Chapter 28
Isomorphous Substitution of Iron in the Faujasite Lattice P. Ratnasamy, A. N. Kotasthane, V. P. Shiralkar, A. Thangaraj, and S. Ganapathy
Downloaded by UNIV OF LEEDS on May 18, 2016 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch028
National Chemical Laboratory, Pune 411008, India
The crystalline faujasite Y zeolites containing iron have been prepared. Evidence for the presence of Fe in the lattice framework is obtained using XRD, solid state MASNMR < Si, Al and C>, ESR, both framework and hydroxyl IR spectroscopies and DTA. Lattice Fe leads to increase in the XRD unit cell parameters.Spin echo experiments indicate that the spin—spin relaxation time of Si is shortened due to the presence of Fe in the framework. CPMASNMR 29
27
13
29
13
spectra of C atoms in tetraethylammonium-ZSM-20, a zeolite with a faujasite—like structure, also exhibit line broadening due to the interaction of 3+
Fe with the template ion. DTA studies indicate that Fe-faujasites have lower thermal stability than their Al-analogs. The (OH) vibration frequency shifts from 3540 and 3630 to 3570 and 3643 cm respectively on isomorphous substitution of Al by Fe. Relative changes in the intensity of the ESR peak at g = 4.3 at low temperatures also support the conclusion that iron can be inserted in the fauja site lattice positions. -1
BarrerC1) of
Al
elements
h a d r e v i e w e d t h e isomorphous
or
Si
i n the
s u c h a s Ga,
substitution
zeolite
Be,
B,
substitution
framework Fe,
by
other
C r , Ρ and Mg. The
o f A l by Fe i n t h e ZSM-5 framework 0097-6156/89/0398-0405$06.00/0 ο 1989 American Chemical Society
Occelli and Robson; Zeolite Synthesis ACS Symposium Series; American Chemical Society: Washington, DC, 1989.
is
406
ZEOLITE SYNTHESIS now w e l l Pott
e s t a b l i s h e d ( 2-5).
I n 1972,
( 6 ) showed u n a m b i g u o u s l y t h a t
faujasite
McNicol
iron
and
impurities i n
zeolites
c a n occupy s u b s t i t u t i o n a l l a t t i c e 3+ positions. From EPR s t u d i e s o f t h e Fe impurity i n NH - f a u j a s i t e , D e r o u a n e e t a l . ( 7 ) showed t h a t i r o n 4 3
can
be s i m u l t a n e o u s l y
Fe
species
forms : 3+ i n t h e a l u m i n o s i l i c a t e framework, Fe
acting
as
Fe
counter ions
Downloaded by UNIV OF LEEDS on May 18, 2016 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch028
compound w i t h precipitated iron
strong
deliberate lattice
iron
ions 3+
another
In both the s t u d i e s , the
as an i m p u r i t y
i n the z e o l i t e
was made t o
positions.
zeolite,
or
+
exchange s p i n - s p i n i n t e r a c t i o n s ,
attempt
to
i n three
and Fe^O^
on t h e z e o l i t e .
occurred
first
present
introduce
and 3+ Fe
in
S z o s t a k and Thomas
