Catalytic Hydrodechlorination of Polychlorinated Hydrocarbons - ACS

3 Catalytic Hydrodechlorination of Polychlorinated Hydrocarbons 1

2

WILMER L. KRANICH, RENEB.LaPIERRE ,LASZLOGUCZI ,and ALVINH.WEISS

Downloaded by IOWA STATE UNIV on March 9, 2017 | http://pubs.acs.org Publication Date: June 30, 1978 | doi: 10.1021/bk-1978-0073.ch003

Department of Chemical Engineering, Worcester Polytechnic Institute, Worcester, MA 01609

Catalytic hydrodechlorination is one of the methods under consideration for conversion of chlorinated pesticides and other environmentally undesirable chlorinated compounds into environmentally acceptable products. LaPierre, Guczi, Wu, Kranich and Weiss (1-3) have reported on the reactions of DDT (and i t s derivative by simple dehydrochlorination, DDE), and Aroclor 1248 (a typical polychlorinated biphenyl). Both liquid and gas phase reactions were studied over a range of pressures from 1 to 50 bar, temperatures from 20 to 230°C and with both nickel and palladium catalysts. Solvents for liquid phase reactions included ethanol and xylene, and both calcium and sodium hydroxides were used as hydrochloric acid (by-product) acceptors. In this paper additional hydrodechlorination data are given for Dieldrin, Aldrin, and Toxaphene (chlorinated camphene). Chemistry of Hydrodechlorination PCB. The catalyzed hydrodechlorination reactions to remove chlorine from PCBs proceed one step at a time in a consecutive manner. ØØ represents a biphenyl nucleus substituted with n chlorine atoms 54

~43

32 +H

~21 +H„

00 5 -HC1» 00, -HC1 » 00, -HC1 » 00. -HC1 *

~10 —» 00 1 -HC1 9

00 ο

K i n e t i c s are w e l l represented by a s e r i e s o f successive reactions. I f s i m p l e f i r s t o r d e r r a t e c o n s t a n t s (^ ) a r e calculated r e l a t i v e t o the f i r s t step, a single set o f c o n s t a n t s r e p r e s e n t s t h e d a t a o v e r t h e r a n g e o f 60-130°C at 50 b a r h y d r o g e n p r e s s u r e f o r l i q u i d - p h a s e r e a c t i o n s mn

1

Current address: Mobil Research Corporation, Princeton, Ν J Current address: Institute of Isotopes, Hungarian Academy of Sciences, Budapest, Hungary 2

0-8412-0433-0/78/47^73-024$05.00/0 © 1978 A m e r i c a n C h e m i c a l Society

Kennedy; Disposal and Decontamination of Pesticides ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

3.

KRANICH ET AL.

Polychlorinated Hydrocarbons

25

i n e t h a n o l s o l v e n t w i t h n i c k e l c a t a l y s t ( G i r d l e r G49) and NaOH as a c i d a c c e p t o r . P r o d u c t d i s t r i b u t i o n s b a s e d on k =1, k =0.40, k = 0 . 2 3 , k =0.36, and k =0.40 a r e snown i n F i g u r e 1 superimposée on t h e e x p e r i m e n t a l d a t a . DDT-DDE. I n t h e p r e s e n c e o f sodium h y d r o x i d e i n e t h a n o l s o l v e n t , DDT i s q u i c k l y c o n v e r t e d n o n - c a t a l y t i c a l l y t o DDE. 3 2

C10

- C - 0C1 I

cci Downloaded by IOWA STATE UNIV on March 9, 2017 | http://pubs.acs.org Publication Date: June 30, 1978 | doi: 10.1021/bk-1978-0073.ch003

HC1

¥

(DDT)

3

- >

C10

0C1

- C Μ

cci

2

(DDE)

The subsequent r e a c t i o n s o f DDE a r e more c o m p l e x . They not o n l y i n v o l v e c o n s e c u t i v e a r o m a t i c h y d r o d e c h l o r i n a t i o n but a l s o p a r a l l e l r e a c t i o n s i n which o l e f i n i c c h l o r i n e s a r e removed and t h e a s s o c i a t e d o l e f i n i s s a t u r a t e d w i t h o u t i n t e r m e d i a t e d e s o r p t i o n from the c a t a l y s t . Note i n the f o l l o w i n g r e a c t i o n n e t w o r k t h a t as many as f i v e h y d r o g e n m o l e c u l e s r e a c t i n one s t e p . The numbers shown are f i r s t order r a t e c o n s t a n t s r e l a t i v e t o the t o t a l r a t e o f r e a c t i o n o f DDE by a l l f o u r p a t h s , f o r l i q u i d phase r e a c t i o n w i t h h y d r o g e n a t 50 b a r , N i c a t a l y s t , o v e r t h e temp e r a t u r e r a n g e 20-100°C. These c o n s t a n t s have b e e n used t o c a l c u l a t e t h e p r o d u c t d i s t r i b u t i o n shown i n F i g u r e 2, s u p e r i m p o s e d on t h e e x p e r i m e n t a l d a t a .



