Gel Permeation Chromatographic Behavior of Metalloporphyrins from

C h a p t e r 22 Gel of

Permeation Metalloporphyrins

Chromatographic from

a

Rock

Behavior Extract

G. Šebor

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on March 8, 2016 | http://pubs.acs.org Publication Date: July 6, 1987 | doi: 10.1021/bk-1987-0344.ch022

Department of Petroleum Technology and Petrochemistry, Institute of Chemical Technology, 166 28 Prague 6, Czechoslovakia

The number of carbon atoms present in the porphine substituents and mainly the d i f f e r e n t geometry of n i c k e l and vanadyl ions i n the molecule of metalloporphyrins were found to be the main factors i n fluencing the GPC separation of these e t i o and deoxophylloerythroetio type complexes. This chromatographic technique provided an e f f e c t i v e separation of n i c k e l from vanadyl porphyrins present i n a rock extract from the vicinity of petroleum dep o s i t i n the Persian Gulf area. Both met a l l o p o r p h y r i n s were i s o l a t e d by the comb i n a t i o n of adsorption chromatography on silica gel and GPC on s t y r e n e - d i v i n y l b e n zene copolymer. In order to study the GPC behavior of these complexes, GPC f r a c t i o n s were c o l l e c t e d and and analyzed by mass spectrometry. For many y e a r s a l r e a d y , c o n s i d e r a b l e a t t e n t i o n has b e e n p a i d t o t h e c h a r a c t e r o f n i c k e l and v a n a d y l p e t r o p o r p h y r i n s found i n f o s s i l f u e l s and b o t h a n c i e n t and r e c e n t sediments. The knowledge o f t h e type o f p e t r o p o r p h y r i n s found i n f o s s i l f u e l s i s s i g n i f i c a n t b o t h f o r g e o c h e m i c a l c o r r e l a t i o n s and f o r t h e s t u d y o f t h e b e h a v i o r o f b o t h types of the r e l e v a n t m e t a l l o p o r p h y r i n s d u r i n g f o s s i l fuels processing. An e f f e c t i v e s e p a r a t i o n o f p e t r o p o r p h y r i n s from t h e sample i s a n e c e s s a r y p r e r e q u i s i t e f o r t h e i r d e t a i l e d characterization. The methods used f o r t h e s e p a r a t i o n o f p e t r o p o r p h y r i n s may be d i v i d e d i n t o two b a s i c g r o u p s , v i z . e x t r a c t i o n methods and c h r o m a t o g r a p h i c methods. An a p p r o p r i a t e c o m b i n a t i o n o f b o t h t y p e s o f methods i s a l s o applied very f r e q u e n t l y . Numerous o r g a n i c s o l v e n t s and b o t h o r g a n i c and m i n e r a l a c i d s have been used as e x t r a c t i o n r e a g e n t s (J_). I t i s e s p e c i a l l y the e x t r a c t i o n

0097-6156/87/0344-0350$06.00/0 © 1987 American Chemical Society

Filby and Branthaver; Metal Complexes in Fossil Fuels ACS Symposium Series; American Chemical Society: Washington, DC, 1987.


22.

