Facile synthesis of hypercrosslinked resin via photochlorination of p-xylene and succedent alkylation polymerization

Article abstract of DOI:10.1016/j.cclet.2011.03.011

A combination of photochlorination of p-xylene and succedent Friedel-Crafts alkylation polymerization was firstly used in the preparation of the hypercrosslinked adsorptive resin. The data of GC-MS and GC showed that a series of chlorizates were produced when p-xylene was photochlorinated. Hypercrosslinked resins could be synthesized by copolymerization, self-polymerization of chlorizates or post crosslinking reaction. The chemical structure and micromorphology of the porous resins were characterized by BET, FT-IR, SEM and elementary analysis (EA). The results showed that the novel adsorptive resins possess high BET surface near to 1038 m²/g and large pore volumes range from 0.5 to 1.2 cm³/g.

Full text of DOI:10.1016/j.cclet.2011.03.011

Available online at www.sciencedirect.com
Chinese Chemical Letters 22 (2011) 1115–1118
www.elsevier.com/locate/cclet
Facile synthesis of hypercrosslinked resin via photochlorination
of p-xylene and succedent alkylation polymerization
*
Ling Ling Bai, Yong Hao Zhou, Xiu Li Wang, Si Guo Yuan , Xian Li Wu
School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou 450001, China
Received 10 December 2010
Abstract
A combination of photochlorination of p-xylene and succedent Friedel–Crafts alkylation polymerization was firstly used in the
preparation of the hypercrosslinked adsorptive resin. The data of GC–MS and GC showed that a series of chlorizates were produced
when p-xylene was photochlorinated. Hypercrosslinked resins could be synthesized by copolymerization, self-polymerization of
chlorizates or post crosslinking reaction. The chemical structure and micromorphology of the porous resins were characterized by
BET, FT-IR, SEM and elementary analysis (EA). The results showed that the novel adsorptive resins possess high BET surface near
2
3
to 1038 m /g and large pore volumes range from 0.5 to 1.2 cm /g.
2011 Si Guo Yuan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
#
Keywords: Hypercrosslinked resin; Synthesis; p-Xylene; Photochlorination; Polymerization
As a kind of novel porous adsorptive materials, hypercrosslinked polystyrene resin possesses high specific surface
area, narrow pore size distribution, as well as excellent swelling characteristics in various solvent systems [1]. Since
1
CH storage [2–6].
980 it has been widely applied in the fields of selective separation, heterogeneous catalysis, ion exchange, and H or
2
4
However, the hypercrosslinked resin still presents some shortages in its synthetic strategies and matrix variety, such
as humdrum polymeric matrices (usually ST-DVB matrix) and complex synthetic processes. To the best of our
knowledge, Davankov [1], Wood [6], Zeng [7] and our research group [8–10] have expanded the synthetic strategies
and matrix type of hypercrosslinked resin since 2002, which included the Friedel–Crafts alkylation self-
polymerization of dichloromethyl aryl monomer, Friedel–Crafts alkylation co-polymerization with various aryl
molecules, as well as the phenolic condensation of hydroxybenzene with formaldehyde, etc.
In this paper, we adopted a new route to synthesize the hypercrosslinked resins with cheap chemical raw
materials such as p-xylene and Cl , including photochlorination of p-xylene and successively Friedel–Crafts
2
alkylation polymerization. The chemical and porous structures of the novel resins, as well as the components of
the chloride products, were characterized or monitored by BET, FT-IR, SEM, EA, GC–MS and GC,
respectively.
*
Corresponding author.
E-mail address: yuansiguo2005@yahoo.com.cn (S.G. Yuan).
1001-8417/$ – see front matter # 2011 Si Guo Yuan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
doi:10.1016/j.cclet.2011.03.011

