Indi an Journ al of C hemistry
Vol. 38 B. October 1999 ; pp. 11 89- 11 93
Propionylation of anisole to 4-methoxypropiophenone over zeolite H-beta
S Sugunan* , Bindhu Jacob & Binoy Jose
Dc partme nt of Applied C hemi stry , Cochin University of Science and Technology, Cochin 682 022, India
Received II Ma y' 1999; accepted (revised) 18 August 1999
The rcs ult s of a detailed stud y o f the propionylation o f anisole over vari ous medium and large pore zeolites such as HZS M-). H-hcta. H-Na-beta, H-mo rdcnite, H- Y and H-RE-Y are presented and discussed. In addition , homogenous catalysts
:lI1d amorp holls SiO, -AI , O \ are also in cluded for co mpari son. The catalyst and process parameters are optimised to enhance
th e con\c rsioll of pro pion yl chl o ride(PC) and selectivity to 4-methoxypropiophenone(4-MOPP).
Me th oxy pro piophenon es are found to have wide
applications in th e area of fine chemical synthesis.
They are usuall y pre pared by the Friedel-Crafts
acylation o f aniso le with propionyl c hloride/propionic
anh ydride usin g A IC l1 catalystt .2.:l . The use of various
6
5
types o f ca tal ysts like Z nCI 2 , FeCI / · , H, P0 4 , and
7
co balt ( II ) chloride have been repo rted recently in the
liquid phase pro pi o ny lat io n of anisole. Zeolites due to
th e ir shape-selectivity , th e rmos tability, ease of
sep:t rati o n fro m the produ cts and the regeneration of
th e deacti va ted catal ysts, ha ve been widely used in
th e field o r pe troc hemistry. However, the use of
zeo lite catal ys ts in fin e organic synthesis and
parti c ularl y in th e acylati on and alkylation reaction s
o f aro matic s is limit ed.
He re in we re po rt th e results obtained in the
pro pion y lat io n of a ni so le unde r various reaction
co nditi o ns a nd o n the effects of some catalyst
va riables o n ca tal ys t pe rformance. The results
obtai ned over zeo lit e H-beta are also compared with
the Lewis acid catal yst, AIC I,.
Expe rimental Section
Ze o l ites Na- Y and H- morde nile were o btained
fro m Laporte In o rgani cs. Ches hire, UK Zeolites
ZSM-5 and be ta we re prepared using the methods
described in the lite rature K,,!. The sy nthesized zeoli tes
were was hed wi th deionised water, dried and calcined
at I ~ K for 16 hI' in th e presence of air to e limjnate
the o rganic templates from the zeo li te channe ls. The
resultant samples were N H/ -exchanged three ti mes
using the fo ll ow ing cond iti ons: 10 mL NH 4NO]
( I M)/g zeo lit e. ~53 K. 8 hr exchanged lun, pH 7-8 .
Thc N H/ -cx c h<.tn ged sdmples were aga in calcined at
823 K for 8 hr to get the ir protonic forms. Naexchanged beta samples were prepared by treating
fresh H-beta with 100 mL aliquots of O.IM and 1M
aqueous solutions of NaNO-, by following the above
exchange conditions.
The
H.RE(42.2)Y
and
H .RE(70.6) Y were prepared by treating NH 4 - Y with
5% rare earth chloride solution.
The Si0 2/AhO, ratio of various zeolites and degree
of ion-exc hange were carried out by a combination of
wet and atomic absorption me thods (Hitachi 800).
The surface area of the catalysts was measured by the
nitrogen BET method us ing an Omnisorb 100 CX
apparatus. X-ray powder diffraction (X RD) was
carried out on a Rigaku , D-Max/fII-VC model using
the CuKx radi ation and was used to evaluate the peak
positions of various zeolite samples . The ac i dity of
the various zeo lites were dete rrrilned using
.
f
. 10- 12 ,
temperature programmed d esorptlon 0 ammOllla
The size and morphology of the zeolite catalysts were
est imated
by
scanning
e lectron
microscope
(Cambridge Ste reoscan 400).
The acylat ion of an iso le was carried out in liquid
ph ase at 343 K under atmospheric pressure. In a
typical run, appropri ate a mounts of ani sole and
propionyl chloride (5: )) molar ratio was ch arged in
the batch reactor along with 0.3 g catalyst. Samples
were withdrawn periodicall y and analyzed with a gas
ch romatograph. The percentage conversion (wt. %) of
propionyl ch loride (PC) is defined as the total
pe rcentage of PC tran sformed . T he main products
obtained we re 4-methoxypropiophenone(4-MOPP)
and 2-meth oxypropiophenone(2-MOPP) along with
some amount of other consecutive products
(Scheme I ).
