Nickel and Vanadium

14 Nickel and Vanadium

Downloaded by UNIV OF ARIZONA on June 9, 2014 | http://pubs.acs.org Publication Date: June 1, 1976 | doi: 10.1021/ba-1976-0156.ch014

Up

to several thousand parts per million of nickel and vanadium may be present i n crude petroleum as metal porphyrin and other complexes. Although most of it i n a crude oil remains i n the residual fractions and coke during refining, minute quantities have been observed i n distillate fractions (1). Since nickel and vanadium are the most widely analyzed trace metals i n petroleum, the Project addressed itself only to the sub part-per-million levels. Available Analytical Methods. The most commonly used colorimetric reagent for nickel—dimethylglyoxime—can be used to measure levels of nickel as low as 20 ppb after appropriate preconcentration (2). F o r vanadium, hematoxylin (3) and PAR-zephiramine (4) are sensitive colorimetric reagents that can be used to measure as little as 0.1 and 0.015 ppm, respectively. However, a number of elements interfere, and they must be removed prior to measurement. X-ray fluorescence spectroscopy has been used to determine 50 ppb of nickel and vanadium after they have been concentrated on ion exchange resins (5, 6). Emission spectroscopy has been used but is only semiquantitative at the nanogram/gram levels of interest to the Project. Nevertheless, the technique may be useful as a screening tool. T w o relatively new instrumental techniques—spark source mass spectrometry (7) and kinetics of metal-catalyzed reactions (8)—can measure extremely low levels of nickel and vanadium, but they have not been utilized to any appreciable extent. F l a m e a t o m i c a b s o r p t i o n is sensitive e n o u g h t o measure p a r t - p e r b i l l i o n levels of n i c k e l i n aqueous s o l u t i o n , b u t i t is n o t t h a t sensitive f o r vanadium.

H e a t e d vaporization atomic absorption

is m o r e

sensitive,

p e r m i t t i n g d e t e c t i o n o f v a n a d i u m d o w n to 2 0 n g / m l i n aqueous s o l u t i o n . T h e r e f o r e , f o r the p r a c t i c a l q u a n t i t a t i v e d e t e r m i n a t i o n of n a n o g r a m / g r a m concentrations of b o t h n i c k e l a n d v a n a d i u m i n p e t r o l e u m , t h e c o m b i n a t i o n of H V A A

w i t h a preconcentration

a s h i n g step w a s selected f o r

detailed study. Role of Neutron Activation. T h e r m a l n e u t r o n a c t i v a t i o n does n o t p r o d u c e a s u i t a b l e g a m m a - e m i t t i n g isotope f o r m e a s u r i n g n a n o g r a m / g r a m levels of n i c k e l . F o r v a n a d i u m , t h e

5 1

V (n/y)

5 2

V reaction, producing a

1 4 3 4 - K e V g a m m a - r a y p e a k , m a y b e u s e d t o measure 10 n g V / g a n d is n o t subject to a n y interferences.

H o w e v e r , t h e h a l f - l i f e of t h e

5 2

V isotope is

160

In Analysis of Petroleum for Trace Metals; Hofstader, R., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1976.

Nickel

HOFSTADER E T A L .

14.

and

161

Vanadium

o n l y 3.8 m i n , so t h a t p n e u m a t i c s a m p l e transfer f r o m t h e r e a c t o r core to t h e c o u n t i n g f a c i l i t i e s is essential. Special Analytical Considerations.

L o s s of n i c k e l a n d v a n a d i u m

w h e n p e t r o l e u m samples are d r y a s h e d is w e l l k n o w n . occur if the H V A A fractions (9).

