Single-stage oxychlorination of ethanol to ethylene dichloride using a dual-catalyst bed

Article abstract of DOI:10.1016/j.apcata.2010.08.036

The direct production of ethylene dichloride, EDC, from ethanol over a dual-catalyst bed consisting of a zeolite pre-bed and a CuCl₂-NaCl/ γ-Al₂O₃ oxychlorination catalyst has been shown to give greater than 80% yield of EDC with ethyl chloride as the main by-product. The effects of temperature, HCl/air ratio and space velocity were investigated. The most effective zeolite was ZSM-5. It is concluded that the main route to EDC was via ethyl chloride and its oxychlorination and disproportionation.

Full text of DOI:10.1016/j.apcata.2010.08.036

Applied Catalysis A: General 388 (2010) 96–101
Contents lists available at ScienceDirect
Applied Catalysis A: General
journal homepage: www.elsevier.com/locate/apcata
Single-stage oxychlorination of ethanol to ethylene dichloride using a
dual-catalyst bed
∗
Rashid Al-Hajri, David Chadwick
Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 25 May 2010
Received in revised form 31 July 2010
Accepted 18 August 2010
Available online 26 August 2010
The direct production of ethylene dichloride, EDC, from ethanol over a dual-catalyst bed consisting of a
zeolite pre-bed and a CuCl2–NaCl/␥-Al2O3 oxychlorination catalyst has been shown to give greater than
8
0% yield of EDC with ethyl chloride as the main by-product. The effects of temperature, HCl/air ratio
and space velocity were investigated. The most effective zeolite was ZSM-5. It is concluded that the main
route to EDC was via ethyl chloride and its oxychlorination and disproportionation.
©
2010 Elsevier B.V. All rights reserved.
Keywords:
Ethylene dichloride
Ethanol
Oxychlorination
Zeolite
1
. Introduction
replacement of hydrocarbon feedstocks. Ethanol is already pro-
duced on a large scale by fermentation from biomass material
such as sugar cane or corn for fuel application [2,3]. It can also be
produced from biomass via syn-gas [4–6]. Usually, ethanol is first
dehydrated to ethylene and this process is energy integrated with
the conventional ethylene conversion processes [7]. However, the
development of single-stage processes, in which ethanol is con-
verted directly to bulk chemicals, would provide greater process
intensification but requires new catalysts. No scientific literature
has been found reporting the oxychlorination of ethanol to EDC. US
patent 2,442,285 (1948) claimed a process for the direct production
Ethylene dichloride, EDC is a major chemical intermediate
and belongs to the group of chemicals with the highest annual
production rate. Its main use is in the manufacture of vinyl chlo-
ride monomer, VCM, which comprises 95% of EDC use, while
the remaining goes to the production of ethylene amines, 1,1,1-
trichloroethane and vinylidene chloride. EDC is produced from
ethylene either by direct chlorination using chlorine (1), or by oxy-
chlorination with HCl as the chlorinating agent (2).
C H + Cl → ClH CCH Cl
(1)
(2)
(3)
2
4
2
2
2
◦
of EDC from ethanol at 230–290 C over alumina supported CuCl2
catalyst containing NaCl [8]. A good yield of EDC was reported but
no performance data was given. US patents 4,814,527 (1989) and
C H + 2HCl + 1/2O → ClH CCH Cl + H O
2
4
2
2
2
2
ClH CCH Cl → H CCHCl + HCl
2
2
2
4
,910,176 (1990) claimed the selective production of EDC and ethy-
Generally in modern plants these two processes are balanced
so that the HCl produced by cracking of EDC to make VCM (3) is
sufficient for the oxychlorination reaction (2) and no net import
of HCl is required. Typical catalysts for ethylene oxychlorination
are based on CuCl2 supported on alumina with minor amounts of
promoters such as alkali metals and lanthanum chloride [1].
Ethylene is normally produced by catalytic cracking or steam
cracking of hydrocarbons at high temperatures. However the devel-
opment of sustainable and environmental friendly feedstocks for
the production of petrochemical products is needed. Ethanol, in
particular, is considered to be a promising renewable source for
lene from ethyl chloride or ethanol over bifunctional CuCl2/zeolite
catalysts, which combine dehydration (zeolite) and oxychlorina-
tion (CuCl2) functions [9,10].