1116
L.L. Bai et al. / Chinese Chemical Letters 22 (2011) 1115–1118
1
. Experimental
Gas phase photochlorination (GPPC): p-Xylene (0.52 mol) was added to a three neck flask with a jacket reactor,
and the reaction was initiated by fluorescent lamp near the jacket reactor. During the photochlorination, the reaction
medium in the flask was evaporated and reacted with the chlorine gas in the jacket reactor. The chlorinated p-xylene
fell into the flask because of their higher boiling points than that of the reactant. The photochlorination conditions were
as follows: the temperature in the jacket reactor was controlled at 138 8C by transparent heatcycling oil bath; the liquid
temperature in the flask was gradually raised from 138 8C to 205 8C; the flow rate of Cl was 20 mL/min; the reaction
2
time was 11.5 h. After photochlorination, the chlorizates (86.89 g) were obtained.
The synthesis of the hypercrosslinked resins could be mainly classified into three approaches: (1) copolymerization
of chlorizates with benzene; (2) self-polymerization of chlorizates; (3) further postcrosslinking of the resin obtained
from approach 1.
Copolymerization reaction: The GPPC chlorizates (1.6993 g) and benzene (0.2373 g) were added to 1,2-
dichloroethane solution (10 mL) containing anhydrous FeCl (0.1399 g) and dissolved by ultrasonic means. The
3
polymerization was carried through at 60 8C for 5 h and then 80 8C for 6 h, and the resulted brown resin was washed
with HCl (aq.), extracted with acetone in a Soxhlet apparatus and dried at 80 8C under vacuum, respectively. The resin
2
(1.1533 g, BET surface: 810.05 m /g) was obtained.
1
Self-polymerization reaction: The GPPC chlorizates (1.7160 g) were added to a solution of FeCl (0.1437 g) in
3
anhydrous 1,2-dichloroethane (10 mL), and dissolved by ultrasonic means. The polymerization was carried through at
0 8C for 5 h and then 80 8C for 6 h, and the resulted resin was washed with HCl (aq.), extracted with acetone in a
Soxhlet apparatus and dried at 80 8C under vacuum, respectively. The resin 2 was obtained (0.8687 g, BET surface:
6
2
6
28.1 m /g).
Post crosslinking reaction: The resin 1 (0.5620 g) was added to 1,2-dichloroethane solution (10 mL) containing
FeCl (0.0315 g), and swelled at ambient temperature for 5 h. The post crosslinking reaction was carried through at
3
8
0 8C for 17 h, and the resulted resin was filtered and then washed with HCl (aq.), extracted with acetone in a Soxhlet
apparatus and dried at 80 8C under vacuum, respectively. The resulted P-resin 1 was obtained (0.5342 g, BET surface:
2
037.6 m /g).
1
2
. Results and discussion
The photochlorination of alkyl aromatic hydrocarbon is a kind of continuous competitive reaction. Chlorination
degree and isomer species would increase along with the increase of the photochlorination time, the components of the
chlorizates were determined via GC–MS as shown in Fig. 1 and the proportion of each product was monitored by GC.
The final contents of the GPPC chlorizates were as follows: a-chloro-p-xylene: 16.24%; a,a-dichloro-p-xylene: 7.5%;
0
0
0
a,a -dichloro-p-xylene: 47.25%; a,a,a ,a -tetrachloro-p-xylene: 20.59%.
In our investigation, the GPPC chlorizates could be used in the synthesis of hypercrosslinked resin in the
subsequent polymerization, various chloromethyl aromatic compounds could participate in the construction of
hypercrosslinked matrix and the further investigation for the photochlorination is in progress.
Our earlier investigation has demonstrated that the porous adsorptive resin could be obtained via the
0
copolymerization of 1,4-dichlomethyl benzene (XDC) or 4,4 -dichlomethyl diphenyl (CMB) with benzene or
diphenyl [8]. Being different to the pore formation mechanism of traditional hypercrosslinked resin, the novel porous
resins were synthesized in a homogeneous solution system, and went through initial oligomerization and subsequent
phase separation process during the formation of crosslinked network and pore structure. The preliminary results in
this paper further indicated that the mixed chloride species could be used in the preparation of porous resin, and the
[(Fig._1)TD$FIG]
Fig. 1. GC–MS of the main components of GPPC chlorination intermediate.

