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Crystal symmetry and shape selectivity in ZSM-5 zeolites
531
Catalysis Today, 3 (1988) 531-535
Elsevier Science PublishersB.V.,Amsterdam-PrintedinThe Netherlands
CRYSTAL
SYMMETRY
AND SHAPE
SELECTIVITY
IN ZSM-5
ZEOLITES
P. RATNASAMY National
Chemical
Laboratory,
Pune
411 008,
India.
ABSTRACT The
crystallographic
to influence
their
of
Crystals
toluene.
exhibit
higher
symmetry
shape
of
selective
with
more
ZSM-5
zeolites
bahaviour
is
shown
in the methylation
pronounced
monoclinic
symmetry
para selectivity.
INTRODUCTION An
interesting
is its
reversible
clinic
crystal
the shape
(l), as
well
a
matter
later
changes,
reported
In
the
1073
scopy. hexanes toluene
IR
and
their
in addition also
concluded
favouring to
study,
adsorption
catalytic
and
the
of
activity
framework
Al
content, governig Hay
such
form
H20, in
01988 ElsevierSciencePublishers B.V.
factors,
was
to
(3,4).
electron
cyclethe
form.
found
calcined
scanning
and
structural
orthorhombic
samples,
XRD,
, under-
monoclinic
(192).
in the zeolite
HZSM-5 by
the
obtained +
to the above
orthorhombic
Al content
and Na
influenced
al.
ions,
variables
structure
et
materials
Extra
etc.)
effect
Wu
form,
form.
and
ZSM-5
to
with methanol.
0920-5861/&3/$03.50
catalytic
H+
critical
ZSM-5
sample
characterised
spectroscopy,
and
protonic
the
the
monoclinic
present
K were
This
activity,
literature.
molecules
molecules,
(3) that,
by lower
NH4'
organic
among
of
the
the
transformation
the
temperatures
from
be facilitated
and
of
higher
change
be
changes
temperature
to
adsorbed to
we report
on
of the orthorhombic
displacive
(cations,
symmetry
with
structure
zeolite
and mono-
changes
in
ZSM-5
orthorhombic
of the as-synthesised
exchanged
converted
the
communication,
reactions.
reported
and containing
identified
Jaeger
The
those
when
In this
structural
studies
reversible
symmetry
were
been
framework
synthesis
went
such
of
between
(1).
in catalytic
far,
on XRD
as
the
after
the
so
based
that
the
of
selectivity not,
feature
transformation
structures
consequences
has
structural
and
at
823
micronormal
methylation
of
532 EXPERIMENTAL Sample
A was a ZSM-5 procedures
following of the
organic
nation
in
zeolite
template
air
(823
K for
with
NH4+.
K
(Sample
in
air
at
393
D).
divided
K,
at
823
(Sample
823
and
1073
by
XRD,
IR,
technique,
have done
were
were
conducted
and
the
RESULTS For
sample those
Due
to those
to
the
of
the
been
(Na
exchanged =
0.05
calcined E
described The
was
for
25
F,
down-flow,
mesh)
was
by
hrs
in
and
adsorptive
The XRD measure-
quartz
measurements
integral
reactor
chromatography.
pretreated
at air
respectively.
activity
gas
NH4N03
dried
of the zeolite
(5,7).
catalytic
with
%)
and
zeolite
B) was calcined
microanalysis
analysed
in air
at
The
823
K for
of the feedstock.
was,
by
What symmetry
F)
the
in
are
orthorhombic
properties
question,
it
has in
due to differences
to
of
the
be
of
the
in
calcined
in crystal
and
of the
organics
these
the
the
compared
lines.