DISPOSAL AND DECONTAMINATION OF PESTICIDES

AROCLOR

HYDRODECHLORINATION

Fraction Chlorine Unconverted Figure 1. Product distribution conversion for hydrodechlorination chrl248)

vs. chlorine of PC Β (Aro-



3.

KRANiCH ET AL.

ΡOlychlorinated Hydrocarbons

Figure 2. Product distribution version for hydrodechlorination

vs. chlorine con of DDE (DDT)


27

28



Aldrin-Dieldrin. The s t r u c t u r e s corresponding epoxide D i e l d r i n a r e :

o f A l d r i n and i t s

Dieldrin

Aldrin

E x p e r i m e n t a l d a t a o n r e l a t i v e mole f r a c t i o n o f h y d r o d e c h l o r i n a t i o n p r o d u c t s o f A l d r i n and D i e l d r i n a r e shown i n F i g u r e s 3 and 4. These d a t a a r e f o r l i q u i d phase r e a c t i o n i n e t h a n o l a t 50 b a r h y d r o g e n and 130°C w i t h NaOH as a c i d a c c e p t o r . The c a t a l y s t i s a g a i n n i c k e l ( G i r d l e r G49). Experimental procedures a r e s i m i l a r t o those desc r i b e d f o r DDE (2) and A r o c l o r 1248 ( 3 ) . The d a t a do n o t lend themselves t o simple k i n e t i c a n a l y s i s . For A l d r i n , h y d r o d e c h l o r i n a t i o n appears t o proceed as follows: + H C

H

12 8

C 1

6

C

-HCl

H

12 11

C 1

5

-HCl

C

H

12 12

\+3H

2 2HC1

V

V H

12 15

C 1

4

Y+3H

2 2HC1

C

C 1

C

3

H

12 16

C 1

2

F i r s t an o l e f i n i c group i n A l d r i n hydrogenates (the epoxide i n D i e l d r i n i s not a f f e c t e d a t these c o n d i t i o n s ) i n a step simultaneous w i t h removal o f a h i g h l y a c t i v e geminal d i chloride. The m o l e c u l e t h e n l o s e s i n one s t e p i t s o l e f i n i c c h l o r i n e atoms and h y d r o g e n a t e s t h a t o l e f i n i c bond. F o r D i e l d r i n t h e p r i n c i p a l r e a c t i o n p a t h seems t o b e s i m i l a r b u t s i m p l e r , s i n c e t h e r e i s no o l e f i n i c bond t o hydrogenate. +H C

H

12 8

C 1

6°

+H

2

-HCÏ*

C

H

12 9

C 1

5°

-HCl

C

H

C 1

12 10 4°

The l a s t h i g h l y u n r e a c t i v e c h l o r i n e s t o b e removed a r e t h e a l i p h a t i c c h l o r i n e s , and t h e c o n s e q u e n c e o f t h e i r v e r y l o w r e a c t i v i t y i s t h a t A l d r i n and D i e l d r i n a r e n o t r e a d i l y completely s t r i p p e d t o t h e corresponding hydrocarbon skeletons.


KRANiCH ET AL.


1.0 ι

Polychlorinated Hydrocarbons 1

1

1

1 I I I II

1

Reaction Time

(Min.)

1

1

1—I I I I

Figure 3. Distribution of hydrodechlorination products of Aldrin vs. reaction time

10

too Reaction Time

Figure

4.

ιροο

ιοροο

(Min.)

Distribution of hydrodechlorination Dieldrin vs. reaction time

products of


30

DISPOSAL AND

DECONTAMINATION OF PESTICIDES


Toxaphene. Toxaphene i s a m i x t u r e o f h i g h l y c h l o r i n a t e d d e r i v a t i v e s o f camphene. A t y p i c a l compound w h i c h has been i s o l a t e d from a r e p r e s e n t a t i v e toxaphene m i x t u r e i s a heptachlorobornane. Ci

