Pulse radiolysis at high temperatures and high pressures

Pulse radiolysis at high temperatures and high pressures

RadlatPhys Chem Vol 18, No 3-4, pp 723-731, 1981 0146-5724/81/090723-0950200/0 Pnnted m Great Britain Pergamon Press Ltd PULSE RADIOLYSIS AT H I...

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RadlatPhys Chem Vol 18, No 3-4, pp 723-731, 1981

0146-5724/81/090723-0950200/0

Pnnted m Great Britain

Pergamon Press Ltd

PULSE

RADIOLYSIS

AT H I G H T E M P E R A T U R E S

H11bert *Studsvlk

Chrlstensen*

Energlteknlk

**Riso N a t l o n a l

AND H I G H P R E S S U R E S

and Knud S e h e s t e d * *

AB,

S-611

Laboratory,

82 N y k o p l n g ,

DK-4000

Roskllde,

Sweden Denmark

ABSTRACT A set-up enabllng 320°C)

pulse

radlolysls

and h l g h p r e s s u r e s

(up to 140 bar)

ratlon between

Rlso N a t i o n a l

has been u s e d

for e x p e r l m e n t s

determine

actlvatlon

The a c t x v a t l o n k J - m o l -I more,

wlth

and O H + O H

to t e m p e r a t u r e s

and S t u d s v l k

for r e a c t i o n s

of i m p o r t a n c e

eaq+e:q

(tentatively

8 kJ mol -I,

of 200°C

The a b s o r p t l o n

maxlmum

to be 22

values.

Further-

(13 3 kJomol -I,

1.9 kcal mol -I)

s p e c t r u m of the OH r a d l c a l

to

in r e a c t o r e h e m l s t r y

literature

Cu2++OH

The cell

the p u r p o s e

has b e e n d e t e r m i n e d

of the r e a c t l o n s

(up to

In c o l l a b o -

Energlteknlk.

solutions wlth

in good a g r e e m e n t w l t h

energles

The a b s o r p t l o n

at h l g h t e m p e r a t u r e s

has b e e n c o n s t r u c t e d

aqueous

e n e r g y of the r e a c t i o n

the a c t l v a t l o n

termlned,

Laboratory

energies

(5.3 k c a l . m o l -I)

k c a l . m o l -I)

measurements

3.2

have been de-

has been d e t e r m l n e d

up

is found at 230 nm at all

temperatures.

T h e r e a c t i o n b e t w e e n Fe 2+ and OH r a d x c a l s of 220°C. termlned

An a c t l v a t l o n

has b e e n

e n e r g y of 9 kJ-mol -I

and the s p e c t r u m of the t r a n s l e n t

determlned

at d i f f e r e n t

s t u d i e d up to a t e m p e r a t u r e

(2.2 k c a l - m o l -I)

formed

has been de-

in the r e a c t i o n

has been

temperatures

INTRODUCTION Radlatxon (1-5)

chemlcal

Michael,

studles

H a r t and S c h m x d t

of e-aq in the t e m p e r a t u r e above rature

of a q u e o u s

solutlons

above

(i) have d e t e r m l n e d

range - 4 - 3 9 0 ° C

using

Freeman

et al

(3) have d e t e r m i n e d

range

0-300°C

uslng

SF 6 and N20 as e l e c t r o n

the yleld of the r e d u c l n g 300-410°C.

His

results

products

range

e g g(e:q)=

0 4 at 400°C and 4 8 at 300°C a c c o r d l n g

723 RPCVolIg, No 3/4--.V

scarce

spectrum

capillarles

the yxeld of e-aq in the tempe-

temperature

respectlvely

the a b s o r p t i o n

small S u p r a s l l

200°C.

have d e t e r m l n e d

100°C have been

scavengers

Burns

from y - r a d l o l y s l s

dlsagree with

the results

to Burns

et al

(5)

in the

of Freeman,

and Freeman,

724

H CHRISTENSENand K SEHESTED

A revzew

coverzng

The actzvatzon

the

lzterature

energzes

of the r e a c t z o n

termzned

zn the t e m p e r a t u r e

However,

it zs of g r e a t

about past

radzatzon several

decomposztzon The

- zn m o s t

cases

radzcal-radzcal

were

In o r d e r

reactmons

radzolysls tzated

energy

to g e t m o r e

tlon energzes

to c a l c u l a t e

for d z f f u s z o n

in p r e s s u r l z e d

the r e s u l t s

was

In the

of r a d z a t l o n

szmulatzons.

at r o o m

(9-11).

