Synthetic Erionite and Selective Hydrocracking - Advances in

73 Synthetic Erionite and Selective Hydrocracking H. E. ROBSON, G. P. HAMNER, and W. F. AREY, JR.

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Esso Research Laboratories, Humble Oil & Refining Co., Baton Rouge, La. 70821

Erionite has been synthesized at 100°-150°C from a (Νa,Κ) aluminosilicate gel with SiO /Al O = 10. X-ray and elec tron diffraction results on the product show intergrowths of the related offretite structure, which is a hrge-pore zeolite. Adsorption capacity for n-hexane is consistent with the density but adsorption rates are far slower than for zeolite A. Adsorption rates for n-octane are even slower but still better than for natural erionite. Hydrocracking tests on a C /C naphtha show strong selectivity for converting normal paraf fins to C4- gas, particularly propane. As temperature is in creased, other components of the naphtha feed are cracked and selectivity decreases. 2

2

3

5

6

R e d i t e A , a l t h o u g h a n excellent adsorbent, has never seen w i d e u s e as a catalyst f o r p e t r o l e u m processes.

T h i s is p r o b a b l y because o f its

l o w s i l i c a / a l u m i n a r a t i o w h i c h makes i t u n s t a b l e i n t h e h y d r o g e n f o r m . Nevertheless,

processes s u c h as octane i m p r o v e m e n t a n d p o u r p o i n t

r e d u c t i o n c o u l d benefit f r o m a catalyst w h i c h w o u l d operate o n l y o n straight-chain hydrocarbons—i.e.,

a catalyst b a s e d o n a s m a l l - p o r e zeo

lite. E r i o n i t e appears to b e t h e p r i m e c a n d i a t e f o r this service b e c a u s e i t has b o t h a t h r e e - d i m e n s i o n a l 5 - A p o r e system a n d h i g h s i l i c a content (Si0 /Al 0 2

2

Synthesis

3

~ 7 ) .

Experiments

T h e synthesis of erionite w a s r e p o r t e d b y Z h d a n o v (11)

i n 1965.

T h e m e d i u m w a s d e s c r i b e d as a m i x e d sodium—potassium a l u m i n o s i l i c a t e h y d r o g e l at 9 0 ° - 1 0 0 ° C

b u t f u r t h e r details are n o t g i v e n .

Breck a n d

417

Flanigen and Sand; Molecular Sieve Zeolites-II Advances in Chemistry; American Chemical Society: Washington, DC, 1971.

418

M O L E C U L A R SIEVE ZEOLITES

II

A c a r a ( 1 ) h a d r e p o r t e d earlier t h e synthesis of zeolite T , w h i c h appears to b e erionite as f a r as c a n b e seen f r o m t h e p r i n c i p a l x-ray lines. T h e results of o u r synthesis experiments are g i v e n i n F i g u r e 1, w h i c h plots 2 o f t h e 4 c o m p o s i t i o n v a r i a b l e s r e q u i r e d to d e s c r i b e t h e synthesis gel of 5 components ( N a 0 · K 2

2

0 · A1 0 2

3

· Si0

2

*H 0 ) .

T h e system i s

2

c o m p a r a t i v e l y less sensitive t o t h e other 2 c o m p o s i t i o n v a r i a b l e s : K (K 0 2

+

Na 0) 2

and H 0 / S i 0 . 2

2

2

0 /

E x p e r i m e n t s i n F i g u r e 1 a r e at 0.25

K 0 / ( K 0 -f- N a 0 ) ; t h e results w o u l d b e n e a r l y t h e same i f this ratio 2

2

2

w e r e 0.20 o r 0.30. B e y o n d this range, c r y s t a l l i z a t i o n o f other

zeolite

phases becomes p r e d o m i n a n t . Downloaded by PURDUE UNIV on October 25, 2016 | http://pubs.acs.org Publication Date: June 1, 1971 | doi: 10.1021/ba-1971-0102.ch073

Silica sol was the S i 0

2

source f o r a l l these experiments. A n a l u m i n a t e

liquor was prepared b y dissolving alumina trihydrate i n hot N a O H - K O H s o l u t i o n . A f t e r c o o l i n g t o r o o m t e m p e r a t u r e , the ( N a , K ) A 1 0 l i q u o r w a s 2

b l e n d e d w i t h 4 0 % s i l i c a s o l u s i n g a h i g h - s p e e d m i x e r . W a t e r content o f the synthesis g e l w a s h e l d t o a m i n i m u m ; r e d u c t i o n o f w a t e r has c o n sistently

g i v e n better erionite

H 0/Si0 2

2

crystallinity.

