7/24/2019 Us 3904656 patent

1/6

U n i t e d S t a t e s v

P a t e n t 1 1 9 1

[ 1 1 1

3,904,656

B r o z

[ 4 5 ]

S e p t . 9 , 1975

[54]

PROCESS

FOR PREPARING 2 , 4 0 9 , 4 4 1 10/1946

Metzger

. . . . . . . . . . . . . . . . . . . . . . .

. . 260/637

R

MONOETHYLENE

GLYCOL

AND 2 , 4 3 0 , 4 4 3

1 1 / 1 9 4 7

P e c k e r . . . .

2 6 0 / 3 4 8 . 5 R

2, 75 6 , 24 1

7 / 1 9 5 6

C0urter.., . . . . .

. .

2 6 0 / 6 3 5

E

ETHYLENE

OXIDE 3,367,847

2 1968

Pierson . . . . . . . . . . . . . . . . 260 637R

[ 7 5 ]

I n v e n t o r ; S t e p h e n

E .

B r o z ,

Beaumont,

T e x , 3 , 4 1 8 , 3 3 8 1 2 / 1 9 6 8 G i l m a n e t

a 1 .

2 6 0 / 3 4 8 . 5

R

_ _ _ 3,597,452 8/1971 Laemmle

et

a1.

. . . . . . . .

260/348.5

[ 7 3 ] A s s l g n e e l PPG n d u s t l l e s , Inc Pmsburgh, P a - 3 , 7 3 2 , 3 2 0

5 / 1 9 7 3

Ford . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 6 0 / 6 3 7

R

[ 2 2 ]

F i l e d :

F e b .

1 3 ,

1973

[ 2 1 ]

A p p l _

N o _ : 3 32 0 5 6

P r i m a r y

Examiner-Joseph

E .

E v a n s

A t t o r n e y ,

Agent, or

F i r m - l rw i n M . S t e i n

[ 5 2 ] US. C L . . .

2 6 0 / 3 4 8 . 5 R ;

2 6 0 / 6 3 5 E ; 2 6 0 / 6 3 7

R

[51]

I n t .

GL2

. . . . . . . . . . . . . . .

. .

C07C 1/20; C 0 7D

3 0 1 / 3 2 [57] ABSTRACT

[ 5 8 ]

F i e l d o f Search . . .

. . 260/635 E , 3 4 8 . 5

I R ,

6 3 7

R An

mproved

p r o c e s s

f o r p r e p a r i n g ?ber

g r a d e m o n o_

[ 5 6 ]

R e f e r e n c e s C i t e d e t h y l e n e

g l y c o l i s

p r o v i d e d

w h i c h o b v i a t e s t h e need

f o r

s e w e r i n g

l a r g e

amounts

o f

w a t e r .

UNITED STATES PATENTS

2 , 1 2 5 , 3 3 3

8/1938

C a n e r

. . . . . . . . . . . . . . . . . . . . . . . . . 260/348.5 R 3

Claims,

1

Drawing Figure

E.O.REACTOR

ABSORBER

STRIPPER

REABSORBER

E.O.REFINING

E.O,PURIFY|NG OLUMNS

s t e p

a .

s t e p b ) s r e p c )

( s t e p

d ) s r e p

h )

Rec

c l e E 1 h y | e n e

5 . 0 . 1 5 . 0 . 5 . 0 . 0 0 2 5 . 0 .

H 2 0

H 2 0 r

5 0 / 1 1 2 6

A I R 1

ETHYLENE

E . O . / H 2 0 P 2 ) ? 5 . 0 .

FURGE ( I N O R G A N I C S A L T S

Am

-V-ABSORBERS)E.G./Hg0

STEAM

(CONDENSED)

G

was

H o

MEG

0 5

a F [ - >

E g g / { 3 2 5 R z x r l l ? E

( O P T I O N A L 5 0 / 1 4 2 0 H2OEGASSER ACTIVATED T EG

CARBON

H20

MEG DEG TEG

DEG TEG

TEG

ETHYLENE GLYCOL DRYING

DISTILLATION

TR A I N

REACTOR

EVAPORATION

COLUMN

1 1 4 5 s 05s TEG

s r e p

e ) ( s r e p f )

@-srep g-__-

7/24/2019 Us 3904656 patent

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7/24/2019 Us 3904656 patent

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3 , 9 0 4 , 6 5 6

l

PROCESS

FOR'PREPARING

M O N O E T H Y L E N E

GLYCOL AND ETHYLENE

OXIDE

DESCRIPTION

OF THE INVENTION

E t h y l e n e g l y c o l s ( m o n o e t h y l e n e g l y c o l , d i e t h y l e n e

g l y c o l and t r i e t h y l e n e g l y c o l )

a r e

p r e p a r e d

c o m m e r

c i a l l y

b y s e v e r a l

m e t h o d s . O ne o f t h e s e methods

in

v o l v e s a t w o- s t a g e r e a c t i o n

s y s t e m ,

t h e ? r s t s t a g e

o f

w h i c h r e q u i r e s

t h e

d i r e c t

o x i d a t i o n o f e t h y l e n e

w i t h

a i r

o r

elemental oxygen

over a

s u i t a b l e c a t a l y s t , t y p i c a l l y

a

s i l v e r - c o n t a i n i n g c a t a l y s t ,

a t e l e v a t e d

t e m p e r a t u r e

( 1 0 0 C . t o 5 0 0 C . i s t y p i c a l ) and a t s u p e r a t m o s p h e r i c

p r e s s u r e ( 2 t o 2 5

a t m o s p h e r e s ) .

E t h y l e n e

o x i d e produced i n t h e s e r e a c t o r s , which

m a y

be

? x e d o r

?uid

bed r e a c t o r s , a s

t y p i ? e d

by US.

P a t . No. 2 , 1 2 5 , 3 3 3 and US.

P a t .

