Properties of Aluminum-Deficient Large-Port Mordenites - Advances in

40 Properties of Aluminum-Deficient

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Large-Port Mordenites W. L. KRANICH, Y. H. MA, L. B. SAND, A. H. WEISS, and I. ZWIEBEL Department of Chemical Engineering, Worcester Polytechnic Institute, Worcester, Mass. 01609 A series of aluminum-deficient mordenites, ranging in Si/Al ratio from 6 to greater than 600, has been prepared by ther mal and acid treatment of H-mordenite. The series has been characterized for cumene adsorption, catalytic activity for cumene cracking and hydrocracking, and catalytic activity for butene isomerization. Removal of aluminum from the lattice results in diminished cumene adsorptive capacity at a given pressure for cumene pressures above 0.15 torr, but increased capacity at low pressures. Both cracking and hy drocracking activity decrease with decreasing aluminum content at high Si/Al ratios. Initial leaching of H-mordenite gives increased isomerization activity, but continued de cationization results in diminished activity.

Ο e v e r a l authors h a v e r e p o r t e d o n changes i n characteristics o f m o r d e n i t e s ^

as a l u m i n u m is r e m o v e d f r o m t h e i r structure b y l e a c h i n g w i t h m i n

e r a l a c i d . S a n d ( 6 ) , B e l e n ' k a y a et al. (3),

and Frilette and R u b i n (5)

d e s c r i b e d t h e a c i d l e a c h i n g of mordenites p r o d u c i n g S i / A l ratios u p t o a b o u t 15. B e e c h e r , V o o r h i e s , a n d E b e r l y ( 2 ) r e p o r t e d o n t h e c a t a l y t i c a c t i v i t y of p a l l a d i u m s u p p o r t e d o n a m o r d e n i t e w h i c h h a d a S i / A l "sev e r a l - f o l d greater t h a n 5." W e l l e r a n d B r a u e r ( 8 )

recently

described

c a t a l y t i c experiments o n m o r d e n i t e l e a c h e d to a r a t i o of a b o u t 9. A l t h o u g h B a r r e r a n d M a k k i ( 1 ) s u c c e e d e d i n r e d u c i n g the a l u m i n u m content of c l i n o p t i l o l i t e essentially to zero, the c h a r a c t e r i z a t i o n of a f u l l y d e c a t i o n i z e d m o r d e n i t e has n o t b e e n r e p o r t e d . I n t h e present s t u d y , b y use of a c o m b i n a t i o n o f t h e r m a l a n d a c i d treatments, a series of l a r g e - p o r t m o r d e n i t e s has b e e n p r e p a r e d d o w n to a m a t e r i a l w i t h essentially n o r e s i d u a l a l u m i n u m b u t w h i c h retains t h e m o r d e n i t e c r y s t a l structure as d e t e r m i n e d b y x - r a y p o w d e r d i f f r a c t i o n 502 In Molecular Sieve Zeolites-I; Flanigen, E., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

40.

Aluminum-Deficient

KRANiCH E T A L .

Large-Port

503

Mordenites

a n d s i n g l e - c r y s t a l e l e c t r o n d i f f r a c t i o n . L a r g e - p o r t m o r d e n i t e s are d e f i n e d as those w h i c h sorb m o l e c u l e s l a r g e r t h a n 5 A i n t o the 1 2 - m e m b e r e d channels, as c o n t r a s t e d w i t h those w h i c h sorb o n l y s m a l l e r s u c h as m e t h a n e

(6).

ring

molecules

T h e series has b e e n s y s t e m a t i c a l l y i n v e s t i g a t e d

for its a d s o r p t i v e a n d c a t a l y t i c p r o p e r t i e s at b o t h h i g h a n d l o w t e m p e r a tures. P r e l i m i n a r y results are r e p o r t e d i n this p a p e r . A s a l u m i n u m is r e m o v e d , its p l a c e i n the l a t t i c e is t a k e n b y h y d r o g e n i n h y d r o x y l groups as s h o w n b y i n f r a r e d a b s o r p t i o n spectra.

I n the

o r i g i n a l H - m o r d e n i t e , the s t r u c t u r e i n the v i c i n i t y of the a l u m i n u m m a y


be represented b y ι

—βί ο I

I H +O 3

ι

—Si—Ο—A1-—O—Si— ' Ο ' —Si—

I

As charges moved.

the a l u m i n u m is r e m o v e d

f r o m the s t r u c t u r e , the

w h i c h r e s u l t i n the e x c h a n g e a b l e The

fully

decationized

mordenite

unbalanced

cations are successively (aluminum-free)

may

re be

r e p r e s e n t e d as ι

—βί

ο

I

Η

—Si—OH '

I HO—Si—

Η Ο

'

I —Si— T h i s is a s i m i l a r s t r u c t u r a l a l t e r a t i o n to t h a t p r o p o s e d b y B a r r e r a n d Makki (I)

for c l i n o p t i l o l i t e .

