Synthesis of Microporous Silicoaluminophosphates in HexanolWater

Chapter 22

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on March 30, 2016 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch022

Synthesis of Microporous Silicoaluminophosphates in Hexanol—Water Biphasic Systems Johan A. Martens, Bart Verlinden, Machteld Mertens, Piet J. Grobet, and Peter A. Jacobs Laboratorium voor Oppervlaktechemie, Katholieke Universiteit Leuven, Kardinaal Mercierlaan 92, B-3030 Heverlee, Belgium

Microporous silicoaluminophosphates are synthesized in the hexanol-water biphasic system using tetrapropylammonium hydroxide (Pr N-OH) and dipropylamine (Pr N) as templates. The outcome of the crystallization depends on phase separation and agitation during synthesis. MCM-1 crystallizes in a broad range of conditions and in the presence of Pr N-OH or Pr N. The mechanism of Si substitution in and the ion-exchange and catalytic properties of MCM-1 materials are influenced by the template used. A silicon-free homolog of MCM-1 exists and was formerly denoted as A1PO -H . The structural identity of MCM-1 and AlPO4-H3 is demonstrated. The crystallization of AlPO -H from an inorganic synthesis mixture is an example of the growth of microporous aluminophosphates in absence of template. The intracrystalline void structure of MCM-1 is determined with the decane test. 4

2

4

2

4

3

4

3

C r y s t a l l i n e microporous silicoaluminophosphates have been patented as SAPO-n (1) o r MCM-n (2) m a t e r i a l s . The SAPO m a t e r i a l s c r y s t a l l i z e from an aqueous medium i n the presence o f organic templates, t h e MCM m a t e r i a l s from a b i p h a s i c medium, u s i n g s i m i l a r templates. Most o f the a c t u a l l y known MCM's and SAPO's a r e c r y s t a l l o g r a p h i c a l l y d i f f e r e n t apart from SAPO-34, SAPO-44, SAPO-47 and MCM-2 which have t h e chabasite topology (2., 3) . The s t r u c t u r e o f other MCM m a t e r i a l s i s p r e s e n t l y unknown. From t h e a v a i l a b l e l i t e r a t u r e i t appears t h a t t h e S i , A l and Ρ o r d e r i n g i n the two groups o f microporous silicoaluminophosphates should be different. The anhydrous chemical composition o f SAPO-n corresponds t o ( 1 ) :

R 0-0.3

(SiO ) (A10 ) (PO ) 2 χ 2 y 2 ζ 0097-6156/89/0398-0305$07.00A) ο 1989 American Chemical Society

Occelli and Robson; Zeolite Synthesis ACS Symposium Series; American Chemical Society: Washington, DC, 1989.

(1)

306

ZEOLITE SYNTHESIS


i n which R i s t h e template molecule. A SAPO-n m a t e r i a l can be considered t o o r i g i n a t e from S i s u b s t i t u t i o n i n t o an h y p o t h e t i c a l aluminum phosphate framework (4,5). The predominant substitution mechanisms are S i f o r Ρ (mechanism 2) and two S i atoms f o r one A l and one Ρ simultaneously (mechanism 3 ) . S i s u b s t i t u t i o n f o r A l (mechanism 1) does not occur with SAPO's (4). The negative charge o f a SAPO i s , t h e r e f o r e , p r o p o r t i o n a l t o the mole f r a c t i o n o f S i i n c o r p o r a t e d v i a mechanism 2, as mechanism 3 does not c r e a t e any l a t t i c e charge. The general anhydrous formula o f MCM-n i s (2): R ν

m+ + nM (A10 ) (PO ) (SiO ) Ν x/m 2 1-y 2 1-x 2 x+y y/n

(2)

When t h e i n c o r p o r a t i o n o f S i i s again considered as a replacement o f A l and/or Ρ i n an h y p o t h e t i c a l aluminum phosphate l a t t i c e , the MCM formula precludes isomorphic substitution v i a mechanism 3 and allows only f o r mechanism 1 and 2 t o occur. According t o the MCM formula, Si0 t e t r a h e d r a r e p l a c e A 1 0 ~ and i n t r o d u c e p o s i t i v e framework charge, which i s n e u t r a l i s e d by t h e anions N ~ or r e p l a c e s POp and c r e a t e s negative framework charge, which i s n e u t r a l i s e d by the c a t i o n s M . As a result o f these suggested differences i n isomorphic s u b s t i t u t i o n mechanism, SAPO and MCM m a t e r i a l s should have different ion-exchange and catalytic p r o p e r t i e s . SAPO's a r e c a t i o n exchangers and p o t e n t i a l Br0nsted a c i d c a t a l y s t s . MCM s a r e expected t o be c a t i o n and/or anion exchangers and a r e p o t e n t i a l Bronsted a c i d , Bronsted base o r Bronsted acid/base c a t a l y s t s . In t h i s work the p o t e n t i a l o f b i p h a s i c s y n t h e s i s mixtures f o r t h e s y n t h e s i s o f microporous s i l i c o a l u m i n o phosphates is investigated. The influence of e m u l s i f i c a t i o n o f the s y n t h e s i s mixture, a g i t a t i o n and temperature on t h e c r y s t a l l i z a t i o n i s s t u d i e d . The s t r u c t u r a l i d e n t i t y o f MCM-1 and A1P0^-H , which i s an aluminum phosphate hydrate t h a t c r y s t a l l i z e s i n absence of template, i s demonstrated. S p e c i a l a t t e n t i o n i s p a i d t o t h e mechanism o f S i s u b s t i t u t i o n i n MCM-1, t o i t s catalytic activity and i t s intracrystalline void structure. 2

2

n

+

m+

7

3

Experimental Materials. The components o f t h e b i p h a s i c s y n t h e s i s mixture were hexanol (HEX), tetraethyl orthosilicate (TEOSi), orthophosphoric a c i d (85%), Pr^N and Pr N-0H (25%), a l l from Janssen Chim., pseudoboehmite ( V i s t a , 70% A 1 0 , 30% H 0) and water. These compounds were mixed i n the f o l l o w i n g way. To hexanol f i r s t TEOSi was added and subsequently phosphoric acid, pseudoboehmite, the template and water. The s y n t h e s i s mixtures were t r a n s f e r r e d i n t o autoclaves with a c a p a c i t y o f 120 ml. A g i t a t i o n was performed by r o t a t i n g t h e autoclaves a t 50 4

2

3

2


22.

MARTENS ET AL.