No. 2 , 4 3 0 , 4 4 3 , i s r e

m o v e d

from t h e r e a c t o r s i n

a

g a s

stream

a n d i s

passed

i n t o

an

e t h y l e n e

o x i d e a b s o r b e r

where

t h e

g a s stream

i s contacted

w i t h water

t o

absorb

t h e e t h y l e n e oxide

c o n t e n t

t h e r e o f .

The

g a s e s (which

s t i l l

c o n t a i n

appre

c i a b l e q u a n t i t i e s o f

e t h y l e n e )

a r e t h e n

r e c y c l e d

t o t h e

e t h y l e n e o x i d e r e a c t o r w h i l e t h e e t h y l e n e o x i d e con~

t a i n i n g w a t e r i n

t h e a b s o r b e r i s p a s s e d t o a s t r i p p e r ,

e . g . , s t r i p p i n g column.

I n t h e

s t r i p p e r ,

steam o r h o t

water

i s

introduced

a n d

contacted

u s u a l l y

countercur~

r e n t t o t h e e t h y l e n e oxide f e d t h e r e t o t o r e m o v e e t h y l

ene o x i d e

product

o v e r h e a d . The water d i s c h a r g e d

from t h e s t r i p p e r

i s

r e c i r c u l a t e d t o t h e absorber

f o r

use

i n a b s o r b i n g

e t h y l e n e

o x i d e t h e r e i n .

I n o t h e r s y s t e m s a steam heated

r e b o i l e r

i s employed

t o h e a t water i n t h e bottom of t h e s t r i p p i n g c o lu m n a n d

b o i l i t . T h i s g e n e r a t e s s t e a m i n t e r n a l l y

i n

t h e

s t r i p p i n g

column.

While

t h i s

e l i m i n a t e s

a water

b u i l d - u p

problem

g l y c o l s s t i l l accumulate i n

t h e column

and must be

p u r g e d t o t h e e v a p o r a t i o n a n d / o r r e c o v e r y s y s t e m s o f

t h e

g l y c o l

p r o d u c i n g u n i t .

Because water i s i n t r o d u c e d

i n t o

t h e

s t r i p p e r

and t h e

aqueous

s t r i p p e r

bottoms

a r e r e c y c l e d t o

t h e a b s o r b e r

t o

provi de

a closed system, a

p ur g e

o r

bleed

stream i s

required

to r e m o v e the

excess water

which

accumu

l a t e s .

T h i s

purge

stream c o m m o nly

c a l l e d

t h e

l e a n

c y c l e

w a t e r s t r e a m

g e n e r a l l y

c o n t a i n s a p p r e c i a b l e

q u a n t i t i e s o f e t h y l e n e g l y c o l i n i t ,

e . g . ,

l

t o 3 p e r c e n t

b y volume and t h i s g l y c o l

i s

u s u a l l y o f s u c h v a l u e

t h a t

i t

cannot

be d i s c a r d e d .

F u r t h e r , s i n c e t h e

purge stream

c o n t a i n s e t h y l e n e g l y c o l ,

i t c a n n o t

b e e a s i l y d i s p o s e d o f

due t o t h e f a c t t h a t e t h y l e n e g l y c o l h a s a d e l e t e r i o u s e f

f e c t o n t h e

t o t a l

oxygen demand

f

bodies

of

water i n

w h i c h t h i s

m a t e r i a l

m i g h t b e

d i s c h a r g e d .

S i m i l a r l y ,

where

h e a t e d

s t r i p p i n g v e s s e l s a r e u s e d , g l y c o l b u i l d u p

in t h e v e s s e l s r e q u i r e a b l e e d

o f

w a t e r - g l y c o l from

t h e

s y s t e m .

The o v e r h e a d

f r o m

t h e s t r i p p e r c o m p r i s i n g e t h y l e n e

o x i d e i s p a s s e d

t o

an

e t h y l e n e

o x i d e reabsorber

a n d

t h e

e t h y l e n e oxide absorbed

i n

w a t e r .

F r o m

t h e r e a b s o r b e r ,

a p o r t i on of t h e aqueous e t h y l e n e oxide mixture i s

p a s s e d t o a

g l y c o l

r e a c t o r t o

m a ke

e t h y l e n e

g l y c o l s

a n d

a

p o r t i o n i s p a s s e d t o a r e ? n i n g

v e s s e l

t o produce

p u r i

? e d e t h y l e n e

o x i d e .

The e t h y l e n e

g l y c o l s p r o d u c e d i n

t h e g l y c o l

r e a c t o r

a r e ? r s t

passed

t o

an

e v a p o r a t o r

wherein water vapo r

i s

r e m ov e d

and t h e

vapor

i s

then

condensed and r e c y c l e d t o t h e r e a b s o r b e r .

The

g l y c o l s

product

i s

taken

from

t h e evaporator

a s

bottoms,

f u r

t h e r d r i e d and p a s s e d

t h r o u g h a

d i s t i l l a t i o n

t r a i n

wherein monoethylene

g l y c o l

can

be

recovered

i n

a

? r s t d i s t i l l a t i o n v e s s e l

a s

overhead.

T h e bottoms i s then

5

1 0

20

25

3 0

35

4 0

45

55

65

2

p a s s e d t o a second d i s t i l l a t i o n v e s s e l wherein d i e t h y l

ene g l y c o l i s

recovered

a s

overhead,

a n d

t h e bottoms

p a s s e d t o a t h i r d d i s t i l l a t i o n v e s s e l wherein t r i e t h y l e n e

g l y c o l

i s r e c o v e r e d

a s o v e r h e a d . A l t e r n a t i v e l y , t h e e t h

y l e n e g l y c o l s

can be

s e p a r a t e d

i n

a

f r a c t i o n a t i o n

c o l

umn.

