Solubilities of phenol in supercritical carbon dioxide from aqueous phenol solutions
by Eric Raymond Leland
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in
Chemical Engineering
Montana State University
© Copyright by Eric Raymond Leland (1986)
Abstract:
The existing techniques for treating industrial chemical wastewater could benefit from cheaper and
improved processing. Recent research has focused some attention upon supercritical fluid extraction.
The purpose of this research was to experimentally measure solubilities of phenol, a common
wastewater pollutant, in supercritical carbon dioxide from aqueous phenol solutions. A thermodynamic
model of this system was also developed.
Extraction experiments were performed with a single pass flow apparatus. Liquid carbon dioxide was
fed into the extraction cell by way of a high pressure liquids pump. The charged vapor samples were
bubbled through water to isolate the product phenol. A wet chemistry, direct photometric method was
used for phenol analysis. Experiments were run at 40 and 60 degrees Celsius. Aqueous phenol
solutions of 10,000 parts per million, ppm, 5,000 ppm, and 2,500 ppm were studied. The pressures
investigated ranged from 1,100 psi to 2,800 psi.
Measured experimental phenol mole fractions in supercritical carbon dioxide ranged from 0.000060 to
0.00080. At 40 degrees Celsius the vapor phase phenol solubility increased with increasing pressure. At
60 degrees Celsius the vapor phase phenol solubility passed through minimums over pressure at lower
pressures. Larger aqueous phenol solution concentrations gave larger vapor phase phenol solubilities at
both temperatures. The lower temperature of 40 degrees Celsius gave larger vapor phase phenol
solubilities than at 60 degrees Celsius.
The data generated by the thermodynamic model of the aqueous phenol-supercritical carbon dioxide
system passed through minimums in vapor phase phenol solubilities at both 40 and 60 degrees Celsius
in the pressure range of 600 to 700 psia. The model predicted general trends at both temperatures but
also showed discrepancies at both temperatures. These discrepancies might have been caused by
assumptions made to solve the model. SOLUBILITIES OF PHENOL IN SUPERCRITICAL
CARBON DIOXIDE FROM AQUEOUS PHENOL SOLUTIONS
by
E rie Raymond Leland
A t h e s i s subm itted in p a r t i a l f u l f i l l m e n t
o f th e requirem ents fo r th e degree
• of
Master o f S c ie n c e
in
Chemical .Engineering
MONTANA STATE UNIVERSITY
Bozeman, Montana
January 1986
^7?
LS 3 Z
ii
APPROVAL
o f a t h e s i s subm itted by
E ric Raymond Leland
T h is t h e s i s h as been read by e a c h member o f t h e t h e s i s c o m m i t t e e
and has been found t o be s a t i s f a c t o r y regardin g c o n te n t, E n glish usage,
form at, c i t a t i o n s , b ib lio g r a p h ic s t y l e , and c o n s is t e n c y , and i s ready
for su bm ission to th e C o lle g e o f Graduate S t u d ie s .
'■ M .
Dr. Warren S carrah , Chairman
Approved fo r th e Major Department
Approved fo r the C o lle g e o f Graduate S t u d ie s
Date
Dr. Henry17P arson s, Graduate Dean
iii
STATEMENT OF PERMISSION TO USE
In
p r e se n tin g
th is
th e sis
in
p a r tia l
fu lfillm e n t
of
th e
req u irem en ts fo r a m aster's degree a t Montana S t a t e U n i v e r s it y , I agree
t h a t t h e L ib r a r y s h a l l make i t a v a i l a b l e t o b o r r o w e r s under r u l e s o f
th e Library,
B r i e f q u o ta tio n s from t h i s t h e s i s are a ll o w a b le w ith ou t
p e r m is s io n , provided t h a t a c c u r a te acknowledgment of sou rce i s made.
P e r m i s s i o n f o r e x t e n s i v e q u o t a t i o n from or r e p r o d u c t i o n o f t h i s
t h e s i s may be granted by my major p r o f e s s o r ,
or in h i s / h e r absence, by
th e D ir e c to r o f L ib r a r ie s when, in th e o p in io n of e i t h e r ,
use of th e m a te r ia l i s fo r s c h o la r ly pu rp oses.
th e proposed'
Any c o p y i n g or u s e o f
t h e m a t e r i a l i n t h i s t h e s i s f o r f i n a n c i a l g a in s h a l l n o t be a l l o w e d
w ith o u t my w r it t e n p e r m issio n .
iv
X
TABLE OF CONTENTS
Page
APPROVAL............................................................................................
STATEMENT OF PERMISSION TO U S E ................................
ii
iii
TABLE OF CONTENTS.......................................................................................................iv
LIST OF TABLES................................................................................................................ v i
LIST OF F I G U R E S ......................................................................................................... v i i
ABSTRACT...................• .................................................................................................. ix
INTRODUCTION ............................................................................................
Wastewater Treatment Via S u p e r c r i t i c a l F lu id s . . . . . . . .
Research O b j e c t iv e s ........................................................................................
S u p e r c r i t i c a l F l u i d s ........................ ...............................................................
E x tr a c tio n With S u p e r c r i t i c a l F lu id s ......................................................
S u p e r c r i t i c a l F lu id A p p lic a t io n s .............................................................
High P ressu re Experim ental Methods ........................................................
Flow M e t h o d s ......................................................................................................
S t a t i c Methods . . ........................................................................................
EXPERIMENTAL ...................................................
I
I
2
2
3
4
5
5
6
7
7
Experim ental D e s i g n ............................................................ • .........................
Experim ental Apparatus ....................................................................................
7
Experim ental Procedure .................................................................................... 10
Phenol A n a ly s is .................................................................................................. 13
R e a g e n t s ..........................................................................................................................13
V
TABLE OF CONTENTS— Continued
RESULTS AND DISCUSSION ........................................................................
14
General O b s e r v a t i o n s ....................................................................................■ . 14
.....................................
14
Experimental S o l u b i l i t i e s
Data a t 40 D egrees C e l s i u s ........................................................................... 15
Data a t 60 Degrees C e ls iu s . . . ................................
19
21
Thermodynamic Modeling . . ..........................................................................
M o d e l i n g .....................................................................
21
Modeling R e s u l t s ................................................................................... .... . 26
D esign C o n s i d e r a t i o n s ................................
31
SUMMARY..............................................................................................................................36
RECOMMENDATIONS FOR FURTHER STUDY
............................................................
38
REFERENCES CITED........................................................' ............................................40
APPENDICES ........................................
Appendix A - D e r iv a tio n o f Thermodynamic Model ............................
Appendix B - Computer Aided S o lu t io n s o f th e Thermodynamic
Model o f Aqueous P h e n o l- S u p e r c r it ic a l Carbon
D ioxid e Vapor-Liquid Equ ilibriu m . . . . . . .
Appendix C - S p ectrop h otom etric Phenol A n a ly s is C a lib r a t io n
Curve o f Absorbance Versus Phenol
C on cen tration ..........................................................................
42
43
50
58
vi
LIST OF TABLES
Page
T ab les
1.
Hole F r a c tio n Phenol in S u p e r c r i t i c a l Carbon D ioxid e
a t 40 d e g r e e s C e l s i u s
........................................................................... 16
2.
Mole F r a c tio n Phenol in S u p e r c r i t i c a l Carbon D ioxid e
a t 60 d e g r e e s C e l s i u s
........................................................................... 19
3.
Aqueous P h e n o l- S u p e r c r it ic a l Carbon D ioxid e Model
C a lc u la te d V alues of. Mole F r a c t io n s in th e Vapor Phase,.
Vapor Phase Component F u gacity C o e f f i c i e n t s , and Poynting
C o r r e c tio n s fo r Phenol and Water a t 60 d egrees C e ls iu s
and P h e n o l S o l u t i o n C o n c e n t r a t i o n o f 10,000 ppm ...................30
4.
E xperim ental Mole F r a c tio n s o f Phenol in Water, Mole
F r a c t io n s o f Phenol in S u p e r c r i t i c a l Carbon D ioxid e, and
E q u ilibriu m K -values a t 40 d e g r e e s C e l s i u s ..................................31
5.
E xperim ental Mole F r a c tio n s o f Phenol in Water, Mole
F r a c t io n s o f Phenol in S u p e r c r i t i c a l Carbon D ioxid e,
and E q u i l i b r i u m K - v a l u e s a t 60 d e g r e e s C e l s i u s .......................33
v LI
LIST OF FIGURES
Page
F igu res
1.
Schematic o f phenol e x t r a c t i o n apparatus ..........................................
2.
E xperim ental vapor phase phenol s o l u b i l i t i e s
in s u p e r c r i t i c a l carbon d io x id e a t 40 d egrees C e l s i u s
. . .
8
17
3.
S u p e r c r i t i c a l carbon d io x id e d e n s it y as a fu n c tio n
o f p r e s s u r e a t 40 and 60 d e g r e e s C e l s i u s ......................................18
4.
Experim ental vapor phase phenol s o l u b i l i t i e s in
s u p e r c r i t i c a l c a r b o n d i o x i d e a t 60 d egrees C e ls iu s ............... 20
5.
Experim ental vapor phase phenol s o l u b i l i t i e s in
s u p e r c r i t i c a l carbon d io x id e a t 40 and 60 d egrees C e ls iu s . . 22
6.
Thermodynamic m odel-generated vapor phase phenols o l u b i l i t i e s and e x p erim en ta l phenol s o l u b i l i t i e s in
s u p e r c r i t i c a l carbon d io x id e a t 40 d e g r e e s C e l s i u s .................27
7.
Thermodynamic m od el-generated vapor phase phenol
s o l u b i l i t i e s and ex p erim en ta l phenol s o l u b i l i t i e s in
s u p e r c r i t i c a l c a r b o n d i o x i d e a t 60 d egrees C e ls iu s ............... 28
8.
C a lcu la ted d i s t r i b u t i o n c o e f f i c i e n t s o f phenol from
ex p erim en ta l data for system p ressu re a t 40 d egrees
C e l s i u s .......................................................
9.
32
C a lcu la ted d i s t r i b u t i o n c o e f f i c i e n t s o f phenol from
ex p erim en ta l data fo r system p ressu r e a t 60 d egrees
C e l s i u s ....................................................................................................................... 34
10. Comparison o f two s o l u t i o n methods of the aqueous p h en ols u p e r c r i t i c a l carbon d io x id e thermodynamic model a t 40
d egrees C e l s i u s (method I used a l l th r e e of the component
f u g a c it y eq u a tio n s and method 2 used two o f the component
f u g a c it y eq u a tio n s and a vapor phase mole b alan ce) ............. 52
v iii
LIST OF FIGURES— Continued
Page
11. Comparison of two s o l u t i o n methods o f th e aqueous p h en o ls u p e r c r i t i c a l carbon d io x id e thermodynamic model a t 60
d egrees C e ls iu s (method I used a l l t h r e e o f th e component
f u g a c i t y e q u a tio n s and method 2 used two o f th e component
f u g a c i t y e q u a tio n s and a vapor phase mole b alan ce) . . . . . .
53
12. Computer program t o c a l c u l a t e th e v a p o r - liq u id
e q u ilib r iu m o f th e aqueous p h e n o l - s u p e r c r i t i c a l carbon
d i o x i d e s y s t e m ............................................................................................... 54
13. Phenol a n a l y s i s c a l i b r a t i o n curve o f absorbance v e r s u s
p h e n o l c o n c e n t r a t i o n ...............................................................................
59
ABSTRACT
The e x i s t i n g t e c h n i q u e s f o r t r e a t i n g i n d u s t r i a l c h e m i c a l
w astew ater could b e n e f i t from cheaper and improved p r o c e s s in g .
Recent
r e s e a t ch h a s f o c u s e d s o m e a t t e n t i o n upon s u p e r c r i t i c a l f l u i d
e x t r a c t i o n . The purpose o f t h i s resea r ch was to e x p e r im e n t a lly measure
s o l u b i l i t i e s o f phenol, a common w a ste w a ter p o l lu t a n t , in s u p e r c r i t i c a l
carbon d io x id e from aqueous phenol s o l u t i o n s . A thermodynamic model of
t h i s system was a l s o developed.
E x t r a c t i o n e x p e r i m e n t s w ere p e r fo r m e d w it h a s i n g l e p a s s f l o w
apparatus.
Liquid carbon d io x id e was fed i n t o the e x t r a c t i o n c e l l by
way o f a h ig h p r e s s u r e l i q u i d s pump. The c h a r g e d vapor s a m p l e s w ere
bubbled through water to i s o l a t e the product phenol.
A wet c h e m istr y ,
d i r e c t p h otom etric method was used for phenol a n a l y s i s .
Experiments
w ere run a t 40 and 60 d e g r e e s C e l s i u s .
Aqueous p h e n o l s o l u t i o n s o f
1 0 ,0 0 0 p a r t s per m i l l i o n , ppm, 5 ,0 0 0 ppm, and 2 ,5 0 0 ppm w ere s t u d i e d .
The p r e s s u r e s i n v e s t i g a t e d ranged from 1,100 p si to 2,800 p s i.
M easured e x p e r i m e n t a l p h e n o l m ole f r a c t i o n s in s u p e r c r i t i c a l
carbon d io x id e ranged from 0.000060 to 0.00080.
At 40 d eg ree s C e ls iu s
th e vapor phase phenol s o l u b i l i t y in c r e a se d w ith i n c r e a s i n g p ressu re.
At 60 d eg ree s C e ls iu s th e vapor phase phenol s o l u b i l i t y passed through
minimums o v e r p r e s s u r e a t lo w e r p r e s s u r e s .
L arger a q u e o u s p h e n o l
s o l u t i o n c o n c e n t r a t io n s gave la r g e r vapor phase phenol s o l u b i l i t i e s a t
both tem p eratu res.
The low er tem perature o f 40 d eg ree s C e ls iu s gave
la r g e r vapor phase phenol s o l u b i l i t i e s than a t 60 d e g r e e s C e ls iu s .
The d a ta g e n e r a t e d by t h e th erm o d y n a m ic m odel o f t h e a q u eo u s
p h e n o l - s u p e r c r i t i c a l carbon d io x id e system passed through minimums in
vapor p h ase p h e n o l s o l u b i l i t i e s a t both 40 and 60 d e g r e e s C e l s i u s in
t h e p r e s s u r e r a n g e o f 600 t o 700 p s i a. The model p r e d i c t e d g e n e r a l
t r e n d s a t b oth t e m p e r a t u r e s but a l s o showed d i s c r e p a n c i e s a t b oth
tem p eratu res. These d is c r e p a n c i e s might have been caused by assum p tion s
made to s o l v e the model.