Similar

losses

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

Losses of this t y p e are p a r t i c u l a r l y serious w i t h the d i s t i l

late m a t e r i a l s s t u d i e d b y t h e P r o j e c t s i n c e t h e v o l a t i l e p o r p h y r i n s are f o u n d i n these fractions. S u l f u r i c a c i d has b e e n r e c o m m e n d e d as a s u i t a b l e d e c o m p o s i t i o n p r o c e d u r e f o r samples c o n t a i n i n g v o l a t i l e n i c k e l a n d v a n a d i u m , a n d this a p p r o a c h w a s i n v e s t i g a t e d . H o w e v e r , other

decom


p o s i t i o n p r o c e d u r e s d e s i g n e d t o p r e v e n t loss of n i c k e l or v a n a d i u m , i n w h i c h the s a m p l e is h e a t e d w i t h either b e n z e n e s u l f o n i c a c i d (10) (11)

9

or sulfur

w e r e not i n v e s t i g a t e d .

A l t h o u g h n o c o n t a m i n a t i o n f r o m a p p a r a t u s o r reagents w a s

found

f o r v a n a d i u m , s e v e r a l sources of c o n t a m i n a t i o n w e r e e n c o u n t e r e d nickel.

H i g h p u r i t y s u l f u r i c a c i d c o n t a i n e d 4-5

for

n g N i / m l w h i l e the

h y d r o c h l o r i c a c i d d i d n o t c o n t a i n a n y m e a s u r a b l e a m o u n t . V y c o r dishes w h i c h h a d b e e n u s e d p r e v i o u s l y r e t a i n e d traces of n i c k e l t h a t w e r e signifi cant w h e n nanogram quantities were

being determined.

Even

after

t h o r o u g h w a s h i n g , s u c h dishes c o u l d n o t b e u s e d c o n f i d e n t l y . N e w glass w a r e s h o u l d b e u s e d a n d p r e f e r a b l y d e d i c a t e d e x c l u s i v e l y f o r the tests at this l e v e l . N e w vessels m u s t b e c l e a n e d c a r e f u l l y b e f o r e use. T h e d a t a i n T a b l e 14.1 s h o w t h e n i c k e l c o n t a m i n a t i o n r e s u l t i n g f r o m t w o n e w dishes Table 14.1. N i c k e l i n Solution after Successive A c i d Washing of 800-ml V y c o r Dishes Nickel Treatment (1) (2) (3) (4) (5)

a

6

10 m l 1:1 HC1 o n l y 5 m l cone. H S 0 + 10 m l 1:1 HC1 (1) F i r s t repeat of (2) Second repeat of (2) T h i r d repeat of (2) 2

4

Content

(ng)

Dish 1

Dish 2

157 74

92 55

34 23 29

19 24 24

" B o i l e d , evaporated to dryness o n the steam b a t h , a n d the residue t a k e n u p i n 10 m l 1:19 H C 1 . T a k e n to fumes of cone. H 2 S O 4 , 1 : 1 H C 1 added, t h e n t r e a t m e n t (1). 6

t h a t h a d b e e n p r e v i o u s l y u s e d o n c e to d e c o m p o s e samples c o n t a i n i n g p a r t - p e r - m i l l i o n levels of n i c k e l . T h e n i c k e l c o n t a m i n a t i o n w a s e l i m i n a t e d o n l y after several 5 - m l p o r t i o n s of c o n c e n t r a t e d s u l f u r i c a c i d w e r e t a k e n d o w n to fumes i n the d i s h ; the 20-30 n g of r e m a i n i n g n i c k e l r e p r e s e n t e d the reagent b l a n k .


162

ANALYSIS O F P E T R O L E U M

FOR TRACE

METALS

T o test t h e t r e a t i n g p r o c e d u r e , s e v e r a l fuels w e r e a n a l y z e d f o r n i c k e l b y our recommended method, using both (1) treated a n d (2)

washed

b u t u n t r e a t e d V y c o r dishes. T h e results, w h i c h are c o m p a r e d i n T a b l e 14.11, s h o w t h a t c o n t a m i n a t i o n is e l i m i n a t e d b y t h e consecutive

fumings

w i t h the acid. Table 14.11.

