Epoxidation of allyl chloride with H2O2 catalyzed by three structurally related quaternary ammonium modified polyoxophosphotungstates

Article abstract of DOI:10.1016/j.apcata.2020.117846

The one-step epoxidation of allyl chloride has always been a great challenge for the industrial production. The key of this technology is to find efficient and friendly catalyst. In this paper, three structurally related quaternary ammonium modified polyoxophosphotungstates were synthesized by green and facile method. Among them, [C₁₆H₃₃(CH₃)₃N]₃PW₄O₂₄ and [π-C₅H₅NC₁₆H₃₃]₃PW₄O₂₄ are reaction-controlled phase transfer catalyst (RPTC) and [(C₁₈H₃₇)₂(CH₃)₂N]₃PW₄O₂₄ is temperature-controlled phase transfer catalyst (TPTC). All three catalysts could achieve the epoxidation of allyl chloride with equimolar H₂O₂ under solvent-free and mild conditions. Moreover, the catalysts exhibited excellent catalytic performance and reusability. The catalytic mechanism was explored by FT-IR spectroscopy. The results of kinetic experiments show that the chain length of alkanes and heterocyclic structure of cations have a great influence on the catalytic activity of the catalysts.

Full text of DOI:10.1016/j.apcata.2020.117846

Journal Pre-proof
Epoxidation of Allyl Chloride with H O Catalyzed by Three Structurally
2
2
Related Quaternary Ammonium Modified Polyoxophosphotungstates
Xiuxian Zhao (Methodology) (Investigation), Junhua Sun (Data
curation) (Writing - original draft), Guoxin Sun (Conceptualization),
Qi You (Visualization) (Software), Xuchuan Jiang (Writing - review
and editing) (Supervision), Yu Cui (Writing - review and editing)
(Supervision)
PII:
S0926-860X(20)30439-7
DOI:
https://doi.org/10.1016/j.apcata.2020.117846
APCATA 117846
Reference:
To appear in:
Applied Catalysis A, General
Received Date:
Revised Date:
Accepted Date:
5 May 2020
19 September 2020
21 September 2020
Please cite this article as: Zhao X, Sun J, Sun G, You Q, Jiang X, Cui Y, Epoxidation of Allyl
Chloride with H O Catalyzed by Three Structurally Related Quaternary Ammonium Modified
2
2
Polyoxophosphotungstates, Applied Catalysis A, General (2020),
doi: https://doi.org/10.1016/j.apcata.2020.117846

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Epoxidation of Allyl Chloride with H
2
O Catalyzed by Three
2
Structurally Related Quaternary Ammonium Modified
Polyoxophosphotungstates
#
#
Xiuxian Zhao , Junhua Sun , Guoxin Sun, Qi You, Xuchuan Jiang*, Yu Cui*
Affiliation and address of the authors: Institute for Smart Materials & Engineering, School of
Chemistry and Chemical Engineering, University of Jinan, No. 336 Nanxinzhuang West Road,
250022 Jinan, P.R. China
*
Corresponding author: E-mail: ism_jiangxc@ujn.edu.cn (X.C. Jiang), chm_cuiy@ujn.edu.cn
(Y. Cui)
#
Xiuxian Zhao and Junhua Sun contributed equally to this paper.
Graphical Abstract

Highlights





The catalyst of polyoxophosphotungstate was synthesized by green method.
The epoxidation of allyl chloride was achieved under real solvent-free condition.
The catalysts exhibited excellent catalytic performance and reusability.
The catalytic mechanism was explored by FT-IR spectroscopy.
The catalytic activity is related to the structure of cations.
Abstract
The one-step epoxidation of allyl chloride has always been a great challenge for
the industrial production. The key of this technology is to find efficient and friendly
catalyst. In this paper, three structurally related quaternary ammonium modified
polyoxophosphotungstates were synthesized by green and facile method. Among them,
[
C
16
H
33(CH
3
)
3
N]
transfer catalyst (RPTC) and [(C18
phase transfer catalyst (TPTC). All three catalysts could achieve the epoxidation of allyl
chloride with equimolar H under solvent-free and mild conditions. Moreover, the
3
PW
4
O
24 and [π-C
5
H
5
NC16
H
33
]
3
PW
4
O
24 are reaction-controlled phase
H
37
)
2
(CH
3
)
2
N] PW
3
4
O24 is temperature-controlled
2
O
2
catalysts exhibited excellent catalytic performance and reusability. The catalytic
mechanism was explored by FT-IR spectroscopy. The results of kinetic experiments
show that the chain length of alkanes and heterocyclic structure of cations have a great
influence on the catalytic activity of the catalysts.
Keywords
Catalytic activity; Epoxidation; Epichlorohydrin; Phase transfer catalyst;
1
. Introduction

Epoxidation has been the subject of extensive research interest for a long time
because epoxides are often used as starting materials or intermediates in chemical or
pharmaceutical industry.[1] As an important chemical raw material, epichlorohydrin
(ECH) has large demand in the whole world, which is widely used in the preparation of
glycerol, epoxy resin, chlorohydrin rubber and polyether polyols.[2] Up to now,
chlorohydrin method remains dominant in the industrial production. However, the
chlorohydrin method showed inevitable shortcomings such as low yield, high energy
consumption, many by-products, and environmental pollution.[3] Therefore, it is urgent
to develop an eco-friendly and cost-effective method for ECH production.
In recent years, various catalysts have been reported for the epoxidation of olefins
with H
2
2
O such as nano materials,[4-10] metal complex,[11-18] silicates,[19-25]
hydrotalcites[26-29] and polyoxometalates.[30-36] Catalysts play an indispensable role
in epoxidation reaction. The traditional homogeneous and heterogeneous catalysts have
the intrinsic advantages and limitations. Homogeneous catalysts dissolve in reactants
and exhibit high reactivity but have difficulty in separation and reuse. On the contrary,
heterogeneous catalysts are beneficial to facile separation and recycling but always
show poor activity compared with homogeneous counterparts in most catalytic
processes.[37-39] In order to combine the advantages of homogeneous and
heterogeneous catalysts, many efforts have been devoted to develop phase transfer
catalysts.[40-43] The derived reaction-controlled phase transfer catalyst and
temperature-controlled phase transfer catalyst possess the superiorities of both
homogeneous and heterogeneous catalysts, which have been applied to the epoxidation