L.L. Bai et al. / Chinese Chemical Letters 22 (2011) 1115–1118
1117
Table 1
The results of BET surface and elementary analysis.
a
Property
Resin 1
P-Resin 1
Resin 2
XDC-BE
2
SSA (m /g) (BET)
810.05
1.6550
0.6700
87.235
5.8750
2.9350
0.0870
0.0880
0.0006
1037.6
2.1270
1.1030
87.535
5.9100
–
628.10
1.8250
0.5730
73.885
5.1050
–
974.88
3.3860
1.6510
92.280
6.5270
–
Average pore radius (nm)
3
Total pore volume (cm /g)
EA (C%)
EA (H%)
EA (O%)
3
Micropore volume (r < 2 nm, cm /g) (BJH)
3
Mesopore volume (r: 2–50 nm, cm /g) (BJH)
3
Macropore volume (r > 50 nm, cm /g) (BJH)
0.2610
0.1830
0.0000
0.0940
0.1130
0.0014
–
–
–
a
The resin obtained by copolymerization reaction of XDC (C.P. reagent) and benzene.
resulted resins possessed the fundamental characteristics of hypercrosslinked adsorptive resin. For example, the BET
surface of self-polymerization resin and copolymerization resin from above gas phase photochlorination products
2
2
3
could attain to 628.10 m /g and 810.05 m /g, the pore volume was 0.5–1.2 cm /g (Table 1). We propose that the high
BET surface and abundant micropore (or mesopore) structure mainly derived from the crosslinking network between
phenyl rings. And the large pore volume, on the other hand, arose from the stacking of oligomers and microsphere
particles which were produced during the polymerization.
The content of C and H would increase with the polymerization progressing in our investigation, and theoretically
the content of C and H would attain 100% when the polymerization was complete. In our previous work, the total
content of C and H could attain 98.807% in the resin from XDC (C.P. reagent) and benzene. However, because of
variety of the chlorizates and formation of C O in polymerization, the total content of C and H of the titled resins was
ꢀ
1
usually lower than the resin from XDC (C.P. reagent) and benzene, and the IR peaks at 1264 and 1712 cm (Fig. 3), as
well as the energy spectrum analysis (EDA) results (Fig. 2), also implied that the presence of the C–Cl and C O bond
in the resin matrix (Fig. 3). The literature [11] also reported the oxidation of chloromethyl group during the preparation
of hypercrosslinked resin. The results could be attributed to the presence of multi-chloride isomer (e.g. Cl C–C H –
2
6 4
CH Cl, Cl HC–C H –CHCl ) of chloride mixture and formation of carbonyl group during the alkylation
2
2
6
4
2
polymerization.
To improve the porous structure of polymer matrix, a post crosslinking process was adopted. The experimental
2
2
results showed that the BET surface of resin 1 increased to 1037.6 m /g from the original 810.05 m /g, the total
content of C and H increased from 93.110% to 93.445%. The crosslinking density and pore structure are one of the
most important factors in the adsorption, separation and catalysis of various small molecules. The application of these
novel porous resins is in progress.
[(Fig._2)TD$FIG]
Fig. 2. The energy spectrum analysis (EDA) with SEM for the resin 1.

[(Fig._3)TD$FIG]
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L.L. Bai et al. / Chinese Chemical Letters 22 (2011) 1115–1118
Fig. 3. FT-IR spectra of the hypercrosslinked polymeric resin 1.
In summary, p-xylene and chlorine gas were firstly used in the synthesis of novel hypercrosslinked adsorptive resin
by photochlorination and succedent alkylation polymerization. These novel porous resins obtained from simple
2
3
compounds possessed high specific surface areas (near to 1038 m /g), large pore volumes (0.5–1.2 cm /g) and narrow
pore size distributions (mainly in the range of micropores and small mesopores).
Acknowledgment
The authors are grateful for the support of the National Natural Science Foundation of China (Nos. 20574063 and
1004055).
2
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