Stankiewicz 2003

Reactive separations for process intensification: an industrialperspective

Andrzej Stankiewicz *

DSM Research, P.O. Box 18, 6160 MD Geleen, The Netherlands

Received 11 February 2001; received in revised form 6 July 2001; accepted 13 November 2001

Abstract

The paper presents an industrial view on the current developments in the field of reactive separations, particularly reactive

distillation, reactive adsorption and membrane reactors, and their place in the intensification of chemical manufacturing and

processing. Several cases of successfully commercialized reactive separation technologies are presented. Barriers hindering a wider

introduction of reactive separations in the industry are discussed, together with the most likely scenarios of further developments in

the field.

# 2003 Elsevier Science B.V. All rights reserved.

Keywords: Multifunctional reactors; Separative reactors; Membrane reactors; Reactive distillation

1. Introduction: process intensification

Process Intensification presents one of the most

important trends in today’s chemical engineering and

process technology. It consists in the development of

innovative apparatuses and techniques that offer drastic

improvements in chemical manufacturing and proces-

sing, substantially decreasing equipment volume, energy

consumption, or waste formation, and ultimately lead-

ing to cheaper, safer, sustainable technologies [1]. One of

the basic components of Process Intensification (Fig. 1)

are so-called multifunctional reactors, which can be

described as reactors combining at least one more

function (usually a unit operation) that conventionally

would be performed in a separate piece of equipment.

Integration of reaction and separation presents the most

significant class of multifunctional reactors.

In the simplest case, integration of reaction and

separation takes place purely on the equipment level,

without introducing any new functional interrelations

between the operations involved*/the reaction does not

influence the separation, nor has the separation process

any effect upon the reaction. The aimed result of such

combination can be: smaller inventory, compacter plant

layout and/or better energy management. The Urea

2000plusTM technology, developed by Stamicarbon B.V.

[2] presents a typical example of such a ‘non-interrelat-

ing’ integration. In this process, the carbamate con-

denser, the urea reactor and the inerts scrubber, have

been successfully combined in an essentially single

vessel, the so-called ‘pool reactor’. The integration

resulted in a considerably smaller and cheaper plant

(the height of the plant with respect to the conventional

technology decreased almost 2.5 times*/see Fig. 2), with

much less high-pressure equipment/piping needed and

less energy consumption. Yet, the interrelations between

the reaction and other operations remained basically the

same as in the conventional technology.

In most cases, however, the reaction and separation

are integrated in order to benefit from the interaction

effect between those two, for instance a shift of the

reaction product composition beyond the equilibrium

by an in-situ separation/removal, or an enhancement of

the separation efficiency by a chemical reaction. One

speaks in those cases about reactive separations or

separative reactors .In this paper some industrially relevant reactive

separations are discussed. Special attention is given to

the application aspects, including today’s barriers that

hamper a broader introduction of the reactive separa-* Tel.: �/31-46-4760820; fax: �/31-46-4760809

E-mail address: [email protected] (A. Stankiewicz).

Chemical Engineering and Processing 42 (2003) 137�/144

www.elsevier.com/locate/cep

0255-2701/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved.

PII: S 0 2 5 5 - 2 7 0 1 ( 0 2 ) 0 0 0 8 4 - 3

mailto:[email protected]

tions into the industrial practice and the ways to

overcome those barriers.

2. Reactive distillation

Reactive (catalytic) distillation is one of the better-known examples of a combined reaction and separation,

and is used commercially [3]. In this case, the multi-

functional reactor is a distillation column filled with

catalytically active packing. In the column, chemicals

are converted on the catalyst while reaction products are

continuously separated by fractionation (thus overcom-

ing equilibrium limitations). The catalyst used for

heterogeneous reactive distillation is usually incorpo-

rated into a fiber-glass and wire-mesh supporting

structure, which also provides liquid redistribution and

disengagement of vapor. Structured catalysts, such as

Sulzer’s KATAPAK-S, are also employed [4]. Also, a

reverse process to the one described above, that is,

combination of reaction and condensation, has been

studied [5,6]. The group of industrial technologies, in

which reactive distillation has already been implemented

or is offered for commercialization, has expanded in the

last 20 years.

