METAL-ORGANIC COMPOUNDS

---

Chemical Corps Experience in the Manufacture of Lewisite

GORDON N. JARMAN

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Process Development Division, Chemical Warfare

Laboratories, Army Chemical Center, Md.

The U. S. Army Chemical Corps produced 20,000 tons of lewisite [dichloro(2-chlorovinyl)arsine] during World War II. After one false start, an operationally simple batch process was chosen. It involved condensation of acetylene with arsenic trichloride in the presence of mercuric chloride in aqueous hydrochloric acid. Development concurrently was able to devise more economic processes using cheaper catalysts. They were also more complex in equipment and operational requirements. The batch process used less than one year from test tube to tank car. The combined experience demonstrated the usefulness of simplicity in process design when the certainty of early production is the overriding consideration.

Lewisite i s t h e c o m m o n n a m e f o r a c h e m i c a l agent w h i c h has d i c h l o r o ( 2 - c h l o r o v i n y l ) arsine as i t s a c t i v e c o n s t i t u e n t . T h e C h e m i c a l C o r p s m a n u f a c t u r e d l e w i s i t e d u r i n g W o r l d W a r s I a n d I I , b u t i t d i d n o t receive b a t t l e f i e l d test. T h e agent h a d n o t r e a c h e d t h e t h e a t e r o f o p e r a t i o n s i n W o r l d W a r I w h e n t h e A r m i s t i c e c a m e i n t o effect a n d i n W o r l d W a r I I none of t h e c o m b a t a n t s r e s o r t e d t o c h e m i c a l w a r f a r e . I n f o r m e d o p i n i o n o n t h e v a l u e o f l e w i s i t e as a n agent fluctuated, as test results b e c a m e a v a i l a b l e . T h e f a v o r a b l e o p i n i o n b e c a m e s t r o n g a r o u n d 1940 w h e n t h e decision to manufacture lewisite was made. L a r g e scale tests i n 1943 p r o v e d t h a t c o m p a r e d t o m u s t a r d gas, i t w a s n o t a p r o f i t a b l e m a t e r i a l t o h a v e . P r o d u c t i o n w a s s t o p p e d , a l ­ t h o u g h 20,000 t o n s h a d been m a d e . T h e r e w a s n o l a c k of desire a n d effort t o a r r i v e a t a d e f i n i t i v e d e c i s i o n e a r l i e r , b u t t h e p r o p e r t i e s o f l e w i s i t e c o m b i n e d w i t h t h e test f a c i l i t i e s a v a i l a b l e m a d e i t p r a c t i c a l l y i n e v i t a b l e t h a t t h e sequence, as o b s e r v e d , w o u l d o c c u r . T h eChemical C o r p s p r i o r t o 1940 h a d n e i t h e r t h e l a b o r a t o r y n o r field t e s t i n g f a c i l i t i e s needed t o r e a c h s u c h a c o n c l u s i o n . A s f u n d s b e c a m e a v a i l a b l e , e x i s t i n g o u t s i d e l a b o r a t o r i e s were d i v e r t e d t o r e s e a r c h i n c h e m i c a l w a r f a r e a n d t h e e x p a n s i o n of l o c a l l a b o r a t o r y f a c i l i t i e s was e x p e d i t e d . A d e q u a t e field test f a c i l i t i e s were o b t a i n e d m o r e s l o w l y . T i m e w a s r e q u i r e d t o f o r m a d o c t r i n e f o r a n e w t y p e of t e s t i n g f o r w h i c h f u n d s h a d p r e v i o u s l y been e x t r e m e l y l i m i t e d . E l a b o r a t e f a c i l i t i e s h a d t o b e b u i l t . A t e a m c o n t a i n i n g t h e d i v e r s e skills needed had to be f o r m e d , i n d o c t r i n a t e d , a n d t r a i n e d i n an u n f a m i l i a r field. 328

METAL-ORGANIC COMPOUNDS Advances in Chemistry; American Chemical Society: Washington, DC, 1959.

