[ACS Symposium Series] Zeolite Synthesis Volume 398 || Competitive Role of Organic and Inorganic Cations in Directing One-Dimensional Zeolitic Structures

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Chapter 40 Competitive Role of Organic and Inorganic Cations in Directing One-Dimensional Zeolitic Structures ZSM-48 and EU-1 Girolamo Giordano1, Janos B. Nagy, Eric G. Derouane, Nicole Dewaele, and Zelimir Gabelica Laboratory of Catalysis, Center for Advanced Materials Research, Facults Universitaires Notre Dame de la Paix, Namur, 61 Rue de Bruxelles, B-5000 Namur, Belgium The Bis-quaternary ammonium ions (e.g. hexamethonium, HM++) favour the formation of two different one-dimensional zeolites, namely ZSM-48 and EU-1. The resulting structure essentially depends on the initial aluminium content in the starting hydrogel. The stability fields for both zeolites synthesized by using various reactant compositions have been established. Zeolite ZSM-48 is prepared from a silica hydrogel containing HM++ ions and alkali cations (Li, Na, and ), in presence or in absence of Al . For a higher in i t ia l Al content and increased crystallization time, zeolite EU-1 is obtained. The critical role of hexamethonium ions and inorganic cations on the crystallization rate of ZSM-48 was systematically studied. HM++ ions favor the ZSM-48 formation by interacting electrostatically with Al negative charges and stabilizing its structure by acting as pore fillers. The s y n t h e s i s o f pure and h i g h l y c r y s t a l l i n e z e o l i t e s from a l l u m i n o s i l i c a t e hydrogels r e q u i r e s the st u d y o f the s i m u l t a n e o u s e f f e c t s o f d i f f e r e n t parameters i n v o l v e d i n the s y n t h e s i s . Most of these z e o l i t e s are prepared i n presence of organic d i r e c t i n g Current address: Dipartimento di Chimica, Universit della Calabria, Arcavacata di Rende, 1-87030 Rende (CS), Italy 0097-6156/89A)398-0587$06.00A) 1989 American Chemical Society Downloaded by UCSF LIB CKM RSCS MGMT on November 19, 2014 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch040In Zeolite Synthesis; Occelli, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. 588 ZEOLITE SYNTHESIS agents whose r o l e can be d r a s t i c a l l y i n f l u e n c e d by the a c t u a l composition of the hydrogel. Recent work has p o i n t e d out t h e predominant t e m p l a t i n g r o l e of b i s - q u a t e r n a r y ammonium ions (e.g. hexamethonium i o n s ) i n d i r e c t i n g o n e - d i m e n s i o n a l z e o l i t i c s t r u c t u r e s namely z e o l i t e s ZSM-48 and EU-1, the f i r s t r e p r e s e n t a t i v e member of the EU0 fami l y ( 1 - 4 . ) . Z e o l i t e s having ZSM-48 t o p o l o g y a l s o c r y s t a l l i z e from hydrogels c o n t a i n i n g other l i n e a r organic s t r u c t u r e d i r e c t i n g agents, such as diamines (UL) or v a r i o u s (poly)alkylamines (). Z e o l i t e ZSM-50, another member of the EU0 f a m i l y p o s s e s s i n g the topology of EU-1, a l s o c r y s t a l l i z e s i n presence of dibenzyldimethylammonium ions (2). The framework of ZSM-48 i s composed of f e r r i e r i t e -type sheets, connected i n such a s p e c i f i c way as t o generate l i n e a r 10-membered r i n g channels. The s t r u c t u r e i s a random intergrowth of the Imma-Cmcm frameworks and contains 48-T atoms per u n i t c e l l (&). Recently B r i s c o e et a l . () d e s c r i b e d the framework t o p o l o g y o f z e o l i t e EU-1. I t c o n s i s t s o f a unidimensional 10-membered r i n g channel system with s i d e pockets formed at r e g u l a r i n t e r v a l s o f f the channels. The u n i t c e l l c o n t a i n s 112-T atoms and the framework symmetry i s Cmma. The aim o f t h i s work i s t o e v a l u a t e t h e (competitive) r o l e of other i n g r e d i e n t s i n s t a b i l i z i n g p r e f e r e n t i a l l y one or the other s t r u c t u r e . The most i n t e r e s t i n g are the c a t i o n i c s p e c i e s , namely the a l k a l i and HM + + ions, p o t e n t i a l n e u t r a l i z i n g agents t o A10 2~ n e g a t i v e l y charged framework c e n t e r s . Indeed, a l k a l i c a t i o n s were shown t o p l a y an important r o l e i n the f o r m a t i o n o f many z e o l i t e s , e i t h e r as s t r u c t u r e d i r e c t o r s i n the n u c l e a t i o n p r o c e s s ( 1 . - 1 2 . ) or as s t a b i l i z i n g m i n e r a l i z e r s during growth ( 1 1 , 1 2 . ) , thereby a f f e c t i n g the f i n a l s i z e , morphology and composition of the c r y s t a l l i t e s . Besides t h e i r obvious r o l e as templates or s t r u c t u r e d i r e c t i n g agents (13.) or as s t a b i l i z i n g pore f i l l e r s Qrl!) the organic c a t i o n s w i l l a l s o compete with a l k a l i i o n s f o r the s t a b i l i z a t i o n o f the n e g a t i v e l y charged framework (1, 11,1!) . The p r e s e n t approach c o n s i s t s i n examining the s t r u c t u r e and c o m p o s i t i o n o f s e l e c t e d c r y s t a l l i n e z e o l i t e s o b t a i n e d by h e a t i n g under a p p r o p r i a t e c o n d i t i o n s hydrogels having the general composition: x M 20 y HMBr2 A l 2 0 3 60 S i 0 2 3000 H 20 by s y s t e m a t i c a l l y v a r y i n g the i n i t i a l c a t i o n i c , organic and A l content t o d e f i n e the fundamental r o l e of HM + + i o n s i n e a c h s y s t e m , a n d t o u l t i m a t e l y o p t i m i z e t h e o p e c i f i c c r y s t a l l i z a t i o n c o n d i t i o n s f o r each z e o l i t e . Downloaded by UCSF LIB CKM RSCS MGMT on November 19, 2014 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch040In Zeolite Synthesis; Occelli, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. 40. GIORDANO ET AL. Competitive Role ofOrganic and Inorganic Cations 589 Experimental A s e r i e s of hydrogels having the f o l l o w i n g molar composition : M 20 y HMBr2 A 1 2 0 3 60 S i 0 2 3000 H 20 (where HMBr 2 stands f o r hexamethonium bromide; M= L i , Na or K; 0590 ZEOLITE SYNTHESIS 3 I f 1 1 1 2 x mole A\2O3/60 S1O2 Figure 1. V a r i a t i o n of the percentage of c r y s t a l l i n i t y of z e o l i t e s ZSM-48 and EU-1 as a fu n c t i o n of the AI2O3 content i n the f o l l o w i n g precursor g e l phases: = ZSM-48 5Na 20 5HMBr2 x A l 2 0 3 60SiO 2 3000H 2O, (200C, 66 h) . = EU-1 10Na2O 10HMBr2 x A l 2 0 3 60SiO 2 3000H 2O, (200C, 120 h) . 0 = EU-1 + ZSM-48 (30%) Q = EU-1 + ZSM-48 (40%) + -quartz and c r i s t o b a l i t e . Downloaded by UCSF LIB CKM RSCS MGMT on November 19, 2014 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch040In Zeolite Synthesis; Occelli, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. 40. GIORDANO ET AL. Competitive Role of Organic and Inorganic Cations 591 A l content (expressed i n mole AI2O3 per 60 mole S1O2), i n each g e l system. Nearly 100% c r y s t a l l i n e ZSM-48 was o b t a i n e d i n A l - f r e e g e l systems. The c r y s t a l l i n i t y f u r t h e r markedly decreases u n t i l the upper l i m i t of 1 AI2O3, above which no ZSM-48 c r y s t a l s c o u l d be detected, even f o r longer r e a c t i o n times.In the A l - f r e e 10 Na 20 10 HMBr2 hydrogel, ZSM-48, c r i s t o b a l i t e and -quartz are the o n l y c r y s t a l l i n e phases detected, c o n f i r m i n g t h a t EU-1 can not be s t a b i l i z e d i n such a system (2.) . For 0.5 AI2O3 about 40% c r y s t a l l i n e EU-1 was detected along with ZSM-48 and smaller amount of c r i s t o b a l i t e and -quartz, and f o r 1 AI2O3 EU-1 and ZSM-48 are the only c r y s t a l l i n e phases. EU-1 i s the only phase present f o r 1.5 AI2O3, but over t h i s value i t s c r y s t a l l i n i t y s t a r t s t o decrease, i n agreement with the w e l l e s t a b l i s h e d i n h i b i t i n g r o l e o f l a r g e amounts o f A l i n t h e c r y s t a l l i z a t i o