F o r high-silica formulas,

w a s 16; as s i l i c a w a s decreased, w a t e r content w a s r e d u c e d

u n t i l at the l o w s i l i c a e n d , H 0 / S i 0 2

2

= 6.

T h e g e l w a s c r y s t a l l i z e d i n c l o s e d containers to p r e v e n t e v a p o r a t i o n loss. C r y s t a l l i z a t i o n t i m e r a n g e d f r o m 1 to 5 days d e p e n d i n g o n g e l c o m p o s i t i o n a n d c r y s t a l l i z a t i o n temperature.

F i g u r e 1 shows t h e ranges of

g e l c o m p o s i t i o n w h e r e t h e p r o d u c t is s u b s t a n t i a l l y p u r e erionite. T h e b o u n d a r i e s are n o t sharp b u t rather represent areas of d e c r e a s i n g erionite crystallinity i n the product. I n c r e a s i n g the c r y s t a l l i z a t i o n t e m p e r a t u r e f r o m 1 0 0 ° t o 150 ° C sub s t a n t i a l l y increases t h e erionite c r y s t a l l i z a t i o n area.

J 10 2

2

good

ι

1

15

20

Si0 /Al 0 Figure 1.

A t 150 ° C ,

3

Erionite synthesis from silica sol, 0.25 K 0 / ( K 0 + minimum water 3

2


Nafi),

73.

ROBSON E T

Synthetic

AL.

Erionite

419

erionite p r o d u c t s w e r e o b t a i n e d w i t h 10 S i 0 / A l 0 a n d 16 h o u r s ' c r y s t a l 2

2

3

l i z a t i o n t i m e . T h e change i n s i l i c a content of t h e erionite p r o d u c t is o n l y f r o m 7 to 6 S i 0 / A l 0 2

Comparison

2

3

as t h e g e l changes f r o m 20 to 10 S i 0 / A l 0 . 2

with Natural

2

3

Erionite

N a t u r a l erionite, u n l i k e most other n a t u r a l zeolites, occurs i n deposits large e n o u g h a n d p u r e e n o u g h to b e u s e d f o r c o m m e r c i a l purposes ( 3 ) . S e v e r a l h i g h - q u a l i t y deposits are k n o w n i n N e v a d a a n d O r e g o n .

Natural


erionite has some properties w h i c h are definite l i a b i l i t i e s f o r c a t a l y t i c purposes. O b v i o u s l y , n a t u r a l erionite contains a w h o l e s p e c t r u m of i m p u r i t i e s s u c h as F e , T i , C a , M g , a n d C u w h i c h m a y b e

objectionable.

F u r t h e r , t h e n a t u r e of the f o r m a t i o n process p r a c t i c a l l y guarantees v a r i a t i o n i n q u a l i t y w i t h i n a single deposit (4).

S y n t h e t i c erionite, a l t h o u g h

m o r e expensive, s h o u l d b e d e p e n d a b l e i n q u a l i t y .

Table I.

Erionite X - R a y Diffraction Patterns

I/h hkl

d

100 101 002 110 102 200 201 103 202 210 211 300 212 104 302 220 213 310 204 311 312 400 214 401 402 410 322

11.47 9.37 7.55 6.61 6.30 5.72 5.35 4.61 4.56 4.326 4.158 3.814 3.754 3.587 3.401 3.304 3.278 3.173 3.148 3.106 2.923 2.860 2.842 2.811 2.675 2.497 2.479

Natural 100 8.5 7.8 41 4.9 5.3 6.9 4.1 5.8 25 11 14 40 21 0.8 17 6.2 6.6 13 3.3 6.5 27 21 22 7.3 5.6 8.8