SEBOR

Gel Permeation Chromatographic Behavior of Metalloporphyrins

351

of p e t r o p o r p h y r i n s w i t h an a c i d , w h i c h s t a r t s as a demet a l a t i o n o f the m e t a l l o p o r p h y r i n s p r e s e n t , and i s f r e q u e n t l y used as the f i r s t s t e p i n the i s o l a t i o n o f the r e l e v a n t compounds (2_) . T h e r e i s a d i s a d v a n t a g e however, i n t h a t changes i n the o r i g i n a l s t r u c t u r e o f the com pounds may o c c u r d u r i n g d e m e t a l a t i o n and the s u b s e q u e n t e x t r a c t i o n of f r e e p o r p h y r i n s ( 3_~6_) . The b a s i c a s s u m p t i o n made i s t h a t e v e r y compound decomposes to the same e x t e n t , e.g. the r e l a t i v e amounts of the v a r i o u s compounds p r e s e n t a r e unchanged a f t e r d e m e t a l a t i o n (2). In the f i e l d o f c h r o m a t o g r a p h i c methods, h i g h - p e r formance l i q u i d c h r o m a t o g r a p h y has r e c e n t l y been c o n s i d e r e d an e x t r e m e l y p r o m i s i n g t e c h n i q u e (7_~J_2 ) . This chromatographic t e c h n i q u e e n a b l e s s e p a r a t i o n of homolo gous s e r i e s and t y p e s o f m e t a l l o p o r p h y r i n s as w e l l as s t r u c t u r a l i s o m e r s ( j j O . W i t h the e x c e p t i o n of i o n - e x change c h r o m a t o g r a p h y , o t h e r l i q u i d c h r o m a t o g r a p h y t e c h n i q u e s have been employed f o r p e t r o p o r p h y r i n s s e p a r a t i o n s , v i z . a d s o r p t i o n column c h r o m a t o g r a p h y , t h i n l a y e r c h r o m a t o g r a p h y , p a p e r c h r o m a t o g r a p h y , and g e l permeation chromatography (2). The l a s t method has been used by some a u t h o r s f o r s e p a r a t i o n of n i c k e l and v a n a d y l p o r p h y r i n s ( J_3^, Jj_4_ ) . To d a t e however the mechanism o f GPC s e p a r a t i o n of t h e s e compounds has not been d i s c u s s e d i n a d e t a i l e d manner. In the p r e s e n t p a p e r , the c h a r a c t e r i s t i c s o f n i c k e l and v a n a d y l p o r p h y r i n s , found i n the r o c k e x t r a c t o b t a i n e d i n the v i c i n i t y of c r u d e o i l d e p o s i t s , a r e presented. The r e l e v a n t m e t a l l o p o r p h y r i n s have been s e p a r a t e d by a c o m b i n a t i o n o f a d s o r p t i o n c h r o m a t o g r a p h y on s i l i c a g e l and GPC on a s t y r e n e - d i v i n y l b e n z e n e c o p o lymer. Gel permeation chromatographic b e h a v i o r of n i c k e l and v a n a d y l m e t a l l o p o r p h y r i n s has been s t u d i e d i n a d e t a i l e d manner. Experimental Sample P r e p a r a t i o n . D r i l l i n g s were made to a d e p t h of 6 m i n the v i c i n i t y of c r u d e o i l d e p o s i t s i n the P e r s i a n Gulf area. The r o c k e x t r a c t s o b t a i n e d from the b o r e h o l e were c r u s h e d ; 450 g were e x t r a c t e d w i t h benzene i n a S o x h l e t e x t r a c t o r and the e x t r a c t s were w e i g h e d . The y i e l d s of e x t r a c t a b l e mass were w i t h i n the range of 0.1-15 wt%, u s u a l l y about 0.15 wt% . E x t r a c t samples marked KB6a, KB7a, and KB9b were s u p p l i e d by P r o f e s s o r W. D. Gill. The o r i g i n a l e x t r a c t s were c h a r a c t e r i z e d by means of t h e i r c o n t e n t of n i c k e l , vanadium, and m e t a l l o p o r p h y r i n s ; the r e s u l t s have been p u b l i s h e d p r e v i o u s l y (j_5_) . F o r the p r e s e n t s t u d y , the KB6a sample has been chosen. A d s o r p t i o n Chromatography. A d s o r p t i o n chromatography of the e x t r a c t was c a r r i e d out on a g l a s s column C60 cm χ 8 mm i . d . ) p a c k e d w i t h s i l i c a g e l (Woelm Eschwege)