n r a t e of many z e o l i t e s (11). Influence of HMBr2 The amount of HM"1""1" ions i n the i n i t i a l h y d r o g e l d r a s t i c a l l y i n f l u e n c e s the nature of the z e o l i t e formed and i t s c r y s t a l l i z a t i o n k i n e t i c s . Pure and h i g h l y c r y s t a l l i n e ZSM-48 i s formed f o r a HMBr2 molar c o n c e n t r a t i o n c l o s e t o 2.5 ("Figure 2"). For h i g h e r HMB r 2 c o n t e n t s t he c r y s t a l l i n i t y shows a s l i g h t decrease, probably due to a marked m o d i f i c a t i o n of the hydrogel composition and/or of the s o l u b i l i t y of the va r i o u s r e a c t i v e s pecies, induced by the excess of organic molecules. For HM + + concentrations l y i n g between 1 and 2.5 mole, dense S1O2 pol y m o r p h i c phases coc r y s t a l l i z e w i t h ZSM-48, w h i l e f o r lower H M + + c o n c e n t r a t i o n s , e s s e n t i a l l y below 0.5 mole, ZSM-5 was found t o be predominant z e o l i t i c phase. T h i s l a t t e r o b s e r v a t i o n confirms once more t h a t Na + ions r e a d i l y i n i t i a t e the formation of 5-1 SBU i n h i g h l y s i l i c e o u s hydrogels (11,1) . Our i n v e s t i g a t i o n s l e a d us t o propose the f o l l o w i n g optimum composition t o o b t a i n 100% c r y s t a l l i n e ZSM-48 a f t e r 48 h: Na 20 2.5 HMBr2 0-0.5 A 1 2 0 3 60 S i 0 2 3000 H 20 The optimum c r y s t a l l i n i t y of EU-1 was found i n the 15-20 HM + + molar range and f o r 1.5 AI2O3 per 60 S1O2 ("Figure 3"). Furthermore we c o u l d d e f i n e more a c c u r a t e l y the appro x i m a t e g e l c o m p o s i t i o n i n which pure EU-1 c r y s t a l l i z e s with a r e l a t i v e l y f a s t r a t e : 10 Na20 17.5 HMBr2 1.5 A1 20 3 60 S i 0 2 3000 H20 Downloaded by UCSF LIB CKM RSCS MGMT on November 19, 2014 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch040In Zeolite Synthesis; Occelli, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. 592 ZEOLITE SYNTHESIS 80 -2 60 - > k. ^ 4 0 -20 -1 3 5 mole HMBr2/60 S1O2 Figure 2. V a r i a t i o n of the percentage of c r y s t a l l i n i t y of z e o l i t e ZSM-48 synthesized from:5Na 20 xHMBr2 0.5Al 20 3 60SiO 2 3000H2O gels (200 C, 66 h) , as a fu n c t i o n of HMBr2 content 0 = ZSM-48 + c r i s t o b a l i t e . 20 -5 15 25 x mole HMBT2 / 60 S1O2 Figure 3. V a r i a t i o n of percentage of c r y s t a l l i n i t y of z e o l i t e EU-1 synthesized from: 10Na2O xHMBr2 1.5Al 20 3 60SiO 2 3000H2O gels (200 C, 7 days), as a fu n c t i o n of HMBr2 content = EU-1 = EU-1 + -quartz 0 = EU-1 + ZSM-48 (t r a c k s ) . Downloaded by UCSF LIB CKM RSCS MGMT on November 19, 2014 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch040In Zeolite Synthesis; Occelli, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. 40. GIORDANO ET AL. Competitive Role ofOrganic and Inorganic Cations 593 c r y s t a l l i z a t i o n of dense phases f o r low co n c e n t r a t i o n s and general i n h i b i t i o n of c r y s t a l l i z a t i o n f o r high HM + + contents. I t i s i n t e r e s t i n g t o note t h a t between 5 and 10 HM+ + , ZSM-48 c o - c r y s t a l l i z e s with EU-1. A s p e c i f i c composition of both z e o l i t e s c o u l d not be measured but i t seems reasonable t o suppose that t h i s ZSM-48 phase i s not r i c h e r i n A l than those c r y s t a l l i z e d from S i - r i c h e r g e l s , as most of the A l i s probably u t i l i z e d t o b u i l d up the EU-1 framework. Influence of NaOH c o n c e n t r a t i o n . The minimun Na 20 content (mole/60 mole S i 0 2 ) t o i n i t i a t e the c r y s t a l l i z a t i o n o f ZSM-48 and EU-1 i s r e s p e c t i v e l y 2.5 and 7.5, w h i l e t h e h i g h e s t c r y s t a l l i n i t y f o r each z e o l i t e i s observed f o r 5 and 10 mole Na 20 r e s p e c t i v e l y ("Figure 4") . Because added as NaOH, a l a r g e r amount of N a + may a l s o i n d i r e c t l y i n c rease the c r y