8/11/2019 Separation of Phthalic Anhydride

1/2

P a t e n t e d

O c t . 2 9 ,

1 9 4 0

U N I T E D S T A T E S

* 2 , 2 2 0 , 0 4 4

PATENT OFFICE

2 , 2 2 0 , 0 4 4

SEPARATION OF ALEIC AND HTHALIC

ANHYDRIDE

A l p h o n s

0 . J a e g e r , G r e e n w i c h ,

C o n n . ,

a s s i g n o r

t i

American Cyanamid'& C h e m i c a l C o r p o r a t i o n ,

New

o r k ,

N .

Y . , ' a

c o r p o r a t i o n

o f Delaware

N

Drawing. A p p l i c a t i o n September , 1 9 3 9 ,

.

Serial

No. 293,619

3 C l a i m s .

T h i s

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

t o

t h e

p r o d u c t i o n

and

recovery

o f

maleic a c i d o r

anhydride

f r o m

the

c a t a l y t i c oxidation o f

org anic c o m p o u n d s

in

which maleic

anhydride

i s

obtained

a s

a by

5 product _

In

t h e c a t a l y t i c v a p o r phase

o x i d a t i o n

o f

n a p h

thalene t o

p h t h a l i c a n h y d r i d e ,

a

g r e a t e r o r

l e s s

a m o u n t

o f

maleic

anhydride i s

produced a s

a by

product

a n d f

t h e

naphthalene s admix ed

with

1 0 p h e n o l s ,

wood

a r , b e n z o i c a c i d , b e n z e n e , f u r f u r a l ,

t h i o p h e n e , t e r p e n e s , c y c l o p e n t a d i e n e o r o t h e r ,

compounds c o n t a i n i n g

u n s a t u r a t e d

l i n k a g e s ,

l a r g e r

amounts

o f m a l e i c anhydride a r e p r o

d u c e d .

S i m i l a r l y ,

i f t h e naphthalene s o m i t t e d ,

1 5

m a l e i c

anhydrideis produced

a s

o n e

o f

t h e

prod

u c t s

although i n

somewhat

s m a l l e r

y i e l d s .

In

the g a s e s c o m i n g f r o m the

v a p o r

phase con

v e r t e r , t h e m a l e i c a c i d , o f c o u r s e ,

i s

p r e s e n t

mainly i n

t h e

fo r m o f t h e anhydride which s a

2 0 v e r y

v o l a t i l e

s u b s t a n c e a nd cannot

n o r m a l l y

be

c o n d e n s e d c o m p l e t e l y

by

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

t y p e

o f

c o n d e n s e r , due

t o

t h e

p r e s e n c e o f

l a r g e

volumes

o f d i l u t i n g g a s e s . I t

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

f o r e , t o p r o v i d e a l i q u i d

a b s o r p t i o n

s y s t e m . o r

g a n i c o r

i n o r g a n i c ,

u s u a l l y employing

a

s o l u t i o n

of m a l e i c a c id in

water

a s an a bsor b i n g

medium

a s d e s c r i b e d

a n d

claimed

i n t h e patent

t o

Jaeger

a n d

J e w e t t ,

N o . 2 , 0 9 8 , 0 4 7 d a t e d

November

,

1 9 3 7 .

I n

t h e p a s t t h e m a l e i c

a n h y d r i d e

p r e s e n t i n

t h e

3 0 c o n v e r t e r g a s e s ,

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

in the c a s e o f

the'

vapor

phase o x i d a t i o n

o f naphthalene

t o form

p h t h a l i c

anhydride a s a primary p r o d u c t , y h a s

been

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

o f

t h e

f a c t that a c e r t a i n proportion o f

the maleic

a n

3 5 h y d r i d e c o n d e n s e s with t h e

p h t h a l i c

anhydride

b e f o r e

r e a c h i n g t h e

l i q u i d a b s o r p t i o n

s y s t e m . I n

the

c a s e o f p l a n t s

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

d e s i g n e d

f o r

pro

duction o f phthalic anhydride,

t h i s

l o s s o f the

maleic anhydride present

m a y

a m ou n t

t o

a s

40

much s

50 .

