Membrane reactors for Process Intensification
Special Symposium - EPIC-1: European Process Intensification Conference - 1
EPIC-1: Multifunctionality (MF-1)
Keywords: membrane reactor, process intensification
The development of innovative systems and techniques offering a drastic improvement in chemical manufacturing and processing is a fundamental issue for a sustainable growth, following the Process Intensification Strategy[1]. According to this logic, membrane reactors (MRs) are the most significant class of the so-called multifunctional reactors integrating reaction and separation in the same unit and, therefore, moving towards plant size reduction, better material exploitation, lower energy consumption, etc.
The advantage of the MR was demonstrated by means of new indexes:
• Volume Index, the ratio of the catalytic volume of an MR to a traditional reactor,
• Conversion Index, the ratio of the conversion of an MR to a traditional one.
A significant size reduction (volume index equal to 1/4) was achieved by the MR for a final conversion of ~80% (corresponding to 90% of the traditional reactor equilibrium one) feeding an equimolecular mixture. Furthermore, a conversion index of 5 was reached using a reformate stream (50%H2; 10%CO2; 20%CO; 20%H2O) which is of particular industrial interest. These values were calculated by means of a 1-D non-isothermal model at 280°C and 1,500 kPa of feed pressure for a 60-micron Pd-Ag self-supported membrane. The catalyst weight and reaction volume necessary to achieve a suitable conversion drastically reduces using an MR with clear gain in terms of plant size reduction (a factor 4-5) and better catalyst utilization. This is due to hydrogen permeation through the Pd-alloy membrane shifting the reaction toward a further conversion; therefore, the MR conversion exceeds the equilibrium one of a traditional reactor. In addition, the reduced hydrogen concentration (on the reaction side) reduced the reverse reaction rate, thus improving the kinetics. Around 80% of the total hydrogen produced, recovered on the permeation side as pure stream, does not require further separation and purification units before its use also in PEMFCs.
Acknowledgments
The Italian Ministry for Foreign Affairs, Direzione generale per la promozione e la Cooperazione Culturale, Rome, Italy is gratefully acknowledged for co-funding this research.
References
[1] Drioli E. Romano M. Progress and new perspectives on integrated membrane operations for sustainable industrial growth. Ind. Eng. Chem. Res. 2001, 40, 1277-1300
[2] Stankiewicz A., “Reactive separations for process intensification: an industrial perspective, Chem. Eng., Proc., 42 (2003), 137-144
[3] Brunetti A., Barbieri, G.; Drioli, E, Engineering Approach for the WGS reaction in a catalytic membrane reactor, 4th Chemical Engineering Conference for Collaborative Research in Mediterranean Countries, Israel, January 9-11, 2006.
Presented Thursday 20, 10:10 to 10:30, in session EPIC-1: Multifunctionality (MF-1).
