WRC RESEARCH REPORT NO. 36
C a t a l y t i c O x i d a t i o n of Organic
Compounds i n Waste Water
Gerard V. Smith
Department of Chemistry
Southern I l l i n o i s U n i v e r s i t y
Carbondale, I l l i n o i s 62901
F I N A L
R E P O R T
Pro j e c t No. B-022 -ILL
The work upon which t h i s p u b l i c a t i o n is based was s u p p o r t e d by f u n d s
provided by t h e U.S. Department of t h e I n t e r i o r a s a u t h o r i z e d under
t h e Water Resources Research Act of 1964, P. L. 88-379
Agreement No. 14-01-0001-1500
UNIVERSITY OF ILLINOIS
WATER RESOURCES CENTER
2535 Hydrosystems L a b o r a t o r y
Urbana, I l l i n o i s 61801
ABSTRACT
CATALYTIC OXIDATION OF ORGANIC COMPOUNDS I N WASTE WATERS
Water p o l l u t i o n i s r a p i d l y becoming a major problem. Through s t u d i e s of t h e
e f f e c t of u l t r a s o u n d on c a t a l y s t s i t h a s been found t h a t c e r t a i n w a t e r p o l l u t a n t s
c a n b e o x i d i z e d o r modified.
T h i s s y n e r g e t i c e f f e c t between u l t r a s o u n d and
c e r t a i n h e t e r o g e n e o u s c a t a l y s t s , s o n o c a t a l y s i s , i s demonstrated q u a l i t a t i v e l y
f o r a number o f o r g a n i c compounds ( a n i l i n e s , s t i l b e s t r o l , o r t h o c h l o r o n i t r o b e n z e n e
and phenol) and q u a n t i t a t i v e l y f o r t h e o x i d a t i o n of i o d i d e i o n . The t e c h n i q u e
shows promise a s a t e r t i a r y t r e a t m e n t of m u n i c i p a l w a s t e w a t e r .
Smith, Gerard V.
CATALYTIC OXIDATION OF ORGANIC COMPOUNDS I N WASTE WATERS
F i n a l Report t o t h e O f f i c e of Water Resources Research, Department
of t h e I n t e r i o r , December, 1970, Washington, D . C.
KEYWORDS--*catalysis/ c a t a l y t i c o x i d a t i o n / c a t a l y t i c d e s t r u c t i o n / * u l t r a s o n i c
d e s t r u c t i o n 1 *waste w a t e r s / * t e r l i a r y t r e a t m e n t
SONOCATALYSIS
by
Gerard V. Smith, F. ~ a t i l " , Yuri ~ a v l o v *
Department of Chemistry
and Juh W. Chen
Department of Thermal and Environmental Engineering
Southern I l l i n o i s U n i v e r s i t y
Carbondale, I l l i n o i s
I
62901
INTRODUCTION
Heterogeneous c a t a l y s t s i n c r e a s e t h e r a t e s of chemical r e a c t i o n s by g a t h e r i n g
I
r e a c t a n t s i n c l o s e proximity and f u r n i s h i n g new, lower energy pathways.
I
In spite
of t h i s common s u r f a c e a b i l i t y t o c o l l e c t molecules, h i g h energy b a r r i e r s preclude
1
t h e r e a c y occurrance of many r e a c t i o n s .
I
U s u a l l y h e a t i s s u p p l i e d t o surmount
high energy b a r r i e r s , b u t , i n p r i n c i p l e , o t h e r forms of energy may be used.
For
i
example, e l e c t r i c a l energy i s used i n e l e c t r o c h e m i c a l r e a c t i o n s , and b o t h h i g h
!I
I
energy p a r t i c l e s and e l e c t r o m a g n e t i c r a d i a t i o n s have imparted e x t r a energy
surfaces.
to
We have discovered t h a t u l t r a s o n i c i r r a d i a t i o n may be a n o t h e r energy
I
I
source f o r c e r t a i n c a t a l y t i c reactions$?