A l t h o u g h n o m a j o r d i s r u p t i o n of the c r y s t a l l a t t i c e occurs, as e v i d e n c e d b y s t a b i l i t y of the x - r a y p a t t e r n , there are s i g n i f i c a n t

changes

in ionic character a n d charge distribution. These m a y be expected

to

l e a d to changes i n the a d s o r p t i v e a n d c a t a l y t i c b e h a v i o r of the m o r d e n i t e .

In Molecular Sieve Zeolites-I; Flanigen, E., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

504

MOLECULAR SIEVE ZEOLITES

Table I.

1

D a t a on Hydrogen-Exchanged Large-Port Partial

Sample

No.

Wt. % Al Oz

Unit Cell

2


1 (starting material) 2 3 4 5

Materials

11.24

Composition

Na o.48H 6.i9Al .67Si4o ex

n o t heat t r e a t e d 6.90 1.99 1.42 0.10

ex

H H H Η

eX

4.ooAl4.ooSl40 i.i4Ali.i Si o.8oAlo.8oSl40 ο.ΟβΑ1ο. 06^140

e x

ex

6

4

4 0

βχ

Preparation

T h e b a s i c m a t e r i a l for p r e p a r a t i o n of the series w a s a h y d r o g e n e x c h a n g e d m o r d e n i t e ( L o t N o . H B - 3 3 - 3 6 ) o b t a i n e d f r o m the N o r t o n C o . Its c h e m i c a l analysis is as f o l l o w s : 7 2 . 2 8 % S i 0 , 9 . 8 % A 1 0 , 0 . 2 6 % 2

T i 0 , 0.08% F e 0 , 0.37% N a 0 , 12.09% L . O . I . 2

2

3

2

2

3

N o other phases w e r e

d e t e c t e d b y x - r a y d i f f r a c t i o n analysis; the presence of 5 - 1 0 %

of a m o r

p h o u s m a t e r i a l was e s t i m a t e d b y m i c r o s c o p i c e x a m i n a t i o n . T h e treat ments o n this starting m a t e r i a l h a d n e g l i g i b l e effect o n the T i 0 a n d r e d u c e d the F e 0 2

3

2

content

a n d N a 0 content to less t h a n 0 . 0 1 % . 2

T h e A 1 0 content, r e p o r t e d on a n a n h y d r o u s basis, of the a l u m i n u m 2

3

deficient m o r d e n i t e s w a s o b t a i n e d b y x - r a y fused

fluorescence

analysis u s i n g

l i t h i u m tetraborate discs w i t h a w o r k i n g c u r v e established o n

m i x t u r e s of 2 c h e m i c a l l y a n a l y z e d H - m o r d e n i t e s of e n d - m e m b e r p o s i t i o n (11.24 a n d 0 . 1 0 %

A1 0 ). 2

3

com

G l a s s discs w e r e p r e p a r e d b y c a l

c i n i n g the m o r d e n i t e p o w d e r samples at 1 1 0 0 ° C for 1 h o u r , f u s i n g a m i x t u r e of 2 grams of m o r d e n i t e a n d 10 grams of l i t h i u m tetraborate at 1300 ° C , a n d p o u r i n g the l i q u i d into a graphite m o l d k e p t at r e d heat i n a k i l n . T h e b o t t o m of the glass d i s c was p o l i s h e d flat before analysis. N o significant changes i n l a t t i c e parameters or d e g r a d a t i o n of the c r y s t a l structure w a s n o t e d b y x - r a y d i f f r a c t i o n analysis. Increases i n d i f f r a c t i o n p e a k intensities of 110, 200, a n d 020 r e s u l t e d f r o m the treatments. S u m m a tions of p e a k intensities of t h e m a j o r diffractions f r o m 110, 200, 020, 111, 510, 0 2 2 , 6 0 0 , a n d 620 w e r e o b t a i n e d a n d c o m p a r e d w i t h those of the start ing material (2 — 1 0 0 ) . T h e d a t a o n s a m p l e p r e p a r a t i o n a n d analysis are s u m m a r i z e d i n T a b l e I.

A 7 0 0 ° C t h e r m a l treatment was u s e d for a l l samples except

S a m p l e N o . 3 w h i c h w a s t r e a t e d at 500 ° C .