As the
monoclinic
sample
823
to
K
calcined
(Sample
E).
at 2 &values
were
more
clearly
of
crystal
1). of
this
monoclinic
zeolites
first
adsorption
pores,
Pnma
lower
doublets
respectively
to
the
The
at
spectra
group
transformation
of the three
consequences
the
removal
pronounced
48-49',
in was
calcination.
that
F than in E (Fig.
from
matter
intensities
XRD
space
(2 @)
The
(l-4),
more
than
and
7-10“
on
separation
29-30
organic
the
others
from
orthorhombic
of 23-25".
however,
catalytic
differences
of
calculated
an
around
occurred
(Sample
seen in Sample
values
from
enhanced
form
example,
d
presence
region
pores
24-25,
the
the lines
earlier
character 1073
A,
of
monoclinic
For
probe
K.
calculated
in the
reported
at
in the
(Sample
samples
to the introduction
intensities
from
ions
by calci-
AND DISCUSSION
matched (1).
Nat
again
and
yield
were
lo-20
and
removal
After
bromide)
for the characterisation
in a vertical,
(2 g,
5 hrs prior
to
298
the
sample
batches
already
products
catalyst
C)
electron
at
= 350) synthesised
(5).
This material
methods
SEM,
ments
2
K
The experimental
15 hrs),
This
into
earlier
(tetrapropylammonium
were exchanged
solution
(SiO,/A1203
published
?
on
size or acid
adsorption
and
answering
this
Before
established catalytic
change
that
the
properties strength
observed are
not
distribution.
533
5(
AN
LA
1083
K
& k
823K
-7iFI.I 48
50
Fig. 1 x-r&;; diffraction patterns of sanales I;:Tnd 9
Fig. 2 Scanning electron micrographs (.?1 and R respectively)
of samples E 2nd ?
534
Fig. of
B, illustrates
2, A and the
crystals
in
of the crystals 6-8
pm
acid
(Fig.
0.22
ively.
NH3
(6).
have
similar
crystal
=
balance. n-
F were
of
adsorption
the
like
crystal
and
F,
E
and
F
in
the
to
Now, nation 823
of
be
K,
former.
The 1.7
differ
to
cyclohexane the
equal)
2
6.4
the
and
mainly
in of
vapour
pressure
using
a McBain
X
(wt.)
of
corresponding
H20,
values The
respectively. (which
is
all
other
7.5
for
zeolite,
is
E
adsorption
F
% wt.,
of
K
and
greater
at
a measure factors
samples
shape
E
selectivity
shape
temperature.
over
sample
reaction
Thus,
However,
some from
sample a
that
K, while is
a
F,
more
since sample
similar
was
the
shape
been
values
1. than
Moreover,
also
found
to
example,
in
the
distribution
of
the
is
to
of
873
K was
53:4:28.4:18.2
"more
monoclinic"
selective
character.
F is
from
Table less
selective.
For
F which
E had
in
temperature
sample
dealumination the
shown
compared
respectively,
exhibits
is
of samples
F is slightly
selectivity
at
possible
1073
toluene
is more
shape
reaction
1).
distribution
of sample
(p:m:o)
E,
there
of
activity
their
product
toluene
(Table
is
and
methylation
75:15:10,
sample it
n-
and
150 Si/Al
samples
The
E and
13.4
and
activity
the
isomers
723
3.7,
E, the former
with
methylation
than
and
1).
samples
indicating
samples,
increase
at
over
13.7
of
catalytic
both
found
Hence
acidity (Fig.
Model
similar
at 198 K and a relative
being
catalytic
the
xylene
and
F.
respectively.
size
that of sample for
and
and
by the latter.
