Ultrasonic intensification of

Ultrasonic

intensification of

chemical processes

Tom Van Gerven

[email protected]

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

Solid

Liquid

Gas

Pre

ssure

Temperature

Cavitation

Boiling

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


(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 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 crystallization: shaping

Silent conditions Sonicated (48 W/L, 94 kHz)

Tap density = 1.09 g/cm³ Tap density = 2.08 g/cm³


SEM images of NiCO3 samples after 120 min with (a) silent, (b) 94 kHz.


• Ultrasound crystallization: polymorphism selectivity

Santos et al., 2012


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



Stirred-tank configuration



Harwell configuration



Shell-and-tube configuration

Scale-up of sonochemical processes


Application barriers:

• scale-up methodology

• large-scale efficiency

Scale up: limited penetration depth

Kumar et al., 2006

not an issue in microreactors !


(M. Bengtsson, T. Laurell, Anal Bional Chem, 378, 1716-1721 (2004))



• 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


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

Ultrasonic intensification of

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