Sin c e

m a l e i c a c i d

and

a l e i c a n -

h y d r i d e d e m a n d

a

h i g h e r p r i c e than

d o e s

p h t h a l

' i c a n h y d r i d e

and

t h e d e m a n d f o r

m a l e i c anhy

d r i e d

and

a c i d

i s

c o n s t a n t l y

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

i s

a

s e r i o u s economic f a c t o r a n d i t i s t h e

o b j e c t

4 5

o i

t h e

p r e s e n t

i n v e n t i o n t o r e d u c e t h i s

l o s s .

A c c o r d i n g

t o

t h e

p r e s e n t

i n v e n t i o n ,

c o n v e r t e r

gases f r o m the v a p o r

p h ase

c a t a l y t i c oxidation o f . ,

or ga n i c

compounds,

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

which c o n t a i n

' m a l e i c anhydride

i n a d d i t i o n

t o

50 other c o m p ounds such as

p h t h a l i c

anhydride, are

. t h e gases

because

a n e ? e c t i v e s c r u b b i n g s y s t e m ,

( C l . 2 6 0 - 5 3 7 )

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

a l i q u i d

s c r u b b i n g s y s t e m , b u t i n s t e a d

o f

c o o l i n g

the condensers e x t e r n a l l y

t o

as low a t e m p e r a

t u r e a s p o s s i b l e , they a r e maintained a t a ,t e m

p e r a t u r e

s u ? i c i e n t l y

high s o

t h a t m a l e i c anhy- 5

d r i d e remains v o l a t i l e .

In t h i s m a n n e r ,

maleic

anhydride i s

p r e v e n t e d

from c o n d e n s i n g

i n

s o l i d

f o r m a n d

s

recovered m o r e o r

l e s s

completely by

t h e l i q u i d s c r u b b i n g s y s t e m . W h i l e any

d e s i r e d

m e t h o d

o f m a i n t a i n i n g t h e t e m p e r a t u r e

i n

t h e 1 0

c o n d e n s e r s above t h e

c o n d e n s i n g

p o i n t

o f

m a l e i c

anhydride

can

be

u s e d , , I

have

found

t h a t

a t

l e a s t

f o r t h e c o o l e r

p o r t i o n s

o f t h e

c o n d e n s e r , i t i s

p r e f e r a b l e

t o

i n j e c t

hot i r . which t i l l

f u r t h e r

d i

l u t e s

the gas

stream

a n d e r m i t s

maintaining

t h e

maleic anhydride i n the vapor s t a t e

a t

tempera- 1 5

t u r e s which

are l o w e r t h a n those

n e c e s s a r y

i f n o

d i l u t i o n had

t a k e n

p l a c e . The

c u r v e s

o f v o l a t i l i t y

o f m a l e i c anhydride

a n d p h t h a l i c

anhydride

a r e

such that a b e t t e r

s e p a r a t i o n

i s

obtained a n d hot

a i r

i s

a cheaper

a n d , i r o m a n o p e r a t i n g s t a n d -

2 0

p o i n t ,

s i m p l e r method

o f

o b t a i n i n g t h e d e s i r e d r e

s u l t s .

T h e

d i l u t i o n o f .

the g a s e s

does

ot

m a t e r i a l

l y - h i n d e r t h e c o m p l e t e n e s s w i t h which t h e l i q u i d

s c r u b b i n g system removes

m a l e i c

anhydride

from 2 5

s u c h a s - f o r

example

t h e s t a n d a r d s y s t e m d e

s c r i b e d i n t h e

J a e g e r

and

J e w e t t

p a t e n t a b o v e

r e f e r r e d t o ,

w i l l

r e m o v e v e r y e ? i c i e n t l y t h e m a l e i c

a n h y d r i d e

f r o m l a r g e

v o l u m e s o f d i l u t i n g g a s e s .

