Synthesis and Characterization of Metal Aluminophosphate Molecular

Chapter 23

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Synthesis and Characterization of Metal Aluminophosphate Molecular Sieves Stephen T. Wilson and Edith M. Flanigen Union Carbide Corporation, UOP Molecular Sieve Technology Department, Tarrytown Technical Center, Tarrytown, NY 10591

Novel metal aluminophosphate molecular sieves (MeAPO-n) have been synthesized, where Me can be the divalent form o f Co, Fe, Mg, Mn, or Zn, or trivalent Fe. These MeAPO molecular sieves have tetrahedral frameworks containing metal, aluminum, and phosphorus, and exhibit a wide range o f compositions within the general formula 0 - 0.3 R : (Me Al P )O where x, y , and z represent normalized mole fractions with χ = 0.01-0.25, y = 0.15-0.52 and z = 0.35-0.6 and R refers to the organic template, an amine or quaternary ammonium s a l t . The structures can be envisioned as hypothetical AlPO frameworks with metal incorporated into some o f the Al s i t e s . The anionic framework charge generated by such substitution leads to Bronsted a c i d i t y . The 18 reported MeAPO structure-types include structures topologically related to z e o l i t e s , A1P0 , and SAPO molecular sieves as well as novel structures. The c a t a l y t i c properties o f MeAPO's are both metal and structure dependent, and as acidic catalysts they range i n activity from low to high. x

y

z

2

4

4

The h i s t o r y o f molecular s i e v e s y n t h e s i s encompasses some 40 years and i n c l u d e s the p r e p a r a t i o n o f aluminosi 1 i c a t e z e o l i t e s (1_>, p h o s p h o r u s - s u b s t i t u t e d a l u m i n o s i l i c a t e s ( 2 ^ 3 ) , and the microporous s i l i c a polymorphs ( 4 ) . More r e c e n t l y , t h e compositional and s t r u c t u r a l range o f molecular s i e v e s has been s i g n i f i c a n t l y increased by t h e d i s c o v e r y o f crystalline microporous aluminophosphate-based frameworks, beginning with t h e aluminophosphates (5^7) o r A l P 0 - n molecular s i e v e s . This i n i t i a l d i s c o v e r y was f o l l o w e d by the s i l i c o a l u m i n o p h o s p h a t e s ( 8 ) , t i t a n i u m aluminophosphates ( 9 ) , metal aluminophosphates (10-13), and metal s i l i c o a l u m i n o p h o s p h a t e s ( H ) designated SAP0-n, TAP0-n, MeAP0-n, and MeAPS0-n, r e s p e c t i v e l y . The acronym SAPO i s d e r i v e d from ( S i A l P ) 0 and ΤΑΡ0, MeAPO, and MeAPSO a r e d e r i v e d 4

x

y

2

2

0097-6156/89/0398-0329$06.00/0 ο 1989 American Chemical Society In Zeolite Synthesis; Occelli, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989.

330

ZEOLITE SYNTHESIS

s i m i l a r l y where the Τ = T i and Me = Metal as d e s c r i b e d . The s u f f i x "n" denotes a s p e c i f i c s t r u c t u r e type o r framework t o p o l o g y . The MeAPO f a m i l y d e s c r i b e d here marks the f i r s t demonstrated i n c o r p o r a t i o n o f the d i v a l e n t forms o f c o b a l t (CoAPO), i r o n (FAPO), magnesium (MAPO), manganese (MnAPO), o r z i n c (ZAPO) i n t o microporous frameworks d u r i n g s y n t h e s i s .


Experimental The s y n t h e s i s o f a MeAPO molecular s i e v e t y p i c a l l y uses an aqueous r e a c t i o n mixture formed by combining a d i s s o l v e d form o f the d i v a l e n t metal, o r t h o p h o s p h o r i c a c i d , a r e a c t i v e alumina, and an amine o r quaternary ammonium templating agent ( R ) . The metal i s t y p i c a l l y i n t r o d u c e d as the a c e t a t e o r s u l f a t e s a l t , o r as the metal oxide d i s s o l v e d i n d i l u t e phosphoric a c i d . A s y n t h e s i s mixture i s prepared i n one o f two ways: 1) An alumina isopropoxide) combined with F i n a l l y the hydroxide, i s 2)

source (e.g., pseudo-boehmite o r aluminum i s mixed with d i l u t e o r t h o p h o s p h o r i c a c i d , then an aqueous s o l u t i o n c o n t a i n i n g the metal s a l t . template, an amine o r quaternary ammonium added.

The alumina source i s combined with an aqueous s o l u t i o n o f the metal s a l t f i r s t , then d i l u t e o r t h o p h o s p h o r i c a c i d i s added, and f i n a l l y the template.

T y p i c a l r e a c t i o n mixtures have the molar c o m p o s i t i o n : y R : 2x MeO : (1-x) A 1 0 2

