(10g) Preparation of FAU Zeolite Membranes on Polydopamine Modified Al2O3 Tubes for Dewatering of Amine-Based Post-Combustion CO2 Capture Solutions
AIChE Annual Meeting
Sunday, November 10, 2019 - 5:24pm to 5:42pm
Amine scrubbing is currently regarded as among the most economical technology for post-combustion CO2 capture. In this process, aqueous amine solvent is circulated between an absorber column for CO2 absorption and a stripping column for solvent regeneration. To reduce the energy required in the stripping column per mole of CO2 captured, a selective ceramic membrane is proposed here to dewater and enrich the carbon loading in the amine solution prior to the stripper . In this work, FAU zeolite membranes installed after the lean-rich heat exchanger were investigated as part of a dewatering unit for implementation into the carbon capture process. The concentrated CO2-rich solution is sent to the top of stripper while the water-rich permeate is joined with the lean amine solvent exiting the bottom of the stripper and is sent back to the absorber. Based on polydopamine (PDA) modified Al2O3 substrates, a simple and facile synthesis strategy was developed to prepare highly reproducible FAU zeolite membranes. In this approach, polydopamine was deposited on Al2O3 tubes (coated with a 30-Î¼m thick Î±-alumina layer with an average pore size of 0.05 Î¼m) under varying time periods between 1-20 h for the fabrication of cross-linked polymer layer. The optimized modification time was 4 h to achieve uniform dopamine polymerization on the Al2O3 surface. Attributing to its bio-adhesive ability through non-covalent self-assembly and covalent polymerization , PDA functioned as a âmolecular seedâ for the attachment of zeolite onto the Al2O3 substrate surface for the formation of a dense and selective membrane layer with a thickness of approximately 3 Î¼m. The physicochemical properties of these zeolite membranes were characterized to understand the hydrothermal synthesis temperature and time on membrane formation by techniques including X-ray diffractometer (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The effects of dewatering test operation temperature (353-413 K) and pressure (0-150 psi) on the membrane dewatering performance were comprehensively investigated in a 5 M monoethanolamine (MEA) solution to work towards an optimized condition. Membranes synthesized at 85 °C for 11 h exhibited fluxes as high as 6.5 kg m-2 h-1 with rejection rates of 95% at 403 K and 75 psi. In addition, FAU zeolite membrane batches were prepared with a high reproducibility of >90%.
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