Nickel in Fuels by H V A A Nickel Concentration


Untreated

Vycor

(ng/g)

Treated

Vycor

Sample Gasoline Jet Fuel N o . 2 heating o i l Sample Preparation. T h e p r o c e d u r e d e s c r i b e d b y M i l n e r et a l . ( 1 2 ) , based on wet ashing w i t h sulfuric acid a n d incineration i n a V y c o r dish, w a s a d o p t e d w i t h o u t m o d i f i c a t i o n f o r t h e d e c o m p o s i t i o n of m i d d l e a n d h e a v y distillates. F o r l i g h t distillates (i.e., gasolines) t h e d e c o m p o s i t i o n t i m e was shortened considerably b y evaporating the sample i n a stream o f n i t r o g e n after t h e s u l f u r i c a c i d a d d i t i o n b u t b e f o r e t h e i n c i n e r a t i o n . Measurement.

Optimum H V A A

parameters w e r e e s t a b l i s h e d e m

p i r i c a l l y f o r s t a n d a r d d i l u t e h y d r o c h l o r i c a c i d solutions of t h e metals. T h e heat r e t a i n e d b y t h e t u b e f u r n a c e b e t w e e n cycles affects t h e repeata b i l i t y of successive injections. A l t h o u g h injections w e r e m a d e o n a fixed t i m e schedule, m u l t i p l e injections w e r e u s u a l l y necessary t o o b t a i n r e l i able readings. I t is i m p o r t a n t t o e s t a b l i s h t h a t t h e a s h c y c l e settings u s e d d o n o t cause loss of n i c k e l b y p r e m a t u r e v o l a t i l i z a t i o n . C a m p b e l l a n d O t t a w a y (13)

r e p o r t e d t h a t w h e n aqueous n i c k e l sulfate solutions w e r e i n j e c t e d ,

12-26%

of t h e n i c k e l w a s lost at a n a s h i n g t e m p e r a t u r e of 7 5 0 ° C f o r

300 sec. A t t h e p o w e r a n d t i m e settings u s e d i n t h e Project, i t w a s demonstrated that no metal was v o l a t i l i z e d prematurely. T h e existence of b a c k g r o u n d ( n o n - a t o m i c )

a b s o r p t i o n at t h e a n a l y t i

c a l w a v e l e n g t h s f o r N i (232.0 n m ) a n d V (318.5 n m ) w a s i n v e s t i g a t e d using a hydrogen c o n t i n u u m lamp. U n d e r the conditions used, the back g r o u n d signals f o r t h e samples w e r e i n d i s t i n g u i s h a b l e f r o m t h e b a s e l i n e . C o n s e q u e n t l y , n o b a c k g r o u n d c o r r e c t i o n is r e q u i r e d i n t h e p r o c e d u r e . F u r t h e r m o r e , u n d e r t h e c o n d i t i o n s f o r a t o m i z a t i o n , t h e m a x i m u m response w a s o b t a i n e d w i t h n o " m e m o r y " f r o m one a t o m i z a t i o n t o t h e next. T h e h i g h t e m p e r a t u r e r e q u i r e d to a t o m i z e t h e v a n a d i u m l o w e r s t h e l i f e of t h e a t o m i z a t i o n furnaces, a n d i t is r e c o m m e n d e d t h a t t h e f u r n a c e b e r e p l a c e d after 2 0 - 2 5 injections. electrodes

G o o d contact b e t w e e n t h e s u p p o r t

a n d the furnace must be maintained.

c r i t i c a l f o r v a n a d i u m because m a x i m u m p o w e r

T h i s is p a r t i c u l a r l y

is r e q u i r e d to ensure


14.

HOFSTADER

E TA L .