of olefins.[44-47]
The one-step epoxidation of allyl chloride with environmentally friendly H
2
2
O is
an ideal production route, which could reduce side reactions and improve atomic
utilization. However, a few of catalysts were reported for the epoxidation of allyl
chloride. Venturello group first reported a catalyst based on polyoxophosphotungstate,
[
(C
chloride with H
reported that the titanium silicalite (TS-1) catalyzed the epoxidation of allyl chloride
with H using excess allyl chloride and methanol solvent.[49] Sun group testified
allyl chloride could be epoxidized into ECH catalyzed by [π-C [PW
in toluene and tributylphosphate solution.[50] Jun Li group reported a reversible
supported catalyst (RSC), [C16 PW 16 supported on silanized silica gel,
epoxidizing allyl chloride to ECH with H under excess allyl chloride.[51] All the
8
H
17
)
3
NCH
3
]
3
[PO
4
[W(O)(O
2
)
2
]
4
], which could be used for the epoxidation of allyl
2
O
2
using excess allyl chloride and benzene solvent.[48] Clerici group
2
O
2
5
H
5
NC16
H
33
]
3
4
16
O ]
H
33N(CH
3
)
3
]
3
4
O
2
O
2
reported catalysts achieved the epoxidation of allyl chloride in organic solvents or
excess allyl chloride, which made subsequent separation and purification difficult and
did not meet the requirements of green chemistry. Therefore, it is significant to exploit
a series of catalysts to achieve the epoxidation of allyl chloride with equimolar H
2
2
O in
the absence of any solvent. It can be seen from previous studies that
polyoxophosphotungstate has a very good catalytic potential for epoxidation of allyl
chloride. However, a traditional synthesis method of polyoxophosphotungstate
involved carcinogenic chlorinated solvents, and the synthesized catalyst could not
achieve the desired effect for the epoxidation of allyl chloride. Moreover, the influence

of cation structure on the catalytic activity of polyoxophosphotungstates has not been
reported yet.
In present work, three phase transfer catalysts based on polyoxophosphotungstate
were synthesized by green and facile method. Due to the difference of cations, the three
catalysts showed the properties of reaction-controlled and temperature-controlled phase
transfer catalysts respectively. Three structurally related quaternary ammonium
modified polyoxophosphotungstates showed excellent catalytic performance for the
epoxidation of allyl chloride with equimolar H
2
2
O . First, the catalytic performance of
three catalysts were investigated and compared. Then, the catalytic mechanism was
studied by FT-IR spectroscopy. To further study and compare the catalytic activity of
three catalysts, the turnover frequency and activation energy of the epoxidation reaction
catalyzed by different catalysts were studied.
2
. Experimental
2
.1 Reagents and Characterization
All the chemicals used in this study are as follows: Phosphotungstic acid
(
H
3
PW12
O
40·xH
2
O, ≥ 99.0%, Sinopharm Chemical Reagent Co. Ltd.), hydrogen
30%, Sinopharm Chemical Reagent Co. Ltd.),
hexadecyltrimethylammonium chloride (C16 NCl, 98.0%, Sinopharm
Chemical Reagent Co. Ltd.), hexadecylpyridinium chloride monohydrate [π-
O, 98.0%, Sinopharm Chemical Reagent Co. Ltd.), dimethyl
dioctadecyl ammonium chloride (C18 (CH NCl, 97.0%, Sinopharm Chemical
peroxide
(H
2
O ,
2
H
3 3
33)(CH )
C
5
H
5
NC16
H
33]Cl·H
2
H
37
)
2
)
3 2

Reagent Co. Ltd.), absolute ethanol (CH
3
CH
2
OH, ≥ 99.7%, Sinopharm Chemical
Cl, 97.0%, Sinopharm Chemical
Reagent Co. Ltd.), allyl chloride (CH =CHCH
2
2
Reagent Co. Ltd.), and deionized water was used throughout the experiments. All
chemicals were analytical in grade, commercially available and used without further
purification.
The functional groups of the catalyst were characterized by fourier transform
infrared spectroscopy (FT-IR, VERTEX 70, Bruker, USA) using 2–4% (w/w) KBr
pellets prepared by manual grinding. The catalysts were pretreated by microwave
digestion equipment (MARS6, CEM), and then the content of P and W was measured
by inductively coupled plasma emission spectrometer (iCAP6300, Thermo Fisher
Scientific). The content of C, H, N atoms was measured by elemental analyzer (vario
3
1
EL cube, Elementar). P NMR spectroscopy was detected by Bruker AVANCE
NEO600. The concentration of ECH was analyzed by gas chromatography (GC, GC-
2
030ATF, SHIMADZU, Japan) with a flame-ionization detector and a TM-1701
column (35 m×0.32 mm, film: 0.5 mm). The temperature of injector, detector and oven
o
o
o
was 160 C, 230 C, 100 C, respectively. High purity nitrogen was used as the carrier
gas.
2
.2 Preparation of Catalysts
[
C
16
H33(CH
3
)
3
N]
3
PW
4
O
24: Firstly, phosphotungstic acid 2.88 g (1 mmol) was dissolved
in 20 mL aqueous H
2
O
2
(30%) and stirred at room temperature for 2 h. Secondly, the
suspension of hexadecyltrimethylammonium chloride 1.01 g (3.1 mmol) in 20 mL