3

: P 0 : 40 H 0 2

5

2

where y = 1.0 - 2.5, and χ = 0.005 - 0.333. These r e a c t i o n mixtures a r e then heated q u i e s c e n t l y a t a temperature o f 100-200°C f o r s u f f i c i e n t time t o c r y s t a l l i z e the MeAPO m o l e c u l a r s i e v e . The p a r t i c u l a r time/temperature c o n d i t i o n s depend on the metal, the template, and the s t r u c t u r e - t y p e . In many cases a given r e a c t i o n mixture w i l l produce the same s t r u c t u r e s with each metal although the time/temperature c o n d i t i o n s may vary. The template R i s occluded i n the MeAPO product d u r i n g s y n t h e s i s and appears e s s e n t i a l t o the s y n t h e s i s o f these novel phases. I t can be removed t h e r m a l l y a t 400-600°C. Structures There a r e 18 r e p o r t e d MeAPO s t r u c t u r e - t y p e s ( T a b l e I ) . E i g h t o f these a r e z e o l i t e s t r u c t u r e analogs (17, 20, 34, 35, 37, 43, 44, 47) which were subsequently observed i n A l P 0 - b a s e d m a t e r i a l s . Seven s t r u c t u r e - t y p e s were f i r s t i d e n t i f i e d i n the A1P0 ( 5 , 11, 14, 16, 31), SAPO ( 4 1 ) , o r MeAPSO (46) f a m i l i e s (14,15). The remaining s t r u c t u r e s (36, 39, 50) were f i r s t observed i n the MeAPO f a m i l y . The x-ray powder d i f f r a c t i o n p a t t e r n s c h a r a c t e r i s t i c o f the s t r u c t u r e - t y p e s 5, 11, 17, and 20 (6,16,17); and 14, 18, and 31 (7) have been p r e v i o u s l y p u b l i s h e d . The x-ray powder p a t t e r n s 4

4

In Zeolite Synthesis; Occelli, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989.

23.

WILSON AND FLANIGEN

331

MeAPO Molecular Sieves

f o r the s t r u c t u r e - t y p e s 16, 46, and 50 (both c a l c u l a t e d and observed) a r e Included i n r e c e n t reviews o f A l P 0 - b a s e d s t r u c t u r e s (16,17), For the remaining novel s t r u c t u r e s 36, 39, and 41, x-ray powder p a t t e r n s a r e shown i n F i g u r e s 1-3. The 34 (18), 44 (19), and 47 (19) types a r e a l l now known t o be s t r u c t u r e s with the c h a b a z i t e framework topology (as determined by s i n g l e - c r y s t a l methods) but prepared with d i f f e r e n t templates, TEAOH, cyclohexy1 ami ne, or Ν,N-d1 e t h y l - e t h a n o l a m i ne, respectively. As i n i t i a l l y prepared, there was s u f f i c i e n t v a r i a t i o n i n the x-ray powder p a t t e r n s o f the a s - s y n t h e s i z e d forms f o r d i f f e r e n t framework t o p o l o g i e s t o be c o n s i d e r e d . Once c a l c i n e d , the three s p e c i e s e x h i b i t e s s e n t i a l l y i d e n t i c a l powder p a t t e r n s , c o n s i s t e n t with t h e framework topology. Other p r o p e r t i e s vary s u b s t a n t i a l l y among the three s p e c i e s . There s t i l l remains t h e p o s s i b i l i t y o f unique, template mediated, framework s i t i n g f o r the metal i n these and o t h e r tempiated forms o f the c h a b a z i t e topology.


4

Table I . T y p i c a l Templates and S t r u c t u r e - T y p e s f o r MeAPO M o l e c u l a r Sieves MeAPO Species

Structure Type

T y p i c a l Template

5 36 37 46 50

A1P04-5 Novel Faujasite MAPS0-46 Novel

Ν,N-diethylethanolami ne t r i propyl ami ne ΤΡΑ0Η + ΤΜΑ0Η di-n-propylamine di-n-propylamine

0.8 0.8 0.8 0.7 0.8

11 31 41

ΑΙΡΟ4-ΙΙ

A1P04-31 SAP0-41

di-n-propylamine di-n-propylamine di-n-propylamine

0.6 0.7 0.65

14 17 34 35 39 43 44 47

A1PÛ4-14 erionite chabazite levynite novel gismondine chabazite chabazite

isopropylamine quinuclidine tetraethylammoni urn quinuclidine di-n-propylamine di-n-propylamine cyclohexylamine Ν,N-di ethylethanolami ne

0.40 0.43 0.43 0.43 0.40 0.43 0.43 0.43

16 20

ΑΙΡΟ4-Ι6

quinuclidine tetramethylammoni urn

0.3 0.3

sodalite

Pore S i z e (nm)

Synthesis The s t r u c t u r e - t e m p l a t e r e l a t i o n s h i p s p r e v i o u s l y observed i n t h e f a m i l y a r e compounded now by the p a r t i c i p a t i o n o f the metal i n synthesis. A t one extreme t h e template

ΑΙΡΟ4


332

ZEOLITE SYNTHESIS

d(A) 1 11.2 100 10.8 31 4 6.54 11 5.59 5.39 31 4.64 13 4.27 34 15 4.10

(?) Ζ LU

H Z LU >

d(A) 4.03 3.95 3.72 3.27 3.15 3.08 2.80 2.58

1 13 14 5 12 7 6 7 5


ω cc

uu

16

24 32 40 DEGREES 20, CuKa

48

56

Figure 1. X-ray Powder D i f f r a c t i o n P a t t e r n o f MAP0-36. d(A) 3.01 2.95 2.74 2.64 2.36 1.78

d(A) 1 9.34 33 6.60 64 54 4.91 4.18 87 3.94 100 7 3.30 10 3.11

ζ LU LU >

1 15 35 14 10 10 5

LU OC

16

JJ

24

32

40

48

56

DEGREES 20, CuKa

Figure 2. X-ray Powder D i f f r a c t i o n P a t t e r n o f MAPO-39.

d(A) i 12.9 20 9.08 20 6.47 20 4.86 9 4.31 5 4.21 100 4.01 64

É z LU

Z LU

8

16

24 32 40 DEGREES 20, CuKa

48

Mi 3.88 23 3.83 18 3.53 14 3.46 17 3.03 12 2.39 9

56

Figure 3. X-ray Powder D i f f r a c t i o n P a t t e r n o f MAPO-41.


23.