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JARMAN—MANUFACTURE OF LEWISITE

L e w i s i t e i s h i g h l y t o x i c , c a u s i n g p r o f o u n d p h y s i o l o g i c a l effects b y b o t h i n h a l a t i o n a n d skin contact. I t i s stable i n m o s t l a b o r a t o r y e n v i r o n m e n t s , e s p e c i a l l y f o r t h e s h o r t t i m e i n v o l v e d i n w o r k w i t h i t . O n t h e o t h e r h a n d , i t is r a p i d l y h y d r o l y z e d i n t h e presence o f m o i s t u r e w h i c h i s u s u a l l y p r e s e n t i n e a r t h a n d v e g e t a t i o n ; hence i t i s l a r g e l y d e s t r o y e d o v e r t h e l o n g e r p e r i o d s i n v o l v e d i n field tests.

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I t w a s i n e v i t a b l e t h a t w h e n l e w i s i t e r e a c h e d a d e q u a t e field t e s t i n g i t w o u l d f a i l as a n agent, e v e n t h o u g h l a b o r a t o r y results were v e r y f a v o r a b l e . I t w a s so u n s t a b l e u n d e r a v e r a g e field c o n d i t i o n s t h a t m u c h o f i t s t o x i c i t y w a s l o s t . U n f o r t u n a t e l y , l a b o r a t o r y m e t h o d s a t t h a t t i m e h a d n o t been d e v e l o p e d t o a r o u t i n e w h i c h w o u l d h a v e p r e d i c t e d s u c h a sequence. T h e e r r o r i n t h e d e c i s i o n t o p r o d u c e l e w i s i t e is, n a t u r a l l y , of h i s t o r i c a l i n t e r e s t o n l y . It has n o bearing o n the interesting problems involved i n the manufacture a n d t h e c r e d i t due f o r t h e i r successful s o l u t i o n . T h e a l u m i n u m c h l o r i d e process f o r t h e m a n u f a c t u r e o f l e w i s i t e w a s a b o u t t o b e p u t t h r o u g h t h e u s u a l p i l o t p l a n t , p r o d u c t i o n p l a n t r o u t i n e i n e a r l y 1941. A t t h a t t i m e C o n a n t b r o u g h t b a c k f r o m E n g l a n d news of a successful r e a c t i o n o f arsenic t r i c h l o r i d e a n d a c e t y l e n e i n t h e presence o f aqueous m e r c u r i c c h l o r i d e . T h e n e w m e t h o d , e v e n f r o m t h e p r e l i m i n a r y e v a l u a t i o n possible, p r o m i s e d s u b s t a n t i a l o p e r a t i o n a l a n d e q u i p m e n t s i m p l i f i c a t i o n . A l t h o u g h t h e a l u m i n u m c h l o r i d e process h a d been o p e r a t e d a t t h e p i l o t p l a n t l e v e l , t h e m e r c u r i c c h l o r i d e process s t i l l a p p e a r e d t o b e a faster r o u t e t o p r o d u c t i o n . T h i s p r o v e d t o b e a s o u n d c o n c l u s i o n . T h e r e were o t h e r f a c t o r s i n v o l v e d . M e r c u r i c c h l o r i d e , w h i l e scarce a n d e x p e n s i v e , was t h e o r e t i c a l l y n o t c o n s u m e d a n d t h e m a i n d r a i n o n stocks w o u l d b e b u i l d i n g u p plant inventory. O n t h e other hand, t h e a l u m i n u m chloride charged would a l l be lost as a u s e f u l m a t e r i a l c o n s t i t u t i n g , i n f a c t , a s u b s t a n t i a l d i s p o s a l p r o b l e m , c o n ­ t a m i n a t e d as i t w o u l d b e w i t h a r s e n i c . D e p e n d i n g o n a s t e a d y s u p p l y o f a l u m i n u m m e t a l f o r a l u m i n u m c h l o r i d e p r o d u c t i o n d i d n o t seem safe, w h i l e t h e w a r effort d e m a n d e d t h e m e t a l f o r o t h e r v i t a l uses. U n f o r t u n a t e l y , e n g i n e e r i n g was a l l o w e d t o sell r e s e a r c h o n t h e p r o p o s i t i o n t h a t t h e o n l y a c c e p t a b l e l a r g e scale p r o d u c t i o n process was a c o n t i n u o u s one. A s a consequence, r e s e a r c h a b a n d o n e d i t s field of c o m p e t e n c e a n d s t a r t e d o n t h e d e v e l o p m e n t of process equipment. I n a surprisingly short time lewisite was produced a n d p r o u d l y exhibited as t h e p r o d u c t o f a c o n t i n u o u s process. T h e decision was made t o start a pilot p l a n t at once.