The
While
E
size
3.0,
respectively,
possessed
(Stereoscan
(7),
esti-
be 0.24
E and F, respect-
revealed
selectivity
shape
samples
sites
to
and
techniques
acid
found
equal
temperature
by
microanalysis
adsorbed
cyclohexane,
sample
ratio of
E
strong
size
and
acidity
the
out
crystals
measured
Sample
and
for
was
0.5,
of
for
symmetry
H20, n- and cyclohexanes
the
samples,
K was
The
the same
carried
573
samples
crystallographic
P/PO
two
number
micrographs
respectively.
is about
was
above
probe
both
F,
electron
characterise
the
NH3
The
random
in
distribution
to
of the zeolite
Electron for
and
in
of
desorbing cell
USA)
their
order
distribution
per unit
Camb.,
F
In
earlier
from
E
scanning
the samples
desorption
described mated
samples
in both 2).
strength
programmed
the
obtained
heat
treated
lattice of
by calciat
sites
strong
acid
only
in
the
sites
535 estimated unit
from
cell
NH3
for
desorption
samples
dealumination
(in
E
sample
and F)
F,
10 %) and the observed
differences in crystal
differences
TABLE
1
Shape
selectivity
of samples
Reaction
:
Feed hr
Reaction Pressure
-1:
:
Sample Products
in shape
and the
to be low selectivity
0.22 extent (less
per of than
probably
symmetry.
E and F.
Methylation
of toluene (4:l molar)
8.4
temp.:
:
(0.24
respectively),
C7H8 + CH30H
WHSV,
K
is considered
arise
from
573
above
723 K
Atm. E
1
(wt. X)
Benzene Toluene
82
85.9
p-xylene
5.4
6.5
m-xylene
6.1
3.4
o-xylene
2.5
2.2
C9+
4.0
2.0
C8 isomers p-xylene
39
53.4
m-xylene
43
28.4
o-xylene
18
18.2
REFERENCES 1. 2. 3. 4. 5. 6. 7. 8.
E.L. Wu, S.L. Lawton, D.H. Olson, A.C. Rohrman Jr. and G.T. Kokotailo, J. Phys. Chem., 83 (1979), 2777. H. Nakamoto and H. Takahashi, Chem. Lett., 1013, 1981. D.G. Hay and H. Jaeger, J. Chem. Sot., Chemm. Commun., 1433, 1984. J.M. Berak, B. Kanik, PL. Eysymont and J. Mejsuer, React. Kinet. Catal. Lett., 15 (1984). S.B. Kulkarni, V.P. Shiralkar, A.N. Kotasthane, R.B. Borade and P. Ratnasamy, Zeolites, 2, (1982), 313. G.P. Babu, S.G. Hegde, S.B. Kulkarni and P. Ratnasamy, J. Catal., 81 (1981), 471. P. Ratnasamy, G.P. Babu, A.J. Chandwadkar and S.B. Kulkarni, Zeolites, 6 (1986). 98. N.Y. Chen, W.W. Kaeding and F.G. Dwyer, J. Am. Chem. Sot., 101 (1977), 6387.
Catalysis Today, 3 (1988) 531-535
Elsevier Science PublishersB.V.,Amsterdam-PrintedinThe Netherlands
CRYSTAL
SYMMETRY
AND SHAPE
SELECTIVITY
IN ZSM-5
ZEOLITES
P. RATNASAMY National
Chemical
Laboratory,
Pune
411 008,
India.
ABSTRACT The
crystallographic
to influence
their
of
Crystals
toluene.
exhibit
higher
symmetry
shape
of
selective
with
more
ZSM-5
zeolites
bahaviour
is
shown
in the methylation
pronounced
monoclinic
symmetry
para selectivity.
INTRODUCTION An
interesting
is its
reversible
clinic
crystal
the shape
(l), as
well
a
matter
later
changes,
reported
In
the
1073
scopy. hexanes toluene
IR
and
their
in addition also
concluded
favouring to
study,
adsorption
catalytic
and
the
of
activity
framework
Al
content, governig Hay
such
form
H20, in
01988 ElsevierSciencePublishers B.V.
factors,
was
to
(3,4).
electron
cyclethe
form.
found
calcined
scanning
and
structural
orthorhombic
samples,
XRD,
, under-
monoclinic
(192).
in the zeolite
HZSM-5 by
the
obtained +
to the above
orthorhombic
Al content
and Na
influenced
al.
ions,
variables
structure
et
materials
Extra
etc.)
effect
Wu
form,
form.
and
ZSM-5
to
with methanol.