The

p o r t i o n

o f

e t h y l e n e

o x i d e

w h i c h

i s

p a s s e d

f r o m

t h e

r e a b s o r b e r

t o p r o d u c e

p u r i ? e d

e t h y l e n e

o x i d e i s

? r s t

p a s s e d

t o

a r e ? n i n g column

w h e r e i n

t h e e t h y l e n e

oxide i s recovered a s

overhead

a n d t h e aqueous

bot

t o m s

c o n t a i n i n g u l t r a - v i o l e t

l i g h t

a b s o r b e r s i s r e c y c l e d

t o t h e re a b s o r b e r . The e t h y l e n e o x i d e overhead from

t h e

re?ning

column can t h e n be

f u r t h e r

puri?ed i n

a

subsequent

v e s s e l t o remove carbon d i o x i d e overhead

and t h e e t h y l e n e

o x i d e

bottoms p a s s e d t o a t h i r d

d i s t i l

l a t i o n v e s s e l w h e r e i n t h e p u r i ? e d e t h y l e n e o x i d e p r o d

uct i s

recovered a s overhead.

I t would be

d e s i r a b l e i f

t h e aqueous

bottoms

could be

r e c y c l e d

from

t h e e t h y l e n e o x i d e r e ? n i n g

v e s s e l to

t h e

r e a b s o r b e r

t o

p r o v i d e

m a ke u p

w a t e r

and

o b v i a t e

t h e

need

f o r sewering

s a i d

b o t t o m s . The u s e o f

t h i s

bottoms

i n t h e p r e p a r a t i o n o f e t h y l e n e g l y c o l s , h o w e v e r , h a s

c a u s e d t h e

monoethylene

g l y c o l p r o d u c t

t o

b e u n s u i t

a b l e f o r u s e a s ?ber

grade

m a t e r i a l . M o r e

p a r t i c u l a r l y ,

i t

h a s

been found t h a t

t h e

aqueous

bottoms

i n

t h e re?n

i n g

column

c o n t a i n s u l t r a - v i o l e t l i g h t a b s o r b e r s which

c o n t a m i n a t e m o n o e t h y l e n e g l y c o l p r o d u c e d

t h e r e f r o m .

I t would

a l s o

be

d e s i r a b l e

i f t h e purge stream could

be r e c y c l e d t o

t h e

r e a b s o r b e r , b u t

t h e

purge stream

c o n t a i n s

u l t r a - v i o l e t

a b s o r b e r s

which

contaminate

m o n o e t h y l e n e g l y c o l p r o d u c e d

f r o m s a i d

e t h y l e n e

o x

i d e . I t would a l s o be d e s i r a b l e i f t h e purge stream could

be

r e c y c l e d t o

an

e t h y l e n e g l y c o l w a t e r e v a p o r a t o r t o

b e u s e d

a s r e f lu x t o

produce

p u r i ? e d

e t h y l e n e

g l y c o l ,

but

the

purge stream

contains

both s a l t s which

cause

s c a l i n g

i n t h e

e v a p o r a t o r and u l t r a - v i o l e t a b s o r b e r s

w h i c h

c o n t a m i n a t e

t h e m o n o e t h y l e n e g l y c o l p r o d u c t .

I t has now

been

discovered t h a t the purge stream

from

t h e e t h y l e n e o x i d e s t r i p p e r

can

be

upgraded

t o

r e n d e r i t

s u i t a b l e

f o r r e c y c l i n g

t o

t h e

e t h y l e n e

o x i d e

r e a b s o r b e r

and e t h y l e n e g l y c o l e v a p o r a t o r , when t h e

purge stream i s

deionized

by treatment

with i o n ex

change m a t e r i a l s t o remove metal s a l t s , t h e

purge

stream

passed

t o

a

d e g a s s i f i e r

t o

r e m o v e

c arbon

d i o x

i d e a n d

other

v o l a t i l e s a n d t h e

purge stream t r e a t e d

with

a c t i v a t e d carbon

t o

remove u l t r a - v i o l e t l i g h t ab

s o r b e r s .

I t has

f u r t h e r

been d i s c o v e r e d t h a t t h e aqueous bot

toms from t h e e t h y l e n e

oxide

re?ning v e s s e l can be

r e

c y c l e d t o t h e

e t h y l e n e

o x i d e r e a b s o r b e r ,

and a

?ber

g r a d e m o n o e t h y l e n e

g l y c o l

p r o d u c t r e c o v e r e d . I t i s

o n l y r e q u i r e d

t h a t

t h e e t h y l e n e o x i de p a s s e d f r o m t h e

r e a b s o r b e r

t o

t h e e t h y l e n e o x i d e r e ? n i n g

v e s s e l

b e con

t r o l l e d

t o provide

a

f e e d t o t h e g l y c o l r e a c t o r

having an

a m o u n t o f

aqueous bottoms

from t h e e t h y l e n e o x i d e

re?ning

v e s s e l i n s u f ? c i e n t t o c ontaminate the mono

e t h y l e n e

g l y c o l p r o d u c t and r e n d e r i t

u n s u i t a b l e

f o r

u s e

a s a

?ber

grade

p r o d u c t .

DETAILED DESCRIPTION OFTHE INVENTION

M o r e

p a r t i c u l a r l y ,

t h e i n v e n t i o n

a s

b r o a d l y

de?ned

c o m p r i s e s : I n t h e m a n u f a c t u r e o f

e t h y l e n e

g l y c o l s b y

t h e

s t e p s o f :

a . reacting

a i r

or o x y g e n a n d

ethylene

i n the presenc e

o f a c a t a l y s t

a t

e l e v a t e d t e m p e r a t u r e s t o produce

e t h y l

ene

o x i d e ;

b .

a b s o r b i n g

t h e

e t h y l e n e o x i d e o f s t e p ( a ) i n

w a t e r ;

7/24/2019 Us 3904656 patent

4/6

3 , 9 0 4 , 6 5 6

3

c . s t r i p p i n g

t h e

e t h y l e n e

o x i d e from t h e

water o f s t e p

( b )

by

c o n t a c t w i t h s t e a m ,

a n d

r e c o v e r i n g

and con

densing steam

t o

water

a n d r e c y c l i n g r e s u l t a n t

water

t o

s t e p b ) ;

d .

