Chapter 14
Cancrinite Crystallization from Alkaline Aluminosilicate Systems Containing Large and Small Cations 1
2
C. Colella and M. de' Gennaro
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1
Dipartimento di Chimica, Ingegneria Chimica e Materiali, Università de L'Aquila, 67040 Monteluco di Roio (AQ), Italy Dipartimento di Scienze della Terra, Università degli Studi di Napoli, Via Mezzocannone 8, 80138 Naples, Italy 2
Cancrinite crystallization, promoted by the joint presence in the reaction system of lithium and a large cation, has been thoroughly investigated, pointing out the specificity of the cationic couple for the synthesized phase. The products obtained have been characterized by means of X-ray diffraction, chemical, microscopy and thermal analyses. A hypothesis on the mechanism of cancrinite formation has been worked out, also on the basis of the preliminary results of structural analysis. The
specificity
cation-structure
c r y s t a l l i z a t i o n has been s y n t h e s i z e d phases form r e a c t i o n mixture through
in
recognized
fora
( 1 ) . Although
r o l e played
i n t h e presence
their action,
normally
i n the
i tis likely one, as i t
when s y n t h e s e s
o f organic cations (1). (_2_),
as most
i s present
by them i s a t e m p l a t i n g
systems, t h e r e i s e v i d e n c e
the l a r g e r one
silicates
time,
i t i s v e r y seldom c l e a r t h e mechanism
e v i d e n t i n some i n s t a n c e s , e s p e c i a l l y polycationic
long
only i f a given cation
which t h e s i n g l e c a t i o n s develop
t h a t t h e main
framework
is
a r e performed
Referring to
syntheses i n
that a single cation, often
p l a y s the s t r u c t u r e - d i r e c t i n g
role;
n e v e r t h e l e s s c a s e s a r e known o f c a t i o n i c c o u p l e s which determine t h e formation
of specific
s y n t h e s i z e d i n mixed
frameworks,
Na,Cs
f o r instance
systems ( 3 ) ,
zeolites
RHO,
e d i n g t o n i t e , formed
from
Ba+Li (_4_), EAB and m a z z i t e , b o t h o f them o b t a i n e d i n t h e presence o f sodium and tetramethylammonium A r e c e n t paper
(TMA)
(_5).
(6) r e p o r t s an i n t e r e s t i n g case o f a f e l s p a t h o i d ,
c a n c r i n i t e , p r e v i o u s l y o b t a i n e d i n t y p i c a l l y s o d i c environments w i t h (7) o r w i t h o u t
added s a l t s
(8), s y n t h e s i z e d i n b i c a t i o n i c
formed by l i t h i u m and a l a r g e a l k a l i n e c a t i o n Such s y n t h e s e s
suggest
that cancrinite
systems
(rubidium o r cesium).
i s a further
phase, t h e
0097-6156/89/0398-0196$06.00A) ο 1989 American Chemical Society Occelli and Robson; Zeolite Synthesis ACS Symposium Series; American Chemical Society: Washington, DC, 1989.
14.
COLELLAANDDEGENNARO
f o r m a t i o n o f which may and,
moreover, t h a t
depend
on the j o i n t p r e s e n c e
the c o u p l i n g
of a large
and
c a t i o n produces the same r e s u l t o f the p r e s e n c e a l o n e o r p l u s a sodium T h i s works aims,
197
Cancrintie Crystallization of
a
two
o f sodium
first
of
all,
the i n v e s t i g a t i o n a l s o t o the
to
strengthen
couple T l , L i ,
radius i s very c l o s e to that o f behave a l s o i n o t h e r o c c a s i o n s
Rb
+
hydroxide
this assertion,
of this
and
inasmuch
as the
in a similar
the f o r m a t i o n o f phases b e l o n g i n g
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alkaline
salt.
