Selective preparation of 4,4′-dichlorodiphenylmethane over zeolite K-L catalyst using sulfuryl chloride

Article abstract of DOI:10.1016/S1381-1169(02)00020-1

The liquid phase chlorination of diphenylmethane (DPM) to 4,4′-dichlorodiphenylmethane (4,4′-DCDPM) is investigated at 333 K, under atmospheric pressure over a number of zeolite catalysts using sulfuryl chloride (SO₂Cl₂) as the chlorinating agent. The results obtained are compared with those over the conventional Lewis acid catalyst, AlCl₃ as well as without any catalyst. Zeolite K-L is found to be highly active and selective catalyst for the conversion of DPM to 4,4′-DCDPM. The conversion of DPM, rate of DPM conversion and the selectivity (4,4′-DCDPM/2,4′-DCDPM isomer ratio) over zeolite K-L after 1 h of reaction time are found to be 96.8 wt.%, 19.1 mmol g^-1 h^-1 and 7.4, respectively. The influence of solvent, catalyst concentration, reaction temperature, DPM/SO₂Cl₂ molar ratio, recycle of zeolite K-L, etc. are also examined. 1,2-Dichloroethane is the best solvent and gives the highest selectivity for 4,4′-DCDPM (4,4′-DCDPM/2,4′-DCDPM isomer ratio = 9.7) with zeolite K-L at 353 K after 1 h of reaction time. The formation of 4,4′-DCDPM is favoured by increase in catalyst concentration, reaction temperature and higher concentration of SO₂Cl₂ (lower DPM/SO₂Cl₂ molar ratio). In all these cases, the yield of 4,4′-DCDPM increases with a decrease in the yield of 4-CDPM which suggests that the formation of 4,4′-DCDPM takes place by the consecutive reaction of 4-CDPM. Higher SiO₂/Al₂O₃ ratio (obtained by HCl treatment) of zeolite K-L decreases the conversion of DPM. A noticeable decrease in the activity and selectivity of zeolite K-L is observed on recycling, probably due to reduced crystallinity as well as extraction of small amounts of Al⁺³ and K⁺ ions by the HCl, generated in the reaction. Mechanistically, SO₂Cl₂ is first decomposed into SO₂ and Cl₂ the latter being polarized by the zeolite catalyst to an electrophile (Cl⁺) which then attacks the DPM and subsequently produce the monochlorodiphenylmethane (MCDPM). The MCDPM further is attacked by the electrophile (Cl⁺) and result in the formation of DCDPM.

Full text of DOI:10.1016/S1381-1169(02)00020-1

Journal of Molecular Catalysis A: Chemical 184 (2002) 399–411
Selective preparation of 4,4ꢀ-dichlorodiphenylmethane over
zeolite K-L catalyst using sulfuryl chloride
S.M. Kale, A.P. Singh∗
Catalysis Division, National Chemical Laboratory, Pune 411 008, India
Received 15 August 2001; accepted 3 January 2002
Abstract
The liquid phase chlorination of diphenylmethane (DPM) to 4,4ꢀ-dichlorodiphenylmethane (4,4ꢀ-DCDPM) is investigated
at 333 K, under atmospheric pressure over a number of zeolite catalysts using sulfuryl chloride (SO2Cl2) as the chlorinating
agent. The results obtained are compared with those over the conventional Lewis acid catalyst, AlCl3 as well as without any
catalyst. Zeolite K-L is found to be highly active and selective catalyst for the conversion of DPM to 4,4ꢀ-DCDPM. The con-
version of DPM, rate of DPM conversion and the selectivity (4,4ꢀ-DCDPM/2,4ꢀ-DCDPM isomer ratio) over zeolite K-L after
1 h of reaction time are found to be 96.8 wt.%, 19.1 mmol g−1 h−1 and 7.4, respectively. The influence of solvent, catalyst con-
centration, reaction temperature, DPM/SO2Cl2 molar ratio, recycle of zeolite K-L, etc. are also examined. 1,2-Dichloroethane
is the best solvent and gives the highest selectivity for 4,4ꢀ-DCDPM (4,4ꢀ-DCDPM/2,4ꢀ-DCDPM isomer ratio = 9.7) with
zeolite K-L at 353 K after 1 h of reaction time. The formation of 4,4ꢀ-DCDPM is favoured by increase in catalyst concen-
tration, reaction temperature and higher concentration of SO2Cl2 (lower DPM/SO2Cl2 molar ratio). In all these cases, the
yield of 4,4ꢀ-DCDPM increases with a decrease in the yield of 4-CDPM which suggests that the formation of 4,4ꢀ-DCDPM
takes place by the consecutive reaction of 4-CDPM. Higher SiO2/Al2O3 ratio (obtained by HCl treatment) of zeolite K-L
decreases the conversion of DPM. A noticeable decrease in the activity and selectivity of zeolite K-L is observed on recycling,
probably due to reduced crystallinity as well as extraction of small amounts of Al+3 and K+ ions by the HCl, generated in
the reaction. Mechanistically, SO2Cl2 is first decomposed into SO2 and Cl2 the latter being polarized by the zeolite catalyst
to an electrophile (Cl+) which then attacks the DPM and subsequently produce the monochlorodiphenylmethane (MCDPM).
The MCDPM further is attacked by the electrophile (Cl+) and result in the formation of DCDPM. © 2002 Elsevier Science
B.V. All rights reserved.
Keywords: 4,4ꢀ-Dichlorodiphenylmethane; Diphenylmethane chlorination; Zeolite K-L
1. Introduction
resin [1]. Traditionally, it is known that, on chlori-
nating diphenylmethane (DPM) with molecular
chlorine, methylene group chlorinated compounds are
formed. When DPM is chlorinated in the presence of
azobisisobutyronitrile in CCl4 solvent, then 66–67%
␣-chlorodiphenylmethane and 32–33% ␣,␣-dichloro-
diphenylmethane (␣,␣-DCDPM) are obtained [2].
DPM in the presence of PCl5 with chloride gas gives
only the side-chain chlorinated product [3]. Further-
Ring chlorinated dichlorodiphenylmethane (DCD-
PM) is useful in the preparation of agricultural and
pharmaceutical chemicals or as a plasticizer for vinyl
∗
Corresponding author. Tel.: +91-21-2331453;
fax: +91-20-5893761.
E-mail address: apsingh@cata.ncl.res.in (A.P. Singh).
1381-1169/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S1381-1169(02)00020-1