s t a l l i z a t i o n through the more pronounced m o b i l i z i n g e f f e c t of the OH" ions (JL2.) , but a l s o , more d i r e c t l y by s t a b i l i z i n g the f i r s t n u c l e i (IQ.,11) . The l a r g e r amount of Na + needed t o a c c e l e r a t e the growth of an A l - r i c h e r m a t e r i a l (here EU-1) suggests t h a t , i n both systems, N a + i s at l e a s t as e f f i c i e n t as HM + + i n the r o l e of counterion t o framework A l negative centers, i n agreement t o what i s u s u a l l y observed f o r z e o l i t e s s y n t h e s i z e d i n presence of both Na + and organic c a t i o n s (JUL,UL) . Note t h a t above these Na 20 optimum v a l u e s , dense phases l i k e -quartz or c r i s t o b a l i t e s t a r t t o c r y s t a l l i z e i n both systems, as alr e a d y observed i n a previous study (2) . Indeed as soon as the maximum amount of z e o l i t e i s formed the system i s d e p l e t e d i n A l and merely behaves as usual Na-Si hydrogels. Influence of the n a t u r e of a l k a l i c a t i o n s on t h e o p t i m a l s y n t h e s i s p r o c e d u r e f o r ZSM-48. The d i f f e r e n t a l k a l i c a t i o n s a f f e c t n u c l e a t i o n and growth of z e o l i t e s i n various ways, independently or i n competition with the other organic c a t i o n i c s p e c i e s . In p a r t i c u l a r , s m a l l e r hydrated s t r u c t u r e - f o r m i n g c a t i o n s (towards water) l i k e L i + or Na + r e a d i l y favour, along t h e o r g a n i c t e m p l a t e s , the f o r m a t i o n o f r e g u l a r s t r u c t u r e d a l u m i n o s i l i c a t e p r e c u r s o r s or SBU, and e s s e n t i a l l y i n f l u e n c e the n u c l e a t i o n process. S t r u c t u r e -b r e a k i n g c a t i o n s l i k e K + induce l e s s r e a d i l y s t a b l e p r i m i t i v e b u i l d i n g u n i t s , but can act as s t a b i l i z i n g m i n e r a l i z e r s during growth (11,19). We have checked such a behaviour by r e p l a c i n g Na + i o n s by L i + and K +, i n the g e l s g i v i n g ZSM-48 i n "optimum y i e l d " , namely M 20 2.5 HMBr2 A l 2 0 3 6 0 s i 0 2 3 0 0 0 H 2 Downloaded by UCSF LIB CKM RSCS MGMT on November 19, 2014 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch040In Zeolite Synthesis; Occelli, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. 594 ZEOLITE SYNTHESIS Figure 4. Percentage of c r y s t a l l i n i t y f o r z e o l i t e s ZSM-48 and EU-1 as a fu n c t i o n of Na 20 content i n the g e l . Curve a: ZSM-48 synthesized from: xNa 20 5HMBr2 0.5Al 2O 3 60SiO 2 3000H2O; curve b: EU-1 synthesized from: xNa 20 10HMBr2 1.5A1 20 3 60SiO 2 3000H2O; curve c: -quartz and/or c r i s t o b a l i t e c o - c r y s t a l l i z e d with ZSM-48; curve d: -quartz c o - c r y s t a l l i z e d with EU-1. Downloaded by UCSF LIB CKM RSCS MGMT on November 19, 2014 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch040In Zeolite Synthesis; Occelli, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. 40. GIORDANO ET AL. Competitive Role of Organic and Inorganic Cations 595 with two d i f f e r e n t A l contents (x= 0 or 0.5). The so ob t a i n e d c r y s t a l l i z a t i o n k i n e t i c curves o f ZSM-48 i n absence ("Figure 5a") and i n presence ("Figure 5b") of A l were compared f o r each c a t i o n i c system. In a l l three cases, the c r y s t a l l i z a t i o n was found f a s t e r i n absence of A l , i n agreement with what was g e n e r a l l y observed f o r (M) ZSM-5 ( 2 . ) . In a d d i t i o n , the i n d u c t i o n p e r i o d v a r i e s i n the f o l l o w i n g order: L i < Na < K, s u g g e s t i n g t h a t the s t r u c t u r e - f o r m i n g L i + and Na + b e t t e r favour the ZSM-48 n u c l e a t i o n process than K +. The f u r t h e r growth r a t e s f o r the t h r e e systems appear comparable ("Figure 5a"). Table I. Cation and A l contents of four ZSM-48 samples s y n t h e s i z e