1190
IND IA N J C HEM, SEC B, OCTOBER 1999
OMe
-
H-beta
Liquid phase, 2 h
G-COCH,CH,
(2-MOPP = '11.88 wt.%)
(4-MOPP = 85.37 wt.%)
+
Others
(2.74 wt.%)
Scheme I
Table I-Propionylation of anisole'
Catalyst
Reaction
time (h)
Conversion h of
PC (wt%)
Rate of PC _____ ~~()_~~~l c!~st!!_~~j_'~I!j ~c~)~___
4-MOPP
conversion
2-MOPP
Others
(mmol g- Ih- I)
H-ZSM-5
2
62.02
19.10
83.45
15 .55
0.99
H-heta
2
69.76
21.48
85.37
11 .88
2.74
H-Na (13 .6) beta"
2
63 .64
19.60
75 .07
17.27
7.65
H-Na (37.3 ) beta"
2
48.39
14.90
55.73
30.48
13 .78
H-mordenite
2
57.15
17.60
78 .20
20.02
1.78
H-Y
2
58.66
18.07
67.56
24.76
7.58
H-RE (422 )y l
H-RE (70.6)y r
2
59.81
18.42
68.2 1
26.62
5.27
2
65.32
20.11
58.03
30.70
11 .27
AIC I,
2
82.93
25.54
59.7
22.07
18.23
Si0 2-A I20 , (amorphous)
2
47.47
14.62
64.88
3 1.35
3.76
• Reactio n cond iti on s: catalys t (g) = 0.3 ; catalyst / C 2 H5COCI (wt./wt.) = 0.17; anisole / C 2 HsCOCI (molar ratio)
(K) = 343
h PC == propio nyl chloride (C 2 HsCOCI)
(" Rat e of PC co nversio n (mmol g- Ih- I) = (amount of PC reacted)/(weight of catalyst x reac ti on time)
d 4-MOPP = 4-meth oxypropiop henone; 2-MOPP = 2-methoxypropiophenone others = consecutive products
(" Values in parenthesis represents the percent age of Na exchanged in the H-beta
3
f Values in parenthesis rep resen ts the percentage of RE+ -exchanged in zeolite H- Y
The rate of PC conversion (mmol g- 'h- ') was
calculated as the amount of PC (m mole) converted
per hour per g of the catalyst. The selectivity for a
product is ex pressed as the % of the particular
product formed .
Results and Discussion
T he co nversion of PC(wt. %), rate of PC conversion
(mmolg- 1h- l ) and the product di stribution (wt.%) of
the products, 4-met hoxypropiophenone and 2meth oxy-prop iophenone obtained over various zeoli te
catalysts are li sted in Table I. Among various zeolite
catalysts, H-beta catalyzes the reaction efficiently and
selecti ve ly to 4-M OPP and it is found to be superior
to ot her zeolite catalysts and AICI 3 . The conversion of
PC, rate of PC conversion and selectivity for the
majo r product, 4-MOPP over zeolite H-beta after 2 hr
= 5; reaction temperature
of reaction time were found to be 69.76 wt. %, 21.48
mmol g- Ih- I, 85 .37 wt. % respecti vely. The highest
ac tivity of H-beta may be attributed to its stron ger
ac id sites and th e space avail able in th e 12-membered
three dimensional pore sys tem (5.4x5.6 and 5.lx5.5).
AICI , gave hi gher amounts of consecutive products
due to its non-shape select ive character.
The convers ion of PC over H-Y, H-RE(42 .2)-Y and
H-RE(70.6)- Yare found to be 58.66 wt. %, 59.8 1
wt. % and 65 .32 wt. % respectively . The enhancement
in catalyti c ac ti vit y may be du e to the increase in
strength of acid sites due to RE-cat ion exc hange".
