Friedel-Crafts alkylation of diphenyl oxide with benzyl chloride over sulphated zirconia

Article abstract of DOI:10.1021/op990099y

Friedel-Crafts reactions are ubiquitous in fine chemicals, intermediate, and petrochemical industries. In most of the cases very high yield and selectivities can be achieved with aluminium chloride as catalyst with nitrobenzene as a solvent. However, environmental concerns associated with aluminium chloride-nitrobenzene or BF₃-HF or mineral acids catalysts have encouraged process changes and the development of solid acid-based Friedel-Crafts reactions which are economically viable as well. This contribution deals with the alkylation of diphenyl oxide with benzyl chloride using sulphated zirconia as solid acid catalyst, which gives excellent conversions of the product benzyldiphenyl oxide. The effects of a variety of parameters were studied in a batch reactor to establish the kinetics and mechanism of the reaction at 90°C. The reaction obeys the Langmuir-Hinshelwood-Hougen-Watson mechanism involving weak adsorption of the reactants, and the reaction is intrinsically kinetically controlled.

Full text of DOI:10.1021/op990099y

Organic Process Research & Development 2002, 6, 256−262
Friedel-Crafts Alkylation of Diphenyl Oxide with Benzyl Chloride over
Sulphated Zirconia
,†
G. D. Yadav* and Sonali Sengupta
Department of Chemical Engineering, UniVersity Institute of Chemical Technology (UICT), UniVersity of Mumbai,
Matunga, Mumbai - 400019 India
importance,6
-16
for instance, condensation, esterification,
Abstract:
Friedel-Crafts reactions are ubiquitous in fine chemicals,
intermediate, and petrochemical industries. In most of the cases
very high yield and selectivities can be achieved with aluminium
chloride as catalyst with nitrobenzene as a solvent. However,
environmental concerns associated with aluminium chloride-
alkylation, etherification, acylation, isomerisation, and nitra-
tion. Due to its low cost, high thermal stability, and
superacidity in certain reactions, S-ZrO possesses distinct
2
advantages over many solid acids. It is reusable and can be
used in powder form and pelletised form.
The alkylation of diphenyl oxide (DPO) with a number
of olefins, alcohols, and benzyl chloride leads to com-
mercially important products, for instance, heat transfer fluids
and perfumery compounds. Particularly the alkylation of
diphenyl oxide with benzyl chloride has not been reported
in the literature, and the alkylated product has potential uses
as a heat-transfer fluid among others. Thus, it was thought
worthwhile to study systematically the Friedel-Crafts alky-
lation of diphenyl oxide with benzene chloride (using
sulphated zirconia as a catalyst) including kinetics and
mechanism.
nitrobenzene or BF
3
-HF or mineral acids catalysts have
encouraged process changes and the development of solid acid-
based Friedel-Crafts reactions which are economically viable
as well. This contribution deals with the alkylation of diphenyl
oxide with benzyl chloride using sulphated zirconia as solid acid
catalyst, which gives excellent conversions of the product benzyl-
diphenyl oxide. The effects of a variety of parameters were
studied in a batch reactor to establish the kinetics and
mechanism of the reaction at 90 °C. The reaction obeys the
Langmuir-Hinshelwood-Hougen-Watson mechanism involv-
ing weak adsorption of the reactants, and the reaction is
intrinsically kinetically controlled.
Experimental Section
Experimental Setup and Methodology. A 100-mL glass
reactor (internal diameter 5 cm and height 10 cm) which
was fully baffled was employed. It was provided with a six-
bladed turbine impeller located at 0.5 cm from the bottom
of the reactor and a reflux condenser. The desired speed of
agitation of the reaction mixture was achieved by controlling
the speed of stirrer motor with a regulator. An electrically
heated oil bath was used to heat the reactor. The temperature
of the bath was maintained by using a temperature controller.