d from 5 M 20 2.5 HMBr 2 (0 or 0.5)Al 2O 3 60 S i 0 2 3000 H 20 a f t e r 48 h Sample M +/u.c. HM + +/u.c. Al/u.c . a b a Na-ZSM-48 0.05 1.0 (Na+Al)ZSM-48 0.20 1.0 0.59 K-ZSM-48 0.22 1.1 (K+Al)ZSM-48 0.23 1.1 0.62 a: atomic absorption; b: TG-DTA The amounts of i n c o r p o r a t e d a l k a l i c a t i o n s remain low (Table I) and these c a t i o n s o n l y n e u t r a l i z e the defe c t SiO~ negative charges f o r A l - f r e e samples. Note tha t the HM + + content f o r each sample i s s i m i l a r , t h i s s t r o n g l y suggesting that the e s s e n t i a l s t a b i l i z a t i o n of the framework i s achieved by the pore f i l l i n g a c t i o n , as i n the s i m i l a r system y i e l d i n g Nu-10 (14.) . However, t h i s f i l l i n g i s not completely a c h i e v e d by the o r g a n i c s (about 85%), because, f o r s t r u c t u r a l reasons, about one HM + +/u.c. i s the maximum p o s s i b l e amount t h a t can be incorporated i n the ZSM-48 framework (see below). S i m i l a r k i n e t i c s trends are observed i n presence of aluminium ("Figure 5b") with the d i f f e r e n c e t h a t Na + i s a l s o i n c o r p o r e t e d during growth, i n s i m i l a r amount than K +, both probably a c t i n g t o a l i m i t e d extent, as A10 2~ counterions. Downloaded by UCSF LIB CKM RSCS MGMT on November 19, 2014 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch040In Zeolite Synthesis; Occelli, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. 596 ZEOLITE SYNTHESIS Time (h) Figure 5 . C r y s t a l l i z a t i o n k i n e t i c s of z e o l i t e ZSM-48 i n presence of L i + , Na + and K + ions, without A l (a) and i n presence of 0.5 mole A I 2 O 3 i n the g e l (b) : 5Na 20 2.5HMBr2 (0 or 0.5)Al2C>3 60SiO 2 3000H2O. Downloaded by UCSF LIB CKM RSCS MGMT on November 19, 2014 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch040In Zeolite Synthesis; Occelli, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. 40. GIORDANO ET AL. Competitive Role of Organic and Inorganic Cations 597 C o m p e t i t i v e r o l e o f Na+ and HM++ s p e c i e s Unit c e l l composition of t y p i c a l z e o l i t e s prepared from d i f f e r e n t Na + b e a r i n g hydrogels are r e p o r t e d i n Table I I . The constant Na/Al r a t i o s measured f o r two ZSM-48 samples c r y s t a l l i z e d from two d i f f e r e n t g e l compositions at d i f f e r e n t s y nthesis times and from which the r e s i d u a l amorphous phase was removed by u l t r a s o n i c c l e a n i n g , confirms t h a t Na + ions are c o n t i n u o u s l y i n c o r p o r a t e d d u r i n g growth. In n e i t h e r case they can n e u t r a l i z e t o t a l l y the A l bearing negative charges, suggesting that the HM + + ions a l s o p a r t i c i p a t e i n t h i s n e u t r a l i z a t i o n p r o c e s s . N e v e r t h e l e s s , the amount of o r g a n i c ions was found t o be remarkably constant, as i n the case of the other a l k a l i systems (Table I ) . S i m i l a r y , i n sample 4, about one HM + + was again found occluded per u n i t c e l l of ZSM-48. However sample 4 contains a s l i g h t l y l a r g e r amount of N a + / u . c , and t h i s may be due to the l a r g e r Na 20 content c h a r a c t e r i z i n g i t s hydrogel p r e c u r s o r (Table II) . T h i s suggests t h a t Na + i o n s probably do not p l a y t h e i r n e u t r a l i z i n g r o l e as counterions t o A l . At l e a s t our o b s e r v a t i o n confirms t h a t , i n our sy n t h e s i s c o n d i t i o n s , Na + do not b r i n g A l to the s t r u c t u r e . Mechanism o f HM++ a c t i o n A l l the ZSM-48 samples s y n t h e s i z e d from the above envisaged g e l systems, accomodate about one HM + + per u n i t c e l l , t h i s corresponding to about 85% of the t o t a l pore f i l l i n g . By c o n t r a s t , the A l c o n c e n t r a t i o n can be d i f f e r e n t from one sample t o a n o t h e r , as i