WILSON AND FLANIGEN

333


tetramethylammoniurn (TMAOH) behaves c o n s i s t e n t l y a c r o s s a l l t h e AlP0 -based families, producing the sodalite o r 20 s t r u c t u r e - t y p e under most c o n d i t i o n s . A t the o t h e r extreme, di-n-propylamine templates a t least seven s t r u c t u r e - t y p e s depending on s y n t h e s i s c o n d i t i o n s and gel composition. 4


Te trame th y1ammon i um (TMAOH). Tetramethylammonium y i e l d s the 20 s t r u c t u r e - t y p e over a wide range o f gel composition and temperature (Table I I ) . Using a r e a c t i o n mixture prepared with magnesium a c e t a t e : 1.0 TMAOH : 2x MgO : (1-x) A 1 0 2

3

: P 0 2

5

: 40 H 0 : 4x HOAc 2

where χ = 0.083, 0.167, and 0.333, the 20 s t r u c t u r e i s the o n l y type observed at 100, 150, o r 200°C. Gel and product analyses f o r samples prepared a t 200°C are expressed as mole f r a c t i o n s , normalized t o 1 mole o f t o t a l product o x i d e , T 0 . The product oxide compositions r e f l e c t the gel composition and each e x h i b i t s TMA contents up t o , but not exceeding, one TMA per s o d a l i t e cage (or 0.167 TMA/T0 ). Product 3 e x h i b i t s an a n a l y s i s c o n s i s t e n t with o c c u p a t i o n o f 1/6 o f the framework T - s i t e s by Mg, with one TMA per s o d a l i t e cage. The framework charge i s completely balanced by occluded TMA . The remaining products have lower framework charge and l e s s than one TMA per s o d a l i t e cage. The amount o f TMA occluded i s n e v e r t h e l e s s g r e a t e r than the c a l c u l a t e d framework charge and t h i s excess charge i s probably balanced by n e g a t i v e l y charged s p e c i e s , such as phosphate o r hydroxide, occluded i n some o f the s o d a l i t e cages. 2

2

+

+

Table I I . Reaction Mixture and Product Analyses f o r MAPO-20 S t r u c t u r e s ( T 0 formula, anhydrous b a s i s ) 2

TMA

: ( Mg

Al

Ρ )0

2

T0 /R 2

Framework Charge*

1) Gel Product

0..250 0..131

0.042 0.041

0. 458 0. 454

0. 500 0. 505

7..6

-0. 031

2) Gel Product

0..250 0..135

0.083 0.084

0. 417 0. 401

0. 500 0. 515

7,.4

-0. 054

3) Gel Product

0,.250 0,.167

0.167 0.158

0. 333 0. 330

0. 500 0. 512

6..0

-0. 134

*Framework charge c a l c u l a t e d from chemical a n a l y s e s . Tetraethylammonium (TEAOH). In A1P0 s y n t h e s i s , ΤΕΑ0Η templates the s t r u c t u r e - t y p e s 5 and 18. In SAPO and i n MeAPO s y n t h e s i s , s t r u c t u r e s 5 and 34 are produced. Both 18 and 34 have pore systems c o n t r o l l e d by 8-rings and both have comparable, l a r g e v o i d volumes. The presence o f the Me o r Si i n the gel composition 4


334

ZEOLITE SYNTHESIS

f a v o r s s t r u c t u r e - t y p e 34 over 18. In MeAPO s y n t h e s i s the r a t e o f c r y s t a l l i z a t i o n o f the 34 s t r u c t u r e depends on the metal. The metals Mg, Co, and Zn r e a d i l y form pure 34 a t 100°C i n 2-4 days from the g e l composition: 1.0 TEAOH : 0.4 MeO : 0.8 A 1 0 4.8 iPrOH : 0.8 HOAc


2

:P 0

3

2

: 55 H 0 :

5

2

where the a c e t i c a c i d and isopropanol d e r i v e from the metal acetate s a l t and aluminum isopropoxide (AIP) used as r e a c t a n t s . Under s i m i l a r c o n d i t i o n s , MnAPO-34 r e q u i r e s more than 7 days t o c r y s t a l l i z e and FAP0-34 f a i l s t o c r y s t a l l i z e i n 21 days. Higher temperatures are r e q u i r e d t o c r y s t a l l i z e FAPO-34. The elemental a n a l y s i s o f three MeAPO's prepared from the above g e l a t 100°C are shown below (expressed as normalized T 0 f r a c t i o n s ) : 2

Species

TEAOH : ( Me

ZAP0-34 MAPO-34 CoAPO-34

Al

Ρ )0

0.083 0.095 0.396 0.079 0.095 0.400 0.108 0.085 0.407

T0 /R

2

Framework Charge

2

-0.077 -0.085 -0.069

12 13 9

0.509 0.505 0.508

These analyses and o t h e r s are c o n s i s t e n t with the occupancy o f each c h a b a z i t e cage by one TEA molecule, i . e . 1 TEA/12 T0 .(lj>) Using a d i f f e r e n t g e l composition, with pseudo-boehmite i n s t e a d o f AIP, the e f f e c t s o f gel metal c o n c e n t r a t i o n and c r y s t a l l i z a t i o n temperature on MAP0-34 s y n t h e s i s with TEAOH can be i l l u s t r a t e d ( F i g u r e s 4 and 5 ) . Reaction mixtures were prepared d i f f e r i n g o n l y i n Mg c o n c e n t r a t i o n ( x ) : 2