The

b e s t p o i n t a t which

t h e

hot i r s h o u l d be

i n j e c t e d g w i l l

i n g e n e r a l

v a r y w i t h

t h e n a t u r e o f

t h e c o n v e r t e r

g a s e s a nd a l s o w i t h t h e p h y s i c a l

d e s i g n o f t h e

c o n d e n s i n g

s y s t e m ,

I n

c a s e s where

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

a r e o b t a i n e d

from t h e c a t a

l y t i c o x i d a t i o n o f v a p o r s , t h e ? r s t

s e c t i o n s o f

t h e

condenser a r e

a t

a s u ? l c i e n t l y

e l e v a t e d

t e m p e r a

t u r e

s o t h a t

i t i s

not n e c e s s a r y .

t o i n j e c t

hot a i r

i n t o

t h e m ,

. t h e i n j e c t i o n

t h e r e f o r e t a k e s v p l a c e

6 9 0

f u r t h e r

back

i n the s e r i e s o f c o n d e n s e r s . The 4 0 9

temperature

t , which

t h e . a i r

i s

i n j e c t e d s h o u l d

be mainta ined below

the

p o i n t a t which i t

w i l l

r a i s e

the

temperature

0 1 '

t h e g a s e s t o o

high

t o

p e r m i t e ? e c t i v e c o n d e n s a t i o n

o f

t h e p h t h a l i c

an

hydride

,

' I

,

Whil e

the

use o f

the

p r e s e n t invention i n

c o n

j u n c t i o n w i t h . c o n v e r t e r

g a s e s

fro m

t h e

c a t a l y t i c

o x i d a t i o n

o f naphthalene r e s u l t s

i n

a small l o s s

i n

p h t h a l i c a n h y d r i d e , i t i s a n advantage o f

t h e

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

l o s s

i s k e p t

l o w

a n d i s n o r - 5 o

8/11/2019 Separation of Phthalic Anhydride

2/2

10

1 5

m a l l y a b o v e t h e

p o i n t

i n t h e c o n d e n s e r where h e

g r a d e

o f p h t h a l i c

a n h y d r i d e

p r o d u c e d i s r e l a

t i v e l y l o w .

Of

o u r s e ,

s m a l l l o s s e s

o f

p h t h a l i c a n

h y d r i d e

a r e

n o t s e r i o u s e c o n o m i c a l l y b e c a u s e o f

t h e l o w e r p r i c e which p h t h a l i c

a n h y d r i d e

c o m

mands

and

n

a d d i t i o n ,

t h e p h t h a l i c

a n h y d r i d e

i s

not r e a l l y l o s t a s i t i s d i s s o l v e d i n the aqueous

o

l u t i o n i n t h e

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

s y s t e m a n d

i s

r e m o v e d

i n the

p r o c e s s . o f puri?cation o f

the

m a l e i c

a c i d l i q u o r p r o d u c e d . I t

i s t r u e

t h a t t h e

p h t h a l i c

a c i d i s o b t a i n e d fro m such

p r o c e s s e s i n

the fo r m o f

the

a c i d

a n d

sometimes i n

a

fo r m

which s n o t v e r y p u r e , but t

i s

not e n t i r e l y

l o s t

a n d c a n be used

f o r

many

u r p o s e s ,

such as f o r

ex ample.

the

production o f e s t e r s . ~ I t i s

a n ad-

v a n t a g e o f

the 'presentinvention that

the g r e a t - '

l y i m p r o v e d r e c o v e r y o f m a l e i c a c i d i s

o b t a i n e d

_ l with but l i t t l e

l o s s

o f

phthalic anhydrid e.

' 2 0

80

The i n v e n t i o n

w i l l

be d e s c r i b e d i n

g r e a t e r

de

t a i l

i n

c o n j u n c t i o n

w i t h

a s p e c i ? c

example

which

d e a l s

with

a

c o n v e r t e r gas

f r o m a

p a r t i c u l a r type

o f p h t h a l i c a n h y d r i d e p l a n t . I t s h o u l d be

under

s t o o d ,

o f

c o u r s e ,

t h a t

t h i s i s merely a n l l u s t r a

t i o n and t h a t

t h e

t e m p e r a t u r e and volume o f t h e

g a s employed w i l l n e c e s s a r i l y v a r y w i t h c o n v e r t e r

g a s e s

fro m d i f f e r e n t o x i d a t i o n s . A c c o r d i n g l y , t h e

i n v e n t i o n

i s

n o t c o m p l e t e l y l i m i t e d t o t h e

s p e c i ? c

details

set

f o r t h

i n

the example.