o
anhydrous ethanol was heated to 40 C to obtain light yellow solution. Then the oxidic
phosphotungstic acid aqueous solution was added dropwise into the resultant ethanol
o
solution at 40 C, the white precipitate was appeared and the suspended solution was
stirred for another 2.5 h. After the reaction, the white precipitate was filtered and
washed with water (100 mL×2) and anhydrous ethanol (20 mL) respectively. Finally,
o
the white precipitate was dried in vacuum at 30 C for 12 h to obtain white powder 1.76
-1
g. (Yield 72.3%, based on P atoms). FT-IR spectrum (KBr, cm ): ν˜= 1091 (s), 1058
s) (P-O), ν˜= 964 (s) (W=O), ν˜= 845(s) (O-O), ν˜= 773 (w), 721 (m) (C-C) , ν˜=
52 (m) (Figure S1). Elemental analysis: found C 35.01%, N 2.14%, H 6.66%, P 1.27%,
W 34.3%. Calculated for [C16 N] PW 24: C 34.6%, N 2.10%, H 6.34%, P
.55%, W 36.7%.
π-C
using the similar method with [C16
(
6
H33(CH
3
)
3
3
4
O
1
[
5
H
5
NC16
H ]
33
3
PW
4
O24: The catalyst of [π-C
5
H
5
NC16
H ]
33 3
PW
4
O24 was synthesized
H33(CH
3
3
) N]
3
PW O24. The difference is that
4
hexadecylpyridinium chloride dissolved in water was added dropwise into oxidic
o
phosphotungstic acid aqueous solution at 40 C. (Yield 73.6%, based on P atoms). FT-
-1
IR spectrum (KBr, cm ): ν˜= 1091 (s), 1058 (s) (P-O), ν˜= 983 (m) (W=O), ν˜= 846
s) (O-O), ν˜= 773 (w), 721(w) (C-C), ν˜= 685 (m). (Figure S2). Elemental analysis:
found C 37.53%, N 2.09%, H 5.67%, P 1.37%, W 32.9%. Calculated for [π-
(
C
5
H
5
NC16
H
33
]
3
PW
4
O24: C 36.66%, N 2.04%, H 5.57%, P 1.50%, W 35.63%.
[
(C18
H
37
)
2
(CH
3
)
2
N]
3
PW
4
O
24: The catalyst of [(C18
H
37
)
2
(CH
3
4
)
2
N]
3
PW
4
O24 was
synthesized using the similar method with [C16
H33(CH
3
)
3
N]
3
PW
O24. (Yield 73.5%,
-1
based on P atoms). FT-IR spectrum (KBr, cm ): ν˜= 1088 (s), 1058 (s) (P-O), ν˜= 978

(m) (W=O), ν˜= 848 (m) (O-O), ν˜= 789 (w), 719 (w) (C-C) , ν˜= 650 (w) (Figure
S3). Elemental analysis: found C 50.05%, N 1.62%, H 8.99%, P 0.86%, W 22.7%.
Calculated for [(C18
W 26.23%.
H
37
) (CH
2
3
)
2
N]
3
PW O24: C 48.84%, N 1.50%, H 8.63%, P 1.10%,
4
2
.3 Catalytic Reaction
2
.3.1 Catalyst Content
Allyl chloride (6.12 g, 0.08 mol), 30% H
2
2
O (9.07 g, 0.08 mol), different amounts
of catalyst (allyl chloride: catalyst (mol: mol) =1:100, 1:200, 1:300, 1:400, 1:500) were
put into a number of single-neck flasks respectively. The flasks were heated in an oil
o
bath with a reflux condenser and stirred at 45 C for 6.5 h.
2
.3.2 Temperature
Allyl chloride (6.12 g, 0.08 mol), 30% H
2
2
O (9.07 g, 0.08 mol), catalyst
[
C
16
H
33(CH
3
)
3
N]
mixture was prepared in quintuplicate and then reacted at 25 C, 35 C, 45 C, 55 C
respectively. Similarly, catalyst [π-C PW 24 (1.65 g, 0.8 mmol) and
(CH N] PW 24 (1.12 g, 0.4 mmol) were performed the above reaction.
3
PW
4
O24 (1.60 g, 0.8 mmol) were put into single-neck flask. The
o
o
o
o
5
H
5
NC16
H
33
]
3
4
O
[
(C18
H
37
)
2
3
)
2
3
4
O
2
.3.3 Recycling
A single-neck flask was charged with catalyst [C16
H33(CH
3
)
3
N]
3
PW
4
O24 (1.60 g,
0
.8 mmol), 30% H (9.07 g, 0.08 mol) and allyl chloride (6.12 g, 0.08 mol) in a molar
2
O
2
ratio of 1/100/100. The flask was heated in an oil bath with a reflux condenser and
o
stirred at 55 C for 4 h. After the reaction, the mixture was cooled to room temperature
and catalyst was filtered out. Then, the catalyst was washed with ethanol and dried in

vacuum for next use. The recovery percent for one cycle was 92.6%. The catalyst was
recycled for five times and properly replenished in each cycle. Similarly, catalyst [π-
C
5
H
5
NC16
H
33
]
3
PW
.4 mmol) were performed the above reaction.
For all catalytic reactions, the mixture was cooled to room temperature after the
reaction for [C16 N] PW 24 and [π-C PW 24 system. But the
mixture was cooled to 15 C after the reaction for [(C18 (CH N] PW 24 system.
4
O
24 (1.65 g, 0.8 mmol) and [(C18
H
37
)
2
(CH
3
)
2
N]
3
PW
4
O24 (1.12 g,
0
H
33(CH
)
3 3
3
4
O
5
H
5
NC16
H
33
]
3
4
O
o
H
37
)
2
3
)
2
3
4
O
Then catalyst was filtered out. The mixture was allowed to separate into layers and then
the content of ECH in organic phase was analyzed by GC.
2
.4 Kinetic Experiment
To investigate the catalytic activity of three phase transfer catalysts, the following
experiments were carried out for the calculation of turnover frequency (TOF) and
activation energy (E ). Catalyst (1.60 g [C16 N] PW 24), 30% H (9.07 g)
and allyl chloride (6.12 g) in a molar ratio of 1/100/100 were mixed in a two-neck flask,
adding 10mL chloroform as solvent. Similarly, catalyst (1.65 [π-
PW 24), 30% H (9.07 g) and allyl chloride (6.12 g) in a molar ratio
of 1/100/100 were mixed in a single-neck flask, adding 10mL chloroform as solvent.
Catalyst (1.12 g [(C18 (CH N] PW 24), 30% H (9.07 g) and allyl chloride
6.12 g) in a molar ratio of 1/200/200 were mixed in a single-neck flask, adding 10mL
chloroform as solvent. The above three reaction systems were heated in an oil bath with
a
H33(CH
3
)
3
3
4
O
2
O
2
g
C
5
H
5
NC16
H
33
]
3
4
O
2
O
2
H
37
)
2
3
)
2
3
4
O
2
O
2
(
o
o
o
o
o
a reflux condenser and stirred at 25 C, 35 C, 40 C, 45 C, 55 C respectively. The
products were sampled at different time and detected by GC.