This paper reports the single-stage production of EDC from
ethanol using a dual-catalyst bed configuration consisting of a zeo-
lite catalyst in the first bed and a typical CuCl2 oxychlorination
catalyst in the second bed. The use of the dual-bed configuration
overcomes some of the difficulties of making a truly bifunctional
catalyst: achieving complete dehydration of ethanol and subse-
quently oxychlorination to EDC, while avoiding cracking of the
product EDC to VCM on the acid sites (which can lead to production
of heavy products). It allows oxychlorination and dehydration func-
tions to be optimised independently while still achieving the aim of
conversion of ethanol to EDC in a single stage. Zeolites were used for
the pre-bed because of their high acidity, activity for dehydration,
∗ Corresponding author. Tel.: +44 2075945579.
E-mail address: d.chadwick@imperial.ac.uk (D. Chadwick).
0
926-860X/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.apcata.2010.08.036

R. Al-Hajri, D. Chadwick / Applied Catalysis A: General 388 (2010) 96–101
97
Nomenclature
AcA
DEE
EtCl
EDC
EtOH
GHSV
TCA
VCM
X
acetaldehyde
diethyl ether
ethyl chloride
1,2-dichloroethane
ethanol
gas hourly space velocity, h
trichloroethane
vinyl chloride monomer
conversion
−1
and stability at the temperatures typically used for ethylene oxy-
◦
chlorination (200–350 C). In particular, ZSM-5 was compared with
Fig. 1. XRD of 14 wt%CuCl2 + 5 wt%NaCl/␥-Al2O3 (a) as prepared; (b) treated in argon
at 300 C.
◦
mordenite and Y-zeolite, which provide a range of acid strengths
and structure, and which have been studied widely for the dehy-
dration of ethanol [11–14]. Mordenite has been shown to be highly
active for dehydration of ethanol to ethylene at temperatures as
◦
(counter current configuration at 150 C) where it mixed with an
Ar flow. The ethanol/argon mixture was then fed into a mixer/pre-
heater made of glass lined s.s. tubing where HCl and air were added
to adjust the reactor feed composition. For experiments with ethyl
chloride, ethyl chloride/N2 premixed gas was supplied to the feed
gas mixer/pre-heater via a mass flow controller. To avoid corro-
sion and product reactions in the reactor exit lines, PFA tubing was
used for all lines prior and after the reactor containing HCl. The
lines were trace heated to avoid any condensation. NaOH solution
and Norit activated carbon were used as scrubber for any unre-
acted HCl and halogenated products. The product stream from the
reactor was analyzed continuously by online FID GC with a Car-
bopack B column. Using a temperature program (isothermal at
◦
low as 180 C [13]. It was expected, therefore, that ethanol would
be dehydrated over the zeolite in the first bed producing ethylene,
and that the product ethylene would be oxychlorinated to EDC in
the presence of HCl and air over the CuCl2 catalyst in the second
bed. However, we show that the main route to EDC is via formation
ethyl chloride and its subsequent oxychlorination and dispropor-
tionation. The effects of reaction temperature, feed composition,
and space velocity were studied. In addition, the performance of
the dual-bed configuration is compared to a physical mixture. We
demonstrate that greater than 80% yield of EDC can be achieved
directly from ethanol when ZSM-5 is used in the pre-bed.
◦ ◦
5 C for 4 min, increase of temperature up to 220 C with a heat-
ing rate of 8 C/min and then hold at 220 C for 5 min) ethylene,
EtCl, ethanol and EDC were easily separated at retention times of
4
◦
◦
2
. Experimental
1
.9, 6.2, 6.8 and 15.1 min, respectively. The main by-products were
2.1. Catalyst preparation and pretreatment
also readily identified. The response factors for chlorinated com-
pounds were determined using a calibration mixture obtained from
Restek. Data was taken over 1 h time-on-stream at each condition.
