Patent Application
20250186950
This application claims priority to Brazilian Application No. BR 1020230256597, filed on Dec. 6, 2023, the disclosure of which is herein incorporated by reference in the entirety.
The present invention refers to processes for the preparation of polymeric membranes, which can be nanostructured hybrids, containing ionic liquids and their derivatives for sequestration of CO2 from natural gas by gaseous permeation, and its referred membranes. The membranes of the present invention can be dense flat membranes, or composite asymmetric flat membranes.
The invention can be applied in oil and gas extraction and renewable energies, for example, in existing gas treatment plants on off-shore platforms, replacing existing conventional polymeric membranes, as well as in new gas treatment plant designs that use polymeric membranes as natural gas purification technology, or treatment of exhausted gas streams.
Natural gas extracted from underwater deposits off the Brazilian coast contains high levels of CO2 (15-50% by volume), which needs to be separated from the main stream to ensure the thermal power conferred by methane CH4, the main component, in order to meet the current standards for its use as fuel and feedstock in the petrochemical industry. In addition, this natural gas is available at relatively high pressures. The most widely used technology employs chemical extraction of CO2 and operates at low pressures, also requiring thermal recovery of absorbent solvents, making the process energetically costly. The most promising alternative process for purifying natural gas lies in the process of gaseous permeation, which employs selective polymeric membranes. However, this process has performance limitations that affect the operation and economics of the extraction process, when the concentration of CO2 increases in natural gas.
Considering that the limitations mentioned above could be circumvented if more efficient membranes were used in gaseous permeation, also promoting the reduction of the space occupied by the industrial unit and the increase of methane recovery (volume of natural gas enriched with CH4), the technical problem to be solved by the present invention is to extract the CO2 present in natural gas more effectively.
Thus, the objective of the present invention was the development of polymeric membranes that are more selective to CO2 to be used in natural gas purification processes that have high concentrations of CO2. The membranes developed are polymeric membranes containing ionic liquid in their composition that can be used in existing natural gas treatment plants, replacing conventional polymeric membranes.
Due to its better performance, the adoption of this new membrane has the potential to reduce the area and weight occupied on offshore platforms, or even allow a greater flow of gas to be treated by the plant. This technology can also be applied to capture CO2 in exhausted gas streams from turbines and other sources as a way to reduce the emission of polluting gases into the atmosphere.
The polymeric membranes obtained by the processes of this invention withstand high operating pressures, and have been tested to extract CO2 present in natural gas at high concentrations, particularly up to 50%.
The sequestration of CO2 from hydrocarbon streams, in particular natural gas, remains an important priority for the oil and gas industry. Processes that use selective membranes are considered one of the most promising alternatives to replace conventional treatment with amines. Membrane processes have several advantages, such as smaller installation space and lower energy requirements, in addition to not requiring regeneration of extractors or adsorbents. Challenges still persist in relation to the performance of the membranes currently available on the market, particularly in the sense of obtaining a good compromise between permeability and selectivity.
Several studies have shown that the selectivity of membranes decreases as permeability to the more permeable gaseous component increases. A correlation of permeability and selectivity originally suggested by Robeson has updated the literature outcomes for each gaseous mixture of industrial interest, indicating the best membrane performance values to be overcome, graphically represented by a straight line in the permeability vs. selectivity diagram and known as “Robeson upper limit”. Thus, it serves as a guide to develop membranes that have high permeabilities and selectivities to be used in industrial processes, in an economically viable way. Despite the wide availability of developed materials, few could be commercially incorporated into the market for capturing CO2 from gas mixtures.
Ionic liquids (IL) are materials that have a unique combination of physicochemical properties, in addition to some being good solvents for CO2, and have recently been suggested as promising components in the manufacture of membranes that can reach or exceed the Robeson upper limit for mixtures containing CO2. Thus, membranes containing ionic liquids can achieve performances superior to membranes currently available on the market. However, the incorporation of these membranes in the market is still restricted by the high cost and the difficult production of ionic liquids.