In h y d r o d e c h l o r i n a t i o n the geminal c h l o r i n e s a r e r e a d i l y a t t a c k e d but the remaining a l i p h a t i c c h l o r i n e s are q u i t e s t a b l e . As w i t h D i e l d r i n and A l d r i n , c o m p l e t e r e moval o f c h l o r i n e f r o m t h e h y d r o c a r b o n s k e l e t o n i s v e r y difficult. E x p e r i m e n t a l r e s u l t s f o r toxaphene h y d r o d e c h l o r i n a t i o n are given i n Table I. TABLE I TOXAPHENE HYDRODECHLORINATION AT 100°C, 50 BAR (4-6 wt % Toxaphene i n E t h a n o l ; lOgm Toxaphene/gm c a t a l y s t ^ N i on K i e s e l g u h r ) R e a c t i o n Time ( h r ) 2 4 19 C h l o r i n e atoms/molecule D i s t r i b u t i o n (%) 0 16.5 32.4 37.2 1 21.4 29.0 25.8 2 29.9 20.3 24.2 3 9.4 2.8 1.2 4 8.5 11.6 10.5 5 5.5 2.0 1.1 6 6.1 1.9 7 1.5 8 1.2 Based on i t s 68% (wt) c h l o r i n e , t h e o r i g i n a l Toxaphene c o n t a i n e d an a v e r a g e o f 7.8 c h l o r i n e atoms p e r m o l e c u l e Hydrodechlorination Process. A process i s proposed b a s e d on t h e l a b o r a t o r y s t u d i e s , w h i c h i s c a p a b l e o f dec h l o r i n a t i n g DDT and PCBs t o any d e s i r e d l e v e l and p a r t i a l l y d e c h l o r i n a t i n g D i e l d r i n , A l d r i n and Toxaphene. A c o n c e p t u a l i z e d f l o w s h e e t i s g i v e n i n F i g u r e 5. The m a t e r i a l s t o be t r e a t e d a r e c h a r g e d as a b a t c h t o a r o t a r y ( t u m b l i n g ) e x t r a c t o r . The o r g a n i c m a t e r i a l s t o be h y d r o d e c h l o r i n a t e d a r e e x t r a c t e d w i t h hot e t h a n o l and pumped t o t h e r e a c t o r . D u r i n g t h e e x t r a c t i o n phase t h e r e a c t o r c o n t e n t s a r e b o i l e d a t a t m o s p h e r i c p r e s s u r e and t h e e t h a n o l i s e v a p o r a t e d , condensed and r e t u r n e d t o t h e e x t r a c t o r u n t i l t h e c o n t a i n e r s and i n e r t m a t e r i a l s r e m a i n i n g i n t h e e x t r a c t o r a r e f r e e o f p e s t i c i d e s . E t h a n o l may be r e c o v e r e d f r o m t h e c l e a n e d s o l i d w a s t e e i t h e r by a f i n a l e x t r a c t i o n w i t h w a t e r o r by h e a t i n g s u f f i c i e n t l y t o


Polychlorinated

Hydrocarbons


KRANICH ET AL.