1
p r e s e n t evidence f o r s o n o c a t a l y s i s , t h e s y n e r g e t i c e f f e c t between c e r t a i n c a t a l y s t s
I n t h i s and t h e following papers, we
and h i g h frequency u l t r a s o u n d , and d i s c u s s i t s p o s s i b l e mechanisms and i m p l i c a t i o n s .
1
APPARATUS AND PROCEDURES
The s t a n d a r d experimental a p p a r a t u s was simply a l a r g e flat-bottomed g l a s s
tube (2% x 16 i n c h e s ) p o s i t i o n e d a few m i l l i m e t e r s above an 800 KHz submersible
I
J
?
piezoceramic t r a n s d u c e r (Macrosonics I n c . ) ,
cooling water bath.
4.
*.
both of which were immersed i n a .
The bottom of t h e r e a c t o r t u b e was u s u a l l y g l a s s ; however,
P r e s e n t a d d r e s s Bangalore U n i v e r s i t y
US -USSR Exchange Student
-.
in some experiments aluminum foil and Cuprophan (150PT-M) membrane were used.
Aluminum foil worked very well for short periods but developed holes after several
hours.
The special Cuprophan (15OPT-M) membrane worked well.
Gases were intro-
duced through glass tubes extending to within a few millimeters of the bottom and
optimum insonation was estimated by adjusting variables, e.g. reactor/transducer
positions, for maximum liquid jet height at each energy input.
the apparatus and procedures were as previously described
Other details of
except where noted.
RESULTS
Oxidative Dehydrogenation of Certain Anilines
In six hours at 120'~.
(boiling petroleum ether) aniline is converted to
azobenzene in 87% yield over activated M~o~.' At room temperature and in aqueous
solution, the reaction is not readily detected; however, insonation at 800 KHz
yields azobenzenes and other unidentified products for certain anilines.
Results
from these qualitative experiments are tabulated in Table I. Since experiments
were conducted for the purpose of detecting a reaction, not all products were
isolated and identified. Azobenzene and p,p'-dimethoxyazobenzene were isolated
and identified by mass spectrometry.
TABLE I :
OXIDATIVE DEHYDROGENATION OF AQUEOUS SOLUTIONS OF
ANILINES BY SONOCATALYSIS WITH Mn02/800 KHz
PRODUCTS /RESULTSa
COMPOUND
@N=N@
+
CH~O-@-N=N-@-OCH~
a t l e a s t four others
+
s i x others
t r a c e of p r o d u c t , p o s s i b l y t h e azobenzene
no p r o d u c t s d e t e c t e d
no p r o d u c t s d e t e c t e d
no p r o d u c t s d e t e c t e d
no p r o d u c t s d e t e c t e d
a ) r e a c t i o n m i x t u r e s were f i l t e r e d , e x t r a c t e d w i t h a c e t o n e , e v a p o r a t e d t o d r y n e s s
and a n a l y z e d b y t h i n - l a y e r - c h r o m a t o g r a p h y .
Epoxidation of Stilbestrol
Stilbestrol
J
peracids.
is oxidized to the epoxide by
We have identified the epoxide in the reaction mixture obtained from
a six-hour irradiation of a mixture of 200 mg of stilbestrol, 200 ml of water,
and 500 mg of Mn02 catalysts.
The product isolated by preparative thin-layer-chromatography (TLC) matched
exactly (TLC, I.R., N.M.R.)
an authentic sample of the epoxide prepared from
stilbestrol by epoxidation with m-chloroperbenzoic acid.
Attempted Sonocatalytic Oxidations of Steroids
Insonation of water is believed to produce H202 as a principle product .4
However, since peracid is required for the conversion of stilbestrol to the
epoxide, our finding of stilbestrol epoxide points to the presence of a more
powerful oxidizing agent than H202.
To attempt to identify the relative potency
of the oxidizing agent in insonated water we subjected a variety of steroids to
sonocatalytic oxidation using Mn02.