There was no noticeable deactivation. The carbon balances were
Na-mordenite(13), Y-zeolite(60), ZSM-5(280) and ZSM-5(50)
were obtained from Zeolyst and checked by XRD. The number in
parentheses is the SiO /Al O ratio. NH -mordenite was prepared
2
2
3
4
±
2% at all the conditions studied demonstrating that the produc-
tion of carbon oxides was very small. Values of selectivity are given
in mol%.
by ion-exchange method with NH NO . The H-forms of the zeolites
4
3
◦
were prepared by calcination at 550 C in air for 10 h ex situ imme-
diately before use. The oxychlorination catalyst for the second bed,
1
4 wt%CuCl + 5 wt%NaCl on ␥-Al O , was prepared according to
2 2 3
the procedure described in US patent 2,442,285 (1948) [8]. The Cu
content of the catalyst was determined by ICP. BET surface area was
3. Results and discussion
2
determined to be 150 m /g. The catalyst and pre-bed was heated
3.1. Reactions over CuCl2–NaCl/ꢀ-Al2O3
◦
overnight in situ in the reactor at 300 C with argon flow. This treat-
ment was carried out in order to activate the zeolite pre-bed in situ
and also to remove water of hydration from the CuCl2 catalyst. The
temperature was then decreased to the reaction temperature and
a flow of HCl and air was passed over the catalyst for 1 h before
introducing the ethanol flow.
3.1.1. Catalyst characterisation
XRD of the CuCl2–NaCl/␥-Al2O3 catalyst as prepared and after
◦
in situ pretreatment at 300 C in Ar is given in Fig. 1. In the as
prepared catalyst, Fig. 1a, the diffraction peaks of CuCl2·2H2O are
clearly seen. From XRD the average particle size of the supported
CuCl ·2H O was estimated to be 15 nm. After the pretreatment no
2
2
2.2. Catalyst activities
diffraction peaks from Cu species were detected. Redistribution of
Cu in oxychlorination catalysts is well known [15], and could be a
contributory factor to the loss of diffraction peaks. TEM analysis of
the spent catalysts, however, revealed a reasonably even covering
of particles of about 15 nm diameter on the alumina support. From
this we conclude that the CuCl2·2H2O particles lose crystallinity
when the water of hydration is removed by heating in Ar and may
also partially oxidise on exposure to air [15], but the majority of the
particles remain about 15 nm in diameter.
A 10 mm I.D. tubular flow reactor was used to study the gas
phase reaction. The reactor was electrically heated and the temper-
ature was controlled by a thermocouple placed in the centre of the
catalyst bed. 0.7 g of zeolite and 0.7 g of CuCl catalyst (0.5–0.85 mm
2
particle diameter) were each mixed with SiC at 4:1 dilution and
placed as separate beds in the middle of the reactor supported by
quartz wool from both ends. The same dilution was used for stud-
ies of single catalysts. Values of GHSV are based on the undiluted
catalyst volume (either zeolite or CuCl2 catalyst). Gas feeds (ethy-
lene, Ar, air, N , HCl/N ) to the reactor were controlled by mass flow
3.1.2. Ethylene oxychlorination
The C H oxychlorination activity of catalyst was tested at
2
2
2
◦
4
controllers. Liquid ethanol was pumped into an evaporator/mixer
250–300 C with a close to stoichiometric feed composition of 9,

9
8
R. Al-Hajri, D. Chadwick / Applied Catalysis A: General 388 (2010) 96–101
Table 1
C2H4 oxychlorinationa over 14 wt%CuCl2–5 wt%NaCl/␥-Al2O3.
used compared to ethylene (therefore lower kinetic driving force),
suggests that the direct oxychlorination route is more significant
especially at the higher temperature.
T
C2H4
Product selectivity, %
◦
C
X, %
VCM
EtCl
EDC
CH CH Cl ↔ C H + HCl
(4)
(5)
(6)
3
2
2
4
2
2
3
50
75
00
6.2
8.2
26
0.00
0.00
0.24
1.4
1.0
0.47
99
99
99
2
CH CH Cl + O → C H + ClCH CH Cl + H O
3
2
2
2
4
2
2
2
a
−1
Feed (vol%): 9%C2H4, 18%HCl, 31%air; GHSV = 11550 h ; 1 barg.
CH CH Cl + HCl + 1/2O → ClH CCH Cl + H O
3
2
2
2
2
2
Table 2
EtCl reactiona with HCl/air over 14 wt%CuCl2–5 wt%NaCl/␥-Al2O3.