400
S.M. Kale, A.P. Singh / Journal of Molecular Catalysis A: Chemical 184 (2002) 399–411
more, DPM when chlorinated in the presence of
FeCl3 as catalyst in CCl4, gives monochlorodiphenyl-
methane (MCDPM) with a low yield and selectivity
for the para-product [4]. In another method, DPM
in the presence of CCl4, azobisisobutyronitrile and
ammonium molybdate at 60 ◦C gives MCDPM with
molecular chlorine [5]. Thus, these methods are not
suitable for the preparation of 4,4ꢀ-DCDPM. Also
the homogeneous Lewis acid catalysts pose many
problems in the chlorination reaction like formation
of polychlorinated products, lower regioselectivity,
difficulty of separation of the catalyst from the final
product and the use of the stoichiometric amount of
the catalyst. The use of heterogeneous catalyst, on
the other hand, offers several advantages compared to
their homogeneous counterparts, e.g. ease of recov-
ery, enhanced selectivity and stability and recycling
of the catalyst. Zeolite based catalysts are effective in
meeting current industrial processing objectives and
more stringent environment pollution limits which
require the development of new more active and selec-
tive catalysts. Zeolites are well defined microporous
crystalline materials and have been investigated ex-
tensively and applied as solid catalysts in the field of
petrochemistry [6,7]. However, relatively few reports
are available on the selective chlorination of aromatics
using zeolite catalysts [8–25]. In addition, the chlori-
nation of diphenylmethane in the presence of zeolite
catalysts is limited to patents [26,27]. The main pur-
pose of this study, therefore, is to enhance the selec-
tivity for 4,4ꢀ-dichlorodiphenylmethane in the liquid
phase chlorination of diphenylmethane with sulfuryl
chloride (SO2Cl2) as the chlorinating agent using
zeolite K-L as the catalyst under mild reaction condi-
tions. Sulfuryl chloride, though a milder reagent than
molecular chlorine, is more easily metered and han-
dled in batch reaction studies, by virtue of its being a
liquid.
2. Experimental
Zeolite ZSM-5, beta and K-L samples used in
this study were synthesized hydro-thermally as per
the literature procedures [28–30]. The zeolite thus
formed was washed with deionized water, dried and
calcined at 773 K for 16 h in the presence of air. The
K-forms of these zeolites were prepared by the con-
ventional ion-exchange method, in which the zeolites
were treated thrice in aqueous 1 M KNO3 solution
(10 ml for 1 g catalyst), at 353 K for 8 h with stirring,
washed with deionized water, filtered and dried at
383 K for 2 h.+Zeolite H.K-L was prepared from K-L,
first by NH4 exchange by 1 M NH4NO3 solution
(three exchanges) followed by calcination at 773 K
for 12 h. Various dealuminated K-L zeolites were pre-
pared by treating fresh zeolite K-L (10 g each) with
100 ml aliquots of 0.05, 0.1, 0.3, 0.5, 0.7 M aqueous
solutions of HCl at room temperature. The dealu-
minated zeolites thus obtained were further treated
with 1 M KNO3 to get their K-form. Laporte Inor-
ganics, Cheshire, UK supplied zeolites Na-X, Na-Y
and H-mordenite. These zeolites were converted to
their K-forms following the above ion exchange
procedure.
The SiO2/Al2O3 ratio and the degree of ion ex-
change of these zeolites were determined by a combi-
nation of wet and atomic absorption methods (Hitachi
800). X-ray diffraction (XRD) was carried out on a
Rigaku D-Max/111-VC model using Cu K␣ radiation
for determining the crystallinity and phase purity of
the zeolite samples. No evidence of change in struc-
ture or crystallinity of K-L samples was obtained
after treatment with NH4NO3 or KNO3. The surface
area of the catalysts was measured by the N2 BET
method. The crystal size and morphology of these
catalysts were estimated by scanning electron micro-
scope (Shimadzu, Model 2101PC). All the catalysts
were activated at 523 K for 2 h prior to the reaction.
All the chemicals employed in this study were of
high purity. Sulfuryl chloride was freshly distilled to
a clear fraction (bp 69.5◦ C) before each reaction. A
typical batch reaction procedure was as followed. A
sample of activated catalyst (0.3 g), DPM (0.006 mol),
sulfuryl chloride (0.012 mol) and 1,2-dichloroethane
(EDC) were taken in a mechanically stirred, closed,
50 ml glass reactor fitted with a reflux condenser, a
thermometer and a septum for withdrawing samples,
The present paper describes the use of various cata-
lysts in the selective chlorination of diphenylmethane
with sulfuryl chloride and also compares their activity
with the conventional catalyst, AlCl3. The effect of
solvent, catalyst concentration, reaction temperature,
DPM to SO2Cl2 molar ratio, catalyst recycling, etc.
is also investigated on the conversion of DPM, prod-
uct yields, DCDPM/MCDPM ratio and the selectivity
for 4,4ꢀ-DCDPM (4,4ꢀ-DCDPM/2,4ꢀ-DCDPM isomer
ratio).

