Daniel Gorri

2.11 Supported Liquid Membranes for Pervaporation Processes

Pervaporation (PV) is a separation technology where a liquid mixture (feed) is placed in contact with one side of a membrane and the permeated product (permeate) is removed as a low-pressure vapor from the other side. The use of liquids immobilized within nanostructured porous supports as liquid membranes (LMs) allows increasing permeation fluxes and selectivity for specific applications, being the main drawback the well-known instability of supported LMs for practical applications. Transport of target compounds in LMs occurs by either simple permeation based on its solubility in the liquid or by facilitated transport involving the use of a carrier to mediate the transport.

Facilitated transport of propylene through composite polymer-ionic liquid membranes. Mass transfer analysis

Abstract Separation of light gaseous olefins from paraffin’s of the refinery process off-gasses has been traditionally performed by cryogenic distillation, which is a highly capital and energy intensive operation. This handicap creates an incentive for the investigation of alternative olefin/paraffin separation technologies. In this regard, membrane technology supposes a potential solution for process intensification. Previous works of our research group reported the use of facilitated transport composite membranes integrating the use of PVDF-HFP polymer, BMImBF4 ionic liquid and AgBF4 silver salt. In this type of membranes, the silver cations react selectively and reversibly with the olefin, allowing the separation via mobile and fixed carrier mechanisms. Ionic liquids were selected as membrane additives because in addition to their negligible vapor pressure that avoids solvent losses by evaporation, they provide stability to the metallic cation dissolved inside, and modify the structure improving the facilitated transport. This technology offers a commercial attractive separation alternative thanks to their modular form of operation, high values of selectivity and permeability and low operational costs. In the present work, propane/propylene permeation experiments involving the use ionic liquids and different membrane compositions were performed. Moreover, basing on the transport and equilibrium parameters previously obtained, a mathematical model description of the system will be proposed fitting the remaining parameters and allowing the design and optimization of the propane/propylene separation process at industrial levels.

Optimal Production of Ethyl Tert-butyl Ether using Pervaporation-based Hybrid Processes through the Analysis of Process Flowsheet

Abstract This work applied a process design methodology based on the combined use of process simulation and heat integration with pinch analysis to analyse a PV-integrated hybrid process for ETBE production. Mathematical modelling and simulation of the membrane module have been performed using Aspen Custom Modeler and linked with Aspen Plus software to describe the overall process. Simulation results showed that the hybrid process, in which the PV modules are located on a side-stream withdrawn from the distillation column, is more favourable in energy consumption and it shows lower content of ethanol in distillate stream than other membrane integrated hybrid processes. Heat integration with pinch analysis shows that it is possible to achieve savings of up to 18% in utilities consumption.

Design of a Hybrid Nanofiltration/Electrooxidation Process for the Removal of Perfluorohexanoic Acid (PFHxA)

Abstract The present work analyses a pilot scale hybrid nanofiltration/electrooxidation process for the removal of persistent perfluorohexanoic acid (PFHxA) from industrial process waters. A mathematical model was developed enabling the simulation and scale-up of the independent nanofiltration (NF) and electrooxidation (ELOX) units. Commercial spiral wound membrane modules and recirculation strategies were implemented in the NF simulation. One single NF unit and a cascade of NF stages were compared. A battery of serial-parallel electrochemical cells was designed for the ELOX system. The simulations showed that the electrochemical treatment is, when one and two NF stages are used, the most energy demanding process. Adding more NF stages increased noticeably the contribution of NF to the global energy consumption. The NF pre-concentration strategy was able to reduce significantly the ELOX energy consumption (up to 86 %) and the overall energy demand. The hybrid NF/ELOX process is foreseen as a beneficial strategy to reduce the energy consumption of large-scale electrochemical processes aimed at the treatment of waters polluted by persistent organic compounds.