Synthesis of Pentasil Zeolites With and Without Organic Templates

Chapter 20

Synthesis of Pentasil Zeolites With and Without Organic Templates 1

1

2

2

2

W. Schwieger , K.-H. Bergk , D. Freude , M. Hunger , and H. Pfeifer Downloaded by CORNELL UNIV on May 13, 2012 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch020

1

Sektion Chemie der Martin-Luther-Universität Halle-Wittenberg, Schlossberg 2, DDR-4020 Halle, German Democratic Republic Sektion Physik der Karl-Marx-Universität Leipzig, Linnestrasse 5, DDR-7010 Leipzig, German Democratic Republic

2

Magic-angle-spinning nuclear magnetic resonance spec troscopy (MAS NR) yields quantitative information about Brönsted acidity and structural defects in zeo lites. We have studied samples of pentasil zeolites synthesized with and without organic templates using 1H and 27Al NMR. The influence of mono-, di- and tri-nalkylamine and tetraalkylammonium compounds (alkyl = methyl, ethyl, propyl and butyl) upon the rate of crystallization, yield and the properties of the pro ducts is discussed. By varying the SiO /AlO ratio and the lengths of the period of crystallization at 175 °C, H O/SiO =30, Na O/SiO =0.1 we have arrived optimal reaction conditions for a template-free synthesis of zeolites of ZSM-5 type at SiO /Al O =30-50 and 36-48 h. In all samples the concentration of non-acidic hydroxyl groups (silanol groups) is much higher than could be accounted for by the number of terminal hydroxyls on the external surface of the crystallites. In the H-form of the zeolites the number of acidic OH groups is equal to the number of framework aluminium atoms. We demon strate that it is possible to synthesize defect-free zeolites of type ZSM-5 without an organic template. 2

2

2

2

3

2

2

2

3

The synthesis of p e n t a s i l zeolites i s supported by organic cations. Argauer et a l . (_1) f i r s t described syntheses with tetraalkylammonium and tetraalkylphosphonium compounds. The organic cations may not only i n i t i a t e and sustain a certain c r y s t a l l i z a t i o n process but also may lead to products of a new structure. This "templating" behaviour i s explained by the structure-directing e f f e c t of the organic cations i n the process of c r y s t a l l i z a t i o n (2,3;. 0097-^156/89A)398-O274$06.00/0 © 1989 American Chemical Society In Zeolite Synthesis; Occelli, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989.

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Synthesis of Pentasil Zeolites

Downloaded by CORNELL UNIV on May 13, 2012 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0398.ch020

In the past numerous syntheses were described using compounds which were assumed to possess this templating property. A few references are given i n Table I, beginning with the c l a s s i c templates, going to more simple molecules and ending with the template-free synthesis. A group-specific arrangement i s presented i n Table I I . Table I.

Organic compounds, which were mostly used i n syçtheses of zeolites of pentasil-type. Abbreviations are TPA f o r tetrapropylammonium cation, TEPA f o r triethylmonopropylam^ monium cation, TBA for tetrabutylammonium cation, TBP for tetrabutylphosphonium cation, TPA f o r tripropylamine and C-DN f o r hexamethyldiamine

Product

Group of compounds

ZSM-5

tetraalkylammonium

Preferred comp.

References (1,4.5) (6,7)

trialkylamine and alkylhalogenide

TPA TEPA TPA and propylchloride

ZSM-11

tetraalkylammonium or tetraalkylphosphonium cation

™ t + TBA , TBP

(12) (5)

ZSM-5 like

alkanolamine diamine mono-n-alky lamine alcohols and ammonia alcohols template-free

NHgCHÔH

(13-15) (16) (17-19) (20) (21) (22,23)

Table

cation

+

propylamine C,H 0H Q

CJHÔH

(8-11)

I I . The d i f f e r e n t types of organic compounds, which can be used for the syntheses of p e n t a s i l z e o l i t e s

Type

References

Examples +

+

organic cations

R N , R P polymeric c a t i o n i c compound

(1,4,5,7) (24)

organic molecules

diamine amine alcohols dioxane 2-aminopyridine

(16) (17-19) (20.21) (25) (26)

organic anions

alkylbenzolsulfonate polymeric anionic compound

(27) (28,29)

4

4

In consideration of the fact that even a template-free synthesis i s possible i t i s not easy to understand that a l l d i f f e r e n t groups of compounds should have the same structure-directing e f f e c t . For a more p l a u s i b l e explanation we must consider the reaction mixture as a whole and discuss the combined effects of a l l components. Table I I I i s an attempt to systematize the effects of d i f f e r e n t components.