D e t a i l s o n the p r e p a r a t i o n

of a l u m i n u m - d e f i c i e n t m o r d e n i t e s are g i v e n b y C h a n g a n d S a n d

(4).

T h e p a r t i c l e size r a n g e of the h y d r o g e n - e x c h a n g e d m o r d e n i t e u s e d as the s t a r t i n g m a t e r i a l is 5 - 1 0 / x m w i t h a n average m e a n d i a m e t e r of 7/xm. T h e p a r t i c l e s consist of 4 0 % of single crystals a n d 6 0 % of c r y s t a l aggregates.


40.

Aluminum-Deficient

KRANiCH E T A L .

Large-Port

505

Mordenites

Mordenite and Aluminum-Deficient Derivatives


Si/Al

Σ XRD

Peaks

Acid

Treat.

6

100

6N H S 0

10 35 50 >600

98 118 141 102

IN 6N 6N QN

2

4

ambient

H C 1 boil 2 H C 1 boil 6 HNO3 b o i l HNO3 b o i l

hrs. hrs. 12 h r s . 6 hrs.

T h e severe a c i d treatments s e p a r a t e d the aggregates i n t o single crystals i n a size range of 0.5-10yx,m w i t h a n average m e a n d i a m e t e r of 3/rni. T w e n t y p e r cent of the crystals are e u h e d r a l a c i c u l a r a n d the r e m a i n d e r are e q u a n t a n d a n h e d r a l . I n o r d e r to i n v e s t i g a t e changes i n the characteristics of the m o r d e n i t e as a l u m i n u m w a s extracted, studies w e r e m a d e of the a d s o r p t i o n

of

c u m e n e , the c r a c k i n g a n d h y d r o c r a c k i n g of c u m e n e , a n d the i s o m e r i z a t i o n of 1-butene. Experimental

Methods

C u m e n e a d s o r p t i o n experiments w e r e c a r r i e d out i n a m i c r o b a l a n c e a p p a r a t u s e q u i p p e d w i t h a q u a r t z s p r i n g w h o s e deflections w e r e meas u r e d w i t h a cathetometer.

T h e u n i t also i n c l u d e d a v a c u u m

system

c a p a b l e of r e d u c i n g the pressures to b e l o w 0.01 m i c r o n , a n d a B a r a t r o n c o n t i n u o u s pressure-sensing d e v i c e w i t h a s e n s i t i v i t y of 1 m i c r o n . a m o u n t a d s o r b e d was m e a s u r e d b y s p r i n g deflection, a n d c h e c k e d m a t e r i a l b a l a n c e o n the gas p h a s e b a s e d o n a n a p p r o x i m a t e v o l u m e of 600 cc.

The by

chamber

T h e pressure measurements w e r e n o t e d at r e g u l a r

intervals u n t i l " e q u i l i b r i u m " was r e a c h e d (less t h a n 1 m i c r o n change i n 5 m i n u t e s ) . T h e s e pressure vs. t i m e d a t a w e r e u s e d for d i f f u s i v i t y c a l culations. Cumene Cracking and Hydrocracking. C r a c k i n g studies w e r e c o n d u c t e d i n a t u b u l a r stainless steel m i c r o r e a c t o r i n s e r t e d i n a

bronze

b l o c k . T h e entire a s s e m b l y was c o n s t r u c t e d w i t h i n the o v e n of a P e r k i n E l m e r M o d e l 880 gas c h r o m a t o g r a p h . W i t h this c o n s t r u c t i o n , the reactor c o u l d be f e d i n 5-μ\ pulses d i r e c t l y f r o m the i n j e c t i o n b l o c k into a stream of h y d r o g e n o r h e l i u m

flowing

at a rate of 282 s t a n d a r d cc p e r m i n u t e . A f r a c t i o n of the p r o d u c t gases was c o n d u c t e d d i r e c t l y to the c h r o m a t o g r a p h c o l u m n . T h e catalyst, d i l u t e d 1000:1 w i t h glass s a n d , was p r e t r e a t e d at 538 ° C for 15 hours w i t h h y d r o g e n or h e l i u m p r i o r to use.



506


T y p i c a l l o a d i n g for c u m e n e c o n v e r s i o n of 0.1 to 1.0% w a s 4 X

1

10~

4

g r a m of catalyst at a t e m p e r a t u r e of a b o u t 371 ° C a n d a t m o s p h e r i c p r e s sure. W i t h o u t catalyst, the b e n z e n e y i e l d f r o m t h e r m a l c r a c k i n g at 421 ° C was o n l y a b o u t 0 . 0 0 2 %

of the c u m e n e f e d .

