Communications Membrane Contactors and Catalytic Membrane Reactors in Process Intensification By E. Drioli*, A. Criscuoli,and E. Curcio Membraneoperations,withtheirintrinsiccharacteristicsof efficiency and operational simplicity, high selectivity and permeability for the transport of specific components, compatibility between different membrane operations in integrated systems, low energetic requirement, good stability under operating conditions, environment-compatibility, easy control and scale-up, and large operational flexibility, represent an interesting answer for the rationalisation of chemical productions. Many membrane operations are practically based on the same hardware (materials), only differing in their software (methods). The traditional membrane separation operations (reverse osmosis, micro-, ultra- and nanofiltration, electrodialysis, pervaporation etc.), already largely utilised in many different areas, are today completed with new membrane systems such as catalytic membranereactorsandmembranecontactors.Atpresent,the possibility to redesign important industrial production cycles by combining various membrane operations available in the separationandconversionunits,sorealisinghighlyintegrated membrane processes, is an attractive opportunity because of the synergic effects that can be reached. Additionally, the design of the integrated membrane production cycle in principle satisfy, the requirements for an advanced process intensificationstrategy. Membranecrystallizers,membraneemulsifiers,membrane strippers and scrubbers, membrane distillation, membrane extractors, etc., can be realized and integrated in the production line together with other existing membrane operations for advanced molecular separation and chemical transformations, overcoming existing limits of the more traditional membrane processes. 1 Introduction The design and operation of large plants with steadily increasing production capacity have represented, throughout twocenturies,thepriorityofthechemicalindustry.Sincethe ninteeneighties,indicationsregardingthedramaticdeteriora- tion of the environment, shortage of key raw materials, and general evidence of a social and economic trend adversely affectingasustainabledevelopment,suggestedarequirement for the implementation of more drastic policy measures and industrialpractices. As described in Common Future (World Commission on Environment and Development, 1987), ªsustainable devel- opment is a process of change in which the exploitation of resources, the direction of investments, the orientation of technical development, and institutional change are all in harmony and enhance both current and future potential to meet human needs and aspirationsº. Today,processintensificationandintegrationrepresentthe most promising strategies believed to bring drastic improve- mentsinmanufacturingandprocessing,substantiallydecreas- ing equipment-size/production-capacity ratio, reducing raw materials, saving energy input, replacing and reducing hazardous waste, recycling waste materials. Possiblehighbenefitsimplypotentialrisksconcerningcosts foradditionalorinnovativehardware,needsformoreflexible integration design tools and new plants, efficient scale-up procedures from laboratory/pilot trials to full-scale produc- tion. In this contest, membrane science and technology is expected to make a substantial contribution to the develop- ment of sustainability pathways, thus providing reliable optionsforbothindustrialgrowthandenvironmentalprotec- tion. As is now well known and accepted, the efficiency and simplicityofmembraneseparationandreactiondevicesmake them increasingly competitive against traditional processes and, therefore, attractive for the realisation of process intensificationandintegrationassumptions.Traditionalmem- brane operations, such as microfiltration, ultrafiltration, nanofiltration, reverse osmosis, electrodialysis, pervapora- tion, are going to be completed with new membrane systems (Fig. 1). The possibility to redesign important industrial productioncyclesbycombiningvariousmembraneoperations available in separation and conversion units, by realising integrated membrane processes, represent an attractive opportunity because of the synergic effects that can be reached, namely, the simplicity of these units, and the possibility of advanced levels of automation and remote control. Moreover, the integration of different membrane units gives the possibility to overcome the limits of a single operation, thus improving the performance of the overall process [1]. 2 Membrane Contactors MembraneContactorsrepresentanemergingtechnologyin which the membrane is used as a tool for inter-phase mass transferoperations:themembranedoesnotactasaselective barrier,buttheseparationisbasedontheprinciplesofphase equilibrium. All traditional stripping, scrubbing, absorption, and liquid-liquid extraction processes can be carried out according to this configuration. Differences and advantages of membrane-based unit operations with respect to conventional equipment are here Chem. Eng. Technol. 26 (2003) 9 DOI: 10.1002/ceat.200300012 Ó 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 975 ± [*] E. Drioli (correspondence author), E. Curcio, Research Institute on MembraneTechnology,ITM-NR,c/oUniversityofCalabria±ViaP.Bucci Cubo17/C,I-87030ArcavacatadiRende(CS),DepartmentofChemical Engineering and Materials, University of Calabria, Via P. Bucci Cubo 17/C, I-87030 Arcavacata di Rende (CS), Italy; A. Criscuoli, Research InstituteonMembraneTechnology,ITM-CNR,c/oUniversityofCalabria ±ViaP.BucciCubo17/C,I-87030ArcavacatadiRende(CS),Italy.