Synthesis of Microporous Silicoaluminophosphates

307

rpm. A f t e r c r y s t a l l i z a t i o n the s l u r r i e s were f i l t e r e d , and the s o l i d products washed and d r i e d . A 1 P 0 - H was prepared according t o experiment No.3 of r e f . 6 . From pseudoboehmite, phosphoric a c i d and water a 100 ml aqueous s o l u t i o n c o n t a i n i n g 1 0 g of A I 2 O 3 and 38 g of Ρ ° 5 was prepared. T h i s s o l u t i o n was d i l u t e d seven times and r e f l u x e d under vigorous s t i r r i n g d u r i n g 3 h. A 1 P 0 - H was recovered by f i l t r a t i o n , washing and d r y i n g . 4

3

2


4

3

Methods. X-ray powder d i f f r a c t i o n (XRD) p a t t e r n s were recorded u s i n g a modified Siemens type F d i f f r a c t o m e t e r , automated and equipped with a McBraun p o s i t i o n s e n s i t i v e d e t e c t o r (22). Scanning e l e c t r o n micrographs were taken with a P h i l l i p s instrument. MAS NMR s p e c t r a were obtained with a Bruker 400 MSL spectrometer. The exDerimental c o n d i t i o n s used i n the S i DEC, S i CP, Al, A 1 CP and P DEC were as follows: 2 9

2 9

2 7

2

Parameter

3 1

7

2 9

Si

DEC

MAS frequency (MHz) Pulse l e n g t h (με) R e p e t i t i o n time (s) Spinning r a t e (kHz) CP MAS contact time Decoupling (ms) Number of scans

2 7

CP

79.5 3 3 (ms)

5.2 5 3

5 1 18000 10000

31 DEC

A1

p

CP 104.2 0.6 0.1 3 0.5

161.9 4 10 5 1 48

3000

Infrared spectra were recorded on a PE-580B instrument with data s t a t i o n . L a t t i c e v i b r a t i o n s p e c t r a were obtained u s i n g the KBr technique. Hydroxyl s p e c t r a were scanned on s e l f - s u p p o r t i n g wafers of the samples mounted i n a vacuum c e l l . S p e c t r a l averaging was u s u a l l y 9 times. The as-synthesized m a t e r i a l s were converted into b i f u n c t i o n a l c a t a l y s t s by h e a t i n g i n i n e r t atmosphere at 723 K, impregnation with P t ( N H ) C l s o l u t i o n t o o b t a i n a 1% by weight l o a d i n g with Pt and a c t i v a t i o n i n f l o w i n g oxygen and hydrogen a t 673 K. A d e s c r i p t i o n of the r e a c t o r used f o r decane conversion was g i v e n p r e v i o u s l y (7) . The H /decane molar r a t i o i n the feed was 100 and W/F was 2 kg h mole" . The use of the catalytic conversion of decane t o c h a r a c t e r i z e the v o i d volume of microporous c r y s t a l s was d e s c r i b e d p r e v i o u s l y (8-10). 3

4

2

2

1

Q

R e s u l t s and D i s c u s s i o n Influence of A g i t a t i o n and Synthesis Temperature of a Two Phase System. A s y n t h e s i s mixture with the f o l l o w i n g molar composition per mole of A 1 0 : 2

(HEX)

4 > 2 8

(TEOSi)

0 > 3 6

(P 0 ) 2

5

0 f 7 5

3

(Pr N) 2

1 > 0

3(H 0) 2

3 0

.

7 5



308

ZEOLITE SYNTHESIS

i s a two phase system which does not e m u l s i f y . I t w i l l be f u r t h e r denoted as mixture A. I t was autoclaved under d i f f e r e n t c o n d i t i o n s o f temperature, time and a g i t a t i o n . The c r y s t a l l i z a t i o n products obtained a r e l i s t e d i n Table I. MCM-1, MCM-9, SAPO-11 and mixtures t h e r e o f were obtained depending on t h e nature o f t h e hydrothermal treatment (Table I) . In Figures 1-3 t h e XRD p a t t e r n s o f the r e s p e c t i v e phases a r e compared t o l i t e r a t u r e data. The p a t t e r n s o f MCM-1 and SAPO-11 a r e i n agreement with l i t e r a t u r e . Some o f t h e l i n e p o s i t i o n s i n t h e p a t t e r n o f MCM-9 a r e s h i f t e d with respect t o data from t h e patent literature and supplementary diffractions o f medium i n t e n s i t y a r e found a t 2Θ v a l u e s o f 6.7 and 13.5. Table I . Influence o f Temperature, Time and A g i t a t i o n on the Nature o f t h e C r y s t a l l i z a t i o n Products from Mixture A Exp ». T No. (KÎ

a

x

1 2 3 4 5 6

_

-

298 298

-

298

-

7 8 9 10 11 12 298 13 298 14 298 15 16 17 18 19

-

T t ( κ ί (R) 2

Agit. 4 (K) (h) T

2

(K?

\h 24 24 24 24

403 423 403 418 473 403

24 24 24 24 48 24

443 473 448 458

-

-

403 403 403 393 393 403 403 403 408 408 423 423 458

24 24 24 24 24 24 24 24 24 24 24 48 48

443 443 443 443 443 458 458 458 458 473 473 473

24 72 72 24 96 24 24 24 24 24 24 120

-

-

458 24

-

-

458 24

_

-

_

-

b

Product

Y Y Y Y Y Y

MCM-1 MCM-l+SAPO-11 MCM-1 MCM-1 MCM-l+SAPO-11 MCM-1

N N N N N N N N N N N N N

MCM-9+U MCM-l+SAPO-11 MCM-l+SAPO-11 MCM-1+U MCM-1+U MCM-l+SAPO-11 SAPO-11 SAPO-11 SAPO-11 SAP0-11+MCM-1 MCM-l+SAPO-11 MCM-l+SAPO-11 MCM-l+SAPO-11

Purity (%)

d

d d

c

100 50+50 100 100 60+40 100 70 90+10 60+40 60 30 80+20 80 60 60 70+30 70+30 50+50 60+40

a, T(emperature, t ( i m e ) , using a temperature i n c r e a s e o f 0.1 K s " between two T^ values, t ^ O h; b, Y ( e s ) , N(o) ; c, from XRD; d, u n i d e n t i f i e d phase. 1

When synthesis mixture A i s agitated, MCM-1 c r y s t a l l i z e s as a pure phase i f t h e temperature i n t h e first step o f t h e hydrothermal treatment i s low (Nos.1,3,4 and 6 ) . When t h i s temperature i s 423 Κ o r higher, c o - c r y s t a l l i z a t i o n o f SAPO-11 i s observed (Nos.2 and 5) . MCM-9 was obtained under s t a t i c c o n d i t i o n s a f t e r h e a t i n g a t 403 Κ and a t 443 Κ f o r one day (No.7). When the h e a t i n g p e r i o d a t the second temperature i s prolonged MCM-9 i s transformed i n t o a mixture o f MCM-1 and SAPO-11


22. MARTENS ET AL.


309

(Nos.8 and 9 ) . MCM-1, SAPO-11 o r a mixture o f both were obtained i n a l l other syntheses performed without agitation (Nos.10-19). The c r y s t a l l i z a t i o n o f SAPO-11 seems t o be favoured g e n e r a l l y when a high temperature step (>443 K) i s i n v o l v e d (Nos.12-19) o r a f t e r prolonged h e a t i n g a t 443 K (Nos. 8 and 9). I t seems t h a t MCM-9 and MCM-1 a r e unstable with respect t o SAPO-11 and accordingly the following successive phase t r a n s f o r m a t i o n s must occur:


MCM-9 -> MCM-1 -> SAPO-11. The importance o f s t i r r i n g o f b i p h a s i c systems d u r i n g s y n t h e s i s becomes apparent when comparing t h e r e s u l t s from experiments Nos.l and 7. Under s t a t i c c o n d i t i o n s MCM-9 c r y s t a l l i z e s (No.7) while a f t e r a g i t a t i o n MCM-1 i s obtained (No.l). A SEM photograph o f MCM-1 No.l i s shown i n F i g u r e 4. The MCM-1 c r y s t a l s a r e about 1 μία. l a r g e . The p i c t u r e a l s o shows a high degree o f c r y s t a l l i n i t y and homogeneous morphology o f the c r y s t a l s . Synthesis i n non-Emulsifying C o n d i t i o n s with P r N usiner I n c r e a s i n g Amounts o f S i . Mixtures were prepared "with the f o l l o w i n g molar composition : 2

(HEX)

4 > 2 8

(Α1 Ο ) 2

3

1 β 0 0

(P 0 ) 2

5

0 e 7 5

(Pr N) 2

l e 0 3

(Η Ο) 2

3 0

.