T h e very small charge

of

catalyst a l l o w e d s t u d y of i n t r i n s i c a c t i v i t y d e c l i n e at l o w c o n v e r s i o n levels w h i l e o p e r a t i n g at temperatures of p r a c t i c a l interest w h i c h w e r e h i g h e n o u g h to a v o i d d e s o r p t i o n p r o b l e m s .

U n f o r t u n a t e l y , this same

catalyst charge r e s u l t e d i n a n u n c e r t a i n t y i n mass as great as

small ±40%,

w i t h a c o r r e s p o n d i n g u n c e r t a i n t y i n c o m p a r i s o n of different i n d i v i d u a l catalyst charges. Successive pulses of c u m e n e w e r e f e d to the reactor u n t i l t h e i n i t i a l h i g h a c t i v i t y l e v e l h a d b e e n r e d u c e d to a p p r o x i m a t e l y steady state. B u t e n e I s o m e r i z a t i o n . A steady-flow t u b u l a r reactor w a s u s e d for studies of i s o m e r i z a t i o n of 1-butene to cis- a n d frans-2-butene. T h e catalyst p o w d e r w a s pressed i n t o a t h i n d i s k , c r u s h e d , screened, a n d d r i e d at 200 ° C .

A f t e r b e i n g d i l u t e d a b o u t 5 to 1 w i t h glass beads

a n d p a c k e d into a c y l i n d r i c a l flow reactor, the catalyst was a c t i v a t e d i n p l a c e b y h e a t i n g i n a s t r e a m of d r y h e l i u m for 2 hours at 3 5 0 ° C . T h e catalyst mass of a b o u t 0.75 g r a m was t h e n b r o u g h t to the r e a c t i o n t e m p e r a t u r e a n d exposed to a m i x t u r e of 1-butene ( 132 c c / m i n ) a n d h e l i u m (260 c c / m i n ) .

T e m p e r a t u r e w a s m a i n t a i n e d constant b y i m m e r -

s i o n of the reactor i n a fluidized s a n d b a t h .


40.

Aluminum-Deficient

KRANiCH E T A L .

Large-Port

507

Mordenites

T h e r a p i d decrease i n a c t i v i t y c h a r a c t e r i s t i c of fresh, a c t i v a t e d c a t alysts was f o l l o w e d b y t r a p p i n g a n d a n a l y z i n g successive gas samples at m e a s u r e d i n t e r v a l s i n a gas c h r o m a t o g r a p h .

T h e butene—helium m i x t u r e

was a l l o w e d to f l o w over the catalyst for s e v e r a l hours, u n t i l samples s h o w e d essentially n o c h a n g e i n c o m p o s i t i o n .

successive

Steady-state

ac-

tivities w e r e m e a s u r e d at several temperatures. Results


Cumene Adsorption. C u m e n e a d s o r p t i o n e q u i l i b r i u m d a t a are p r e sented i n t h e f o r m of isotherms at r o o m t e m p e r a t u r e i n F i g u r e 1. A t the h i g h - p r e s s u r e e n d of the g r a p h ( a b o v e P / P

0

=

0.15) the a d -

s o r p t i o n c a p a c i t y at a g i v e n pressure decreases m a r k e d l y as a l u m i n u m is l e a c h e d f r o m the m o r d e n i t e .

I n m i d - r a n g e , h o w e v e r , the curves

so that at l o w pressures ( b e l o w P / P = 0

creases as a l u m i n u m is r e m o v e d .

cross,

0.01) the a d s o r p t i o n c a p a c i t y i n -

T h i s effect is p a r t i c u l a r l y m a r k e d i n

the f u l l y d e c a t i o n i z e d m o r d e n i t e . T h i s m a t e r i a l adsorbs as m u c h c u m e n e at a pressure of 0.005 torr as the other m o r d e n i t e s a d s o r b at pressures a b o u t 50 times as great. E f f e c t i v e diffusion coefficients w e r e c a l c u l a t e d f r o m a d s o r p t i o n rate data on 3 materials based on a spherical model.

T h e crystallites w e r e

a s s u m e d to b e spheres w i t h a d i a m e t e r of 3.0 m i c r o n s . F o r c o m p a r i s o n , the diffusion coefficients w e r e c a l c u l a t e d f r o m e a c h a d s o r p t i o n rate c u r v e at the p o i n t w h e r e the c u m e n e u p t a k e w a s h a l f of its e q u i l i b r i u m v a l u e . T h e results are s h o w n i n T a b l e I I . Table II.