Synthetic 100

*

4.0 41 2.8 3.3

* *

3.9 31 4.5* 12 36 15 0.6 11 1.3* 5.1 12

*

4.4 30 25 5.7* 7.1 5.6 10


420


II

A s e c o n d a n d m o r e subtle area o f difference is i n t h e c r y s t a l l o g r a p h y of the erionite p h a s e itself (10). T a b l e I c o m p a r e s x - r a y d i f f r a c t i o n i n t e n sities of l o w angle lines f o r a n a t u r a l erionite (Jersey V a l l e y , N e v . ) a n d a synthetic erionite p r e p a r e d at E s s o R e s e a r c h L a b o r a t o r i e s . T h e agree m e n t is q u i t e g o o d except f o r those lines w h i c h h a v e b e e n m a r k e d b y a n astrisk i n d i c a t i n g a n i n t e n s i t y of less t h a n h a l f o f that f o r n a t u r a l erionite. W i t h o u t e x c e p t i o n , the d e s i g n a t e d lines ( 101, 201, 103, 211, 213, 311, a n d 401) h a v e o d d values f o r t h e " 1 " i n d e x . F u r t h e r , t h e i r intensities are s u b s t a n t i a l l y less t h a n t h e reference. S u c h a n effect is u n d e r s t a n d a b l e i n v i e w o f t h e d i s t i n c t i o n b e t w e e n Downloaded by PURDUE UNIV on October 25, 2016 | http://pubs.acs.org Publication Date: June 1, 1971 | doi: 10.1021/ba-1971-0102.ch073

erionite a n d offretite structures p u b l i s h e d b y B e n n e t t a n d G a r d (2, 9 ) . T h e d e s i g n a t e d lines are f o r b i d d e n f o r t h e offretite structure.

G a r d has

e x a m i n e d o u r synthetic erionite p r o d u c t b y e l e c t r o n d i f f r a c t i o n a n d f o u n d " d i s o r d e r e d i n t e r g r o w t h w i t h w i d e l y v a r y i n g p r o p o r t i o n s of erionite a n d offretite structures" ( 8 ) . Adsorption

Properties

S i n c e offretite is a l a r g e - p o r e structure, i n t e r g r o w t h o f offretite i n t h e erionite phase w o u l d b e e x p e c t e d to affect t h e a d s o r p t i o n p r o p e r t i e s . T a b l e I I compares a d s o r p t i o n capacities f o r n a t u r a l a n d synthetic erionite w i t h Z e o l i t e A ( C a ) a n d synthetic faujasite ( N a ) ( 4 . 8 S i 0 / A l 0 ) . A s 2

2

3

e x p e c t e d , t h e m o r e dense erionite structure shows l o w e r c a p a c i t y ( 5 ) . T h e r e is s u b s t a n t i a l agreement

b e t w e e n n a t u r a l a n d synthetic

erionite

c a p a c i t y ; the difference shows i n a d s o r p t i o n rates ( D/r ). T h e l o w a p p a r 2

ent d i f f u s i v i t y of η-paraflîns i n erionite is s o m e w h a t a m y s t e r y since there does n o t a p p e a r t o b e that m u c h difference i n p o r e d i m e n s i o n s b e t w e e n erionite a n d zeolite A as p r e d i c t e d f r o m t h e i r structures ( 6 ) . T h e differ ence cannot b e a t t r i b u t e d t o crystallite size since t h e n a t u r a l erionite s a m p l e (laths, 0.5 μ d i a m e t e r o r less) has finer c r y s t a l l i t e size t h a n a n y of t h e synthetic materials ( 1 - 5 μ ). Table II.

Adsorption Capacities n-Hexane

Sample

Capacity"

Faujasite (Na) Zeolite A ( C a ) Natural Erionite Synthetic Erionite ( N a , K ) Synthetic Erionite (H)

1.68 0.83 0.57 0.68 0.50

n-Octane

Diffusivity

b

137 2.1 0.23 2.4 10 c

Capacity

0

Diffusivity

1.06 0.80 0.32 0.27 0.35

° M i l l i m o l e s a d s o r b a t e / g r a m zeolite (20- t o 35-mesh granules). A p p a r e n t d i f f u s i v i t y (D/r ) s e c Χ 10 (6). Desorption. b

2

- 1

3

0


6

46 2.3 0.024 5.5 5.1 c

73.