The activity of zeo lite H-beta in the propionylation
reaction decreases drastically with the increase in Na +
content in H-beta . This may be due to the removal of
some amount of stronger Brbnsted aci d sites by Na +
exc hange in H-beta . A blank run carried out at the
1191
SUGUNAN et at. : PROPIONYLATION OF ANISOI .F TO 4-METHOXYPROPIOPHENONE
l00~--------------------------~
• Conv. of PC(v..(04
ORate of PC
conv.(11'111JIIg'h)
.4-MCPP
~2-MCPP
• Others
343
373
363
353
Peoc1ia1 taTlJ· (I<)
Figure I-Influence of reaction temperature on the conversion of PC (wt. %); rate of PC conversion
(m mols g-I h- I) and product distribution (over H-beta)
t>
Table II-Influence of SiOi AI 20 3 ratio of zeolite H-beta"
Si0 2/AI 20 3 (molar ratio)
26
50
80
2
2
2
Conversion of PC (wt. %)h
69.76
23.25
18. 11
Rale of PC conversion (mmol g- Ih- I)"
21.48
7.16
5.57
Reaction time (hr)
Product distribution (wt. %)
85 .37
82.07
84.93
2-MOP.P
11.88
12.95
6.98
2.74
4.98
8.09
a,b,c & d see footnotes to Table I
same reacti on conditions in the absence of any
catalyst gave a PC conversion of 19.65 wt.%.
A significant increase in the rate of PC conversion
is achieved with the increase in the reaction
temperature from 343 K to 373 K. However, the
product distribution is not significantly influenced.
The selectivity toward s 4-MOPP remains more or less
co nstant in the ran ge of temperature studied (Figure
I).
Table II shows the effect of Si02/AI 20 3 molar
ratio ~f zeolite H-beta in the propionylation of
anisole. The conversion of PC is found to decrease
from 69.76 wt. % to 18.11 wt. % with increase in
Si0 2/AI 20 , mo lar ratio from 26 to 80.
The e ffec t o f cataly st concentration (cat/PC ratio)
in the ran ge o f 0.05 to 0.41 g/mole of PC on the
conversion of PC is studied at 343 K for 2 hr of
reaction ove r zeolite H-beta catalyst. When the
100
...a0.
'0
ern(/?
~~
o .........
60
CLE·c
40
a(/)
e .aU
...
20
>
e
a
0
0
(/)
_ _I
:/"/:
80
e
-
~.Q
0~
4-MOPP
Others
:J
'0
.X:
Q)
0
2
•
•
4
•
6
8
ArisoleIPC (rrolar ratio)
Figure 2-E lleCI of ani sole PC mol ar ralio on the co nversion of
PC ( . ) and produ ct di stribution (Over zeolite H-beta). 4-MOPP
( . ). 2-MOppr.& ) and others (*) ; Reaction conditions: See
footnotes to Table. I; Reaction time = 2 hr
catalyst to PC ratio is increased from 0.05 to 0.41 , the
conversion of PC is also found to increase from 50 .20
wt. % to 64.15 wt. % (Table III) . Furthermore, it is
observed that, the selectivity of the major product, 4MOPP is found to be relatively little affected by the
increase in catalyst concentration. The increase in
selectivity of 2-MOPP can be explained on the basis
of shape selective behaviour of H-beta.
Figure II shows the effect of varying the
anisolelPC molar ratio in the reaction mixture on the
activity of H-beta and product distribution at a fixed
anisole concentration. An increase in both the
1192
INDIAN J CHEM, SEC B, OCTOBER 1999
... ................
........................
-
............. . . ......•.... .......•.
_......_.._..
__
_
_
... •...... ........ ...... ......••. ••
_..
_-_..._...._._.........................................._ ___._
.. .. ..
.....- ..
Table Ill-Effect of catalyst (H-beta) concentration a
Catal yst/PC
Convertion ~ of PC
(wt.lwl. )
(wt %)
Rate of PC conversion
(mmol g-Ih- I)
••• •• •••• • •• • •••• __
Product
distribution(wt%)d
__ ·_···__··H.·_H·__._ ·_
········___ _ _ _ __
4-MOPP
2-MOPP
others
0 .05
50.20
46.38
87.23
8.13
4 .64
0.17
69.76
21.48
85.37
11.88
2.74
0.29
65.32
12.07
76.05
13.48
10.46
0.41
64.15
8.46
74.80
19.12
6.08
a,b.c & d see fo o t notes to Table I; reaction time = 2 hr
-
_
_- ............................ ....._----_._- -_..•.._ - - -
• ••••••••••••• _ _ _ _ .H •• • _ . _ . . .. . . _ _ _ .H . . . . . . . . . . . . . . . . . . . . . . . .. . .. . . . . _ _ _ _ • _ _ _ •• _ _ H • •••• _
....