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

276

ZEOLITE SYNTHESIS

Table I I I . The influence of the r e l a t i v e (referred to SiO^) amount of d i f f e r e n t compounds of the reaction mixture upon the properties of the reaction mixture and of the product Molar r a t i o A

Properties

S

^2°3^ ^°2 HLO/SiCL 0H~/Si0

composition of the network v i s c o s i t y , concentration of hydroxyde ions molecular weight of s i l i c a t e s , cone, of hydroxide ions

2

N

+

c a t


R N /SiO^ )

i o n d i s t r i b u t i o n , templating e f f e c t , Al-content

To draw conclusions concerning the templating e f f e c t of d i f f e r e n t molecules, comparable conditions f o r the c r y s t a l l i z a t i o n process must be used. In this paper we present a systematic investigation on the e f f e c t o f mono-, d i - and tri-n-alkylamine and tetraalkylammonium compounds ( a l k y l = C. - C,) upon the rate of c r y s t a l l i z a t i o n , y i e l d and the properties of the products. Also the f i e l d of a templatefree synthesis i s studied. The products were characterized by magicangle-spinning nuclear magnetic resonance spectroscopy (MAS NMR) and X-ray d i f f r a c t i o n . Experimental The template containing samples were synthesized using a procedure based on those given by Union Carbide (30). The batch composition expressed i n mole r a t i o s was as follows: 1 R 0 * 4.1 Na 0 * 50 S i 0 2

2

2

* 0.417 A l 0 2

with R = CJSI, ( C ) N , ( Q ^ N , ( C ^ N * and C i

±

2

3

* 691 H 0 2

= C^-C^ = methyl-butyl.

Some of the samples were synthesized without Al 0«. The syntheses with tetrapropylammonium iodide (TPA J") as template were c a r r i e d out with a varying S i 0 / A l 0 o r a t i o i n the range 25 - 400. The batch composition of the template-free synthesis was 2

2

2

4 Na 0 * 1 A 1 0 2

2

3

* x Si0

2

* 1200 H 0 2

where χ varies from 10 to 100. Sodium s i l i c a t e , sodium aluminate and NaOH were obtained from VEB Chemiekombinat B i t t e r f e l d . The organic templates were guaranteed reagents. At f i r s t NaOH was d i l u t e d i n water and then sodium s i l i c a t e and sodium aluminate i n l i q u i d or d i l u t e d form were added under s t i r r i n g . Afterwards, the organic compound was added under vigorous s t i r r i n g . The obtained mixture was s t i r r e d f o r further 15 min^ and then d i s t r i b u t e d over several autoclaves i n portions of 50 cm çer autoclave. The c r y s t a l l i z a t i o n was conducted i n a furnace at 175 C. The reaction vessels were placed on rotating shafts. A f t e r the time of c r y s t a l l i z a t i o n the autoclave was quickly cooled down. The products were f i l t e r e d , washed and dried a t 100 °C. The procedure of the template-free synthesis was d i f f e r e n t i n only one point: To the d i l u t e d aqueous solution of sodium s i l i c a t e the sodium aluminate was added.



20.