I
INTRODUCTION
Wastewater Treatment Via S u p e r c r i t i c a l F lu id s
A c o n s ta n t and i n t e g r a l part o f c h em ic a l p ro cess in d u str y i s th e
i n v e s t i g a t i o n and a d a p ta tio n of new or e x i s t i n g t e c h n o lo g i e s t h a t might
im p r o v e a p r o c e s s ' s e c o n o m ic s a n d /o r b o o s t i t s o v e r a l l p e r f o r m a n c e .
The trea tm en t o f i n d u s t r i a l ch em ical w astew ater i s an area th a t could
b e n e f i t from c h e a p e r and im p ro v ed p r o c e s s i n g .
S u p e r c r itic a l flu id
e x t r a c t i o n could be a p rom isin g method fo r t r e a t i n g w a ste w a ter .
S u p e r c r i t i c a l f l u i d e x t r a c t i o n i n v o l v e s e x t r a c t i o n w ith a f l u i d
above i t s c r i t i c a l p o in t ( c r i t i c a l tem p eratu re, Tc,
P c ).
c r i t i c a l p ressu re,
The f l u i d ' s s o l v e n t power i n t h e c r i t i c a l r e g i o n v a r i e s g r e a t l y
w ith s m a ll changes in tem perature and p r e s s u r e .
in c lu d e
t h e d e c a f f e i n a t i o n iof c o f f e e ,
r e g e n e r a tio n of. a c t i v a t e d carbon.'
R ecent a p p lic a t io n s
ex tra c tio n
of
sp ic e s,
Carbon d io x id e i s overw h elm ingly the
p r e f e r r e d s o l v e n t i n m ost a p p l i c a t i o n s .
Carbon d io x id e has moderate
c r i t i c a l p r o p e r t i e s (Tc = 31 d e g r e e s C e l s i u s , . Pc = 1070 p s i a ) ,
en v ir o n m en ta lly s a f e ,
and
is
r e a d i ly a v a i l a b l e , and r e l a t i v e l y in e x p e n s iv e .
The p r o s p e c t o f u s i n g s u p e r c r i t i c a l f l u i d e x t r a c t i o n t o t r e a t
w astew ater i s mentioned by B o tt [ I ,
p. 229].
However, t h e r e i s l i t t l e
p u b l i s h e d e x p e r i m e n t a l d a t a f o r s o l u b i l i t i e s o f common w a s t e w a t e r
p o l l u t a n t s i n s u p e r c r i t i c a l c a rb o n d i o x i d e as a f u n c t io n o f p r e ssu r e
and tem perature.
In o r d e r t o
Also most o f th e s o l u b i l i t i e s are fo r pure m a t e r ia ls .
fu rth er
assess
t h e p o t e n t i a l o f s u p e r c r i t i c a l c a rb o n
d io x id e in t r e a t i n g w astew ater th e r e i s a need to i n v e s t i g a t e aqueous
w a ste s o l u t i o n s .
Van Leer and P a u l a i t i s have reported th e s o l u b i l i t i e s
2
o f a common w a s t e w a t e r p o l l u t a n t , p h e n o l , in s u p e r c r i t i c a l c a rb o n
d io x id e as a fu n c t io n o f p ressu re [2,
pp. 2 5 7 -259].
They dem onstrated
t h a t s u p e r c r i t i c a l carbon d io x id e i s
an e f f e c t i v e s o lv e n t fo r phenol.
T h e r e f o r e , an i n v e s t i g a t i o n i n t o t h e s o l u b i l i t i e s o f a q u e o u s p h e n o l
s o l u t i o n s in s u p e r c r i t i c a l carbon d io x id e appears w o rth w h ile.
Research O b j e c t iv e s
The primary o b j e c t i v e o f t h i s re se a r c h was to measure e x p erim en ta l
vap or l i q u i d e q u i l i b r i u m d a t a f o r t h e a q u e o u s p h e n o l - s u p e r c r i t i c a l
c a rb o n d i o x i d e s y s t e m .
E x p e r i m e n t a l a p p a r a t u s and p r o c e d u r e s w ere
developed t o c r e a t e a rep r o d u c ib le system .
A thermodynamic model of
th e above mentioned system was developed t o p r e d ic t vapor and l i q u i d
phase c o m p o s itio n s a t e q u ilib r iu m .
S u p e r c r i t i c a l F lu id s
Pure f l u i d s a r e g e n e r a l l y t h o u g h t o f a s l i q u i d s and g a s e s .
T h is
i s t r u e f o r m ost f l u i d s up t o a s p e c i f i c p o i n t c a l l e d t h e c r i t i c a l
p o i n t , h e r e t h e tw o p h a s e s become i n d i s t i n g u i s h a b l e .
The c r i t i c a l
p o in t
and
has
th e
co o rd in a tes
of
c r itic a l
tem p era tu re
c r itic a l
p ressu r e.
Above th e c r i t i c a l tem perature i t i s not p o s s i b l e to l i q u e f y
th e f lu id
a t any p r e s s u r e .
r e q u ite d
d isc u ssio n
to
liq u e fy
of
th e
th e
The c r i t i c a l
flu id
c r itic a l
at
reg io n
its
of
p ressu re i s th e p ressu re
c r itic a l
pure f l u i d s
tem p era tu re.
A
and a p h y s i c a l
d e s c r i p t i o n o f a f l u i d a t i t s C r i t i c a l p o in t i s provided by Smith and
Van N e s s [ 3 , pp. 5 7 - 6 0 ] .
3
E x tr a c tio n With S u p e r c r i t i c a l F lu id s
The in h e r e n t p h y s ic a l p r o p e r t ie s o f s u p e r c r i t i c a l f l u i d s are very
a ttr a c tiv e
from
th e
sta n d p o in t
of
a se p a r a tio n
te c h n iq u e .
f o l l o w i n g d e s c r i p t i o n o f t h e s e p r o p e r t ie s i s given by B o tt [ I ,
In i t s
The
p. 229].
s u p e r c r i t i c a l s t a t e th e dense f l u i d i s very m ob ile. ■The f l u i d
has a d e n s it y o f up t o o n e -th ir d or more compared t o t h e l i q u i d s t a t e ,
w h i l e i t s v i s c o s i t y can be a s lo w a s o n e - f i f t h or l e s s d e p e n d in g on
p r e s s u r e and t e m p e r a t u r e .
T h is
a p p r o a c h in g t h o s e o f t h e l i q u i d
r e su lts
in
flu id
s o lu b ilitie s
p h a se y e t t h e f l u i d can p e n e t r a t e
f a s t e r and d e e p e r i n t o a s o l i d m a t r ix o f n a t u r a l s u b s t a n c e s or c o u ld
p r o g r e ss f a s t e r through a d en sely packed f ix e d bed or column.
E x tra ctio n v ia
fo llo w in g
fea tu res
su p e r c r itic a l
w h ich a r e p r o v id e d
r e la tiv e ly in v o la tile
flu id s,
flu id s
is
c h a r a c te r iz e d
by W ilk e
[4,
by t h e
p. 7 0 1 ] :
(I)
m a t e r i a l s can be d i s s o l v e d by s u p e r c r i t i c a l
som etim es even s e l e c t i v e l y ,
(2) phenomena o f d i s t i l l a t i o n and
e x tr a c tio n are sim u lta n e o u sly in v o lv e d ,
i . e . e n h a n cem en t o f vapor
p r e s s u r e and p h a se s e p a r a t i o n b o th p l a y a r o l e , ( 3 ) t h e p r o p e r t i e s o f
t h e s u p e r c r i t i c a l f l u i d s u ch a s d e n s i t y can be v a r i e d w i t h i n w id e
l i m i t s by means of p ressu r e and tem p eratu re,
and (4) s e p a r a t io n o f th e
d i s s o l v e d s u b s t a n c e s can be a c c o m p l i s h e d e i t h e r by a r e d u c t i o n o f
pressure
(at co n sta n t
con stan t p ressu re).
2 2 9]:
t e m p e r a t u r e ) or by r a i s i n g
tem p era tu re
(at
Two a d d i t i o n a l f e a t u r e s a r e g i v e n by B o t t [ I , p.
( I ) th e lo w er o p e r a t in g te m p e r a tu r e s in v o lv e d a llo w fo r th e
s u c c e s s f u l e x t r a c t i o n o f heat s e n s i t i v e compounds,
and (2) th e use of
s u p e r c r i t i c a l carbon d io x id e l e a v e s no harmful r e s id u e s . .
4
S u p e rcritica l flu id
process.
High
pressure
ex tra c tio n i s
processes
a r e la tiv e ly
are
reco g n ized
h ig h p r e s s u r e
as
h ig h
cost
o p e r a tio n s due t o e x p e n s iv e equipment and energy demands t o m ain tain
p la n t p ressu r e.
e x tr a c tio n
These c o s t s may be p r o h i b i t i v e to s u p e r c r i t i c a l f l u i d
u n le ss th ere
p r o c e s s e n j o y s key
ex tra ctio n .
is
some t y p e o f e n e r g y r e c o v e r y a n d /o r a
ad van tages
from
u sin g
su p e r c r itic a l
flu id
There i s very l i t t l e p u b lish ed in fo r m a tio n on th e c o s t s o f
su p e r c r itic a l
flu id
e x tr a c tio n .
An a r t i c l e
by P e t e r
and Brunner
d i s c u s s e d d a t a on t h e c o s t s o f s e p a r a t i o n o f n o n - v o l a t i l e su b sta n ces
[ 5 , pp. 7 4 6 - 7 5 0 ] .
S u p e r c r i t i c a l F lu id A p p lic a t io n s
C h e m ic a l p r o c e s s i n d u s t r i e s h a v e begun t o e x p l o i t t h e u s e s o f
su p e rcritica l flu id s.
An a r t i c l e by Kohn and Savage r e v ie w s prom ising
a p p l i c a t i o n s of s u p e r c r i t i c a l f l u i d s ,
but i t i s w ith o u t r e f e r e n c e s [6,
pp. 4 1 - 4 3 ] .
S u p e r c r i t i c a l carbon d io x id e has dem onstrated an a f f i n i t y towards
some n a t u r a l p r o d u c t c o n s t i t u e n t s s u ch a s c a f f e i n e
e x tr a c ts of sp ic e s.
in
c o f f e e and
An a r t i c l e by Z o s e l g i v e s a d e s c r i p t i o n o f t h e
d e c a f f e i n a t i o n of c o f f e e v i a s u p e r c r i t i c a l carbon d io x id e [7,
709].
pp. 707-
H ubert and V itzhum p r o v i d e an i n t r o d u c t i o n t o t h e m eth od s o f
s u p e r c r i t i c a l carbon d io x id e e x t r a c t i o n o f hops, s p i c e s , and tobacco in
th e ir a r t ic le
[8,
pp. 710-715].
S u p e r c r i t i c a l c a r b o n d i o x i d e i s a l s o b e in g u s e d t o r e g e n e r a t e
a c t i v a t e d carbon [ 9 ] .
5
The u s e s o f s u p e r c r i t i c a l f l u i d s are f in d in g a p p l i c a t i o n s in th e
f u e l s in d u str y .
Kerr-McGee has c o m m erc ia lized a p r o c e s s t h a t e x t r a c t s
a s p h a l t e n e s and r e s i d u e s from d i s t i l l a t i o n r e s id u e in o i l r e f i n e r i e s
u sin g s u p e r c r i t i c a l a l i p h a t i c h y d r o c a r b o n s [ 6 , pp. 4 1 - 4 2 ] .
B r ita in 's
N a t i o n a l C oal Board R e s e a r c h E s t a b l i s h m e n t i s u s i n g s u p e r c r i t i c a l
t o l u e n e t o e x t r a c t l i g h t h y d r o c a r b o n s from c o a l l e a v i n g
charred r e s id u e [6,
b eh in d a
pp. 4 2 -4 3 ].
High P ressu re Experim ental Methods
There are two g e n e r a l approaches t o measuring high p r e ssu r e vaporliq u id eq u ilib r iu m .
T h e s e a r e f l o w s y s t e m s and s t a t i c s y s t e m s .
An
a r t i c l e by Young d e s c r ib e s t h e s e s y ste m s in g en era l and a l s o p r e s e n ts
s p e c i f i c exp erim en tal system s th a t have been used [10, pp. 8 3 - 1 0 4 ] .
Flow Methods
There are two t y p e s of flo w s y s te m s ,
th e vapor r e c i r c u l a t i o n system .
pure g a s a t a s p e c i f i e d
s p e c i f i e d tem perature.
th e s i n g l e pass system , and
In th e s i n g l e pass system a sample o f
pressure i s
p a s s e d th r o u g h a l i q u i d a t a
In a given le n g t h o f tim e th e l i q u i d and vapor
are e s s e n t i a l l y in e q u ilib r iu m , which in a w e l l d esign ed system i s l e s s
than f i f t e e n m inutes [10, p. 83].
When e q u ilib r iu m i s reached sam ples
o f vapor and l i q u i d are withdrawn fo r a n a l y s i s .
The vapor r e c i r c u l a t i n g method s t a r t s w ith l i q u i d and vapor in a
v e s s e l a t a s p e c i f i e d tem perature and p r e s s u r e .
Vapor i s withdrawn and'
r e c i r c u l a t e d through th e l i q u i d , t h i s v a p o r - liq u id c o n t a c t a ll o w s fo r a
rap id approach t o e q u ilib r iu m .
When e q u ilib r iu m i s reached sam ples o f
vapor and l i q u i d are withdrawn fo r a n a l y s i s .
6
The s i n g l e pass method s u f f e r s from two major d isa d v a n ta g e s w ith
r e s p e c t t o th e vapor r e c i r c u l a t i o n method.
F irst,
it
is
d i f f i c u l t to
e s t a b l i s h whether e q u ilib r iu m has been reached in one p ass or not.
The
second d isad van tage i n v o l v e s th e p r e s s u r iz i n g of th e v e s s e l c o n ta in in g
liq u id .
A l l o f t h e vap or u sed t o p r e s s u r i z e t h e v e s s e l c o n t a c t s t h e
l i q u i d below th e s p e c i f i e d p ressu re.
