Ultrasonic
intensification of
chemical processes
Tom Van Gerven
www.cit.kuleuven.be/process
Contents of this lecture
• PI and ultrasound group in Leuven
• Mechanism of sonication
• Ultrasound effects in chemical processes
• Scale-up of sonochemical reactors
Department of Chemical Engineering
Chemical & Biochemical
Process Technology & Control (BioTeC)
Soft Matter, Rheology and
Technology (SMaRT)
Process Engineering for
Sustainable Systems (ProcESS)
Situating the group in Leuven
Research lines in ProcESS
• Process Intensification & Solid Waste Treatment (Tom Van Gerven)
• Separation processes (Bart Van der Bruggen)
• Evaluation of Environmental Performance (Carlo Vandecasteele)
• Ultrasound processing (8)
• Photochemical processing (3)
• Solid waste treatment (3)
Flagship projects
• EU FP7 project ALTEREGO Alternative energy forms for green chemistry (M€4.5 total, M€0.9 ProcESS
for ‘ultrasound’ work)
• KU Leuven project ERES Extraction of rare earths (M€1.1 total, k€360 ProcESS for ‘light’ work)
• KU Leuven project SMaRT-Pro² Sustainable materialization of residues from thermal processes into
products (k€ 800 total, k€200 ProcESS for ‘mineral carbonation’ work)
Total running budget in PI group at this moment = M€ 2.2
Ultrasound group in ProcESS
1. Dr. Mahdi Gharabaghi, Sonicated leaching of rare earth metals from magnets and lamp phosphors, 2013-
2015, KU Leuven, promoter is Tom Van Gerven.
2. Dr. Gunjan Agrahari, Ultrasound effects on vapour-liquid equilibria, 2013-2015, KU Leuven, promoter is
Tom Van Gerven
3. Chenna Rao, Recovery of rare earths from bauxite residue (red mud), 2013-2016, KU Leuven, promoters
are Tom Van Gerven and Koen Binnemans.
4. Jinu John, Ultrasound-assisted liquid-liquid extraction, 2013-2017, KU Leuven, promoters are Tom Van
Gerven and Leen Braeken.
5. Bjorn Gielen, Ultrasound-assisted reactive crystallization, 2013-2017, KU Leuven, promoters are Leen
Braeken, Tom Van Gerven and Leen Thomassen.
6. Embialle Mengistie, Study and treatment of Cr release from leather tanneries, 2011-2015, KU Leuven –
Jimma University, promoters are Tom Van Gerven and Ilse Smets.
7. Jeroen Jordens, Acoustic processing in microstructured reactors, 2011-2015, KU Leuven, promoters are
Tom Van Gerven, Leen Braeken and Jan Degrève.
8. Rafael Mattos dos Santos, Sustainable materialization of residues from thermal processes into carbon sink,
2010-2014, KU Leuven, promoters are Tom Van Gerven, Jan Elsen and Rudy Swennen.
Ultrasound equipment in ProcESS
• Batch reactor with US horn (Hielscher, 200 W, 24 kHz)
• Autoclave to be equipped with US horn
• Batch and continuous reactors equipped with US
transducers (Meinhardt, 200 W, 10kHz-12 MHz)
Ultrasound in PI scheme
STRUCTURE
(spatial domain)
ENERGY
(thermodynamic domain)
SYNERGY
(functional domain)
TIME
(temporal domain)A
PP
RO
AC
HE
SS
CA
LE
SP
RIN
CIP
LE
S(G
OA
LS
) maximizing the effectiveness of
intra- and intermolecular
events
giving each molecule the same processing
experience
optimizing the driving forces and maximizing
the specific surface areas to which these
forces apply
maximizing synergistic effects
from partial processes
10-16
10-16
10-14
10-10
10--4
10--6
10-2
10-4
100
10-2
102
100
104
102
s
m
Mol ec ula r proc es ses
Catalyst/reaction processes, particles, thin films
Processing unitsProcessing plant/site
Hydrodynamics andtransport processes,single- and multiphase systems
PR
INC
IPL
ES
(GO
AL
S)
AP
PR
OA
CH
ES
SC
AL
ES
ENERGY
(thermodynamic domain)
Van Gerven & Stankiewicz, 2009
Energy to enhance mesoscale effects
mass transfer
mixing
heat transfer
magnetic field
acoustic field
electric field
high gravity
flow field
Ultrasound mechanism
Thompson and Doraiswamy, 1999 Toukoniity et al., 2005
pyrolysis shear micromixing
Muthukumaran et al., 2006
Water and effluent treatment
• destruction of contaminants in water
Polymer chemistry
• degradation of polymer compounds
• initiation of polymerization reactions
Sono-electrochemistry (ultrasound with electrolysis)
• lowering cell voltages
• minimization of electrode fouling
Textile industry
• dispersion and break-up of dye aggregates
• expulsion of entrapped air from fiber capillaries
Ultrasound effects in chemical processes
In chemical reactions:
Reduction in reaction time
Increase in the yield
Switching of the reaction pathway
Changing the product distribution
Hz
Ultrasound effects on reaction time & yield