The turnover frequency (TOF) were calculated according to equations (1).
푚표푙 표푓 퐸퐶퐻
푇푂퐹 = 2
(1)
×푚표푙 표푓 푊×푡푖푚푒
The concentration changes of ECH with time at different temperature was fitted
by Exponential decay equation (2). The reaction rate equation (3) was obtained by
derivation of equation (2).
−
ꢁ
−ꢁ
(
)
(
)
퐵
+ 퐴2ꢀ 퐵
푦 = 푦 + 퐴 ꢀ
ꢂ
ꢃ
(2)
(3)
0
1
−
ꢁ
−ꢁ
ꢅꢂ
ꢆꢂ
(
)
ꢅꢃ
ꢆꢃ
(
)
퐵
푦′ = ꢄ
ꢀ
퐵
ꢄ
ꢀ
ꢂ
ꢃ
′
푦 is the concentration of ECH. ꢇ is time. 푦 is differential coefficient for 푦. Other
parameters are constants.
Arrhenius equation (4) and kinetic equation (5) are used for calculating activation
energy.[52, 53] Equation (6) is derived from equations (4) and (5).
Arrhenius equation:
ꢉ푎
푘 = 푘 × ꢀ( 푅ꢊ
ꢈ
)
(4)
0
Kinetic equation:
푟 = 푘 × ꢋ × ꢋ
(5)
(6)
ꢅ
ꢆ
퐸푎
ꢌ푛푟 = ꢄ + ln(푘 × ꢋ × ꢋ )
0
ꢅ
ꢆ
ꢍꢎ
푘 is reaction rate constant. ꢏ is activation energy. 푇 is temperature. 푟 is reaction
ꢐ
rate. ꢋ and ꢋ are the concentration of allyl chloride and H
2
2
O respectively.
ꢅ
ꢆ
3
. Results and Discussion
3
.1 Characterization of the fresh catalysts
3
1
The P NMR spectroscopy of three catalysts are shown in Fig. S4 - S6. There is a

peak at 6.69 ppm and a smaller peak at -10.77 ppm in the spectrum of [C16
H
33
(
CH N] PW 24 (Fig. S4), which illustrates the catalyst is not a single component. In
3
)
3
3
4
O
Fig. S5, a broad peak from -15 to 8 ppm could be ascribed to many components with
different P/W ratio. [55] Ten independent peaks in Fig. S6 demonstrates that there are
many active components in [(C18
H
37
)
2
(CH
3
)
2
N]
3
PW O24. The significant difference in
4
the composition of the three catalysts may be attributed to the different forces between
the quaternary ammonium cations and peroxotungstates anions during the reaction. The
result of elemental analysis shows that the W/P ratio of three catalysts are 4.54, 4.35,
4
.44 respectively. Similar values of W/P ratio indicate that the active sites of three
catalysts are similar in number. [56]
3
.2 Catalytic Performance
The catalytic performance of three catalysts for the epoxidation of allyl chloride
was studied separately. First of all, the effect of catalyst content on conversion and
selectivity of allyl chloride was investigated. Allyl chloride was allowed to react with
o
equimolar H
2
O
2
at 45 C for 6.5 h in the presence of different catalysts. The molar ratio
between catalysts and allyl chloride was set as 1:100, 1:150, 1:200, 1:300, 1:400 and
:500 respectively. As shown in Fig. 1A, the conversion of allyl chloride was improved
1
gradually and exceeded 94% with the increase in catalysts ratio from 1:500 to 1:100,
and the selectivity was found higher than 99% (Fig. 1B). Compared with the previous
reported catalysts, the catalysts synthesized in this paper all showed excellent catalytic
performance for the epoxidation of allyl chloride (Table 1). For the catalyst of

[
(C18
H
37
)
2
(CH
3
)
2
N]
3
PW O24, the conversion approached maximum when catalyst ratio
4
increased to 1:200. Therefore, the catalytic content of [(C18
set as 1:200 in the following experiments.
H
37
)
2
(CH
3
)
2
N]
3
PW O24 was
4
Table 1. The epoxidation of allyl chloride with H
2
2
O by different catalysts.
Catalyst
Solvent
Conversion% Selectivity% Yield% Ref.
[
(C
8
H
17
)
3
NCH
3
]
3
[PO
4
[W(O)(O
2
)
2
]
4
]
Benzene
96 a
/
80 a
[48]
[49]
[50]
TS-1
Methanol
98 a
92 a
/
[
π-C
5
H
5
NC16
H
33
]
3
[PW
4
O
16
]
Toluene and tributylphosphate
93.5 b
90.6 a
94.8 c
94.5 c
94.1 c
/
80.5 b
RSC
Excess allyl chloride
94.4 c
＞99 c
＞99 c
＞99 c
/
/
/
/
[51]
[
[
[
C
16
H
33(CH
3
)
3
N]
3
PW
4
O
24
None
None
None
This work
This work
This work
5 5 33 3 4 24
π-C H NC16H ] PW O
37 2 3 2 3 4 24
(C18H ) (CH ) N] PW O
a
The conversion and selectivity are based on H
The conversion and yield are based on EAHQ.
The conversion and selectivity are based on allyl chloride.
2 2
O .
b
c
In the experimental process, it has been found that [C16
PW 24 are reaction-controlled phase transfer catalyst, and
N] PW 24 is temperature-controlled phase transfer catalyst.[57, 58]
H
33(CH
3
)
3
N]
3
PW
4
O24 and
[
π-C
5
H
5
NC16
H
33
]
3
4
O
[
(C18
H
37
)
2
(CH
3
)
2
3
4
O
The reaction-controlled phase transfer catalysts emulsified the two phases during the
reaction and then precipitated out with the end of the reaction. The temperature-
controlled phase transfer catalyst emulsified the two phases during the reaction and
o
dissolved in ECH absolutely above 15 C after the reaction, which precipitated out by