S.M. Kale, A.P. Singh / Journal of Molecular Catalysis A: Chemical 184 (2002) 399–411
401
placed in a thermostat at the required reaction temper-
ature. The samples were taken periodically, degassed
thoroughly, neutralized by NaHCO3 and analyzed
by gas-chromatograph (HPGC 6890) equipped with
a capillary column (50 m × 200 ␮m × 0.2 ␮m) with
phenyl methoxy silicone gum. Product identification
was done with reference to standard samples and
GCMS (Shimadzu, QP 2000A).
tivity for 4,4ꢀ-dichlorodiphenylmethane (4,4ꢀ-DCDPM/
2,4ꢀ-DCDPM isomer ratio) over various catalysts such
as K-X, K-Y, K-L, K-ZSM-5, K-beta, K-mordenite,
H.K-L and also the Lewis acid catalyst, AlCl3 and
without any catalyst (blank), in the chlorination of
diphenylmethane with sulfuryl chloride at 333 K under
identical reaction conditions. The reaction produces a
mixture of MCDPM such as 2-chlorodiphenylmethane
(2-CDPM) or (A), 3-chlorodiphenylmethane (3-CD-
PM) or (B) and 4-chlorodiphenylmethane (4-CDPM)
or (C) and DCDPM like 2,4ꢀ-DCDPM (D), 2,2ꢀ-DCD-
PM (E) and 4,4ꢀ-DCDPM (F). Smaller amounts of
the side-chain chlorinated product (␣,␣-DCDPM) (G)
and polychlorinated products (others) (H) are also
obtained (Scheme 1).
Conversion is defined as the percentage of DPM
transformed. The rate of DPM conversion (mmol g−1
h
−1) is calculated as the amount of DPM (mmol) con-
verted per h per g of the catalyst. The yield percentage
of product represents the amount of the product cal-
culated from selectivity multiplied by the conversion
and divided by 100.
The MCDPM are formed by the parallel reaction
by an interaction of an electrophile (Cl+) with DPM
whereas the DCDPM are obtained by the consecutive
reaction of the MCDPM. It is clear from the results
that zeolite K-L is highly active as well as selective
in this reaction compared to the other catalysts and
the conversion of DPM, the rate of DPM conver-
sion, DCDPM/MCDPM ratio and 4,4ꢀ-DCDPM/2,4ꢀ-
DCDPM ratio over zeolite K-L are found to be
96.8 wt.%, 19.2 mmol g−1 h−1, 0.7 and 7.4, respec-
tively, after 1 h of reaction time.
Zeolites K-X, K-Y and K-ZSM-5 and the conven-
tional Lewis acid catalyst, AlCl3, are found to be less
active giving only MCDPM and higher amounts of
polychiorinated products (others). Zeolites K-beta,
K-mordenite and H.K-L are also less active, and give
little dichlorination. Blank reaction also gives very less
3. Results and discussion
3.1. Influence of various catalysts
X-ray diffraction studies indicate high crystallinity
and absence of any other phases in all the samples.
XRD examination also gave no evidence of struc-
ture change of the zeolite sample after the cation
exchange. The scanning electron micrographs reveals
well-defined materials without any occluded material
in the zeolites. The main properties of the zeolites are
summarized in Table 1.
Table 2 compares the conversion of DPM (wt.%),
rate of DPM conversion (mmol g−1 h−1), product
yields (wt.%), DCDPM/MCDPM ratio and the selec-
Table 1
Properties of zeolites
Zeolites
SiO2/Al2O3 (molar ratio)
Cation composition (wt.%)a
Surface areab (m2 g−1
)
Crystal size (␮m)
H+
Na+
K+
K-X
K-Y
2.4
4.1
22.0
41.0
26.0
6.8
–
–
7.5
2.5
9.8
26.1
–
7.4
7.2
2.7
1.4
4.3
–
92.6
92.8
89.8
96.1
85.9
73.9
98.6
615
606
542
410
743
221
215
1.0
1.0
1.0
0.5
0.5
0.2
0.2
K-mordenite
K-ZSM-5
K-beta
H(26.1)K-L
K-L
6.8
1.4
a Na+ and K+ ions were analyzed by XRF. H+ was obtained by the difference between the Al content and the sum of the alkali metal
values. Values are reported as percent of the total cation sites with Al content taken as 100%.
b Measured by N2 adsorption. Value in parentheses represents the percentage of H+ in K-L.