o p t i m i z i n g C s , L i - and R b , L i - c a n c r i n i t e c r y s t a l l i z a t i o n and
F u r t h e r purposes
cations
small
extending
are: i )
ionic
three large cations
way
(see
f o r instance
t o the s t r u c t u r a l type
study
+
as T l
to v e r i f y
ABW
that
(9)).
cationic
c o u p l e s , e x c l u d i n g sodium and
d i f f e r e n t from the above t h r e e , do
give r i s e
i i ) to
to
cancrinite;
c a n c r i n i t e s from a p h y s i c o - c h e m i c a l a h y p o t e s i s on
the r o l e
characterize
not
the
synthesized
p o i n t o f view; i i i )
t o work out
p l a y e d by
the two
cations i n
cancrinite
formation.
Experimental R e f e r r i n g t o the r e a c t i o n c o n d i t i o n s p r e v i o u s l y found runs were performed a t
200°C and a t
t e f l o n c o n t a i n e r s , r o t a t e d f o r programmed times a thermostated contact of
o v e n . P a r t i c u l a r c a r e has
the
Reagent
grade
mixtures
and
reaction chemicals
2
Products), T 1 S 0 2
3
40%
hydroxide
ion Si0
2
dried
RbOH o r
the
dioxide.
(see
aluminum KOH,
in
reaction below): hydroxide
CsOH s o l u t i o n
2
(Merck),
day)
a v o i d i n g the
carbon
preparing
L i O H - H 0 , NaOH,
solution
in
exchange t e s t s ),
concentrated
(Fluka) ,
4
been taken for
i n sealed
( u s u a l l y one
w i t h atmospheric used
for
(Ludox,
( S e r v a , 61.35% A l 0 ) , TMA
were
the s o l u t i o n s
s i l i c a suspension
(Merck),
magma
(6), synthesis
autogenous p r e s s u r e
(Alfa
Ba(0H)2 · 8 H
ammonium h y d r o x i d e
2
0
solution
(Carlo Erba). The
oxide
batch
c r y s t a l l i z a t i o n was
composition
η L i 0 · mMe 0 - A l 0 - 2 S i 0 2
where Me
i s Rb,
2
L i , B a and
2
3
Cs, T l o r m i x t u r e s
2, m between 2 and
tested
for
2
-100-110
P^O
o f them, η ranges between
10. R e f e r r i n g i n p a r t i c u l a r t o the
runs
L i , N H ^ systems, the r a t i o s 2Ba/2Ba+Li and NH
s y s t e m a t i c a l l y v a r i e d , c e t e r i s p a r i b u s , between t o t a l a l k a l i n i t y ranged between 1 and At the end
of
cancrinite
as f o l l o w s :
the r e a c t i o n
mother l i q u o r s by f i l t r a t i o n ,
0 and
1
and
i n mixed
/NH^+Li were 1,
while
the
4.
the p r o d u c t s
washed and
were
separated
from
d r i e d o v e r n i g h t a t 100°C.
X-ray powder d i f f r a c t i o n i n v e s t i g a t i o n s were made i n c o o p e r a t i o n w i t h P.
Norby ( O s l o
University)
(Odense U n i v e r s i t y ) . F o r phase determination a Guinier-Hagg (10); q u a r t z i n t e r n a l diagrams were i n d e x e d
and
I.G.
camera
has been used
s t a n d a r d a=4.91309 À, and
and E.
i d e n t i f i c a t i o n and
Krogh
Andersen
lattice
costants
(CuKo^ =1.5451 Â
c=5.40426 %
l a t t i c e constants r e f i n e d
(11).
by l e a s t
Occelli and Robson; Zeolite Synthesis ACS Symposium Series; American Chemical Society: Washington, DC, 1989.
The
square
198
ZEOLITE SYNTHESIS
calculations
(programme
PARAM
p o s i t i o n s were d e t e r m i n e d ( 1 3 ) . The d a t a used Siemens D5000
by
(1.2)).
Extra
f o r these determinations
diffractometer
radiation).The Li,Cs-C
4°