To in s u r e t h a t th e vapor sample
withdrawn i s r e p r e s e n t a t i v e of th e o p e r a tin g p ressu r e,
th e v e s s e l must
e i t h e r have enough v a p o r p a s s e d th r o u g h i t t o " c le a r " o u t t h e i n i t i a l
vapor or th e v e s s e l ' s c o n t e n t s must be mixed a t o p e r a tin g c o n d it io n s .
S t a t i c Methods
There are s e v e r a l ty p e s o f equipment sy stem s fo r measuring s t a t i c
high p ressu r e e q u ilib r iu m .
p h a se m i x t u r e
p ressu r e.
in
A t y p i c a l method c o n s i s t s o f p la c in g a tw o-
a se a le d
v e s s e l at a s p e c ifie d
t e m p e r a t u r e and
Then th e v e s s e l ' s c o n t e n t s are mixed and when e q u ilib r iu m i s
reached vapor and l i q u i d sam ples are withdrawn fo r a n a l y s i s .
one major d isa d v a n ta g e t o s t a t i c methods.
There i s
The p ressu r e i s u s u a lly not
h e ld c o n s t a n t w h i l e s a m p l e s a r e b e in g w it h d r a w n , w h ic h can l e a d t o
c o n s id e r a b le e r r o r .
7
EXPERIMENTAL
Experim ental Design
The e x p e r i m e n t a l work was p e r f o r m e d i n t h r e e s t a g e s .
stage
was t h e
ap p aratu s.
d ev elo p m en t o f
a w o r k in g
and
r e lia b le
The f i r s t
ex tra c tio n
N ex t a s e r i e s o f e x p e r i m e n t s w ere p e r fo r m e d t o d e v e l o p a
p r a c t ic a l e x p e r im e n ta l procedure w ith r e p r o d u c ib le r e s u l t s .
T h ese
exp erim en ts a l s o gave th e i n v e s t i g a t o r a f e e l for th e apparatus.
l a s t s t a g e was th e g a th e r in g o f u s e f u l data.
a t 40 d eg ree s C e ls iu s .
Here,
The
The f i r s t s e t o f data was
phenol s o l u t i o n c o n c e n t r a t io n s of 10,000
ppm, 5,000 ppm, and 2,500 ppm were i n v e s t i g a t e d over th e p ressu r e range
o f 1 ,1 0 0 p s i g t o 2 ,8 0 0 p s i g .
C e lsiu s.
The s e c o n d s e t o f d a t a was a t 60 d e g r e e s
P h e n o l s o l u t i o n c o n c e n t r a t i o n s o f 1 0 ,0 0 0 ppm and 2 ,5 0 0 ppm
w ere i n v e s t i g a t e d
over
th e
same p r e s s u r e r a n g e a s a t 40 d e g r e e s
C e lsiu s.
Experim ental Apparatus
A s c h e m a t i c o f t h e e x p e r i m e n t a l a p p a r a t u s a p p e a r s i n F i g u r e I.
The apparatus used was a s i n g l e pass flo w system .
An in v e r te d carbon
d i o x i d e g a s c y l i n d e r was u sed t o f e e d l i q u i d ca rb o n d i o x i d e t o t h e
l i q u i d s pump.
A M ilroy Model HBD-1-30R h ig h -p r e s s u r e l i q u i d pump was
used to p r e s s u r iz e th e e x t r a c t i o n c e l l and t o d e l i v e r carbon d io x id e t o
th e e x t r a c t i o n c e l l a t c o n s ta n t p r e s s u r e s .
The pump was charged w ith
a m b ie n t t e m p e r a t u r e c a r b o n d i o x i d e by a carb on d i o x i d e g a s c y l i n d e r
w h ic h was i n v e r t e d t o d e l i v e r l i q u i d s o l v e n t .
The pump's l i q u i d end
was a lw a y s p acked i n i c e t o k eep t h e c a r b o n d i o x i d e l i q u i d
in th e
pumping chamber and thus in s u r in g c o n s i s t e n t flo w by p rev en tin g a vapor
Micrometering v a lv e
Connector tube
Thermocouple
Separable vacuum trap
E le c tr ic
h e a te r s
I v e r t e d gas
c y l in d e r
Ice
bath
E x tra ctio n
bomb
' Iso la tin g
v a lv e s
P ressu re
tran sd u cer
Rupture d is c
Liquids pump
One-way
check v a lv e
H gure I .
Schematic o f phenol e x t r a c t i o n apparatus
Soapfilm
flowmeter
9
lo c k .
Pumping l i q u i d carbon d io x id e y ie ld e d c o n s i s t e n t flo w and s t a b l e
system p r e s s u r e s .
The pump was p r o te c te d by- a rupture d i s c and a one­
way check v a lv e lo c a t e d beyond th e pump and b efo re th e e x t r a c t i o n c e l l .
The e x t r a c t i o n c e l l was a o n e - l i t e r monel bomb ra ted a t 3,500 p s i
suspended in an e l e c t r i c a l l y heated oven.
Eighty p ercen t o f th e bomb's
volume was packed w ith 0.64 c e n t im e t e r ceram ic B erl s a d d le s .
This l e f t
a two hundred m i l l i l e t e r empty space and roughly a h e ig h t o f s i x c e n t i ­
m eters fo r v a p o r - liq u id disengagem ent. Oven tem perature was c o n t r o lle d
I
by e l e c t r i c a l h e a t e r s c o n t r o l l e d by a P ow erstat typ e 3PN1168 v a r ia b le
auto tra n sfo rm er.
There was a network o f v a lv e s around th e bomb which
a llo w e d fo r th e i s o l a t i o n and removal o f th e bomb w h ile under p ressu re.
A W h itey Model number SS-22RS4 m i c r o m e t e r i n g v a l v e was u sed t o
c o n t r o l p ressu r e and c o l l e c t sam ples fo r a n a l y s i s .
t h e s a t u r a t e d vap or t o a t m o s p h e r i c p r e s s u r e .
b u b b led
through
a sep a ra b le
vacuum t r a p
T h is v a lv e fla s h e d
Then t h e f l a s h e d vapor
co n ta in in g
se v e n ty -fiv e
m i l l i l i t e r s o f d e i o n i z e d w a t e r t h a t w as h e l d a t 0 d e g r e e s C e l s i u s by
means of an i c e bath.
Then th e "clean" vapor was routed through a one
hundred m i l l i l i t e r soap f i l m f l o w m e t e r and th e n t o t h e a t m o s p h e r e .
I n i t i a l l y an attem p t was made t o c o l l e c t phenol sam ples in a dry trap
h e l d a t 0 d e g r e e s C e l s i u s by an i c e b a t h .
T h is f a i l e d t o p rod u ce any
d e t e c t a b le t r a c e s of phenol in th e tra p .
T h erefo re, th e a lt e r n a t i v e
m ethod o f u s i n g d e i o n i z e d w a t e r i n t h e t r a p was e m p lo y e d ,
sa tisfa cto ry .
and was
The f a i l u r e of the f i r s t attem p t might have been caused
by th e s m a ll s i z e o f th e condensed phenol p a r t i c l e s which may have been
c a r r ie d through th e trap by th e e f f l u e n t vapor flo w .
10
System p r e s s u r e s were monitored by an A utoclave Engineers Model
DPS0081
pressure
sen sor
p ressu re tran sd u cer.
and an A u t o c l a v e
E n g in eer s
Model DPT418
The p r e s s u r e t r a n s d u c e r was lo c a t e d b efore th e
e x t r a c t i o n c e l l by r o u g h ly 1.5 m e t e r s o f t u b i n g .
A c a lc u la tio n of
p r e s s u r e drop o v e r t h i s d i s t a n c e due t o f r i c t i o n a l f l o w was made and
was n e g l i g i b l e .
Oven tem p eratu re was m onitored by a Cole Palmer Model
8530 thermometer and a therm ocouple in th e oven.
Phenol
io n a ly z e r
a n a ly sis
used
as
u se d
th e
fo llo w in g
a pH m e te r ;
e q u ip m e n t;
a B ausch
an O rion
and Lomb S p e c t r o n i c
901
2Q
sp ectop hotom eter; a m agnetic s t i r r e r ; and a mass balance.
Experim ental Procedure
P rep aration fo r an ex p erim en ta l run began th e even in g b efo re.
bomb was charged w ith f r e s h s o l u t i o n
if
n ecessa ry .
Phenol s o l u t i o n s
were prepared from rea g en t grade phenol and d e io n iz e d w ater.
n e e d e d t o be r e c h a r g e d i f
The
The bomb
t h e n e x t run r e q u i r e d a d i f f e r e n t p h e n o l
s o l u t i o n c o n c e n tr a tio n .
Charging th e bomb w ith f r e s h s o l u t i o n in volved
g r a v im e trica lly f i l l i n g
th e bomb w ith roughly s i x hundred m i l l i l i t e r s
o f th e d e s ir e d s o l u t i o n ,
p a c k in g .
w h ic h f i l l e d
t h e bomb t o t h e l e v e l o f i t s
N ext t h e bomb was cla m p ed i n t o t h e oven w h ic h had been
preheated t o th e run tem perature.
Then th e bomb was connected t o th e
sy ste m 's tu b in g and p r e s s u r iz e d w ith s a tu r a te d carbon d io x id e at room
tem p eratu re, roughly 9 0 0 . p s i.
The bomb was then s e a le d from th e system
and heated up t o th e run tem perature o v ern ig h t.
The e x p e r im e n ta l run began th e n ext morning.
used
t o . b r in g
th e
system
up t o
(
th e
o p e r a tin g
F i r s t th e pump was
pressure
and t h e n
11
m aintained a t t h i s p ressu r e fo r 15 m inutes.
Next th e bomb was i s o l a t e d
from t h e s y s t e m and rem oved from t h e oven f o r m ix i n g .
T h is m ix in g
in su red i n t im a t e v a p o r - liq u id .c o n ta c t a t op era tin g p ressu r e.
When th e
bomb reached o p e r a tin g p r e s s u r e , v i r t u a l l y a l l of th e carbon d io x id e in
t h e bomb, roughly 200 m i l l i l i t e r s ,
a t s u b -o p e r a tin g p ressu r e.
had been bubbled through th e l i q u i d
This in clu d ed th e p r e s s u r iz i n g o f th e bomb
w ith s a tu r a te d carbon d io x id e a t room tem perature and th e pumped carbon
d i o x i d e t h a t b r o u g h t t h e bomb up t o o p e r a t i n g p r e s s u r e .
A ll of t h i s
c a rb o n d i o x i d e r e m a in e d i n t h e bomb s i n c e t h e o u t l e t o f t h e bomb was
c l o s e d t o f lo w .
T h erefo re, th e vapor and l i q q i d in th e bomb needed t o
be r e - c o n t a c t e d a t o p e r a t i n g c o n d i t i o n s .
Upon r e a c h i n g o p e r a t i n g
p ressu r e and a f t e r a 15 minute w a it , th e bomb was i s o l a t e d and removed
from th e oven and shaken v ig o r o u s ly fo r roughly one m inute.
bomb was
Then th e
clamped back i n t o th e oven and opened up to t h e system .
The
bomb's drop i n p ressu r e during removal from th e oven ranged from l e s s
th a n 10 p s i up t o 50 p s i .
The l a r g e r p r e s s u r e d ro p s w e r e a s s o c i a t e d
w ith h igh er o p e r a tin g p r e s s u r e s and a l l p ressu r e drops were co rr ected
w it h in 5 m inutes.
These p ressu r e drops were probably due t o th e s l i g h t
c o o l in g o f th e bomb upon oven removal.
When the bomb p r e s s u r e had been
r e s t o r e d i t was m aintained fo r one hour.
A f t e r t h e one hour p e r i o d a s a m p le o f vapor was rea d y t o be
withdrawn.
f lo w ,
The m icrom etering v a lv e was opened t o d e l i v e r a d e s ir a b le
which ranged from 50 m i l l i l i t e r s
p er m in u t e .
per minute to 200 m i l l i l i t e r s
The p h e n o l i n t h e vap or s a m p le was c o n d e n s e d o u t o f t h e
vap or i n t h e s e p a r a b l e vacuum t r a p ,
and was a l s o d e p o s i t e d i n t h e
m icrom etering v a lv e and on th e c o n n ectin g tube.
The vapor f lo w r a t e was
12
measured w ith th e soap f i l m flo w m eter and a sto p watch.
The amount o f
carbon d io x id e from each run ranged from around 4,500 m i l l i l i t e r s
to
6,000 m i l l i l i t e r s a t ambient c o n d it io n s .
Ambient p ressu r e was recorded
a l o n g w i t h e f f l u e n t va p o r t e m p e r a t u r e .
D u rin g t h e run and t h e hour
p e r i o d b e f o r e s a m p le c o l l e c t i o n p r e s s u r e was a l w a y s h e l d t o +_ 10 p s i
and u s u a l l y h e l d t o
5 p si.
A ls o d u r in g t h i s t i m e oven t e m p e r a t u r e
was h eld t o _+ I degree C e ls iu s .
During th e ex p erim en ta l run th e phenol
s o l u t i o n was d e p le te d somewhat.
The amount of s o l u t i o n d e p le t i o n was
s m a l l due t o t h e r e l a t i v e l y l a r g e am ount o f l i q u i d s o l u t i o n and t h e
s m a ll s o l u b i l i t i e s o f phenol in th e vapor phase.
The phenol s o l u t i o n
c o n c e n t r a t io n was alw a y s w it h in 95% o f th e s t a t e d c o n c e n tr a tio n .
When t h e s a m p le had b een t a k e n ,
iso la te d
from
th e
system .
t h e m i c r o m e t e r i n g v a l v e was
Then t h e v a l v e ,
c o n n e c tin g
tu b e,
and
se p a r a b le vacuum trap were removed as a u n it , and then taken to th e lab
for
phenol rec o v ery .
Only t h e s e
c o m p o n e n ts
w ere u s e d i n p h e n o l
recovery because they were th e only components th a t were exposed to th e
p h e n o l i n t h e vap or s a m p le c o l l e c t e d d u r in g t h e run.
Here a l l t h e
components were thoroughly washed w i t h 175 m i l l i l i t e r s o f d e i o n i z e d
water and a l l o f th e w ashings p lu s th e c o n t e n t s o f th e trap were placed
i n a t i g h t l y - s e a l e d , l a b le d , and tared sample b o t t l e .