402
S.M. Kale, A.P. Singh / Journal of Molecular Catalysis A: Chemical 184 (2002) 399–411
Table 2
Chlorination of diphenylmethane over various catalystsa
Catalysts
DPM conv.
(wt.%)
Conv. rate
(mmol g−1 h−1
Product yields (wt.%)c
MCDPM
DCDPM/
MCDPM
ratiod
4,4ꢀ/2,4ꢀ-
isomer
ratioe
b
)
DCDPM
A
B
C
D
E
F
G
H
K-X
K-Y
K-L
K-ZSM-5
K-mordenite
K-beta
H.K-L
AlCl3
13.7
20.0
96.8
14.0
17.7
34.9
48.5
34.1
12.2
2.7
4.0
19.1
2.8
3.5
7.0
9.7
6.8
2.4
4.9
0.6
0.7
2.0
4.3
2.0
4.8
4.1
2.0
10.5
6.2
–
–
–
–
–
0.3
0.1
0.1
0.4
0.3
0.4
0.2
0.7
–
1.7
5.1
0.1
0.1
0.3
0.2
–
–
–
–
–
5.8
2.5
4.7
6.9
8.1
11.9
12.2
–
8.3
52.7
4.3
–
34.0
–
0.2
1.4
1.1
–
4.6
0.1
0.8
2.4
1.8
1.6
–
0.8
0.1
0.2
0.2
–
0.7
0.02
0.07
0.13
0.06
0.06
–
7.4
–
0.3
0.6
0.6
–
8.1
17.4
29.4
12.3
1.7
–
–
5.3
–
Blank
–
–
a Reaction conditions: catalyst (g/mol of DPM) = 50.5; DPM (mol) = 0.006; SO2Cl2 (mol) = 0.012; 1,2-dichloroethane (ml) = 2;
reaction temperature (K) = 333; reaction time (h) = 1.
b Rate of DPM conversion is expressed as the mmol of DPM converted per g of catalyst per h.
c MCDPM = monochlorodiphenylmethanes; DCDPM = Dichlorodiphenylmethanes; A = 2-chlorodiphenylmethane; B = 3-chlorodi-
phenylmethane; C = 4-chlorodiphenyimethane; D = 2,4ꢀ-dichlorodiphenylmethane; E = 2,2ꢀ-dichlorodiphenylmethane; F = 4,4ꢀ-dichloro-
diphenylmethane; G = ␣,␣-dichlorodiphenylmethane; H = others (polychlorinated diphenylmethanes).
d DC/MC ratio = dichlorodiphenylmethanes/monochlorodiphenylmethanes ratio.
e 4,4ꢀ/2,4ꢀ ratio = 4,4ꢀ-dichlorodiphenylmethane/2,4ꢀ dichlorodiphenylmethane ratio.
conversion with monochlorinated products. Thus, the
conversion of DPM and product yields mainly depend
upon the type of the catalyst used in the chlorination
reaction. The results demonstrate that the conventional
concept of geometry related shape-selectivity couldn’t
be related alone to explain the role of zeolite K-L
in enhancing the para-selectivity. It is seen that zeo-
lites of similar pore diameter but different structural
types behave in different ways [13,17]. In addition,
Wortel et al. [31] (in the bromination of halobenzenes),
Botta et al. [13] (in the chlorination of biphenyl) and
Singh et al. [19] (in the chlorination of toluene) sug-
gested that factors such as size, charge and position
of the cations and the electrostatic forces produced by
them in the zeolite channels direct the substitution to
get higher selectivity produced by them in the zeolite
Scheme 1.

S.M. Kale, A.P. Singh / Journal of Molecular Catalysis A: Chemical 184 (2002) 399–411
403
Fig. 1. Chlorination of DPM with SO2Cl2: effect of reaction time on the performance of various catalysts. Reaction conditions: see the
footnotes to Table 2.
channels direct the substitution to get higher selectiv-
ity for para-products. It is also observed by Van Dijk
et al. [9] that highly selective para-substitution in the
halogenation of aromatics over zeolite catalysts may
be attributed to a specific orientation of the substrate
in the cavities of the zeolites resulting in the steric
hindrance at the ortho-position and activation of the
para-position by the electrostatic influences in the ze-
olite crystal. The combined effect of all these factors
may be responsible for the selective formation of the
4,4ꢀ-DCDPM in the chlorination of diphenylmethane
over zeolite K-L.
Zeolite K-L also has been found to be highly
active and para-selective in the liquid phase chlorina-
tion of various aromatics such as toluene, o-xylene,
1,2-dichlorobenzene, p-chlorotoluene, benzyl chlo-
ride and cumene [20,22–25,33].
the progress of the reaction. However, zeolite K-L is
highly active giving 96.8 wt.% conversion of DPM
after 1 h which increased to 99.4 wt.% after 6 h of
reaction time. Thus, the reaction is very fast in the
presence of zeolite K-L. The conversion of DPM
over the Lewis acid catalyst, AlCl3 is found to be
lower initially but increased slowly with time giv-
ing 100 wt.% conversion after 5 h. Based on the
conversion of DPM after 6 h of reaction time, the
trend in the activities of the catalysts studied is as
follows:
AlCl3 > K-L > K-Y > H.K-L > K-mordenite
> K-X > K-ZSM-5 > Blank
3.3. Effect of reaction time using zeolite K-L
The performance of zeolite K-L catalyst at 333 K
in terms of DPM conversion (wt.%), product yields
(wt.%), DCDPM/MCDPM and 4,4ꢀ-DCDPM/2,4ꢀ-
DCDPM ratios as a function of time on stream is
presented in Fig. 2. The conversion of DPM and
product yields increase with the duration of the run.
The concentration of DCDPM increases with reac-
3.2. Duration of run using various catalysts
The conversion versus reaction time in the chlori-
nation of DPM over various catalysts under similar
reaction conditions is given in Fig. 1. The conver-
sion of DPM increases over all the catalysts with