3.1.4. Ethanol oxychlorination
The EDC yield from ethanol oxychlorination over CuCl –NaCl/␥-
2
T
EtCl
Product selectivity, %
◦
Al O was low at 250–300 C; the main product was EtCl with
2
3
◦
selectivities of over 80%, Table 3. This contrasts sharply with US
patent 2,442,285 (1948) which claimed a good yield of EDC from
ethanol in the same temperature range [8]. The activity for ethanol
conversion to EtCl was much higher than for ethylene or ethyl chlo-
ride oxychlorination to EDC at the same conditions, which is a clear
indication that EtCl is formed by the rapid direct hydrochlorination
of ethanol (7), and not by dehydration to ethylene (8) followed by
hydrochlorination of ethylene by reverse of (4). In fact as pointed
out above, the equilibrium of (4) lies towards ethylene at the con-
ditions used and it does not take place at a significant rate over the
catalyst.
C
X, %
C2H4
EDC
TCA
2
2
3
50
75
00
1.1
9.0
35
30
13
4.5
70
87
95
0.00
0.00
0.65
TCA: trichloroethane.
a
−1
Feed (vol%): 2%EtCl, 18%HCl, 31%air; GHSV = 11550 h ; 1 barg.
1
1
8, and 31 vol% for C H , HCl, and air respectively at a GHSV of
2 4
1,550 h . This feed composition and reaction temperature is typ-
ical of industrial oxychlorination processes [16]. The results are
given in Table 1. The catalyst showed good activity for C H4 oxy-
−1
2
chlorination with high selectivity to EDC. Small amounts of EtCl
and VCM were detected with a total selectivity less than 2%. VCM
increased with increasing temperature due to dehydrochlorination
C H5OH + HCl → CH CH Cl + H O
(7)
(8)
2
3
2
2
C H5OH → C H + H O
2
2
4
2
of the product EDC over the ␥-Al O3 according to reaction (3). The
2
◦
ethylene conversion reached 25% at 300 C with corresponding to
EDC increases as temperature and selectivity to EtCl falls
−1
−1
a reaction rate of 3.2 mmol l
of 70 kJ/mol.
s , and apparent activation energy
suggesting a sequential reaction of EtCl to EDC, mainly by oxychlo-
rination (6) as noted above (there is a loss of selectivity to EtCl at the
lower temperature due to the formation of oxygenated by-products
such as acetaldehyde), Table 3. The EDC cracking to VCM was very
low at all conditions due to the low acidity of the NaCl promoted
3
.1.3. Ethyl chloride oxychlorination
Ethyl chloride oxychlorination was studied from 250 to 300 C
◦
␥
-Al O catalyst and agrees well with the findings of Carmello et
with a feed composition of 2, 18, and 31 vol% for EtCl, HCl, and air,
respectively. The results are given in Table 2. The reaction selec-
tively produced EDC and ethylene with the selectivity to ethylene
falling as temperature increased. Trichloroethane, TCA, was the
only significant by-product, which is produced by the hydrochlo-
rination reaction of VCM which was not detected. The conversions
2 3
al. [17]. Diethyl ether (DEE) is observed at the higher temperatures
due to a small amount of dehydration of ethanol on the ␥-Al O3
support. The low selectivity to ethylene is also due to the low acid-
2
ity of the catalyst which does not dehydrate ethanol to ethylene
◦
significantly below 300 C [14].
◦
The effect of temperature on the extent of these reactions was
opposite to that reported in US patents 4,814,527 (1989) and
at 250 and 275 C are lower and similar in magnitude to ethylene
oxychlorination, Table 1, which might be taken as evidence that
the route to EDC may be via dehydrochlorination as in (4) followed
by oxychlorination of ethylene according to (2). Thermodynamic
calculation by Aspen shows that the equilibrium of (4) lies toward
ethylene at the conditions used. However, reaction (4) is known
to be catalysed by acidic sites on the alumina support which are
4
,910,176 (1990) [9,10], although it was noted that the ratio of
EDC/ethylene could be varied over a wide range by balancing the
CuCl2 loading and support acidity. Our results show that higher
reaction temperature favours the production of EDC rather C H .
This is a consequence of the dominance of the direct oxychlori-
nation of EtCl (6) due to the high loading of CuCl2 compared to
the zeolite supported catalysts of US patents 4,814,527 (1989) and
2
4
blocked by CuCl and NaCl in typical oxychlorination catalysts [17],
2
suggesting that this is not the main route to EDC. The dispropor-
tionation of EtCl to EDC and ethylene (5) followed by ethylene
oxychlorination to EDC by (2) and direct oxychlorination of ethyl
4
,910,176 (1990), and the relatively low catalyst acidity. In any
case, any produced ethylene from disproportionation (5) and/or
dehydrochlorination of EtCl (4), would be oxychlorinated to pro-
duce more EDC as the temperature increased further increasing
the selectivity to EDC.