One of the above-mentioned technologies, the methyl

acetate process by Eastman Chemical, is now widely

regarded as a textbook example of process intensifica-

tion [7]. Here, a task analysis-based process synthesis

resulted in the replacement of traditional reactors and

separation units by a highly integrated reactive distilla-

tion column. In consequence, the number of major

pieces of equipment has been reduced from 28 to 3, as it

is shown in Fig. 3. Other known applications of reactive

distillation include traditional ether technologies

(MTBE, ETBE, TAME), hydration of ethylene oxide

to mono-ethylene glycol, as well as a number of selective

hydrogenations of dienes and aromatics [8]. Processes,

in which reactive distillation may become a potentially

interesting option, include [9]:

Fig. 1. Process Intensification and its components

Fig. 2. Reduction of plant size via integration of reactor, condenser

and scrubber in Stamicarbon’s Urea 2000plusTM technology.

A. Stankiewicz / Chemical Engineering and Processing 42 (2003) 137�/144138

. decomposition of ethers to high purity olefins;

. dimerization;

. alkylation of aromatics and aliphatics, e.g. ethylben-

zene from ethylene and benzene, cumene from

propylene and benzene, alkylation of isobutane with

normal butenes for gasoline blending;

. esterifications, e.g. ethyl acetate from ethanol and

acetic acid;

. hydroisomerizations;

. hydrolyses;

. dehydrations of ethers to alcohols;

. oxidative dehydrogenations;

. carbonylations, e.g. n-butanol from propylene and

syngas;

. C1 chemistry reactions, e.g. methylal from formalde-

hyde and methanol.

Currently, numerous studies are carried out in the

field of reactive distillation modeling, as reviewed

recently by Taylor and Krishna [10]. Also, research on

new internals for catalytic distillation columns attracts a

lot of attention. Some novel packings developed for the

conventional (non-reactive) distillation could probably

be made catalytically active and be used in the reactive

distillation units. One of such promising packings is the

Super X-pack by Nagaoka International Corp., shown

in Fig. 4. The packing, consisting of bundles of fine

Fig. 3. Plant integration in methyl acetate separative reactor process by Eastman Chemical (after Siirola [7]).

Fig. 4. Super X-pack*/novel packing for distillation columns by

Nagaoka International Corp.

A. Stankiewicz / Chemical Engineering and Processing 42 (2003) 137�/144 139

wires, is said to be able to reduce the distillation column

even to one fifth of the size of the columns working with

conventional packings, at a much lower pressure drop

[11]. Further research activities will also focus ondevelopment of new types of catalysts, which could

broaden the feasible operation windows of the reactive

distillation, i.e. the overlap regions between the feasible

reaction conditions and the feasible distillation condi-

tions. The narrow feasible operation windows are one of

the main factors limiting successful industrial applica-

tions of reactive distillation.

3. Reactive adsorption

Numerous research groups investigate integration of

reaction and adsorption, for instance, in chromato-

graphic reactors [12�/16] and in periodic separating

reactors, which are a combination of a pressure swing

adsorber with a periodic flow-forced packed-bed reactor[17]. The simulated moving-bed reactor integrates con-

tinuous countercurrent chromatographic separation

with chemical reaction. Such combination allows achiev-

ing higher conversions and better yield by separating

educts and products of an equilibrium reaction form

each other. The movement of the bed with regard to the

reactants inlets/outlets is usually realized in a rotating

system. One of the more interesting developments here isthe Rotating Cylindrical Annulus Chromatographic

Reactor, shown in Fig. 5. In this design the inlets of

the mobile phase are uniformly distributed along the

annular bed entrance, while the feed stream is stationary

and confined to one sector. As a result of the rotation of

reactor, the selectively adsorbed species take different

helical paths through the bed and can be continuously

collected at fixed locations. Alternatively, it is possibleto hold the reactor stationary and rotate continuously

the feed. Among the processes investigated in the

RCACR are: hydrolysis of aqueous methyl formate

and dehydrogenation of cyclohexane to benzene [18].

Another very interesting type of an adsorptive reactor

is the so-called Gas�/Solid�/Solid Trickle Flow Reactor,

in which fine adsorbent trickles through the fixed bed of

catalyst, removing selectively in-situ one or more of the

products from the reaction zone. In case of the methanol

synthesis this led to conversions significantly exceeding

the equilibrium conversions under given conditions [19].