Then th e sample
b o t t l e was w e ig h e d and s t o r e d f o r l a t e r p h e n o l a n a l y s i s .
A ls o a f t e r
each run, th e 0.16 c e n t im e t e r O.D. s t a i n l e s s s t e e l tu b in g t h a t ran from
t h e bomb t o t h e m i c r o m e t e r i n g v a l v e was w ashed o u t w i t h d e i o n i z e d
w ater.
T h is i n s u r e d t h a t t h e . n e x t run w ould n o t be i n f l u e n c e d by
I
phenol t h a t might have been l e f t in th e tu b in g from th e p r e v io u s run.
13
Phenol A n a ly s is
The phenol a n a l y s i s was a d i r e c t p h otom etric method.
The a c t u a l
wet ch e m istr y i s p resen ted in Standard Methods For th e Examination o f
Water and Wastewater [11,
pp. 5 1 0 -5 1 3 ].
A s e r i e s o f phenol standards
was prepared and an alyzed by th e above procedure.
From t h i s a c a l i b r a ­
t i o n c u r v e was c o n s t r u c t e d , w h ic h p l o t t e d a b s o r b a n c e v e r s u s p h e n o l
c o n c e n t r a t io n (appendix C).
The absorbance r ea d in g s o f unknowns were
compared a g a in s t th e c a l i b r a t i o n curve and phenol c o n c e n t r a t io n s were
read d i r e c t l y o f f th e curve.
Phenol a n a ly s e s were performed on th r e e
known p r e p a r e d s o l u t i o n s and r e p e a t e d on a c o u p l e o f e x p e r i m e n t a l
sam ples in order to e v a lu a t e th e accuracy o f th e phenol a n a l y s i s .
A ll
a n a ly s e s were w it h in 5% error.
The c a l c u l a t i o n o f phenol mole f r a c t i o n in th e vapor samples was
accom plished by i n d i v i d u a l l y c a l c u l a t i n g th e amounts o f carbon d io x id e
and p h e n o l.
The amount o f p h e n o l was c a l c u l a t e d from kn ow ing t h e
phenol c o n c e n tr a tio n o f th e c o l l e c t e d w ater sample and i t s
amount o f
carbon d io x id e
was c a l c u l a t e d
from t h e i d e a l
mass.
The
g a s la w .
Ambient tem perature and p ressu r e were known along w ith sample volume.
Reagents
A ll c h e m ic a ls used were reagen t grade ex ce p t carbon d io x id e .
ca rb o n d i o x i d e was w e l d i n g g ra d e and was 99.9% p u re.
was d e io n iz e d .
The
The w a t e r u sed
14
RESULTS AND DISCUSSION
General O b servation s
Phenol s o l u b i l i t i e s were measured a t a c o n s ta n t tem perature and a t
a c o n s ta n t phenol s o l u t i o n c o n c e n t r a t io n over a range of p r e s s u r e s .
As p r e v i o u s l y m e n t io n e d t h e d e p l e t i o n o f p h e n o l d u r in g a run ch anged
th e aqueous phenol c o n c e n t r a t io n l e s s
b e f o r e p h e n o l a n a l y s i s by t h e d i r e c t
th a n 5%.
A ls o a s m e n tio n e d
p h o t o m e t r i c m ethod p roduced
r e s u l t s w ith l e s s than 5% e r r o r .
The c r i t i c a l p r o p e r t ie s o f th e s u p e r c r i t i c a l phase m ixtu re (Tc, Pc)
w ere assu m ed t o be i d e n t i c a l t o t h o s e o f pure c a rb o n d i o x i d e (Tc = 31
degrees C e lsiu s,
Pc = 1070 p s i a ) and u n a f f e c t e d by t h e p r e s e n c e o f
phenol and water s i n c e th ey were in such s m a ll c o n c e n t r a t io n s .
Experim ental S o l u b i l i t i e s
The primary o b j e c t i v e of t h i s re se a r c h was to measure e x p erim en ta l
s o l u b i l i t y data fo r phenol in s u p e r c r i t i c a l carbon d io x id e from aqueous
phenol s o lu t io n s .
eq u ilib r iu m
r u n s w ere t e m p e r a t u r e , p r e s s u r e ,
c o n cen tra tio n .
m illio n ,
The p a r a m e t e r s s t u d i e d d u r in g t h e s e v a p o r - l i q u i d
and p h e n o l s o l u t i o n
S o l u t i o n c o n c e n t r a t i o n s w ere r e p o r t e d i n p a r t s p er
ppm, which was a w eigh t r a t i o (e.g. 10,000 ppm was I w eigh t %
p h e n o l) .
The r e p o r t e d p h e n o l s o l u b i l i t i e s
d egrees C e ls iu s and 60 d egrees C e l s i u s ,
i n t h e vap or p h a s e .
w ere f o r t e m p e r a t u r e s o f 40
and were mole f r a c t i o n phenol
Each e x p e r i m e n t a l run was d u p l i c a t e d and t h e
d i f f e r e n c e between, r e p l i c a t e s averaged 17%.
15
Data a t 40 Degrees C e ls iu s
The phenol s o l u b i l i t i e s fo r 40 d eg ree s C e ls iu s are l i s t e d in Table
I.
T his data in c l u d e s th e v a lu e s fo r each ex p erim en ta l r e p l i c a t e and
th e average.
For t h i s tem perature th e f o l l o w i n g th r e e phenol s o l u t i o n
c o n c e n t r a t i o n s w ere i n v e s t i g a t e d :
ppm.
1 0 ,0 0 0 ppm; 5 , 0 0 0 ppm; and 2 ,5 0 0
The p r e s s u r e r a n g e i n v e s t i g a t e d
for
each of t h e s e s o l u t i o n
c o n c e n t r a t i o n s was 1 ,1 0 0 p s i g t o 2 ,8 0 0 p s i g . The a v e r a g e v a l u e s f o r
each d u p lic a te d experim ent are p l o t t e d in Figure 2.
The e f f e c t o f p r e s s u r e upon vap or p h a se p h e n o l s o l u b i l i t y was
c o n s i s t e n t among th e t h r e e phenol s o l u t i o n c o n c e n t r a t io n s .
phase phenol s o l u b i l i t y in c r e a se d s i g n i f i c a n t l y
o f 1,100 p s ig t o 2,000 p s ig .
so lu b ility
The vapor
in th e p ressu r e range
Beyond 2,000 p s ig th e vapor phase phenol
l e v e l e d o f f i n d i c a t i n g a much weaker f u n c t io n of p ressu re.
Figure 2 a l s o shows t h a t in c r e a se d phenol s o l u t i o n c o n c e n t r a t io n gave
la r g e r vapor phase phenol s o l u b i l i t i e s . t
The e f f e c t
o f p r e s s u r e on vap or p h a se p h e n o l s o l u b i l i t y
was
s i m i l a r t o i t s e f f e c t on s u p e r c r i t i c a l carbon d io x id e d e n s it y (Figure
3).
The d e n s it y in c r e a s e d r a p id ly w ith in c r e a se d p r e ssu r e in the same
p ressu r e range as did vapor phase phenol s o l u b i l i t y .
A lso th e d e n s it y
s t a r t e d t a p e r i n g o f f a t r o u g h ly t h e same p r e s s u r e a s d id t h e vapor,
phase phenol s o l u b i l i t y .
I t was apparent t h a t in c r e a se d d e n s it y in th e
vapor phase r e s u l t e d in in c r e a se d s o l u t e s o l u b i l i t y in th e vapor phase.
Table I .
P re ss
(Ps I r )
1100
1200
1400
1800
2600
Mole F r a c tio n Phenol in S u p e r c r i t i c a l Carbon D io x id e a t 40 d egrees C e ls iu s
10,000 ppm
Mole F r a c t i o n Phenol
Rx p . I
0 .0 0 0 0 9 5
0 .0 0 0 2 6
0 .0 0 0 3 4
0.00051
0 .0 0 0 8 0
Exp. 2
0 .0 0 0 1 3
0 .0 0 0 2 2
0 .0 0 0 3 2
0 .0 0 0 8 7
0 .0 0 0 8 3
Ave.
0.00011
0 .0 0 0 2 4
0 .0 0 0 3 3
0 .00069
0 .0 0 0 8 2
P re ss
(Ps I r )
1100
1200
1400
1700
2000
2800
5,000 ppm
Mole FracLion Phenol
Exp. I
0 .0 0 0 1 2
0 .0 0 0 2 0
0 .0 0 0 1 6
0 .0 0 0 2 5
0 .0 0 0 5 7
0 .0 0 0 6 0
Exp. 2
0 .0 0 0 0 8 6
0 .0 0 0 1 9
0 .0 0 0 2 2
0 .0 0 0 3 4
0 .0 0 0 3 9
0.00041
Ave.
0 .0 0 0 1 0
0 .0 0 0 2 0
0 .0 0 0 1 9
0 .0 0 0 3 0
0 .0 0 0 4 8
0 .00051
2 ,5 0 0 ppm
P re ss
(Psifi)
1100
1200
1400
1700
2000
2800
Mole F r a c t i o n Phenol
Exp. I
Exp. 2
Ave.
0.000069
0.000071
0.000070
0.000048
0.000068
0.000058
0.000096
0.00011
0.00010
0.00013
0.00015
0.00014
0.00018
0.00019
0.00019
0.00019
0.00027
0.00023
Mole f r a c t i o n p h e n o l ( v a p o r p h a s e )
10 - 3
10
-14
1200
1500
1800
2100
2 IiOO
2700
P ressu re (p sig )
F ig u re 2.
E x p e rim en ta l v ap o r p hase p h en o l s o l u b i l i t i e s in s u p e r c r i t i c a l carbon d io x id e a t
UO d e g r e e s C e l s i u s
3000
(g /m l)
S u p e r c r i t i c a l carbon d io x id e d e n s it y
0.20
1200
1500
180O
2100
2400
2700
3000
P ressu re (p sia)
F ig u re 3.
S u p e r c r i t i c a l c a r b o n d i o x i d e d e n s i t y a s a f u n c t i o n o f p r e s s u r e a t 40 and 60 d e g r e e s C e l s i u s
19
D a ta a t 60 D eR rees C e l s i u s
The v a p o r
phase
a p p e a r s i n T a b l e 2.
phenol
so lu b ility
d a ta
The p h e n o l s o l u t i o n
at
60 d e g r e e s C e l s i u s
c o n c e n tra tio n s
in v e s tig a te d
w e re 1 0 ,0 0 0 ppm and 2 ,5 0 0 ppm o v e r t h e p r e s s u r e r a n g e o f 1 ,1 0 0 p s i g t o
2 ,8 0 0 p s i g .
At
T h is d a ta i s
60
d eg rees
p lo tte d
C e lsiu s
i n F i g u r e 4.
th e
b e h a v io r
of
vapor
s o l u b i l i t y a s a f u n c t i o n o f p r e s s u r e was d i s t i n c t l y
b e h a v i o r o b s e r v e d a t 40 d e g r e e s C e l s i u s .
phase
d iffe re n t
phenol
th a n t h e
B o th t h e F i g u r e 4 c u r v e s a t
60 d e g r e e s C e l s i u s showed a minimum i n v a p o r p h a s e p h e n o l s o l u b i l i t y a t
th e lo w e r
pressures,
w h ic h was u n e x p e c t e d .
T h i s b e h a v i o r was c l e a r l y
shown f o r t h e d a t a c o l l e c t e d fro m t h e 2 ,5 0 0 ppm a q u e o u s p h e n o l s o l u t i o n
w hich had n e a r l y t w i c e a s many p o i n t s a s t h e 1 0 ,0 0 0 ppm s o l u t i o n .
T ab le 2.
M o le F r a c t i o n P h e n o l i n S u p e r c r i t i c a l C a r b o n D i o x i d e a t 60
____________ D e g r e e s C e l s i u s .
________________________________________________
1 0 ,0 0 0 ppm
Mole F r a c t i o n P h e n o l
P ress
A ve.
Exp. 2
( P s i g ) I Exp. I
0
.0
0012
0 .0 0 0 1 1
1100 0 .0 0 0 1 3
0
.0
0
0097
1200 0 .0 0 0 0 9 4 0 .0 0 0 1 0
0
.0
0
0078
0
.0
0
0
0
8
4
1400 0 .0 0 0 0 7 2
0
.0
0
012
0 .0 0 0 1 4
1600 0 .0 0 0 1 0
0
.0
0
017
0
.0
0
0
1
5
2000 0 .0 0 0 1 8
0
.0
0
0
3
7
0
.0
0
034
0
.0
0
0
3
0
2700
The r e a s o n s
d e p re ssio n s
w ere
2 ,5 0 0 ppm
;
Mole
F r a c t i o n Phenol
Press
A ve.
Exp. 2
( P s i g ) Exp. I
0 .0 0 0 0 9 9
1100 0 .0 0 0 0 9 7 0 .0 0 0 1 0
1200 0 .0 0 0 0 8 8 0 .0 0 0 0 7 2 0 .0 0 0 0 8 0
1300 0 .0 0 0 0 8 3 0 .0 0 0 0 7 3 0 .0 0 0 0 7 8
1400 0 .0 0 0 0 6 2 0 .0 0 0 0 6 0 0 .0 0 0 0 6 1
1550 0 .0 0 0 0 5 5 0 .0 0 0 0 6 7 0 .0 0 0 0 6 1
1650 0 .0 0 0 0 5 8 0 .0 0 0 0 6 5 0 .0 0 0 0 6 2
1800 0 .0 0 0 0 6 8 0 .0 0 0 0 8 1 0 .0 0 0 0 7 5
1950 0 .0 0 0 0 6 8 0 .0 0 0 0 8 2 0 .0 0 0 0 7 5
2100 0 .0 0 0 0 7 6 0 .0 0 0 0 8 6 0 .0 0 0 0 8 1
0 .0 0 0 1 1
2300 0 .0 0 0 0 9 4 0 .0 0 0 1 2
0 .0 0 0 1 4
0 .0 0 0 1 2
2800 0 .0 0 0 1 5
why v a p o r p h a s e p h e n o l s o l u b i l i t y e x p e r i e n c e d t h e s e
not
u n d e rsto o d
d e s c rib e d in th e n ex t s e c tio n .
and
led
to
th e
m o d e lin g
stu d ie s
T he d e n s i t y v e r s u s p r e s s u r e b e h a v i o r
Mole f r a c t i o n p h e n o l ( v a p o r p h a s e )
1200
2100
P re ssu re (p sig )
F ig u re
4.