Synthetic

ROBSON E T AL.

421

Erionite

T h e difference is m o r e n o t a b l e i n η-octane a d s o r p t i o n w h i c h is s h o w n i n the last 2 c o l u m n s of T a b l e I I . Z e o l i t e A shows s u b s t a n t i a l l y t h e same c a p a c i t y a n d a d s o r p t i o n rate f o r η-octane as for n-hexane. B u t f o r e r i o n i t e , b o t h n a t u r a l a n d synthetic, η-octane

capacities,

a n d particularly the

a d s o r p t i o n rates are s u b s t a n t i a l l y r e d u c e d . H e r e the difference b e t w e e n synthetic a n d n a t u r a l erionite a d s o r p t i o n rate is q u i t e large. I t is possible that this is a n effect of r e s i d u a l K cations. H o w e v e r , s i m p l e exchange of +

Na

+

a n d K f o r H s h o w e d l i t t l e change. +

+

W e believe the more probable

e x p l a n a t i o n is t h e i n t e r g r o w t h of offretite i n t h e erionite c r y s t a l . T h e large offretite channels c o u l d g i v e m o r e r a p i d d i s t r i b u t i o n o f t h e sorbate Downloaded by PURDUE UNIV on October 25, 2016 | http://pubs.acs.org Publication Date: June 1, 1971 | doi: 10.1021/ba-1971-0102.ch073

m o l e c u l e w i t h i n the synthetic erionite c r y s t a l . Hydracracking

Tests

T h e s e materials w e r e tested as catalysts f o r t h e selective c o n v e r s i o n of n o r m a l paraffins. T h e use of 5 A zeolites as shape-selective

catalysts

w a s first d e s c r i b e d b y E n g ( 7 ) ; i t has b e e n d e v e l o p e d s u b s e q u e n t l y b y several authors.

F o r this p u r p o s e , the e x c h a n g e d zeolites w e r e i m p r e g

n a t e d w i t h 0 . 5 % P d , m a d e i n t o 14- to 35-mesh granules ( s e l f - b o n d e d ), a n d p r e r e d u c e d w i t h h y d r o g e n at 8 5 0 ° F . C /C 5

6

T h e feedstock w a s a n A r a b i a n

n a p h t h a stream, selected because of its h i g h η-paraffin

content

( o v e r 4 0 % ) . T h e n i t r o g e n content of t h e f e e d w a s less t h a n 1 p p m , s u l f u r less t h a n 10 p p m . T e s t c o n d i t i o n s w e r e 7 5 0 ° F ( e x c e p t w h e r e other w i s e n o t e d ) , 500 p s i g , 0.5 V / V / h r , a n d 2000 s t d . c u f t H / b b l .

The

2

catalyst w a s s u l f i d e d b y a d d i n g 0 . 2 5 % C S t o t h e f e e d . 2

p r o d u c t s w e r e e v a l u a t e d b y G C a n d M S analyses.

L i q u i d a n d gas

Individual

p e r i o d s w e r e 7 hours l o n g ; m u l t i p l e tests o n the same catalyst

balance charge

gave t o t a l exposures u p to 200 h o u r s .

Table III.

Hydrocracking of C5—CQ Naphtha by Zn-Exchanged Zeolites

Catalyst (Na 0 + 2

Base

K 0)/A1 0 2

Conversion, W t % n-Pentane n-Hexane Other

2

3

Natural Erionite

Synthetic Erionite

Faujasite

Zeolite A

0.24

0.11

0.33

0.20

60 79 52

62 86 15

81 98 25

93 99+ 36

T a b l e I I I compares results f r o m erionite catalysts w i t h faujasite a n d zeolite A , a l l i n t h e z i n c - e x c h a n g e d f o r m . Z i n c w a s u s e d to o b t a i n a n a c t i v e f o r m of zeolite A w h i c h is stable to these c o n d i t i o n s . E r i o n i t e is less a c t i v e t h a n faujasite f o r c o n v e r s i o n of t h e t o t a l n a p h t h a f e e d t o C 4


422


Table I V .