SCHWIEGERETAL

277


The synthesized samples were analyzed by X-ray powder d i f f r a c t i o n f o r q u a l i t a t i v e and quantitative phase i d e n t i f i c a t i o n . The unit used was a P h i l i p s Model with a v e r t i c a l goniometer and a s c i n t i l l a t i o n coun ter, u t i l i z i n g N i - f i l t e r e d CuK^ r a d i a t i o n . For quantitative phase i d e n t i f i c a t i o n an external standard sample of oe-AÔ^ was used. The percentage c r y s t a l l i z a t i o n was calculated using the averaged peak i n t e n s i t i e s a t 20=35.2° and 20=47.3° of the reference sample and the peak i n t e n s i t y at 20=23.2° f o r the sample under study (31). X-ray and aluminium MAS NMR measurements were c a r r i e d out on samples rehydrated i n a desiccator over an aqueous NH,C1 solution. A portion of the zeolites synthesized with organic tempât^s was heated for 5 h at 600 °C to remove organic compounds. The Na /H ion exchan ge was c a r r i e d out at room temperature with an aqueous solution of 0.5 N HC1. The preparation of Η MAS NMR samples was performed under shallow bed a c t i v a t i o n conditions i n a glass tube of 5.5 mm inner diameter and 10 mm height of the z e o l i t e layer. The temperature was increased at a rate of 10 K/hr. A f t e r maintaining the samples at^the f i n a l a c t i v a t i o n temperature of 400 °C under a pressure below 10 Pa for 24 hrs., they were cooled and sealed. NMR measurements were performed on a home-made spectrometer HFS 270 and on a BRUKER spectrometer MSL 300. As a reference f o r i n t e n s i t y measurements of the aluminium NMR a well-characterized sample of ZSM-5 with a framework S i / A l - r a t i o of 15 was used. The t o t a l concentration of OH groups i n the activated samples was deter mined by comparison of the maximum amplitude of the free induction of the samples with those of a c a p i l l a r y containing an aqueous solution i n a probe with a short ring-down time... To separate the r e l a t i v e i n t e n s i t i e s of d i f f e r e n t l i n e s i n an Η MAS NMR spectrum quantita t i v e l y , the signals of the spinning side bands were added to the main s i g n a l . The home-made MAS equipment f o r the rotation of the fused glass ampoules was c a r e f u l l y cleaned to avoid spurious proton signals. Results and Discussion Synthesis. Figure 1 shows the c r y s t a l l i z a t i o n of template-containing z e o l i t e s a s a function of time. The aluminium-free syntheses using TEA , TPA and TBA as template give products wjj-th p e n t a s i l structure ( s i l i c a l i t e I or II) without other phases. ΊΜΑ and a l l other amines mentioned above y i e l d i n the aluminium-free syntheses as the f i r s t c r y s t a l l i n e phase only magadiite, an aluminium-free sheet s i l i c a t e . The aluminium containing syntheses give d i f f e r e n t phases with penta s i l structure, sheet structure and an amorphous phase. Table IV pre sents the maximum percentage ccystaj.lizatj.on of the p e n t a s i l phase. The value of about 100% f o r TEA ,ΤΡΑ , TBA , di-and tri-n-propylamine and d i - and tri-n-butylamine proves that these syntheses y i e l d only t h e p e n t a s i l phase. X-ray d i f f r a c t i o n analysis shows that TPA and TBA lead to the ZSM-5 and ZSM-11 structure type, respectively. Figure 2 shows a comparison of the X-ray d i f f r a c t i o n patterns. The most intense d i f f r a c t i o n l i n e s occur at 20 =20°-27°. Going from the tetraalkylammonium to the alkylamine compounds a s p l i t t i n g of the 23.2° l i n e can be observed. The form of the s p l i t ted l i n e seems to be t y p i c a l f o r the template. Similar patterns have been measured f o r the following z e o l i t e s of p e n t a s i l type (32): NU-5 (EP 54 386), ZSM-8 (NL 7 014 807) and ZETA-1 (DE 2 548 695). I t i s not c l e a r whether the +

+

+



278

ZEOLITE SYNTHESIS

Yield/%

10

1β

Η

22

26

30

t/h

2k

t/1j

Figure 1. Y i e l d of p e n t a s i l zeolites (percentage c r y s t a l l i z a tion) as a function of time. Abbreviations are f o r mono-nbutylam5ne, f o r mono-n-propylamine, C f o r mono-n-ethylamine, CL f o r mono-n-me thy lamine, di-C, f o r di-n-propy lamine, di-C« f o r di-n-propylamine, di-C2 f o r di-n-ethylamine, di-n-C. f o r a i - n methylamine, TPA A l - f r e e f o r the aluminium-free synthesis with the tetrapropylammonium cation, TPA f o r tetrapropylammonium cation, TEA A l - f r e e f o r the aluminium-free synthesis with the tetraethylammonium cation, TEA f o r tetraethylammonium cation and tri-Co f o r tri-n-propylamine. 2

+

+




20. SCHWIEGER ET AL·


279

280

ZEOLITE SYNTHESIS


Table IV.