Standard experiments were carried out by using 0.07 mol of
Introduction
The use of acid catalysts is very widespread in the
chemical and allied industries, and the highly corrosive,
hazardous, and polluting liquid acids employed by those
technologies are being replaced with solid acids, for instance,
acid-treated clays, zeolites, ion-exchange resins, and a variety
of metal oxides. Of late, a number of organic syntheses are
conducted with solid acids, leading to better regio- and
stereoselectivity. Not only the strength of the acid but also
the type of acidity (Brønsted or Lewis) are factors for
obtaining enhanced activity and selectivity. The incorporation
of superacidity in solid acids has attracted considerable
diphenyl oxide (11.9 g) and 0.01 mol of benzyl chloride
3
(
(
1.265 g). A catalyst loading of 50 kg/m of total reactants
0.064 g) was used. The liquid-phase volume was 12.8 mL.
The reactions were carried out at 90 °C for 1 h. A speed of
agitation of 20 rps rpm was employed for the reaction.
Samples were collected periodically.
Analytical Method. The samples were analysed by gas
chromatography (Chemito 8510 model with a flame ionisa-
tion detector). A 2 m × 3.2 mm internal diameter stainless
steel column packed with Chromosorb WHP impregnated
with 10% SE-30 was used for analysis. Synthetic mixtures
2
attention. Among solid acids, sulphated zirconia (S-ZrO )
has found several applications,1 and we have observed that
-7
it holds great promise in a number of reactions of industrial
*
To whom correspondence should be addressed. E-mail: gdyadav@yahoo.com.
Telephone: 91-21-410-2121. Fax: 91-22-4145614.
†
Current address: Johansen-Crosby Visiting Professor of Chemical Engineer-
ing, Department of Chemical Engineering and Material Science, Michigan State
University, East Lansing, MI 48824. Telephone: 517-355-9291. Fax: 517-432-
1
105. E-mail: yadavg@egr.msu.edu.
(
(
1) Yamaguchi, T.; Tanabe, K. Mater. Chem. Phys. 1986, 16, 67.
2) Tanabe, K. In Catalysis: Science and Technology; Boudart, M., Anderson,
J., Eds.; Springer-Verlag: New York, 1981.
(8) Yadav, G. D.; Nair, J. J. Chem. Commun. 1998, 2370.
(9) Yadav, G. D.; Thorat, T. S. Ind. Eng. Chem. Res. 1996, 35, 721.
(10) Yadav, G. D.; Kirthivasan, N. Chem. Commun. 1995, 203.
(11) Yadav, G. D.; Nair, J. J. Catal. Lett. 1999, 62, 49.
(12) Yadav. G. D.; Pujari. A. A. Green Chem. 1999, 1, 6.
(13) Yadav, G. D.; Krishnan, M. S. Chem. Eng. Sci. 1999, 54, 4189.
(14) Yadav, G. D.; Pujari, A. A. Can. J. Chem. Eng. 1999, 77, 489.
(15) Yadav G. D.; Ramesh, P. Can. J. Chem. Eng. 2000, 78, 917.
(16) Yadav, G. D.; Kundu, B. Can. J. Chem. Eng. 2001, 79, 805.
(
(
(
(
3) Tanabe, K.; Hattori, H.; Yamaguchi, T. Crit. ReV. Surf. Chem. 1990, 1, 1.
4) Kumbhar, P. S.; Yadav. G. D. Chem. Eng. Sci. 1989, 44, 2535.
5) Song, X.; Sayari A. Catal. ReV. Sci. 1996, 38, 329.
6) Kumbhar, P. S.; Yadav, V. M.; Yadav, G. D. In Chemically Modified Oxide
Surfaces; Layden, D. E., Ed.; Gordon and Breach: New York, 1989.
7) Yadav, G. D.; Nair, J. J. Microporous Mesoporous Mater. 1999, 33, 1.
(
2
56
•
Vol. 6, No. 3, 2002 / Organic Process Research & Development
10.1021/op990099y CCC: $22.00 © 2002 American Chemical Society
Published on Web 04/05/2002

of the authentic components were used for calibration and
quantification of the data.
Reagents. Diphenyl oxide was obtained from Hardillia
Chemicals Ltd., Mumbai, India. Benzyl chloride was pro-
cured from M/s s.d.Fine Chemicals Pvt. Ltd., Mumbai, India.
Zirconium oxychloride octahydrate (ZrOCl
2 2
‚8H O) of AR
grade was obtained from M/s. Loba Chemie, Mumbai, India.