Compounds tested were progesterone, cholesterol,
stigmasterol, testosterone and lanesterol.
No products could be detected.
Sonocatalytic Reactions of Orthochloronitrobenzene
Orthochloronitrobenzene is a known water pollutant which can be removed
only by charcoal filtration.
It was of interest, therefore, to test the applicability
of the sonocatalytic technique to the destruction of orthochloronitrobenzene. Initially,
a variety of catalysts were tried, Pt02, P ~ / c ,Mn02, Pt/C, R ~ / C with air, oxygen
or oxygen/ozone mixtures, but no reactions were detected.
Products were obtained,
however, with aluminum powder or Raney-nickel catalysts with air, oxygen or oxygen/
ozone mixtures.
These experiments are described and discussed in progress reports
to the FWQCA and in later papers in this series.
Several products were formed in
six hours and the three isolated were typical nitrobenzene reduction products.
When
a saturated aqueous solution of orthochloronitrobenzene is submitted to sonocatalytic
ozonation for 24-hours., neither starting material nor products can be detected.
The Silver Mirror Phenomenon
During the studies with orthochloronitrobenzene silver oxide, Ag20, was
tested as a potential catalyst. No change in orthochloronitrobenzene occurred,
but a silver mirror formed on the walls of the reaction vessel, Plate 1.
Since
no mirror formed in the absence of orthochloronitrobenzene, but the silver was
reduced by ultrasound, we assume that a complex between
and/or A ~ O
and
orthochloronitrobenzene adjusts the silver concentration to that favorable for
forming the mirror.
As can be seen in the upper portion of Plate 1, the distance
between rings of silver is approximately lmm, about the wavelength of insonation.
Sonocatalytic Oxidation of Phenol
Previously, we reported preliminary results of our studies on sonocatalytic
oxidation of phenol.1
Complete details of more extensive studies are included in
reports to the FWQCA and a later paper in this series.
Although phenol can be oxidized under the influence of ultrasound alone, it
is not readily oxidized by catalysts and air at room temperatures.
The combination
of ultrasound and certain catalysts, however, causes the concentration of phenol
to decrease faster than does ultrasound alone.
Sonocatalytic Oxidation of Potassium Iodide
Aqueous solutions of potassium iodide (O.lM, 200 ml) were oxidized either by
high (800 KHZ) or low (55KHz) frequency ultrasound or by various catalysts and
ultrasound.
frequencies.
Tables I1
- VI compare the experimental results at high and low
The values for liberated iodide appear to be reproducible to within
10% of the number and were determined by titration with an 0.05 N solution of
Na2S203.
Y
-
1
,.
J
Plate 1:
-
-
Sonodeposition of silver mirror from aqueous solution of
orthochloronitrobenzene containing solid silver oxide.
V
7
3 s d ~ e 3 e 3y3sa
SUIEJ%
0 ~ * 0(p
8 8 ~ - ( 3 s d - [ s 3 ~2noy3lM
3
pUnoso~3-[n)-(3sd-[e3e~
pue punoseJ3-[n)
(3
-I W T * O m ~ s3~ n o yc u r paaezaq?T ZI 30 J ~ ~ T T / % U(q
sUI73J%OS'0
POZ
SIP
9TT
09 Z
TG
OPZ
oz
06 Z
0
OL T
0
OT z
0
OL z
0
szz
0
€6T
0
0
0
0
qZK)I.
(e
008
TABLE 111:
OXIDATION OF IODIDE TON TO IODINE AT LOW FREQUENCY
CATALYSTa
0 Hzb
Ru203
RU/C
5'2'
CUO/A~~O~~
None
a)
0.50 grams except for Mn02 and Cu0/A1203
b)
mglliter of I2 liberated in three hours from 0.1 M I
'
c)
(ultrasound and catalyst)-(ultrasound
d)
0.200 grams
e)
1.00 grams
without catalyst)-48 = A
TABLE I V :
OXIDATION OF IODIDE I O N TO I O D I N E
AS A FUNCTION OF AMOUNT OF Mn02
GRAMS Mn02
800 KHz
c
- a
a)
c a t a l y s t a c t i v a t e d according t o r e f e r e n c e 2, i . e .