Hydrocracking by Different Cationic Forms of Synthetic Erionite

Catalyst Base (Na 0 + 2

K 0)/A1 0 2

2

Conversion, W t n-Pentane n-Hexane Other


Table V .

II

Zn-Erionite

3

%

H-Erionite

RE-Erionite

0.20

0.31

0.24

93 99+ 36

96 99+ 41

97 99+ 27

Effect of Temperature on Hydrocracking with R E - E r i o n Temp.,

Conversion, W t n-Pentane n-Hexane Other

°F

%

Table V I .

Ci C C i-C n-C i-C n-C Branched-Ce n-C Branched C7 MCP CH MCH Benzene 3

4

4

B

5

6

700

750

52 30 8

91 99+ 15

97 99+ 27

Feed and Product Composition, W t

Component

2

650

Feed 0.0 0.0 0.0 0.0 0.2 9.8 16.2 38.7 25.0 0.5 6.3 1.0 0.0 2.2

%

Product 0.7 3.2 36.6 1.7 6.6 7.1 1.4 34.4 0.2 0.4 4.3 0.6 0.2 2.6

a n d l i g h t e r m a t e r i a l s , b u t it is c o n s i d e r a b l y m o r e a c t i v e f o r c o n v e r t i n g n - p e n t a n e a n d n-hexane. Z e o l i t e A is s t i l l less active b u t is m o r e selective f o r c o n v e r t i n g o n l y the n o r m a l paraffin c o m p o n e n t . C o m p a r e d w i t h nat u r a l e r i o n i t e , the synthetic erionite catalyst is m o r e active f o r c o n v e r s i o n of b o t h t o t a l f e e d a n d the n - p a r a f f i n c o m p o n e n t .

It is less selective f o r

o p e r a t i n g o n l y o n the n o r m a l paraffins. E r i o n i t e c a n be u s e d i n other c a t i o n i c forms i n c l u d i n g the h y d r o g e n a n d rare e a r t h f o r m s . A s e x p e c t e d , these g i v e i m p r o v e d a c t i v i t y as s h o w n in Table IV.

T h e h y d r o g e n f o r m is t h e m o s t active b u t also the least

selective, p o s s i b l y because the test c o n d i t i o n s are too severe.

T h e rare

e a r t h e x c h a n g e d f o r m ( n a t u r a l m i x t u r e less c e r i u m ) is just as a c t i v e f o r c o n v e r t i n g n o r m a l paraffins b u t m o r e selective. A g a i n , the c o n d i t i o n s are


73.

ROBSON E T

Synthetic

AL.

423

Erionite

too severe, a n d better results c a n b e a c h i e v e d b y a c c e p t i n g less t h a n e x t i n c t i o n of t h e n-parafBns. T h i s is c o n f i r m e d b y T a b l e V , w h i c h shows the t e m p e r a t u r e effect. A t 6 5 0 ° F , n-hexane c o n v e r s i o n i s o n l y 3 0 % ; this is consistent

w i t h l o w e r a d s o r p t i o n rates o b s e r v e d f o r t h e h i g h e r n -

paraffins. A t 7 0 0 ° F a n d a b o v e , t h e greater s t a b i l i t y of n - p e n t a n e b e c o m e s the c o n t r o l l i n g factor; n-hexane is s u b s t a n t i a l l y e x t i n g u i s h e d .

Selectivity

at 7 0 0 ° F is better t h a n t h e earlier results w i t h zeolite A at 7 5 0 ° F . C o m p o s i t i o n of f e e d a n d p r o d u c t f r o m t h e rare-earth erionite catalyst at 7 0 0 ° F are g i v e n i n T a b l e V I . The

question

remains

w h y t h e other

components,

principally


b r a n c h e d paraffins, are c o n v e r t e d at a l l . S e v e r a l explanations c a n b e offered, n o n e c o m p l e t e l y satisfactory.