404
S.M. Kale, A.P. Singh / Journal of Molecular Catalysis A: Chemical 184 (2002) 399–411
Fig. 2. Effect of reaction time on the conversion of DPM (wt.%), product yields (wt.%), DCDPM/MCDPM and 4,4ꢀ-DCDPM/2,4ꢀ-DCDPM
ratios over zeolite K-L. Reaction conditions: see the footnotes to Table 2.
tion time at the expense of MCDPM and hence the
DCDPM/MCDPM ratio increases with time. It is inter-
esting to note that the yield of 4-CDPM decreases and
simultaneously the yield of 4,4ꢀ-DCDPM increases
with the time which suggests that the formation of
4,4ꢀ-DCDPM takes place by the consecutive reaction
of 4-CDPM. The level of DPM conversion (wt.%)
and the yield of 4,4ꢀ-dichlorodiphenylmethane (wt.%)
are found to be 99.4 and 48.5 wt.%, respectively, after
6 h of reaction time. The selectivity for 4,4ꢀ-DCDPM
(4,4ꢀ-DCDPM/2,4ꢀ-DCDPM ratio) shows a slight
decrease with time on stream. The polychlorinated
products (others) are found to increase with time due
to the increased conversion of DPM. The side-chain
chlorinated product (␣,␣-DCDPM) remains almost
constant throughout the reaction.
uct yields (wt.%), DCDPM/MCDPM as well as
4,4ꢀ-DCDPM/2,4ꢀ-DCDPM ratios obtained in the
chlorination of DPM using zeolite K-L in the presence
of dichloromethane (CH2Cl2), 1,2-dichloroethane
(EDC), 1,1,1-trichloroethane (Cl3CCH3) and chlo-
roform (CHCl3). The nature of the reaction medium
(solvent) plays an important role in the course of
the liquid phase chlorination of aromatics over zeo-
lite catalysts [9,13,20,31]. Among the solvents used,
the highest activity (rate of DPM conversion) is ob-
served in CH2Cl2 whereas the highest selectivity
(4,4ꢀ-DCDPM/2,4ꢀ-DCDPM ratio) is obtained in EDC
at 313 K. The other solvents led to a lower activity as
well as selectivity under similar reaction conditions
at 313 K. Thus, the activity of K-L using these sol-
vents can be arranged in the decreasing order of their
activity at 313 K as follows:
3.4. Influence of solvent
CH2Cl2 > Cl3CCH3 > EDC > CHCl3
Table 3 presents the conversion of DPM (wt.%),
rate of DPM conversion (mmol g−1 h−1), prod-
The overall trend of the isomer ratio over these sol-
vents at 313 K is found to be as follows:

S.M. Kale, A.P. Singh / Journal of Molecular Catalysis A: Chemical 184 (2002) 399–411
405
Table 3
Solvent effecta
Solvent
React
temp. (K)
DPM conv.
(wt.%)
Conv. rate
(mmol g−1 h−1
Product yields (wt.%)c
MCDPM
DCDPM/ 4,4ꢀ-/2,4ꢀ-
b
)
MCDPM
ratiod
isomer
ratioe
DCDPM
A
B
C
D
E
F
G
H
EDCf
313
353
67.4
98.1
13.4
19.4
3.2 0.7 50.8 1.5 0.3 8.3
1.9 0.8 44.3 4.6 1.3 44.4 0.4 0.4 1.1
0.3 2.3 0.2
5.5
9.7
CHCl3
313
333
50.2
50.4
9.9
10.0
7.1 2.8 33.8 2.3 0.3 3.1 0.2 0.6
15.7 3.9 25.9 2.5 1.0
7.5 1.6 49.5 3.6 0.6 7.9
10.7 1.4 46.4 3.7 0.5 6.3
4.1 1.6 55.3 3.2 0.4 10.7
–
–
0.3
–
0.9 0.7 0.1
f
CH3CCl3
CH2Cl2
313
345
72.3
69.8
14.3
13.8
0.4 1.3 0.1
0.4 0.4 0.1
1.3
0.4
313
75.8
15.0
–
–
0.2
0.2
2.2
3.3
a Reaction conditions: catalyst (g/mol of DPM) = 50.5; DPM (mol) = 0.006; SO2Cl2 (mol) = 0.012; solvent (ml) = 2; reaction time
(h) = 1.
b Rate of DPM conversion is expressed as the mmol of DPM converted per g of catalyst per h.
c MCDPM = monochlorodiphenylmethanes; DCDPM = dichlorodiphenylmethanes; A = 2-chlorodiphenylmethane; B = 3-chlorodi-
phenylmethane; C = 4-chlorodiphenyimethane; D = 2,4ꢀ-dichlorodiphenylmethane; E = 2,2ꢀ-dichlorodiphenylmethane; F = 4,4ꢀ-dichloro-
diphenylmethane; G = ␣,␣-dichlorodiphenylmethane; H = others (polychlorinated diphenylmethanes).
d DC/MC ratio = dichlorodiphenylmethanes/monochlorodiphenylmethanes ratio.
e 4,4ꢀ/2,4ꢀ ratio = 4,4ꢀ-dichlorodiphenylmethane/2,4ꢀ-dichlorodiphenylmethane ratio.
f EDC = 1,2-dichloroethane; CH3CCl3 = 1,1,1-trichloroethane.
EDC > CH2Cl2 > Cl3CCH3 > CHCl3
3.5. Influence of catalyst concentration
The rate of DPM conversion has increased markedly
on increasing the reaction temperature to the respec-
tive reflux temperatures in case of all the solvents
except CHCl3. Thus, EDC is found to the best sol-
vent and the conversion of DPM (wt.%) and the 4,4ꢀ-
DCDPM/2,4ꢀ-DCDPM isomer ratio obtained are
98.1 wt.% and 9.7, respectively, with a DCDPM/
MCDPM ratio of 1.1, at 353 K after 1 h of reaction
time. The other solvents give less selectivity at higher
temperatures as compared to EDC.
Presumably, the higher dielectric constant (ionic
medium) of EDC favours the rupture of the Cl–Cl
bond and formation of the electrophile (Cl+) [32]
which results in the formation of higher amounts of
MCDPM and DCDPM. In addition, higher polarity
of EDC enhances the 4,4ꢀ-DCDPM/2,4ꢀ-DCDPM iso-
mer ratio. Furthermore, others [13,14] have suggested
that solvents may influence the activation of the reac-
tants or affect the adsorption and diffusion processes
in the zeolite channels which may enhance the para-
selectivity.
Fig. 3 shows the effect of concentration of zeolite
K-L in the range of 0 to 117.8 g/mol of DPM on
the conversion of DPM, product yields, DCDPM/
MCDPM and 4,4ꢀ-DCDPM/2,4ꢀ-DCDPM ratios at
333 K for 0.083 h (5 min) of reaction time in the
chlorination of DPM with SO2Cl2. Only MCDPM
is formed with a very low conversion of DPM when
no catalyst is used. The conversion of DPM in-
creased from 30.4 to 98.6 wt.% when the catalyst
loading is increased from 16.8 to 117.8 g/mol of
DPM, respectively. Also, the yield of 4,4ꢀ-DCDPM
increases with a decrease in the 4-CDPM yield as
the concentration of catalyst K-L is increased. Thus,
47.1 wt.% 4,4ꢀ-DCDPM is obtained at 98.6 wt.%
conversion level of DPM after 0.083 h of reaction
time at the catalyst concentration of 117.8 g/mol of
DPM.
The DCDPM/MCDPM as well as 4,4ꢀ-DCDPM/2,4ꢀ-
DCDPM ratios also increase with an increase in the
catalyst concentration.

406
S.M. Kale, A.P. Singh / Journal of Molecular Catalysis A: Chemical 184 (2002) 399–411
Fig. 3. Effect of catalyst (K-L) concentration on the conversion of DPM (wt.%), product yields (wt.%), DCDPM/MCDPM and
4,4ꢀ-DCDPM/2,4ꢀ-DCDPM ratios. Reaction conditions: DPM (mol) = 0.006; SO2Cl2 (mol) = 0.012; EDC (ml) = 2; reaction temperature
(K) = 333; reaction time (h) = 0.083.
Fig. 4. Effect of reaction temperature on the conversion of DPM (wt.%), rate of DPM conversion (mmol g−1 h−1), product yields (wt.%),
DCDPM/MCDPM and 4,4ꢀ-DCDPM/2,4ꢀ-DCDPM ratios over zeolite K-L. Reaction conditions: catalyst (K-L) (g/molofDPM) = 50.5;
DPM (mol) = 0.006; SO2Cl2 (mol) = 0.012; reaction time (h) = 0.083.

