent-free conditions: the
influence of peroxides and catalysts on the reaction rate, React. Kinet. Mech.
Cat. 107 (2012) 263–275.
[6] J.L.F. Monteiro, C.O. Veloso, Catalytic conversion of terpenes into fine
chemicals, Top. Catal. 27 (1–4) (2004) 169–180.
[7] A.M. Santa, J.C. Vergara, L.A. Palacio, A. Echavarria, Limonene epoxidation by
molecular sieves zincophosphates and zincochromates, Catal. Today 133–135
(2008) 80–86.
[8] M.V. Cagnoli, S.G. Casuscelli, A.M. Alvarez, J.F. Bengoa, N.G. Gallegos, N.M.
Samaniego, M.E. Crivello, G.E. Ghione, C.F. Perez, E.R. Herrero, et al., Clean
limonene epoxidation using Ti-MCM-41 catalyst, Appl. Catal. A: Gen. 287
(2005) 227–235.
[9] P.A. Robles-Dutenhefner, B.B.N.S. Brandao, L.F. de Sousa, E.V. Gusevskaya,
Solvent-free chromium catalyzed aerobic oxidation of biomass-based alkenes
as a route to valuable fragrance compounds, Appl. Catal. A: Gen. 399 (2011)
171–178.
[10] A.J. Bonon, D. Mandelli, O.A. Kholdeeva, M.V. Barmatova, Y.N. Kozlov, G.B.
Shulpin, Oxidation of alkene and olefins with hydrogen peroxide in
acetonitrile solution catalyzed by a mesoporous titanium-silicate Ti-MMM-2,
Appl. Catal. A: Gen. 365 (2009) 96–104.
[11] Z. Strassberger, E.V. Ramos-Fernandez, A. Boonstra, R. Jorna, S. Tanase, G.
Rothenberg, Synthesis, characterization and testing of a new
V2O5/Al2O3–MgO catalyst for butane dehydrogenation and limonene
oxidation, Dalton Trans. 42 (2013) 5546–5552.
[12] W.A. Duetz, H. Bouwmeester, J.B. van Beilen, B. Witholt, Biotransformation of
limonene by bacteria, fungi, yeasts, and plants, Appl. Microbiol. Biotechnol. 61
(2003) 269–277.
[13] J. Alonso-Gutierrez, R. Chan, T.S. Batth, P.D. Adamas, J.D. Keasling, Ch.J.
Petzold, T.S. Lee, Metabolic engineering of Escherichia coli for limonene and
perillyl alcohol production, Metab. Eng. 19 (2013) 33–41.
[14] E.G. Funhoff, J. Salzmann, U. Bauer, B. Witholt, J.B. van Beilen, Hydroxylation
and epoxidation reactions catalyzed by CYO153 enzymes, Enzyme Microb.
Technol. 40 (2007) 806–812.
4. Conclusions
The presented studies showed that all examined parameters
(the temperature, the molar ratio of limonene/hydrogen perox-
ide, the methanol concentration, the TS-1 catalyst content and the
reaction time) influenced on the course of the process of limonene
oxidation but the highest influence had the temperature and the
reaction time. These parameters not only influenced on the selec-
tivities of the products but also on the conversions of the reactants
and the efficiency of hydrogen peroxide conversion. During the
studies on the influence of the temperature, the product of the
epoxidation of limonene at the position of 1–2 was formed with the
highest selectivity only at the lowest temperatures, the increase in
the temperature hindered the epoxidation process and privileged
the oxidation at the positions of 6 and 7. Studies on the influence of
the reaction time showed that for the short time the main products
were perillyl alcohol and 1,2-epoxylimonene diol. The prolongation
of the reaction time changes the main directions of the oxidation
because next product was formed – carveol (the allyl oxidation at
the position 6) and the stability of the epoxide ring at the studied
conditions raised.
[15] M. van der Werf, P.M. Keijzer, P.H. Schaft, Xanthobacter sp. C20 contains a
novel bioconversion pathway for limonene, J. Biotechnol. 84 (2000) 133–143.
[16] G. Rothenberg, Y. Yatziv, Y. Sasson, Comparative autoxidation of 3-carene and
␣-pinene: factors governing regioselective hydrogen abstraction reactions,
Tetrahedron 54 (1998) 593–598.
[17] A. Wróblewska, The epoxidation of limonene over the TS-1 and Ti-SBA-15
catalysts, Molecules 19 (2014) 19907–19922.