(L. H. Thompson, L. K. Doraiswamy, Ind. Eng. Chem. Res., 1999, 38, 1215-1249)
Reaction Reaction time Product Yield
Conventional Ultrasound Conventional Ultrasound
Diels-Alder cyclization 35 h 3.5 h 77.9% 97.3%
Oxidation of indane to indan-1-one 3 h 3 h < 27% 73%
Reduction of methoxyaminosilane no reaction 3 h 0% 100%
Epoxidation of long-chain unsaturated
fatty esters 2 h 15 min 48% 92%
Oxidation of arylalkanes 4 h 4 h 12% 80%
Michael addition of nitroalkanes to
monosubstituted ,-unsaturated
esters
2 days 2 h 85% 90%
Permanganate oxidation of 2-octanol 5 h 5 h 3% 93%
Synthesis of chalcones by Claisen-
Schmidt condensation 60 min 10 min 5% 76%
Ullmann coupling of 2-
iodonitrobenzene 2 h 2 h < 1.5% 70.4%
Reformatsky reaction 12h 30 min 50% 98%
Ultrasound effects in solid-liquid systems
(U. Neis, in: Ultrasound in Environmental Engineering, 2002)
Solid-liquid mass transfer enhancement
Ultrasound effects in solid-liquid systems
(U. Neis, in: Ultrasound in Environmental Engineering, 2002)
Solid-liquid mass transfer enhancement
• Ultrasound crystallization: nucleation
0
2
4
6
8
10
12
14
16
18
20
0 100 200 300 400 500 600 700 800 900 1000 1100 1200
Av
era
ge
red
uct
ion
in
MZ
W ( C
)
Frequency (kHz)
Reduction in MZW of paracetamol as function of the applied US frequency The dots represent the average reduction as function of the applied frequency
and the error bars show the standard deviations. Jordens et al., 2013
Ultrasound effects in solid-liquid systems
• Ultrasound crystallization: be careful with degradation
Jordens et al., 2013
0
2
4
6
8
10
12
14
16
18
20
0 10 20 30 40 50 60
Co
nce
ntr
ati
on
of
pa
race
tam
ol
(pp
m)
Time (min)
41 kHz 98 kHz 165 kHz 570 kHz 850 kHz 1140 kHz
Concentration of paracetamol as function of time and frequency.
Ultrasound effects in solid-liquid systems
• Ultrasound crystallization: shaping
Silent conditions Sonicated (48 W/L, 94 kHz)
Tap density = 1.09 g/cm³ Tap density = 2.08 g/cm³
Jordens et al., 2013
SEM images of NiCO3 samples after 120 min with (a) silent, (b) 94 kHz.
Ultrasound effects in solid-liquid systems
• Ultrasound crystallization: polymorphism selectivity
Santos et al., 2012
Ultrasound effects in solid-liquid systems
Ultrasound effects in gas-liquid systems
(A. Kumar, et al., Ind. Eng. Chem. Res., 2004, 43, 1812-1819)
Gas-liquid mass transfer enhancement
Ultrasonic horn system Ultrasonic bath system
• Sonicated VLE
Ripin et al., 2009
Suggested effects: volatility (-> into gas phase), polarity (-> into liquid phase)
Ultrasound effects in gas-liquid systems
Sonochemical reactors
(K. Yasui, at al., Ultrasonics Sonochemistry, 2005, 12, 43-51)
Ultrasonic horn system Ultrasonic bath (standing-wave) system
Sonochemical reactors
(L. H. Thompson, L. K. Doraiswamy, Ind. Eng. Chem. Res., 1999, 38, 1215-1249)
Stirred-tank configuration
Sonochemical reactors
(L. H. Thompson, L. K. Doraiswamy, Ind. Eng. Chem. Res., 1999, 38, 1215-1249)
Harwell configuration
Sonochemical reactors
(L. H. Thompson, L. K. Doraiswamy, Ind. Eng. Chem. Res., 1999, 38, 1215-1249)
Shell-and-tube configuration
Scale-up of sonochemical processes
(L. H. Thompson, L. K. Doraiswamy, Ind. Eng. Chem. Res., 1999, 38, 1215-1249)
Application barriers:
• scale-up methodology
• large-scale efficiency
Scale up: limited penetration depth
Kumar et al., 2006
not an issue in microreactors !
Scale-up of sonochemical processes
(M. Bengtsson, T. Laurell, Anal Bional Chem, 378, 1716-1721 (2004))
Scale-up of sonochemical processes
Scale-up of sonochemical processes
• Models for process design and control to be developed
0.000%
0.002%
0.004%
0.006%
0.008%
0.010%
0.012%
0.014%
0.016%
0.018%
0
10
20
30
40
50
60
70
80
90
100
110
0 10 20 30 40 50 60 Av
era
ge
ca
vit
y v
olu
me
fra
ctio
n [β
av]
Imp
rove
me
nt
fact
or
[Xi]
Frequency (kHz)
Xi
βav
Improving CFD models to move
from micro- (cavitations) to macro-
effect (conversion)
Optimization of
US frequency and
millireactor design
Jordens et al., 2012
Conclusions
• Ultrasound provides interesting effects in single and
multi-phase systems
• A lot of examples on ultrasound intensification reported
in scientific literature
• Ultrasound reactors are available on the market, for a
variety of applications, but efficiency should improve
• Main challenges are
– design methodology for scale-up, models for design and control
– efficiency of ultrasound transfer