◦
chloride to EDC (6) can also take place. At 300 C, the conversion
of ethyl chloride to EDC, Table 2, is greater than that of ethylene
to EDC, Table 1. The much lower concentration of ethyl chloride
Table 3
EtOH oxychlorinationa over 14 wt%CuCl2–5 wt%NaCl/␥-Al2O3.
Temperature
EtOH
Product selectivity, %
◦
C
X, %
C2H4
CH3Cl
AcA
VCM
EtCl
CHCl3
DEE
EDC
250
275
300
64
76
80
0.33
0.68
1.1
0.10
0.17
0.22
6.4
0.97
0.73
0.00
0.00
0.08
88
95
83
0.00
0.00
0.00
0.00
0.08
0.07
5.0
3.4
15
AcA: acetaldehyde; DEE: diethyl ether.
a
−1
Feed (vol%): 8%EtOH, 18%HCl, 31%air; GHSV = 11550 h ; 1 barg.

R. Al-Hajri, D. Chadwick / Applied Catalysis A: General 388 (2010) 96–101
99
Table 4
a
Effect of space velocity at different reaction temperatures .
GHSV, h 1
−
T
EtOH
Product selectivity, %
◦
Bed 1
Bed 2
C
X, %
C2H4
CH3Cl
AcA
VCM
EtCl
DEE
EDC
2
275
50
94
98
99
5.9
4.7
0.93
0.11
0.12
0.08
0.07
0.22
0.29
0.07
0.07
0.07
79
45
15
0.02
0.01
0.00
15
50
84
1
1550
1550
11550
3
00
50
2
95
94
96
7.5
7.7
3.5
0.11
0.08
0.05
0.17
0.41
0.34
0.07
0.12
0.10
79
61
38
0.01
0.02
0.04
13
31
58
1
23100
275
00
3
AcA: acetaldehyde; DEE: Diethyl ether.
a
Bed 1: ZSM-5(50), bed 2: 14 wt%CuCl2–5 wt%NaCl/␥-Al2O3; feed (vol%):8%EtOH, 18%HCl, 31%air; 1 barg.
conversion and EDC selectivity was obtained using the ZSM-5(50)
pre-bed, giving 99% EtOH conversion, 84% EDC selectivity and an
estimated HCl conversion of 80%. The lower ethanol conversion
observed using mordenite in the pre-bed, despite its known high
ethanol dehydration activity [13], is probably due to the presence of
a significant proportion of alumina binder leading to a lower zeolite
actual content.
Ethanol oxychlorination over 14 wt%CuCl –5 wt%NaCl/␥-Al O
2
2
3
produced mainly EtCl as reported above, Table 3, while ethylene
and EtCl itself are rapidly oxychlorinated to EDC, Tables 1 and 2,
respectively. In the dual-catalyst bed configuration EDC is formed,
therefore, from oxychlorination of the EtCl and ethylene produced
in the zeolite pre-bed over the 14 wt%CuCl –5 wt%NaCl/␥-Al O
2
2
3
catalyst with the formation and oxychlorination of EtCl being the
main route to EDC. As discussed below the relatively high yield of
EDC with a ZSM-5(50) pre-bed apparent in Fig. 2 is due to the high
yields of EtCl and ethylene from ethanol obtained over ZSM-5(50),
Table 6.
◦
Fig. 2. EtOH oxychlorination over dual-catalyst bed at 300 C. Bed 1 = zeolite;
bed 2 = 14 wt%CuCl2–5 wt%NaCl/␥-Al2O3. Selectivities are given to ethylene, ethyl
chloride and EDC. Other includes: CH3Cl, acetaldehyde, VCM, diethyl ether, and
trichloroethane.