r e a b s o r b i n g

in w a t e r t h e

e t h y l e n e o x i d e r e c o v e r e d

f r o m s t e p

c ) ;

e . r e a c t i n g a p o r t i o n of

t h e e t h y l e n e oxide

a n d water

o f s t e p ( d )

t o p r o d u c e e t h y l e n e g l y c o l s ;

f . e v a p o r a t i n g

w a t e r o f s t e p ( e ) and

c o n d e n s i n g

and

r e c y c l i n g

w a t e r

t o s t e p ( d ) ;

g .

d i s t i l l i n g e t h y l e n e

g l y c o l s

o f

s t e p

( e )

t o s e p a r a t e

m o n o e t h y l e n e g l y c o l

t h e r e f r o m ;

a n d

h . d i s t i l l i n g a p o r t i o n o f t h e

e t h y l e n e

o x i d e and water

o f s t e p ( d ) t o s e p a r a t e t he

e t h y l e n e

o x i d e and r e c y c l i n g

r e s u l t a n t

water

t o

s t e p

( d ) ;

t h e

improvement which c o m p r i s e s

removing

a p o r

t i o n of t h e water condensed i n

s t e p

( c ) , i n a n a m o u n t

s u f f i c i e n t

t o

maintain a water balance

i n

s a i d absorbing

and s t r i p p i n g s t e p s ( b ) and ( c ) , t r e a t i n g

removed

w a t e r

w i t h i o n exchange m a t e r i a l s t o

r e m ov e s a l t s

contained

t h e r e i n , degassing r e m o v e d water t o r e m o v e

carbon

d i

o x i d e and v o l a t i l e s t h e r e f r o m ,

and t r e a t i n g

removed

water

with

activated

c a r b o n t o r e m o v e u l t r a - v i o l e t a b

s o r b e r s a n d r e c y c l i n g t h e r e s u l t a n t water t o s t e p s ( d ) o r

( f )

or both a s

required

t o

provide makeup

water or r e

? u x me d i u m; and

t h e f u r t h e r improvement

which

com

p r i s e s r e g u l a t i n g t h e amount o f e t h y l e n e o x i d e

and

w a t e r p a s s e d from

s t e p ( d ) t o s t e p ( h )

s u c h

t h a t t h e

a m o u n t

of water

recycled

t o

s t e p ( d )

i s not

so g r e a t

a s

t o introduce an a m o u n t of u l t r a - v i o l e t l i g h t absorbers

s u f f i c i e n t t o

r e n d e r t h e monoethylene g l y c o l

o f s t e p

( g )

u n s u i t a b l e f o r use

a s

?ber grade m a t e r i a l .

I n

order

t o s e t f o r t h

c l e a r l y

t h e n a t u r e o f t h e i n v e n

t i o n ,

t h e

e n t i r e

e t h y l e n e o x i d e - g l y c o l p r o c e s s

i s

d e

s c r i b e d i n r e l a t i o n t o t h e improved p r o c e s s o f t h e

in

v e n t i o n i n d e t a i l . T y p i c a l l y , i r o r oxygen and e t h y l e n e

are fed to a

reactor

?lled with a s i l v e r c a t a l y s t . The

th

y l e n e and oxygen r e a c t

i n t h e p r e s e n c e o f

t h e

c a t a l y s t

a t temperature t y p i c a l l y i n

t h e r a n g e o f

from 1 0 0 C . t o

5 0 0 C . a n d

p r e f e r a b l y

i n

t h e

r a n g e o f 2 0 0 C . t o 3 6 0 C .

The e t h y l e n e

o x i d e

vapor produced overhead

i s

t h e n

passed t o

an

absorber

where

i t

i s countercurrently con

tacted with water a t a

temperature of

about 85F. A t

a n

absorber bottoms temperature o f about 1 1 8 F . and t h e

t o p

p r e s s u r e

o f a b o o u t 270 p s i . a b s o l u t e ,

e t h y l e n e i s

recovered a s

a

g a s a n d

recycled

t o

the ethylene oxide

r e a c t o r .

The

a b s o r b e r

b o t t o m s

c o n t a i n i n g

p r i n c i p a l l y

e t h y l e n e o x i d e i s r a i s e d t o a temperature of about

2 1 2 F . by

a s e r i e s

o f heat exchangers and passed

t o a

s t r i p p e r ,

p r e f e r a b l y a t a p o i n t

near

the

t o p .

S team a t a

t e m p e r a t u r e

o f

a b o u t

5 0 0 F . i s

p a s s e d i n t o t h e s t r i p p e r

p r e f e r a b l y

a t

a p o i n t

near t h e

bottom

and

t h e s t r i p p e r

i s

operated a t

a top p r e s s u r e and temperature of about

20 psi.

a b s o l u t e

a n d

2 0 9 F .

t o

r e c o v e r

e t h y l e n e

o x i d e

o v e r h e a d . The

e t h y l e n e

o x i d e i s t h e n p a s s e d th r o u g h

a

s e r i e s of heat exchangers

t o

reduce t h e temperature t o

about 9 6 F . where i t

i s

f e d

i n t o

a reabsorber p r e f e r a b l y

a t a point near the

bottom.

The

q u e o u s

bottoms f r o m

t h e s t r i p p e r i s

p a s s e d

t h r o u g h a s e r i e s o f

h e a t

exchang

e r s t o

reduce

the

temperature

t o

about

8 5 F .

a n d

then

r e c y c l e d t o t h e

a b s o r b e r ,

p r e f e r a b l y

a t a

p o i n t

near t h e

t o p .

A

o r t i o n o f t h e aqueo us bottoms from t h e

s t r i p

p e r , however, i s purged o r

b l e d

from t h e stream

i n

order

t o r e m o v e i n o r g a n i c s a l t s

a n d

u l t r a - v i o l e t

absorb

e r s

a n d maintain a water balance

i n

t h e absorber s t r i p

per system. This purge

stream i s

passed

t o a n

ion ex

1 0

25

35

4 0

45

55

65

4

change b e d , t o

a

degasser a n d t o a'bed of a c t i v a t e d c a r

bon.