7 5

and c o n t a i n i n g v a r i o u s amounts o f TEOSi. The amount of hexanol had t o be increased when more than 0.8 mole of TEOSi were used. A l l mixtures were s t i r r e d d u r i n g the hydrothermal treatment. The products obtained a r e l i s t e d i n Table I I . When no TEOSi was added t o the s y n t h e s i s mixture, ALPO-11 was obtained (Nos.20 and 21). With 0.095 mole o f TEOSi, t h e same c r y s t a l l i n e phase was obtained and denoted as SAPO-11, although the i n c o r p o r a t i o n o f S i i n t h e m a t e r i a l was not v e r i f i e d (No. 22). Pure MCM-1 c r y s t a l s were obtained when t h e amount o f TEOSi was between 0.36 and 0.65 mole per mole Al^O^ (Nos. 4,24-28) . With higher amounts o f TEOSi c o - c r y s t a l l i z a t i o n o f MCM-1 with an u n i d e n t i f i e d phase (Sample No.29) o r with SAPO-11 (Samples Nos.30 and 31) o r p o o r l y c r y s t a l l i n e MCM-1 (Sample No.32) was obtained. Thus, under the present experimental c o n d i t i o n s , t h e S i content o f t h e mixture f o r MCM-1 c r y s t a l l i z a t i o n cannot be v a r i e d widely. Synthesis i n E m u l s i f y i n g Conditions with Pr N-OH. The results o f t h e syntheses performed withr mixtures c o n t a i n i n g Pr N-OH a r e presented i n Table I I I . The d i f f e r e n t molar r a t i o s o f the components o f the s y n t h e s i s mixture were v a r i e d around those given i n t h e o r i g i n a l patents on MCM-1 (11) , MCM-3 (12) and MCM-4 (13) s y n t h e s i s . MCM-1 was obtained i n a l l experiments (Nos.3336). In experiment No.34, t r a c e s o f other u n i d e n t i f i e d c r y s t a l l i n e phases have c o - c r y s t a l l i z e d . The s y n t h e s i s mixture i n a l l i n s t a n c e s was an emulsion. With t h i s s y n t h e s i s mixture t h e r e seems t o be 4

4


310

ZEOLITE SYNTHESIS

d(nm)

No 6 V i


0.976 0.695 0.657 0.490 0.428 0.341 0. 308 0.295 0.291 0.269

Ref. 11 I d(nm) 0

33 100 77 40 80 47 66 16 19 37

0.967 0.686 0.649 0.486 0.425 0.339 0. 306 0.293 0.289 0.268

m vs s s-vs vs m vs w w π

F i g u r e 1. XRD p a t t e r n o f MCM-1 sample No.6 and comparison o f the l i n e p o s i t i o n s and i n t e n s i t i e s the data from r e f . 1 1 .

d(nm)

No 7 I/Io

1.650 1.084 0.948 0.824 0.670 0.629 0.568 0. 550 0.489 0.438 0.417 0. 395 0.386 0. 380 0. 361 0. 340 0. 330 0.318 0.313 0. 308 0. 297 0.269

100 32 44 43 28 28 46 25 30 29 24 71 43 27 25 26 35 22 31 31 30 22

with

Ref d(nm)

25 I/Io

1. 641 1. 084 0. 933 0. 820 0. 668 0 617 0 565 0 546 0 474 0 434 0 421 0 394 0 383 0 377 0 359 0 339 0 328 0 316 0 .309 0 .303 0 .295 0 .263

100 7 15 31 8 14 13 5 14 15 54 43 25 20 9 6 32 10 14 9 19 7

F i g u r e 2. XRD p a t t e r n o f MCM-9 sample No.7 and comparison o f the l i n e p o s i t i o n s and i n t e n s i t i e s the data from ref.22.


with


22. MARTENS ET AL.


d (nm)

I/Io

d(nm)

I/Io

1.097 0.940 0.665 0.568 0.437 0.424 0.402 0.392 0. 386 0.308

38 54 40 33 58 100 55 78 58 30

1.085 0.931 0.666 0.564 0.432 0.423 0.400 0.393 0. 383 0. 302

34 49 16 30 50 100 58 75 67 9

Figure 3. XRD p a t t e r n o f SAPO-11 sample No.13 and comparison o f the l i n e p o s i t i o n s and i n t e n s i t i e s with the data from r e f . l .

F i g u r e 4. Scanning e l e c t r o n micrograph o f MCM-1 No.l.

sample


311

312

ZEOLITE SYNTHESIS

no i n f l u e n c e o f a g i t a t i o n on the c r y s t a l phase obtained. The morphology o f the MCM-1 c r y s t a l s obtained with P r N OH i s shown i n F i g u r e 5. The s i z e o f t h e c r y s t a l s i s around 1 μπι. The nature o f the template ( P r N o r Pr N-OH) a l s o seems unable under these c o n d i t i o n s t o i n f l u e n c e the morphology and dimensions o f MCM-1 c r y s t a l s (Figures 4 and 5 ) . 4

2

4

Table I I . C r y s t a l l i z a t i o n Products from S t i r r e d Mixtures with Molar Compostion per Mole o f A 1 0 (HEX) (TEOSi) ( P O ) (Pr N) (H O) 2


4 e 2 8

x

2

5

0 e 7 5

2

l e 0 3

a

Exp. TEOSi T n T t T t T t No. χ (K) (Kj (fi) (KT (fi) (K) (h) 2

20 21 22 23 4 24 25 26 27 29 3 0

0 0 0.095 0.24 0.36 0.39 0.42 0.49 0.51 0.65 0.81 0.84 0.97 1. 13

d

H

d 32 3 1

d

298 298 298 298 298 298 298 298 298 298 298 298 298 298

418 408 408 408 418 403 403 403 403 403 403 418 403 403

2

3

24 24 24 24 24 24 24 24 24 24 24 24 24 24

458 458 458 458 458 448 448 448 448 448 448 458 448 448

3

24 96 96 96 24 24 24 24 24 24 24 24 24 24

4

ALPO-11 ALPO-11 SAPO-11 MCM-l+SAPO-11 MCM-1 MCM-1 MCM-1 MCM-1 MCM-1 MCM-1 MCM-1 + U MCM-l+SAPO-11 MCM-l+SAPO-11 MCM-1+AM

- - - 24458

-

24 24 24 24 24

-

3 0 e 7 5

Product

4

458 458 458 458 458

3

2

b

-

458 24 458 24

C

a, T(emperature), t ( i m e ) , u s i n g a temperature i n c r e a s e o f 0.1 K s " between two T^ v a l u e s ; b, u n i d e n t i f i e d phase; c, amorphous; d, with (HEX) = 5.14. 1

Table I I I . Synthesis with Pr N-OH under S t i r r i n g

3

4

Ref. 11 Exp. No. 1 HEX TEOSi 2°5 A1 0 Pr NOH H0 P

2

4

9

3

4.38 0.36 °1.00 0.77 42.2 7 5

Τ (Κ) 433 t (h) 72 MCM-1

11 3

12 1

13 1

_ 33

34

35

6.0 0.49 1.02 1.00 1.06 57.7

8.6 0.70 1.46 1.00 1.51 82.4

3.8 0.31 1.18 1.00 0.67 39.2

4.38 1.07 0.75 1.00 0.77 60.2

8.6 0.70 1.46 1.00 1.21 88.3

3.8 0.31 1.19 1.00 0.67 48.9

453 168

423 72

423 120

423 192

MCM-1

423 168

MCM-3 MCM-4

_

448 72

_ b

_ 36 3.8 0.31 1.19 1.00 0.67 48.9 423 192

MCM-I MCM-1 MCM-1 MCM-1 e

a, a l l s y n t h e s i s mixtures were e m u l s i f i e d ; b, under s t a t i c c o n d i t i o n s ; c, c o n t a i n i n g t r a c e o f u n i d e n t i f i e d phase.