1.0 TEAOH : χ MgO : 0.8 A 1 0 2

: 1.0 P 0

3

2

5

: 40 H 0 : 2x HOAc 2

The i n i t i a l gel pH ranged from 3.5 - 4.5, i n c r e a s i n g with Mg content. At 100°C and a 2 day r e a c t i o n time ( F i g u r e 4 ) , the lowest Mg c o n c e n t r a t i o n (0.05) y i e l d s p r i m a r i l y template-free aluminophosphate hydrate s t r u c t u r e - t y p e s such as m e t a v a r i s c i t e and v a r i s c i t e (A1P0< : 2 H 0) and H (A1P0< : 1.5 H 0) (20,21). As the Mg c o n c e n t r a t i o n i s i n c r e a s e d toward 0.25, MAP0-34 becomes the major product and then the only product. At higher Mg c o n c e n t r a t i o n s non-microporous, Mg-rich s t r u c t u r e s i n c r e a s e a t the expense o f MAP0-34. The same s e r i e s o f g e l compositions d i g e s t e d f o r 5-7 days a t 100°C show s i m i l a r behavior, except f o r the g r e a t e r prominence o f the H s t r u c t u r e - t y p e a t the expense o f m e t a v a r i s c i t e and variscite structures. This s e r i e s o f g e l s c r y s t a l l i z e d a t 150°C f o r 3 days y i e l d s e x c l u s i v e l y mixtures ( F i g u r e 5 ) . Nhen no Mg i s p r e s e n t , o n l y the 5 and 18 s t r u c t u r e s a r e observed. A t the lowest Mg c o n c e n t r a t i o n (0.05) the 18 s t r u c t u r e c o e x i s t s with the 34, and as the Mg c o n c e n t r a t i o n i n c r e a s e s , the r e l a t i v e amount o f MAPO-34 i n c r e a s e s as the MAP0-5 decreases. At the highest Mg c o n c e n t r a t i o n examined the r a t i o o f MAP0-5 t o MAPO-34 i s about 2:1. 2

3

2

3


23.

WILSON AND FLANIGEN



% by X - R a y

Gel Mg/P 0 2

5

Figure 4. Product D i s t r i b u t i o n v s . Gel Mg C o n c e n t r a t i o n i n MAPO-34 S y n t h e s i s with TEAOH (100°C, 2 Days).

Figure 5. Product D i s t r i b u t i o n v s . Gel Mg C o n c e n t r a t i o n i n MAPO-34 S y n t h e s i s with TEAOH (150°C, 3 Days).


335


336

ZEOLITE SYNTHESIS

To summarize these r e s u l t s , a t constant template c o n c e n t r a t i o n and higher g e l Mg c o n c e n t r a t i o n s , Mg-rich, non-molecular s i e v e s t r u c t u r e s seem t o nucleate a t the expense o f MAPO-34. At g e l c o n c e n t r a t i o n s o f 0.4 and below, some MAPO-34 i s formed as long as there i s any Mg i n the g e l . These o b s e r v a t i o n s suggest t h a t under t h i s s e t o f c o n d i t i o n s there i s a p r e f e r r e d range o f g e l compositions f o r making pure MAPO-34 with TEAOH. Reaction mixtures o u t s i d e the p r e f e r r e d range produce mixtures c o n t a i n i n g a t l e a s t some MAPO-34 but the amount o f MAPO-34 d e c l i n e s as the Mg content o f the gel d e v i a t e s t o o f a r in e i t h e r d i r e c t i o n . The tendency o f gels with low Mg c o n c e n t r a t i o n s t o g i v e mixtures r a t h e r than simply a pure, low Mg MAPO-34 a l s o suggests t h a t MAPO-34 has a p r e f e r r e d product s t o i c h i o m e t r y . The products o b t a i n e d along with the MAPO-34 are t y p i c a l o f low Mg o r Mg-free g e l s , i . e . , MAPO-5 and aluminophosphates such as H o r m e t a v a r i s c i t e . I t i s p o s s i b l e t h a t some Mg i s a l s o i n c o r p o r a t e d i n Al s i t e s o f these aluminophosphate s t r u c t u r e s . 3

Q u i n u c l i d i n e (QUIN). The template q u i n u c l i d i n e y i e l d s the s t r u c t u r e - t y p e s 16 and 17 (ERI) i n A1P0 s y n t h e s i s and types 16, 17, and 35 (LEV) i n SAPO and MeAPO s y n t h e s i s . T y p i c a l s y n t h e s i s g e l s f o r the p r e p a r a t i o n o f MeAPO-16 and -35 a r e : 4

16-1.0 0.33 35-1.0 1.00

QUIN HOAc QUIN HOAc

: 0.17 MeO

: 0.92 A1 0

3

: P 0 :

40

H0

: 0.50 MeO

: 0.75 A1 0

3

: P 0 :

40

H0

2

2

2

2

5

5

2

2

In g e n e r a l , higher c r y s t a l l i z a t i o n temperatures (150-200°C) and lower g e l Me f a v o r s t r u c t u r e s 16 and 17. Since these s t r u c t u r e s a r e a l s o tempiated i n the absence o f Me, a broad compositional range i s e a s i e r t o a c h i e v e . The 35 s t r u c t u r e i s f a v o r e d a t low temperatures (100°C) and higher g e l Me concentrations. Table I I I shows t y p i c a l gel and product compositions f o r MeAPO-16 and MeAPO-35. The f o u r g e l compositions shown f o r MeAPO-35 produce product compositions t h a t m i r r o r the g e l s , and demonstrate compositional l a t i t u d e f o r t h i s framework also. Despite the v a r i a t i o n i n framework composition, both the 16 and 35 s t r u c t u r e - t y p e s show c h a r a c t e r i s t i c r a t i o s o f approximately 10 and 9, r e s p e c t i v e l y , f o r the number o f T 0 u n i t s per template. These values are completely c o n s i s t e n t with s t r u c t u r a l knowledge. For the 16 s t r u c t u r e (1_9) there are 10 T 0 per cage and room f o r 1 QUIN i n each. For the 35 s t r u c t u r e there a r e 9 T0 per cage and room f o r 1 QUIN i n each. The remaining s t r u c t u r e templated by QUIN, 17, a l s o possesses 9 T 0 per QUIN but 2 QUIN occupy each l a r g e cage. 2

2

2

2


23.