The d e i o n i z a t i o n o c c u r r i n g i n t h e i o n exchange bed

c a n

be

accomplished

by the use of a n u m b e r of com

monly employed o r g a n i c

i o n

e x c h a n g e

r e s i n s

s u c h a s

t h e s u l f o n i c a c i d c a t i o n t y p e a n d t h e weak b a s e a n i o n

t y p e .

I n

a d d i t i o n ,

i n o r g a n i c

e x c h a n g e r s

such a s

t h e n a t

u r a l

and

s y n t h e t i c

a l u m i n o

s i l i c a t e

c a t i o n

e x c h a n g e r

g e l s c a n

be employed.

P r e f e r r e d ,

however, a r e t h e o r

g a n i c h i g h t e m p e r a t u r e t y p e s , e . g . , e f f e c t i v e a t 8 5 F .

such a s

t h e

s t y r e n e d i v i n y l

benzene

c a t i o n r e s i n s h a v i n g

a s u l f o n i c a c i d f u n c t i o n a l i t y , and t h e weak b a s e a n i o n

r e s i n s such

a s

s t y r e n e d i v i n y l benzene

having a

q u a r t e r

nary ammonium

u n c t i o n a l i t y .

The

most

p r e f e r r e d

r e s

i n s of t h e

a f o r e s a i d

s t y r e n e

d i v i n y l

benzene t y p e s a r e a

c a t i o n e x c h a n g e r e s i n d e s i g n a t e d A m b e r l y s t A 1 5

a n d

a n a n i o n e x c h a n g e r e s i n d e s i g n a t e d A m b e r l y s t A21,

b o t h s o l d b y Rohm

aas Company.

The d e i o n i z a t i o n

can

be accomp lished by

u s e

of t h e

conventional

r e v e r s e

a n d m i x e d

m o n o - b e d

methods.

The

c o n v e n t i o n a l

method i s

p r e f e r r e d ,

h o w e v e r ,

i n

which t h e purge stream i s

? r s t

passed through

a

c a t i

onic

exchanger

i n t h e

hydrogen form

i n

order t o r e

m o v e t h e

c a t i o n s

and r e p l a c i n g

them b y

hydrogen

i o n s .

Then

t h e

p u r g e

s t r e a m

i s p r e f e r a b l y

d e g a s s e d

b y h e a t

i n g under

reduced p r e s s u r e

t o remove

carbon d i o x i d e

a n d v o l a t i l e s . F r o m

t h e

d e g a s s e r ,

t h e purge stream

i s

p r e f e r a b l y

p a s s e d t h r o u g h a n a n i o n e x c h a n g e r e s i n i n

t h e h y d r o x y l f o r m . The

r e s u l t a n t

d e g a s s e d and d e i o n

i z e d aqueous purge stream i s t h e n p r e f e r a b l y f e d

through a bed

of a c t i v a t e d

carbon

t o r e m o v e the

u l t r a

v i o l e t

a b s o r b e r s ,

and t h e n

r e c y c l e d e i t h e r

t o

t h e

r e a b

s o r b e r ,

t o t h e e t h y l e n e g l y c o l e v a p o r a t o r , or

b o t h .

C o n t i n u i n g w i t h t h e

p r o c e s s ,

t h e e t h y l e n e o x i d e from

t h e

s t r i p p e r i s

passed t o

a reabsorber

where

water i s

added, p r e f e r a b l y a t

a

p o i n t near

t h e

t o p , countercur

rent t o

the ethylene oxid e a d d e d ne ar the

bottom,

a t a

t o p

t e m p e r a t u r e

and p r e s s u r e o f about 9 8 F . a n d 1 5

p s i .

a b s o l u t e .

The r e a b s o r b e r b o t t o m s c o m p r i s i n g e t h

y l e n e o x i d e and water i s

then f e d

i n

p a r t t o an

e t h y l e n e

g l y c o l

r e a c t o r

and i n p a r t t o an e t h y l e n e

o x i d e

re?ning

c o l u m n , t h e amounts d e p e n d i n g upon t h e p r o d u c t d i s

t r i b u t i o n

d e s i r e d . I n

t h e g l y c o l

r e a c t o r ,

t h e

e t h y l e n e

oxide

a n d water

i s reacted a t a

temperature between

about 240 a n d

310F. or a n

average

temperature of

about 2 7 5 F . ,

and

p r e s s u r e o f about 1 3 5 p s i .

a b s o l u t e .

The

r e s u l t a n t

m i x t u r e v c o m p r i s i n g e t h y l e n e

g l y c o l s

i n

water

i s then passed

t o

a m u l t i ~ e f f e c t evaporator

a n d

the

steam rec overed overhead t o

be c o n d e n s ed a n d

r e

cycled t o t h e

reabsorber p r e f e r a b l y

a t a p o i n t

near

t h e

t o p . The

e t h y l e n e

g l y c o l b o t t o m s

from

t h e m u l t i - e f f e c t

e v a p o r a t o r

i s t h e n

p r e f e r a b l y

p a s s e d

t o a d r y i n g column

wherein a t a temperature of about

1 5 0 F .

a n d

p r e s s u r e

of 20 0

m i l l i m e t e r s o f mercury, t h e remaining water i s

r e m o v e d .

The

e t h y l e n e

g l y c o l s

b o t t o m s f r o m

t h e

d r y i n g

c o l u m n

i s

then

fed

i n t o a f r a c t i o n a t i o n c o l u m n

or

d i s t i l

l a t i o n t r a i n i n which

a t a

temperature of about 1 9 6 F .

a n d p r e s s u r e of 1 0

m i l l i m e t e r s

mercury a t

t h e

top of

t h e

c o l u m n , m o n o e t h y l e n e g l y c o l p r o d u c t

i s r e c o v e r e d . I f

a

f r a c t i o n a t i o n c o l u m n

i s not employed, t h e bottoms

c o m p r i s i n g

d i e t h y l e n e

g l y c o l

a n d

t r i e t h y l e n e g l y c o l

i s

then f e d t o a second

c olumn

wherein t h e d i e t h y l e n e

g l y c o l

i s r e c o v e r e d

a s o v e r h e a d , a n d t h e bottoms i s

f e d

t o

a

t h i r d c olumn

wherein

t r i e t h y l e n e g l y c o l i s

recov

e r e d as overhead.