24 h o u r s
b)
c a t a l y s t a c t i v a t e d according t o reference 3 .
c)
c a t a l y s t a c t i v a t i o n same a s i n b b u t a d i f f e r e n t b a t c h
dried a t 125'~ for
TABLE V:
OXIDATION O F I O D I D E TO I O D I N E AS A
FUNCTION OF AMOUNT OF V 2 0 5
GRAMS V 2 0 5
a)
determined graphically
800 KHz
TABLE V I :
OXIDATION OF IODIDE I O N TO I O D I N E UNDER SPECIAL CONDITIONS
CAT /gms
0 KHz
Mn02 10. 20a
0
5
--
--
12.8
--
None a
55 KHz
800 KHz
a)
i r r a d i a t e d f o r t h r e e h o u r s t h e n added enough K I s o l u t i o n t o make 0.1M.
a f t e r t e n m i n u t e s c e n t r i f u g e d and t i t r a t e d f o r 1 2 . I n c a s e of no
c a t a l y s t , s o l i d K I was added a f t e r i r r a d i a t i o n
b)
i r r a d i a t e d o n l y f i f t e e n minutes
c)
s o l u t i o n made b a s i c by a d d i n g 0.2 grams KOH t o 200 m. 0 . 1 M K I s o l u t i o n
d)
s o l u t i o n made a c i d i c by a d d i n g two d r o p s 6M H C 1 t o 500 m l 0.1M K I s o l u t i o n
DISCUSSION
Sonocatalysis
There i s a s y n e r g e t i c e f f e c t , s o n o c a t a l y s i s , between c e r t a i n c a t a l y s t s and
This e f f e c t i s measured q u a n t i t a t i v e l y i n t h e e x p e r i m e n t s
h i g h f r e q u e n c y sound.
w i t h p o t a s s i u m i o d i d e and q u a l i t a t i v e l y i n t h e o t h e r e x p e r i m e n t s .
I n some c a s e s ,
a r e a c t i o n a p p e a r s t o go f a s t e r i n t h e p r e s e n c e o f b o t h a c a t a l y s t and u l t r a s o u n d
t h a n i n t h e p r e s e n c e o f e i t h e r one a l o n e ; i n o t h e r c a s e s , i n which r e a c t i o n does
n o t occur under t h e experimental c o n d i t i o n s , r e a c t i o n s a r e sonocatalyzed, e.g.
e p o x i d a t i o n of s t i l b e s t r o l .
We b e l i e v e t h e e f f e c t i s r e a l and have sought a
r a t i o n a l explanation.
Physical vs
. Chemical E f f e c t s
A v e r y good way t o s t a r t i s t o d e c i d e w h e t h e r t h e e f f e c t i s p h y s i c a l o r
T a b l e V I I l i s t s a v a r i e t y o f p o t e n t i a l p h y s i c a l and chemical
chemical i n n a t u r e .
effects.
That c e r t a i n c a t a l y s t a a r e c o l l o i d e d d u r i n g i n s o n a t i o n i s shown by e x p e r i m e n t s
S o n o c a t a l y s i s o f aqueous p h e n o l w i t h ~ t O ~ / 8 0KHz
0 c a u s e s changes i n
w i t h Pt02.
t h e p h e n o l a s d e t e c t e d by u l t r a v i o l e t s p e c t r o s c o p y .
Using t h i s a s a rough g u i d e
t o d i s a p p e a r a n c e of p h e n o l , i t was found t h a t i r r a d i a t e d aqueous s u s p e n s i o n s of
P t 0 2 were a c t i v e f o r o x i d a t i o n of phenol.