22.

MARTENS ET AL.


F i g u r e 5. Scanning e l e c t r o n micrograph of MCM-1 No.34.

sample


313

314

ZEOLITE SYNTHESIS

C h a r a c t e r i z a t i o n of A1P0 -H and MCM-1. In 1961 d'Yvoire reported on the s y n t h e s i s o~f aluminum phosphate hydrates (6). Α1Ρ0 -Η^ i s of p a r t i c u l a r i n t e r e s t among these m a t e r i a l s . L i t e r a t u r e data on the XRD l i n e p o s i t i o n s and r e l a t i v e i n t e n s i t i e s f o r A1P0 -H and MCM-1 a r e c o l l e c t e d i n F i g u r e 6. The m a t e r i a l s show i d e n t i c a l XRD p a t t e r n s and thus should have the same s t r u c t u r e type. I n f r a r e d spectroscopy o f the l a t t i c e v i b r a t i o n s o f A1P0 -H and MCM-1 synthesized with Pr N-OH and P r N are shown i n F i g u r e 7. The i d e n t i t y o f t h e s t r u c t u r e s i s a l s o c l e a r from those data. The A 1 , A 1 CP and P MAS NMR s p e c t r a o f A1P0.-H are shown i n F i g u r e 8. A sharp A 1 l i n e i s observed a t 41.2 ppm. In aluminum phosphates A 1 l i n e s i n the range 41-29 ppm are a s c r i b e d t o t e t r a h e d r a l l y co-ordinated A l (14) . An a d d i t i o n a l A 1 s i g n a l appears with maxima a t -11, -16, -19 and -24 ppm. T h i s s i g n a l according t o i t s p o s i t i o n can be assigned to octahedrally co-ordinated aluminum. The 41 ppm l i n e and those i n the range -11 t i l l -26 ppm are a l s o v i s i b l e under CP, i n d i c a t i n g t h a t protons ( s t r u c t u r a l water) are i n the v i c i n i t y o f A l . The aluminum phosphate hydrates v a r i s c i t e and m e t a v a r i s c i t e have s t r u c t u r e s composed o f a l t e r n a t i n g A l and P, with A l and Ρ exhibiting octahedral and tetrahedral co ordination, respectively (15,16). The formula of v a r i s c i t e and m e t a v a r i s c i t e i s A1P0 .2H 0. The two waters of h y d r a t i o n occupy c i s p o s i t i o n s i n the c o - o r d i n a t i o n sphere o f aluminum. With m e t a v a r i s c i t e the A 1 MAS NMR chemical s h i f t i s -13.2 ppm (14) and with v a r i s c i t e i t i s -12.5 (17), which i s i n the range found f o r A1P0 -H . With A1P0 -H the shape o f the o c t a h e d r a l A1 line suggests the presence o f a w e l l - d e f i n e d o c t a h e d r a l A l complex d e v i a t i n g from a x i a l c y l i n d r i c a l symmetry â n d which i s subjected t o quadrupolar i n t e r a c t i o n . The A1 l i n e s i n the range from -11 t i l l -24 ppm can be assigned to A l c o n t a i n i n g two water molecules i n c i s p o s i t i o n i n i t s octahedral c o - o r d i n a t i o n s h e l l . The chemical formula of A l P 0 - H o i s A1P0 .1.50H 0 (6,18). A c c o r d i n g l y , not every A l atom can take two water molecules i n i t s coordination shell. This necessitates the presence o f tetrahedral aluminum, justifying the 41.2 ppm A1 s i g n a l . The r a t i o o f the i n t e n s i t y o f the l i n e a t 41.2 ppm t o the sum o f those between -11 and -24 ppm i s 1.00 ± 0.05. Therefore, the s t r u c t u r e should c o n t a i n an equal amount o f o c t a h e d r a l l y and t e t r a h e d r a l l y co-ordinated A l . From the 1.50 mole o f h y d r a t i o n water, only 1.00 mole i s i n the c o - o r d i n a t i o n s h e l l o f A l , corresponding t o twice the amount o f A l ( V I ) . The P s p e c t r a c o n s i s t o f two l i n e s a t -24 and -26 ppm with equal intensity (Figure 8) . Dense aluminium phosphates and AlPO-n m a t e r i a l s g e n e r a l l y show a s i n g l e symmetrical l i n e i n the range from -19 t i l l -30 ppm, c o n s i s t e n t with the presence o f t e t r a h e d r a l phosphorus (14) . A l P 0 - H o i s a c t u a l l y the f i r s t aluminum phosphate for which a P spectrum with two t e t r a h e d r a l l i n e s i s 4

3

4

4

4

3

4

2 7


3

2 7

2

3 1

?

2 7

2 7

2 7

4

2

2 7

4

2 7

4

3

p

2 7

4

4

2

2 7

3 1

4

31


3


22.

MARTENS ET AL.

Synthesis oj Microporous Silicoaluminophosphates

M CM 1

II

1— -M-

9

17

25

33 20

Figure 6. XRD l i n e p o s i t i o n s and r e l a t i v e i n t e n s i t i e s f o r A1P0 -H (data adapted from ref.6) and f o r MCM-1 (data from r e f . 1 1 ) . 4

3


315


316 ZEOLITE SYNTHESIS


22.

MARTENS ET AL.


