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Chemical Process Engineering and Forest Products Research Centre
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Optimization and performance studies of PES/SAPO-34 membranes for CO2/N2 gas separation
Publication . Cardoso, Jonathan; Fonseca, Joel P.; Lin, Zhi; Brito, Paulo; Gando-Ferreira, Licínio M.
SAPO-34 nanocrystals were prepared and used as inorganic filler in polyethersulfone (PES) membranes. The
influence of preparation conditions on permeation properties of CO2 and N2 gases and CO2/N2 selectivity were
studied to achieve the highest separation performance possible for this mixed-matrix membrane. Gas permeation
properties of PES/SAPO-34 MMMs with different contents of SAPO-34, PES and initial film thickness were
investigated according to a full factorial design of experiments (DOE). The permeation tests and DOE results
revealed that the optimized conditions to maximize the selectivity for PES/SAPO-34 are: composition of 18.5 wt
% of SAPO-34, 15 wt% of PES, and a casted film thickness of 400 μm resulting in a CO2/N2 selectivity of 30.85.
The findings showed that a multivariable model was validated and able to predict the selectivity with determination
coefficient R2 of 0.969 and the results are in accordance with values presented in literature for PES/
SAPO-34 membranes. An economic analysis shows that the commercial grade price for the optimized membrane
is EUR 9.43/m2 which represents around 2.2 times cheaper than polymeric commercial membranes.
Enhancing CO2/N2 and CO2/CH4 Separation Properties of PES/SAPO-34 Membranes Using Choline Chloride-Based Deep Eutectic Solvents as Additives
Publication . Cardoso, Jonathan; Lin, Zhi; Brito, Paulo; Gando-Ferreira, Licínio M.
CO2 separation is an important environmental method mainly used in reducing CO2
emissions to mitigate anthropogenic climate change. The use of mixed-matrix membranes (MMMs)
arrives as a possible answer, combining the high selectivity of inorganic membranes with high
permeability of organic membranes. However, the combination of these materials is challenging due
to their opposing nature, leading to poor interactions between polymeric matrix and inorganic fillers.
Many additives have been tested to reduce interfacial voids, some of which showed potential in
dealing with compatibility problems, but most of them lack further studies and optimization. Deep
eutectic solvents (DESs) have emerged as IL substitutes since they are cheaper and environmentally
friendly. Choline chloride-based deep eutectic solvents were studied as additives in polyethersulfone
(PES)/SAPO-34 membranes to improve CO2 permeability and CO2/N2 and CO2/CH4 selectivity.
SAPO-34 crystals of 150 nm with a high surface area and microporosity were synthesized using
dry-gel methodology. The PES/SAPO-34 membranes were optimized following previous work
and used in a defined composition, using 5 or 10 w/w% of DES during membrane preparation.
All MMMs were characterized by their ideal gas permeability using N2 and CO2 pure gasses.
Selected membranes were also tested using CH4 pure gas. The results presented that 5 w/w%,
in polymer mass, of ChCl–glycerol presented the best result over the synthesized membranes.
An increase of 200% in CO2 permeability maintains the CO2/N2 selectivity for the non-modified
PES/SAPO-34 membrane. A CO2/CH4 selectivity of 89.7 was obtained in PES/SAPO-34/ChClglycerol
membranes containing 5 w/w% of this DES, which is an outstanding ideal separation
performance for MMMs when compared to other results in the literature. FTIR analysis reiterates the
presence of glycerol in the membranes prepared. Dynamic Mechanical Thermal Analysis (DMTA)
shows that the addition of 5 w/w% of DES does not impact the membrane flexibility or polymer
structure. However, in concentrations higher than 10 w/w%, the inclusion of DES could lead to high
membrane rigidification without impacting the overall thermal resistance. SEM analysis of DESenhanced
membranes presented asymmetric final membranes and reaffirmed the results obtained in
DMTA about rigidified structures and lower zeolite–polymer interaction with higher concentrations
of DES.