o
cooling to 10 C. In order to observe the state of reaction system more intuitively before
and after the reaction and the formation of emulsification during the reaction, the
corresponding photos were shown in Fig. S7 & S8. This phenomenon demonstrates that
the kind of quaternary ammonium salt cations determines the solubility of the catalysts.
Since the liquid-liquid two-phase reaction takes place at the interface, as a promoter of
the reaction, the catalyst must play a role in the interface. Therefore, the structure of the
catalyst influences the reaction. The prepared catalysts have amphiphilic structure, the
cations with alkyl groups have lipophilicity, and the phosphotungstic acid anions have
hydrophilicity. The surfactant-like structure makes the catalysts aggregate at the
interface, and the increase of lipophilic group chain length can increase the tendency of
aggregation at the interface.[60] Therefore, the catalytic performance of
[
(C18
H
37
)
2
(CH
3
)
2
N]
3
PW O24 is the best among the three and the other two also show
4
good efficiency under the similar condition.
Figure 1. (A) Effect of different catalyst amount on conversion of allyl chloride. (B) Effect of
different catalyst amount on selectivity of allyl chloride. Experimental condition: allyl chloride:
o
H
2
O
2
(mol: mol) = 1:1, 45 C, 6.5 h.
To evaluate the reusability of the catalysts, recycling experiments were carried out
o
as shown in Fig. 2. Allyl chloride reacted with equimolar H
2
O
2
at 45 C for 6.5 h

catalyzed by different catalysts. After five cycles, the conversion of allyl chloride was
no less than 85% and selectivity was still more than 99%, which indicated three
catalysts possessed good catalytic activity and stability. The decrease of conversion rate
may be attributed to the leaching of W after each catalytic run. [45] In order to further
explore the stability of the catalysts, the IR spectra of the catalysts before and after the
reaction were compared. The results showed that the band of v(O-O) band disappeared
and v(W-Oc-W) and v(W-Ob-W) appeared (Fig. S4-Fig. S6), which demonstrated that
the hydrogen peroxide had been consumed completely and the catalysts transferred the
oxygen of themselves to allyl chloride.[52] The other bands did not change obviously,
testifying that the structures of catalysts were relatively stable after the reaction.
Temperature plays an important role on catalytic reaction. Herein, the effect of
temperature on conversion rate and selectivity was investigated keeping the molar ratio
between catalysts and allyl chloride as 1:100, 1:100, 1:200 for
[
C
16
H33(CH
3
)
3
N]
3
PW
4
O
24, [π-C
5
H
5
NC16
H ]
33 3
PW
4
O24 and [(C18
H
37
)
2
(CH
3
2
) N]
3
PW
4
24
O ,
respectively. Allyl chloride reacted with equimolar H
2
O
2
in the presence of catalysts for
o
o
o
o
o
6
.5 h at 25 C, 35 C, 40 C, 45 C, 55 C respectively. The conversion of allyl chloride
in three catalytic systems enhanced with the increase in the temperature and the
o
maximum value was more than 97% at 55 C. What is worth mentioning is that the
selectivity keeps above 99% under different reaction temperature (Fig. 3), which shows
the feasibility of reaction with raising temperature.
Figure 2. (A)The effect of cycle test on conversion of allyl chloride. (B) The effect of cycle test on
selectivity of allyl chloride.

Figure 3. (A) The effect of temperature on conversion of allyl chloride in the presence of different
catalysts. (B) The effect of temperature on selectivity of allyl chloride in the presence of different
catalysts.
3
.3 Catalytic Mechanism
To explore the catalytic mechanism, the catalytic process of the reaction was tracked
by infrared spectroscopy. When the catalyst [C16
H33(CH
3
)
3
N]
3
PW O24 reacted with
4
o
allyl chloride at 55 C for 1min, 5 min, 15 min, respectively, the v(O-O) band at 845
-1
-1
cm disappeared gradually (Fig. 4). At the same time, two new bands at 883 cm and
-1
8
04 cm assigned to v(W-Oc-W) and v(W-Ob-W) appeared respectively, which
indicated that the catalyst transferred the oxygen atom to allyl chloride.[52] Then, the
o
system was treated with 30% H
2
O
2
for additional 1 min, 5 min, 15 min at 55 C. The
-
1
v(O-O) band appeared again and shift to 832 cm , while the band of v(W-Oc-W) and
v(W-Ob-W) disappeared. The phenomenon illustrated active oxygen was transferred
from hydrogen peroxide to catalyst. The slight shift of spectrum may be attributed to
the changes of catalyst structure after adding hydrogen peroxide. The catalyst could
degrade into smaller species after the reaction with hydrogen peroxide.[57] Meanwhile,
the similar results were obtained from the catalytic system of [π-C
5
H
5
NC16
H ]
33 3
PW
4
O
24
and [(C18 (CH N] PW 24 (Fig. S12 and Fig. S13). The results show that the
H
37
)
2
3
)
2
3
4
O

catalysts acted as oxygen carrier during the reaction and obtained the oxygen from
hydrogen peroxide, then transferred the oxygen to allyl chloride. In our previous work,
it has been testified the catalyst exhibited obvious interfacial activity and aggregated at
the interface.[59] Therefore, the catalytic process takes place at the interface of the two
phases, as shown in Scheme 1.
Figure 4. FT-IR spectrum of the catalyst [C16
H
33(CH
)
3 3
3 4
N] PW O24 under reaction condition (a)
o
fresh catalyst (b) catalyst treated with allyl chloride for 1 min at 55 C (c) catalyst treated with allyl
o
o
chloride for 5 min at 55 C (d) catalyst treated with allyl chloride for 15 min at 55 C (e) d system
o
treated with 30% H
2
O
2
for additional 1 min at 55 C (f) d system treated with 30% H
2
O for
2
o
o
additional 10 min at 55 C (g) d system treated with 30% H
2
O for additional 25 min at 55 C.
2