317

reported. The two line spectrum could result from d i f f e r e n t c o - o r d i n a t i o n s of Ρ with A l ( I V ) and A l ( V I ) . The A1 and P MAS NMR s p e c t r a are i n agreement with the s t r u c t u r a l data a v a i l a b l e i n l i t e r a t u r e (18-20) . A1P0 -H c o n t a i n s P0 t e t r a h e d r a a l t e r n a t i n g between A10 and A 1 0 ( H 0 ) octahedra (18). When the water molecules are ignored the s t r u c t u r e can be regarded as a 4connected t e t r a h e d r a l framework, c o n t a i n i n g 6 and 4.8 two-dimensional nets j g i n t by up-down l i n k a g e s (18). The A 1 , Si, S i CP and P MAS NMR s p e c t r a of MCM-1, prepared with P r N i n experiment No.27 are shown i n F i g u r e 9. The S i s i g n a l i s very broad. Using S i CP MAS NMR i t becomes narrower and r e s t r i c t e d t o the -80 t i l l -120 ppm range, which i s t y p i c a l f o r S i i n z e o l i t e s (21) and SAPO's (22). The S i spectrum of SAPO-5, e.g., c o n s i s t s of a l i n e a t -92, ascribed to Si(4Al) goo r d i n a t i o n and -112 ppm, r e p r e s e n t i n g S i ( 4 S i ) . The Si spectrum shown i n F i g u r e 9 suggests t h a t the co o r d i n a t i o n and the T-atom p o s i t i o n s of S i i n MCM-1 are much more complex. The A 1 spectrum shows a sharp l i n e a t 41.2 ppm, a broad s i g n a l around 7 ppm and a d d i t i o n a l s i g n a l s from -11 t i l l -24 ppm. We have experienced t h a t the broad l i n e around 6 ppm a r i s e s from non-ideal s y n t h e s i s c o n d i t i o n s , when an excess of amorphous A l i s present i n the sample. Chemical a n a l y s i s (Table IV) confirms t h a t t h e r e i s an excess of A l i n the product, when the A l T-atom f r a c t i o n exceeds 50%. Apart from the 7 ppm s i g n a l , the A1 spectrum of MCM-1 i s very s i m i l a r t o t h a t of A1P0 -H . The i n t e n s i t y r a t i o of the 41.2 ppm l i n e t o the sum of the l i n e s between -11 and -24 ppm i s 1.07 ± 0.05. T h i s i n d i c a t e s t h a t w i t h i n experimental e r r o r the p r o p o r t i o n of A l ( I V ) t o Al(VI) i s f i x e d by the framework topology and does not change with the i n c o r p o r a t i o n of S i . With MCM-1, P lines a t -24 and -26 ppm are observed, as expected (Figure 9). The i n c o r p o r a t i o n of S i does not i n f l u e n c e the r e l a t i v e amounts of the two types of Ρ atoms, g i v i n g r i s e t o -24 and -26 ppm signals, respectively. The Si, A1 and P MAS NMR s p e c t r a of MCM-1 sample No.34 prepared with Pr N-0H are shown i n F i g u r e 10. Apparently, the replacement of P r N with P r N and the d i f f e r e n c e s i n chemical composition (Table IV) do not i n f l u e n c e the S i and A 1 l i n e p o s i t i o n s . The i n t e n s i t y r a t i o of the 41.2 ppm l i n e t o the sum of those between -11 and -24 ppm i s 0.98 ± 0.05. I f S i i s i n c o r p o r a t e d i n the l a t t i c e , i t does not i n f l u e n c e the p r o p o r t i o n of A l ( I V ) t o A l ( V I ) . In the P MAS NMR spectrum the most intense s i g n a l s are a t -24 and -26 ppm. S i g n a l s a t higher f i e l d (1,-7 and -19 ppm) should be assigned t o Ρ not i n c o r p o r a t e d i n the c r y s t a l s which cannot be removed by washing. The i n t e n s i t y r a t i o of the two major P lines i s again c l o s e t o u n i t y , as observed f o r A1P0 -H and MCM-1 prepared with P r N . 27

4

3 1

3

4

4

2

4

2

3

27

2 9

2 9

2

3 1

2


2 9

2 9

2 9

9 2 9

27

27

4

3 1

2 9

27

3 1

4

2

2 9

4

27

3 1

3 1

4

2


3

3


318 ZEOLITE SYNTHESIS


22. MARTENS ET AL.

Synthesis ofMicroporous Silicoaluminophosphates

319

Conditions f o r A1PQ -H and MCM-1 Synthesis. From p r e v i o u s s e c t i o n i t can "De concluded t h a t as f a r as the c o o r d i n a t i o n o f A l i s concerned, A1P0 -EU i s a h y b r i d between t h e aluminum phosphate hydrates l i k e variscite and m e t a v a r i s c i t e and t h e aluminophosphate molecular s i e v e s . I t can be expected t h a t t h e s y n t h e s i s c o n d i t i o n s under which i t c r y s t a l l i z e s w i l l a l s o be intermediate between those of hydrates and molecular sieves. L i t e r a t u r e together with t h e present new data seem t o confirm t h i s . i . PH o f G e l . According t o t h e data o f d'Yvoir (6) , A1P0 -H c r y s t a l l i z e s from i n o r g a n i c s y n t h e s i s mixtures with composition: 4

3


4

4

3

A1

p

Η

( 2°3>1.00 ( 2°5>2.73 ( 2°>Χ' x ranging from 42 t o 3,600. The pH o f t h e s o l u t i o n was i n a l l experiments lower than 2.5. Under these c o n d i t i o n s A1P0 -H i s metastable and appears i n t h e f o l l o w i n g sequence o f s u c c e s s i v e phase t r a n s f o r m a t i o n s : 4

3

amorphous -> A1P0 -H -> m e t a v a r i s c i t e and v a r i s c i t e . 4

A1P0 -H

1

4

2

->

A1P0 -H 4

3

->

Wilson e t a l . reported a f t e r 24 h h e a t i n g a t 423 Κ the s y n t h e s i s o f A1P0-5 i n the f o l l o w i n g system (23): (Pr N) 3

(Al O )

1 Q

2

3

1 0

(P O ) 2

5

l e 0

(H 0) . 2

4 0

A1P0 -H co-crystallized with A1P0-5 and m e t a v a r i s c i t e when i n the g e l t h e ( P r N ) / ( A 1 0 ) r a t i o was decreased from 1.0 t o 0.6. A concommittant decrease o f t h e i n i t i a l pH occurred from 3.0 t o 2.3. The importance o f g e l pH was f u r t h e r i l l u s t r a t e d by adding t o t h e g e l 0.5 mole o f HC1, or by i n c r e a s i n g t h e amount o f Ρ 0 ς t o 1.2 mole p e r mole A l 2 0 . A f t e r these changes, A1P0 -H c o - c r y s t a l l i z e d with AlPO-5 and A l P 0 - t r i d i m i t e , o r with metavariscite, respectively. The c r y s t a l l i z a t i o n o f MCM-1 occurs a t low pH t o o . The pH o f mixture A from which MCM-1 succèsfully c r y s t a l l i z e s (Table I) was 2.4. i i . Temperature. The c o n d i t i o n s o f temperature a t which A1P0 -H c r y s t a l l i z e s a r e i l l u s t r a t e d by t h e data o f Wilson e t a l . (23.)· A1P0 -H , v a r i s c i t e and m e t a v a r i s c i t e were formed a f t e r h e a t i n g a g e l a t 373 Κ f o r 168 h with composition: 4

3

3

2

3

2

3

4

3

4

4

3

4

Pr

N

A1

3

P

H

( 3 >1.0 ( 2°3)l.O ( 2°5>1.0 ( 2°>40A f t e r a r e a c t i o n o f 24 h a t 398 Κ A1P0 -H appears together with AlPO-5 and m e t a v a r i s c i t e . Pure AlPO-5 c r y s t a l l i z e s a t higher temperatures (423 and 473 K) . I f i n t h i s g e l P r N i s r e p l a c e d with Pr N-0H, m e t a v a r i s c i t e is obtained after 384 h of heating a t 328 K. M e t a v a r i s c i t e , A1P0 -H and v a r i s c i t e a r e formed a t 373 Κ and a r e a c t i o n time o f 168 h. A f t e r 24 h a t 398 Κ AlPO-5 4

3

3

4

4

3


320

ZEOLITE SYNTHESIS

c r y s t a l l i z e s together with A 1 P 0 - H . The use o f h i g h e r temperatures r e s u l t s i n AlPO-5 formation. Wilson e t a l . concluded that high synthesis temperatures are necessary t o overcome the tendency o f A l to be o c t a h e d r a l l y co-ordinated i n a c i d i c media (23.) . From t h e data o f Table I i t f o l l o w s t h a t t h e same r u l e applies f o r silicoaluminophosphates. When a high temperature step i s involved i n the synthesis, the crystallization o f SAPO-11 c o n t a i n i n g o n l y A l ( I V ) i s favoured over MCM-1, having A l ( V I ) next t o A l ( I V ) . iii. Agitation. Stirring i s an important synthesis parameter i n the c r y s t a l l i z a t i o n of A l P O ^ H o . We experienced t h a t f o r A 1 P 0 - H s y n t h e s i s a c c o r d i n g t o t h e r e c i p e o f d'Yvoir (6) mechanical s t i r r i n g was necessary d u r i n g r e f l u x o f t h e s y n t h e s i s mixture. Without s t i r r i n g only amorphous solids could be recovered. The c r y s t a l l i z a t i o n o f MCM-1 from b i p h a s i c mixtures which a r e not e m u l s i f i e d seems a l s o t o be favoured i f the s y n t h e s i s mixture i s s t i r r e d (Table I) .