Generally, the process of limonene epoxidation is very compli-
cated, mainly because the various directions of the oxidation in the
limonene molecule. It is difficult to establish such conditions for
this process at which only one product is obtained. The easiest it
can be done for 1,2-epoxylimonene (but at very low conversions
of the reactants and at the temperatures below of 20 ◦C) and for
perillyl alcohol. At the higher conversions of the reactants and the
higher values of the efficiency of hydrogen peroxide conversion
the selectivity of 1,2-epoxylimonene does not achieve of 100 mol%
because the other products of this process are formed, especially
carveol, 1,2-epoxylimonene diol and perillyl alcohol. But taking into
account applications of these products it is also beneficial.
[18] Ch.M. Byrne, S.D. Allen, E.B. Lobkovsky, G.W. Coates, Alternating
copolymerization of limonene oxide and carbon dioxide, J. Am. Chem. Soc.
126 (2004) 11404–11405.
[19] P.A. Wilborn, F. Chu, Ch. Tang, Progress in renewable polymers from natural
terpenes, terpenoids, and rosin, Macromol. Rapid Commun. 34 (2013) 8–37.
[20] A. Gupta, S.P. Stratton, P.B. Myrdal, An HPLC method for quantitation of
perillyl alcohol in a topical pharmaceutical cream formulation, J. Pharm.
Biomed. Anal. 37 (2005) 447–452.
[21] A. Gupta, P.B. Myrdal, Development of a perillyl alcohol topical cream
formulation, Int. J. Pharm. 269 (2004) 373–383.
[22] Ch. Berlini, M. Guidotti, G. Moretti, R. Psaro, N. Ravasio, Catalytic epoxidation
of unsaturated alcohols on Ti-MCM-41, Catal. Today 60 (2000) 209–225.
[23] M.V. Cagnoli, S.G. Casuscelli, A.M. Alvarez, J.F. Bengoa, N.G. Gallegos, M.E.
Crivello, E.R. Herrero, S.G. Marchetti, Ti-MCM-41 silylation: development of a
simple methodology for its estimation. Silylation effect on the activity and
selectivity in the limonene oxidation with H2O2, Catal. Today 107–108 (2005)
397–403.
[24] D. Marino, N. Gallegos, J.F. Bengoa, A.M. Alvarez, M.V. Cagnoli, S.G. Casuscelli,
E.R. Herrero, S.G. Marchetti, Ti-MCM-41 catalysts prepared by post-synthesis
methods, limonene epoxidation with H2O2, Catal. Today 133–135 (2008)
632–638.
[25] F. Chiker, F. Launay, J.P. Nogier, J.L. Bonardet, Green epoxidation on
Ti-mesoporous catalysts, Environ. Chem. Lett. 1 (2003) 117–120.
[26] F. Chiker, F. Launay, J.P. Nogier, J.L. Bonardet, Green and selective epoxidation
of alkenes catalysed by new TiO2–SiO2 SBA mesoporous solids, Green Chem. 5
(2003) 318–322.
Moreover, the studies on the recycling of the TS-1 catalyst
showed that it is very stable catalyst at the studied conditions and
it can be recycled to the oxidation process at least three times.
References
[1] M. Bahr, A. Bitto, R. Mulhaupt, Cyclic limonene dicarbonate as a new
monomer for non-isocyanate oligo- and polyurethanes (NIPU) based upon
terpenes, Green Chem. 14 (2012) 1447–1454.
[27] A. Thangaraj, R. Kumar, P. Ratnasamy, Direct catalytic hydroxylation of
benzene with hydrogen peroxide over titanium–silicalite zeolites, Appl. Catal.
57 (1990) L1–L3.
[28] A. Wróblewska, A. Fajdek, Epoxidation of allyl alcohol to glycidol over the
microporous TS-1 catalyst, J. Hazard. Mater. 179 (2010) 258–265.
[2] M. Firdaus, M.A.R. Meier, Renewable polyamides and polyurethanes derived
from limonene, Green Chem. 15 (2013) 370–380.
[3] R. Ciriminna, M. Lomeli-Rodriguez, P. Demma Cara, J.A. Lopez-Sanchez, M.
Pagliaro, Limonene: a versatile chemical of the bioeconomy, Chem. Commun.
50 (2014) 15288–15296.
Please cite this article in press as: A. Wróblewska, et al., The studies on the limonene oxidation over the microporous TS-1 catalyst,
Catal. Today (2015), http://dx.doi.org/10.1016/j.cattod.2015.11.008