Scheme 1. The catalytic process of catalysts at two-phase interface.
3
.4 Kinetic Study
Turnover frequency (TOF) is a common parameter to evaluate the catalytic activity.
o
[
61] The reaction could reach to equilibrium in three hours at 55 C. Therefore, the
o
turnover frequency of three catalysts was calculated under 55 C (Fig. 6). As the
reactant concentration decreased with the progress of the reaction, the contacting
probability between the reactant and catalyst decreased，so the TOF value on the whole
showed a downward trend. For [C16
H33(CH
3
3
) N]
3
PW O24, the TOF value first
4
decreased with time and then showed a small recovery and then fell. The brief rebound
of 80-120 minutes may attribute to a better emulsion state of the reactant. For [π-
C
5
H
5
NC16
H
33
]
3
PW
4
O24, the TOF value went down to almost the same value as
-1
O
24, TOF= 4.46 h-
[
C
16
H
33(CH
3
)
3
N] PW
3
4
O
24 (TOF= 4.37 h for [C16
PW 24), which illustrated the similar catalytic activity. For
PW 24, there was a slow decline in TOF value and it still kept a
H
33(CH
3
)
3
N]
3
PW
4
1
for [π-C
5
H
5
NC16
H
33
]
3
4
O
[
(C18
H
37
)
2
(CH
3
)
2
N]
3
4
O

-1
high value when the reaction reached equilibrium (TOF= 9.29 h ), which showed that
the catalytic activity of [(C18 (CH N] PW 24 is much higher than that of the
other two. The order of catalytic activity is [(C18 (CH N] PW
N] PW 24≈[π-C PW
The catalytic activity of catalyst in heterogeneous reaction is not only related to
H
37
)
2
3
)
2
3
4
O
H
37
)
2
3
)
2
3
4
O ＞
24
[
C
16
H33(CH
3
)
3
3
4
O
5
H
5
NC16
H ]
33 3
4
24
O .
the activation energy but also to the interfacial properties. In order to further explore
the relationship between catalytic activity and catalyst structure, the reaction activation
energy of allyl chloride catalyzed by different catalysts was studied. First of all, the
concentration changes of generated ECH with time was explored at different
temperatures. As shown in Fig. 5, allyl chloride reacted with equimolar H
O
2 2
catalyzed
o
o
o
o
o
by [C16
H33(CH
3
)
3
N]
3
PW O24 at 25 C, 35 C, 40 C, 45 C and 55 C respectively. The
4
concentration of ECH increased gradually and reached to maximum value during the
reaction time at different temperatures. With the temperature increased, the equilibrium
time for the reaction gradually decreased. The experimental data were fitted with
equation (2) to further explore the effect of temperature on the reaction rate. Relevant
fitting parameters were shown in Table S1. The initial reaction rates at different
temperature were calculated by equation (3), and there was good linear relationship
between reaction rate and temperature. The calculated activation energy of allyl
chloride in catalyst [C16
experiments were
(CH N] PW
and 68.90 kJ/mol respectively (Fig. S9-Fig. S10). The order of activation energy values
H
33(CH
3
)
3
N]
3
PW
out
O24 catalytic system. The activation energy was 62.58 kJ/mol
4
O
24 system was 64.05 kJ/mol. The similar
carried
in [π-C PW and
5
H
5
NC16
H ]
33 3
4
O
24
[
(C18
H
37
)
2
3
)
2
3
4

is
C
[(C18
H
37
)
2
(CH
3
)
2
N]
3
PW
4
O
24
＞
[C16
H
33(CH
3
)
3
N]
3
PW
4
O
24
＞
[π-
5
H
5
NC16
H
33
]
3
PW
demonstrate
(CH N] PW
4
O
24. Considering the catalytic activity, the results of activation
energy
that
the
order
of
PW
interfacial
activity
PW
is
[
(C18
H
37
)
2
3
)
2
3
4
O
24＞[C16
H33(CH
3
)
3
N]
3
4
O
24＞[π-C
5
H
5
NC16
H
33
]
3
4
24
O .
The interface aggregation of catalyst can promote the interface reaction, that is, the
mass transfer between hydrogen peroxide and catalyst, and then affect the whole
reaction rate.
There is a significant correlation between catalytic activity and interfacial activity.
[
62] During the reaction in this study, as an oxygen carrier, the interface location of
polyoxophosphotungstic acid anions directly determines the interfacial activity of the
catalysts, while the interface position of anions is closely related to the structure of
lipophilic cations. The above results prove that the chain length of alkanes and
heterocyclic structure in quaternary ammonium cations have a great influence on the
catalytic activity of such catalysts. The results also provide a new idea for the
subsequent study and industrial application of this kind of catalysts.
Figure 5. (A) The concentration changes of ECH over time catalyzed by [C16
H
33(CH
3
)
3
N]
3
4
PW O
24

at different temperatures. (B) The relationship between reaction rate and temperature. Experimental
condition: catalyst: allyl chloride: H (mol: mol: mol) =1:100:100.
2
O
2
o
Figure 6. The changes of turnover frequency with time of three catalysts under 55 C.
4
. Conclusions
In summary, three structure related quaternary ammonium modified
polyoxophosphotungstates, [C16
H33(CH
3
)
3
N]
3
PW
4
O
24, [π-C
5
H
5
NC16
H
33
]
3
PW
4
O24 and
[
(C18
H
37
)
2
(CH N] PW 24, were synthesized by a simple way. These catalysts
3
)
2
3
4
O
present excellent catalytic performances for the epoxidation of allyl chloride because
they combine the advantages of both homogeneous and heterogeneous catalysis. The
experimental results indicate the maximum conversion rate of allyl chloride is more
than 97% and selectivity is higher than 99%. Moreover, three catalysts are easily
recycled for several times without significant loss of activity. The results of kinetic
experiments show the catalytic activity of the catalysts is related to the chain length of
alkanes and heterocyclic structure in quaternary ammonium cations. This study lays a
foundation for further study of the influence of cations in phase transfer catalysts on
catalytic activity and has a strong industrial application value.
Credit Author Statement