E x p e r i m e n t a l v a p o r p h a s e p h e n o l s o l u b i l i t i e s i n s u p e r c r i t i c a l c a rb o n d i o x i d e a t
60 d e g r e e s C e l s i u s
21
fo r carbon d io x id e a t 60 d egrees C e ls iu s was s i m i l a r t o th e curve a t 40
d e g r e e s C e ls iu s (F ig u r e 3).
O b v io u s ly a d i f f e r e n t t y p e o f phenomena
was ta k in g p la c e a t 60 d egrees C e l s i u s than was a t 40 d eg ree s C e ls iu s .
The e f f e c t s o f phenol s o l u t i o n c o n c e n tr a tio n on vapor phase phenol
s o l u b i l i t y were s i m i l a r t o th e e f f e c t s a t 40 d egrees C e ls iu s .
phenol s o lu t io n
co n c e n tr a tio n s
gave
la r g e r
vapor
p h ase
Larger
phenol
so lu b ilitie s.
A ll o f t h e data a t 40 and 60 d eg ree s C e ls iu s are p l o t t e d in Figure
5.
The major e f f e c t s o f tem perature on vapor phase phenol s o l u b i l i t i e s
w ere t h e minimum s o l u b i l i t i e s o b s e r v e d a t 60 d e g r e e s C e l s i u s .
The
o t h e r t e m p e r a t u r e e f f e c t i n v o l v e d t h e r e l a t i v e m a g n it u d e s o f vapor
phase phenol s o l u b i l i t i e s ; th e h igher tem perature o f 60 d eg ree s C e ls iu s
gave low er v a lu e s of vapor phase phenol s o l u b i l i t y than did 40 degrees
C e ls iu s .
This was probably due t o th e decreased carbon d io x id e d e n s it y
a t h igh er tem p era tu res (Figure 3).
Thermodynamic Modeling
Modeling
A model o f th e aqueous p h e n o l - s u p e r c r i t i c a l carbon d io x id e system
was developed t o c a l c u l a t e th e sy ste m 's v a p o r - liq u id e q u ilib r iu m .
model c o n s i s t e d o f t h r e e s o l u t i o n component f u g a c it y e q u a tio n s .
The
Each
eq u ation in v o lv e d s e t t i n g the' component f u g a c it y in th e s u p e r c r i t i c a l
s t a t e e q u a l t o t h e c o r r e s p o n d i n g com p on en t f u g a c i t y i n t h e l i q u i d
Mole f r a c t i o n p h e n o l (v a p o r p h a s e )
10
-3
O
1 0 ,0 0 0 ppm, Uo0 C
□
5 ,0 0 0 ppm, U0°C
O
rv>
ro
10
-I*
— I-------------------------- 1-------------------------- 1-------------------------- 1--------------------------1-------------------------- 1_____________
1200
F ig u re 5.
1500
1800
2100
P re ssu re (p sig )
2U00
2700
I
3000
E x p e rim en ta l v apor p hase p h enol s o l u b i l i t i e s in s u p e r c r i t i c a l carbon d io x id e a t
Uo a n d 60 d e g r e e s C e l s i u s
23
phase,
which i s a thermodynamic c r i t e r i o n fo r phase e q u ilib r iu m .
The
th r e e eq u a tio n s are l i s t e d below.
!)
7 1 0 1 p = xl 7 1 / l °
2)
y202 P =
Where:
yj_ = Mole f r a c t i o n o f "i" in vapor phase
t . = Vapor phase component f u g a c it y c o e f f i c i e n t o f "i"
P = System p ressu re
= Mole f r a c t i o n o f "i" in l i q u i d phase
"Tjl = A c t i v i t y c o e f f i c i e n t o f "i" in l i q u i d phase
= Standard s t a t e f u g a c it y o f "i"
= H enry's law c o e f f i c i e n t o f "i"
P h e n o l i s d e n o t e d by t h e s u b s c r i p t I , w a t e r i s d e n o t e d by 2, and
s u p e r c r i t i c a l c a rb o n d i o x i d e i s d e n o t e d by 3.
The unknowns i n t h e s e
e q u a t i o n s w ere vap or p h a se m ole f r a c t i o n s and vap or p h a s e com ponent
fu g a c ity
c o e ffic ie n ts.
The com p on en t f u g a c i t y
c o e ffic ie n ts
w ere
c a l c u l a t e d u sin g th e Peng-Robinson eq u a tio n of s t a t e (appendix A) and
were f u n c t io n s o f vapor phase mole f r a c t i o n s , tem p eratu re, and p ressure
[12,
p.
205].
T hree-com ponent
d ata
for
liq u id
phase
a c tiv ity
c o e f f i c i e n t s and fo r carbon d i o x i d e s o l u b i l i t i e s i n t h e l i q u i d p h a se
w ere n o t a v a i l a b l e .
H o w ev er, t w o - c o m p o n e n t W ils o n p a r a m e t e r s f o r
phenol and water a t low p r e s s u r e s were a v a i l a b l e t o c a l c u l a t e l i q u i d
p h a se a c t i v i t y
c o e ffic ie n ts
e q u a t i o n [ 1 3 , pp. 7 5 4 - 7 5 7 ] .
f o r p h e n o l and w a t e r fr o m t h e W ils o n
T h ese c a l c u l a t e d a c t i v i t y c o e f f i c i e n t s
ignored th e e f f e c t s of d is s o l v e d carbon d io x id e in th e l i q u i d phase and
4*
24
the e f f e c t s
o f the s yst em 's high p re s s u r es .
a t e l e v a t e d p r e s s u r e s were a v a i l a b l e
dioxide
Henry's law c o e f f i c i e n t s
f o r carbon d i o x i d e and water t o
calcu late
c ar b on
so lu b ilities
in
the
liq u id
p h as e
[14,
p. 3 - 9 6 ] .
T h e s e c a l c u l a t e d c ar b o n d i o x i d e s o l u b i l i t i e s i g n o r e d t h e
e f f e c t s of phenol in the l i q u i d phase.
I t was f e l t
th is
l a c k o f d a t a f o r t h e t h r e e com p on en t l i q u i d
s o l u t i o n woul d n o t p r e v e n t t h e p r e d i c t i o n o f t r e n d s f o r t h e p h e n o l
s o l u b i l i t i e s in th e s u p e r c r i t i c a l phase.
I t i s u n lik e ly the sm a ll
amount o f d i s s o l v e d c a r b o n d i o x i d e ( l e s s t ha n 4 mole %) would a f f e c t
the w ater-phenol in t e r a c t io n s ;
t h e p h e n o l h as l i t t l e
tendency to
i n t e r a c t w i t h t h e c a r b o n d i o x i d e and i s a l s o p r e s e n t i n v e r y s m a l l
concentrations
( l e s s th a n 0.2 m o le %).
A lt h o u g h t h e p h e n o l - w a t e r
a c t i v i t y c o e f f i c i e n t data was at s m a l l p r e s s u r e s (2-14.7 p s i a ) r e l a t i v e
t o system p r e s s u r e s (up t o 2800 p s i g ) i t should be only weakly a f f e c t e d
s i n c e t h e a c t i v i t y c o e f f i c i e n t i s a weak f u n c t i o n o f p r e s s u r e .
A
d e t a i l e d o u t l i n e of eq ua tio n d e r i v a t i o n and re f e re n ce d data appears in
appendix A.
The com po nen t f u g a c i t y e q u a t i o n s w e r e s o l v e d u s i n g a t r i a l and
error computation t h a t s a t i s f i e d a l l t h r e e eq u a tio n s.
I n i t i a l l y an attem pt was made t o s o l v e the thermodynamic model by
u s i n g a l l t h r e e o f t h e com po ne nt f u g a c i t y e q u a t i o n s .
The s o l u t i o n s
generated by t h i s method gave vapor phase co m p o s it io n s whose sums were
g r e a t e r than one and t h i s was co r r e c t e d by n or m al iz in g t h e vapor phase
com position.
U n f o r t u n a t e l y b e c a u s e t h e s e sums were l a r g e r than one,
25
t h e method o f s o l u t i o n u s i n g a l l
t h r e e o f t h e com ponent f u g a c i t y
e q u a t i o n s became i n d e t e r m i n a t e a t e l e v a t e d . p r e s s u r e s a s d e s c r i b e d
b el o w .
There was a term i n the Peng-Robinsbn equation o f s t a t e t h a t took
the
natural
logarith m
of
a d ifferen ce
in v o lv in g
c o m p r e s s i b i l i t y and vapo r p h a s e c o m p o s i t i o n .
vapor
phase
For in c r e a s e d pr essure
t h i s d i f f e r e n c e became s m a l l e r b e c a u s e t h e v a l u e o f t h e vap or p h as e
ca rbo n d i o x i d e - m o l e f r a c t i o n became g r e a t e r t h a n one and grew w i t h
increased
pressure.
F inally
a
pressure
was
reached
where
the
d i f f e r e n c e became z e r o or n e g a t i v e and t h e e q u a t i o n o f s t a t e became
indeterm inate.
T h i s o c c u r r e d i n t h e m i d d l e o f t h e p r e s s u r e ra ng e o f
t h e e x p e r i m e n t a l d a t a a t b o t h 40 and 60 d e g r e e s C e l s i u s and t h u s , i t
was n o t s a t i s f a c t o r y
for
comparison
w ith
the e x p e r im e n ta l
data.
Therefore t h i s method of s o l u t i o n i n v o l v i n g a l l t h re e of the component
fu gacity
equations
was
abandoned
and
an a l t e r n a t i v e
method
was
developed.
The s e c o n d method u s e d t h e p h e n o l and w a t e r co m p on en t f u g a c i t y
e q u a t i o n s and a vap or p h a s e mole' b a l a n c e t h a t s e t t h e sum o f t h e
component vapor phase mole f r a c t i o n s equal t o one.
The s u p e r c r i t i c a l
c a r b o n d i o x i d e com ponent f u g a c i t y e q u a t i o n was r e p l a c e d by t h e mole
balance because i t was cau sin g the i n d e t e r m i n a t e s o l u t i o n s .
This a l t e r n a t i v e method c a l c u l a t e d vapor phase phenol s o l u b i l i t i e s
fo r the e n t i r e p r e s s u r e range (0-2800 p s ia ) .
A c o m p a r i s o n o f t h e tw o
methods showed they were s i m i l a r over p res su re where they both could be
used;
therefore
t h e s e c o n d method was s e l e c t e d
for
the modeling
26
s tu d ie s.
A p p e n d ix B show s t h i s c o m p a r i s o n o f t h e tw o m e th o d s and a l s o
c o n t a i n s t h e c o m p u t e r p r o g ra m u s e d t o c a l c u l a t e t h e s e c o n d m ethod.
Modeling R e s u l t s
The e x p e r i m e n t a l vapor p h a s e p h e n o l s o l u b i l i t i e s a t 40 d e g r e e s
C e l s i u s and phenol s o l u t i o n c o n c e n t r a t i o n s of 10,000 ppm and 2,500 ppm
are
p lotted
again st
th eir
corresponding
thermodynamic model i n Figure 6.
data
generated
by
the
In Figure 7 the same ex p er im en ta l and
model-generated data i s p l o t t e d f o r 60 degre es C e l s i u s .
A l l of t h e model-generated data a t both 40 degre es C e l s i u s and 60
degre es C e l s i u s showed a minimum i n vapor phase phenol s o l u b i l i t y a t
lower p ressu r es.
At 40 d e g r e e s C e l s i u s t h e minimums i n vap or p ha se
phenol s o l u b i l i t i e s
o c c u r r e d around 600 p s i a w h i l e a t 60 d e g r e e s
C e l s i u s the minimums occurred around 700 p s i a .
The m ol e f r a c t i o n o f p h e n o l i n t h e s u p e r c r i t i c a l p h a s e was t h e
x i x Xi Y i x exp
product of four terms:
Cf)±
The f i r s t t e r m , c a l l e d t h e i d e a l s o l u b i l i t y ,
p h a s e p h e n o l mo le f r a c t i o n
was i n v e r s e l y
p res su re a t co n s t a n t temperature.
- A (P - Pi SAT)
RT
showed t h a t t h e vapor
prop ortion al
to
system
The t h i r d term was th e l i q u i d phase
a c t i v i t y and was assumed t o be a f u n c t i o n of co m p os iti o n and tempera­
ture only.
The f o u r t h term was t h e P o y n t i n g c o r r e c t i o n and measured
t h e e f f e c t of p re s s ur e upon the l i q u i d phase f u g a c i t y .
The second term
was the i n v e r s e of the vapor phase component f u g a c i t y c o e f f i c i e n t which
r e f l e c t e d t h e n o n - i d e a l i t y o f t h e v a p o r - p h a s e m i x t u r e o f s o l u t e and
solven t.
At l o w p r e s s u r e t h i s ter m was c l o s e t o u n i t y but became
Mole f r a c t i o n p h e n o l ( v a p o r p h a s e )
1200
F ig u re 6.
1600
P ressu re (p sia)
Thermodynamic m o d e l - g e n e r a t e d v a p o r p h a s e p h e n o l s o l u b i l i t i e s and e x p e r i m e n t a l p h e n o l
s o l u b i l i t i e s i n s u p e r c r i t i c a l c a r b o n d i o x i d e a t 1*0 d e g r e e s C e l s i u s
Mole f r a c t i o n p h e n o l ( v a p o r p h a s e )
1200
1600
2000
P ressu re (p sia)
F ig u re 7.
Thermodynamic m o d e l - g e n e r a t e d v a p o r p h a s e p h e n o l s o l u b i l i t i e s and e x p e r i m e n t a l p h e n o l
s o l u b i l i t i e s i n s u p e r c r i t i c a l c a r b o n d i o x i d e a t 60 d e g r e e s C e l s i u s
s m a l l e r w i t h high er pressures' and thus gave l a r g e r vapor phase phenol
m ole f r a c t i o n s .
The m o d e l - g e n e r a t e d c u r v e s showed d e c r e a s i n g vapor
phase phenol mole f r a c t i o n w it h i n c r e a s i n g pres sur e a t low p re s s u r es ,
r e f l e c t i n g th e e f f e c t o f the f i r s t term or the i d e a l s o l u b i l i t y .