Sulphuric acid of AR grade, used as sulphating agent, and
ammonia solution, used for the preparation of zirconium
hydroxide, were obtained from M/s s.d. Fine Chemicals Ltd.,
Mumbai, India.
Preparation of the Catalyst. Sulphated zirconia was
4
,6,7
prepared by a process developed in this laboratory.
A
known amount of zirconium oxychloride was dissolved in
deionised water and filtered. The filtrate and aqueous
ammonia solution were placed into two different separating
funnels and were simultaneously added to a beaker, at
controlled flow rates under constant stirring, while maintain-
ing the pH of the mixture solution at ∼9-10. By this process,
4
a white zirconium hydroxide [Zr(OH) ] precipitate was
obtained. After the precipitation was complete, it was kept
for 1 h for digestion and filtered. The solids were washed
with deionised water until no ammonia and chloride ions
were detected in the washings, the absence of which was
confirmed through the phenolphthalein and silver nitrate tests,
respectively. The white precipitate of zirconium hydroxide
was then dried in an oven at 393 K for 24 h. The dried cake
was crushed to small particles. Sulphation of this hydrous
Figure 1. Reaction scheme for the reaction between diphenyl
oxide with benzyl chloride over sulphated zirconia catalyst.
2 4
zirconia was done by percolating 1 N H SO solution through
3
it, taken as 15 cm /g of solids. The sulphated zirconium
hydroxide was then calcined in air at 923 K for 3 h to obtain
the final catalyst. The Hammet acidity function H
0
of
sulphated zirconia is -16.0, and it is a known solid superacid
7
6
with both Brønsted and Lewis acidity. The surface area of
the catalyst is 102 m /g.
2
Results and Discussion
Reaction Chemistry. The Friedel-Crafts alkylation of
diphenyl oxide (B) with benzyl chloride (A) in the presence
of sulphated zirconia catalyst leads to the formation of an
isomeric mixture of benzyl-diphenyl oxide (MW 260) which
was confirmed through GC-MS and FTIR. The reaction
scheme is shown in Figure 1 In the presence of S-ZrO
2
catalyst, benzyl chloride is protonated, and the benzyl
carbenium ion or carbocation so formed then combines with
diphenyl oxide in the ortho or para position to give an
isomeric mixture as the product (Figure 2).
Effect of HCl Acid Generated in Situ. The HCl
generated in situ is desorbed from the reaction mixture at
the reaction temperature, and any small quantity of dissolved
Figure 2. Mechanism of the reaction between benzyl chloride
with diphenyl oxide over sulphated zirconia.
4
,6
HCl does not catalyse these types of reactions. In the
current study, nitrogen was purged continuously through the
mixture with the result that there was no effect on the
conversion of benzyl chloride at 90 °C. HCl has poor
solubility in the reaction mixture at higher temperatures, and
any trace amount left is not sufficient to produce any reaction.
A standard experiment was done wherein the reaction was
started with only DPO and benzyl chloride under otherwise
identical conditions at 90 °C. A sample after 2 h did not
show any conversion of benzyl chloride. The catalyst was
then added, the reaction was continued with the result that
the reaction had proceed smoothly, and within 10 min there
was a conversion of 29.5% of benzyl chloride. This was in
conformity with the usual experiment. Then 2 mL of sample
was pipetted out carefully without any catalyst particles in
it, this solution was placed in a test tube to which a specially
Vol. 6, No. 3, 2002 / Organic Process Research & Development
•
257

necked condenser was attached, and the assembly was placed
in the oil bath at the same temperature. Simultaneously the
reaction was continued in the reactor, and sampling was done
after 10 min. The test tube liquid and the reaction mixture
were analysed to find that the test tube sample had the same
composition as in the beginning, whereas the sample from
the reactor showed a conversion of 48.2%, which was little
more than the standard experiment. This suggested that the
reaction between DPO and benzyl chloride did not proceed
without sulphated zirconia whose loading per unit volume
of liquid phase had increased due to withdrawal of a large
sample. Thus, it was concluded that this was a true
heterogeneous reaction and also that HCl did not catalyse
the reaction.