Effective Cumene Diffusion Coefficients at 5 0 % D X W

% Al 0 2

12

3

11.24 6.90 1.42

Uptake

Cm*/Sec

10.0 5.2 3.4

T h e results i n d i c a t e t h a t the o r i g i n a l m o r d e n i t e p e r m i t s s i g n i f i c a n t l y easier diffusion of c u m e n e

t h a n does l e a c h e d m a t e r i a l . F u r t h e r w o r k

is u n d e r w a y to c l a r i f y this r a t h e r u n e x p e c t e d r e l a t i o n s h i p . Cumene C r a c k i n g . F i g u r e s 2 a n d 3 s h o w c u m e n e c o n v e r s i o n

per

g r a m of catalyst for runs i n H e a n d i n H , r e s p e c t i v e l y , at 3 6 0 ° C as a 2

f u n c t i o n of the c u m u l a t i v e q u a n t i t y of c u m e n e i n j e c t e d over e a c h c a t alyst s t u d i e d . A c t i v i t y loss c o u l d b e p a r t i a l l y r e c o v e r e d to as m u c h as 50%

of o r i g i n a l b y h e a t i n g i n H

2

at 538 ° C , i n d i c a t i n g t h a t b o t h the

f o r m a t i o n of d i m e r s a n d h i g h e r , as w e l l as i r r e v e r s i b l e c o k i n g , c o n t r i b u t e d to a c t i v i t y loss. T h e activities of the f u l l y - l e a c h e d samples a p p e a r to b e almost the same i n H

2

a n d i n H e ; the a p p a r e n t l y e n h a n c e d r e a c t i v i t y i n



508


Figure 2. H

2

Cumene cracking

1

activity

of the catalysts c o n t a i n i n g m o r e a l u m i n a is w i t h i n the l i m i t s of e r r o r

of catalyst mass as d e s c r i b e d p r e v i o u s l y . A r r h e n i u s plots of n o n d e c l i n i n g a c t i v i t y d a t a c a l c u l a t e d as r a t e constants w e r e fitted for the 0.1 a n d 1.42% A 1 0 2

3

first-order

catalysts.

Benzene

p r o d u c t i o n o n b o t h catalysts c a n be fitted to the same a c t i v a t i o n energy of 15.8 K c a l / m o l e for o p e r a t i o n i n b o t h H

2

a n d H e i n the r a n g e

of

347°-450°C. B e e c h e r et al. ( 2 ) i n v e s t i g a t e d 1 / 2 % Pd

o n ΑΙ-deficient H - m o r d e n i t e

r a t i o s e v e r a l - f o l d greater t h a n 5"). greatly

improved

ing

of H - m o r d e n i t e s

obtained

. . .

to g i v e

1/2%

a

Si/Al

T h e y s h o w e d t h a t the a c i d t r e a t m e n t

c a t a l y t i c a c t i v i t y for

d e c a l i n . T o p c h i e v a et al. ( 7 )

P d on H-mordenite and

("acid-leached

hydrocracking

n-decane

and

studied pulse microreactor cumene crack

h a v i n g S i / A l ratios of 5, 6.5, a n d 9.

The

data

( b u t n o t p r e s e n t e d ) i m p l i e d that c a t a l y t i c a c t i v i t y i n c r e a s e d

w i t h increasing S i / A l ratio. Similar w o r k b y W e l l e r and Brauer (8)

in

t h e r a n g e of 7.5 to 9 S i / A l c o r r o b o r a t e d the i n c r e a s e d c r a c k i n g a c t i v i t y of a l u m i n a - d e f i c i e n t m o r d e n i t e s , i n this case for h e x a n e c r a c k i n g . I n the present w o r k , S i / A l ratios v a r i e d f r o m 6 to 600.

Neither

i n i t i a l a c t i v i t y levels n o r s u s t a i n e d o p e r a t i o n s h o w e d a n a c t i v i t y a d v a n tage f o r A 1 0 2

3

removal.

c r e a s i n g S i / A l at the 1 %

R a t h e r , a c t i v i t y a p p e a r e d to decrease w i t h i n cumene conversion level, both w i t h H

with helium.


2

and

40.

KRANiCH E T A L .

Aluminum-Deficient

Large-Port

Mordenites

509

T h e m a t e r i a l s selected f o r this p r e l i m i n a r y i n v e s t i g a t i o n w e r e chosen so t h a t S i / A l ratios w o u l d b e separated b y a b o u t a n o r d e r o f m a g n i t u d e — i.e., 6, 50, a n d 600. T h e r a n g e s t u d i e d b y t h e other investigators c i t e d w a s b e t w e e n t h e first 2 of these points.