_ I

Ezamlile

, I n

t h e

p a r t i c u l a r p l a n t

w i t h w h i c h

t h i s e x

a m p le i s . c o n c e r n e d , about 4 , 0 0 0 l b s .

o f

p h t h a l i c

a n h y d r i d e

a r e p r o d u c e d

daily

and p p r o x i m a t e l y

a s

4 , 0 7 0 l b s . o f naphthalene a r e consumed. 3 4 6 0 l b s .

o f the

naphthalene

a r e

converted

i n t o p h t h a l i c

a n h y d r i d e

a n d

t h e

b a l a n c e .

o r

6 1 0

l b s . ,

i s

con

v e r t e d

t o

o t h e r p r o d u c t s ,

t h e

major o n e b e i n g

maleic anhydride. ,

Th e

c o n v e r t e r g a s e s a r e passed

through a con

d e n s i n g

system

w h e r e ' p a r t i a l o r c o m p l e t e

con

d e n s a t i o n o f t h e p h t h a l i c a n h y d r i d e t a k e s p l a c e

a l o n g

w i t h

some

o f

t h e

m a l e i c

a n h y d r i d e , depend

i n g

upon the

r a t e o f t h e g a s c o o l in g a nd

the c o n

denser wall

temperatures.

6 6 The

c o n d e n s e r s y s t e m

o f

t h i s

p a r t i c u l a r p l a n t

i s

composed

o f

a s e r i e s o f t h r e e round c o n d e n s e r s

with r o t a r y

s c r a p e r s

a n d a fourth box type

c o n

d e n s e r

which i s

merely

eum

etal box

w i t h .

b e l l i e s a n d a n

opening

i n t o a fume

t o w e r .

Th e

c o n d e n s e r s ha v e a

r e l a t i v e l y l a r g e s u r f a c e

area

t o

p r e v e n t

l o s s

o f

p h t h a l i c

a n h y d r i d e through h e

fume t o w e r

e s p e c i a l l y

d u r i n g hot sum m e r

weath

e r .

Some

f

the

maleic

a n h y d r i d e passes t h r oug h

t h e

c o n d e n s e r s

and

t

i s r e c o v e r e d from

t h e

fume

t o w e r

g a s e s

b y t h e

p r o c e s s

o f

t h e

J a e g e r

a n d

Jewett

p a t e n t

m e n t i o n e d

heretofore.

D u r i n g t h e

winter m o n t h s the w a l l tempe ratures of the c o n

d e n s e r s ' d r o p

t o

a

c o n s i d e r a b l e e x t e n t

. w h i c h

c a u s e s

a

r e a t e r c o n d e n s a t i o n o f p h t h a l i c - a n h y

d r i d e i n

t h e

i i r s t

condenser a n d

a l s o

i n c r e a s e s

_

the

a m o u n t

o f

m aleic

anhydride

that condenses

i n t o t h e c o n d e n s e r s , c o n t a m i n a t i n g t h e p h t h a l i c

anhydride a n d a l s o r e s u l t i n g in a decrease

o f

the

m a l e i c a c i d r e c o v e r e d i n

t h e

tune t o w e r . r .

2 , 2 2 0 , 0 4 4

The f o l l o w i n g

t a b l e

s h o w s t h e

d i s t r i b u t i o n

o f

maleic a c i d i n the conde nsers which

i s

not

r e

c o v e r a b l e

from h e

i u m ' e

t o w e r g a s e s

under m e a n

summ e r c o n d i t i o n s a n d m e a n w i n t e r c o n d i t i o n s .

M e a n M e a n

m m ? , Z i a ? i i

m m n s l o i m s c i d

m a l e i c

8 6 1 1 1

First c o n d e n s e r

. . . .

.;

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

0 .

4 0 . 7

Second condenser. .

0 .

8

3 . 0

Third

o n d e n s e r . . . . . . . . . .

4 . 0

l 2 .