The y i e l d s of syntheses measured i n mass% of c r y s t a l l i n e p e n t a s i l i n dependence on the template. The experimental error i s about +10%

Template

methyl

ethyl

propyl

butyl

mono-n-alkylamine di-n-alkylamine tri-n-alkylamine tetraalkylammonium cation

21 20 11 23

40 55 77 90

50 100 106 100

70 100 101 103

patterns are due to a special phase or due to an intergrowth ZSM-5/ZSM-11, c f . (33,34). Magadiite apart from p e n t a s i l phases can be found i n z e o l i t e s synthesized with mono-n-methyl-, -ethyl-, -propyl- or -butylamine, with di-n-methyl-, -ethyl- or -propylamine, with tri-n-methyl- or -ethy lamine and with te trame thy lammonium iodide. Table IV shows that the z e o l i t e content increases with the number of carbon atoms per group and with the number of a l k y l groups. Values describing the k i n e t i c s of c r y s t a l l i z a t i o n with organic compounds are presented i n Table V. Figure 3 shows how the values t = induction period, t = period of growth and k = percentage cryst a l l i z a t i o n per hour can^be determined from the curves presented i n Figure 1. Aluminium decelerates the synthesis as can be shown by comparison o f t h e aluminium-containing and the aluminium-free sytheses using TPA and TEA as template. Compounds containing the propyl group give the best structure d i r e c t i n g e f f e c t and among them the shortest induction period has beeen found f o r TPA and the maximum c r y s t a l l i z a t i o n rate for tri-n-propylamine. +

+

Table V. The induction period t , the period of growth t , the c r y s t a l l i z a t i o n rate k °(percentage c r y s t a l l i z a t i o n ^ per hour) and the maximum percentage c r y s t a l l i z a t i o n (mpc) i n dependence on the d i f f e r e n t templates used i n p e n t a s i l syntheses Template mono-n-methylamine mono-n-ethylamine mono-n-propylamine mono-n-butylamine di-n-me thy lamine di-n-ethy lamine di-n-propy lamine di-n-buty lamine tri-n-propy lamine TEAT TPAT TEA]; (Al-free) TPA (Al-free)

t

0

(h) x

20.8 18.8 12.7 11.8 21.0 18.8 16.0 18.5 13.2 6.0 4.3 5.2 3.0

'

t (h> R

3.5 4.2 3.6 3.2 4.1 2.9 2.2 2.0 0.9 4.0 1.0 4.2 0.5

1

k (% h' ) 6 10 14 22 5 19 46 50 118 24 100 25 216

mpc (%) 21 40 50 70 20 55 100 100 106 98 100 104 108


20.

SCHWIEGER ET AL·

281


Figure 4 presents the isothermal phase transformation diagram of the template-free syntheses i n which the Si0 /Al 0« r a t i o and the time t of c r y t a l l i z a t i o n are varied. The S i C L / ^ O and tÔ/SiO^ r a t i o s are 10 and 30, respectively. The p e n t a s i l phase could only be synthe sized for η = S i 0 / A l 0 = 3 0 - 5 0 and t = 36 - 72 h. Outside of this area amorphous material, mordenite, sheet structures s i m i l a r to kenyaite, quartz and c r y s t o b a l i t e can be found. For values of η less than 25 the c r y t a l l i n e product i s mordenite. For 30 < η < 50 a y i e l d of 95% (related to the S i 0 content) ZSM-5 type, which was proved by X-ray d i f f r a c t i o n pattern, could be found. Depending on η and the c r y s t a l l i z a t i o n time, t, a more or less large amount of amorphous material i s produced. This i s shown i n Figure 5. A long c r y s t a l l i z a t i o n time causes r e c r y s t a l l i z a t i o n and i s harmful to the y i e l d of ZSM-5 products. The influence of the compounds i n the c r y s t a l l i z a t i o n mixture upon the morphology of c r y s t a l l i t e s i s i l l u s t r a t e d by the scanning electron micrographs presented i n F i g u r e s 6-8. Figure 6 shows that i n the aluminium-free syntheses TPA gives spherical c r y s t a l l i t e s with a diameter of 2-3 μπι and TEA gives rhombic c r y s t a l l i t e s with sizes of about 1x2x5 μπι. Figure 7 demonstrates the influence of the Si0 /Al 0o r a t i o on the morphology. With increasing r a t i o the s i z e and the smoothness of the c r y s t a l l i t e s increase. The template-free synthesized z e o l i t e s with a SiOVAlÔ- r a t i o of 30 show f l a k i n g surfaces (see Figure 8). In conclusion the syntheses performed i n t h i s work showj. - The r e a l structure d i r e c t i n g e f f e c t i s caused by the TEA , TPA , and TBA cations. These cations cause the structure d i r e c t i n g e f f e c t also i n the aluminium-free syntheses. - Amines support the synthesis of aluminium containing pentasils i n dependence on their number of carbon atoms. - A template-free synthesis can be performed i n a limited range of the S i 0 / A l 0 r a t i o . Based on these r e s u l t s a z e o l i t e of p e n t a s i l type i s i n d u s t r i a l l y produced by Chemiekombinat B i t t e r f e l d , GDR. 2