50 mm.

AT AT STRIPPING TILL

PUMP

CATALYST

Figure

1.

Flow

SEPARATOR

sheet of mercuric process

chloride continuous

METAL-ORGANIC COMPOUNDS Advances in Chemistry; American Chemical Society: Washington, DC, 1959.

ADVANCES IN CHEMISTRY SERIES

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T h e p i l o t p l a n t w a s u n i q u e . M o s t of t h e c o n s t r u c t i o n w a s d o n e b y engineers a n d h i g h l y s k i l l e d a n d e x p e r i e n c e d p l a n t o p e r a t o r s . P r a c t i c a l l y n o d r a w i n g s were u s e d . R e s e a r c h m e n were c o n s u l t a n t s a n d d e s c r i b e d , o n t h e j o b , t h e f u n c t i o n s o f t h e p l a n t . I t w a s m a d e o f w h a t e v e r c o u l d b e f o u n d a v a i l a b l e a n d w a s a reasonable f a c s i m i l e o f w h a t r e s e a r c h s a i d w a s needed. I t w a s c o m p l e t e d i n a t i m e e x t r e m e l y s h o r t t o one f a m i l i a r w i t h t h e u s u a l p i l o t p l a n t schedule. I t w o r k e d w e l l e n o u g h t o b e e v a l u a t e d . O n s t a r t - u p t h e engineers were d i s m a y e d a t t h e t i n y s t r e a m o f l e w i s i t e r e s u l t i n g f r o m t h e l a r g e e n e r g y i n p u t , b u t i t w a s a p p a r e n t t h a t r e s e a r c h w a s pleased. Engineer­ ing measured streams, calculated ratios, a n d power consumption. Research, viewing t h e r e s u l t s , i n t i m a t e d t h a t t h e y were r i g h t i n l i n e . A slide r u l e c a l c u l a t i o n of t h e results w i t h i n t r o d u c t i o n o f t h e u l t i m a t e p r o d u c t i o n g o a l w a s a l l t h a t w a s needed t o c o n f i r m t h a t i t w a s e v e n worse t h a n s u s p e c t e d a t first. T h e f i n a l p l a n t w o u l d h a v e t h e largest a n d / o r m o s t r e a c t i o n t o w e r s e v e r a s s e m b l e d i n one s p o t . I n a d d i t i o n , t h e p u m p i n g e q u i p m e n t c o u l d h a v e m a d e a s u b s t a n t i a l c o n ­ tribution i n reversing N i a g a r a . E n g i n e e r i n g w r o t e off t h e losses; b u t " c o n t i n u o u s " as a p p l i e d t o a l e w i s i t e process was a n u n m e n t i o n a b l e w o r d f o r some t i m e . B a t c h o p e r a t i o n w a s t h e o r d e r o f t h e d a y . T h e b a t c h o p e r a t i o n w a s successful. T h e pilot plant operated during most of 1942 a n d p a r t of 1943. T h e first p r o d u c t i o n p l a n t w a s r e a d y i n l a t e 1942 a n d t h e second a n d t h i r d p l a n t s e a r l y i n 1943. P r o d u c t i o n w a s s t o p p e d l a t e i n 1943, w i t h a t o t a l o f o v e r 20,000 t o n s . T h i s was a v e r y s u b s t a n t i a l a c h i e v e m e n t , t a k i n g i n t o a c c o u n t t h a t t h e c a t a l y s t was first h e a r d o f i n 1941. I n t h e m e a n t i m e , d e v e l o p m e n t p r o c e e d e d a l o n g t w o l i n e s : first, s o l u t i o n o f p l a n t p r o d u c t i o n p r o b l e m s a n d second, c o n s i d e r a t i o n o f o t h e r c a t a l y s t s a n d processes. B o t h efforts were successful.