METAL COMPLEXES IN FOSSIL FUELS

352


d e a c t i v a t e d by a d d i t i o n o f 3 wt% w a t e r . Saturated hydro c a r b o n s and a r o m a t i c s were e l u t e d w i t h 50% e t h e r i n pentane. The m e t a l l o p o r p h y r i n s were e l u t e d w i t h e t h e r . The e l u e n t was d e l i v e r e d w i t h a MC 300_micropump ( M i c r o t e c h n a , P r a g u e ) a t a f l o w r a t e o f 1 mL min and m o n i t o r e d w i t h a UV-VIS d e t e c t o r (KNAUER) f o r q u a n t i t a t i v e i s o l a t i o n of metalloporphyrins. The d e t e c t o r was s e t a t 400 nm. Gel Permeation Chromatography. Gel permeation chromato g r a p h y of the m e t a l l o p o r p h y r i n s c o n c e n t r a t e was performed on a g l a s s column (150 cm χ 14 mm i . d . ) p a c k e d w i t h a s t y r e n e - d i v i n y l b e n z e n e c o p o l y m e r c o n t a i n i n g 3 wt% o f d i v i n y l b e n z e n e C t h e g e l was p r e p a r e d at the I n s t i t u t e o f Macromolecular C h e m i s t r y , C z e c h o s l o v a k Academy o f S c i e n ces, Prague). The g e l was c h a r a c t e r i z e d by p a r t i c l e s i z e of 40-120 ,um and an e x c l u s i o n l i m i t of about 2000. It was s w e l l e d i n a methano1-benzene m i x t u r e c o n t a i n i n g 10% methanol. The column was c l o s e d a t b o t h ends w i t h b r a s s s t o p p e r s e q u i p p e d w i t h T e f l o n s e a l s , and the g e l was f i x e d on b o t h ends by a g l a s s wool l a y e r . The m e t h a n o l -benzene m o b i l e phase was d e l i v e r e d by means o f a d e v i c e w o r k i n g on_îjIar i o 11 i s p r i n c i p l e ; a c o n s t a n t f l o w r a t e of 1.5 mL min was m a i n t a i n e d . A s i x way s t o p cock w i t h a s a m p l i n g l o o p was used f o r the i n j e c t i o n o f the m e t a l l o p o r p h y r i n s c o n c e n t r a t e p r e p a r e d by a d s o r p t i o n c h r o m a t o graphy. The e l u e n t was c o n s t a n t l y m o n i t o r e d w i t h a UV-VIS d e t e c t o r (KNAUER) s e t at 550 and 572 nm, respectively . -

Mass S p e c t r o m e t r y . Mass s p e c t r a were r e c o r d e d on an A . E . I . MS 902 s p e c t r o m e t e r at an i o n i z a t i o n e n e r g y o f 70 eV. The samples were i n t r o d u c e d by means o f a d i r e c t i n s e r t i o n probe. The mass s c a l e was c a l i b r a t e d w i t h the use of p e r f l u o r o t r i b u t y l a m i n e . S p e c t r a were measured w i t h a r e s o l u t i o n o f 3000 on a 10% v a l l e y . Results

and

Discussion

By means of a d s o r p t i o n c h r o m a t o g r a p h y of the r o c k e x t r a c t , about 100 mg o f a c o n c e n t r a t e o f n i c k e l and v a n a d y l p o r p h y r i n s was o b t a i n e d . The c o u r s e o f GPC a n a l y s i s o f the c o n c e n t r a t e i s shown i n F i g u r e 1. It i s evident that g e l c h r o m a t o g r a p h y r e s u l t e d i n an e f f e c t i v e s e p a r a t i o n o f n i c k e l and v a n a d y l p o r p h y r i n s p r e s e n t i n the above mentioned c o n c e n t r a t e . The f a c t t h a t v a n a d y l p o r p h y r i n s are e l u t e d from the column e a r l i e r t h a n n i c k e l p o r p h y r i n s means t h a t the s e p a r a t i o n of b o t h m e t a l l o p o r p h y r i n s i s p r o b a b l y c o n t r o l l e d by the s t e r i c f a c t o r to a c o n s i d e r a b l e d e g r e e . The c o o r d i n a t i o n s p h e r e geometry o f n i c k e l p o r p h y r i n s i s p l a n a r , the n i c k e l atom b e i n g l o c a t e d i n the p l a n e formed by the n i t r o g e n atoms of the f o u r p y r r o l e r i n g s t h a t form the b a s i c p o r p h y r i n s k e l e t o n . Vanadyl p o r p h y r i n s are complex compounds w i t h t e t r a g o n a l p y r a m i d a l g e o m e t r y ,


22.