3
.2.2. Effects of temperature and space velocity
3
.2. Ethanol oxychlorination over the dual-catalyst bed
A pre-bed of ZSM-5(50) was used to explore the effects of
configuration
◦
temperature, 250–300 C and space velocity on the product dis-
tribution, Table 4. Higher space velocity over the oxychlorination
catalyst in the dual-catalyst bed system was achieved by reduc-
ing the catalyst volume of the second bed (and a corresponding
increase in the dilution), so that the flow rate and hence residence
time in the pre-bed remained unchanged. The ethanol conversion
was always high and decreased only slightly at the higher space
velocity showing that almost all the ethanol was converted over
the ZSM-5 pre-bed. The selectivity to EDC decreased sharply for
the higher space velocity indicating that it is formed almost exclu-
sively on the second bed. This was confirmed by a study of ethanol
reaction with HCl and air over the ZSM-5(50) alone, Table 6, which
shows almost the same ethanol conversion, but low selectivity to
EDC and higher selectivities to ethylene and ethyl chloride at the
same reaction temperature. At both space velocities, the selectivity
to EDC increased with reaction temperature at the expense of EtCl,
further underlining the sequential nature of EDC formation.
3
.2.1. Effect of zeolite
The direct production of EDC from EtOH was carried out at
◦
2
50–300 C using a dual-catalyst bed configuration consisting of a
zeolite catalyst in the pre-bed and the 14 wt%CuCl –5 wt%NaCl/␥-
Al O catalyst in the second bed. A range of zeolites (ZSM-5(50),
ZSM-5(280), mordenite(13), Y-zeolite(80)) were investigated ini-
tially for the pre-bed spanning variation in acidity and structure. In
general, while EtCl was the main product at 250 C EDC increased
with temperature becoming the main product for all except the
ZSM-5(280) pre-bed at 300 C. Fig. 2 shows the results obtained
at 300 C, 1 barg operating pressure, 11,550 h
the volume of the CuCl2 catalyst bed or zeolite catalyst bed) with a
feed gas composition of 8 vol%EtOH, 18 vol%HCl, and 31 vol%air. The
2
2
3
◦
◦
◦
−1
GHSV (based on
◦
selectivity to VCM was very low reaching 0.3% maximum at 300 C
indicating a low EDC cracking rate over the dual-bed catalyst con-
figuration. By far the best performance in terms of both ethanol
Table 5
a
Effect of feed gas composition .
Feed composition vol%
EtOH
Product selectivity, %
EtOH
HCl
Air
X, %
C2H4
CH3Cl
AcA
VCM
EtCl
DEE
EDC
8
8
8
32
18
12
31
31
31
87
93
96
5.7
9.9
15
0.06
0.07
0.12
0.34
0.56
0.54
0.07
0.08
0.09
71
58
66
0.01
0.02
0.01
24
31
19
8
8
8
18
18
18
22
31
45
92
93
94
10
9.9
9.7
0.05
0.07
0.10
0.47
0.56
0.47
0.07
0.08
0.10
73
58
73
0.01
0.02
0.01
16
31
16
AcA: acetaldehyde; DEE: diethyl ether.
a
◦
−1
Bed 1: ZSM-5(50), bed 2: 14 wt%CuCl2–5 wt%NaCl/␥-Al2O3; T = 275 C; GHSV = 11550 h ; 1 barg.

1
00
R. Al-Hajri, D. Chadwick / Applied Catalysis A: General 388 (2010) 96–101
Table 6
EtOH oxychlorination over ZSM-5.
a
Catalyst
Temperature
EtOH
Product selectivity, %
◦
C
X, %
C2H4
CH3Cl
AcA
VCM
EtCl
CHCl3
DEE
EDC
2
275
3
50
94
95
94
8.8
11
28
0.13
0.10
0.17
2.0
1.8
2.6
0.12
0.11
0.22
88
85
65
0.12
0.16
0.32
0.02
0.00
0.00
0.42
1.1
3.6
ZSM-5(50)
ZSM-
00
250
275
300
80
83
84
6.2
5.6
11
0.00
0.07
0.13
0.96
0.46
0.15
0.82
0.80
1.0
92
93
85
0.00
0.00
0.00
0.32
0.03
0.06
0.03
0.46
3.0
5
(280)
AcA: acetaldehyde; DEE: diethyl ether.
a
−1
Feed (vol%): 8%EtOH, 18%HCl, 31%air; GHSV = 11550 h ; 1 barg.
3
.2.3. Effects of HCl and air composition
version of less than 10%. On balance therefore, since much less EDC
than ethylene is produced, it is likely that the ethylene is produced
mainly by direct dehydration (8).