t s i n c o r p o r a t i o n i s governed by the i n i t i a l A l content i n the g e l , p r o v i d e d i t i s not too important. However, c o n s i d e r i n g the framework charge balance, at l e a s t p a r t of the HM + + ions must a l s o act as A l c o u n t e r i o n s . We t h e r e f o r e propose the f o l l o w i n g model t o e x p l a i n the r o l e of HM + + ions i n d i r e c t i n g syntheses of z e o l i t e s with l i n e a r channel systems such as ZSM-48 and EU-1. During the f i r s t r e s t r u c t u r a t i o n of the s i l i c a t e or S i - r i c h a l u m i n o s i l i c a t e complexes p r i o r t o the z e o l i t i c n u c l e a t i o n , t h e HM + + e n t i t i e s p l a y a s t r u c t u r e s t a b i l i z i n g r o l e . By t h e i r p a r t i c u l a r l i n e a r shape, they favour the formation of channel systems. Simultaneously, they can a l s o n e u t r a l i z e one AIO2"" negative center of the a l u m i n o s i l i c a t e complex by i t s p o s i t i v e N + ( C H 3 ) 3 ends. Note th a t t h i s does not exclude the formation of a c e l l i n v o l v i n g o n l y one (or l e s s ) A l , t h a t then i n t e r a c t s o n l y with one p o s i t i v e l y charged end of the template. The other p o s i t i v e end w i l l be s o l i c i t a t e d o n l y i f enough A l i s a v a i l a b l e i n the g e l , up t o a maximum of 2 Al per one HM++f i.e. per unit c e l l . Downloaded by UCSF LIB CKM RSCS MGMT on November 19, 2014 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch040In Zeolite Synthesis; Occelli, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. Table II. Nature crystallinity and chemical composition of various zeolites synthesized in presence of Na+ and HM"1"1" ions Sample AI2O3/S1O2 Synthesis Solid phase Composition per unit cell a Pore filling (gel) time,(h) (%crystal.) Al Na H20 HM++ SiOR (%) b b c de 1 0 48 ZSM-48(97) . ,d. n. ,d. 1. ,80 0. 98 11. .1 82 2 0, .0083 66 ZSM-48(81) 0, .78 0, .24 2 .31 1, .01 10. .6 85 0, .0083 90 ZSM-48(75) 0, .72 0, .24 2 .25 1. .00 10. .1 84 3 0, .0083 48 ZSM-48(93) 0. .60 0, .20 2, .97 1, .04 -87 If 0, .0083 66 ZSM-4 8(97) 0. .67 0, .24 2, .96 1. .05 -88 4 0. .0083 48 ZSM-48(83) 0. .74 0, .49 3, .42 0. .96 10. .9 80 5 0. .0250 120 EU-1 (80) 2, .10 0, .44 7. .40 1, .30 3. ,5 g Correspondence between sample number and gel composition:5 Na20 5 Na20 5 Na20 10 Na20 5 HMBr2 5 HMBr2 2.5 HMBr2 5 HMBr2 0.5 Al203 0.5 A1203 0.5 A1203 60 Si0 260 Si0 260 Si0 260 Si0 23000 H20 3000 H20 3000 H20 3000 H20 10 Na20 10 HMBr 2 1.5 A12C>3 60 Si02 3000 H20 a For sake of comparison, one unit cell of EU-1 is assumed to have 48 atoms b Evaluated by PIGE c Evaluated by TG-DTA d Evaluated by TG-DTA and ammonia titration e Evaluated by 29Si-NMR f Percentage of filling as calculated by considering the length of one HM++ in equal to 14.05 , and by considering the total channel length of one ZSM-48 unit cell equal to 16.8 . g The total length of the tortuous channel system of EU-1 is not known. The Na and Al contents for sample 3 at (4 8 h) were evaluated by atomic absorption ES Downloaded by UCSF LIB CKM RSCS MGMT on November 19, 2014 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch040In Zeolite Synthesis; Occelli, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. 40. GIORDANO ET AL. Competitive Role of Organic and Inorganic Cations 599 The f i n a l s t r u c t u r e so genereted i s a Cmcm-Imma inte r g r o w t h (&) i n which the Cmcm u n i t i s only able to accomodate two A l at st a b l e p o s i t i o n s . For l a r g e r A l g e l concentrations r i n g s i n v o l v i n g an even number of atoms (e.g. four membered ring s ) w i l l be p r e f e r e n t i a l l y f a v o u r e d and the f i n a l s t r u c t u r e s t a b i l i z e d by the HM + + ions w i l l be d i f f e r e n t i n terms of geometry and c o n c e n t r a t i o n of s t a b l e s i t e s f o r aluminium (1) . EU-1 i s one example of such a s t r u c t u r e , s t a b i l i z e d by HM + + ions under the p a r t i c u l a r c o n d i t i o n s d e s c r i b e d . For i n t e r m e d i a t e A l c o n c e n t r a t i o n s i n the g e l phases, one can suppose t h a t both s t r u c t u r e s coc r y s t a l l i z e , each i n c o r p o r a t i n g the appropiate amount of A l . As a c o n c l u s i o n , HM + + i o n s are not e x c l u s i v e templates f o r a given s t r u c t u r e but w i l l s t a b i l i z e an a l u m i n o s i l i c a t e s t r u c t u r e that i s p r e l i m i n a r i l y favoured by other v a r i a b l e s such as the A l content i n the g e l . They w i l l a c t p a r t l y as co u n t e r i o n s t o the neg a t i v e framework, p a r t l y as pore f i l l e r s . O b v i o u s l y , they e x c l u s i v e l y act as pore f i l l e r s i n the A l fr e e g e l s , i n which a l k a l i c a t i o n s can be pre s e n t ( t h i s work) or absent (2) . In ZSM-48 the presence of HM + + generates a marked number of s t r u c t u r a l S i R d e f e c t groups (up t o 11 SiOR/ u.c.) (R = H, M + or HM+ + ), as measured by 2 9Si-NMR (Table I I ) . In c o n t r a s t , when a l i n e a r diaminoalkane i s used as template a s m a l l e r amount of de f e c t groups i s measured (about 3.5 SiOR/u.c.) (21) . The d i f f e r e n c e between t h e s e two v a l u e s , about 8 SiO R / u . c , can be e a s i l y e x p l a i n e d by c o n s i d e r i n g the a c t u a l s i z e of the bul k y t e r m i n a l trimethylammonium groups. Being l a r g e r (6.9 ) than the average ZSM-48 channel diameter (about 5.3*5.6 ) , they are accomodated w i t h i n the s t r u c t u r e by c r e a t i n g 4 SiOR groups at each end of the channel that r e s u l t from an empty p o s i t i o n ("Figure 6") . Such d e f e c t groups l i n k e d t o empty p o s i t i o n s have a l s o been det e c t e d i n high s i l i c a ZSM-5 (15.) .By c o n t r a s t few s t r u c t u r a l d e f e c t s are detected i n the EU-1 framework. T h i s i s e a s i l y e x p l a i n e d by c o n s i d e r i n g t h a t the si d e pockets r e s u l t i n g from the h i g h t o r t u o s i t y o f the s t r u c t u r e more e a s i l y accomodate the t e r m i n a l trimethylammonium groups of the HM + + i o n . Conclusion The framework of z e o l i t e ZSM-48 can be o r i e n t e d by hexamethonium (HM + +) templates i n v a r i o u s g e l systems h a v i n g d e f i n e d A l c o n c e n t r a t i o n s . The HM + + i o n s Downloaded by UCSF LIB CKM RSCS MGMT on November 19, 2014 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch040In Zeolite Synthesis; Occelli, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. 600 ZEOLITE SYNTHESIS Figure 6.Schematic l o c a l i z a t i o n of hexamethonium ions i n ZSM-48 channel s t r u c t u r e , generating SiO" defects near the terminal trimethylammonium groups of the template. Downloaded by UCSF LIB CKM RSCS MGMT on November 19, 2014 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch040In Zeolite Synthesis; Occelli, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. 40. GIORDANO ET AL. Competitive Role ofOrganic and Inorganic Cations 601 s t a b i l i z e the z e o l i t i c s t r u c t u r e i n formation and, by t h e i r p a r t i c u l a r l i n e a r shape, t h e y f a v o u r t h e generation of the channel system. In a d d i t i o n , they a l s o n e u t r a l i z e the negative charges of the s t r u c t u r e , l i n k e d e i t h e r t o S i - 0 - A l ~ e n t i t i e s or t o S i - 0 ~ d e f e c t groups. Because the complete f i l l i n g by the HM + + ions represents one HM + + per u n i t c e l l , the maximum number of A l atoms th a t can be introduced i n t o the framework, i s t h e r e f o r e e q u a l t o two. I n t e r e s t i n g l y because o f s t e r i c i n t e r a c t i o n s , the HM + + ions introduce defect groups i n t o the s t r u c t u r e , t he amount of which can be e a s i l y r a t i o n a l i