4

4

3

3

Table IV. Chemical composition o f MCM-1 Exp. No.

Si (%)

Al (%)

Ρ (%)

Ν (%)

Template (%)

3

T-atoms/ template molecule 3

MCM-1 s y n t h e s i z e d with Pr N-OH 33 6.6 45.0 ~48.4 34 6.2 36.1 57.7 MCM-1 s y n t h e s i z e d with P r N 1 12.0 51.5 "36.5 3 9.2 54.5 36.3 25 11.8 53.6 34.6 26 12.0 53.0 35.0 27 13.3 51.5 35.2 28 18.0 48.9 33.1 4

0.88 0.74

11.7 9.8

17 22

0.38 0.55 0.64 0.59

2.7 4.0

50 33

4.6 4.3

29 29

2

a, assuming no template

degradation.

Isomorphous S u b s t i t u t i o n o f S i i n MCM-1. In Table IV the chemical composition o f some o f t h e MCM-1 m a t e r i a l s o f Tables I - I I I i s g i v e n . When MCM-1 i s s y n t h e s i z e d with Pr^N-OH t h e f r a c t i o n o f Ρ i s higher than o f A l (Nos. 33 ana 34). According t o t h e MCM formula g i v e n i n eqn. 2, MCM-1 sample No.33 should have c a t i o n - as w e l l as anionexchange c a p a c i t y , t h e l a t t e r being h i g h e s t . The Ρ content o f MCM-1 sample No.34 exceeds 50% (Table I V ) . I f amorphous Ρ present i n t h e sample (Figure 10) i s taken i n t o account, t h e a c t u a l l a t t i c e Ρ content should be lower. Anyway, S i s u b s t i t u t i o n i n t h i s s t r u c t u r e appears to occur v i a mechanism 1 and t h e m a t e r i a l should behave as an anion exchanger. When MCM-1 i s s y n t h e s i z e d with P r N , t h e A l f r a c t i o n i s c l o s e t o 50% and S i seems t o r e p l a c e Ρ (mechanism 2) . The m a t e r i a l s are, t h e r e f o r e , 2


MARTENS ET AL.



22.


321

322

ZEOLITE SYNTHESIS

c a t i o n exchangers. I n f r a r e d spectroscopy i n d i c a t e s t h a t the a s - s y n t h e s i z e d MCM-1 contains r e s i d u a l dipropylammonium c a t i o n s v i b r a t i n g a t 1460 cm" (Figure 11). P r N shows an i n f r a r e d band a t 1560 cm" . 1

2

1

Hydroxyl Groups i n A1P0^-H and MCM-1. The i n f r a r e d s p e c t r a o f t h e hydroxyl v i b r a t i o n s o f A1P0 -H and MCM-1 are shown i n F i g u r e 12. A1P0 -H does not c o n t a i n i n f r a r e d a c t i v e hydroxyl groups. In MCM-1 s y n t h e s i z e d with P r N hydroxyl groups a r e observed a t 3740 and 3670 cm" . These bands shift t o 3620 and 3450 cm" , r e s p e c t i v e l y , upon a d s o r p t i o n o f benzene, which a c t s as a hydrogen bond acceptor molecule (spectra not shown). T h i s i n d i c a t e s t h a t t h e Bronsted a c i d i t y o f t h e 3 670 cm" hydroxyls i s higher than o f t h e ones a t 3740 cm" . Therefore, t h e 3740 cm" hydroxvls should be a s c r i b e d t o s i l a n o l groups and the 3670 cm"-" bands t o b r i d g i n g Si-OHA l . The appearence o f t h e l a t t e r hydroxyl groups i n the MCM-1 m a t e r i a l s i s c o n s i s t e n t with S i substitution according t o mechanism 2. MCM-1 sample No.34 synthesized with Pr N-0H shows hydroxyl v i b r a t i o n s a t 3740 cm" and 3670 cm" . The chemical composition given i n Table IV suggests t h a t isomorphous s u b s t i t u t i o n according t o mechanism 2 does not occur i n t h i s m a t e r i a l . I f t h e 3670 cm" band represents Al-OH-Si groups, there should be a c o n t r i b u t i o n o f mechanism 2 and t h e Ρ content should be lower than 50%. An a l t e r n a t i v e e x p l a n a t i o n i s t h a t t h e 3670 cm" band i n t h i s sample represents P-OH groups, a s s o c i a t e d with the excess o f Ρ i n the sample. 3

4

4

3

3

2


1

1

1

1

1

1

4

1

1

1

1

C a t a l y t i c A c t i v i t y o f MCM-1. For s e l e c t e d MCM-1 samples the temperature a t which 5% i s o m e r i s a t i o n o f decane i s obtained i s given i n Table V. MCM-1 c a t a l y s t s a r e a c t i v e when s y n t h e s i z e d with P r N . The a c t i v i t y o f sample Nos.l and 27 i s comparable. These samples have a s i m i l a r chemical composition (Table IV) and c o n t a i n strong Br0nsted a c i d s i t e s , v i s u a l i s e d by 3670 cm" i n f r a r e d bands (Figure 12). Sample No.3 contains l e s s S i (Table IV) and i s l e s s a c t i v e . The reaction temperature necessary t o o b t a i n 5% i s o m e r i s a t i o n o f decane with MCM-1 sample No.33 prepared with Pr.N-OH i s about 100 Κ higher than with the MCM-1 prepared with Pr^N (Table V) . The very weak Br0nsted acidity i s c o n s i s t e n t with the v i r t u a l absence o f isomorphous s u b s t i t u t i o n mechanism 2 i n t h i s sample. In c o n c l u s i o n , i t seems t h a t i n MCM-1 besides the isomorphic s u b s t i t u t i o n mechanism 2, which i s found i n SAPO's, mechanism 1 can a l s o be o p e r a t i v e . In MCM-1 synthesized with Pr N-0H according t o the l a t t e r mechanism A l i s r e p l a c e d with S i . The presence o f both o c t a h e d r a l and t e t r a h e d r a l A l i n MCM-1 c o u l d be t h e reason f o r t h i s unexpected behaviour. 2

1

4



22. MARTENS ET AL.


1900

1700

1500

1300 cm"1

F i g u r e 11. I n f r a r e d spectrum o f the organic m a t e r i a l i n MCM-1 sample No.l a t 295 Κ (a) and a f t e r evacuation at 400 Κ (b).

3750

3650 cm"1

F i g u r e 12. I n f r a r e d spectrum o f the hydroxyl groups o f A1P0 -H and MCM-1 samples Nos. 1, 27 and 34. 4

3


323

324

ZEOLITE SYNTHESIS

Table V. Temperature (T &) necessary t o reach 5% i s o m e r i s a t i o n of decane over MCM-1 5

Exp. No.