The

p o r t i o n of e t h y l e n e g l y c o l

i n water which was

n o t

p a s s e d

from t h e r e a b s o r b e r

t o

t h e g l y c o l r e a c t o r , i s

7/24/2019 Us 3904656 patent

5/6

3 , 9 0 4 , 6 5 6

5

p a s s e d t o

an

e t h y l e n e o x i d e r e ? n i n g column wherein

a t

a

t o p p r e s s u r e o f about 4 4 6 . s . i . , a b s o l u t e and temper

a t u r e

o f about

1

1 0 F , t h e

e t h y l e n e

o x i d e

i s

recovered

a s overhead.

T h e ethylene oxi de

i s then

passed

t o a s e

r i e s o f h e a t e x c h a n g e r s t o condense t h e v a p o r s t o

l i q u i d

a n d

s u b s e q u e n t l y

p a s s e d t o

a

s e c o n d c o l u m n ,

p r e f e r a

b l y a t a p o i n t near t h e

bottom,

wherein carbon d i o x i d e

i s recovered overhead a t

a

top temperature a n d

p r e s

s u r e o f about 1 2 2 F . and

58

p . s . i . a b s o l u t e . The b o t

toms

f r om

t h e

second

c ol u m n i s

then

fed t o a t h i r d c o l

u m n and t h e

p u r i ? e d

e t h y l e n e o x i d e p r o d u c t r e c o v e r e d

overhead a t

a top temperature a n d p r e s s u r e of

about

1 1 0 F .

and 46

p . s . i .

a b s o l u t e .

The

bottoms from t h e

e t h y l e n e o x i d e r e ? n i n g column c o m p r i s i n g w a t e r

and

u l t r a - v i o l e t

a b s o r b e r s

i s r e c y c l e d

t o

t h e r e a b s o r b e r

p r e f e r a b l y a t a

p o i n t

near

t h e

t o p

t o absorb

e t h y l e n e

o x i d e

e n t e r i n g c o u n t e r c u r r e n t l y .

I t h a s been found t h a t i n a d d i t i o n

t o

t h e d e i o n i z a t i o n ,

d e g a s s i n g , a n d a c t i v a t e d c a r b o n

t r e a t m e n t

o f

t h e

e t h y l

ene o x i d e

s t r i p p e r

purge

s t r e a m , i t i s n e c e s s a r y t h a t t h e

a m o u n t

of

e t h y l e n e oxide

and

water

bottoms from

t h e

r e a b s o r b e r , which s

p a s s e d

t o t h e e t h y l e n e o x i d e re?n

i n g column, be

l i m i t e d

t o an a m o u n t such

t h a t

the

a q u e o u s

b o t t o m s , r e c y c l e d

from t h e r e ? n i n g

column

t o

t h e reabsorber, i s not

so great a s t o

be

carried

over i n t o

t h e

g l y c o l r e a c t o r and s u b s e q u e n t l y i n t o t h e monoethy

l e n e g l y c o l p r o d u c t .

The amount o f e t h y l e n e o x i d e

and

w a t e r

bottoms

p a s s e d

from

t h e r e a b s o r b e r t o t h e e t h y l

e n e o x i d e r e f i n i n g c o l u m n , w i t h o u t s a c r i ? c i n g th e q u a l

i t y o f t h e m o n o e t h y l e n e g l y c o l p r o d u c t , w i l l

d e p e n d

i n

p a r t upon t h e e f ? c i e n c y

o f

t h e s y s t e m , i n c l u d i n g th e

i o n

exchange s y s t e m and t h e a c t i v a t e d carbon b e d . I t h a s

b e e n f o u n d , h o w e v e r , t h a t

t h e

p r e s e n t s t a n d a r d o f

?ber

g r a d e

monoethylene

g l y c o l

c a n b e

p r o d u c e d ,

when

t h e

a m o u nt o f e t h y l e n e o x i d e i n

water

p a s s e d from

t h e

r e a b s o r b e r t o

t h e

e t h y l e n e o x i d e

r e ? n i n g

column

i s

c o n t r o l l e d ,

such

t h a t t h e aqueous

bottoms

which a r e

r e c y c l e d t o t h e

r e a b s o r b e r

a r e s u f ? c i e n t l y l o w ,

such

t h a t

t h e v ol ume r a t i o of t h i s aqueous bottoms stream t o

t h e e t h y l e n e o x i d e

f e e d stream

t o

t h e g l y c o l r e a c t o r

i s

n o more than about 6 a n d

preferably n o

more than

about

5 . 3 .

According

t o

t h e a f o r e d e s c r i b e d p r o c e s s , i t i s not

n e c e s s a r y t o

sewer

l a r g e amounts

of

w a t e r c o n t a i n i n g

p r o d u c t s a n d t h e monoethylene g l y c o l produced h a s

a

m i n i m u m

t r a n s m i t t a n c e of 70 percent

a t

a

wave-length

of 2 2 0 nanometers, a minimum

f

88 percent transmit

tance a t

a

wave-length of

2 5 0

nanome t e rs,

a minimum

of

95

percent t r a n s m i t t a n c e

a t

a

wavelength of

2 7 5

nanometers,

a n d

1 00

transmittance a t a wavelength of

3 5 0 nanometers,

u s i n g d i s t i l l e d

water

a s a r e f e r e n c e l i q

u i d

i n a B e c k m a n M o d el DU 4 0 0 Spectrophotometer.