0920-5861/&3/$03.50
catalytic
H+
critical
ZSM-5
sample
characterised
spectroscopy,
and
protonic
the
the
monoclinic
present
K were
This
activity,
literature.
molecules
molecules,
(3) that,
by lower
NH4'
organic
among
of
the
the
transformation
the
temperatures
from
be facilitated
and
of
higher
change
be
changes
temperature
to
adsorbed to
we report
on
of the orthorhombic
displacive
(cations,
symmetry
with
structure
zeolite
and mono-
changes
in
ZSM-5
orthorhombic
of the as-synthesised
exchanged
converted
the
communication,
reactions.
reported
and containing
identified
Jaeger
The
those
when
In this
structural
studies
reversible
symmetry
were
been
framework
synthesis
went
such
of
between
(1).
in catalytic
far,
on XRD
as
the
after
the
so
based
that
the
of
selectivity not,
feature
transformation
structures
consequences
has
structural
and
at
823
micronormal
methylation
of
532 EXPERIMENTAL Sample
A was a ZSM-5 procedures
following of the
organic
nation
in
zeolite
template
air
(823
K for
with
NH4+.
K
(Sample
in
air
at
393
D).
divided
K,
at
823
(Sample
823
and
1073
by
XRD,
IR,
technique,
have done
were
were
conducted
and
the
RESULTS For
sample those
Due
to those
to
the
of
the
been
(Na
exchanged =
0.05
calcined E
described The
was
for
25
F,
down-flow,
mesh)
was
by
hrs
in
and
adsorptive
The XRD measure-
quartz
measurements
integral
reactor
chromatography.
pretreated
at air
respectively.
activity
gas
NH4N03
dried
of the zeolite
(5,7).
catalytic
with
%)
and
zeolite
B) was calcined
microanalysis
analysed
in air
at
The
823
K for
of the feedstock.
was,
by
What symmetry
F)
the
in
are
orthorhombic
properties
question,
it
has in
due to differences
to
of
the
be
of
the
in
calcined
in crystal
and
of the
organics
these
the
the
compared
lines.
As the
monoclinic
sample
823
to
K
calcined
(Sample
E).
at 2 &values
were
more
clearly
of
crystal
1). of
this
monoclinic
zeolites
first
adsorption
pores,
Pnma
lower
doublets
respectively
to
the
The
at
spectra
group
transformation
of the three
consequences
the
removal
pronounced
48-49',
in was
calcination.
that
F than in E (Fig.
from
matter
intensities
XRD
space
(2 @)
The
(l-4),
more
than
and
7-10“
on
separation
29-30
organic
the
others
from
orthorhombic
of 23-25".
however,
catalytic
differences
of
calculated
an
around
occurred
(Sample
seen in Sample
values
from
enhanced
form
example,
d
presence
region
pores
24-25,
the
the lines
earlier
character 1073
A,
of
monoclinic
For
probe
K.
calculated
in the
reported
at
in the
(Sample
samples
to the introduction
intensities
from
ions
by calci-
AND DISCUSSION
matched (1).
Nat
again
and
yield
were
lo-20
and
removal
After
bromide)
for the characterisation
in a vertical,
(2 g,
5 hrs prior
to
298
the
sample
batches
already
products
catalyst
C)
electron
at
= 350) synthesised
(5).
This material
methods
SEM,
ments
2
K
The experimental
15 hrs),
This
into
earlier
(tetrapropylammonium
were exchanged
solution
(SiO,/A1203
published
?
on
size or acid
adsorption
and
answering
this
Before
established catalytic
change
that
the
properties strength
observed are
not
distribution.
533
5(
AN
LA
1083
K
& k
823K
-7iFI.I 48
50
Fig. 1 x-r&;; diffraction patterns of sanales I;:Tnd 9
Fig. 2 Scanning electron micrographs (.?1 and R respectively)
of samples E 2nd ?