Xiuxian Zhao: Methodology, Investigation
Junhua Sun: Data curation, Writing- Original draft preparation
Guoxin Sun: Conceptualization
Qi You: Visualization, Software
Xuchuan Jiang: Writing- Reviewing and Editing, Supervision
Yu Cui: Writing- Reviewing and Editing, Supervision
Acknowledgements
This work was supported by the National Natural Science Foundation of China
(No 21876062); and the Natural Science Foundation of Shandong Province (No
ZR2017LB005).

Reference
[
1]
E. A. Mikhalyova, O. V. Makhlynets, T. D. Palluccio, A. S. Filatov, E. V. Rybak-Akimova,
Chemical Communications 2012, 48, 687-689.
[
2]
A. M. Krzyꢀanowska, E. Milchert, W. M. Paꢁdzioch, Industrial & Engineering Chemistry
Research 2013, 52, 10890-10895.
[
[
[
[
3]
4]
5]
6]
W. Zhongxun, Qilu Petrochemical Technology 2007, 4.
J. Huang, Y. Wang, Z. Hao, X. Peng, Journal of Saudi Chemical Society 2017, 21, 811-816.
A. Blanckenberg, R. Malgas-Enus, Catalysis Reviews 2019, 61, 27-83.
M. Zhang, V. Singh, X. Hu, X. Ma, J. Lu, C. Zhang, J. Wang, J. Niu, ACS Catalysis 2019, 9,
7
641-7650.
[
[
7]
8]
U. Jameel, M. Zhu, X. Chen, Z. Tong, Current Organic Chemistry 2017, 21, 2585-2596.
S. Ghiami, M. A. Nasseri, A. Allahresani, M. Kazemnejadi, Reaction Kinetics, Mechanisms and
Catalysis 2019, 126, 383-398.
[
[
[
[
9]
S. Akbarpour, A. Bezaatpour, E. Askarizadeh, M. Amiri, Applied Organometallic Chemistry
2
017, 31, e3804.
A. Rezaeifard, M. Jafarpour, R. Haddad, F. Feizpour, Catalysis Communications 2017, 95, 88-
1.
10]
11]
12]
9
X. Engelmann, D. D. Malik, T. Corona, K. Warm, E. R. Farquhar, M. Swart, W. Nam, K. Ray,
Angewandte Chemie 2019, 131, 4052-4056.
H. M. Hassan, M. A. Betiha, E. El-Sharkawy, R. F. Elshaarawy, N. El-Assy, A. A. Essawy, A.
Tolba, A. M. Rabie, Colloids and Surfaces A: Physicochemical and Engineering Aspects 2020,
1
24520.
[
[
13]
14]
J. Du, C. Miao, C. Xia, Y.-M. Lee, W. Nam, W. Sun, ACS Catalysis 2018, 8, 4528-4538.
X. Song, D. Hu, X. Yang, H. Zhang, W. Zhang, J. Li, M. Jia, J. Yu, ACS Sustainable Chemistry
&
Engineering 2019, 7, 3624-3631.
[
[
15]
16]
N. Maksimchuk, J. S. Lee, A. Ayupov, J.-S. Chang, O. Kholdeeva, Catalysts 2019, 9, 324.
G. Tseberlidis, L. Demonti, V. Pirovano, M. Scavini, S. Cappelli, S. Rizzato, R. Vicente, A.
Caselli, ChemCatChem 2019, 11, 4907-4915.
[
[
[
17]
18]
19]
W. Wang, Q. Sun, D. Xu, C. Xia, W. Sun, ChemCatChem 2017, 9, 420-424.
R. Egekenze, Y. Gultneh, R. Butcher, Polyhedron 2018, 144, 198-209.
O. A. Kholdeeva, I. D. Ivanchikova, N. V. Maksimchuk, I. Y. Skobelev, Catalysis Today 2019,
3
33, 63-70.
[
[
[
[
20]
21]
22]
23]
N. Maksimchuk, I. Ivanchikova, O. Zalomaeva, Y. Chesalov, A. Shmakov, V. Zaikovskii, O.
Kholdeeva, Catalysts 2018, 8, 95.
Y. Yu, Z. Tang, J. Wang, R. Wang, Z. Chen, H. Liu, K. Shen, X. Huang, Y. Liu, M. He, Journal
of Catalysis 2020, 381, 96-107.
D. T. Bregante, D. W. Flaherty, Journal of the American Chemical Society 2017, 139, 6888-
6
898.
A. Solé-Daura, T. Zhang, H. Fouilloux, C. Robert, C. M. Thomas, L.-M. Chamoreau, J. J. Carbó,
A. Proust, G. Guillemot, J. M. Poblet, ACS Catalysis 2020.
[
[
24]
25]
G. Wang, Y. Li, Q. Zhu, G. Li, C. Zhang, H. Guo, Catalysts 2020, 10, 15.
I. D. Ivanchikova, I. Y. Skobelev, N. V. Maksimchuk, E. A. Paukshtis, M. V. Shashkov, O. A.
Kholdeeva, Journal of Catalysis 2017, 356, 85-99.