MCM-1 3 1 27 MCM-1 33

T %

(K)

5

s y n t h e s i z e d with P r N 2

538 527 510

s y n t h e s i z e d with Pr N-OH 636 4

Pore f i l l i n g i n A1P0 -H and MCM-1. The MCM-1 samples s y n t h e s i z e d with Pr N=0H contain 17 t o 22 mol T-atoms per mol P r N (Table IV, Nos.33 and 34), which i s comparable t o the 26 mol T-atoms found per P r N molecule i n AlPO-5 (24) . I t i n d i c a t e s t h a t the p o t e n t i a l v o i d volume i n the MCM-1 framework i s a t l e a s t comparable t o t h a t of AlPO-5. The stoicheometry of A1P0 -H is A1P0 .1.50H O, corresponding t o 17.7 weight-% of H 0. As d i s c u s s e d above there i s 11.8 weight-% of s t r u c t u r a l water ( i n the coo r d i n a t i o n sphere of octahedral Al) and the remaining 5.9 weight-% i s z e o l i t i c water. Apparently, t h i s f r a c t i o n i n MCM-1 can be r e p l a c e d with 10 t o 12% of P r N (Table IV, Nos.33 and 34). The template content of the MCM-1 samples synthesized with P r N i s much lower (Table IV, Nos.l, 3, 27 and 28) and consequently, the number of T-atoms per P r N molecule i s s y s t e m a t i c a l l y h i g h e r (Table IV) . As P r N i s a s m a l l e r molecule than Pr N-0H, t h i s means t h a t the v o i d volume of the MCM-1 c r y s t a l s i s only p a r t i a l l y f i l l e d with Pr^N i n these i n s t a n c e s . The chemical nature of the additional pore filling molecules was not determined. The presence of water i s most l i k e l y . I t was not v e r i f i e d whether hexanol was a l s o present i n these crystals. 4

3

—

4

4

4

4

3

4

2

2

4

2

2 2

4

Void S t r u c t u r e of MCM-1 Determined with the Decane T e s t . The r e s u l t s from the decane t e s t f o r determining the v o i d s t r u c t u r e are presented i n Table VI. The t e s t c o u l d not be a p p l i e d t o MCM-1 synthesized with Pr N-0H as t h i s m a t e r i a l i s too weakly a c i d i c . The f i r s t c r i t e r i o n allows t o d i s c r i m i n a t e between 10-and 12-MR s t r u c t u r e s (9) . MCM-1 behaves l i k e a 12-MR z e o l i t e . The second c r i t e r i o n allows t o make a ranking according t o the s i z e of the windows (10). MCM-1 i s among the most s h a p e - s e l e c t i v e 12-MR z e o l i t e s . A CI of 2.0 and 1.8 i s s i t u a t e d between t h a t of o f f r e t i t e (CI =1.8) and ZSM-12 (CI =2.2) and corresponds, t h e r e f o r e , t o a window s i z e of about 0.6 nm. Important d i f f e r e n c e s are found i n the values of c r i t e r i o n 3 and 4, i n d i c a t i n g t h a t the voids of the different m a t e r i a l s are significantly d i f f e r e n t . In t h i s respect, there seems t o be no r e l a t i o n with the S i content. According t o C r i t e r i o n 5 MCM-1 is 4



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intermediate between 10- and 12-MR z e o l i t e s . C r i t e r i a 6 t o 8 should be considered with c a u t i o n . A l l c a t a l y s t s e x h i b i t hydrogenolysis and t h e r e f o r e the a p p l i c a t i o n o f these c r i t e r i a i s not allowed (8.9). F o r MCM-1 sample No.27 which i s the most a c t i v e c a t a l y s t (Table V) and e x h i b i t s almost no hydrogenolysis, the isopentane y i e l d i s i n agreement with l a r g e pore c h a r a c t e r i s t i c s (Table VI) . The molar values obtained i n c r i t e r i o n 7 and 8 are equal i n d i c a t i n g t h a t secondary hydrocracking occurs ( 9 ) . As t h i s phenomenon i s not s t r o n g l y pronounced, the pore system c o u l d be b i - o r t r i d i m e n s i o n a l . D e f i n i t e proof f o r t h i s c o u l d be obtained i f a more a c i d i c MCM-1 c a t a l y s t were a v a i l a b l e . A1P0 -H i s an 8-MR s t r u c t u r e (18). Consequently, the l a r g e s t pore openings i n MCM-1 should a l s o be 8-MRs. The r e s u l t s o f t h e decane t e s t suggest t h a t t h e pores o f MCM1 become enlarged a f t e r c a l c i n a t i o n . 4

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Table VI. C h a r a c t e r i z a t i o n o f the Pore S t r u c t u r e o f MCM-1 u s i n g the Hydroconversion o f Decane 1

Exp. No. 27

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Zeolites 10-MR 12-MR

1. Ethvloctanes i n monobranched isomers a t 5% i s o m e r i s a t i o n (%) 7.6 8.4 7.7 < 1.0 > 5 2. 2-/5-methylnonane r a t i o a t 5% i s o m e r i s a t i o n 2.0 1.8 1.8 > 2.7 1.0-2.2 3. 3-/4-ethyloctane a t 5% i s o m e r i s a t i o n 0.6 0.7 0.9 4. 4-propylheptane i n monobranched isomers a t 75% conversion 2.6 1.4 1.8 0.0 > 0 5. Multibranched isomers a t maximum i s o m e r i s a t i o n (%) 18 27 19 3-11 >26 6. Mole isopentane/100 mole C10 cracked a t 35% c r a c k i n g * 26 * 11-21 >37 7. Mole C3/100 mole C10 cracked - mole C7/100 mole C10 cracked/2 a t 35% c r a c k i n g * 2.9 * 8. Mole C4/100 mole C10 cracked - mole C6/100 mole C10 cracked * 3.1 * *, hydrogenolysis superimposed. Wilson e t a l . have s t a t e d t h a t i n absence o f organic template molecules no microporous aluminum phosphates can be s y n t h e s i z e d (24). The s y n t h e s i s o f A1P0 -H from an i n o r g a n i c g e l i s a c l e a r exception t o t h i s statement. Aluminum-rich zeolites are g e n e r a l l y c r y s t a l l i z e d i n absence o f organic molecules. The s y n t h e s i s o f h i g h s i l i c a z e o l i t e s i n absence o f organic molecules i s very d i f f i c u l t , i n agreement with the hydrophobic nature o f 4

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t h e i r i n t r a c r y s t a l l i n e s u r f a c e . Aluminum phosphates with fully cross-linked tridimensional frameworks are moderately h y d r o p h i l i c (24). As t h e dehydrated forms o f A1P0 -H a r e very h y d r o p h i l i c (6) i t i s i n our o p i n i o n not s u r p r i s i n g t h a t t h e presence o f organic template molecules i s not r e q u i r e d . 4