T h i s w o r k does n o t p r e c l u d e

t h e p o s s i b i l i t y t h a t t h e increase i n a c t i v i t y w i t h d e c r e a s i n g a l u m i n u m content o b s e r v e d b y t h e others m i g h t exist also i n t h a t same r a n g e f o r o t h e r m a t e r i a l s . W e l l e r a n d B r a u e r ( 8 ) i n fact d i d r e p o r t a m a x i m u m i n c r a c k i n g a c t i v i t y a t a S i / A l r a t i o of a b o u t 8.7. W o r k is c o n t i n u i n g i n this range. Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 1, 2015 | http://pubs.acs.org Publication Date: August 1, 1974 | doi: 10.1021/ba-1971-0101.ch040

Butene Isomerization.

INITIAL DEACTIVATION.

C o n v e r s i o n of

1-bu-

tene to t h e 2-butenes w a s m u c h m o r e r a p i d i n i t i a l l y t h a n i n t h e steady state f o r a l l catalysts at a l l temperatures s t u d i e d . I n i t i a l a c t i v i t y o f t h e f u l l y - l e a c h e d m a t e r i a l w a s m u c h greater t h a n t h a t o f t h e o r i g i n a l H - m o r -

Figure 3.

Cumene hydrocracking

activity



510


Figure 4. denite.

1-Butene isomerization

Approximately 4 0 %

1

activity

of the 1-butene was c o n v e r t e d at a t e m -

p e r a t u r e of 20 ° C b y 0.75 g r a m of l e a c h e d m a t e r i a l after 4 m i n u t e s o n stream.

I n contrast, o n l y a b o u t 1 0 %

was c o n v e r t e d u n d e r the

c o n d i t i o n s over the u n t r e a t e d H - m o r d e n i t e .

same

Catalysts d i d not reach a

steady state a c t i v i t y i n the r a n g e 2 0 ° - 7 0 ° C , b u t c o m p l e t e l y d e a c t i v a t e d w i t h t i m e . A b o v e 90 ° C , a steady-state a c t i v i t y w a s r e a c h e d w h i c h p e r sisted for m a n y hours w i t h o n l y s l i g h t decay. A p p r o x i m a t e l y 7 5 % of the lost a c t i v i t y c o u l d b e r e c o v e r e d b y p u r g i n g for several hours w i t h d r y h e l i u m . I t is b e l i e v e d that the lost act i v i t y results p r i m a r i l y f r o m p o l y m e r i z a t i o n of the butènes to octenes, docecenes, a n d h i g h e r w h i c h cannot r e a d i l y escape f r o m the pores a n d thus p r e v e n t access to the i n n e r a c t i v e sites. O n p r o l o n g e d p u r g i n g i n a h e l i u m s t r e a m , these s o m e w h a t v o l a t i l e p o l y m e r s s l o w l y diffuse

out

of the catalyst. A b o v e a b o u t 90 ° C , the v o l a t i l i t y of the l o w m o l e c u l a r w e i g h t p o l y m e r b y p r o d u c t s is sufficient to p e r m i t t h e m to diffuse s l o w l y b u t s t e a d i l y o u t of the pores a n d a l l o w c o n t i n u i n g i s o m e r i z a t i o n to occur. ence of v o l a t i l e p o l y m e r s i n catalyst w h i c h h a d r e a c h e d

T h e pressteady-state

a c t i v i t y was c o n f i r m e d b y s c a n n i n g d e a c t i v a t e d catalyst at v a r i o u s tern-


40.

Aluminum-Deficient

KRANiCH E T A L .

Large-Port

peratures i n a mass spectrometer.

A t 25 ° C , C

s e r v e d ; at 5 0 ° C ,

appeared;

C12 compounds

significant peaks as h i g h as the C STEADY STATE.

4 0

8

511

Mordenites

hydrocarbons were

a n d at 7 5 ° C there

obwere

range.

T h e v a r i a t i o n of r e a c t i o n rate constant w i t h

centage a l u m i n a at the steady state is s h o w n i n F i g u r e 4.