300°C.

temperatures

For most

estzmated

part

and

of the

to be e q u a l

in w a t e r .

a high

solutzons

about

rate constants

temperature up to 320°C

the a c t z v a t z o n

and bozlzng

information

up to a b o u t

known

energy

znformatzon

to d e t e r m l n e

to get

by c o m p u t e r

energzes

the a c t z v a t z o n

of a q u e o u s

a programme

chemzsts

temperatures

constructed

and O H + H 2 h a v e b e e n de-

at t e m p e r a t u r e s

actzvatzon

(4).

(6-8).

on r a t e c o n s t a n t s

detailed

we h a v e

studzes

zmportance

at r e a c t o r

- estzmated

to the a c t l v a t z o n

for r e a c t o r

reactzons

based

of e a q + e a q

up to 1 0 0 ° C

have been made

of w a t e r

calculatzons

range

znterest

chemzcal

attempts

up to 1969 has b e e n g z v e n by M a t t h e w s

water

cell and

energies

reactors

and actzva-

enabllng

14 M P a

pulse

and have

for r e a c t z o n s

znz-

of

(12).

EXPERIMENTAL The cell

experlmental shown

electrons The

zn F i g u r e zn s z n g l e

optlcal

Zelss M M I 2

system double

and a N l c o l e t

RESULTS

procedure

has b e e n d e s c r l b e d

1 zs u s e d pulses

of m a x z m u m

conslsts quartz

Explorer

zn c o m b z n a t l o n

wzth

a HRC

i.i A and d u r a t z o n

of a 150 W V a r z a n

prlsm monochromator,

3 dzgztal

zn d e t a z l

storage

prevzously iznac from

high-pressure an EMI

(12]

gzvzng

The

i0 M e V

10 ns to 4.2

Xenon

lamp,

vs.

a

9558 Q p h o t o m u l t z p l z e r

osczlloscope.

AND DISCUSSION

Cu 2+ In the p r e v z o u s termzned

znvestzgatzon

at a n u m b e r

(12)

the r a t e c o n s t a n t

of t e m p e r a t u r e s

zn the r a n g e

for r e a c t z o n

rate

Figure

constant

2, and

was

f r o m the

de-

20-220°C.

Cu 2÷ + OH + Cu2+(OH)

The

(1) w a s

(RE i)

plotted slope

as a f u n c t l o n an a c t z v a t l o n

of I/T energy

(K -I)

in a l o g a r l t h m l c

for r e a c t l o n

(i) of

13.3

plot,

Pulse radlolysts at hw,h temperatures and hw,h pressures

725

f,m

Figure

i

High

temperature

501

pressure

I

I

cell I

-I-

20

C -f

~: 10

ao 0

21 ~0

F~ure of

the

rlment

I 2,5

2. T h e

rate

reciprocal at

200oc

YT

constant

K" ) for

the

Kelvln-temperature Time

scale

1 dlv

I 3,0

J 3,5

reactlon Inset = 1 us,

Cu 2+ + O H + C u 2 + O H oscilloscope

absorbance

as a f u n c t i o n

plcture

scale

1 dlv

of an e x p e = 2% a b s o r b a n c e

726

H CmUSTENSENandK SEHE~ED

k J . m o l -I

(3.2 k c a l ' m o l -I)

was

calculated

according

to the A r r h e n i u s

equa-

tion

k = He - E / R T

This

value

fuslon

is e q u a l

of w a t e r

to the r e p o r t e d

in the t e m p e r a t u r e

value range

of the a c t i v a t i o n

energy

for dif-

10-90°C.