F o r example, when 0 . 2 gms P t 0 2 i n 100
m l of w a t e r i s i r r a d i a t e d one h o u r and 100 m l o f 0.01 M phenol s o l u t i o n i s added
a f t e r t h e i r r a d i a t i o n i s s t o p p e d , a l a r g e d e c r e a s e i n t h e p h e n o l U. V. band
(70% d e c r e a s e ) o c c u r s ,
A p p a r e n t l y t h e c a t a l y s t was c o l l o i d e d by t h e i r r a d i a t i o n ;
t h e c a t a l y s t p a s s e d t h r o u g h f i l t e r p a p e r , e x h i b i t e d a T y n d a l l e f f e c t and c o u l d be
removed o n l y by u l t r a c e n t r i f u g a t i o n .
The c l e a n i n g a b i l i t y o f u l t r a s o u n d o c c u r s by c a v i t a t i o n a t h i g h i n t e n s i t y /
S i n c e most o f o u r e x p e r i m e n t s were conducted a t h i g h f r e q u e n c y ,
frequency r a t i o s .
800 KHz, and low i n t e n s i t i e s , 33 watts/cm2 maximum p o s s i b l e b u t p r o b a b l y a b o u t 5
-
-
- -
.
-.
TABLE V I I :
POSSIBLE PHYSICAL AND CHEMICAL
EFFECTS CAUSING SONOCATALYSIS
PHYSI CAL
I.
11.
111.
Increasing surface area
A. F r a c t u r i n g C a t a l y s t
( c o l l o i d ; c r e a t e more
pores)
B.
Cleaning s u r f a c e
( d e s t r o y t h i c k absorbed
layers)
i
CHEMICAL
I.
I n c r e a s i n g r a t e of d i f f u s i o n
A. Bulk d i f f u s i o n
B.
Pore d i f f u s i o n
Deform d o u b l e l a y e r
11.
IV.
Effecting substrate-catalyst
bonding
A. Energy absorbed by s u b s t r a t e c a t a l y s t complex
B. Energy absorbed by c a t a l y s t
and t h e n t r a n s f e r r e d t o substrate
i. h e a t i n g of c a t a l y s t
ii. e l e c t r i c ( p i e z o )
C. Energy absorbed by s o l v e n t o r
g a s and t h e n t r a n s f e r r e d t o
s u b s t r a t e - c a t a l y s t complex
Catalyst serving a s nuclei
for cavitation
Changing s o l v e n t i n t o r e a c t i v e
species
A. H202
B.
'OH, H e
111. Changing gas i n t o r e a c t i v e
species
A.
O2 ( s i n g l e t oxygen)
B. O 3 j 0 ' + 02 ( s i n g l e t o r
triplet)
w a t t s / c m z u n d e r a c t u a l c o n d i t i o n s , l i q u i d p h a s e c a v i t a t i o n was p r o b a b l y n o t o c c u r r i n g .
A t d i f f e r e n t k i n d s of s u r f a c e s , however, some c a v i t a t i o n may o c c u r a t i n t e n s i t y /
f r e q u e n c y r a t i o s lower t h a n r e q u i r e d i n t h e l i q u i d phase and lower t h a n r e q u i r e d
f o r some s u r f a c e s .
Such s u r f a c e c a v i t a t i o n c o u l d p r o v i d e p h y s i c a l d i s t u r b a n c e s of
a d s o r b e d p o i s o n s o r t h i c k adsorbed l a y e r s of m o l e c u l ~ so r c o u l d deform d o u b l e
l a y e r s of any i o n s p r e s e n t .
Because of o u r h i g h i n t e n s i t y / f r e q u e n c y r a t i o s i t
does n o t seem l i k e l y t h a t c a v i t a t i o n i s s i g n i f i c a n t .
I n s e v e r a l phenol o x i d a t i o n
e x p e r i m e n t s Adams p l a t i n u m o x i d e c a t a l y s t was r e p l a c e d by powdered a c t i v a t e d
c h a r c o a l t o t e s t t h e p o s s i b i l i t y t h a t s m a l l c a t a l y s t p a r t i c l e s were s e r v i n g a s
nuclei for cavitation.