Figure 5. Hydrodechlorination process flow diagram


31


32


flash i t off. Sodium h y d r o x i d e ( d i s s o l v e d i n e t h a n o l ) i s t h e n added t o t h e r e a c t o r and t h e s y s t e m i s p r e s s u r i z e d w i t h h y d r o g e n . Hydrodechlorination proceeds i n t h e presence o f t h e n i c k e l c a t a l y s t , which i s r e t a i n e d i n t h e r e a c t o r from b a t c h t o batch. NaOH s o l u t i o n i s added a u t o m a t i c a l l y i n r e s p o n s e to decreasing a l k a l i n i t y o f t h e reacting s o l u t i o n . When t h e r e a c t i o n r e a c h e s t h e d e s i r e d d e g r e e o f comp l e t i o n as i n d i c a t e d b y t h e demand f o r NaOH s o l u t i o n , t h e l i q u i d contents a r e s t r a i n e d through t h e c a t a l y s t r e t e n t i o n screen t o t h e solvent recovery s t i l l . Here some o r a l l o f t h e e t h a n o l i s b o i l e d o f f , p u r i f i e d i n a column a s n e c e s s a r y t o remove w a t e r o r o t h e r i m p u r i t i e s and r e t u r n e d t o t h e solvent holding tank. The p r o d u c t s c o n t a i n i n g N a C l and a s l i g h t e x c e s s o f NaOH a r e e x t r a c t e d w i t h w a t e r t o remove t h e s o l u b l e i n o r ganics. Use o r d i s p o s a l o f t h e o r g a n i c p r o d u c t s depends on t h e d e g r e e o f d e c h l o r i n a t i o n , c o m p l e x i t y o f t h e f e e d and p r o d u c t , and t h e u s e f u l n e s s o f t h e p r o d u c t f o r o t h e r p u r p o s e s ( e . g . a s a p l a s t i c i z e r o r c h e m i c a l raw m a t e r i a l ) . Reactor Design. Laboratory r e s u l t s permit estimation o f t h e r e a c t i o n time r e q u i r e d t o reach a g i v e n degree o f c h l o r i n e r e m o v a l and t h e d i s t r i b u t i o n o f p r o d u c t s . F o r r e a c t i o n s a t 100°C, 50 b a r p r e s s u r e , 6 1 % N i o n k i e s e l g u h r c a t a l y s t , 1-6% ( w e i g h t ) r e a c t a n t i n e t h a n o l , 10-40 grams r e a c t a n t p e r gram c a t a l y s t , t h e p e r c e n t a g e o f o r i g i n a l c h l o r i n e r e m a i n i n g as a f u n c t i o n o f t i m e i s g i v e n a p p r o x i m a t e l y b y F i g u r e 6 f o r DDE, PCB ( A r o c l o r 1248) and Toxaphene. D i e l d r i n - A l d r i n d a t a a r e n o t i n c l u d e d , s i n c e t h e i r h y d r o d e c h l o r i n a t i o n s were r u n a t 130°C. A l l o f t h e c u r v e s show r a p i d i n i t i a l r e p l a c e m e n t o f some o f t h e c h l o r i n e b y h y d r o g e n f o l l o w e d b y s l o w e r r e a c t i o n . Since s e v e r a l types o f c h l o r i n e bonding e x i s t , t h e more l a b i l e t y p e s ( a r o m a t i c , o l e f i n i c , g e m i n a l ) a r e attacked before the very s t a b l e a l i p h a t i c c h l o r i n e s . W i t h D i e l d r i n and A l d r i n , i n i t i a l r e a c t i o n o f g e m i n a l c h l o r i n e s i s r a p i d , b u t a l i p h a t i c monochloro bonds a r e o n l y very s l o w l y s u b s t i t u t e d by hydrogen. I f f u r t h e r c h l o r i n e r e m o v a l f r o m t h e s e compounds i s r e q u i r e d ( r a t h e r t h a n s i m p l y t h e r e d u c t i o n i n t o x i c i t y accompanying t h e r a p i d i n i t i a l r e a c t i o n ) , more s e v e r e o p e r a t i n g c o n d i t i o n s w o u l d b e needed. Figure 2 follows i n d e t a i l the intermediate reaction p r o d u c t s c o n t a i n i n g t h e i n d i c a t e d number o f c h l o r i n e atoms per m o l e c u l e as a f u n c t i o n o f t h e f r a c t i o n t o t a l c h l o r i n e removed f r o m DDE. F i g u r e 1 g i v e s t h e same i n f o r m a t i o n f o r A r o c l o r 1248, a t y p i c a l p o l y c h l o r i n a t e d b i p h e n y l . Both o f these s e t s o f curves a r e n e a r l y independent o f temperature. F i g u r e s 1, 2, and 6 c a n be t r e a t e d a s d e s i g n c u r v e s t o meet a v a r i e t y o f p r o c e s s i n g o b j e c t i v e s f o r t h e s e two


Polychlorinated


3. KRANiCH ET AL.

33

\

Ό Φ φ c ο υ c

Hydrocarbons

0.8

Ζ> φ

Ë

0.6

Ο

JC ο ο c

]

!

α» 0.4 Ο Ο c ο

'Ζ 0.2

DDE \

^

Ν 5

TOXAPHEN Ε

I —.^L.

PCB

ι

10

15

20

Reaction Time, Hrs.

Figure 6. Chlorine conversion vs. time (liquidphase hydrodechlorination at 100°C, 50 bar, 16% (wt) in ethanol, 10-40 g reactant/g 61% Ni on kieselguhr catalyst)



34

m a t e r i a l s s u c h a s removal o f a g i v e n f r a c t i o n o f o r i g i n a l c h l o r i n e , c o n v e r s i o n o f a g i v e n f r a c t i o n o f s t a r t i n g mat e r i a l , o r maximizing t h e y i e l d o f a p a r t i c u l a r i n t e r m e d i a t e . Acknowledgement F i n a n c i a l s u p p o r t f o r t h i s s t u d y was p r o v i d e d b y t h e U n i t e d S t a t e s E n v i r o n m e n t a l P r o t e c t i o n Agency under EPA c o n t r a c t R 802-857-01 " C a t a l y t i c C o n v e r s i o n o f H a z a r d o u s and T o x i c C h e m i c a l s " . D r . E. B i r o n h e l p e d i n t h e work.