[
[
[
26]
27]
28]
D. L. Hoyos-Castaño, E. Alarcón, A. L. Villa, Catalysis Letters 2019, 149, 1611-1620.
L. T. K. Huyen, N. T. Dat, N. T. Thao, Vietnam Journal of Chemistry 2018, 56, 203-207.
D. Cosano, D. Esquivel, F. J. Romero-Salguero, C. s. Jimꢂnez-Sanchidriꢃn, J. R. Ruiz, ACS
Omega 2019.
[
[
29]
30]
N. T. Thao, A. Köckritz, Catalysis Letters 2019, 149, 3370-3383.
W. Zhao, Y. Ding, Z. Zhang, B. Ma, W. Qiu, Reaction Kinetics, Mechanisms and Catalysis 2011,
1
02, 93-102.
[
[
31]
32]
S. Zhang, S. Gao, Z. Xi, J. Xu, Catalysis communications 2007, 8, 531-534.
X. Ma, P. He, B. Xu, J. Lu, R. Wan, H. Wu, Y. Wang, P. Ma, J. Niu, J. Wang, Dalton Transactions
2
019, 48, 12956-12963.
O. A. Kholdeeva, in Frontiers of Green Catalytic Selective Oxidations, Springer, 2019, pp. 61-
1.
[
33]
9
[
[
34]
35]
H. Taghiyar, B. Yadollahi, Polyhedron 2018, 156, 98-104.
N. V. Maksimchuk, G. M. Maksimov, V. Y. Evtushok, I. D. Ivanchikova, Y. A. Chesalov, R. I.
Maksimovskaya, O. A. Kholdeeva, A. Solꢂ-Daura, J. M. Poblet, J. J. Carbꢄ, ACS Catalysis 2018,
8
, 9722-9737.
[
[
[
36]
37]
38]
Z. Shi, C. Mei, G. Niu, Q. Han, Journal of Coordination Chemistry 2018, 71, 1460-1468.
Z. Yu, Z. Guo, H. Wei, W. Qian, J. Wang, Cheminform 2015, 5, 4324.
C. Vartzouma, E. Evaggellou, Y. Sanakis, N. Hadjiliadis, M. Louloudi, Journal of Molecular
Catalysis A Chemical 2007, 263, 77-85.
[
[
39]
40]
C. I. Fernandes, N. U. Silva, P. D. Vaz, T. G. Nunes, C. D. Nunes, Applied Catalysis A: General
2
010, 384, 84-93.
J. Li, W. Xu, F. Zhang, Y. Zhong, W. Zhu, Research on Chemical Intermediates 2014, 40, 1867-
877.
1
[
[
41]
42]
J. Zhang, M. Zhang, K. Tang, F. Verpoort, T. Sun, Small 2014, 10, 32-46.
L. Xu, B.-G. Li, S. Jie, Z. Li, Z. Bu, Industrial & Engineering Chemistry Research 2019, 58,
1
3085-13092.
[
43]
K. F. Chin, X. Ye, Y. Li, R. Lee, A. M. Kabylda, D. Leow, X. Zhang, E. C. X. Ang, C.-H. Tan,
ACS Catalysis 2020, 10, 2684-2691.
[
[
[
44]
45]
46]
Z. Xi., N. Zhou, Y. Sun, K. Li, Science 2001, 292, 1139-1141.
Y. Ding, W. Zhao, H. Hua, B. Ma, Green Chemistry 2008, 10, 910-913.
H. Chen, W.-L. Dai, X.-L. Yang, R. Gao, Y. Cao, H. Li, K. Fan, Applied Catalysis A: General
2
006, 309, 62-69.
[
[
[
[
[
47]
48]
49]
50]
51]
W. Zhao, B. Ma, H. Hua, Y. Zhang, Y. Ding, Catalysis Communications 2008, 9, 2455-2459.
C. Venturello, E. Alneri, M. Ricci, The Journal of Organic Chemistry 1983, 48, 3831-3833.
M. G. Clerici, P. Ingallina, Journal of Catalysis 1993, 140, 71-83.
Y. Sun, Z. Xi, G. Cao, Journal of Molecular Catalysis A: Chemical 2001, 166, 219-224.
J. Li, G. Zhao, S. Gao, Y. Lv, J. Li, Z. Xi, Organic process research & development 2006, 10,
8
76-880.
[
[
[
52]
53]
54]
C. Venturello, R. D'Aloisio, The Journal of Organic Chemistry 1988, 53, 1553-1557.
K. J. Laidler, Journal of Chemical Education 1984, 61, 494.
Y. Chen, J. Zhuang, X Liu, J. Gao, X, Han, X. Bao, N. Zhou, S. Gao, Z. Xi, Catalysis Letters
2
004, 93, 41-46.
[
55]
M. Peleg, M. D. Normand, M. G. Corradini, Critical reviews in food science and nutrition 2012,

5
2, 830-851.
[
[
56]
57]
Z. Ma, W. Wang, Y. Wu, Y. He, T. Wu, A. C. Marr, Plos One, 2014, 9, 100743.
J. Gao, Y. Chen, B. Han, Z. Feng, C. Li, N. Zhou, S. Gao, Z. Xi, Journal of Molecular Catalysis
A: Chemical 2004, 210, 197-204.
[
[
[
58]
59]
60]
Y. Ding, B. Ma, D. Tong, H. Hua, W. Zhao, Australian journal of chemistry 2009, 62, 739-746.
M. J. Rosen, J. T. Kunjappu, Surfactants and interfacial phenomena, John Wiley & Sons, 2012.
J. Sun, X. Zhao, G. Sun, S. Zeb, Y. Cui, Q. You, Chemical Engineering Journal, 2020, 398,
1
25051.
[
[
61]
62]
W. F. Monteiro, M. O. Vieira, E. F. Laschuk, P. R. Livotto, S. M.O. Einloft, M. O. de Souzac,
R. A. Ligabue, Journal of CO2 Utilization 2020, 37, 20-28.
D. Mason, S. Magdassi, Y. Sasson, The Journal of Organic Chemistry 1990, 55, 2714-2717.