N o t a l l t h e p a l l a d i u m is i n s i d e t h e

z e o l i t e cages b u t m a y b e p a r t i a l l y o n e x t e r n a l surfaces a n d n o n z e o l i t e c o m p o n e n t s , a m o r p h o u s m a t e r i a l w h i c h is either t h e r e s i d u e of i n c o m plete c r y s t a l l i z a t i o n o r the p r o d u c t of zeolite d e c o m p o s i t i o n i n subsequent treatments.

Since x-ray c r y s t a l l i n i t y is u n i f o r m l y h i g h , t h e a m o r p h o u s

c o m p o n e n t s h o u l d b e q u i t e s m a l l . B r a n c h e d paraffins c a n penetrate t h e zeolite surface f a r e n o u g h to b e c r a c k e d .

H i g h t e m p e r a t u r e alters t h e

selective a d s o r p t i o n properties o f t h e zeolite, w h i c h w e r e o b s e r v e d at l o w temperature.

Offretite i n t e r g r o w t h s p r o v i d e e n o u g h surface i n larger

d i a m e t e r pores p a r t i a l l y to c o n v e r t b r a n c h e d a n d c y c l i c m o l e c u l e s .

There

is some t r u t h i n a l l o f these b u t w e p r e f e r t h e latter.

Literature Cited (1) Breck, D. W., Acara, Ν. Α., U. S. Patent 2,950,952 (1960). (2) Bennett, J. M., Gard, J. Α., Nature 1967, 214, 1005-6. (3) Deffeyes, K. S., "Molecular Sieves," Society of Chemical Industry, Lon don, 1968. (4) Deffeyes, K. S., Am. Mineralogist 1959, 44, 501-9. (5) Eberly, P. E., Jr., Am. Mineralogist 1964, 49, 30-40. (6) Eberly, P. E., Jr., Ind. Eng. Chem. Prod. Res. Develop. 1969, 8, 140-4. (7) Eng, Jackson, U. S. Patent 3,039,953 (1962). (8) Gard, J. Α., private communication. (9) Sheppard, R. Α., Gude, A. J., Am. Mineralogist 1969, 54, 875-86. (10) Staples, L. W., Gard, J. Α., Mineral. Mag. 1959, 32, 261-81. (11) Zhdanov, S. P., Izv. Akad. Nauk SSSR, Ser. Khim. Nauk 1965 (6) 950-9. RECEIVED February 10, 1970.

Discussion F . W . K i r s c h ( S u n O i l C o . , M a r c u s H o o k , P a . 19061): D i d y o u i n f e r a n y conclusions a b o u t r e a c t i o n m e c h a n i s m f r o m the n a t u r e o f the p r o d u c t distribution?


424


II

H . Robson: W e w e r e p r i m a r i l y interested i n the h y d r o c r a c k i n g of n-pentane a n d n-hexane to l o w m o l e c u l a r w e i g h t gases, p r i n c i p a l l y p r o p a n e . T h e r e w e r e m i n o r s e c o n d a r y effects s u c h as i s o m e r i z a t i o n . I. M . Keen ( B r i t i s h P e t r o l e u m C o . , L t d . , M i d d l e s e x , E n g l a n d ) : F i r s t , h o w d i d y o u i m p r e g n a t e the p a l l a d i u m hydrogénation

c o m p o n e n t onto

y o u r catalysts—i.e., w h a t salt d i d y o u use? S e c o n d l y , d i d y o u notice any differences i n the h y d r o c r a c k e d p r o d u c t d i s t r i b u t i o n f r o m C - C r

6

naphtha

u s i n g y o u r different i o n - e x c h a n g e d forms o f the erionite catalyst? H . Robson: P a l l a d i u m was d e p o s i t e d o n the z e o l i t e p o w d e r b y ex change w i t h P d ( N H ) C l Downloaded by PURDUE UNIV on October 25, 2016 | http://pubs.acs.org Publication Date: June 1, 1971 | doi: 10.1021/ba-1971-0102.ch073