Post-treatment Modification Using Deep Eutectic Solvent in PES and PES/ SAPO-34 Membranes for Gas Separation
Publication . Cardoso, Jonathan; Lin, Zhi; Brito, Paulo; Ferreira, Licínio
Mixed matrix membranes (MMM) are heavily studied and the main concern by researchers is the difficulty to obtain a high selectivity membrane with low defects, mainly interfacial voids due to the poor interaction between polymer matrix and filler. The functionalization of zeolite surface in PolyEtherSulphone (PES)/ Silico-AluminoPhosphate-34 (SAPO-34) led to membranes with higher compati-bility. Recently, the use of ionic liquids in the particles surface to improve the gas permeability and separation efficiency has presented advanced results. Although, the cost and environmental issues on Ionic Liquids (ILs) still represent a limit to its use. The Deep Eutectic Solvents (DESs) present an alternative route to replace ILs, with low-cost and environmentally friend. This paper aims to study the potential use of choline chloride/urea, a DES mixture, in ratio 1:2, to replace ILs as a post-healing methodology, showing a 20% increase in CO2 permeability in PES membranes and 15% increase in CO2/N2 selectivity in PES/SAPO-34 membranes due to an increase in compatibility between polymer and zeolite promoted by the post-treatment using DES.
Development of Polyethersulphone Mixed Matrix Zeolite Membranes Functionalized with Ionic Liquids and Deep Eutectic Solvents for CO2 Separation
Publication . Cardoso, Jonathan; Lin, Zhi; Brito, Paulo; Ferreira, Licínio
Mixed matrix membranes (MMM) combine the flexibility of polymers and the strength and durability presented by inorganic solids. In an economically point of view, the advantages of membrane separation are low capital investment and space requirements, high process flexibility and lower energy consumption, helping for a more cost-effective separation process and providing a high separation degree. The molecular sieves based on nano-sized silicoaluminophosphates (SAPO) appear as one of the main materials in MMM for gas separation because the pore size of chabazite (CHA) (0.38 nm) is near the kinetic diameter of gases like H2 (0.29 nm), CO2 (0.33 nm), N2 (0.36 nm), CO (0.37 nm), CH4 (0.38 nm) and reduced crystal size improves the dispersion and decreases interfacial defects. Doping SAPO-34 are intended to increase the potential of these solids. The use of isomorphic substitution by transition metals (Fe, Ni, Co, Mn), results in materials with different acidity that differ from the original SAPO in interactions with other compounds. Besides, the addition of ionic liquids (IL) or Deep Eutectic Solvents (DES) with high affinity and selectivity to CO2, onto the particle surface and then dispersing it in a polymer membrane can enhance the separation characteristics, resulting in better permeation and selectivity properties.
Influence of [emim][Tf2N] in PES/SAPO-34 mixed matrix membranes for gas separation
Publication . Cardoso, Jonathan; Lin, Zhi; Brito, Paulo; Gando-Ferreira, Licínio M.
Mixed matrix membranes (MMM) are heavily studied and the main concern by researchers is the difficulty to obtain a high selectivity membrane with low defects, mainly interfacial voids due to the poor interaction between polymer matrix and filler. The functionalization of zeolite surface in Poly-EtherSulphone (PES)/Silico-AluminoPhosphate-34 (SAPO- 34) led to membranes with higher compatibility. Recently, the use of ionic liquids in the particles surface to improve the gas permeability and separation efficiency has presented advanced results. The aim of this work is to compare the separation efficiency of CO2 and N2 in permeance and selectivity criteria. The use of the ionic liquid (IL) [emim][Tf2N] showed an increase in selectivity and in CO2 permeance due to promoting a better separation of the dispersant in the polymeric matrix when compared to a film with the same composition without the IL treatment.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
6817 - DCRRNI ID
Número da atribuição
UIDB/00102/2020