These p e r c e n t t r a n s m i t t a n c e a r e t h e p r e s e n t s p e c i ? c a

t i o n s

f o r ? b e r g r a d e monoethylene g l y c o l . The f o l l o w

i n g example i l l u s t r a t e s a p r e f e r r e d embodiment o f t h e

process of

t h e i n v e n t i o n .

EX MPLE

A

u r g e

s t r e a m , from an

e t h y l e n e

o x i d e p l a n t

s t r i p

p e r ,

c o n t a i n i n g e t h y l e n e

o x i d e , w a t e r , i n o r g a n i c

s a l t s

a n d

u l t r a - v i o l e t

a b s o r b e r s ,

w h i c h

a v e r a g e d

30-35

g a l ~

l o n s

p e r

minute i n volume f l o w , was p a s s e d i n t o t h e

top

of a c a t i o n i c exchange r e s i n bed having a volume of 6 5

c u b i c

f e e t and

i n

which t h e c a t i o n i c exchange r e s i n was 6

a s t y r e n e d i v i n y l benzene r e s i n having a

s u l f o n i c

a c i d

f u n c t i o n a l i t y .

( A m b e r l y s t

A 1 5 ,

Rohm a a s ) The

purge stream was

then

withdrawn f r o m the cation

ex

1 5

25

35

45

55

6 0

6

change

r e s i n

b e d . and p a s s e d t o

a d e g a s s e r

a p p r o x i

m a t e l y

2 0 f e e t

t a l l h a v i n g

adiameter

o f 20-42 i n c h e s

packed

w i t h i n t e r l o c k i n g

c e r a m i c .

T h e d e g a s s e r

w a s

operated a t a

temperature

of about

8 5 F .

a t 2 0 0 mm

H

p r e s s u r e .

When

h e carbon d i o x i d e and

o t h e r v o l a t i l e s

w e r e r e m o v e d ,

the

bottoms

were

fed i n t o

a n

an i on ex

change r e s i n bed h a v i n g

a

volume o f 29 c u b i c f e e 1

wherein

t h e

anion

exchange r e s i n

was a s t y r e ne d i v i n y l

benzene r e s i n

h a v i n g a

q u a r t e r n a r y a m m o n i u m f u n c

t i o n a l i t y . ( A m b e r l y s t A 2 1 , Rohm a a s ) The r e s u l

t a n t stream was then passed from

t h e

anion

r e s i n

bed

i n t o t h e top of

a

carbon bed

contained i n a 6

f o o t

d i a m

e t e r pressure v e s s e l wherein the bed was packed t o

a

d e p t h o f 4

f e e t

w i t h a

P i t t s b u r g h a c t i v a t e d

c a r b o n ,

t y p e

C a l , 1 2 t o

4 0

m e s h ,

m a n u f a c t u r e d

b y

C a l g o n C o r p o r a

t i o n .

The v e s s e l was 8 f e e t i n h e i g h t and t h e carbon bed

was placed

o n

a screen

about 1 foot f r o m the

bot t o m

of the

v e s s e l .

T h e

v e s s e l was maintained

a t a n

i n t e r n a l

p r e s s u r e

o f 1 2 5

p . s . i . g .

The water recovered a f t e r p a s

s a g e

through t h e

carbon

bed

was r e c y c l e d i n p a r t t o

t h e

ethylene oxide reabsorber

a n d

t o

s e r v e a s

re?ux

i n

t h e

e t h y l e n e

g l y c o l

e v a p o r a t o r .

E t h y l e n e o x i d e and w a t e r

bottoms

from a p l a n t e th y l

e n e

oxide

reabsorber

were

passed i n

part t o

a g l y c o l

r e

a c t o r and i n p a r t t o an e t h y l e n e

o x i d e

r e ? n i n g

column,

under t h e c o n d i t i o n s p r e v i o u s l y d e s c r i b e d . The

a m o u n t

o f e t h y l e n e o x i d e

a n d

water bottoms charged

t o t h e

r e

?ning

c olumn was c o n t r o l l e d

such

t h a t t h e volume

r a t i o

o f r e c y c l e d a q u e o u s b o t t o m s

g o i n g t o

t h e

r e a b

s o r b e r t o t h e e t h y l e n e

o x i d e w a t e r m i x t u r e g o i n g i n t o

t h e g l y c o l r e a c t o r ,

was

about 5 . 3 . A r i p l e e f f e c t evapo

r a t o r was employed

t o

r e m o v e water f r om

t h e

g l y c o l s

and

d e i o n i z e d

carbon t r e a t e d

d e g a s s e d

w a t e r from t h e

e t h y l e n e o x i d e

s t r i p p e r s

was

used

a s r e f lu x

m e d i u m .

F r o m t h e e v a p o r a t o r , t h e e t h y l e n e g l y c o l s bottoms was

p a s s e d

t o

a d r y i n g column operated

a t 1 5 0 F . and 2 0 0

m i l l i m e t e r s of

mercury p r e s s u r e ,

whereup on t h e r e

maining

water

was removed o v e r h e a d .

The e t h y l e n e

g l y c o l s

bottoms was t h e n p a s s e d

t o

t h e ? r s t column i n

a

d i s t i l l a t i o n

t r a i n

wherein t h e c ol u m n

was

operated a t

a t o p temperature

and

p r e s s u r e of

1 9 6 F . and 1 0

m i l l i

meters

o f v

mercury,

and t h e overhead monoethylene

g l y c o l p r o d u c t met

? b e r

g r a d e

s p e c i ? c a t i o n s

h e r e i n b e

f o r e

de?ned.

The

a c t i v a t e d

c a r b o n employed

i s

p r e f e r a b l y m a d e

from bituminous c o a l b u t

bone

c h a r c o a l

and w o o d

c h a r c o a l

t y p e s can be employed.

The

p r o c e s s equipment employed

was

c o m m e r c i a l l y

a v a i l a b l e

e q u i p m e n t a n d

s u i t a b l e

e q u i p m e n t i s r e a d i l y

a v a i l a b l e ,

p r e f e r a b l y

h o w e v e r , n o n ~ c o r r o s i v e e q u i p

m e n t i s employed

such

a s t h a t

m a d e of

s t a i n l e s s

s t e e l .