Effect of External Mass Transfer. This is a typical
solid-liquid slurry reaction involving the transfer of benzyl
chloride (A) and diphenyl oxide (B) to the catalyst wherein
external mass transfer of reactants to the surface of the
catalyst particle, followed by intraparticle diffusion, adsorp-
tion, surface reactions, and desorption, takes place. The
influence of external solid-liquid mass-transfer resistance
must be ascertained before a true kinetic model could be
Figure 3. Effect of speed of agitation on conversion of benzyl
chloride.
The observed rate robs could be given by three types of
models wherein the contribution of intraparticle diffusion
resistance could be accounted for by incorporating the
effectiveness factor, η. These models are (a) the power-law
model if there is very weak adsorption of reactant species,
4
developed. Thus, experimental and theoretical analyses were
done.
The reaction studied in this case involves two reactants
in organic phase, which react on the surface of the catalyst
to form liquid-phase (organic) products at the reaction
temperature chosen. The overall reaction can be presented
as follows:
(b) the Langmuir-Hinshelwood-Hougen-Watson model,
and (c) the Eley-Rideal model.
Since diphenyl oxide (B) was used in large excess over
benzyl chloride (A), there was a chance of external resistance
for the transfer of benzyl chloride from the bulk liquid phase
to the external surface of the catalyst particle. Therefore, the
speed of agitation was varied under otherwise identical
condition for a particle size of <90 µm. The effect of speed
A + zB f D + E
(1)
where A and B are the reactants and D and E are the
products. z is the stoichiometric coefficient of B.
At steady state, the rate of mass transfer per unit volume
-
3
-1
3
of the liquid phase (kmol‚m ‚s ) is given by:
of agitation was studied at a catalyst loading of 50 kg/m at
9
0 °C over the range of 10-25 rps. Figure 3 shows the
RA ) kSL-Aa {[A ] - [A ]}
(2)
p
0
s
conversion of benzyl chloride with time. It is seen that the
conversion remains practically the same at and beyond a
speed of 16.67 rps, which indicates the absence of external
solid-liquid mass-transfer resistance. Theoretical analysis
was also be done to ensure that the external mass-transfer
resistance was indeed absent as delineated below.
The liquid-phase diffusivity values DAB (benzyl chloride
in diphenyl oxide) and DBA(diphenyl oxide in benzyl
chloride) were calculated by using the Wilke-Chang equa-
(
rate of transfer of A from bulk liquid to external
surface of the catalyst particle)
zkSL-Ba {[B ] - [B ]} (3)
)
p
0
s
(
rate of transfer of B from the bulk liquid phase to the external
surface of the catalyst particle)
)
)
robs
(4)
1
7
tion. The values obtained at 90 °C are as follows:
rate of reaction within the catalyst particle.
-
9
2
Equation 4 could be represented by a Langmuir-
DAB ) 2.388 × 10 m /s
Hinshelwood-Hougen-Watson-type or power law model
with or without the effectiveness factor, η, to account for
the intraparticle diffusion resistance.
-
9
2
DBA ) 2.7877 × 10 m /s.
The average particle size used in all experiments was 46.8
µm which was measured by an image analyser (Tracor
Northern 8500, U.S.A.). Thus, the particle surface area per
Depending on the relative magnitudes of external resis-
tance to mass transfer and reaction rates, different controlling
4
mechanisms were put forward. When the external mass-
unit liquid volume could be calculated from a
p
) 6w/F
p p
d
)
transfer resistance is small, then the following inequality
holds,
-
1
3
as 1203 m [where w ) 50 kg/m of solid loading, F
p
3
5
p
330 kg/m , d ) 46.8 µm].
1
robs
1
1
>
>
and
(5)
(17) Reid, R. C.; Prausnitz, M. J.; Sherwood, T. K. The Properties of Gases
and Liquids, 3rd ed.; McGraw-Hill: New York, 1977.
kSL-Aa [A ]
kSL-Ba [B ]
p
0
p
0
258
•
Vol. 6, No. 3, 2002 / Organic Process Research & Development

intrinsically kinetically controlled. This was further con-
firmed by invoking the Wiesz-Prater criterion.18
According to the Wiesz-Prater criterion if
2
(
i) Cwp ) -robsFpR /D C .1
e
AS
then the reaction is limited by severe internal diffusion
resistance,
(ii) Cwp , 1
then the reaction is surface-reaction controlled.