Composition of Lewisite P u r e d i c h l o r o ( 2 - c h l o r o v i n y l ) a r s i n e i s a colorless, s l i g h t l y o i l y , n e a r l y odorless l i q u i d . I t h a s t h e s t r u c t u r e w h i c h shows space i s o m e r s . B o t h h a v e b e e n i s o l a t e d a n d s h o w n t o b e stable b e l o w 1 0 0 ° C . T h e often described " g e r a n i u m " odor of the c o m ­ p o u n d i s a consequence o f t h e process o f m a n u f a c t u r e , b e i n g r e a d i l y i d e n t i f i e d o n l y i n t h e p r o d u c t o f t h e a l u m i n u m c h l o r i d e process. Vapors of a n y sample i n a i r are r e a d i l y d e t e c t e d , b u t t h e s e n s a t i o n i s u s u a l l y one o f a c i d i r r i t a t i o n r a t h e r t h a n of a n odor. Lewisite is a t e r m p r o p e r l y applied t o t h e mass p r o d u c t i o n p r o d u c t containing m a i n l y β-chlorovinyl, mixed w i t h other allied compounds. I t is a brownish l i q u i d , inert t o steel, a n d i n d e f i n i t e l y stable i n closed storage. T h e materials present are shown i n Table I .

Table I.

Compositions of Lewisite Composition of Crude

Component AT, AsCh Li, C1CH :CHAsCh cis trans L2, ( C l C H : C H ) A s C l L3, ( C l C H : C H ) A s 2

3

B.P., °C.

HgCh process,

AlCh Process,

130

40

39

150 190 230 260

Nil 55 5 Nil

Nil 10.5 26.5 24

%

%

After rework ca.Vo ca. 70

L 2 a n d L 3 come f r o m further reaction of L I w i t h acetylene. T h e very high p r o p o r t i o n o f these m a t e r i a l s i n t h e a l u m i n u m c h l o r i d e - c o n t r o l l e d c o n d e n s a t i o n , c o m ­ pared t o that observed w i t h m e r c u r y , is p r o b a b l y due t o physical factors. T h e a l u m i n u m chloride reaction is homogeneous a n d a p p a r e n t l y L I is more reactive t h a n AT. O n t h e o t h e r h a n d L I i s n e a r l y i n s o l u b l e i n aqueous a c i d a n d AT s o l u b i l i t y i s

METAL-ORGANIC COMPOUNDS Advances in Chemistry; American Chemical Society: Washington, DC, 1959.