0

Box condenser . . . . . . . . . . .

.

... 1 0 . 0

3 5 . 0

T o t a l n o t

r e c o v e r a b l e i n t h

iume

tower

...... ..... .. -.--.-

16.2

I 6 0 . 7

An x a m i n a t i o n

o f

t h e - t a b l e shows t h a t t h e r e

i s

a o s s

o f o n l y

15.2

o f m a l e i c

a c i d

by

condensa

t i o n which i n d i c a t e s a r e c o v e r y 0 1 84.8 under

a ve r a ge summer

c o n d i t i o n s ,

whereas there i s a

l o s s

o f 50.7

a n d o n l y a r e c o v e r y o f

49.3

under

w i n t e r c o n d i t i o n s .

Th e

a b l e

a l s o

shows

that t h e

c o n d e n s a t i o n

o f

m a l e i c a c i d i n

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

v a r i e s ve ry l i t t l e between su m m e r

a n d winter

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

i n

t h e o t h e r con

d e n s e r s

under

w i n t e r

c o n d i t i o n s .

1 0

1 5 '

20

. 2 5

when pproximately 620 cubic

f e e t

per

m i nut e

o f hot a i r

a t

t h e temperature o f

1 3 0 - 1 ' l 0

C .

a r e

i n t r o d u c e d

i n t o

the

i n l e t o f

t h e

second

condenser

a n d

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

s m a l l e r

amounts

i n t o t h e

i n l e t

o f

t h e t h i r d

condenser

a n d the b o x c o n

d e n s e r , c o n d i t i o n s simulating those o f sum m e r

are obtained a n d the maleic

anhydride

vapors a r e

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

t h e fume

tower

where

t h e y

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

85-90 o f t h e t o t a l

q u a n t i t y p r o d u c e d by t h e

process.

W h a t

I

claim s :

1 . A m e t h o d

o f

i n c r e a s i n g the

r e c o v e r y

o f

m a l e i c a c i d f r o m ' c o n v e r t e r g a s e s from t h e c a t a

l y t i c vapor phase o x i d a t i o n o f o r g a n i c c o m

p o u n d s w h i c h

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

a n h y d r i d e ,

w h i c h

c o m p r i s e s p a s s i n g

t h e

g a s e s through a

s e r i e s

o f

c o n d e n s e r s

a t

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

t u r e s , f o l l o w e d by a n a b s o r b i n g s y s t e m i n which

m a l e i c a c i d i s

s c r u b b e d

o u t o f t h e g a s e s by

an

a q u e o u s

s o l u t i o n , i n j e c t i n g

h o t

permanent

g a s e s

s u b s t a n t i a l l y i n e r t t o m a l e i c a n h y d r i d e

a t

t h e

t e m p e r a t u r e

o f

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

con

d e n s e r s t o

maintain t h e t e m p e r a t u r e

i n

a l l o f

t h e

c o n d e n s e r s

a t a

p o i n t

above t h a t a t which

s u b s t a n t i a l

q u a n t i t i e s

o f

m a l e i c

a n h y d r i d e

a r e

condensed under t h e

p a r t i a l

p r e s s u r e o f m a l e i c

anhydride

e x i s t i n g i n

t h e

g a s i n q u e s t i o n , where

by t h e m a l e i c

a n h y d r i d e whichwould

o t h e r w i s e

c o n d e n s e i s c a r r i e d forward i n

t h e

v a p o r p h a s e

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

t h e r e

d i s - i

s ol v e d

a s

m a l e i c acid.

2 . A

r o c e s s a c c o r d i n g t o c l a i m 1

i n which

t h e

v a p o r

phase

o x i d a t i o n

i s a c a t a l y t i c v a p o r p h a s e

o x i d a t i o n o f n a p h t h a l e n e t o p h t h e l i c a n h y d r i d e .

3 .

A r o c e s s a c c o r d i n g t o claim i n

which

t h e

aqueous

s o l u t i o n

i n t h e a b s o r b i n s system

i s

a n

a q u e o u s

solution oi

m a l e i c

acid.

1

- ALPHONS

.

JAEGER

30

3 5

a