2

2

2

3


2

+

+

2

2

+

+

2

2

3

NMR-characterization. 7 Corbin et a l . (35) were able to show by a systematic study that A l MAS NMR gives the true S i / A l r a t i o with a mean error of 10 %, i f two conditions are met: a) The amount of paramagnetic species i s less than 0.05 % and b) the sample does not contain NMR-invisible" aluminium. Chemical analyses of the samples under study showed that condition one i s f u l f i l l e d . I f samples con tain "NMR-invisible" aluminium a difference between the concentration determined by chemical analysis and the framework aluminium concen t r a t i o n determined by NMR should be observed. From the absence of such a difference we conclude that "NMR-invisible" aluminium species do not e x i s t i n our samples. Also a l i n e at the p o s i t i o n of about 0 ppm due to octahedrally coordinated non-framework aluminium and a broad l i n e at about 30 ppm due to tetrahedrally coordinated nonframework aluminium (36) could not be observed. The values f o r the concentration of framework aluminium atoms derived from the i n t e n s i t i e s of the l i n e at about 60 ppm (see below) are i n good agreement with those corresponding to the amount of alumina d i n the syn thesis mixtures. In conclusion, through the A l MAS NMR measu rements i t was possible to show that a l l aluminium atoms are incorpo rated i n tetrahedrally oxygen coordinated framework p o s i t i o n s . 2

M

u s e



282

ZEOLITE SYNTHESIS

Figure 3. C r y s t a l l i z a t i o n as a function of time, t denotes the induction period, t the period of growth and the°rate of cryst a l l i z a t i o n , k, can^be calculated using the maximum percentage c r y s t a l l i z a t i o n , Y > by k = Y It max g m a x

100

80 •SS . ^ Z SSMqnd M o f i d SS

ZSMand SS

60 -

/ r / ZSM and quartz

amorph. and ISM

40

ZSM " rs*MQnd~mordên ι?Γ

20-

quartz

1

^

/

mordenite 96

120

240

t/h

Figure 4. Isothermal phase transformation diagram of the template free syntheses. SS denotes sheet structures.



20.

SCHWIEGERETAK

283


Yield

20

40

60

80

100 Si0i/AI 0 2

3

Figure 5. Y i e l d of pentasil z e o l i t e s as a function SiCL/AlÔo r a t i o for d i f f e r e n t c r y s t a l l i z a t i o n times.

on the


ZEOLITE SYNTHESIS


284

Figure 6. Scanning electron micrographs of tjjie products of the aluminium-free syntheses with TPA (A) and TEA (B) as template. (3000 x)


SCHWIEGERETAK


285


20.

Figure 7. Morphology of pentasil zeolites synthesized with TPA as template i n dependence on the S i 0 / A l 0 ~ r a t i o of 25 (A), 50 (B), 100 (C), 200 (D) and 400 (Ε). (5000x) 9

Z

9

Z

J


ZEOLITE SYNTHESIS


286

Figure 8. Scanning electron micrographs of the products of the template-free syntheses performed at 175 °C (A) and 200 °C (B). (8000x)



20.

SCHWIEGERETAL.