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J ARMAN—MANUFACTURE OF LEWISITE

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l i m i t e d . A second, arsenic phase is a l w a y s p r e s e n t i n t h e m e r c u r y process a n d a l l t h e LI is i n t h i s phase. T h e r e f o r e , AT h a v i n g a f a i r s o l u b i l i t y i n t h e c a t a l y s t phase h a s a f a r h i g h e r p r o b a b i l i t y of r e a c t i n g w i t h a n y fixed a c e t y l e n e . L I , t h o u g h m o r e r e a c t i v e , g i v e n t h e same e n v i r o n m e n t , c a n r e a c t o n l y a t t h e o r g a n i c - a q u e o u s i n t e r f a c e , w h i c h reduces t h e n e t r a t e s u b s t a n t i a l l y . T h e s p e c i f i c a t i o n c o m p o s i t i o n of l e w i s i t e i s w h a t e v e r q u a l i t y c o n t r o l c a n m a i n t a i n i n debate w i t h p r o d u c t i o n . B o i l i n g p o i n t r e l a t i o n s a r e s u c h as t o a l l o w s e p a r a t i o n o f a v e r y p u r e p r o d u c t . I n a c t u a l p r a c t i c e , m e r c u r y process p r o d u c t w a s c r u d e m o r e o r less c o m p l e t e l y s t r i p p e d of AT. T h e a l u m i n u m process p r o d u c t d i d n o t r e a c h t h e p r o d u c t i o n stage. A n a l y s i s of lewisite was v e r y accurate a n d complete. Considering the time i n ­ v o l v e d f o r d e v e l o p m e n t of m e t h o d s , t h e a c c u r a c y a n d p r e c i s i o n were r e m a r k a b l e . M e t h o d s a r e o n file i n t h e C o r p s f o r a l l c o m p o n e n t s o f t h e p r o d u c t a n d b y - p r o d u c t s t r e a m s . T h e d e t a i l s c a n b e o b t a i n e d o n a p p l i c a t i o n t o t h e Office o f t h e C h i e f C h e m i c a l Officer, W a s h i n g t o n 2 5 , D . C .

Processes T h e r e a c t i o n s b y w h i c h l e w i s i t e h a s been M e t h o d s n o t u s i n g c a t a l y s t s h a v e been left o u t .

Table II. Catalyst AlCla HgCh

Media None

C112CI2

H2O

H2O

made

are mentioned

i n Table I I .

List of Processes Studied Additive None HC1 SbCla 4- HC1 HC1 Ethanolamine, HC1

Operation Batch—pilot Batch—prod. Cont.—dev. Batch—res. Batch—dev. Cont.—dev. Batch—dev. Cont.—dev.

A l u m i n u m Chloride Process. T h e a l u m i n u m c h l o r i d e process was o p e r a t e d i n t h e p i l o t p l a n t e s s e n t i a l l y as s h o w n i n t h e flow sheet. T h e r a t i o of A T t o a l u m i n u m c h l o r i d e w a s 9 t o 1. T h e o r i g i n a l scheme w a s t o r e c o v e r t h e u n r e a c t e d AT t o g e t h e r w i t h product b y heating the reaction mass. T h e result was a n explosion near t h e e n d of the d i s t i l l a t i o n . T h e e x p l o s i o n c o u l d o f t e n b e a v o i d e d b y r i g i d p r e c a u t i o n s i n t h e d i s t i l l a t i o n , b u t i t s t i l l o c c u r r e d w i t h sufficient f r e q u e n c y t o m a k e t h e o p e r a t i o n u n ­ popular. I t w a s suspected t h a t a n a c e t y l i d e w a s p r e s e n t w h i c h a c c u m u l a t e d t o t h e p o i n t where its characteristically r a p i d decomposition occurred. T h e remedy proposed was t o heat i t i n d r i b l e t s t o a b o v e t h e d e c o m p o s i t i o n t e m p e r a t u r e i n s u c h a w a y t h a t t h e release o f e n e r g y w o u l d n o t w r e c k t h e e q u i p m e n t . A flash b o i l e r h e a t e d a b o v e t h e d r y point was indicated, b u t i t could n o t be used o n a m i x t u r e containing large amounts of relatively nonvolatile a l u m i n u m chloride. H y d r o c h l o r i c acid w o u l d e x ­ tract the a l u m i n u m chloride without hydrolyzing the product, i f the acid concentra­ t i o n was w e l l o v e r 2 0 % . T h e scheme w o r k e d . T h e r e w e r e n o m o r e e x p l o s i o n s , e i t h e r i n t h e l a b o r a t o r y o r i n the p i l o t p l a n t . T h e d i s p r o p o r t i o n a t i o n r e a c t o r w a s t h e source o f t h e cis i s o m e r . L2 a n d L3 i n s h a r i n g the excess of o r g a n i c g r o u p s w i t h AT p r o d u c e b o t h cis a n d t r a n s i s o m e r s . T h e a l u m i n u m c h l o r i d e process m a k e s v e r y g o o d l e w i s i t e , b u t uses a n excessive a m o u n t of e q u i p m e n t a n d e n e r g y . A l s o , a l u m i n u m c h l o r i d e is c o n s u m e d a n d a p p e a r s i n an unpleasant by-product stream. M e r c u r i c Chloride Process. T h e m e r c u r i c c h l o r i d e process uses less e q u i p m e n t , a l t h o u g h a l i t t l e m o r e t h a n was first v i s u a l i z e d . T h e basic o p e r a t i o n s i n t h e process i n v o l v e : t h e c o n d e n s a t i o n o f excess AT w i t h