Abstract A conceptual process i s described for the c a t a l y t i c hydrodechlorination of chlorinated pesticides (e.g. DDT, A l d r i n , D i e l d r i n , and Toxaphene), and other environmentally undesirable compounds (e.g. polychlorinated biphenyls, PCB). Experimental studies show that chlorines can i n general be c a t a l y t i c a l l y replaced by hydrogen to any desired extent. Products are generally high boiling o i l s which may be use ful or readily burned. Reaction models are proposed and relative rate con stants determined for several hydrodechlorinations. In general, o l e f i n i c and aromatic chlorines are more easily removed than aliphatic chlorines. Highly bridged, non -planar molecules l i k e Dieldrin and A l d r i n are very d i f f i c u l t to hydrodechlorinate completely.

Literature Cited 1) LaPierre, R.B., Wu, D., Kranich, W.L., and Weiss, A.H. J . Catal., (1978), (In Press) 2) LaPierre, R.B., Guczi, L., Kranich, W.L., and Weiss, A.H., J . Catal. (1978), (Paper on DDE - In Press) 3) LaPierre, R.B., Guczi, L., Kranich, W.L., and Weiss, A.H., J . Catal. (1978), (Paper on PCB - In Press) See Also: LaPierre, R.B., Biron, Ε., Wu, D., Guczi, L., Kranich, W.L., and Weiss, A.H., "Catalytic Conversion of Hazardous and Toxic Chemicals: Pesticides and Related Substances," Document No. PB 262 804, EPA600/3-77-018, January 1977. National Technical In formation Service, U.S. Department of Commerce, 5285 Port Royal Road, Springfield, Va. See also "Catalytic Hydrodechlorination of Polychlorinated Pesticides and Related Substances: An Executive Summary," EPA-600/ 8-77-013, September 1977. MARCH 23, 1978



34

m a t e r i a l s s u c h a s removal o f a g i v e n f r a c t i o n o f o r i g i n a l c h l o r i n e , c o n v e r s i o n o f a g i v e n f r a c t i o n o f s t a r t i n g mat e r i a l , o r maximizing t h e y i e l d o f a p a r t i c u l a r i n t e r m e d i a t e . Acknowledgement F i n a n c i a l s u p p o r t f o r t h i s s t u d y was p r o v i d e d b y t h e U n i t e d S t a t e s E n v i r o n m e n t a l P r o t e c t i o n Agency under EPA c o n t r a c t R 802-857-01 " C a t a l y t i c C o n v e r s i o n o f H a z a r d o u s and T o x i c C h e m i c a l s " . D r . E. B i r o n h e l p e d i n t h e work.


Abstract A conceptual process i s described for the c a t a l y t i c hydrodechlorination of chlorinated pesticides (e.g. DDT, A l d r i n , D i e l d r i n , and Toxaphene), and other environmentally undesirable compounds (e.g. polychlorinated biphenyls, PCB). Experimental studies show that chlorines can i n general be c a t a l y t i c a l l y replaced by hydrogen to any desired extent. Products are generally high boiling o i l s which may be use ful or readily burned. Reaction models are proposed and relative rate con stants determined for several hydrodechlorinations. In general, o l e f i n i c and aromatic chlorines are more easily removed than aliphatic chlorines. Highly bridged, non -planar molecules l i k e Dieldrin and A l d r i n are very d i f f i c u l t to hydrodechlorinate completely.

Literature Cited 1) LaPierre, R.B., Wu, D., Kranich, W.L., and Weiss, A.H. J . Catal., (1978), (In Press) 2) LaPierre, R.B., Guczi, L., Kranich, W.L., and Weiss, A.H., J . Catal. (1978), (Paper on DDE - In Press) 3) LaPierre, R.B., Guczi, L., Kranich, W.L., and Weiss, A.H., J . Catal. (1978), (Paper on PCB - In Press) See Also: LaPierre, R.B., Biron, Ε., Wu, D., Guczi, L., Kranich, W.L., and Weiss, A.H., "Catalytic Conversion of Hazardous and Toxic Chemicals: Pesticides and Related Substances," Document No. PB 262 804, EPA600/3-77-018, January 1977. National Technical In formation Service, U.S. Department of Commerce, 5285 Port Royal Road, Springfield, Va. See also "Catalytic Hydrodechlorination of Polychlorinated Pesticides and Related Substances: An Executive Summary," EPA-600/ 8-77-013, September 1977. MARCH 23, 1978


Catalytic Hydrodechlorination of Polychlorinated Hydrocarbons - ACS

Recommend Documents