O t h e r t h a n a n i n i t i a l and r a p i d a d s o r p t i o n of phenol by
t h e c h a r c o a l no f u r t h e r d e c r e a s e i n phenol c o n c e n t r a t i o n o c c u r r e d d u r i n g i n s o n a t i o n .
Supermixing r e s u l t i n g from a c o u s t i c s t r e a m i n g c o u l d remove d i f f u s i o n c o n t r o l
e i t h e r i n t h e b u l k phase o r i n c a t a l y s t p o r e s .
We d i d n o t t e s t f o r e i t h e r of t h e s e
p o s s i b i l i t i e s ; however, c h e m i c a l e v i d e n c e , s u c h a s t h e changes i n o r t h o c h l o r o n i t r o benzene and s t i l b e s t r o l which do n o t o c c u r u n d e r t h e same c o n d i t i o n s i n t h e a b s e n c e
o f u l t r a s o u n d , seem t o p r e c l u d e removal of d i f f u s i o n c o n t r o l a s a s i g n i f i c a n t
f a c t o r i n our experiments.
It seems g e n e r a l l y a c c e p t e d t h a t u l t r a s o u n d c a u s e s c h e m i c a l changes i n v a r i o u s
substances.
I n w a t e r , f o r example, i t i s b e l i e v e d t h a t hydrogen p e r o x i d e i s
Our s o n o e p o x i d a t i o n o f s t i l b e s t r o l , however, s u g g e s t s a somewhat more powerful
o x i d i z i n g a g e n t t h a n hydrogen p e r o x i d e .
Such a n a g e n t might b e 'OH,
s i n g l e t oxygen
o r some oxygen s p e c i e s absorbed on t h e c a t a l y t i c s u r f a c e .
An e x c i t i n g p o s s i b i l i t y i s t h a t u l t r a s o n i c e n e r g y i s used by t h e c a t a l y s t ( o r
c a t a l y s t - s u b s t r a t e complex) t o surmount e n e r g y b a r r i e r s f o r r e a c t i o n s .
Such a
p o s s i b i l i t y o f f e r s the potential f o r s e l e c t i v e l y catalyzing m e reaction i n preference t o others.
ST
-
d ~ p e qo s saAem 3 r u o s e x 3 ~ nay3 3 3 a ~ ~ apue
x a s x a d s r p saT3rqxed 7 s d ~ e 3 8 3J O sayJT3
-uenb 2 u ~ s e a x 2 u r ay3 d ~ ~ u a x e d d g-auoTe aprxorp a s a u ~ 2 u e mp a q e h r q ~ e d q pa3exaqTT
3eq3 s p n b a 3~ T r J u n ssaT pue ssa1 s a w ~ a qpa3exaqlT auTpoy 30 qunotue ay7 pappe
~ s d p q e 3a x o u pue axom se ' x a ~ a n o o~ s r s d ~ e 3 e 2 0 u o s* a * r g a u o l e apTxorp asaue%ueu
-2a3uT u e s l e a h a x T a x n % ~ dLIT AI a l q e L uox3 e3ep ay3 % u ~ q ~ o "~1 da x n 4 ~ du r u n o y s
s e uaddey 301.1 saop s ~ y 3' 3 3 ~ 3U I
" s a 3 e x ~ u a p u a d a p u ron3 ay3 30 mns ay3 0 3 ~ e n b a
d ~ a 3 - e u ~ x o x d d -aqex
e
e 3e p a a ~ o x d ' y q o q 30 a 3 u a n ~ j 1 . 1snoaue3lnurs
~
ay3 Japean 'pinon
axan s 3 s d ~ e 3 e 3xno
JO
auou a a u ~ ss3uamrxadxa xno u r In330 3ou p ~ n o 3 ' a m n o 2
s u p x % a u ~ l y e 3 s d x 23 ~ d o x 3 o s r uuodn
~
spuadap s p g o s Xq punosElqln 30 u o r j d x o s q e
' s % u ~ y xay3o
3
% u o w * s x a T x n q d8xaua ure3xa3 8ur3unourarns 30 sueam e aprhoxd
pTnqM a 3 e j x n s 3 s d ~ e 3 e 2ay3 3e d%xaua 3eay o3ur d%xaua DguosexqTn 30 uoSsxaAuo3