534
Fig. of
B, illustrates
2, A and the
crystals
in
of the crystals 6-8
pm
acid
(Fig.
0.22
ively.
NH3
(6).
have
similar
crystal
=
balance. n-
F were
of
adsorption
the
like
crystal
and
F,
E
and
F
in
the
to
Now, nation 823
of
be
K,
former.
The 1.7
differ
to
cyclohexane the
equal)
2
6.4
the
and
mainly
in of
vapour
pressure
using
a McBain
X
(wt.)
of
corresponding
H20,
values The
respectively. (which
is
all
other
7.5
for
zeolite,
is
E
adsorption
F
% wt.,
of
K
and
greater
at
a measure factors
samples
shape
E
selectivity
shape
temperature.
over
sample
reaction
Thus,
However,
some from
sample a
that
K, while is
a
F,
more
since sample
similar
was
the
shape
been
values
1. than
Moreover,
also
found
to
example,
in
the
distribution
of
the
is
to
of
873
K was
53:4:28.4:18.2
"more
monoclinic"
selective
character.
F is
from
Table less
selective.
For
F which
E had
in
temperature
sample
dealumination the
shown
compared
respectively,
exhibits
is
of samples
F is slightly
selectivity
at
possible
1073
toluene
is more
shape
reaction
1).
distribution
of sample
(p:m:o)
E,
there
of
activity
their
product
toluene
(Table
is
and
methylation
75:15:10,
sample it
n-
and
150 Si/Al
samples
The
E and
13.4
and
activity
the
isomers
723
3.7,
E, the former
with
methylation
than
and
1).
samples
indicating
samples,
increase
at
over
13.7
of
catalytic
both
found
Hence
acidity (Fig.
Model
similar
at 198 K and a relative
being
catalytic
the
xylene
and
F.
respectively.
size
that of sample for
and
and
by the latter.
The
While
E
size
3.0,
respectively,
possessed
(Stereoscan
(7),
esti-
be 0.24
E and F, respect-
revealed
selectivity
shape
samples
sites
to
and
techniques
acid
found
equal
temperature
by
microanalysis
adsorbed
cyclohexane,
sample
ratio of
E
strong
size
and
acidity
the
out
crystals
measured
Sample
and
for
was
0.5,
of
for
symmetry
H20, n- and cyclohexanes
the
samples,
K was
The
the same
carried
573
samples
crystallographic
P/PO
two
number
micrographs
respectively.
is about
was
above
probe
both
F,
electron
characterise
the
NH3
The
random
in
distribution
to
of the zeolite
Electron for
and
in
of
desorbing cell
USA)
their
order
distribution
per unit
Camb.,
F
In
earlier
from
E
scanning
the samples
desorption
described mated
samples
in both 2).
strength
programmed
the
obtained
heat
treated
lattice of
by calciat
sites
strong
acid
only
in
the
sites
535 estimated unit
from
cell
NH3
for
desorption
samples
dealumination
(in
E
sample
and F)
F,
10 %) and the observed
differences in crystal
differences
TABLE
1
Shape
selectivity
of samples
Reaction
:
Feed hr
Reaction Pressure
-1:
:
Sample Products
in shape
and the
to be low selectivity
0.22 extent (less
per of than
probably
symmetry.
E and F.
Methylation
of toluene (4:l molar)
8.4
temp.:
:
(0.24
respectively),
C7H8 + CH30H
WHSV,
K
is considered
arise
from
573
above
723 K
Atm. E
1
(wt. X)
Benzene Toluene
82
85.9
p-xylene
5.4
6.5
m-xylene
6.1
3.4
o-xylene
2.5
2.2
C9+
4.0
2.0
C8 isomers p-xylene
39
53.4
m-xylene
43
28.4
o-xylene
18
18.2
REFERENCES 1. 2. 3. 4. 5. 6. 7. 8.
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