S.M. Kale, A.P. Singh / Journal of Molecular Catalysis A: Chemical 184 (2002) 399–411
407

408
S.M. Kale, A.P. Singh / Journal of Molecular Catalysis A: Chemical 184 (2002) 399–411
3.6. Influence of reaction temperature
solutions of HCl (0.05–0.7 M HCl). The results are
presented in Table 4. As can be seen from the re-
sults, the conversion of DPM decreases from 67.4 to
44.1 wt.% after 0.083 h (5 min) of reaction time, when
the SiO2/Al2O3 ratio of zeolite K-L is increased from
6.82 to 9.01, respectively. The DCDPM/MCDPM and
4,4ꢀ-DCDPM/2,4ꢀ-DCDPM ratios decrease with an
increase in the framework SiO2/Al2O3 ratio of zeolite
K-L. The higher catalytic activity of fresh zeolite K-L
compared to the treated zeolite K-L may be due to the
lower SiO2/Al2O3 ratio thus giving higher concentra-
tion of aluminium which in turn gives higher number
of basic sites for the reaction. The low activity of
0.7 M HCl treated zeolite K-L may be attributed to a
combined effect of higher SiO2/Al2O3 ratio and lower
crystallinity of zeolite K-L. Thus, higher numbers of
basic sites as well as good crystallinity of zeolite K-L
are the most important factors for the liquid phase
chlorination of DPM.
The effect of reaction temperature on the conver-
sion of DPM (wt.%), rate of DPM conversion (mmol
g
−1 h−1), product yields (wt.%), DCDPM/MCDPM
as well as 4,4ꢀ-DCDPM/2,4ꢀ-DCDPM ratios over ze-
olite K-L in the liquid phase chlorination of DPM
with SO2Cl2 is illustrated in Fig. 4. As expected,
the rate of DPM conversion increases from 66.3 to
196.6 mmol g−1 h−1 when the reaction temperature
is increased from 313 to 363 K, respectively, after
0.083 h (5 min) of reaction time. At lower tempera-
ture (313 K) no DCDPM is detected. The DCDPM/
MCDPM as well as the 4,4ꢀ-DCDPM/2,4ꢀ-DCDPM
ratios increase with an increase in the reaction tem-
perature.
The formation of 4,4ꢀ-DCDPM is favoured at higher
temperature. The yield of 4-CDPM decreases thus in-
creasing the required product (4,4ꢀ-DCDPM) with an
increase in the reaction temperature. Thus, 25.5 wt.%
4,4ꢀ-DCDPM is obtained at 82.7 wt.% conversion
level of DPM after 0.083 h of reaction time at 363 K.
3.8. Influence of DPM/SO2Cl2 molar ratio
The conversion of DPM, product yields, DCDPM/
MCDPM as well as 4,4ꢀ-DCDPM/2,4ꢀ-DCDPM ra-
tios obtained at different DPM/SO2Cl2 molar ratios
are demonstrated in Table 5. The conversion of DPM
and the rate of DPM conversion decrease from 73.3
to 17.2 wt.%, and 175.0 to 41.1 (mmol g−1 h−1),
3.7. Influence of HCl treated K-L catalysts
The chlorination of DPM was studied with zeo-
lite K-L with different SiO2/Al2O3 ratio obtained
by the treatment of parent K-L with various molar
Table 5
Influence of DPM/SO2Cl2 molar ratioa
DPM/SO2Cl2 DPM conv.
Conv. Rate
(mmol g−1 h−1
)
Product yields, (wt.%)c
MCDPM
DCDPM/
MCDPM
ratiod
4,4ꢀ/2,4ꢀ-
isomer
ratioe
b
molar ratio
wt.%
DCDPM
A
B
C
D
E
F
G
H
0.33
0.5
1
2
3
73.3
67.4
43.4
23.7
17.3
17.2
175.0
160.9
103.6
56.6
41.3
41.1
3.1
3.2
2.3
2.8
0.6
–
2.1
1.1
0.8
1.2
0.2
–
55.2
53.9
36.7
19.7
16.5
17.2
1.5
1.1
0.5
–
–
–
0.3
0.3
0
–
–
10.5
7.6
2.9
–
–
–
0.1
0.1
0.5
0.1
0.2
–
–
–
0.2
0.2
0.1
–
–
–
7
6.9
5.8
–
–
–
–
–
–
5
–
a Reaction conditions: Catalyst (g/mol of DPM) = 50.5; DPM (mol) = 0.006; 1,2-dichloroethane (ml) = 2; reaction temperature
(K) = 333; reaction time (h) = 0.083.
b Rate of DPM conversion is expressed as the mmol of DPM converted per g of catalyst per h.
c MCDPM
=
monochlorodiphenylmethanes; DCDPM
=
dichlorodiphenylmethanes;
A
=
2-chlorodiphenylmethane;
B
=
3-chlorodiphenylmethane; C = 4-chlorodiphenyimethane; D = 2,4ꢀ-dichlorodiphenylmethane; E = 2,2ꢀ-dichlorodiphenylmethane; F =
4,4ꢀ-dichlorodiphenylmethane; G = ␣,␣-dichlorodiphenylmethane; H = others (polychlorinated diphenylmethanes).
d DC/MC ratio = dichlorodiphenylmethanes/monochlorodiphenylmethanes ratio.
e 4,4ꢀ/2,4ꢀ ratio = 4,4ꢀ-dichlorodiphenylmethane/2,4ꢀ-dichlorodiphenylmethane ratio.