Nickel

and

163

Vanadium

c o m p l e t e a t o m i z a t i o n . E v e n a s m a l l loss of p o w e r b y p o o r contacts m a y substantially reduce the temperature inside the furnace. U n d e r t h e specified c o n d i t i o n s , t h e c a l c u l a t e d d e t e c t i o n l i m i t s ( S / N =

2 ) f o r n i c k e l a n d v a n a d i u m a r e 2 Χ 1 0 " g a n d 25 Χ 1 0 " g, respec 11

11

t i v e l y . W i t h these l i m i t s , i t w a s p o s s i b l e to m e a s u r e 2 n g N i / g , a n d 5 n g V / g i n a n o r i g i n a l 100-g p e t r o l e u m s a m p l e , u s i n g respective 1- a n d 5-μ1 a l i q u o t s of t h e final s o l u t i o n f o r i n j e c t i o n . Response w a s l i n e a r o v e r t h e range 0 - 1 n g N i a n d 0 - 1 0 n g V . M a t r i x effects w e r e e n c o u n t e r e d i n t h e H V A A m e a s u r e m e n t of n i c k e l a n d v a n a d i u m . T h e response w h e n a m i x t u r e of 14 metals w a s a d d e d i n


v a r i o u s ratios to a constant c o n c e n t r a t i o n of n i c k e l a n d v a n a d i u m is s h o w n i n T a b l e 14.111. W h e n t h e c o n c e n t r a t i o n of e a c h i n t e r f e r i n g m e t a l w a s t h e same as n i c k e l , t h e c h a n g e i n t h e n i c k e l response w a s i n s i g n i f i c a n t . H o w e v e r , as t h e c o n c e n t r a t i o n of i n t e r f e r i n g m e t a l w a s i n c r e a s e d , t h e n i c k e l response w a s s i g n i f i c a n t l y e n h a n c e d .

F o r v a n a d i u m , t h e response

w a s s i g n i f i c a n t l y depressed, e v e n w h e n t h e c o n c e n t r a t i o n of e a c h i n t e r f e r i n g m e t a l w a s t h e same as t h e v a n a d i u m c o n c e n t r a t i o n . A l t h o u g h n o e x p l a n a t i o n f o r t h e b e h a v i o r of n i c k e l a n d v a n a d i u m i n t h e presence of other metals has b e e n f o u n d , t h e n i c k e l a n d v a n a d i u m c a l i b r a t i o n curves are l i n e a r , i n d i c a t i n g t h a t t h e m e t h o d of s t a n d a r d a d d i t i o n s c a n b e utilized. E v e n w i t h t h e p r e c a u t i o n s n o t e d above, response f r o m v a n a d i u m w a s often q u i t e v a r i a b l e . C o n s e q u e n t l y , t h e slope a n d i n t e r c e p t of response Table 14.111.

Effect of Other Metals on the Determination of N i c k e l and V a n a d i u m " ' 6

Vanadium

Nickel Concentration of Each Interfering Metal/ ^g/ml 0 0.5 5 50

Avg. Re sponse, mm 50 53 65 89

Std. Avg. Dev. of Re No. Re sponse, of Meas sponse, mm urements mm 5 2 3 10

9 3 3 3

36 29 20 19

Std. Dev. of Response, mm

No. of Measurements

4 4 4 3

12 8 8 6

C o n c e n t r a t i o n of N i or V i n s o l u t i o n : 0.5 μg/m\. A m o u n t injected : 2 μ\ for N i , 5 μ\ for V . I n t e r f e r i n g metals present : S i , A l , C r , C a , F e , M g , N a , M n , Z n , C u , C o , P b , M o , N i , or V . a

6 c

vs.

/Ag/ml

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

squares. T h e s t a n d a r d d e v i a t i o n of t h e response a b o u t t h e regression l i n e w a s also c a l c u l a t e d , a n d a n y d a t a p o i n t s o u t s i d e 2σ of t h e regression l i n e w e r e rejected.

T h e slope a n d i n t e r c e p t w e r e t h e n r e c a l c u l a t e d , a n d t h e