While

t h e i n v e n t i o n

h a s been d e s c r i b e d w i t h r e f e r

ence

t o c e r t a i n

speci?c embodiments, i t

i s

not intended

t o be l i m i t e d thereby except

i n s o f a r a s

appears i n t h e

a c c o m p a n y i n g c l a i m s .

I

c l a i m :

1 . I n

t h e combined

manufacture

o f e t h y l e n e

o x i d e

and e t h y l e n e g l y c o l s which i n c l u d e s t h e s t e p s o f :

a . r e a c t i n g oxygen and e t h y l e n e i n a r e a c t o r i n t h e

presence of

a

c a t a l y s t a t elevated

temperatures

t o

p r o d u c e

e t h y l e n e

o x i d e ;

b . a b s o r b i n g e t h yl e n e o x i d e p r o d u c e d i n

s t e p

( a ) i n

water i n an absorber t o p r o d u c e a n ethylene

oxide

water stream;

0 .

stream

s t r i p p i n g

e t h y l e n e

o x i d e

from t h e e t h y l e n e

o x i d e - w a t e r

s t r e a m

produced

i n s t e p

( b )

i n a

s t r i p

p i n g

column

t o

produce

an e t h y l e n e o x i d e over

7/24/2019 Us 3904656 patent

6/6

3 , 9 0 4 , 6 5 6

7

h e a d stream a n d a n a q u e o us b o t t o ms

stre am

a n d

r e c y c l i n g

a q u e o u s b o t t o m s from t h e s t r i p p i n g c o l

umn o t h e absorber o f

s t e p ( b ) ;

d .

r e a b s o r b i n g

s t r i p p e d

e t h y l e n e

o x i d e f r o m

s t e p

( c )

i n water i n

a

reabsorbing column

t o

provide

an

e t h

y l e n e o x i d e - w a t e r s t r e a m ;

e .

forwarding

t o

a

glycol reactor a portion

of

the eth

y l e n e

oxide-water

stream p r o d u c e d i n

s t e p

( d ) a n d

r e a c t i n g e t h y l e n e

o x i d e

c o n t a i n e d t h e r e i n

w i t h

water

t o

produce

a

product stream comprising

e t h

y l e n e

g l y c o l s

i n w a t e r ;

f .

e v a p o r a t i n g

water from t h e product stream pro

d u ce d i n s t e p ( e )

i n

an e v a p o r a t o r t o produce a g l y

c o l s

p r o d u c t s t r e a m ,

a n d r e c y c l i n g

e v a p o r a t e d

water t o

t h e

r e a b s o r b i n g c olumn o f

s t e p

( d ) ;

g . d i s t i l l i n g t h e g l y c o l s p r o d u c t s t r e a m p r o d u c e d

i n

s t e p f )

t o

p r o d u c e a m o n o e t h y l e n e

g l y c o l

p r o d u c t ;

a n d

h .

d i s t i l l i n g a p o r t i o n o f t h e e t h y l e n e o x i d e - w a t e r

s t r e a m produced i n

s t e p

( d ) i n

an

e t h y l e n e o x i d e

r e ? n i n g column t o

p r o v i d e

an overhead e t h y l e n e

oxide produc t stream an an a q u e o u s

bottoms

s t r e a m ,

and r e c y c l i n g aqueous bottoms from t h e

r e f i n i n g

column

t o

t h e r e a b s o r b i n g column o f

s t e p

d ) ;

t h e i mprovement which

comprises

( 1 )

r e m ov ng a s

a

1 0

8

purge

stream

a p o r t i o n of

t h e recycled aqueous

bot

toms

from t h e s t r i p p i n g column o f s t e p

( c ) , s a i d

p o r t i o n

b e i n g s u f f i c i e n t t o m a i n t a i n

t h e

w a t e r b a l a n c e in

t h e

ab

s o r b i n g c o l u m n - s t r i p p i n g

c o l u m n

s y s t e m of

s t e p s ( b )

a n d ( c ) , ( 2 ) t r e a t i n g purge stream water w i t h c a t i o n e x

change m a t e r i a l s t o

remove

i n o r g a n i c s a l t s

t h e r e f r o m ,

degassing

the

p u r g e st r e a m

water,

and

c ont ac t i ng i on

exchange-treated purge stream

water

with

a c t i v a t e d

carbon

t o

remove u l t r a v i o l e t

l i g h t

a b s o r b e r s

t h e r e f r o m ,

( 3 ) forwarding t h u s t r e a t e d

purge

stream water

t o

t h e

reabsorber of s t e p ( d ) o r t h e

evaporator

of s t e p ( f ) o r

b o t h ,

and

( 4 ) m a i n t a i n i n g t h e

v o l u m e t r i c

r a t i o

of i )

20

25

35

45

55

6 5

aqueous b o t t o m s from t h e r e ? n i n g

column

o f s t e p ( h )

r e c y c l e d

t o

t h e r e a b s o r b i n g column o f

s t e p

( d )

t o i i )

t h e e t h y l e n e

o x i d e - w a t e r s t r e a m forwarded

t o t h e g l y

c o l r e a c t o r a t

a

v a l u e n o t g r e a t e r t h a n 6 , thereby

pro

d u c i n g e t h y l e n e o x i d e a n d ? b e r g r a d e m o n o e t h y l e n e

gl y c ol .

2.

The p r o c e s s

o f c l a i m 1

wherein t h e r a t i o

of

i ) / i i )

i s

n o t

g r e a t e r

t h a n

5 . 3 .

3 . The

p r o c e s s

o f c l a i m 1 w h e r e i n d e g a s s e d p u r g e

stream water

s t r e a t e d w i t h a n i o n exchange m a t e r i a l i n

t h e hydroxyl form b e f o r e contact

w i t h

a c t i v a t e d

c a r