z e d by supposing the presence of two missing s i t e s per u n i t c e l l . Note that i f ZSM-48 i s formed i n presence o f polymethylenediamines, much l e s s d e f e c t groups are intro d u c e d i n the s t r u c t u r e . A l k a l i c a t i o n s p l a y a secondary r o l e and probably n e u t r a l i z e the Si-0"~ defect groups. A higher A l content i n the hydrogel i s a predominant v a r i a b l e t h a t leads t o a d i f f e r e n t l y arranged A l - r i c h e r EU-1 framework. HM + + s t a b i l i z e t h i s framework as counterio n s along with the a l k a l i c a t i o n s and a l s o as pore f i l l i n g agents, but do not i n i t i a t e i t s n u c l e a t i o n . The more open, t o r t u o u s pore s t r u c t u r e t h a t r e s u l t s , accomodates the HM + + ions e a s i l y , without much s t e r i c c o n s t r a i n t , and the EU-1 s t r u c t u r e c o n t a i n s a f a r smaller number of S i - 0 ~ defects than ZSM-48. Literature cited 1. Casci, J.L.; Whittam, T.V.; Lowe, B.M. Proc. 6th Intern, Zeolite Conference, 1984, p 894. 2. Dodwell, G.W.; Denkewicz, R.P.; Sand, L.B. Zeolites 1985, 5, 153. 3. Dewaele, N.; Gabelica, .; Bodart, P.; B.Nagy, J.; Giordano, G.; Derouane E.G. Stud. Surf. Sci. Catal. 1988, 37, 65. 4. Casci, J.L. Stud. Surf. Sci. Catal. 1986, 28, 215. 5. Araya, .; Lowe, B.M. J. Catal. 1984, 85, 135. 6. Chu, P. Eur. Patent 23 089, 1981 and U.S. Patent 4 397 827, 1983. 7. Kaeding, W.W. Eur. Patent 219 271, 1987. 8. Schlenker, J.L.; Rohrbaugh, W.J.; Chu, P.; Valyocsik, E.W.; Kokotailo, G.T. Zeolites 1985, 5, 355. 9. Briscoe, N.A.; Johnson, D.W.; Shannon, M.D.; Kokotailo, G.T.; McCusker, L.B. Zeolites 1988, 8, 74. 10. Gabelica, .; Blom, N.; Derouane, E.G. Appl. Catal. 1983, 5, 227 and references cited therein. 11. Gabelica, Z.; Derouane, E.G.; Blom, N. In Catalytic Materials: Relationship between Structure and Reactivity: White,.., Jr. et al., Eds.; ACS Symposium Downloaded by UCSF LIB CKM RSCS MGMT on November 19, 2014 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch040In Zeolite Synthesis; Occelli, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. 602 ZEOLITE SYNTHESIS Series No. 248; American Chemical Society: Washington, DC, 1984; p 219. 12. Nastro, .; Gabelica, Z. ; Bodart, P.; B.Nagy, J . Stud. Surf. Sci. Catal. 1984, 19, 131. 13. Lok, B.M.; Cannan, T.R., Messina, C.A. Zeolites 1983,3, 252. 14. Pellegrino, C.; Aiello, R.; Gabelica, Z. In ACS Symposium Series "Advances in Zeolite Synthesis" (this book) and references cited therein. 15. B.Nagy, J.; Bodart, P.; Colette, H.; El Hage-Al Asswad, J.; Gabelica, Z. ; Aiello, R.; Nastro, .; Pellegrino, C. Zeolites 1988,8, 209. 16. Debras, G.; Derouane, E .G. ; Gilson, J .P . ; Gabelica, Z. ; Demortier, G. Zeolites 1983,3, 37. 17. Nastro, .; Colella, C.; Aiello, R. Stud. Surf. Sci. Catal. 1985, 24, 39. 18. Bellussi, G.; Perego, G.; Carati, .; Cornaro, U.; Fattore, V. Stud. Surf. Sci. Catal. 1988, 37, 37. 19. Guth, J.L.; Caullet, P. J . Chim. Phys. 1986, 83, 155. 20. Rollman, L.D. In Zeolites, Science and Technology; Ribeiro, F.R. et al., Eds.; M. Nijhoff, Den Haag, 1984, p 109. 21. Dewaele, N. Ph.D. Thesis, Namur University, Namur, 1988. 22. Van Santen, R.A.; Keijsper, J.; Ooms, J.; Kortbeek, A.G.T.G. Stud. Surf. Sci. Catal. 1986, 28, 169. RECEIVED February 18, 1989 Downloaded by UCSF LIB CKM RSCS MGMT on November 19, 2014 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch040In Zeolite Synthesis; Occelli, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989. Chapter 40 Competitive Role of Organic and Inorganic Cations in Directing One-Dimensional Zeolitic StructuresExperimentalResults and DiscussionInfluence of the initial Al contentInfluence of HMBr2Influence of NaOH concentration.Influence of the nature of alkali cations on the optimal synthesis procedure for ZSM-48.Competitive role of Na+ and HM++ speciesMechanism of HM++ actionConclusionLiterature cited

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