In the present case, the observed value of Cwp ) 0.072,
and the reaction is surface-reaction controlled.
A further proof of the absence of the intraparticle-diffusion
resistance was obtained through the study of the effect of
temperature, and it will be discussed later.
Figure 4. Effect of particle size on conversion of benzyl
chloride.
Since both internal and external mass-transfer resistances
were absent, further development was done by considering
the adsorption, surface reaction, and desorption steps.
Development of Mechanistic Model and Kinetics of the
Reaction. In the case of present studies, it is essential to
understand the reaction mechanism to develop a suitable
model. The initial rate data could be analysed on the basis
of Langmuir-Hinshelwood-Hougen-Watson (LHHW) or
Eley-Rideal mechanisms. For initial rate data, the following
Thus, the contribution of external mass-transfer coefficient
could be calculated. The solid-liquid mass-transfer coef-
ficients for A and B, given as kSL-A and kSL-B, respectively,
were determined by the Sherwood number correlation. To
be on the safe side, the limiting value of the Sherwood
number was taken as 2. The actual value is far greater than
2
due to intense agitation.
Thus, from the Sherwood number, Sh ) kSL
solid-liquid mass-transfer coefficients for A and B are
calculated as:
d
p
/D the
9
analysis is most appropriate. The mechanism as shown in
Figure 2 can be used to arrive at the LHHW type of
mechanism.
1
. Adsorption of benzyl chloride (A) on a vacant site S
-
4
-4
kSL-A ) 1.02 × 10 m/s and kSL-B ) 1.19 × 10 m/s
is given by:
Substituting these values in eq 5,
KA
A + S [
\
] AS
(a)
1
3
)
10.4 m s/kmol
Similarly adsorption of diphenyl oxide (B) on a vacant site
S is represented by:
kSL-Aa [A ]
p
0
and
KB
B + S [
\
] BS
(b)
1
3
)
)
1.27 m s/kmol
2
. Surface reaction of AS with BS, in the vicinity of the
site, leading to formation of benzyl diphenyl oxide (ES) on
the site.
kSL-Ba [B ]
p
0
1
robs
3
3
3.71 × 10 m s/kmol
K2
AS + BS [
\
] ES + WS
(c)
From these values it is clear that the conditions given by eq
are satisfied. That is, the rate of solid-liquid mass transfer
5
Desorption of benzyl diphenyl oxide (ES), and HCl (WS)
is much higher than the observed rate of the reaction, and it
can be said that the reaction is either surface-reaction
controlled or intraparticle-diffusion controlled. Thus, the
effects of particle size were studied to find out which of the
two was controlling. Further experiments were conducted
at 20 rps to avoid attrition of the catalyst at higher speeds.
Effect of Particle Size. The particles of the catalyst were
crushed and sieved. The effect of particle size was studied
in the ranges 53-74, 74-88, 105-149, and 210-250 µm
under otherwise identical conditions, and conversion versus
time plots were made (Figure 4). It is seen that for the particle
size below 88 µm, the reaction rates were independent of
the size, which in turn offers support that the intraparticle-
diffusion resistance was absent and that the reaction is
1
/KE
ES [ ] E + S
(d)
(e)
1
/KW
WS [ ] W + S
t
The total concentration of the sites, C expressed as
C ) C + CAS + CBS + CES + CWS
t S
or
C ) C + K C C + K C C + K C C + K C C (9)
t
S
A
A
S
B
B
S
E
E
S
W W S
(
18) Fogler, H. S. Elements of Chemical Reaction Engineering; Prentice-Hall:
Englewood Cliffs, 1986.