When
the p re ss ur e reached around 600 p s i a the vapor phase component f u g a c i t y
c o e f f i c i e n t began t o d ec r e a se s i g n i f i c a n t l y and caused the vapor phase
phenol
m o le
in crease.
fraction
N either
activ ity
to
p a s s t h r o u g h a minimum and c o n t i n u e
the Poynting
correction
nor
the
liq u id
to
p h as e
p l a y e d an i m p o r t a n t r o l e i n d e t e r m i n i n g t h e s h a p e s o f t h e
vapor phase phenol mole f r a c t i o n d e p r e s s i o n s generated by the model.
For b o t h t e m p e r a t u r e s t h e model p r e d i c t e d h i g h e r vapor p h a s e
phenol s o l u b i l i t i e s fo r l a r g e r p h e n o l s o l u t i o n c o n c e n t r a t i o n s .
This
was a d i r e c t r e s u l t o f t h e m o le f r a c t i o n p h e n o l b e i n g l a r g e r i n t h e
phenol f u g a c i t y equation.
M odel-generated data d i f f e r e d
Figures
6 and
so lu b ility
7 in
three
was p r e d i c t e d
temperature,
from t h e e x p e r i m e n t a l d a t a i n
respects:
(I)
the
vapor
p h a se
p h en o l
b y . t h e model t o i n c r e a s e f o r i n c r e a s i n g
(2) the p r e d ic te d phenol s o l u b i l i t i e s were four to e i g h t
t i m e s s m a l l e r than the ex p er im en ta l s o l u b i l i t i e s at 40 d egr ee s C e l s i u s ,
and (3) the p r e d i c t e d and ex p er i m en t al minimums i n phenol s o l u b i l i t y
occurred
at
d ifferen t
pressure
region s
a t 60 d e g r e e s C e l s i u s .
I n c r e a s e d p h e n o l s a t u r a t i o n p r e s s u r e s due t o i n c r e a s e d t e m p e r a t u r e
caused the p r e d ic t e d vapor phase phenol s o l u b i l i t i e s t o i n c r e a s e w it h
in creased
tem perature.
The o t h e r
two d i s c r e p a n c i e s
betw een
e x p e r i m e n t a l and m o d e l - g e n e r a t e d d a t a m ig h t ha ve b ee n c a u s e d by t h e
30
replacement of u n a v a il a b le three-component data with two-component data
as p r e v i o u s l y d i s c u s s e d .
Table
3 co n ta in s
m od el-gen erated
v alu es
of
vapor
phase
co m p o s it io n , vapor phase component f u g a c i t y c o e f f i c i e n t s , and Poynting
c o r r e c t i o n s for phenol and water for t h e i r r e s p e c t i v e p r e s s u r e s at 60
d egr ee s C e l s i u s and 10,000 ppm phenol s o l u t i o n c o n c e n t r a t i o n .
Table 3 .
Aqueous P h e n o l - S u p e r c r i t i c a l Carbon Dioxide Model Calcu lat ed
V a l u e s o f Mole F r a c t i o n s i n t h e Vapor P h a s e , Vapor Phas e
Component Fugacity C o e f f i c i e n t s , and P o i n t i n g C o rr ec t io n s for
P h e n o l and Water a t 60 d e g r e e s C e l s i u s and P h e n o l S o l u t i o n
___________ C onc entration of 10,000 ppm_______________________________________
Pr e ss
(Psia)
10
50
100
200
400
600
800
1000
1100
1200
1300
1400
1600
1800
2000
2200
2400
2600
2800
3000
Vapor Phase Comp,
(mole f r a c t i o n )
Phenol
Water
0.290
0. 002 2
0.00047
0.059
0.030
0. 00025
0. 00014
0 .0 1 6
0.0087
0.000093
0 .0 0 64
0.000082
0.000083
0 .0 053
0 .0 0 48
0.000091
0 .0 046
0.000096
0.00011
0 . 004 5
0.00012
0.004 5
0. 00013
0 . 004 5
0.00017
0.0047
0. 00022
0 . 004 9
0. 00 028
0.0051
0. 000 28
0 . 0 0 53
0. 000 30
0 . 0 0 55
0. 00032
0 . 005 6
0.005 7
0. 00033
0.005 7
0. 000 35
Vapor Phase
Fug acity C o e f f .
Phenol
Water
0. 9 8 8
0. 9 9 5
0.9 7 8
0. 9 4 9
0.901
0.961
0.810
0 .9 2 3
0.8 4 8
0 .6 5 0
0. 7 7 4
0 .5 1 4
0.70 2
0.400
0.630
0. 3 0 5
0. 2 6 4
0.59 5
0.226
0. 5 5 9
0. 5 2 3
0. 1 9 3
0. 4 8 7
0.163
0. 1 1 6
0. 4 1 6
0. 3 5 4
0.085
0.307
0.068
0.058
0.27 2
0.24 5
0. 0 5 2
0. 0 4 7
0. 2 2 4
0.044
0. 2 0 6
0.19 2
0.042
Poynting Correction
Phenol
1 .0 0
1.01
1.02
1.0 5
1.09
1.1 4
1 .2 0
1.2 5
1.2 8
1.31
1.34
1.37
1 .4 3
1 .5 0
1.57
1.6 4
1.71
1 .7 9
1.87
1.9 6
Water
1.0 0
1.00
1.00
1.01
1.02
1.03
1.04
1.05
1.05
1.06
1.06
1.07
1.08
1.09
1.10
1.11
1.12
1.13
1.14
1.15
31
D e s ig n C o n s i d e r a t i o n s
T his
sectio n
of
the
resu lts
and d i s c u s s i o n
presents
the
ex p er im en ta l v a p o r - l i q u i d e q u il i b r iu m data in a form t h a t could be used
in p r e d i c t i n g the s y s t e m ' s e x t r a c t i o n c a p a b i l i t i e s .
E q u i l i b r i u m p h e n o l m ole f r a c t i o n s i n t h e l i q u i d p h as e and t h e
s u p e r c r i t i c a l carbon d i o x i d e phase are in Table 4 w it h sy stem pressure
and c a l c u l a t e d d i s t r i b u t i o n c o e f f i c i e n t s or eq u il i b r iu m K-values at 40
degrees C elsiu s.
Figure 8 c o n ta in s cu rves of phenol d i s t r i b u t i o n
c o e f f i c i e n t s v e r s u s p r e s s u r e f o r t h r e e d i f f e r e n t l i q u i d phase phenol
mole f r a c t i o n s a t 40 degre es C e l s i u s .
Figure 8 shows t h a t the phenol
d i s t r i b u t i o n c o e f f i c i e n t v ersu s system pressure p l o t s for the th r e e
Table 4.
E x p e r i m e n t a l Mole F r a c t i o n s o f Ph en o l i n Water, Mole
F r a c t i o n s o f P h en o l i n S u p e r c r i t i c a l Carbon D i o x i d e , and
___________ Equilibrium K-values a t 40 d egr ee s C e l s i u s _____________ _________
Mole F r a c t io n s Phenol
Press
( psig)
1100
1100
1100
1200
1200
1200
1400
1400
1400
1700
1700
1800
2000
2000
2600
2800
2800
Liquid Phase
X
0 . 0 0 19
0. 00096
0 .0 004 8
0.001 9
0. 00 096
0. 00048
0 .0 019
0. 00096
0. 00048
0. 00096
0. 00 048
0. 0019
0. 00096
0. 00048
0 . 001 9
0. 00096
0. 00048
S u p e r c r i t i c a l Phase
y
K-values
y/x
0.00011
0. 00010
0.000070
0.00024
0. 00020
0.000058
0. 00033
0.00019
0. 00010
0. 00030
0. 00014
0.00069
0. 00048
0.00019
0.00082
0.00051
0. 00023
0.05 8
0.08 9
0 .1 6
0 .1 3
0.20
0.13
0. 17
0 .2 3
0 .2 2
0.31
0.31
0 .3 6
0.50
0.4 2
0.43
0 .5 3
0.51
K -c a lc u la te d d i s t r ib u t io n c o e f f ic ie n t
y = m ole f r a c t i o n o f p h e n o l i n c a r b o n d i o x i d e
x = m ole f r a c t i o n o f p h e n o l i n l i q u i d p h a s e
K = y /x
0.0019
1200
2100
P ressu re (p sig )
F ig u re 8.
C a l c u l a t e d d i s t r i b u t i o n c o e f f i c i e n t s o f p h e n o l from e x p e r i m e n t a l d a t a f o r s y s te m p r e s s u r e
a t Uo d e g r e e s C e l s i u s
33
l i q u i d p h as e p h e n o l m o le f r a c t i o n s w ere c l o s e t o g e t h e r a t t h e l o w e r
system p r e s u r e s .
Table 5 c o n t a i n s the ex p er i m en t al e q u il i b r iu m mole f r a c t i o n s of
phenol in the l i q u i d phase and s u p e r c r i t i c a l carbon d i o x i d e phase with
system p res su re and c a l c u l a t e d phenol d i s t r i b u t i o n c o e f f i c i e n t s a t 60
degrees C elsiu s.
F ig u r e 9 shows the p l o t s of phenol d i s t r i b u t i o n
c o e f f i c i e n t v e r s u s system pres sur e fo r the two d i f f e r e n t l i q u i d phase
phenol mole f r a c t i o n s at 60 d egr ee s C e l s i u s .
distribution co efficien t
Figure 9 shows t h a t the
as a f u n c t i o n o f pres sur e a t c o n s t a n t l i q u i d
phase phenol mole f r a c t i o n p a s se s through a minimum at the lower system
p r e s s u r e s fo r both l i q u i d phase phenol mole f r a c t i o n s .
Table 5.
E x p e r i m e n t a l Mole F r a c t i o n s o f Ph en o l i n Water, Mole
F r a c t i o n s o f P h e n o l i n S u p e r c r i t i c a l Carbon D i o x i d e , and
___________ Equilibrium K-values a t 60 d egr ee s C e l s i u s
Mole F r a c t io n s Phenol
Press
(psig)
1100
1100
1200
1200
1300
1400
1400
1550
1600
1650
1800
1950
2000
2100
2300
2700
2800
Liquid Phase
x
0.001 9
0. 00048
0 . 001 9
0. 00048
0. 00048
0 .0 019
0. 00048
0. 00048
0 .0 019
0. 00048
0. 00048
0. 00048
0 . 0 0 19
0.00048
0. 00 048
0. 0019
0. 00 048
S u p e r c r i t i c a l Phase
_________ Y_________
0.00012
0. 000099
0.000097
0. 000080
0. 000078
0.000078
0.000061
0.000061
0. 00 01 2
0.000062
0. 000075
0. 000075
0. 00017
0.000081
0.00011
0 .0 00 34
0. 00014
K-values
y/x
0.0 6 3
0 .2 2
0.051
0.18
0.1 7
0.041
0 .1 4
0 .1 4
0. 0 6 3
0 .1 4
0 .1 7
0.1 7
0.0 9 0
0.18
0.24
0.18
0.31
K -c a lc u la te d d i s t r i b u t i o n c o e f f ic i e n t s
m ole f r a c t i o n o f p h e n o l i n c a r b o n d i o x i d e
m ole f r a c t i o n o f p h e n o l i n l i q u i d p h a s e
K = y /x
0.20
0.10
0 .0 0 1 9
x = 0 .0 0 0 4 8
1200
2100
P ressure
F ig u re 9.
(p sig )
C a l c u l a t e d d i s t r i b u t i o n c o e f f i c i e n t s o f p h e n o l from e x p e r i m e n t a l d a t a f o r s y s te m p r e s s u r e
a t 60 d e g r e e s C e l s i u s
35
G a r tn e r i n v e s t i g a t e d t h e a q u e o u s p h e n o l - s u p e r c r i t i c a l car b o n
d i o x i d e s y s t e m a t h i g h p r e s s u r e s and meas ured e q u i l i b r i u m
concentrations
with
a
sta tic
experim ental
apparatus
phenol
[15].
For
comparable system p r e s s u r e s and l i q u i d phase phenol c o n c e n t r a t i o n s h i s
data y i e l d e d l a r g e r phenol d i s t r i b u t i o n c o e f f i c i e n t s (on th e order of
10-30% l a r g e r ) .
H i s d a t a i s ju d g e d t o be l e s s r e l i a b l e b e c a u s e o f
o b v i o u s and l a r g e
ex p e r i m e n t a l methods.
in co n sisten cie s
probably
due t o h i s
cruder
36
SUMMARY
1.
The wet c h em is t ry method o f phenol a n a l y s i s was re p r o d u c i b l e w it h
l e s s than 5% error.
2.
Pumping
liq u id
carbon
d io x id e
gave
stab le
pressures
and
s a t is f a c t o r y pressure con trol.
3.
At 40 d egr ee s C e l s i u s the vapor phase phenol s o l u b i l i t y in c r e a se d
for increasing pressure.
4.
At 60 d egr ee s C e l s i u s t h e r e was a minimum i n the vapor phase phenol
so lu b ility
over
the
stud ied
pressure
range fo r
both
so lu tio n
concentrations.
5.
L a rg er p h e n o l s o l u t i o n c o n c e n t r a t i o n s ga v e l a r g e r vapor p h a s e
phenol s o l u b i l i t i e s a t both temperatures.
6.
Lower temperatures gave l a r g e r vapor phase phenol s o l u b i l i t i e s .
7.
The d a t a g e n e r a t e d by t h e t h e r m o d y n a m ic model o f
t h e aq u eo u s
p h e n o l - s u p e r c r i t i c a l carbon d i o x i d e system passed through minimums i n
va p or p h a s e p h e n o l s o l u b i l i t i e s a t b o t h 40 and 60 d e g r e e s C e l s i u s i n
the pres sur e range o f 600 t o 700 p s i a .
8.
The model-generated data at 40 d egr ee s C e l s i u s was four t o e i g h t
t i m e s s m a l l e r i n m a g n i t u d e th an t h e e x p e r i m e n t a l va p o r p h a s e p h e n o l
s o l u b i l i t y data.
At 60 degre es C e l s i u s the model-generated data passed
through minimums i n vapor phase phenol s o l u b i l i t y i n d i f f e r e n t pressure
r e g i o n s t h a n d i d t h e e x p e r i m e n t a l va p o r p ha se p h e n o l s o l u b i l i t i e s .