The economics of the methanol process based on the

Gas�/Solid�/Solid Trickle Flow Reactor was evaluated

and compared with the conventional low pressure Lurgi

process [20]. For the production scale of 1000 ton per

day, the new technology offered considerable reductions

of cooling water consumption (50%), recirculation

energy (70%), raw materials (12%) and catalyst amount

(70%). Further improvement of the GSSTFR concept

could be seen in applying a moving bed of adsorbent

through straight, parallel channels of a monolithic

catalyst, as it is shown in Fig. 6 [21].

In contrast to non-reactive adsorption techniques, the

industrial-scale applications of adsorptive reactors are

still to be seen. Challenges involve materials develop-

ment of catalysts/adsorbents and matching of process

conditions (same temperature) for both reaction and

adsorption, so that high yields/selectivities can be

achieved.

Fig. 5. Scheme of Rotating Cylindrical Annulus Chromatographic

Reactor.

Fig. 6. Possible application of monolithic catalyst in moving-bed

reactive adsorption system (after Kapteijn et al. [21]).


4. Membrane reactors

Today, a huge research effort is devoted to membrane

reactors. The membrane can play various functions in

the reactor system, as described in an excellent review

paper by Sirkar et al. [22] (Fig. 7). The scientific

literature on catalytic membrane reactors is exception-

ally rich and includes many interesting ideas, such as

heat- and mass-integrated combination of hydrogena-

tion and dehydrogenation processes in a single mem-

brane unit. Yet, practically no large-scale industrial

applications of catalytic membrane reactors have been

reported so far. The primary reason for this is the

relatively high price of membrane units, although other

factors, such as low permeability, sealing problems as

well as mechanical and thermal fragileness of the

membranes also play an important role. Further devel-

opments in the field of material engineering may surely

change this picture. Possible application areas of cata-

lytic membrane reactors in the base-chemicals sector,

include:

. dehydrogenations, e.g. ethane to ethene, ethylbenzene

to styrene, methanol to formaldehyde;

. methane steam reforming;

. water�/gas shift reaction;

. selective oxidations, e.g. propane to acroleine, butane

to maleic anhydride, ethylene to ethylene oxide;

. oxidative dehydrogenations of hydrocarbons;

. oxidative coupling of methane;

. methane oxidation to syngas.

On the other hand, membranes are more and morefrequently employed in the life-sciences sector, in

manufacturing of pharmaceuticals, very often in combi-

nation with a bioreactor, in which enzymatic reaction

takes place. In DSM such a combination has been

studied for the production of S-ibuprofen, via the

hydrolysis of the (R,S)-ibuprofen methylester coupled

to a racemisation of the unwanted enantiomer [23]. The

esterase used for the above conversion is stronglydeactivated by the product. To solve this problem, an

ultrafiltration membrane unit has been coupled to the

reactor, in order to remove in-situ the product formed.

The application of the ultrafiltration has led to a

twofold increase of the conversion/productivity, as can

be seen in Fig. 8.

5. Other reactive separations

Reactive extraction processes involve simultaneous

reaction and liquid�/liquid phase separation. The im-

Fig. 7. Membrane functions in chemical reactor (after Sirkar et al. [22]).


miscibility may occur naturally within the reactive

system or may be introduced deliberately by addition

of solvent(s). Reactive extraction can be effectively

utilized to obtain significant improvements in yields of

desired products and selectivities to desired products in

multi-reaction systems, thereby reducing recycle flows

and waste formation. The combination of reaction withliquid�/liquid extraction can also be used for separation

of waste by-products that are hard to separate using

conventional techniques [24,25].

Reactive crystallization , or precipitation , has been

investigated by numerous research groups. Processes

of industrial relevance include liquid-phase oxidation of

para -xylene to terephthalic acid, the acidic hydrolysis of

sodium salicylate to salicylic acid, and the absorption ofammonia in aqueous sulfuric acid to form ammonium

sulfate [26]. A very special type of reactive crystallization

is the diastereomeric crystallization, widely applied in

the pharmaceutical industry for the resolution of the

enantiomers. Here, the racemate is reacted with a

specific optically active material (resolving agent), to

produce two diastereomeric derivatives (usually salts),

that are easily separated by crystallization:

(DL)-Aracemate

� (L)-Bresolving agent

0 (D)-A�(L)-Bn-salt

�(L)-A�(L)-Bp-salt

Diastereomeric crystallization is commonly used in

the production of a number of pharmaceuticals, such as

ampicillin, ethambutol, chloramphenicol, diltiazem, fos-

fomycin, and naproxen [27].