Vol. 6, No. 3, 2002 / Organic Process Research & Development
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259

3
3
3
3
Figure 5. Typical first-order reaction plot lines: effect of catalyst loading (/, 50 kg/m ; ×, 40 kg/m ; 4, 30 kg/m ; 9, 20 kg/m ;
3
]
, 10 kg/m ).
or, the concentration of vacant sites,
For equimolar quantities of A and B, the integration of
eq 10 yields the following
Ct
C )
(10)
S
XA
(
1 + K C + K C + K C + K C )
A A B B E E w w
)
C k wt ) k t
(18)
Ao R2
1
1
- XA
If surface reaction (c) controls the rate of reaction, then the
rate of reaction of A is given by
When M . 1, eq 12 leads to a pseudo-first-order kinetics;
hence, upon integration it becomes,
dCA
-
rA ) -
) k C C - k ′C C
(11)
2
AS BS
2
ES WS
-ln(1 - X ) ) k C wt ) k t
(19)
A
R2 Bo
1
dt
where, k ) kR2CBow.
1
K K C C
E
W
E
W
2
k2 K K C C -
Ct
{
A
B
A
B
}
Thus, further experiments were done to study the effects
of catalyst loading, concentration of reactants, and temper-
ature to validate the theory.
dCA
dt
K2
-
)
(12)
2
(
1 + K C + K C + K C + K C )
A
A
B
B
E
E
W
W
Effect of Catalyst Loading. The catalyst loading based
on the total volume of reaction mixture was varied at five
different values from 10 to 50 kg/m at a mole ratio of DPO
to benzyl chloride of 7:1. It was observed that both the rate
of reaction and rate of conversion had increased with catalyst
loading due to the increase in available sites. The concentra-
tion profile indicated a first-order profile, and hence typical
when the reaction is far away from equilibrium
2
3
dCA k C K K C C
2
t
A
B
A
B
-
)
(13)
(14)
2
dt
(
1 + K C )
∑
i
i
k wC C
R2
A B
)
2
(
1 + k C )
∑
i i
A
plots of -ln(1 - X ) versus time were made (Figure 5) for
each catalyst loading to get the slopes k1, the pseudo-first-
order constant, which were in turn plotted against solid
loading w (Figure 6) to get a linear relationship. This is due
to the proportional increase in the number of active sites.
where kR2w ) k
2
C2
t
A B
K K ; w is catalyst loading. If the
adsorption constants are very small, then the above equation
reduces to
dCA
The value of kR2 thus obtained from k
10 m‚ kmol ‚kg ‚s .
1
at 90 °C is 1.21 ×
-
) k C C w
(15)
-6
6
-1
-1 -1
R2
A
B
dt
Effect of Mole Ratio. The effect of the mole ratio of the
reactants was studied for different mole ratios of diphenyl
oxide and benzyl chloride (7:1, 8:1, 10:1, and 12:1) under
otherwise identical conditions (Figure 7). It was found that
as the mole ratio of diphenyl oxide to benzyl chloride was
changed, the conversion of diphenyl oxide remained practi-
cally the same, which shows zero-order dependence on
diphenyl oxide concentration and a typical first-order de-
pendence on benzyl chloride concentration.
Let CB0/CA0 ) M, the molar ratio of diphenyl oxide to benzyl
chloride at time t ) 0. Then eq 10 can be written in terms
of fractional conversion as
dXA
)
k wC (1 - X )(M - X ) ) k C (1 - X )(M - X )
R2
Ao
A
A
1
Ao
A
A
dt
(16)
which upon integration leads to:
ln{(M - X )/M(1 - X )} ) k C (M - 1)t
Effect of Temperature. The effect of temperature was
studied at five different temperatures under otherwise similar
conditions (Figure 8). The conversion of benzyl chloride
(17)
A
A
1 Ao
when M is other than unity.
260
•
Vol. 6, No. 3, 2002 / Organic Process Research & Development

Figure 6. Relationship berween k
constant) and catalyst loading, w.
1
(pseudo-first-order rate
Figure 9. Arrhenius plot.
Figure 7. Effect of mole ratio of DPO to benzyl chloride.
Figure 10. Catalyst reuse and activity.
activation energy was found to be 74.82 kJ/mol. The high
value of activation energy again shows that the reaction was
kinetically controlled and occurred at the surface of the
reaction.