T h es e d i s c r e p a n c i e s m i g h t ha ve be en c a u s e d by t h e s u b s t i t u t i o n o f
u n a v a i l a b l e p h e n o l - w a t e r - s u p e r c r i t i c a l carbon d i o x i d e t h r e e - c o m p o n e n t
37
d a t a w i t h p h e n o l - w a t e r and w a t e r - s u p e r c r i t i c a l carbon, d i o x i d e two
component data.
9.
C a l c u l a t e d d i s t r i b u t i o n c o e f f i c i e n t s or e q u i l i b r i u m K-values o f
p h e n o l from t h e e x p e r i m e n t a l d a t a a t 40. d e g r e e s C e l s i u s show t h a t
phenol K-values i n c r e a s e fo r in c r e a s e d p res sur e.
At 60 d egr ee s C e l s i u s
phenol K-values from ex p er i m en t a l data showed mihimums in K - v a l u e s .as a
f u n c t i o n of p res su re a t lower p re s s u r es .
38
RECOMMENDATIONS FOR FURTHER STUDY
1.
Changi ng t h e a p p a r a t u s from a s i n g l e p a s s f l o w s y s t e m t o a vapor
r e c i r c u l a t i o n system should be i n v e s t i g a t e d .
This would e l i m i n a t e the
handling of the bomb during a run.
2.
In -lin e
an alysis
w ith high
p r e s s u r e g a s c h r o m a t o g r a p h y would
e l i m i n a t e t h e i n h e r e n t error of manual product c o l l e c t i o n .
a l s o d r a s t i c a l l y reduce the time requ ired f o r product a n a l y s i s .
I t would
references cited
40
REFERENCES CITED
1.
B o t t , T.R., " S u p e r c r i t i c a l Gas E x t r a c t i o n , " Chem. and I n d u s t . ,
March 15, 1980.
2.
Van L ee r , R.A., and M.E. P a u l a i t i s , " S o l u b i l i t i e s o f P h en o l and
C h l o r i n a t e d P h e n o l s i n S u p e r c r i t i c a l Carbon D i o x i d e , " J. Chem.
Eng. Data, 25, 1980.
3.
S m i t h , J.M., and H.C. Van N e s s , I n t r o d u c t i o n t o C h e m i c a l
Engineering Thermodynamics, 3rd e d . , McGraw-Hill, New York, 1975.
4.
W i l k e , G., " E x t r a c t i o n w i t h S u p e r c r i t i c a l G a s e s - A Forward,"
Angew. Chem. I n t . Edn., 17, 1978.
5.
P e t e r , S., and G. B r u n n e r , "The S e p a r a t i o n o f N o n v o l a t i l e
Substances by Means Compressed Gases i n Countercurrent Pr oc es se s,"
Angew. Chem. I n t . Edn., 17, 1978.
6.
Kohn, P.M., and P.R. S a v a g e , " S u p e r c r i t i c a l F l u i d s Try For CPI
A p p l i c a t i o n s , " Chem. E n g . , 8 6 ( 6 ) , 1979.
7.
Z o s e l , K., " S e p a r a t i o n w i t h S u p e r c r i t i c a l G a s e s :
A p p l i c a t i o n s , " Angew, Chem, I n t . Edn., 17, 1978.
8.
H u b er t , P., and O.G. V i z t h u m , " F l u i d E x t r a c t i o n o f Hops, S p i c e s ,
and Tobacco w it h S u p e r c r i t i c a l Gases," Angew. Chem. I n t. Edn., 17,
1978.
9.
M o d e l l , M., and R.P. d e F i l i p p i , and V.J. K r u k o n is , " R e g e n e r a t i o n
of A c t iv a t e d Carbon w it h S u p e r c r i t i c a l Carbon Dioxide," presented
a t t h e 1 7 6 t h N a t i o n a l M e e t i n g o f t h e Americ an C h e m i c a l S o c i e t y ,
Miami, FE, S ep t. 14, 1978.
10.
Young, C .L ., Chem. Thermo. , 2, 1978.
11.
S t a n d a r d Methods f o r t h e E x a m i n a t i o n o f Water and W a s t e w a t e r ,
American Pu b li c Health A s s o c i a t i o n , Washington, DC, 1981.
12.
M o d e l l , M., and R.C. R e i d , T h erm od yn am ics and I t s A p p l i c a t i o n s ,
2nd e d . , P r e n t i c e - H a l l , New J e r s e y , 1983.
13.
H i r a t a , M., and S. One, and K. Nagahama, Computer Aided Data Book
o f Vapor-Liquid E q u i l i b r i a , Kodansha Limited E l s e v i e r S c i e n t i f i c
P u b l i s h i n g , New York, 1975.
14.
P e r r y , R.H., and C.H. C h i l t o n , C h e m i c a l E n g i n e e r s ' Handbook, 5 t h
e d ; , McGraw-Hill, New York, 1973.
P ractical
41
15.
G a r t n e r , A.G., " S u p e r c r i t i c a l F l u i d E x t r a c t i o n o f O r g a n i c s From
Co al G a s i f i c a t i o n W a s t e w a t e r s U s i n g Carbon D i o x i d e , " M a st er o f
S c ie n c e T h e s i s , Montana S t a t e U n i v e r s i t y , 1985.
42
APPENDICES
43
APPENDIX A
DERIVATION OF THE THERMODYNAMIC MODEL
44
DERIVATION OF THE THERMODYNAMIC MODEL
The f o l l o w i n g vapor and l i q u i d phase component f u g a c i t y eq uations
were
from Van N es s and Ab b o tt
(Van N e s s ,
H.C.,
and
M.M.
Abbott,
C l a s s i c a l Thermodynamics o f Non E l e c t r o l y t e S o l u t i o n s , McGraw H i l l , New
York,
1982,
273).
These eq u a tio n s were used to develop the component
f u g a c i t y equation used t o d e s c r i b e phenol and water.
At phase eq u ili b ri u m
Therefore
y ^ i P = Xi T i Zi 0
The standard s t a t e f u g a c i t y o f pure "i" was chosen t o be based upon the
standard s t a t e a s s o c i a t e d
wit h the Lewis-Randall r u l e which was pure
"i" a t the temperature and pressure of the system.
Where
i
45
For both phenol and water the vapor phase f u g a c i t y c o e f f i c i e n t of
pure "i" at s a t u r a t i o n pres sur e was assumed to be u n it y .
to
the
moderate
saturation
tem peratures i n v e s t i g a t e d .
pressures
of
This was due
p h en o l and w a t e r a t
Then t h e s t a n d a r d s t a t e
fu gacity
the
was
re p re se nt ed as:
/0
A
n SAT „ Ji(L-R)
" Fi
x y SAT
Where
/i ( L - F
dP
/ i SAT
Vi dP
RT
d In A
Therefore
_±
(V i) dP
RT
/ i SAT
,SAT
The term on the r i g h t s i d e of the eq uation i s the Poynting c o r r e c t i o n
factor.
I t was assumed th a t the s p e c i f i c volume of l i q u i d phenol and
w a t e r was i n c o m p r e s s i b l e and t h u s , i n d e p e n d e n t o f p r e s s u r e .
result:
Ti(L-R)
/iSA T
pSAT)
As a
46
The r e s u l t a n t component f u g a c i t y equation which d es cr ib ed phenol
and water was:
Vi ( p _ p.SAT)
For carbon d i o x i d e the vapor phase component f u g a c i t y equation was
t h e same e q u a t i o n u se d f o r p h e n o l and w a t e r .
liq u id
assumed
p ha se com ponent f u g a c i t y
that
the
liqu id
standard s t a t e a s s o c ia t e d
The e q u a t i o n f o r t h e
was from Van N es s and Abb ott and
p ha se a c t i v i t y
co efficien t
based on t h e
w i t h Henry's law o f c a rb o n d i o x i d e
was
u n ity (Van Ness, H.C., and M.M. Abbott, C l a s s i c a l Thermodynamics of Non
E l e c t r o l y t e S o l u t i o n s , McGraw-Hill, New York, 1982, p. 86).
The l i q u i d phase was d es cr ib ed by Henry's law.
Henry's law was chosen
due to the low c o n c e n t r a t i o n s of carbon d i o x i d e in the l i q u i d phase and
a v a i l a b l e Henry's law c o n s t a n t s for carbon d i o x i d e in water.
The f i n a l
equation used t o d e s c r i b e carbon d i o x i d e was:
Y ^ i P = Xi Hi
L i q u i d p ha se mo le f r a c t i o n s , Xi , we re c a l c u l a t e d by s e t t i n g t h e
number o f moles of water and phenol i n the l i q u i d s o l u t i o n .
Next the
amount o f the carbon d i o x i d e th a t would d i s s o l v e in the g ive n moles of
water was c a l c u l a t e d at system c o n d i t i o n s u sin g Henry's law c o n s t a n t s ,
47
w h i c h we re from P e r r y ( P e r r y ,
R.H., and C.H. C h i l t o n , - C h e m ic a l
Engineers' Handbook, 5th e d . , McGraw-Hill, New York, 1973, p. 3 - 9 6 ) .
Liquid phase a c t i v i t y c o e f f i c i e n t s , w e r e
Wilson equation.
c a l c u l a t e d from the
Wilson p a r a m e t e r s w e r e e s t i m a t e d g r a p h i c a l l y from
p h eno l-w ate r Wilson parameters a t low p r e s s u r e s and tem peratures above
and below t h e d e s i r e d system tem peratures (Hirata, M., and S. One, and
K. Nagahama,
Computer Aided Data Book o f V a p o r - L i q u i d E q u i l i b r i a ,
Kodansha L i m i t e d E l s e v i e r S c i e n t i f i c P u b l i s h i n g , New York, 1975, p.
754-757).
The e f f e c t s o f t h e s y s t e m ' s h i g h p r e s s u r e upon t h e W i l s o n
p a r a m e t e r s w er e i g n o r e d .
A lso th e e f f e c t s of carbon d i o x i d e in the
l i q u i d phase upon th e Wilson parameters were ignored.
The s a t u r a t i o n p r e s s u r e s ,
steam t a b l e s (Smith,
J.M.,
and H.C. Van Ness,
Engineering Thermodynamics, 3rd ed.,
572-580).
o f w a t e r w er e r e f e r e n c e d from
I n t r o d u c t i o n t o Chemical
McGraw-Hill, New York,
1975,
pp.
P h e n o l s a t u r a t i o n p r e s s u r e s we re from P e r r y ( P e r r y , R.H.,
and C.H. C h i l t o n , C h e m i c a l E n g i n e e r s ' Handbook, 5 t h e d . , M c G r a w - H i l l ,
New York, 1973, pp. 3 - 5 8 ) .
S p e c i f i c v o l u m e s , V^, o f w a t e r w e r e from s t e a m t a b l e s ( S m i t h ,
J .M .,
and H.C. Van N e s s ,
In trod u ction
to C hem ical
E ngin eerin g
T h e r m o d y n a m i c s , 3rd e d . , M c G r a w - H i l l , New York, 19 7 5 , pp. 5 7 2 - 5 8 0 ] .
S p e c i f i c v o lu m e s ' o f p h e n o l w ere from t h e Handbook o f C h e m i s t r y and
P h y s i c s ( W e a s t , R.C., Handbook o f C h e m i s t r y and P h y s i c s 63 rd e d ., CRC
P r e s s , Boca Raton, FE, 1982, p. C-429).
48
Vapor phase component f u g a c i t y c o e f f i c i e n t s ,
from the Peng-Robinson equation of s t a t e .
were c a l c u l a t e d
The Peng-Robinson equation
of s t a t e for vapor phase component f u g a c i t y c o e f f i c i e n t i s given below:
b
i ( Z - I ) - In(Z-B)
Z+B(l-V2)
Z+B(l+y2)
+
A = amP
B = bmf>
RT
#2^2
am =
TZ Y i y i a I i
bm =
Z Yibi
i j
i
a^j = (1-5^ j ) (a^a j )
^ aj
ai i = a i
0.4572R2T c i2
a i = — pE:---------
V alues of
the
em p irically
Therefore
b in ary
in teraction
determined
a ll
values
0.07780RTci
bi = — PcT —
param eter, U qji
and o r d i n a r i l y
of 5-jj
were
are u su a lly
s m a l l numbers around 0. 1 0 .
assu med
to
be 0 . 1 0 .
C ritical
p r o p e r t i e s were from P er ry ( P e r r y , R.H., and C.H. C h i l t o n , C h e m ic a l
E n g i n e e r s ' Handbook, 5 t h e d . , M c G r a w - H i l l , New York, 19 7 3 , pp. 3 - 1 0 4 ,
105).
Vapor p h a se c o m p r e s s i b i l i t i e s ,
Z, used i n t h e P e n g - R o b in s o n
e q u a t i o n o f s t a t e were c a l c u l a t e d f o r pure carbon d i o x i d e a t s y s t e m
c o n d i t i o n s from t h e P e n g - R o b i n s o n e q u a t i o n o f s t a t e ( M o d e l l , M., and
R.C. Reid, Thermodynamics and I t s A p p l i c a t i o n s , 2nd ed., P r e n t i c e - H a l l ,
New J e r s e y ,
1983, pp 152-153).
The a c e n t r i c f a c t o r f o r carbon d i o x i d e
49
used i n c a l c u l a t i n g c o m p r e s s i b i l i t i e s from the Peng-Robinson equation
o f s t a t e was from S m i t h and Van N es s ( S m i t h , J.M., and H.C. Van N e s s ,
I n tr o d u c t i o n t o Chemical Engineering Thermodynamics,
H i l l , New York, 19 7 5 , p. 5 7 0 ) .
3rd ed., McGraw-
50
APPENDIX B
COMPUTER AIDED SOLUTIONS OF THE THERMODYNAMIC
MODEL OF AQUEOUS PHENOL-SUPERCRITICAL CARBON
DIOXIDE VAPOR-LIQUID EQUILIBRIUM
51
COMPUTER AIDED SOLUTIONS OF THE THERMODYNAMIC MODEL
Figures IO and 11 show two computer s o l u t i o n methods f o r 40 degrees
C elsiu s
and
respectively.