287


27 The l i n e width of the corresponding A l MAS NMR s i g n a l i s determined by second-order quadrupole interaction. That means, i t i s determined by the deviation from the i d e a l tetrahedral symmetry of the AIO^ u n i t s . The highest degree of symmetry r e s u l t i n g i n a l i n e width of 7+1 ppm (at 6.3 T) i s observed for the p e n t a s i l phase. The quartz phase, mordenite and the amorphous phase gave l i n e widths of 9 ppm, 14 ppm and 18 ppm, respectively. The s h i f t of the centre of gravity of the lines with respect to the resonance position of the aluminiumhexaaquo complex i s 47-56 ppm. Taking into account the quadrupole correction for the s h i f t , which has a maximum value equal to the l i n e width (37) a chemical s h i f t of ca. 60 ppm r e s u l t s f o r a l l l i n e s . 2η Therefore, through a measurement of the chemical s h i f t of the A l MAS NMR l i n e i t i s not possible to d i s t i n g u i s h between d i f f e r e n t phases i n the product. The amorphous and the c r y s t a l l i n e phases give a difJerence only i n the l i n e width. Η MAS NMR spectra are presented i n Figure 9. Two different signals can be seen i n the spectra of the hydrogen forms. Line (a) at 2 ppm i s due to non-acidic hydroxyl groups ( s i l a n o l groups) at the outer surface of z e o l i t e c r y s t a l l i t e s , at framework defects and i n the amorphous part of the sample. Line (b) at 4.3 ppm i s caused by bridging ( a c i d i c ) OH groups (38). Further l i n e s due to d i f f e r e n t types of a c i d i c OH groups or A10H groups on non-framework aluminium species (38), could not be observed i n these spectra. Values f o r the concentration of framework aluminium atoms and of the hydroxyl pro tons giving r i s e to l i n e s (a) and (b) are presented i n Tab. 6. The number of terminal OH groups ^Qper.gram of d r i e d z e o l i t e , ru,, i s calculated by Up = 0.12 χ 10 d" , where d denotes the diame ter of the c r y s t a l l i t e s (pm). The i n t e n s i t i e s of l i n e (a) i n Table VI show that f o r a l l speci mens the values for the concentration of SiOH groups are much greater than the values obtained from a calculation of the number of terminal OH groups. Jhe extremely high concentration of s i l a n o l groups obser ved f o r TPA /ZSM-5 zeolites i s i n accordance with our previous f i n dings (38,39). The number of these SiOH groups i s larger, by a factor of up to 1000, than the number which i s necessary to terminate the external c r y s t a l surface. From the absence of amorphous material (within the accuracy of the X-ray measurements) i t follows that up to 8% of the framework S i are present as SiOH groups. This means, that the ZSM-5 synthesis with TPA as template leads to a highly disturbed l a t t i c e with a high concentration of non-intact Si-O-Si bonds. The enhanced concentrations of SiOH groups i n the hydrogen form of the z e o l i t e s indicate that, a f t e r sample c a l c i n a t i o n , about h a l f the defect s i t e s are present as Si-O-Na, the other h a l f being present as i n t e r n a l s i l a n o l groups. The treatment with 0.5 N HC1 leads to the exchange of Na cations on the defect s i t e s with Η , thus forming a maximum number of s i l a n o l groups. This behaviour can be explained (36) by the following reaction scheme of a defect s i t e : +

Na I

? Si

m

TPA

Na

l

I

? Si

m

850 K, 10 h

H

I

H I

H I

? Si

? 0.5 N HCl, 15 h Si

? Si

? Si

m

m

m

/i\


ZEOLITE SYNTHESIS


288


20.

SCHWIEGERETAL

Table VI.

Concentrations of hydroxyl species and framework aluminium atoms i n the hydrogen (H) or sodium (Na) form of p e n t a s i l zeolites synthesized with d i f f e r e n t organic templates and without organic templates

Form/Template


289


Crystallite diameter (μπι) S i 0 / A l 0 ratio

H/none H/none H/mono-n-propy lamine H/mono-n-butylamine Na/TPA H/TPA Na/TPA H/TPA Na/TPA H/TPA

2

3.2 3.0 1.2 1.1 1.7 1.7 1.5 1.5 2.1 2.1

30 52 70 60 60 60 220 220 360 360

2

3

2Q Concentration (10 species per gram) Protons. Protons. Framework l i n e (a; l i n e (b) A l atoms 0.6 0.5 0.4 0.5 1.5 3.7 1.3 3.6 1.6 3.8

4.9 3.2 3.2 3.5 0.0 3.5 0.0 1.2 0.0 0.5

5.8 3.6 2.7 3.2 3.2 3.2 0.9 0.9 0.6 0.6

Since a hydrothermal treatment at 1100 Κ f o r 5 days leads to a hea l i n g of the z e o l i t i c framework, most of the i n t e r n a l SiOH groups must be v i c i n a l : Neighbouring framework defects ( v i c i n a l SiOH groups) are transferred v i a dehydration into intact Si-O-Si bonds (36). By contrast, ZSM-5 specimens from organic-free batches and those synthesized by η-butyl- and η-propylamine possess r e l a t i v e l y intact l a t t i c e s with only a small concentration of i n t e r n a l s i l a n o l groups (see Figure 9 and Table V I ) . Concerning the concentration of Bronsted s i t e s ( a c i d i c bridging OH groups) we found that f o r the hydrogen form of the z e o l i t e s the number of bridging hydroxyl groups i s i n good agreement with the number of framework aluminium atoms.