Some protic ionic liquids, based on ethanolamines and carboxylic acids, also show high absorptive selectivities for CO2compared to CH4, also showing reversible interactions with CO2. These materials can be synthesized through a simple and inexpensive route, evidencing their potential for application in the separation between CO2 and CH4. The impregnation of a protic ionic liquid in polymeric materials of lower cost and adequate chemical and mechanical properties could generate membranes with excellent performance in the treatment of natural gas.
In addition to the difficulty of incorporating ionic liquids into polymers for the production of membranes, there are also major limitations in scaling these membranes from the laboratory to the industrial scale. This is due to factors such as the low availability of data obtained in operations with industrial mixtures, conducted at high pressures, and the performance of temporal stability tests, in addition to, above all, the difficulty of producing membranes and permeation modules in commercial format. The format necessary to generate greater performance for the commercialization of the product comprises the production of composite membranes, which have a porous support covered with a dense selective thin layer, generated from the developed polymeric solution. The production of this type of membrane involves a series of technical difficulties to generate a selective layer thin enough and for the resulting membrane to have high performance associated with an economically acceptable useful life.
The state of the art document WO 2021/219887 refers to a composite membrane for gas separation, which is suitable for separating a gas from a gas mixture and comprises a selective layer coated on a support, in which said selective layer comprises: a) a polymeric matrix comprising an amine polymer; b) a graphene oxide nanoload and c) a mobile transporter selected from an ionic liquid or an amino acid salt, as well as proposes a process for the formation of said membrane. Both the components of the membrane and the process suggested by WO 2021/219887 differ from those proposed here.
In this context, the present invention is based on the formulation of a protic ionic liquid in a suitable polymeric material. The solution generated in this mixture is used in the coating of a porous support for the production of composite membranes, aiming at high performance and stability, to be used in the removal of CO2 from crude gas streams on an off-shore oil platform, under more severe operating conditions, dictated by pressure and composition of the gas stream to be treated.
The present invention aims to study a process or manufacturing techniques for the production of new nanostructured membranes containing ionic liquids and their derivatives for sequestration of CO2 from natural gas by gaseous permeation.
The invention carried out made it possible to obtain polymeric membranes that are more selective to CO2 (carbon dioxide) in relation to CH4 (methane) through the impregnation of polymers (such as PVA and PEBAX®) with ionic liquids (such as protics based on N-methylethanolamine, using various manufacturing techniques). These membranes withstand high operating pressures (currently up to 50 bar) and extract CO2 from methane mixtures containing a content between 10%-50% CO2. The membranes are stable over time, maintaining in addition to the permeability-selectivity binomial, their physicochemical and mechanical properties.
Polymers sold as PEBAX® are thermoplastic elastomers, more specifically amide/polyether copolymers.
As general and specific advantages configured by this invention, it is notorious that membrane separation processes present an excellent alternative to conventional separation systems and methods that have greater weights, volumes and areas of occupation, in addition to higher operating costs. These are processes that do not involve phase change and are therefore more cost-effective in terms of the energy required. In addition, membrane separation processes minimize environmental impacts, respecting current standards/legislation, due to the absence of chemicals and tailings generated in the process.
In addition, membrane separation processes can be easily integrated into other units/processes already in operation, and the equipment used in membrane separation processes is compact and modular, suitable for system scaling, as well as easy to install and maintain.
The production of polymeric membranes does not present high costs and technical difficulties on a laboratory scale.
Protic ionic liquids based on N-methylethanolamine are additives capable of considerably increasing the performance of polymeric membranes without loss of mechanical properties, with ease and lower production cost compared to other ionic liquids.
The technique of spraying polymeric solutions under a substrate explored here allows the manufacture of flat composite membranes, of the type found in commercial membranes, with thin selective layers and high performance, with versatility and possibility of application with various polymers and supports.
Polymeric membranes containing protic ionic liquids based on N-methylethanolamine can have high performance and replace the current commercial membranes, representing savings in the area of membrane used as well as in the productivity of the natural gas enrichment process.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
To facilitate an easier understanding of the invention, Figures numbered 1-11 are provided for illustrative purposes, but without the intention of limiting the invention. These figures accompany this specification and are an integral part of it.