3

Conclusions A1P0 -H i s t h e aluminum phosphate homolog o f MCM-1. The framework topology o f MCM-1 and A1P0 -H i s t h e same. A c h a r a c t e r i s t i c s t r u c t u r a l f e a t u r e o f A1P0 -H and MCM-1 m a t e r i a l s i s t h e presence o f an equal amount o f Al(IV) and Al(VI) i n t h e framework. A1P0 -H i s , therefore, a hybrid between t h e aluminum phosphate hydrates, c o n t a i n i n g Al(VI) and t h e aluminophosphate molecular s i e v e s , c o n t a i n i n g A l ( I V ) . F o r t h e same reason MCM-1 can be d i s t i n g u i s h e d from the SAPO-n f a m i l y o f m a t e r i a l s . In the c o - o r d i n a t i o n s h e l l o f Al(VI) i n A1P0 -H and MCM-1, two s t r u c t u r a l water molecules a r e present in cis p o s i t i o n . Phosphorus i s present i n two d i f f e r e n t and e q u a l l y abundant c o - o r d i n a t i o n s with Al(IV) and A l ( V I ) . The c o - o r d i n a t i o n and the T-atom p o s i t i o n s o f S i i n MCM-1 are complex. The isomorphous s u b s t i t u t i o n mechanisms a r e probably S i f o r A l (mechanism 1) and S i f o r Ρ (mechanism 2). MCM-1 m a t e r i a l s i n which mechanism 2 i s o p e r a t i v e a r e a c t i v e i n hydrocarbon conversion r e a c t i o n s c a t a l y s e d by Br0nsted a c i d i t y . The presence o f Al(VI) i n A1P0 -H e x p l a i n s why i t c r y s t a l l i z e s a t lower temperatures than AlPO-n m a t e r i a l s as t h e tendency o f A l t o be o c t a h e d r a l l y co-ordinated i n acid media i s only maintained a t low s y n t h e s i s temperatures. A l t e r n a t i v e l y , a t higher temperatures t h e c r y s t a l l i z a t i o n o f A1P0 -H can be favoured by decreasing the pH o f t h e g e l . F o r t h e same reason, t h e temperature and/or g e l pH a t which MCM-1 c r y s t a l l i z e s a r e lower than f o r t h e s y n t h e s i s o f SAPO's. A1P0 -H can be synthesized with t h e same templates as MCM-1, o r i n absence o f template. The s y n t h e s i s o f t h e microporous aluminum phosphate A1P0 -H from an i n o r g a n i c g e l i s a c l e a r exception t o the statement t h a t " i n absence o f organic template molecules no microporous aluminum phosphates can crystallize" (24). The c r y s t a l l i z a t i o n o f MCM-1 from b i p h a s i c mixtures which are not e m u l s i f i e d i s favoured i f the s y n t h e s i s mixture i s s t i r r e d . S t i r r i n g i s a l s o an important parameter i n t h e s y n t h e s i s o f A1P0 -H from an i n o r g a n i c g e l . I f the s y n t h e s i s mixture i s e m u l s i f i e d a g i t a t i o n seems t o be l e s s important. C a l c i n e d MCM-1 behaves c a t a l y t i c a l l y l i k e a 12-MR s t r u c t u r e with 0.6 nm pore openings. 4

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Acknowledgments JAM, PJG and PAJ acknowledge the B e l g i a n N a t i o n a l Fund f o r S c i e n t i f i c Research f o r a Research P o s i t i o n as Research Associate, Senior Research Associate and Research D i r e c t o r , r e s p e c t i v e l y . MM i s g r a t e f u l t o IWONL f o r a research grant. T h i s work has been sponsored by the Belgian Government (Dienst Wetenschapsbeleid) i n the frame o f a concerted a c t i o n on c a t a l y s i s . The authors are indebted t o H. Geerts f o r t a k i n g the NMR s p e c t r a , t o the MTM department o f K.U. Leuven f o r t h e use o f t h e scanning e l e c t r o n microscope and t o F. Pelgrims f o r t a k i n g the SEM photographs.

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4. 5. 6. 7. 8. 9. 10.

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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. Derouane, E.G.; Valyocsik, E.W.; Von Ballmoos, R. Eur. Patent Appl. 146 384, 1984. Flanigen, E.M., Lok, B.M.; Patton, R.L.; Wilson, S.T. In New Developments in Zeolite Science and Technology, Proceed. 7th Int. Zeolite Conf.; Murakami, Y; Lijima, Α.; Ward, J., Eds., Kodansha, Elsevier, Amsterdam, Oxford, New York, Tokyo, 1986, p.103. Lok, B.M.; Messina, C.A.; Patton, R.L.; Gajek, R.T.; Cannan, T.R.; Flanigen, E.M. J . Am. Chem. Soc. 1984, 106, 6092. Flanigen, E.M.; Patton, R.L.; Wilson, S.T. Stud. Surf. Sci. Catal. 1988, 37, 13. d'Yvoir, F. Bull. Soc. Chim. 1961, 372, 1762. Jacobs, P.A.; Uytterhoeven, J.B.; Steijns, M.; Froment,G.; Weitkamp, J., Proceed. 5th Int. Conf. Zeolites. Rees, L.V.C., Ed. Heyden, London, 1980, p.607. Martens, J.A.; Tielen, M.; Jacobs, P.A.; Weitkamp, J., Zeolites. 1984, 4, 94. Martens, J.A.; Jacobs, P.A., Zeolites. 1986, 6, 334. Jacobs, P.A.; Martens, J.A., In New Developments in Zeolite Science and Technology. Proceed. 7th Int. Zeolite Conf.; Murakami, Y; Lijima, Α.; Ward, J., Eds., Kodansha, Elsevier, Amsterdam, Oxford, New York, Tokyo, 1986, p.23. Derouane, E.G.; Von Ballmoos, R. Eur. Patent Appl. 146 385, 1984. Derouane, E.G.; Von Ballmoos, R. Eur. Patent Appl. 146 386, 1984. Derouane, E.G.; Von Ballmoos, R. Eur. Patent Appl. 146 387, 1984. Blackwell, C.S.; Patton, R.L. J. Phys. Chem. 1984, 88, 6135. Kniep, R.; Mootz, D. Acta Cryst. 1973, B29, 2292-4.



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16. Kniep, R.; Mootz, D.; Vegas, A. Acta Cryst. 1977, B33, 263-5. 17. Kotsarenko, N.S.; Mastikhin, V.M.; Mudrakovskii, I.L.; Shmachkova, V.P. React. Kinet. Catal. Lett. 1986, 30,2, 375. 18. Pluth, J.J.; Smith, J.V. Nature 1985, 318, 165. 19. Keller, E.B. Doctoral Thesis. ΕΤΗ Zurich, 1987. 20. Meier, W.M.; Olson, D.H. Atlas of Zeolite Structure Types, Second Edition, Butterworths, 1987, 26. 21. Engelhardt, G.; Michel, D. High-Resolution SolidState NMR of Silicates and Zeolites. John Wiley & Sons, Chichester, 1987. 22. Martens, J.A.; Mertens, M.; Grobet, P.J.; Jacobs, P.A.; Stud. Surf. Sci. Catal. 1988, 37, 97. 23. Wilson, S.T.; Lok, B.M.; Messina, C.A.; Flanigen, E.M.; in Proceed. 6th Int. Zeolite Conf., Olson, D.; Bisio, Α., Eds., Butterworths, 1984, p.97. 24. Wilson, S.T.; Lok, B.M.; Messina, C.A.; Cannan, T.R.; Flanigen, Ε.Μ., Ιn Intrazeolite Chemistry. Stucky, G.D.; Dwyer, F.G., Eds., ACS Symp.Ser.218, 1983, p.79. 25. Derouane, E.G.; Von Ballmoos, R. Eur. Patent Appl. 146 389, 1984. RECEIVED December 22, 1988


Synthesis of Microporous Silicoaluminophosphates in HexanolWater

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