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337


Table I I I . Elemental Compositions o f Gel and Product f o r T y p i c a l MeAPO-16 and -35 36 5

36 36 36 36 > 5

(where the amount o f 36-type seed i s equal t o 10 wt.% o f s t a r t i n g oxides). Under these c o n d i t i o n s Mg and Zn form pure MeAPO-36 more r e a d i l y than Co and Mn. Higher gel P r N l e v e l s are e f f e c t i v e i n 3


338

ZEOLITE SYNTHESIS

f a v o r i n g the 36 s t r u c t u r e , and seeding o f the r e a c t i o n mixture with a 36 s t r u c t u r e - t y p e o f any composition a l s o a c c e l e r a t e s n u c l e a t i o n o f 36. Product analyses o f t y p i c a l MeAPO-36 are shown in Table IV. V a r i a t i o n i n the framework composition o f the 36 s t r u c t u r e can be induced by changing the gel composition. The packing d e n s i t y o f the P r N stays r e l a t i v e l y constant a t 1 P r N per 20 T 0 , a value t h a t i s e s s e n t i a l l y i d e n t i c a l t o t h a t o f P r N i n the 5 s t r u c t u r e - t y p e . 3

3

2


3

Table IV. Elemental Compositions o f Gel and Product f o r T y p i c a l MeAPO-36 ( T 0 Formula, Anhydrous B a s i s ) 2

P r N : ( Me

Al

3

Gel Products

Gel Product

0.042 0.038 0.060 0.045

0.458 0.460 0.436 0.465

Ρ )0

2

T0 /R

Framework Charge

2

ΜΑΡ0 MnAPO CoAPO

0.375 0.045 0.048 0.056

0.500 0.500 0.504 0.490

22 21 18

-0.044 -0.052 -0.065

MAPO

0.204 0.102 0.408 0.490 0.047 0.102 0.413 0.485

21

-0.135

(DPA). Di-n- •propylamine templates at l e a s t Di-n-propylamine s t r u c t u r e - t y p e s i n MeAPO s y n t h e s i s . This m u l t i p l i c i t y o f p o s s i b l e s t r u c t u r e s makes the j o b o f preparing one s t r u c t u r e , f r e e o f competing s t r u c t u r e s more c h a l l e n g i n g . Fortunately, other s y n t h e s i s f a c t o r s can be used t o focus the s t r u c t u r e - d i r e c t i n g e f f e c t o f the template. Such f a c t o r s as metal type, template c o n c e n t r a t i o n , metal c o n c e n t r a t i o n , c r y s t a l l i z a t i o n temperature, and seeding can be used t o i n f l u e n c e s t r u c t u r e formation. The synthesis c o n d i t i o n s observed t o f a v o r formation o f a p a r t i c u l a r s t r u c t u r e - t y p e are shown i n Table V. Table V. Trends i n Synthesis Conditions Favoring S t r u c t u r e Formation with Di-n-Propylamine Structure Type 11 31 39 41 43 46 50

Template Cone. Low Low Low High High High High

Metal Cone.

Temp. °C

Low Low High Low High High High

200 200 150 200 150 150 150

Seed X X X

S y n t h e s i s c o n d i t i o n s that y i e l d e s s e n t i a l l y pure MAPO examples f o r s i x o f these s t r u c t u r e s a r e shown i n Table V I .


23.

WILSON AND FLANIGEN


Table VI.

339


T y p i c a l Synthesis C o n d i t i o n s f o r C r y s t a l l i z a t i o n o f MAPO S t r u c t u r e s with DPA. (Molar Formula)

Type

DPA

MqO

A1 0

11 31 39 41 46 50

1.0 1.5 1.0 2.0 2.0 2.5

0.17 0.20 0.40 0.30 0.30 0.30

0.92 1.00 0.80 0.85 0.85 0.85

2

3

P 0 2

1.0 1.0 1.0 1.0 1.0 1.0

5

H0

Time Temp. Seed

50 60 40 50 50 50

24 24 24 24 168 144

2

200 150 150 200 150 150

X X

(Reactants i n c l u d e pseudo-boehmite alumina and magnesium a c e t a t e ) . T y p i c a l product analyses o f some o f these s t r u c t u r e - t y p e s a r e shown below ( T 0 formula, anhydrous b a s i s ) : 2

Species 11 39 41 46 50

DPA : ( Me 0.050 0.054 0.048 0.118 0.183

0.042 0.096 0.052 0.130 0.211

Al

Ρ )0

0.453 0.406 0.451 0.370 0.310

0.505 0.498 0.497 0.500 0.479

2

T0 /R 2

20 19 21 8 5

Framework Charge -0.032 -0.100 -0.058 -0.130 -0.253

In g e n e r a l , the s t r u c t u r e s with highest v o i d volume (lowest values o f T0 /R) are f a v o r e d by high g e l template c o n c e n t r a t i o n s . 2