Recently, reactive precipitation in high-gravity (Hi-

gee) field has successfully been used for the production

of nano-size cubic particles of CaCO3. Ultra-fineparticles with the mean size of 15�/40 nm and a very

narrow size distribution, were produced by carbonation

of lime suspension in a Rotating Packed-Bed Reactor

[28]. The reaction times in RPBR were 4- to 10-fold

shorter than the corresponding reaction times in a

conventional stirred-tank unit.

Reactive absorption is probably the most widely

applied type of a reactive separation process. It is used

for production purposes in a number of classical bulk-

chemical technologies, such as nitric or sulfuric acid. Itis also often employed in gas purification processes, e.g.

to remove carbon dioxide or hydrogen sulfide. Other

interesting areas of application include olefin/paraffin

separations, where reactive absorption with reversible

chemical complexation appears to be a promising

alternative to the cryogenic distillation [29].

6. Selection of appropriate reactive separation technology

Obviously, in most cases the nature of the reaction

itself (phases present, type of catalyst, temperature,

pressure) becomes the primary selection criterion of

the separation technologies that could potentially be

integrated in a reactive separation unit. The selected

combination must have a sufficiently large feasible

operation window and must not be too restrictive in

terms of process flexibility and control. A very gooddiscussion of how integration of reaction and separation

reduces degrees of freedom in chemical processing has

recently been given by Tlatlik and Schembecker [30].

Cost calculations are definitely the most important

but not the only criterion for making a final choice from

several technically feasible technologies. In the industrial

practice, the maturity of the given technology and past

experiences with it within the company often play nearlyas important role in the decision making as economical

considerations. This is also due to the fact that there is

generally lack of information on process economics of

Fig. 8. Ibuprofen methylester conversion as a function of time, with and without integrated ultrafiltration unit [23].


the emerging reactive separations and the existing

costing methods are not regarded as sufficiently reliable.

7. Industrial reality: today’s practice and future prospects

Despite many ongoing research activities in the field,

there still exist numerous technical and non-technicalbarriers that hinder a wider introduction of reactive

separations into industrial practice. Many of these

barriers have been identified during two workshops

held in 1998 by the Center for Waste Reduction

Technologies of AIChE [31]. They include:

A) Technical gaps, such as lack of simulation and scale-

up capability, lack of validated thermodynamic and

kinetic data, lack of materials (e.g. integrated

catalysts/sorbents, membrane materials) and lack

of high-level process synthesis methodology.B) Technology transfer barriers, such as lack of multi-

disciplinary team approaches to process integration,

lack of commonality of problems (technology is

application-specific) and lack of demonstrations/

prototypes on a reasonable scale (reactive separa-

tions are still regarded more as a science rather than

a technology).

C) General barriers, such as higher standards, to whichnew technologies must be held, compared to con-

ventional technologies, lack of information on

process economics (early economic and process

evaluation) and fear of risk in using new technolo-

gies.

Two other important factors also play role here,

namely the reduction of the degree of freedom resulting

from the integration of reaction and separation in one

piece of equipment, and the relatively small feasibleoperation windows [30].

Most of these barriers can definitely be overcome and

universities have here a fundamental role to play, not

only by developing new catalysts, new materials, new

methodology and tools for high-level process synthesis,

but also by teaching future chemical engineers an

integrated, task-oriented approach to plant design.

Commercialization of reactive separation technologieswill be further speeded-up by development of the

appropriate design tools, starting from reliable thermo-

dynamic and kinetic models, CFD models for multi-

phase systems and complex geometries, up to the

extended flowsheeting and costing software.

Coming years should bring a significant increase in

the number of industrially applied reactive separation

technologies. In particular fast progress can be expectedin the application of reactive distillation, reactive

adsorption and membrane reactors (including bioreac-

tors). Reactive absorption and adsorption processes

may further be intensified by the use of rotating

equipment, in which high-gravity fields enhance the

mass transfer rates and which until now has almost

exclusively been used for non-reactive separations. Onetype of rotating equipment has already been successfully

applied on a large scale in deaeration of water in oil

fields, via stripping it with natural gas in a rotating bed

[32], another one is offered commercially for counter-

current liquid�/solid adsorption/ion-exchange [33�/35].