164

ANALYSIS OF P E T R O L E U M

FOR TRACE

METALS

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

by

e x t r a p o l a t i n g t h e " r e f i n e d " regression U n e . I n a l l d e t e r m i n a t i o n s t h e regression l i n e w a s s t a t i s t i c a l l y tested f o r l i n e a r i t y . T h e response w h e n n i c k e l w a s a t o m i z e d v a r i e d less t h a n that of v a n a d i u m , so t h e n i c k e l c o n c e n t r a t i o n i n t h e s a m p l e s o l u t i o n c o u l d b e c a l c u l a t e d e i t h e r b y least squares o r t h e e q u a t i o n o n p . 170. Recommended Method. I n t h e r e c o m m e n d e d m e t h o d a 1 0 0 - g s a m p l e is d e c o m p o s e d w i t h c o n c e n t r a t e d s u l f u r i c a c i d , a s h e d at 500° C , d i s s o l v e d i n d i l u t e h y d r o c h l o r i c a c i d , a n d t h e c o n c e n t r a t i o n of n i c k e l o r v a n a d i u m m e a s u r e d b y H V A A u s i n g t h e m e t h o d of s t a n d a r d a d d i t i o n s . T h e results


of a p p l y i n g this p r o c e d u r e t o several d i s t i l l a t e fuels are s h o w n i n T a b l e 1 4 . I V . E a c h m a t e r i a l w a s s p i k e d t o c o n t a i n different levels o f n i c k e l a n d v a n a d i u m , w h i c h w e r e a d d e d as t h e sulfonates.

Essentially quantitative

recoveries w e r e o b t a i n e d f o r b o t h n i c k e l a n d v a n a d i u m f r o m a l l m a t e r i a l s . T h e s t a n d a r d d e v i a t i o n f o r n i c k e l w a s ± . 6 o v e r t h e r a n g e 5 0 t o 100 n g N i / g , a n d for v a n a d i u m ± 8 n g V / g over the range 30-100 n g V / g . T h e f e w tests at t h e h i g h e r l e v e l i n d i c a t e d a c o m p a r a b l e p r e c i s i o n . S a m p l e s of gasoline, jet f u e l , a n d N o . 2 h e a t i n g o i l w e r e s p i k e d w i t h n i c k e l a n d v a n a d i u m sulfonates a n d , together w i t h u n s p i k e d samples, w e r e a n a l y z e d a t t h e i n i t i a t i n g l a b o r a t o r y a n d at o n e c o o p e r a t i n g l a b o r a tory.

T h e results o n t h e s p i k e d samples at t h e c o o p e r a t i n g

laboratory

w e r e , o n t h e w h o l e , l o w e r t h a n those o f t h e i n i t i a t i n g l a b o r a t o r y

(Table

14.V), although the precision was identical. T h e l o w e r r e c o v e r y at t h e c o o p e r a t i n g l a b o r a t o r y is a t t r i b u t e d t o a t i m e l a g i n t h e analysis. T h e c o o p e r a t i n g l a b o r a t o r y a n a l y z e d t h e samples a b o u t f o u r m o n t h s after t h e y w e r e p r e p a r e d , w h e r e a s t h e i n i t i a t i n g l a b o r a t o r y a n a l y z e d t h e samples i m m e d i a t e l y . A separate l o n g - t e r m s t a b i l i t y s t u d y d e m o n s t r a t e d t h a t n i c k e l a n d v a n a d i u m sulfonates i n kerosene w e r e g r a d u a l l y d e p l e t e d i n storage ( F i g u r e 1 4 . 1 ) , a n d t h e d e l a y i n p e r f o r m i n g Table 14.IV.

Recovery of N i c k e l and Vanadium in Distillate Fuels by H V A A Method Nickel

Sample

Added

Concentration (ng/g) Measured"

Vanadium

% Recovery

Added

Concentration (ng/g) Measured'

% Recovery

53 95

56 93

100 95

35 72

41 74

117 103

Kerosene

104

106

102

109

98

90

Gasoline

234

208

89

468

467

100

D i e s e l fuel

a

Average of triplicate determinations.


14.

HOFSTADER

Nickel

ETAL.

and

165

Vanadium

Table 14.V. Interlaboratory Analysis for N i c k e l and Vanadium by Proposed Method Nickel

Concentration (ng/g)

Added

Measured

0

Sample


Vanadium

Initi ating Labora tory

Cooper ating Labora tory

Concentration (ng/g)

Added

Measured* Initi ating Labora tory

Cooper ating Labora tory

Gasoline

0 34

Nickel and Vanadium

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