. ........... _ . _ _ • _ _ _ _ •_ _ _ _ _ _ _ _
_ _ __ _ _
Table IV-Recycling of H-beta
Run
h
•• _
•• _ _ ._H ••• _ _ ...... _
_ _ •• _ _ •• • •
a
Change in
Conversion of
Rate of PC" cony.
SiOz/AI 20 1
(molar ratio)
PC (wI. %)
(mmol g-Ih- ' )
4-MOPP
2-MOPP
Others
crystallinity
ofH-beta
26.0
68 .73
21.16
68.85
23.58
7 .57
100
2
29.56
41.32
12.72
61.03
29. 5 1
9.46
79.1
]
3 1. 38
29.89
9.2
58.72
31.43
9.85
75.3
Product distri bution (wt%)d
• • • ••••• .......... •••• •••••••• H· •• _ . _ _ . . . . . . .... _
I (parent catalyst )
a,b ,c & d see foot notes to Table I ; reaction time
. . . .. .. .. . . . .. . . . . . . . . . . .. _
•••• • H ••• H ...... _ . _ _ . . . . . _
%
. . . . . _ H • ••••••• • • •
=2
•• ••• •• •••• • •• ••• •• •••••••• •• •••••• •• ••••••••• •• • • •• • ••••••••••• • ••••••••••••••••••• : •••••••• :. ••••••••• ••• •• ••••••• ••••••••••••••••••••••• ••• ••• •••••••• • ••••••••• • ••• 0 0
b
..,
.
c
c:
50
29, Digr ••
Figure 3-X . ray diffraction patt erns of (a ) fresh H·beta and (b)
H· oeta aft cr recyc lin g
conversion of PC and se lectivity of 4-MOPP is
observed with increase in anisole/PC molar ratio. The
convers ion of PC at I, 3, 5 and 7 molar ratios of
an isole to PC was found to be 15 .50 wt. %, 31.14
wt. %, 69.76 wt. % and 71 .66 wt. % respectively.
Table IV depicts the recycling of zeolite H-beta in
the propionylation of an isole . The used catalyst is
activated eac h time at 773 K in the presence of air
and characterized for its chemical composi ti on and
cry stallinity (Figure III). A decline in the propionyl
chloride convers ion was observed after each reuse. It
has been presumed that the decrease in catalytic
• • ••• •• • • • •••••••• •• • • • • • •
• • • _ _ _ • • • • ••• ••••••••_
_
••••• •••••• • ••• • • • • • • • • • • • •_ _
•
__
. - • • • • • • • • • • • • • • • •- -
- - --
actIvIty is probably due to the dealumination of the
zeolite framework by HC!, which is formed as a byproduct during the reaction .
The formation of methoxypropiophenone is
exp lained by an e lectrophilic attack of the propionyl
cation (C 2H sCO+) on the anisole ring whose
formation is facilitated by the stronger acid sites of
the catalys{1.
In summary, zeolite catalysts can catalyze the
propiony lation
of
anisole
to
methoxy
propiophenones . H-beta is found to be a more active
catalyst than the other zeolites and it showed a better
selectivity in the reaction than the conventional Lewis
acid catalyst AICI,. The catalysts used in thi s study
could be arranged in the decreasing order of PC
conversion (mmol g - I h- I) as follows:
AICI , > H-bet a > H-RE(70.6)-Y > H-Na( 13.6)-beta >
H-ZSM-5 > H-RE(42 .2) .. Y > H- Y > H-mordenite >
H-Na(37.3)-beta > SiO r AI20 , (amorphous).
The yield of the product decreases wi th an increase
in Si0 2-AI 20 , ratio of H-beta. A higher yield of
methoxypropiophenone is obtained by increasing the
reaction temperature, catal yst concentration and
molar ratios of ani sole to propionyl chloride.
References
I
Bindhu Jacoo . Sug unan S & An and P Si ng h, J Mol Calal A
C/II'lIIim /, I ] 'J . 1999. 4 .1 and re ference s cit ed therein.
2
Sing h A P. Jacoh R . .Li co h 13i ndhu & Sugunan S, J Appl
Co w l. A Gel/ eral. 174, 199X, 51 and re ferences ci ted therein .
~
SUGUNAN el al. : PROPIONYLATION OF ANISOLE TO 4-METHOXYPROPIOPHENONE
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