OH r a d l c a l The absorptlon being

studled

solutlons

always

to c h a n g e Figure about

The

been

irrad~ated

to a v o l d

w~th

boiling

are d e s c r l b e d

llttle

in the

3. T h l s

result

is found

Spectra

absorptlon

increase

wlth

tunately,

known

only

of c h a n g e

~s the

with

= 3.2.

The denslty

tratlon

of OH r a d l c a l s

temperature

tlon

is n e a r l y

not

ruled

The

rate

out

OH + OH ~ H 2 0 2

constant

increasing

the p o s s l b l l l t y

constant

coefflclent

of r e a c t l o n

wlth wlth

that

from

around

seems

20-200°C,

see

very

a small

showed

increasing p e r °C,

a de-

little

the m a x i m u m

temperature.

but,

unfor-

(13). If the rate

temperature

would

be

i e the c o n c e n at 200°C.

of the OH a b s o r p -

in the r a n g e is found.

dose,

to the

g - c m -3 at 200°C,

change

results

spectrum

wlth

2 to 65°C

at thls

temperature

2 has b e e n

with 0.12%

temperature

thls

range

of 2-7

the cell w a s

Prelimlnary

is a s c r l b e d

is small,

is 0.86

doses

4 or 7 krad,

increases

in m o l . d m -3 s h o u l d

the e x t l n c t l o n

Thls

range

with

are r e c o r d e d

pulse,

the G - v a l u e

of w a t e r

Consequently,

300 nm an a b s o r p t l o n

decay

up to 200°C

2.7-1.2

spectrum

dose.

(i MPa), a q u e o u s

absorption

temperature

spectra

in the t e m p e r a t u r e

same

The

are p r e s e n t l y

temperatures

of 5 MPa.

below.

a larger

~nitlal

us-pulses

at the h i g h

~f the

increaslng

The

in g(OH)

with

investlgated

taken w ~ t h

of OH r a d l c a l s .

N20-saturated

Ar up to a p r e s s u r e

investlgatlon

2 krad.

of the OH r a d i c a l

up to 250°C.

very

creaslng decay

have

In o r d e r

pressurlzed

thls

a n d the r e a c t l o n s

at t e m p e r a t u r e s

(pH 6-9)

krad/pulse.

from

spectrum

20-200°C.

We have,

Above

however,

is an a r t l f a c t .

studled

in the

same

temperature

(RE 2)

range

Pulse radlolys*s at h~,h temperatures and high pressures

I

I

727

I

0.02

I

n

0

0

001

0 O

0

0

0 0 []

0 + o 200

I

I

I

250

300

350

k(nm) Fl~ure

3. The

ca 2 krad.

+:

spectrum

of the OH r a d l c a l

20°C,

90°C,

o:

O:

150°C,

at v a r l o u s

A: 200°C.

temperatures.

Dose

728

H CHRISTENSENand K SEHESTED

a n d the

actavatlon

(prelimxnary culatxon

energy

result).

of rate

gramme

developed

stant

of r e a c t l o n

has b e e n

However,

constants by L a n g

determlned

we h a v e

to be 8 k J ' m o l -I

started

to i m p r o v e

by the use of c o m p u t e r

Rasmussen,

RlSO.

2 in N 2 0 - s a t u r a t e d

our m e t h o d

slmulatxon

For determinatlon

solutxons

we use

the

(1.9 k c a l - m o l -I)

using

for cal-

a pro-

of the rate followlng

scheme:

OH + OH + H202

(RE 2)

OH + H202

(RE 3)

+ HO 2 + H 2 0

H + OH + H 2 0

(RE 4)

H + 02 + HO 2

(RE 5)

For

reactlons

The

extxnctxon

as 500,

3-5 the a c t l v a t l o n coefflcxents

2000,

and

40

energxes

suggested

at 230 nm of OH,

(mol-l-dm3-cm-l),

HO 2

by J e n k s

(9) w a s

(02 ) and H 2 0 2

con-

used.

were

taken

respectively.

Fe 2+ The

reactlon

various

between

temperatures

Fe 2+ a n d OH r a d l c a l s ,

reactxon

(6), has b e e n

rapld

thermal

sured

at 300 nm.