SEBOR

Fractions


1 τ

I

100

2 1

3 1

4 1

5 1

6 ι

1

150

7 1

Γ

ι

I

200 Elution

250 volume

(mL)

F i g u r e 1. Chromatogram of m e t a l l o p o r p h y r i n s i s o l a t e d from a r o c k sample on s t y r e n e - d i v i n y l b e n z e n e c o p o l y m e r ( a - t h e e l u t i o n c u r v e of v a n a d y l p o r p h y r i n s , b - t h e e l u t i o n c u r v e of n i c k e l p o r p h y r i n s )


353


354


w i t h the oxygen atom o c c u p y i n g the apex of the p y r a m i d and the v a n a d y l group l y i n g o u t s i d e the p l a n e formed by the f o u r n i t r o g e n atoms. A l s o , i t may be d e r i v e d from the c o u r s e o f e l u t i o n o f b o t h m e t a l l o p o r p h y r i n s o b s e r v e d t h a t the a n a l y z e d c o n c e n t r a t e of m e t a l l o p o r p h y r i n s i s a complex m i x t u r e of the r e l e v a n t compounds. In o r d e r to s t u d y the GPC b e h a v i o r of b o t h t y p e s of m e t a l l o p o r p h y r i n s on the s t y r e n e - d i v i n y l b e n z e n e c o p o l y m e r , s e v e n f r a c t i o n s were c o l l e c t e d C s e e F i g u r e 1] and a n a l y zed by mass s p e c t r o m e t r y . T a b l e s I and I I p r e s e n t a summary of the mass s p e c t r o m e t r i c d a t a o b t a i n e d . In f r a c t i o n s 1, 2, and 3, the f o l l o w i n g i o n s have been i d e n t i f i e d ( s e e T a b l e I ) : i o n s of the homologous s e r i e s of v a n a d y l p o r p h y r i n s o f the e t i o t y p e (M=375+14n, where η i s an i n t e g e r ) , and i o n s of the homologous s e r i e s of v a n a d y l p o r p h y r i n s of the d e o x o p h y l l o e r y t h r o e t i o t y p e (the mass of w h i c h i s M=373+14m, where m i s an i n t e g e r £ 2). With r e s p e c t to the i d e n t i f i e d members of homolo gous s e r i e s of b o t h t y p e s of v a n a d y l p o r p h y r i n s i n GPC f r a c t i o n s ( T a b l e I ) , i t may be d e m o n s t r a t e d t h a t GPC b e h a v i o r of t h e s e compounds i s a f f e c t e d by the m o l e c u l a r sieve e f f e c t , i . e . , t h e i r separation c o r r e l a t e s roughly w i t h the number of c a r b o n atoms i n t h e i r p o r p h i n e substituents. In f r a c t i o n no. 4, two s e r i e s of i o n s have been i d e n t i f i e d : M =371+14n, M =379+14n; f o r b o t h s e r i e s , η l i e s i n the range of 7-11. From the t h e o r e t i c a l p o i n t of v i e w , any of the f o l l o w i n g s t r u c t u r e s may be a s c r i b e d (16) to the M.j s e r i e s of mass l i n e s : p o r p h i n e d e r i v a t i v e s w i t h two i s o c y c l i c r i n g s i n t h e i r m o l e c u l e s (12)» c h l o r i n s w i t h one b enzo s ub s t i t uent on p y r r o l e i n f>, (> p o s i t i o n (Η Β ^ ) , c h l o r i n s w i t h t h r e e i s o c y c l i c r i n g s ( H J I ^ ) , or p o r p h y r i n s w i t h t h r e e b e n z o s u b s t i t u e n t s on p y r r o l e r i n g s i n f>, β' p o s i t i o n s (Ββ)· case of the s e r i e s of mass l i n e s , the f o l l o w i n g s t r u c t u r e s may be c o n s i d e r e d (j_6): c h l o r i n s i n w h i c h the (>, f! d o u b l e bond on a n o t h e r p y r r o l e i s a l s o h y d r o g e n a t e d , i . e . tetrahydroporphyrins ( l ^ ) , hexahydroporphyrins w i t h one i s o c y c l i c r i n g ( H ^ I j ) , p o r p h y r i n s w i t h two i s o c y c l i c r i n g s and one b e n z o - s u b s t i t u e n t (B 1 ^ ) , or t e t r a b e n z o p o r p h y r i n s ( B , ) . E x a c t mass measurements have not been c a r r i e d o u t . A d e t a i l e d a n a l y s i s of f r a c t i o n 4 was beyond the s c o p e of the p r e s e n t s t u d y . 1