First commercialization of the reactive stripping in

rotating equipment has also taken place [36]. Combina-

tion of Higee technology with reactive separations maylead to significant compacting of the process equipment

resulting in substantially smaller, cleaner, and more

energy-efficient chemical plants.

References

[1] A. Stankiewicz, J.A. Moulijn, Process intensification: transform-

ing chemical engineering, Chem. Eng. Prog. 96 (2000) 22�/34.

[2] A low cost design for urea, Nitrogen, No. 222 (July�/Augusts)

(1996) pp. 29�/31.

[3] J.L. DeGarmo, V.N. Parulekar, V. Pinjala, Consider reactive

distillation, Chem. Eng. Prog. 88 (1992) 43�/50.

[4] L.U. Kreul, A. Gorak, P.I. Barton, Katalytische Destillation in

Modernen Strukturiert-Katalytischen Packungen, Jahrestagun-

gen 1998, II, Dechema, Frankfurt (1998), p. 913.

[5] V.L. Halloin, H. Ben Armor, S.J. Wajc, Reactor-Condenser,

Proceedings, Fifth World Congress of Chemical Engineering, San

Diego, vol. III (1996), pp. 232�/237.

[6] H. Ben Armor, V.L. Halloin, Methanol synthesis in a multi-

functional reactor, Chem. Eng. Sci. 54 (1999) 1419�/1423.

[7] J.J. Siirola, An industrial perspective on process synthesis,

AIChE. Symp. Ser. 91 (304) (1995) 222�/233.

[8] G.R. Gildert, K. Rock, T. McGuirk, Advances in Process

Technology Through Catalytic Distillation, Proceeding of the

International Symposium on Large Chemical Plants 10, Antwer-

pen (1998), pp. 103�/113.

[9] W.P. Stadig, Catalytic Distillation: Combining chemical reaction

with product separation, Chem. Proc. 50 (1987) 27�/32.

[10] R. Taylor, R. Krishna, Modelling reactive distillation, Chem.

Eng. Sci. 55 (2000) 5183�/5529.

[11] G. Parkinson, Drip drop in column internals, Chem. Eng. 107

(2000) 27�/31.

[12] M. Mazotti, A. Kruglov, B. Neri, D. Gelosa, M. Morbidelli, A

continuous chromatographic reactor: SMBR, Chem. Eng. Sci. 51

(1996) 1827�/1836.

[13] M. Meurer, U. Altenhoner, J. Strube, H. Schmidt-Traub,

Dynamic simulation of simulated moving bed chromatographic

reactors, J. Chromatogr. 769 (1997) 71�/79.

[14] M. Juza, M. Mazzotti, M. Morbidelli, Simulated moving bed

technology*/analytical separations on a large scale, GIT Special

Chromatografie 18 (1998) 70�/76.

[15] M.C. Bjorklund, R.W. Carr, The simulated countercurrent

moving bed chromatographic reactor: a catalytic and separative

reactor, Catalysis Today 25 (1995) 159�/168.

[16] G. Dunnebier, J. Fricke, K.-U. Klatt, Optimal design and

operation of simulated moving bed chromatographic reactors,

Ind. Eng. Chem. Res. 39 (2000) 2290�/2304.

[17] G.G. Vaporciyan, R.H. Kadlec, Periodic Separating Reactors:

Experiments and Theory, AIChE J. 35 (1989) 831�/844.


[18] R.W. Carr, Continuous reaction chromatography, in: G. Ganet-

sos, P.E. Barker (Eds.), Preparative and Production Scale

Chromatography, Marcel dekker, Inc, New York, 1993, pp.

421�/447.

[19] M. Kuczynski, The Synthesis of Methanol in a Gas-Solid-Solid

Trickle Flow Reactor, Ph.D. Dissertation, University of Twente,

Enschede, 1986.

[20] K.R. Westerterp, T.N. Bodewes, M.S. Vrijland, M. Kuczynski,

Two new methanol converters, Hydrocarbon Processing 67 (1988)

69�/73.