8

4

2

s o l u t i o n . W e d i d not observe significant d i f

ferences i n p r o d u c t d i s t r i b u t i o n b e t w e e n c a t i o n i c f o r m s o f erionite, b u t of course w e w e r e l o o k i n g p r i m a r i l y f o r the d i s a p p e a r a n c e o f n-pentane a n d n-hexane. R. C . Hansford ( U n i o n O i l C o . of C a l i f o r n i a , B r e a , C a l i f . 9 2 6 2 1 ) : T o w h a t extent m i g h t some a m o r p h o u s s i l i c a - a l u m i n a b e responsible f o r the p o o r selectivity—i.e., are the synthetic p r o d u c t s c o m p l e t e l y c r y s t a l l i n e ? H . Robson: W e k n o w that the s y n t h e t i c erionite p r o d u c t is h i g h l y c r y s t a l l i n e f r o m the intensity of x-ray d i f f r a c t i o n peaks a n d the absence of the a m o r p h o u s " h a l o / ' U n f o r t u n a t e l y , this does not p r o v e the s a m p l e is f u l l y c r y s t a l l i n e . I f a m o r p h o u s m a t e r i a l is present, i t s h o u l d b e at a v e r y l o w level. Ν . Y . Chen ( M o b i l R e s e a r c h & D e v e l o p m e n t C o r p . , P r i n c e t o n , N . J. 08540 ) : I t m i g h t b e of interest to the a u d i e n c e , p a r t i c u l a r l y to those w h o are not f a m i l i a r w i t h t h e a p p l i c a t i o n o f zeolites i n i n d u s t r i a l c a t a l y t i c processes, to m e n t i o n that since t h e d i s c o v e r y of catalysis over shapeselective zeolite first p u b l i s h e d b y W e i s z a n d F r i l e t t e i n 1960, a c o m m e r c i a l process b a s e d o n selective h y d r o c r a c k i n g reactions s i m i l a r to that r e p o r t e d i n this p a p e r has b e e n i n o p e r a t i o n o n a large scale i n m o r e t h a n f o u r of o u r refineries since 1967. A t e c h n i c a l p a p e r d e s c r i b i n g this process, k n o w n as the S e l e c t o f o r m i n g process, was p u b l i s h e d i n 1968. H . Robson: W e h a v e no p a r t i c u l a r c o m m e n t except that p r i o r i t y of i n v e n t i o n is d e t e r m i n e d b y patents r a t h e r t h a n p u b l i c a t i o n i n journals. D . L . Peterson ( C a l i f o r n i a State C o l l e g e , H a y w a r d , C a l i f . 9 4 5 4 2 ) : D i d y o u examine the t e m p e r a t u r e d e p e n d e n c e o f selectivity a n d conver s i o n o f the Z n or H forms of either the synthetic or the n a t u r a l erionites? H . Robson: R e d u c t i o n o f r e a c t i o n t e m p e r a t u r e i m p r o v e s selectivity of Z n a n d H f o r m s of erionites, as w e l l as rare earth e x c h a n g e d f o r m s . D . A . Hickson ( C h e v r o n R e s e a r c h C o . , R i c h m o n d , C a l i f . 9 4 8 0 2 ) : C a n y o u c o m m e n t o n the s t a b i l i t y of a c t i v i t y a n d p r o d u c t s e l e c t i v i t y w i t h t i m e o n stream?


73.

ROBSON E T AL.

Synthetic

425

Erionite

H . Robson: O u r tests w e r e s h o r t - t e r m s c r e e n i n g tests; b a l a n c e p e r i o d s w e r e six h o u r s , t o t a l t i m e o n t e m p e r a t u r e u p to t w o or three days.

How

ever, w e w e r e a b l e to repeat the i n i t i a l results after this m u c h exposure. A s f a r as c a n be d e t e r m i n e d f r o m s h o r t - t e r m tests, catalyst l i f e appears satisfactory. Question: D o y o u h a v e a n y e s t i m a t i o n of the i n t e r n a l vs.

external

surface area of the erionite? H . Robson: B a s e d o n a p a r t i c l e size of a b o u t one m i c r o n o b s e r v e d i n the e l e c t r o n m i c r o g r a p h s , w e estimate a b o u t 3 m / g e x t e r n a l surface a r e a , 2


w h i c h is less t h a n 1 % of t o t a l surface area.


Synthetic Erionite and Selective Hydrocracking - Advances in

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