S.M. Kale, A.P. Singh / Journal of Molecular Catalysis A: Chemical 184 (2002) 399–411
409

410
S.M. Kale, A.P. Singh / Journal of Molecular Catalysis A: Chemical 184 (2002) 399–411
respectively, when the DPM/SO2Cl2 molar ratio is
increased from 0.33 to 5, after 0.083 h (5 min) of re-
action time. The higher molar ratios of DPM/SO2Cl2
(DPM/SO2Cl2 = 2, 3 and 5) give only the formation
of MCDPM with a lower conversion of DPM. The
DCDPM starts appearing at the DPM/SO2Cl2 molar
ratio of 1. Thus, 2.9 wt.% 4,4ꢀ-DCDPM is obtained at
a DPM/SO2Cl2 molar ratio of 1 which is increased to
10.5 wt.% at a DPM/SO2Cl2 molar ratio of 0.33 and
at 0.083 h (5 min) reaction time.
Cl2 → Cl+ + Cl−
ArH + Cl+ → (ArHCl)+
(ArHCl)+ → ArCl + H+
(2)
(3)
(4)
(5)
H
+ + Cl− → HCl
where Ar = DPM.
A Wheland intermediate is first formed (Eq. (3))
which then deprotonates into the reaction prod-
uct (Eq. (4)). The dichlorodiphenylmethanes are
formed by the consecutive reactions of the mono-
chlorodiphenylmethanes. The side-chain chlorinated
product (␣,␣-DCDPM) is obtained by the radical
mechanism.
3.9. Recycle of the zeolite K-L
Table 6 gives the results of a catalyst recycling
experiment using zeolite K-L in the chlorination of
DPM at 333 K. After the completion of each reaction,
the zeolite K-L was separated from the reaction mix-
ture by filtration, washed with acetone and calcined
in air at 773 K for 12 h. It is then characterized for
the chemical composition and crystallinity. All the
data refers to the calcined samples. The aluminium
and potassium content as well as crystallinity of K-L
samples has been found to decrease after the first re-
cycle. It has been observed that the activity of zeolie
K-L is decreased in the first recycle with a drastic
decrease in the 4,4ꢀ-DCDPM/2,4ꢀ-DCDPM ratio from
6.9 to 0.9, respectively, after 0.083 h (5 min) of reac-
tion time. The sulfur dioxide and hydrochloric acid
evolve continuously during the reaction, which affects
the catalyst activity. In addition, the HCl formed in
the reaction extracts aluminium and to some extent
potassium from the framework positions of zeolite
K-L. Such type of extractions and the decrease in the
crystallinity of zeolite K-L attribute to the decrease in
the catalytic activity of zeolite K-L in the chlorination
of DPM.
4. Conclusions
The 4,4ꢀ-DCDPM is formed selectively over ze-
olite K-L in the liquid phase chlorination of DPM
with sulfuryl chloride as the chlorinating agent under
mild reaction conditions. Other zeolite catalysts as
well as the conventional Lewis acid catalyst, AlCl3,
are less selective compared to zeolie K-L. The yield
of 4,4ꢀ-DCDPM increases with the duration of the
run, catalyst (K-L) concentration, reaction temper-
ature and concentration of the chlorinating agent
(SO2Cl2). In all these cases, the 4,4ꢀ-DCDPM is ob-
tained at the expense of the 4-CDPM, thus reducing
the yield of MCDPM. 1,2-dichloroethane is found to
be the best solvent and gives the highest selectivity
for 4,4ꢀ-DCDPM (4,4ꢀ-DCDPM/2,4ꢀ-DCDPM isomer
ratio = 9.7) at 353 K after 1 h. The increase in the
SiO2/Al2O3 molar ratio of zeolite K-L (by HCl treat-
ment) progressively decreases the activity as well
as the selectivity of the catalyst. On recycling, the
conversion of DPM and 4,4ꢀ-DCDPM/2,4ꢀ-DCDPM
isomer ratio decreases due to the extraction of small
amount of aluminium and potassium (by HCl pro-
duced in the reaction) as well as the decrease in the
crystallinity of zeolite K-L. Reaction path involves
the formation of molecular chlorine by the decompo-
sition of the sulfuryl chloride which then undergoes
heterolytic dissociation into an electrophile (Cl+) by
the catalyst, thus giving an electrophilic aromatic
substitution of the DPM ring and resulting in the
formation of MCDPM and DCDPM.
3.10. Reaction mechanism
The ring chlorination of diphenylmethane takes
place by an ionic mechanism, in the presence of cata-
lysts. Sulfuryl chloride is first decomposed thermally
to sulfur dioxide and molecular chlorine (Eq. (1)). The
latter in the presence of catalyst, cleaves heterolyti-
cally or is polarized and the positive halogen serves as
the electrophile for the aromatic substitution (Eq. (2)).
SO2Cl2 → SO2 + Cl2
(1)

S.M. Kale, A.P. Singh / Journal of Molecular Catalysis A: Chemical 184 (2002) 399–411
411
Acknowledgements
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[14] T. Nakamura, K. Shinoda, K. Yasuda, Chem. Lett. (1992)
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[15] T. Suzuki, T. Komatsu, Ihara Chem. Ind., US Patent 4 831
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[16] L. Delaude, P. Laszlo, J. Org. Chem. 55 (1990) 5260.
[17] P. Ratnasamy, A.P. Singh, S. Sharma, Appl. Catal. A 135
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S.M. Kale thanks the Council of Scientific and
Industrial Research, New Delhi, for Senior Research
Fellowship.
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