. s a ~ n ~ a ~paqxosqE
om
Jay30 y 3 ~ nuor33exa3u-r. Apeax xo a x n ~ d n xpuoq s a s n m a3sSxns
~ s d ~ e 3 e ay3
r , uo u o ~ 3 d x o s q e3ey3 y m s p a s p z aq
30 Xsxaua ay3 d e n x e ~ g m ~e s U I
p~t-103
u o S 3 n l o s u ~ s. a ~ a 3 a l o muro3xa3
8 * u o r 3 e u o s u r d q gaqxnz~sypaxe e r x q r l y n b a Teuor3
-eubaoguo3 pue LUOJ3BTP$llr dnuanbaxj y % ~ dy q pasnea suo.!Jou prdex ay3 dq p a x n ~ d n x
a x e ' a ~ d u e x ax o j ' s a y n ~ a ~ o3rue%xo
m
% u o ~* s p u o q pauayean a x n ~ d n x03 ySnoua aq
dem s 3 3 a j J a y3ns pue 9 Z H X 008 3e uog3zuosur d q pa3eaxs axe suorjom pue saxnssaxd
Tel3uv3sqnS
e s a x a ~ d w 3a 3 e x ~ s q n s - ~ s d ~ e 3uer 3 paxa3Te axe sar%zaua puog
that the ultrasound induced reaction and sonocatalytic reaction cannot occur.
A
similar but greater effect can be seen in the data for V205 in Table V.
Excellent experimental agreement for this damping effect is seen in recent
work which was apparently conducted simultaneous to ours.
By measuring the
decomposition of hydrogen peroxide by ultrasound (550 KHz, 4-5 W cmm2) as a
function of increasing amounts of catalysts, data plotted in Figure 2 were obtained.9
Although we were not able to extract the datum for ultrasound and no catalyst, the
damping effect is obvious.
Data for rhodium and palladium did not so clearly demon-
strate the effect.
Evidently sonocatalysis is limited by this damping effect.
Reactor design can
probably overcome some of the effect but large amounts of catalyst will decrease
rates on a per gram basis.
This will apply to reactions which are sonolytically
induced as well as reactions which are sonocatalyzed.
,
ACKNOWLEDGEMENTS
We gratefully acknowledge support through grants from the Office of Water
Resources Research and the Office of Research and Projects of the Graduate School
at Southern Illinois University.
the U.S.-U.S.S.R.
One of us (Y.P.) acknowledges support through
exchange program.
We appreciate Mr. Michael Beckett increasing our confidence in certain data
through repeat experiments.
REFERENCES
1. Presented at The California Catalysis Society Spring Symposium, Stanford
University, April 26, 1969.
2.
J. W. Chen, J. A. Chang and G. V. Smith, Chemical Engineering Progress
Symposium Series in Sonochemical Engineering, (Pueto Rico, May 1970)
edited by Scott Folger, published by American Institute of Chemical
67, in press (1971).
Engineers, New York, vol. -
3. E. F. Pratt and T. P. McGovern, J. Org. Chem. 29 1540 (1964)
-
4. I. E. Ellpiner, "Ultrasound: Physical, Chemical and Biological Effects,"
translated by F. L. Sinclair, Consultants Bureau, New York (1964) page 43.
5. G. L. Gooberman, "Ultrasonics, Theory and Application," Hart Publishing Co.,
New York (1968) page 107.
6. Ibid
pages 44-48
i
7. Ref. 4 pages 119-126
8. Ref. 5 page 135
44 605 (1970).
9. A. N. Mal'tsev and I. V. Solov'eva, Russ. J . Phys. Chem. -