I

n

F r a c t i o n s 5, 6, and 7 c o n t a i n e d n i c k e l p o r p h y r i n s . As i n the c a s e of v a n a d y l p o r p h y r i n a n a l y s i s , members of the homologous s e r i e s of DPEP and e t i o p o r p h y r i n s have been i d e n t i f i e d i n t h e s e f r a c t i o n s ( s e e T a b l e I I ) . In t h i s c a s e , the e v a l u a t i o n of mass s p e c t r a o b t a i n e d i s somewhat more c o m p l i c a t e d due to the f a c t t h a t n i c k e l has several natural isotopes ( N i 67.88%; N i , 26.23%; N i , 1.19%; N i , 3.66%; and N i , 1.08%). The e v a l u a t e d i n t e n s i t i e s may be used f o r d e t e r m i n a t i o n of Ι^_,_ 60 . i n t e n s i t i e s as f o l l o w s : DPEP Ni 26.23 DPEP °Ni DPEP Ni 67 .88 b Z

η

6 4

Λ7

I

6

= I

5 8



detected

Data

Spectrometric

atoms s u b s t i t u t e d on

porphine

from

GPC

f r o m GPC

DPEP r a n g e Maximum Molecular nC Molecular nC ions ion 574-504 15-10 518 1 1 546-476 13- 8 490 9 518-434 11-5 462 4

F r a c t i o n s Trapped

DPEP r a n g e Maximum Molecular nC Mo 1 e c u l a r nC ions ion 639-541 19-12 541 1 2 597-485 16- 8 10 513 555-457 13- 6 485 8 n.d.

P o r p h y r i n s F r a c t i o n s Trapped

f o r Nickel Porphyrins

Maximum M o l e c u l a r nC ion 520 1 1 492 9 464 7

Data

porphine

Maximum M o l e c u l a r nC ion 543 1 2 515 10 487 8

f o r Vanadyl

atoms s u b s t i t u t e d on

E t i o range^ Molecular nC ions 576-506 15-10 548-478 13- 8 520-436 11-5

Mass

of carbon

Figure 1

number

see

5 6 7

3

Table I I .

not

Spectrometric

E t i o range^ Molecular nC ions 641-543 19-12 599-487 16- 8 557-459 13- 6 η .d.