Comparing the results obtained from ZSM-5(280) and ZSM-
5(50), Table 6, we see the effect of zeolite acidity. Ethanol
conversion is higher for the more acid zeolite as expected. How-
ever, at the same time the selectivity to EtCl is lower and that
Table 5 gives the effects of HCl and air compositions in the feed
gas stream on the product distribution over ZSM-5(50) pre-bed and
1
The main products were EDC, EtCl, and ethylene. The minor by-
products were methyl chloride, CH Cl, acetaldehyde (AcA), vinyl
chloride, VCM, and DEE. In both cases, a maximum in EDC selec-
tivity (minimum EtCl) was observed indicating that an optimum
feed composition was required for efficient EDC formation. This
probably relates to the formation of the catalytically active state of
the copper in the catalyst, as evidenced by XPS studies [15]. These
◦
−1
4 wt%CuCl –5 wt%NaCl/␥-Al O at 275 C and 11550 h
GHSV.
2
2
3
3
to C H4 is higher. Again, this probably reflects the greater direct
2
ethanol dehydration activity of the more acidic zeolite, although as
noted above dehydrochlorination of the main product ethyl chlo-
ride via (4) would also be expected to be greater over ZSM-5(50).
It is also worth noting that despite the low level of EDC produc-
tion, the higher zeolite acidity favours the disproportionation of
EtCl producing EDC as expected.
results may also explain the lower EDC yield over CuCl /zeolite
reported in US patents 4,814,527 (1989) and 4,910,176 (1990)
2
[
9,10]. We believe that the high excess of air and low HCl/ethanol
ratio used was the reason why only 27% EDC selectivity was
achieved.
3.4. Dual-catalyst bed vs. physical mixture
The efficiency of the 2-bed configuration for ethanol oxy-
3.3. Reactions over ZSM-5
chlorination was compared to a physical mixture of ZSM-5(50)
and 14 wt%CuCl –5 wt%NaCl/␥-Al O catalyst. The results obtained
In order to understand the role of zeolite in the direct pro-
2
2
3
from the physical mixture are given in Table 7. The physical mixture
showed similar dependency on temperature to the dual-bed: high
duction of EDC from ethanol in the dual-catalytic bed system, the
ethanol reaction with HCl and air was studied over ZSM-5(280) and
ZSM-5(50), Table 6. For both zeolites, the main product was EtCl
with some C H and EDC. The other by-products were methane,
◦
selectivity to ethyl chloride at 250 C and high selectivity to EDC
◦
at 300 C. However, ethanol conversion and the selectivity to EDC
2
4
were always lower than achieved over the dual-catalyst bed con-
figuration for the same temperature, gas composition and GHSV. A
CH Cl (methanol hydrochlorination), acetaldehyde, AcA (ethanol
3
oxidation), VCM (EDC cracking), CHCl3 (CH Cl chlorination), and
3
◦
significant difference was the higher selectivity to VCM at 300 C
DEE (ethanol dehydration). Two main parallel reactions took place
over the zeolites: hydrochlorination of ethanol producing EtCl and
for the physical mixture. There could be several reasons for the
difference between the dual-catalyst bed and the equivalent phys-
ical mixture. The ZSM-5(50) in the physical mixture is exposed to
a significantly different gas composition compared to when it is a
pre-bed, and this may give rise to more cracking of EDC. For exam-
ple, in the separate bed configuration, the main EDC production was
over the second bed and the only available sites for cracking would
water (7), and ethanol dehydration producing C H4 and water (8).
2
Thermodynamic calculations showed that reaction (7) can proceed
to completion at the conditions used. The relative contribution of
these reactions depends on the temperature and zeolite properties.
At lower temperature the selectivity is overwhelmingly towards
ECl. Higher the reaction temperature leads to increased produc-
tion of C H . EtCl can disproportionate producing C H and EDC
be the exposed surface of the ␥-Al O which has much lower acidity
2
3
2
4
2
4
than ZSM-5(50) [17]. In the physical mixture, part of the EDC would
be produced in the early zone of the reactor, leaving it exposed to
further contact with the acid catalyst as it passed down the reactor
leading to increased cracking to VCM. This effect could be mitigated
by axial grading of the physical mixture.
according to reaction (5) and dehydrochlorinate as in (4), which is
thermodynamically favoured especially at the higher temperature.
Dehydrochlorination is known to be catalysed by acid sites [17].