per-

A s the m o r -

d e n i t e is d e c a t i o n i z e d , the a c t i v i t y increases to a m a x i m u m a n d t h e n falls w i t h f u r t h e r l e a c h i n g . T h i s m a y b e e x p l a i n e d as a n i n i t i a l a c t i v a t i o n of i n t e r n a l sites b y the a c i d a n d heat treatment, f o l l o w e d b y s o m e loss i n a c t i v i t y as t h e Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 1, 2015 | http://pubs.acs.org Publication Date: August 1, 1974 | doi: 10.1021/ba-1971-0101.ch040

n u m b e r of a c i d sites is r e d u c e d . A m a r k e d effect o n steady-state s e l e c t i v i t y , m e a s u r e d as t r a n s / c i s , results f r o m r e d u c t i o n i n a l u m i n u m . T h e s e l e c t i v i t y of the f u l l y - l e a c h e d catalyst is a b o u t 2.4, w h i l e that of the H - m o r d e n i t e is a b o u t 1.3. A p p a r e n t s e l e c t i v i t y of the f u l l y - l e a c h e d f r e s h l y a c t i v a t e d m a t e r i a l was e v e n m o r e m a r k e d t h a n t h a t i n the steady state. I n the first samples f r o m the fresh catalyst, n o cw-2-butene was o b s e r v e d e v e n t h o u g h h a l f of the 1-butene w a s c o n v e r t e d . A t present, i t is not k n o w n w h e t h e r this is o b s e r v e d

because the

cis i s o m e r is not f o r m e d at a rate m e a s u r a b l e r e l a t i v e to trans or w h e t h e r the cis is f o r m e d , t h e n s t r o n g l y a d s o r b e d or q u i c k l y p o l y m e r i z e d . Conclusions A l u m i n u m c a n be l e a c h e d f r o m H - m o r d e n i t e almost c o m p l e t e l y a c o m b i n a t i o n of t h e r m a l a n d a c i d treatment.

by

N o significant v a r i a t i o n

of the b a s i c m o r d e n i t e lattice occurs as a r e s u l t of this treatment, e v e n w h e n the final S i / A l r a t i o is greater t h a n 600. B o t h c a t a l y t i c a n d a d s o r p t i v e p r o p e r t i e s of the H - m o r d e n i t e

are

a l t e r e d s i g n i f i c a n t l y as a l u m i n u m is r e m o v e d , p a r t i c u l a r l y as d e c a t i o n i z a t i o n nears c o m p l e t i o n . A s S i / A l is i n c r e a s e d b y l e a c h i n g , a d s o r p t i o n c a p a c i t y f o r

cumene

at a m b i e n t t e m p e r a t u r e a n d a g i v e n pressure is e n h a n c e d at v e r y

low

pressures, b u t d i m i n i s h e d at pressure a b o v e 0.15 torr. L e a c h i n g of

H - m o r d e n i t e i n i t i a l l y increases

c a t a l y t i c a c t i v i t y for

1-butene i s o m e r i z a t i o n , b u t a b o v e a S i / A l r a t i o of a b o u t 15, the a c t i v i t y diminishes. A t h i g h S i / A l ratios, r e m o v a l of a l u m i n u m also results i n a loss of c r a c k i n g a n d h y d r o c r a c k i n g a c t i v i t y for c u m e n e .

T h e disappearance

of

a c i d sites w i t h d e c a t i o n i z a t i o n c o u l d account for loss of a c t i v i t y i n b o t h cracking and isomerization. Studies are c o n t i n u i n g w i t h the objectives

of f u r t h e r d e f i n i n g the

results o n a d s o r p t i o n a n d catalysis a n d e x p l a i n i n g the p h e n o m e n a s e r v e d i n terms of s t r u c t u r a l changes.


ob-

512

M O L E C U L A R SIEVE ZEOLITES

1

Acknowledgment Techniques for the preparation of the aluminum-deficient mordenites were developed

u n d e r a contract w i t h t h e N o r t o n C o . T h e f o l l o w i n g

students at W o r c e s t e r P o l y t e c h n i c Institute p e r f o r m e d t h e e x p e r i m e n t a l w o r k : H . C h a n g , J . T a m b o l i , J . R. Pratt, D . Kremer, H . Bierenbaum, a n d S. C h i r a m o n g k o l . J . R . P r a t t a n d S. C h i r a m o n g k o l w e r e s u p p o r t e d b y a N a t i o n a l Science

F o u n d a t i o n grant for Undergraduate Research

Par

ticipation. H . Bierenbaum was supported b y a n N D E A Title I V F e l l o w Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 1, 2015 | http://pubs.acs.org Publication Date: August 1, 1974 | doi: 10.1021/ba-1971-0101.ch040

ship.

T h e cooperation

o f t h e f o l l o w i n g N o r t o n C o . scientists i n t h e

analysis o f t h e m o d i f i e d m o r d e n i t e s is a p p r e c i a t e d : R . H . B e n s o n , A . J . Regis, W . H . Gerdes.

Contributions to the design a n d construction of

apparatus b y C . A . Keisling, a n d the collection of adsorption data b y R. K n a p i k are acknowledged.