Thus, the kinetics of the reaction was established through
the LHHW surface-reaction controlled mechanism in the
absence of both internal and external mass-transfer resis-
tances.
Effect of Catalyst Reuse.The reusability of the catalyst
was studied by recycling the filtered and acetone-washed
catalyst under otherwise identical conditions. Figure 10
shows the conversion of benzyl chloride against time, and
that the conversion has been decreased from 66 to 50% from
the fresh to the third reuse of the catalyst. There was attrition
of the catalyst; hence; some catalyst was lost during filtration.
Attrition has no effect on the acidity of the catalyst since it
is on the pore surface and no acid sites are lost even though
particle size is reduced. The batch size was doubled, and
Figure 8. Effect of temperature on conversion of benzyl
chloride.
increased with increase in temperature of the reaction.
Correspondingly -ln(1 - X
each temperatures (Figure 9), and these slopes (k
A
) versus time were plotted at
) were used
1
to make the Arrhenius plot (Figure 10). From the slope of
the curve the apparent activation energy was calculated. The
Vol. 6, No. 3, 2002 / Organic Process Research & Development
•
261

[A
0
] concentration of A in bulk liquid phase, kmol/m3
after the reaction the catalyst was filtered. There was a loss
of 4.5% catalyst during filtration. Thus, in the next experi-
ment, the volume of the reaction mixture was adjusted to
B reactant species, diphenyl oxide
[B ] concentration of B in bulk liquid phase, kmol/m3
0
3
make the catalyst loading, 50 kg/m , the standard value. It
concentration of A, mol/m3
A0 initial concentration of A in Bulk liquid phase, kmol/m3
AS concentration of A at the catalyst surface, kmol/m3
C
C
C
C
C
C
C
A
was found that the conversions were practically the same as
in the previous run, thereby suggesting that there was no
loss in activity.
Thus, it can be concluded that there was little decrease
in the catalyst activity with reuse.
concentration of B, kmol/m3
B
BS concentration of B at the catalyst surface, kmol/m3
B0 initial concentration of B in bulk liquid phase, kmol/m3
wp Wietz-Prater parameter, dimensionless
Conclusions
D reaction product
The Friedel-Craft alkylation of diphenyl oxide with
benzyl chloride was studied by using sulphated zirconia as
the catalyst. This catalyst is reusable. The effects of various
parameters were studied on the rate of the reaction under
otherwise similar conditions. It was seen that external mass-
transfer resistance can be eliminated by providing adequate
stirring and internal mass-transfer resistance was also absent.
A LHHW model was tested which shows that the reaction
is intrinsically kinetically controlled.
2
D
AB diffusion coefficient of A in B, m /s
2
D
BA diffusion coefficient of B in A, m /s
d
p
diameter of the catalyst particle, m
2
D
e
effective diffusivity, m /s
E reaction product
equilibrium constants of various species i
pseudo-first-order rate constant, s- ‚m ‚kg-cat
R2 second-order surface reaction rate constant, m ‚kg-cat-1‚s-1
SL-A,kSL-B solid-liquid mass-transfer coefficient for A and B,
respectively
K
i
1
3
-1
k
k
k
1
3
Acknowledgment
S.S. acknowledges University Grants Commission, India,
for an award of a Senior Research Fellowship, and G.D.Y.
acknowledges the Darbari Seth Endowment for the Chair
and research grant. G.D.Y. is grateful to the Michigan State
University, East Lansing, MI, for hosting him as the
Johansen-Crosby Visiting Chair Professor of Chemical
Engineering during 2001-2002, which provided excellent
time for creative pursuits.
R radius of the catalyst particle, m
rate of the reaction of A, kmol‚m-3‚s-1
r
r
A
obs observed rate of the reaction, kmol‚kg-cat-1‚s-1
3
w catalyst loading, kg/m of liquid phase
X
A
fractional conversion of A
η effectiveness factor
density of the catalyst particle, kg/m3
F
p
NOMENCLATURE
Received for review November 15, 1999.
OP990099Y
A reactant species, benzyl chloride
2
3
a solid-liquid interfacial area, m /m of liquid phase
p
262
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Vol. 6, No. 3, 2002 / Organic Process Research & Development