However, measurement of ethyl chloride dehydrochlorination to
◦
ethylene over ZSM-5(50) at 300 C in the presence of air gave a con-
Table 7
EtOH oxychlorinationa over a physical mixture of ZSM-5(50) and 14 wt%CuCl2–5 wt%NaCl/␥-Al2O3.
Temperature
EtOH
Product selectivity, %
◦
C
X, %
C2H4
CH3Cl
AcA
VCM
EtCl
CHCl3
DEE
EDC
250
275
300
93
84
87
5.8
5.9
4.7
0.09
0.06
0.11
0.53
0.93
1.7
0.07
0.26
1.2
81
45
14
0.00
0.00
0.58
0.03
0.06
0.04
12
47
77
AcA: acetaldehyde; DEE: Diethyl ether.
a
−1
Feed (vol%): 8%EtOH, 18%HCl, 31%air; GHSV = 11550 h ; 1 barg.

R. Al-Hajri, D. Chadwick / Applied Catalysis A: General 388 (2010) 96–101
101
4
. Conclusions
References
[
1] B.K. Hodnett, Heterogeneous Catalytic Oxidation: Fundamental and Technolog-
ical Aspects of the Selective and Total Oxidation of Organic Compounds, Wiley,
We have demonstrated that
a dual-catalyst bed of zeo-
lite + oxychlorination catalyst can be used for the selective
production of ethylene dichloride from ethanol with minimum
cracking to VCM. Greater than 80% EDC yield was achieved using
a ZSM-5 pre-bed with ethyl chloride and ethylene as the main
by-products. An optimum feed composition of HCl and air was
required to activate the oxychlorination catalyst and maximize
the EDC yield. The dual-bed configuration gave better performance
than the equivalent physical mixture. It was shown that EDC was
mainly produced by direct hydrochlorination of ethanol to ethyl
chloride followed by the oxychlorination and disproportionation of
ethyl chloride. Ethanol dehydration followed by ethylene oxychlo-
rination playing the minor role in the temperature range studied.
The results open the possibility of a single-stage process from bio-
derived ethanol to EDC.
2
000.
[2] A. Demirbas, Energy Sources, Part A: Recovery, Utilization, and Environmental
Effects 28 (2006) 955–964.
[
3] C. Cardona, J. Quintero, I. Paz, Bioresource Technology 101 (2010) 4754–
766.
[4] K. Fang, D. Li, M. Lin, M. Xiang, W. Wei, Y. Sun, Catalysis Today 147 (2009)
33–138.
5] X. Zhang, Z. Li, Q. Guo, H. Zheng, K. Xie, Fuel Processing Technology 91 (2010)
79–382.
4
1
[
3
[6] V. Subramani, S. Gangwal, Energy & Fuels 22 (2008) 814–839.
[7] M. Bruscino, Hydrocarbon Processing (August) (2010) 65.
8] H.A. Cheney, US patent 2,442,285 (1948).
9] R.W. Diesen, US patent 4,814,527 (1989).
[
[
[
10] R.W. Diesen, US patent 4,910,176 (1990).
[11] T.M. Nguyen, R.L.V. Mao, Applied Catalysis
29.
12] C. Phillips, R. Datta, Industrial and Engineering Chemistry Research 36 (1997)
466–4475.
13] I. Takahara, M. Saito, M. Inaba, K. Murata, Catalysis Letters 105 (2005) 249–
52.
14] X. Zhang, R. Wang, X. Fang, F. Zhang, Microporous & Mesoporous Materials 116
2008) 210–215.
[15] P. Prasad, K. Prasad, P. Rao, V. Kaushik, Journal of Materials Science 32 (1997)
479–1482.
A
61 (1990) 119–
1
[
[
[
4
2
Acknowledgments
(
We thank DTI(UK) and Ineos Technology for financial support
under contract TP/16307, and in particular Dr. Andrea Marsella of
Ineos Vinyls for general advice on oxychlorination. We are grateful
to Dr. Sami A.I. Barri for advice and help with XRD, and Dr. Laura
Torrente Murciano for help with the equilibrium calculations.
1
[
16] J.W.S. Charles, E. Wilkes, C.A. Daniels (Eds.), PVC Handbook, Hanser Gardner
Publications, 2005.
[17] D. Carmello, E. Finocchio, A. Marsella, B. Cremaschi, G. Leofanti, M. Padovan,
Journal of Catalysis 191 (2000) 354–363.