Characterization Chemical A n a l y s i s . The chemical analyses o f these and o t h e r MeAPO molecular s i e v e s are c o n s i s t e n t with t e t r a h e d r a l frameworks i n which Me and A l occupy 50% o f the Τ s i t e s and P, the o t h e r 50%. A l l o f the a v a i l a b l e s t r u c t u r a l evidence on A1P0 and MeAPO a l s o supports frameworks based on a l t e r n a t i n g (Al,Me) and Ρ i n the l a t t i c e Τ s i t e s . The negative framework charge produced by such an i n c o r p o r a t i o n p a t t e r n i s balanced p r i m a r i l y by the p o s i t i v e l y charged template and, s e c o n d a r i l y , by other occluded s p e c i e s , such as H o r M e . Based on geometrical c o n s i d e r a t i o n s alone, frameworks with a Me f r a c t i o n g r e a t e r than 0.125 must have some phosphorus atoms bonded t o a t l e a s t two metal atoms through oxygen. Of the s p e c i e s d e s c r i b e d h e r e i n , examples o f s t r u c t u r e - t y p e s 20, 35, 46, and 50 f i t t h i s c r i t e r i o n . The refinement o f the data and the chemical a n a l y s i s f o r CoAP0-50 (J_9) are c o n s i s t e n t with t h i s p a t t e r n o f framework i n c o r p o r a t i o n . E l e c t r o n microprobe a n a l y s i s was c a r r i e d o u t on s e l e c t e d MeAPO samples. These samples were mounted i n epoxy r e s i n , p o l i s h e d , and 4

+

2+


340

ZEOLITE SYNTHESIS


carbon coated. Elemental analyses were determined by both energy d i s p e r s i v e and wavelength d i s p e r s i v e techniques using standards and reported c o r r e c t i o n procedures. The e l e c t r o n microprobe analyses were c a r r i e d out on i n d i v i d u a l c r y s t a l l i t e s o f t y p i c a l morphology. The r e s u l t s are shown i n Table V I I . In a l l cases, Ρ c o n s t i t u t e d approximately 50% o f the Τ atoms and (Al+Me), 50%. M u l t i p l e spot analyses (spot s i z e = 5 μπι) o f some o f the l a r g e r c r y s t a l s i n d i c a t e d compositional u n i f o r m i t y from edge t o c e n t e r with no pronounced zoning. Nhere a v a i l a b l e , bulk chemical analyses compared very f a v o r a b l y with those from the e l e c t r o n microprobe. Table V I I . Comparison o f E l e c t r o n Microprobe and Bulk Chemical Analyses f o r S e l e c t e d MeAPO Molecular Sieves Species

Normalized Elemental R a t i o

Technique*

Me 0.03 0.04

Al 0.46 0.43

Ρ 0.51 0.53

1 2

MnAP0-44

0.15 0.14 0.14

0.34 0.33 0.36

0.50 0.52 0.51

1 2 3

MAPO-47

0.09 0.13 0.11

0.39 0.37 0.39

0.51 0.51 0.50

1 2 3

CoAPO-47

0.11 0.10 0.11

0.38 0.37 0.39

0.51 0.53 0.50

1 2 3

CoAPO-5

0.03 0.03

0.47 0.46

0.51 0.51

1 2

MnAPO-11

t e c h n i q u e : U E n e r g y D i s p e r s i v e , 2=Navelength D i s p e r s i v e , 3=Bulk Chemical. X-Ray C r y s t a l l o q r a p h y . S i n g l e c r y s t a l s t r u c t u r e d e t e r m i n a t i o n s f o r the Me c o n t a i n i n g frameworks MnAP0-ll (22); CoAP0-50, CoAPO-44, CoAPSO-44, MAPSO-46, CoAP0-47 (19); and MAP0-43 (23) have been d e s c r i b e d . In a l l o f these d e t e r m i n a t i o n s the metal was found to be i n the framework. A d s o r p t i o n . The a d s o r p t i o n p r o p e r t i e s f o r s e l e c t e d A l P 0 - b a s e d m o l e c u l a r s i e v e s are summarized i n Table V I I I . The a d s o r p t i o n data are arranged f o r each s t r u c t u r e - t y p e i n o r d e r o f i n c r e a s i n g adsorbate s i z e . The l a r g e pore s t r u c t u r e - t y p e s (5, 36, 46) with pores d e f i n e d by 12-rings o f oxygen r e a d i l y adsorb neopentane ( k i n e t i c d i a . 0.62 nm). The 5 and 46 s t r u c t u r e - t y p e s have been 4



8 8 8 8 8

6 6

34 35 39 44 47

16 20

25 1 1

4 2

28 32

23 1 1

13 14

27 17 9 25 27

13 13 12

16 21 30

η-butane 0.43 0.4 22

33 31 23 35 35

18 21 21

26 31 35

0^ 0.346 0.9 -183

10

11 11 10

28

n-hexane 0.43 0.3 22

2

i sobutane 0.50 0.3 22

b) Number of tetrahedral atoms ( A l , P, Me) known, estimated from adsorption measurements.

a

2 11 11

12 13 26

neopentane 0.62 0.6 22

in ring c o n t r o l l i n g pore s i z e . When structure not

c a l c i n a t i o n at 500-600°C in

11 9 8

cyclohexane 0.60 0.5 22

(cc/100g)

a) Determined by standard McBain-Bakr gravimetric techniques after a i r . Samples activated at 350°C, 0.01 torr, prior to measurement.

10 10 or 12 10 or 12

b

2

H0 0.265 0.9 22

Adsorption Capacity

4

Typical Adsorption Pore Volumes For Selected AIP0 -Based Structure Types

Ring S i z e 12 12 12

= = = =

11 31 41

structure 5 36 46

Adsorbate Kinet ic Dia.(nm) P/Po Temp.(C)

Table VIII.