Literature Cited (1) Barrer, R. M., Makki, M. B., Can. J. Chem. 1964, 42, 1481. (2) Beecher, R., Voorhies, Α., Eberly, P., Symp. New Chem. Hydrogen Process. Petrol., ACS, Chicago, Ill, September 11-15, 1967. (3) Belenkaya, I. M., Dubinin, M. M., Krishtofori, I. I., Izv. Akad. Nauk SSSR 1967, 10, 2164-71. (4) Chang, H. D., Sand, L. B., in preparation. (5) Frilette, V. J., Rubin, M. K., J. Catalysis 1965, 4, 310. (6) Sand, L. B., "Molecular Sieves," Society of the Chemical Industry Spec. Publ., 71-77, 1968. (7) Topchieva, Κ. V., Romanovsky, Β. V., Piquzova, L. I., Thoang, HoSi, Bizreh, Y. W., Intern. Congr. Catalysis, 4th, Moscow, USSR, 1968. (8) Weller, S. W., Brauer, J. M., AIChE Annual Meeting, 62nd, Washington, D. C., November 16-20, 1969. RECEIVED February 25, 1970.

Discussion A l f r e d E . Hirschler ( S u n O i l Co., Marcus Hook, P a . ) : I wonder if y o u c o u l d b e a little m o r e specific o n t h e m a n n e r i n w h i c h t h e t h e r m a l a n d a c i d l e a c h i n g p r o c e d u r e s w e r e c o m b i n e d i n o b t a i n i n g t h e samples described? L . B . S a n d : A t y p i c a l p r o c e d u r e w a s 7 0 0 ° C f o r t w o hours i n a d r y n i t r o g e n p u r g e f o l l o w e d b y b o i l i n g i n 6N H C 1 f o r several hours. D e l i n e a t i o n o f parameters c a n b e f o u n d i n H . D . C h a n g s P h D thesis o n file at t h e W . P . I , l i b r a r y . B. C . Gates: (University of Delaware, N e w a r k , D e l . 19711): Y o u r e p o r t e d d a t a f o r c r y s t a l l i t e size d i s t r i b u t i o n . H o w d i d y o u measure c r y s t a l l i t e sizes?

D i d y o u a t t e m p t s i z e - f r a c t i o n a t i o n o f t h e crystallites?


40.

KRANiCH E T A L .

Aluminum-Deficient

Large-Port

Mordenites

513

L . B. Sand: C r y s t a l l i t e sizes w e r e m e a s u r e d w i t h a n o p t i c a l m i c r o scope. N o f r a c t i o n a t i o n w a s a t t e m p t e d . J . R. Katzer ( U n i v e r s i t y of D e l a w a r e , N e w a r k , D e l . 1 9 7 1 1 ) :

You

refer to the fact that diffusivities w e r e m e a s u r e d a n d c o m m e n t that y o u are a t t e m p t i n g to e x p l a i n the v a r i a t i o n s f o u n d o n the basis of s t r o n g l y a d s o r b e d species b l o c k i n g the diffusion process.

D i d y o u measure b o t h

a d s o r p t i o n a n d d e s o r p t i o n rates, a n d i f y o u d i d , w h a t w e r e the r e l a t i v e values of the t w o rates? W. L . K r a n i c h : Because of l i m i t e d a v a i l a b i l i t y of s o r p t i o n a p p a r a t u s Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 1, 2015 | http://pubs.acs.org Publication Date: August 1, 1974 | doi: 10.1021/ba-1971-0101.ch040

w h e n this s t u d y was m a d e , w e d i d not take d e s o r p t i o n d a t a . I n v i e w of the results, w e r e c o g n i z e the s p e c i a l v a l u e of d e s o r p t i o n rates a n d h o p e to t a k e s u c h d a t a i n the f u t u r e . J . R. Katzer: W e are u s i n g a s i m i l a r e x p l a n a t i o n for our results o n the d e s o r p t i o n of b e n z e n e a n d c u m e n e f r o m H - m o r d e n i t e a n d h a v e r e p o r t e d this w o r k at the P u e r t o R i c o A . I . C h . E . m e e t i n g i n M a y , 1970. Eng.

Chem.

Fundamentals,

i n press.)

(Ind.

I t h i n k that this is a n i m p o r t a n t

factor. I f y o u c o u l d d o some d e s o r p t i o n measurements, the results w o u l d be v e r y h e l p f u l a n d w o u l d c l a r i f y y o u r s p e c u l a t i o n .

W e showed

quite

c l e a r l y t h a t benzene a n d c u m e n e molecules cannot counterdiffuse i n the H - m o r d e n i t e pores at reasonable temperatures.


Properties of Aluminum-Deficient Large-Port Mordenites - Advances in

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