METAL-ORGANIC COMPOUNDS Advances in Chemistry; American Chemical Society: Washington, DC, 1959.

ADVANCES IN CHEMISTRY SERIES

332

Al Cl,

Ci Η,

REALTOR! cooling

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ACID WASH KETTLE

Η , Ο loyer

I

SURGE

vent

j

heat _ r FLASH STILL

Κ

SURGE

Figure 2 . Flow sheet of aluminum chloride process a c e t y l e n e , a h e a t i n g p e r i o d t o r e a c t o r g a n o m e r e u r y c o m p o u n d s , s e p a r a t i o n of t h e product from the catalyst layer a n d the v a c u u m distillation, separation, a n d recycling of excess AT. T h i s process, w h i l e r e a d i l y w o r k a b l e , h a s some u n f o r t u n a t e features. T h e c a t a l y s t is h e a v i e r t h a n t h e p r o d u c t a n d i t i s e x p e n s i v e . Therefore, i t must be dropped a n d a l i t t l e o f t h e p r o d u c t d r o p p e d w i t h i t t o w a s h o u t lines a n d v a l v e s . I n t h e e a r l y stages o f d e v e l o p m e n t i t w a s f o u n d t h a t as A T w a s r e m o v e d f r o m t h e m i x t u r e , a s o l i d i d e n t i f i e d as arsenic t r i o x i d e s e p a r a t e d i n c o p i o u s a m o u n t s i n t h e s t i l l p o t . T h e process w a s v e r y d i m l y r e g a r d e d u n t i l r e s e a r c h c a m e u p w i t h t h e i d e a t h a t 5 % of t h i o n y l c h l o r i d e b a s e d o n p r o d u c t w e i g h t w o u l d p r e v e n t t h i s , w i t h o u t serious c o n ­ t a m i n a t i o n o f t h e p r o d u c t . A t t h e t i m e i t s a v e d t h e process, e v e n i f i t i n v o l v e d g o i n g i n t o t h e p r o d u c t i o n o f t h i o n y l c h l o r i d e , a l t h o u g h l a t e r a n o t h e r m e t h o d was u s e d . T h e source o f t h e arsenic t r i o x i d e i s loss of h y d r o c h l o r i c a c i d b y t h e s y s t e m i n t h e f o r m a t i o n o f t h e b y - p r o d u c t v i n y l c h l o r i d e . A s t h e c a t a l y s t is d e p l e t e d o f h y d r o g e n chloride, the concentration drops t o the point where a balance is reached between v i n y l c h l o r i d e f o r m a t i o n a n d h y d r o l y s i s o f AT. C H 2

2

+ HC1->C1CH:CH

*As 0 2

3

2

+ 3 H C 1