[21] F. Kapteijn, J.J. Heiszwolf, T.A. Nijhuis, J.A. Moulijn, Mono-

liths in multiphase catalytic processes�/aspects and prospects,

Cattech 3 (5) (1999) 24�/41.

[22] K.K. Sirkar, P.V. Shanbhag, A.S. Kovvali, Membrane in a

reactor: a functional perspective, Ind. Eng. Chem. Res. 38

(1999) 3715�/3737.

[23] V. Cauwenberg, P. Vergossen, A. Stankiewicz, H. Kierkels,

Integration of reaction and separation in manufacturing of

pharmaceuticals: membrane-mediate production of S-Ibuprofen,

Chem. Eng. Sci. 54 (1999) 1473�/1477.

[24] M. Minotti, M.F. Doherty, M.F. Malone, Design for simulta-

neous reaction and liquid-liquid extraction, Ind. Eng. Chem. Res.

37 (1998) 4746�/4755.

[25] K.D. Samant, K.M. Ng, Systematic development of extractive

reaction process, Chem. Eng. Technol. 22 (1999) 877�/880.

[26] V.V. Kelkar, K.M. Ng, Design of reactive crystallization systems

incorporating kinetics and mass-transfer effects, AIChE J. 45

(1999) 69�/81.

[27] C.R. Bayley, N.A. Vaidya, Resolution of racemates by diastero-

meric salt formation, in: A.N. Collins, G.N. Sheldrake, J. Crosby

(Eds.), Chirality in Industry, Wiley, Newy York, 1992, pp. 69�/77.

[28] J. Chen, Y. Wang, C. Zheng, Synthesis of nano-particles of

CaCO3 in a novel reactor, Second International Conference

Process Intensification in Practice in: Semel, J. (Ed.), BHR Group

Conf. Series, Publ, No. 28, Mechanical Engineering Publications

Limited, London, 1997, pp. 157�/164.

[29] D.J. Safarik, R.B. Eldridge, Olefin/paraffin separations by

reactive absorption: a review, Ind. Eng. Chem. Res. 37 (1998)

2571�/2581.

[30] S. Tlatlik, G. Schembecker, Process synthesis of reactive separa-

tions, Proc. ARS-1, Advances in Reactive Separations,- 1,

Dortmund, Germany, October 12, 2000, pp. 1�/10.

[31] S. Adler, E. Beaver, P. Bryan, J.E.L. Rogers, S. Robinson, C.

Russomanno, Vision 2020: 1998 Separations Roadmap, Center

for Waste Reduction Technologies, AIChE, New York, 1998, p.

77.

[32] C. Zheng, K. Guo, Y. Song, X. Zhou, D. Al, Z. Xin, N.C.

Gardner, Industrial Practice of HIGRAVITEC in Water Deaera-

tion, Proceedings, Second International Conf. Proc. Intensif. in

Pract., BHR Group Conference Series Publication 28, BHR

Group, London, 1997, pp. 273�/287.

[33] M.A.T. Bisschops, L.A.M. Van der Wielen, K.Ch.A.M. Luyben,

Centrifugal Adsorption Technology for the Removal of Volatile

Organic Compounds from Water, in: Proc. 2nd Int. Conf. Process

Intensification in Practice, J. Semel (Ed.), BHR Grroup Conf.

Series, No. 28, London: Mechanical Engineering Publications

Limited, 1997, pp. 299�/307.

[34] Centrifugal Adsorption Technology for the Removal of Volatile

Organic Compounds from Water, Proceedings, Second Interna-

tional Conf. Proc. Intensif. in Pract., BHR Group Conference

Series Publication 28, BHR Group, London, 1997, pp. 299�/307.

[35] M.A.T. Bisschops, S.H. Van Hateren, K.Ch.A.M. Luyben,

L.A.M. Van der Wielen, Mass transfer performance of centrifugal

adsorption technology, Ind. Eng. Chem. Res. 39 (2000) 4376�/

4382.

[36] D. Trent, D. Tirtiwidjojo, Commercial operation of a rotating

packed bed (RPB) and other applications of RPB technology, in:

Better Processes for Better Products, Proceedings of the 4th

International Conference on Process Intensification for the

Chemical Industry, Brugge, September 10�/12, 2001, M. Gough

(Ed.), BHR Group Ltd., Cranfield, 2001, pp. 11�/19.


Documents

Stankiewicz 2003