342

ZEOLITE SYNTHESIS

determined by s i n g l e c r y s t a l methods (24,19). The 5 s t r u c t u r e has a unidimensional c y l i n d r i c a l pore s t r u c t u r e with a diameter o f c a . 0.8 nm. The 46 s t r u c t u r e has a three-dimensional pore s t r u c t u r e with 12-ring channels p a r a l l e l t o the c-ax'is i n t e r s e c t i n g 8 - r i n g channels p e r p e n d i c u l a r t o t h i s a x i s . Of the medium pore s t r u c t u r e s (11,31,41), o n l y the 11 s t r u c t u r e has been p u b l i s h e d (22,25) and i t has p a r a l l e l , e l l i p t i c a l , n o n - i n t e r s e c t i n g 10-ring channels. A d s o r p t i o n data i n d i c a t e that cyclohexane i s r e a d i l y adsorbed but neopentane i s excluded. The o t h e r two s t r u c t u r e s show l e s s d i f f e r e n t i a t i o n between cyclohexane and neopentane and may, i n f a c t , have e l l i p t i c a l 12-ring pores. The small pore ( 8 - r i n g ) s t r u c t u r e s a l l adsorb oxygen but o n l y the c h a b a z i t e - t y p e s and l e v y n i t e adsorb η-butane o r n-hexane and the r a t e o f a d s o r p t i o n i s very s t r o n g l y dependent on p a r t i c l e s i z e . Larger adsorbates a r e completely excluded. The very small pore s t r u c t u r e s ( 6 - r i n g ) adsorb o n l y water and exclude oxygen. C a t a l y t i c A c t i v i t y . As shown above, the negative framework charge o f the MeAPO molecular s i e v e s as s y n t h e s i z e d i s balanced, a t l e a s t in p a r t , by the p o s i t i v e l y charged o r g a n i c template. On c a l c i n a t i o n , p r o t o n i c s p e c i e s a r e formed by the thermal decomposition o f the template. To assess c a t a l y t i c c r a c k i n g a c t i v i t y and Bronsted a c i d i t y , s e l e c t e d MeAPO s p e c i e s (Table IX) were t e s t e d f o r η-butane c r a c k i n g ( 2 6 ) . Factors i n f l u e n c i n g the measured a c t i v i t y i n c l u d e s t r u c t u r e - t y p e , metal type, and framework metal content. Comparing the l a r g e pore s t r u c t u r e s , the maximum a c t i v i t y decreases across the s e r i e s : 36 > 46 > 5. For a given s t r u c t u r e and metal type the a c t i v i t y can be v a r i e d with Table IX. Maximum η-Butane C r a c k i n g * Values ( k ) f o r S e l e c t e d MeAPO M o l e c u l a r Sieves A

Metal Structure

Fe

Mq

Mn

5 36 46

0.4 13.8 2.5

0.9

1.3 30.3 5.9

1.2 6.8

0.04-0.05 0.04-0.05 0.13-0.17

11 31 41

1.4 3.7 1.3

0.5 4.2 0.6

0.5 2.4 0.4

0.04-0.05 0.02-0.04 0.04-0.05

0.6

35.7

5.2

34 47 39

23.2 6.5

0.05

Zn

Framework Me F r a c t i o n

Co

12.5

0.08-0.10 0.12 0.09

* Samples p r e v i o u s l y c a l c i n e d i n a i r , then a c t i v a t e d i n s i t u under f l o w i n g helium a t 500°C f o r one hour. Feedstock i s 2 mole% η-butane i n helium a t 500°C.



23.

WILSON AND FLANIGEN


343

framework metal c o n c e n t r a t i o n . At comparable metal c o n c e n t r a t i o n s the 36 s t r u c t u r e e x h i b i t s c o n s i d e r a b l y g r e a t e r a c t i v i t y than the corresponding 5-type. For the medium pore s t r u c t u r e s (11,31,41) the maximum a c t i v i t y appears t o decrease somewhat across the s e r i e s : 31 > 11 = 41. Among these, the framework metal c o n c e n t r a t i o n has the most pronounced e f f e c t on the a c t i v i t y o f the 31 s t r u c t u r e - t y p e . The r e l a t i v e a c t i v i t i e s o f the v a r i o u s 34 s t r u c t u r e s show a decrease i n the maximum value f o r each metal i n o r d e r : Mg > Co > Zn > Mn > Fe. This r e l a t i v e o r d e r i n g o f the metals a l s o appears true f o r other s t r u c t u r e s , such as 36, 46, and 31, although the data a r e l e s s complete. The 39 s t r u c t u r e - t y p e excludes n-butane (based on a d s o r p t i o n data) and, a c c o r d i n g l y , shows a very low butane c r a c k i n g a c t i v i t y , c o n s i s t e n t with e s s e n t i a l l y no c a t a l y t i c a c t i v i t y due t o the external s u r f a c e . Thermal S t a b i l i t y . Most MeAPO molecular sieves e x h i b i t good thermal s t a b i l i t y , r e t a i n i n g c r y s t a l l i n i t y a f t e r a 400-600°C a i r c a l c i n a t i o n t o remove the o r g a n i c template. The u l t i m a t e thermal s t a b i l i t y depends on s t r u c t u r e - t y p e , metal type, and metal concentration. Conclusions Along with A1P0 and SAPO, the MeAPO molecular s i e v e s have extended the s t r u c t u r a l and compositional v a r i e t y found among the growing numbers o f AlP0 -based molecular s i e v e s . Both the metal and the organic template exert a primary i n f l u e n c e on s t r u c t u r e - f o r m a t i o n during s y n t h e s i s . Despite the s i m i l a r i t i e s i n the behavior o f the f i v e metals i n s y n t h e s i s , each s t i l l has a d i s t i n c t " p e r s o n a l i t y " , e.g., i n s t r u c t u r e s e l e c t i o n with a given template o r i n the r a t e o f c r y s t a l l i z a t i o n . In a d d i t i o n t o Bronsted a c i d i t y d i s c u s s e d here, p o t e n t i a l l y u s e f u l p r o p e r t i e s imparted by the presence o f metal i n framework s i t e s i n c l u d e i o n exchange and metal s p e c i f i c behavior, such as redox a c t i v i t y . 4

4

Acknowledgments The authors would l i k e t o acknowledge Brent M. Lok, C e l e s t e A. Messina and L a r r y D. V a i l f o r t h e i r c o n t r i b u t i o n s and R. L y l e Patton f o r many v a l u a b l e d i s c u s s i o n s and c r i t i c a l review o f the manuscript.