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14. Ball, W. J.; Palmer, V.W.;Stewart, P. G. Patent EP 2899, 1979. 15. Ball, W. J.; Palmer, V.W.;Stewart, P. G. U.S. Patent 4 346 021, 1982. 16. Rollmann, L. D. U.S. Patent 4 108 881, 1978. 17. Rubin, M. V.; Rosinski, E. J.; Plank, Ch. J. Patent DE 2 442 240, 1975. 18. Rubin, M. V.; Rosinski, E. J.; Plank, Ch. J. U.S. Patent 4 151 189, 1979. 19. Bremer, H.; Reschetilowski, W.; Son, D. Q.; Wendland, K.-P.; Nau, P.-N.; Vogt, F. Z. Chem. 1981, 21. 77. 20. Post, M. F. M.; Nanne, J. M. Patent DE 2 913 552, 1979. 21. Post, M. F. M.; Nanne, J. M. Can. Pat. 1 135 679, 1982. 22. Roscher, W.; Bergk, K.-H.; Pilchowski, V.; Schwieger, W.; Wolf, F.; Fürtig, H.; Hädicke, U.; Höse, W.; Krüger, W.; Chojnacki, K.-H. Patent DD-WP 207 186, 1984. 23. Roscher, W.; Bergk, K.-H.; Pilchowski, V.; Schwieger, W.; Wolf, F.; Fürtig, H.; Hädicke, U.; Höse, W.; Krüger, W.; Chojnacki, K.-H. Patent DD-WP 207 185, 1984. 24. Kerr, G. T.; Rollmann, L. D. Patent DE 2 705 436, 1978. 25. Klotz, M. R. U.S. Patent 4 377 502, 1983. 26. Whittam, T. V. Patent EP 59359, 1982. 27. Hugiwara, H.; Kiyozumi, Y.; Kurila, M.; Sato, T.; Shimudu, H.; Szuki, K.; Shin Ch. Chem. Letters 1981, 11, 1653. 28. Roscher,W.; Bergk, K.-H.; Pilchowski, V.; Schwieger, W.; Wolf, F.; F ü i g , H.; Häicke, U.; Höse,W.;Krüger, W.; Chojnacki, K.-H. Patent DD-WP 207 184, 1984. 29. Lowe, B.M.;Aroya, M. Patent EP 77624, 1983. 30. Grose, R. W.; Flanigen, Ε. M. U.S. Patent 4 061 724, 1977. 31. Bergk, K.-H.; Schwieger, W. Abstr. Internat. Conf. on Zeolites, Portoroze, 1984. 32. Jacobs, P.; Martens, A. I. A. In Synthesis of Highsilica Aluminosilicate Zeolites; Dellmann B. and Yales, I. T. Eds.; Studies in Surface Science and Catalysis, Vol. 35, Elsevier (1987). 33. Kokotailo, G. T.; Meier, W. M. Chem. Soc. Spec. Publ. 1980, 33, 13 34. Koningsveld, H. van; Jansen, J. C.; Bekkum, H. van Zeolites 1987, 7, 564. 35. Corbin, D. R.; Burgess, B. F.; Vega A. J.; Farlee, R. D. Analytical Chemistry 1987, 59, 2722. 36. Hunger, M.; Kärger, J.; Pfeifer, H.; Caro, J.; Zibrowius, B.; Bülow, M.; Mostowicz, R. J. Chem. Soc., Faraday Trans.I, 1987, 83, 3459. 37. Freude, D.; Haase, J.; Klinowski, J.; Carpenter, Τ. Α.; Ronikier, G. Chem. Phys. Letters 1985 119, 365. 38. Freude, D.; Hunger M.; Pfeifer, H. Proceedings of the Fourth International Symposium on Magnetic Resonance in Colloid and Interface Science, Münster, July 1986; Z. Physik. Chem. NF 1987, 152, 171. 39. Hunger, M.; Freude, D.; Frohlich, T.; Pfeifer, H.; Schwieger, W. Zeolites 1987, 7, 108. RECEIVED December 22, 1988


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