10,000
ppm and 60 d e g r e e s C e l s i u s
and
1 0 , 0 0 0 ppm
These methods o f s o l u t i o n in c l u d e the method th at used
a l l t h r e e o f t h e co m p o n en t f u g a c i t y e q u a t i o n s (method I ) ,
and t h e
method t h a t u se d two o f t h e com ponent f u g a c i t y e q u a t i o n s and a vapor
phase mole balance (method 2).
The co m p u t e r program u se d t o c a l c u l a t e t h e d a t a f o r t h e s e c o n d
method a t 60 d e g r e e s and 1 0 , 0 0 0 ppm p h e n o l s o l u t i o n c o n c e n t r a t i o n
f o l l o w s t h e above mentioned f i g u r e s .
Mole f r a c t i o n p h e n o l (v ap o r p h a s e )
Solution
method 2
S o ]u t i o n
method I
2000
F ig u re 10.
P ressu re (p sia)
C om parison o f two s o l u t i o n m e th o d s o f t h e a q u e o u s p h e n o l - s u p e r c r i t i c a l c a r b o n d i o x i d e
th erm o d y n am ic m odel a t 40 d e g r e e s C e l s i u s (m ethod I u s e d a l l t h r e e o f t h e component
f u g a c i t y e q u a t i o n s and m ethod 2 u s e d two o f t h e com ponent f u g a c i t y e q u a t i o n s and a
v a p o r p h a s e m ole b a l a n c e )
Hole f r a c t i o n p h e n o l (v ap o r p h a s e )
S o lu tio n
method 2
S o l u ti o n
method I
1200
2000
P ressu re (psia)
F ig u re 11.
C om parison o f two s o l u t i o n m e th o d s o f t h e a q u e o u s p h e n o l - s u p e r c r i t i c a l c a r b o n d i o x i d e
th erm o d y n am ic model a t 60 d e g r e e s C e l s i u s (m ethod I u s e d a l l t h r e e o f t h e component
f u g a c i t y e q u a t i o n s and m ethod 2 u s e d two o f t h e component f u g a c i t y e q u a t i o n s and
a v a p o r p h a s e m ole b a l a n c e )
5b
ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
LISTING OF CONSTANTS INDEPENOANT OF P & T
PHENOL=I
WATER=Z
SUPERCRITCAL C02=3
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
C
C
CRITICAL PROPERTIES
C
REAL HL3,MC02,K
TCI=694-.2
TC2=647.3
TC3=304.2
PCl=SO.5
PC2=217.6
PC3=72.8
C
C
C
BINARY INTERACTION PARAMETERS
WRITE(6,30)
READ(5,*)0EL1,0EL2
R=82.051
PENG-ROBINSON EQUATION CONSTANTS
K=.707984
A1=.45724*(R*TC1)**2./PC1
A 2 = . 4 5 7 2 4 * (R * T C 2 )* * 2 .Z P C 2
A3=.45724*(R*TC3)**2./PC3
B1=.0778*R*TC1/PC1
B2=.0778*R*TC2/PC2
B3=.0778*R*TC3/PC3
A4=(1.-DEL2)*((A1*A2)**.5)
A5=(1.-DEL1)*((A1*A3)**.5)
A6=(1.-0EL1)*((A2*A3)**.5)
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
C
C
C
DATA IN PU T
C
C
C
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
4
W R IT E (6j35)
REA0(5,*)T,P
WRITE(6,40)
REA0(5,*)Y1,Y2
^ IT E (6 ,4 5 )
READ(5,*)T0L
Figure 12.
Computer program to c a l c u l a t e the vapor-liquid equilibrium
of the aqueous p h e n o l- s u p e r c r it i c a l carbon dioxide system
55
Figure 12. continued
ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
C
C
C
TEMP DEPENDANT PRESS INDEPENDANT CONSTANTS
C
C
C
40 C CONSTANTS
C
C
C
ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
IF(T.EQ .333.) GO TO I
P lSAT=.00146
P2SAT=.07279
SPV0L1=90.
SPV0L2=18.14
WP12=.0080
WP21=.820
GO TO 2
C
C
C
1
60 C CONSTANTS
PlSAT=.00566
P2SAT=.19660
SPV0L1=90.
SPV0L2= 18.31
WP12=.0052
WP21=.744
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
C
C
C
PRESS DEPENDANT CONSTANTS
C
C
C
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
C
C
LIQUID SOLUTION COMPOSITIONS
C
C
40 C
C
2
P=P/14.7
IF(T.EQ.333.) GO TO 3
HL3=EXP(7.8013+(.2306E-2)*P+(. 5801E -4)*P **2.-(. 1999E-6)*P**3.)
X3=P/HL3
MC02=X3*55.6 6 6 /( 1 .-X3)
TMOL=55.666+MC02
Xl=. 1063/TM0L
X2=55.56ZTMOL
WRITE(6,*)X1,X2
C
C
ACTIVITY COEFFCIENTS FROM THE WILSON EQUATION
C
WEQC=WP12/(X1+X21WP12) -WP21Z (X2+X1*IWP21)
ACOEFl=EXP(LOG( I . / (X1+X2*WP12) ) +X2*WEQC)
AC0EF2=EXP(LOG( I . Z( X2+X1^WP21) ) -X1*WEQC)
GO TO 14
C
60 C
C
C
HL3=EXP(8 .1 4 4 + (.3204E-2)*P+(. 2051E-4)*P*^2. - ( . 6298E-7)*P**3.)
3
X3=PZHL3
56
Figure 12. continued
MC02=X3*55.6 6 6 / ( 1 . -X3)
TMOL=55.556tM:02
X1=.1063/TM0L
X2=55.56/TM0L
WRITE(6,*)X1,X2
C
C
C
ACTIVITY COEFFCIENTS FROM THE WILSON EQUATION
WEQC=WP12/(X1+X2*WP12)-WP21/(X2+X1*WP21)
ACOEFl=EXP(LOG(I . / ( X1+X2*WP12) ) +X2*WEQC)
ACOEFE=EXP(LOG( I . / ( X2+X1*WP21) ) -Xl^WEQC)
C
C
C
14
5
6
C
C
C
C
C
C
9
7
C
C
C
8
C
C
VAPOR PHASE COMPRESSIBILITIES FROM THE PENG-ROBINSON
EQUATION OF STATE
ALPHA=(1.+K*(1.-((T/TC3)**.5)))**2.
V=90.
VOL=R*T/( P+A3*ALPHA/(V*(V+B3)+B3*(V-B3)))+83
CALL C0NV(V,V0L,1,NC)
GO TO (B j S ) jNC
Z=P*VOL/(R*T)
VAPOR PHASE COMPOSITION CONVERGENCE LOOPS
FIRST LOOP
Y3=l. - ( Y1+Y2)
PCI=EXP( SPV0L1*(P-PI SAT)/ ( R*T))
Y1C=X1*AC0EF1*P1SAT*PC1/P/(EXP(B1*(Z-1.)/(Y1*81+Y2*B2+Y3*33)OLOG(Z-P*(Y1*B1+Y2*B2+Y3*33)/(R*T))+(Yl**2. *A1+Y2**2. *A2+
@Y3*”2 . *A3+2. *Y1*Y2*(I . -DEL2)*(A1*A2)**.5+2.*Yl*Y3*(I . -DELl)*(A1*
@A3)*” .5+2.*Y2*Y3*(l.-0ELl)*(A2*A3)*” .5)/(2.8284*(Yl*Sl+Y2-,-B2+Y3*
@B3)*(R*T)) * ( ( Y1*A1+Y2*A4+Y3*A5) * 2 . / ( Yl*^2. *A1+Y2*"2. *A2+Y3^2. *A3
@+2.*Yl*Y2*(l.-0EL2)*(Al*A2)**.5+2.*Yl*Y3*(l.-0ELl)*(Al*A3)”” .5
@+2.*Y2*Y3*(l.-0ELl)*(A2*A3)**.5)-31/(Yl*Bl+Y2*32+Y3*33))*L0G(
@( Z -. 4142*PZ(R*T)*(Y1*B1+Y2*B2+Y3*B3) ) / ( Z+2.41^2*P/( R*T)*(Y1*31
@+Y2*32+Y3*33)))))
CALL CONV(Ylj YlCj I jNC)
GO TO (S jZ)jNC
CHECK FOR Y2CALC-Y2 CONVERGENCE
AM=Y1**2.*A1+Y2**2.*A2+Y3**2.*A3+2.*Y1*Y2*(1.-0EL2)*(A1*A2)*~.5
@+2.*Yl*Y3*(l.-DELl)*(Al*A3)*” .5+2.*Y2*Y3*(l.-0ELl)*(A2*A3)*^.S
BM=Y1*B1+Y2*B2+Y3*B3
A=AM*P/((R*T)*^2.)
B=BM*P/(R*T)
PHIE=EXP(B2*(Z - I . ) /BM-LOG(Z-B)+ A /(2 .8284*8)*((Y1*A4+Y2*A2+Y3*A6
@)*2./AM-B2/BM)*L0G((Z-B*.4142)/(Z+B*2.4142)))
PCE=EXP( SPV0L2*(P-P2SAT) / ( R*T))
Y2C=X2*AC0EF2*P2SAT/ ( PHI2*P)*PC2
^ I T E ( 6 J*)Y1JY2,Y2C,Y3
S=2. *ABS(Y2C-Y2)/ ( Y2C+Y2)
IF(S.LE.TOL) GO TO 11
SECOND LOOP
57
c
F ig u re 12. c o n tin u e d
10
C
C
C
11
C
C
C
12
C
C
C
PCZ=EXP ( SPV0L2*( P-P2SAT) / ( RyrT))
Y2C=X2*AC0EF2*P2SAT*PC2/P/(EXP(B2*(Z-1. ) / ( Yl*BlrYZ*82+Y3*33)@L0G(Z -P /(R*T)*(Y1*B1+Y2*B2+Y3*53) ) + (Yl**2. *A1+Y2*C. *A2+Y3**2.
®*A3+2. *Y1*Y2*( I . -0EL2 )*(A1*A2) . 5+2. "Yl^YS^t I . -DELl )*(A1*A3 )*” .5
9+ 2.*Y2*Y3*(I . -OELl)*(A 2*A 3)**.5)/(2.8 2 8 4 ^ * 1 ) / ( Y1™=1+Y2*S2+Y3*83)
0*( (Y1*A4+Y2*A2+Y3*A6)*2./(Yl**2.*A1+Y2**2. yrAZtYBy^Z.*43+2.*Y1*Y2
9* ( I . -0EL2)* (A1*A2)**.5+ 2.*Y1*Y3*( I . -DELl)*(Al*A3)~” .5+2.*Y2*Y3*( I .
9-DELI)*(A2*A3) * * . 5 ) -B2/ ( Y1*B1+Y2*32+Y3*B3) ) *L0G( ( Z - .4142*P/ ( R*T)"
@(Y1*B1+Y2*B2+Y3*B3) ) / ( Z+2. 4142*P/(R*T)*(Y1*31+Y2*S2+Y3*33) ) ) ) )
CALL CONV( Y2, Y2C, I , IMC)
V«ITE(6,*)Y1,Y2,Y2C,Y3
GO TO ( 9 , 1 0 ) , NC
CHECK FOR Y3CALC-Y3 CONVERGENCE
Y3C=l.-(Y1+Y2)
WRITE(6,*)Y1,Y2,Y3C,Y3
Sl=2.*ABS(Y3C-Y3) / ( Y3C+Y3)
IF( S I .LE.TOL) GO TO 12
GO TO 9
PRINT CUT SOLUTION TO VAPOR PHASE COMPOSITION FOR
GIVEN PRESSURE AT SYSTEM TEMPERATURE
PHI1=X1*AC0EF1*P1SAT*PC1/P/Y1
PHI2=X2*AC0EF2*P2SAT*PC2/P/Y2
WRITE(6,*)T,P,Y1,Y2,Y3
WRITE( 6 , * ) PHIlt PHIZ
WRITE(I , 50)T,P*14.7
WRITE(Ij SS)
WRITE(1,60)Y1,Y2.Y3
WRITE(Ij SS)
WflITE(Ij ZO)PHIlj PHIZj PCljPCa
INCREMENT PRESSURE OR ASK FOR NEW PRESSURE OR END
WRITE(Sj ZS)
READ(5,*)P
IF(P.E Q .l.) GO TO 13
IF(P.EQ.10.) GO TO 4
GO TO 2
C
C
C
30
35
40
45
50
55
FORMAT STATEMENTS FOR OUTPUT
F0RMAT(3X,'INPUT BIN INTRCTN PARAMTR; VAP-LIQ. LIQ-LIQ')
FORMAT(3X,'ENTER TEMP ( DEG K ) , ENTER BEG PRESSURE ( PSIA ) ' )
FORMAT(3X,'ENTER INITIAL GUESS FOR; Yphenolj Ywater')
FORMAT(3X,'ENTER CONVERGENCE CRITERION')
F0RMAT(///1X,'TEMP=', F 6 .2 .1 X ,'K ' ,SX, ' PRESS=' ,FS. 1 ,IX, ' PSIA')
FORMAT( / IOX, ' VAPOR PHASE COMPOSITION ( MOLE FRACTION ) ' / /
915X,'PHENOL',10X,'WATER',10X,'C02')
SO
FORMAT( /15X,F8. 7 ,8X,F8. 7 , 7X,F8.7)
65 FORMAT( //IOX, 'VAPOR PHASE FUGACITY COEFFS',S X ,'POYNTING
@ CORRECTION' , / / I O X , ' PHENOL' , IOX, 'WATER' , IlX, 'PHENCL' , 9X, 'WATER')
70
FORMAT(/10X,F9.8,7X,F9.8,6X,F5.2,10X,F5.2)
75
FORMAT(IX,'ENTER NEW PRESS (PSIA); ENTER 10 FOR NEW TEMP, ENTER
9 I FOR PROGRAM END')
13
END
APPENDIX C
SPECTROPHOTOMETRIC PHENOL ANALYSIS
CALIBRATION CURVE OF ABSORBANCE
' VERSUS PHENOL CONCENTRATION
M e asu re d a b s o r b a n c e o f sam ple-
0.60 “
0. 20-
0 .1 0
0.20
o.Uo
P h e n o l c o n c e n t r a t i o n o f sam p le (mg p h e n o l/1 0 0 m l)
F igure 13.
Phenol a n a ly s is c a lib r a t io n curve o f absorbance v ersu s phenol c o n c e n tr a tio n .