Mass

number o f c a r b o n

Fractions

a

3

I.

see F i g u r e 1

1 2 3 4

Fractions

Table



356

I t i s a l s o p o s s i b l e to i d e n t i f y i n the s p e c t r a a s e r i e s of i o n s f o r w h i c h M= 366+1 4m. T h e i r i n t e n s i t i e s may be e x p r e s s e d as


1=1

DPEP

6C\ .+I · 58 . Ni etio Ni 7

XT

Consequently, I . may be o b t a i n e d v i a s u b t r a c t i o n from I. As seen from èfie mass s p e c t r o m e t r i e d a t a shown i n T a b l e I I , the GPC b e h a v i o r of n i c k e l p o r p h y r i n s i s a l s o a f f e c t e d by the m o l e c u l a r s i e v e e f f e c t . On the b a s i s of the c o u r s e of e l u t i o n o b s e r v e d f o r n i c k e l and v a n a d y l p o r p h y r i n s ( F i g u r e 1) and mass s p e c t r o m e t r i c d a t a ( T a b l e s I and I I ) , the f o l l o w i n g c o n c l u s i o n s are d e r i v e d : The p r i m a r y f a c t o r a f f e c t i n g GPC b e h a v i o r of b o t h m e t a l l o p o r p h y r i n s i s the geometry of the n i c k e l i o n or the v a n a d y l i o n i n the m é t a l l o porphyrin molecule. To a l e s s e r e x t e n t , t h i s b e h a v i o r a l s o depends upon the number of c a r b o n atoms i n p o r p h i n e sub s t i t u e n t s . These c o n c l u s i o n s a r e c o n f i r m e d by the f a c t t h a t , i n f r a c t i o n no. 3 f o r example ( e l u t i o n volume 141-164 mL), v a n a d y l p o r p h y r i n s w i t h the f o l l o w i n g v a l u e s of m o l e c u l a r mass have been i d e n t i f i e d : 457, 459, 471, 473, 485, and 487. On the o t h e r hand, i n f r a c t i o n 6, w i t h a h i g h e r e l u t i o n volume (175-200 mL), n i c k e l p o r p h y r i n s of m o l e c u l a r mass between 504 and 576 have been i d e n t i f i e d . Gel permeation chromatography enables e f f e c t i v e s e p a r a t i o n s of n i c k e l and v a n a d y l p o r p h y r i n s . Its a p p l i c a t i o n i s a d v a n t a g e o u s p a r t i c u l a r l y as the f i r s t step i n q u a n t i t a t i v e i s o l a t i o n of m e t a l l o p o r p h y r i n s found i n a s p h a l t e n e s from v a r i o u s t y p e s of f o s s i l f u e l s . In c o n t r a s t to the commonly a p p l i e d e x t r a c t i o n of m e t a l l o p o r p h y r i n s w i t h an a c i d , GPC s e p a r a t i o n of the r e l e v a n t compounds i s n o n - d e s t r u c t i v e and e n a b l e s to o b t a i n a r e p r e s e n t a t i v e c o n c e n t r a t e of m e t a l l o p o r p h y r i n s p r e s e n t i n an a n a l y z e d sample. Acknowledgments I would l i k e to thank P r o f e s s o r W. D. G i l l , I m p e r i a l C o l l e g e , London f o r p r o v i d i n g the r o c k e x t r a c t s t u d i e d and Dr. V. K u b e l k a , Department of Mass S p e c t r o m e t r y , I n s t i t u t e of C h e m i c a l T e c h n o l o g y , P r a g u e f o r m e a s u r i n g the mass s p e c t r a . Literature Cited 1.

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B a k e r , E. W. i n " O r g a n i c G e o c h e m i s t r y " ; Eglinton, G.; Murphy, M. T. J . , E d s . ; S p r i n g e r - V e r l a g : Berlin- H e i d e l b e r g - N e w Y o r k , 1969; p. 464. Š e b o r , G.; W e i s s e r , O.; Novák, M. Chem. listy 1979, 73, 23. Howe, W. W.; B l u m e r , M. A n a l . Chem. 1961, 33, 1288. M i l l s o n , M. F.; Montgomery, D. S.; Brown, S. R. Geochim. Cosmochim. A c t a 1966, 30, 207.


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Gel Permeation Chromatographic Behavior of Metalloporphyrins from

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