(RE 6)

to s t u d y

k J - m o l -I Figure

The

of

The

flrst

10 -3 M a n d

reaction

The rate order

rate

of b u i l d - u p constant

M - i s -I at 220°C

uslng

temperatures

of the t r a n s i e n t

was

found

to v a r y

N20-saturated

was

determxned

from the A r r h e n l u s

d u e to

was mea-

from

4.3.108

(i MPa), a q u e o u s energy plot

of 9

shown

in

4.

5. T h e

absorptlon

spectrum two

of the t r a n s l e n t

spectra

spectrum

are

at r o o m

xdentlcal

temperature

the e x t l n c t x o n

w a s ca 30%

The

spectrum

of the t r a n s x e n t

2,

5 and

absorptlon

mlned

at pH 7 at h l g h

3-10 -4 M Fe 2+ at pH 3. An a c t l v a t x o n

(2.2 k c a l - m o l -I)

absorptxon

Fxgure

the

preclpltatlon.

M - I s -I at 20°C to 2 . 1 - 1 0 9 solutions

at

and pH

Fe 2+ + OH + Fe2+(OH)

It is n o t p o s s l b l e

studxed

at pH

i,

3, 4,

found wxthxn had

at 90 and

180°C

the e x p e r l m e n t a l

the same

general

are

shown

error.

appearance

in

The but

lower.

6 at r o o m

formed

in r e a c t l o n

temperature.

Wxth

(6) w a s d e t e r -

decreaslng

pH

Pulse radtolysls at lugh temperatures and lugh pressures

~0

I

7'29

I

2O

m

4:

+

I

";"~ lo

%

5

2 2,0

I

I

2,5

3,0

3,5

I/T(10.3 6') [email protected]

4. The

t l o n of the

the

rate

constant

reclprocal

absorptlon

of the r e a c t i o n

Kelvln

below

probably

replaced

250 nm i n c r e a s e d by Fe 3+ lons

as a f u n c -

temperature.

at 300 nm d e c r e a s e d ,

sorptlon

Fe 2+ + OH ÷ F e 2 + O H

the maxlmum

conslderably. formed

dlsappeared,

The

translent

a n d the abFe2+(OH)

Is

in a f a s t r e a c t l o n .

ACKNOWLEDGEMENT We w l s h

to t h a n k

H Corfltzen acknowledges

E B3ergbakke

for s k l l f u l l a grant

for the c o m p u t e r

technlcal

asslstance.

f r o m the S w e d l s h

Board

slmulatlon

studles

H Chrlstensen

for T e c h n l c a l

and

gratefully

Development

(STU).

H CHRISTENSENand K SEHESTED

730

I

I

0,03

002

a 0

0.01

--

0 250

I

I

300

350

X (nm) [email protected] 5

The spectrum of Fe 2+ OH at pH 3 at 90°C

(+) and 180°C

(®)

Pulse radlolysls at hlgh temperatures and lush pressures

731

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B D MICHAEL,

E J HART and K H SCHMIDT,

2.

R S DIXON and V J LOPATA,

3.

K N JHA,

4.

R W MATTHEWS,

5.

W G BURNS,

6.

E J HART

Radiat

Phys C h e m

T G RYAN and G R FREEMAN,

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537,

W C GOTTSCHALL

The H y d r a t e d

and E J HART,

7.

B HICKEL,

Proc Tzhany

8.

K H SCHMIDT,

9.

G H JENKS,

10.

G H JENKS

and J C GRIESS,

ii.

W G BURNS

and P B MOORE,

12.

H CHRISTENSEN

13.

C J HOCHANADEL

1978,

Symp Radlat

Harwell

Electron,

Wiley, 71,

9516,

N e w York,

1980.

1970,

2102.

1977,

4, 801.

ORNL-3848,

1965.

Oak Ridge Natl Lab Report

Effects

Radiat

and J A GHORMLEY,

868.

1257.

Oak Ridge Natl Lab Report

and K SEHESTED,

79,

report A E R E - R

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81,

Radlat

2037.

135.

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J Phys Chem 1967,

J Phys Chem 1977,

ll,

75,

1970.

W R M A R S H and J KIMBER,

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1976,

Phys C h e m

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30,

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