Literature Cited 1. Breck, D.W. Zeolite Molecular Sieves; Wiley: New York, 1974. 2. Flanigen, E.M.; Grose, R.W. In Molecular Sieve Zeolites-I; Advances in Chemistry Series No. 101; American Chemical Society: Washington, DC, 1971; pp. 76-101. 3. Artioli, G.; Pluth.J.J.; Smith, J.V. Acta Crystallogr. 1984, C40, 214-217.


344 4. 5. 6.


7. 8. 9. 10. 11. 12. 13. 14. 15.

16. 17. 18. 19. 20. 21. 22. 23.

ZEOLITE SYNTHESIS

Grose, R.W.; Flanigen, E.M. U.S. Patent 4 061 724, 1977. Flanigen, E.M.; Bennett, J.M.; Grose, R.W.; Cohen, J.P.; Patton, R.L.; Kirchner, R.M.; Smith, J.V. Nature (London) 1978, 271, 512-516. Wilson, S.T.; Lok, B.M.; Messina, C.A.; Cannan, T.R.; Flanigen, E.M. J. Am. Chem. Soc. 1982, 104, 1146-1147. Wilson, S.T.; Lok, B.M.; Messina, C.A.; Cannan, T.R.; Flanigen, E.M. In Intrazeolite Chemistry; Stucky, G.D.; Dwyer, F.G., Eds.; ACS Symposium Series No. 218; American Chemical Society: Washington, DC, 1983; pp 79-106. Wilson, S.T.; Lok, B.M.; Messina, C.A.; Flanigen, E.M. In Proc. Sixth International Zeolite Conference; Olson, D.; Bisio, Α., Eds.; Butterworths: Guildford, Surrey, UK, 1984; pp. 97-109, 1985, pp 97-109. a) Lok, B.M.; Messina, C.A.; Patton, R.L.; Gajek, R.T.; Cannan, T.R.; Flanigen, E.M. U.S. Patent 4 440 871, 1984. b) Ibid. J. Am. Chem. Soc. 1984, 106, 6092-3. Lok, B.M.; Marcus, B.K.; Flanigen, E.M. U.S. Patent 4 500 651, 1985. Wilson, S.T.; Flanigen, E.M. U.S. Patent 4 567 029, 1986. b) Messina, C.A.; Lok, B.M.; Flanigen, E.M. U.S. Patent 4 544 143, 1985. Wright, L.J.; Milestone, N.B. Eur. Pat. Appl. 0 141 662, 1985. Pyke, D.R.; Whitney, P.; Houghton, H. Applied Catalysis 1985, 18, 173-190. Bond, G.C.; Gelsthorpe, M.R.; Sing, K.S., Chem. Soc., Chem. Commun. 1985, 1056-7. Flanigen, E.M.; Lok, B.M.; Patton, R.L.; Wilson, S.T. Pure & Appl. Chem. 1986, Vol. 58; No. 10, pp 1351-58. Flanigen, E.M.; Patton, R.L.; Wilson, S.T. In Innovation in Zeolite Materials Science; Grobet, P.J.; Mortier, W.J.; Vansant, E.F.; Schulz-Ekloff, G., Eds.; Stud. in Surf. Sci. and Cat. Vol. 37; Elsevier: New York, 1988; pp 13-27. Bennett, J.M.; Dytrich, W.J.; Pluth, J.J.; Richardson, J.W., Jr.; Smith, J.V. Zeolites 1986, 6, 349-61. Ibid., in press, 1989. Ito, M.; Shimoyama, Y.; Saito, Y. Acta. Crystallog. 1698, C41. 1698-1700. Bennett, J.M.; Marcus, B.K. In Innovation in Zeolite Materials Science; Grobet, P.J.; Mortier, W.J.; Vansant, E.F.; Schulz-Ekloff, G., Eds.; Stud, in Surf. Sci. and Cat. Vol. 37; Elsevier: New York, 1988; pp 269-79. d'Yvoire, F. Bull. Soc. chim. France 1961, pp 1762-76. Pluth, J. J.; Smith, J. V. Acta. Cryst. 1986, C42, 1118-20. Pluth, J. J.; Smith, J. V.; Richardson, J. W., Jr. J. Phys. Chem. 1988, 92, 2734-38. Pluth, J.J.; Smith, J.V.; Bennett, J.M. J. Am. Chem. Soc., in press.


23. WILSON AND FLANIGEN MeAPO Molecular Sieves

Bennett, J.M.; Cohen, J.P.; Flanigen, E.M.; Pluth, J.J.; Smith, J.V. In Intrazeolite Chemistry; Stucky, G.D.; Dwyer, F.G., Eds.; ACS Symposium Series No. 218; American Chemical Society: Washington, DC, 1983; pp 109-18. 25. Bennett, J.M.; Richardson, J.W., Jr; Pluth, J.J.; Smith, J.V. Zeolites 1987, 7, 160-2. 26. Rastelli, H., Jr.; Lok, B.M.; Duisman, J.Α.; Earls, D.E.; Mullhaupt, J.T. Can. J. Chem. Eng. 1982, 60, 44-9. RECEIVED December 22, 1988 Downloaded by UNIV OF MICHIGAN ANN ARBOR on February 18, 2015 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch023

24.

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Synthesis and Characterization of Metal Aluminophosphate Molecular

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