The present invention describes a process or techniques for the preparation of polymeric membranes, which can be nanostructured hybrids, containing ionic liquids (IL) and their derivatives for sequestration of CO2 from natural gas by gaseous permeation, and its referred membranes. The membranes of the present invention can be dense flat membranes, or composite asymmetric flat membranes.
In an embodiment, the present invention aims at a process for the preparation of a flat dense polymeric membrane, which comprises the steps of:
In another embodiment, the present invention also aims at a process of preparation of a polymeric, asymmetric flat composite membrane, which comprises the steps of:
Preferably, a process of the present invention, as described above, of preparation of a flat dense polymeric membrane or of preparation of a polymeric, asymmetric flat composite membrane, may additionally comprise a crosslinking reaction for stabilization of a polymer (1a) when required. In this case, such an optional step (b′) occurs after the addition of the protic ionic liquid (1c), before the next step.
According to the present invention, polymer (1a) can be selected from polymer for the production of polymeric solutions (PVA, glutaraldehyde). Meanwhile, polymer (1b) can be selected from polymer for the production of amide/polyether copolymer polymeric solutions.
Regardless of the type of process of the present invention, whether it is aimed at the preparation of a flat dense polymeric membrane or the preparation of a polymeric, asymmetric flat composite membrane, in step (a), the solvent used is in a range of about 3 to about 7% w/w.
According to the processes of the present invention, the protic ionic liquid (IL) (1c) can be selected from protic ionic liquid based on N-methylethanolamine ([m−2-HEA][Pr]). In step (b) of the processes according to the present invention, the mentioned protic ionic liquid (IL) (1c) based on N-methylethanolamine (NMEA) can be added in ratios ranging from 60 to 80% w/w of the polymer mass in the solution.
The polymer solution plus the IL is arranged in an inert coated base for slow evaporation of the solvent and generation of the dense membrane, preferably a flat dense polymeric membrane (item 2, in
The addition of an IL that is selective to CO2, and has low interaction with CH4, aims to improve the performance of membranes, increasing their permeability to CO2 without also increasing the permeability to CH4, aiming to increase productivity in natural gas processing. For the membrane to be stable, the IL must be compatible with the polymeric matrix used, and for the proposed ionic liquids, it is ideal to use polymers that have polar groups.
According to a process of this invention, dense membranes are obtained and the properties of these dense membranes are evaluated. The polymeric solutions produced are then used as a selective layer to coat a commercially available porous support, such as a support membrane (commercial/PVDF) used for the production of flat composite membranes. The porous support must be a partially hydrophobic membrane with porosity in the microfiltration and ultrafiltration ranges, and commercial membranes or membranes produced with the appropriate characteristics may be used.
A porous membrane suitable for use as a support can be produced using the phase inversion method, which consists of dissolving a polymer in a suitable solvent, e.g., a polymeric solution (PVDF (polyvinylidene fluoride), NMP (N-methyl-2-pyrrolidone), adipic acid), followed by spreading this polymeric solution with a controlled thickness extensometer over an inert surface, and ending with the precipitation of this polymer in a non-solvent bath, such as pure water.
The production of composite membranes can be accomplished by various available techniques, including the spray or misting technique. The deposition of polymeric solutions containing the ionic liquid N-methyl-2-hydroxyethylammonium propionate ([m-2-HEA][Pr]) on the supports can be conducted with the use of paint guns or airbrushes, which allow the obtaining of thin and homogeneous selective layers, enabling the manufacture of membranes with high performance and mechanical strength. The composite membranes obtained, typically those containing a selective layer (PB_LI) sprayed on a porous support, can have an additional coating, also by the misting technique, using polymeric solutions of ultra-permeable silicone elastomers, which eliminate the inconvenience of eventual failures and defects on the surface of the selective layer, thus increasing the membrane selectivity.
Preferably, when the protic ionic liquid used is based on N-methylethanolamine, it is used in ratios ranging from about 60 to about 80% w/w of the polymer mass in the solution.
Preferably, the flat dense membranes (item 2, in
Two dense membranes were manufactured from two different polymers containing a protic ionic liquid based on N-methylethanolamine. The performance of the membranes was evaluated to determine their permeability properties (barrer) and actual selectivity.
The tests were conducted on a bench scale using a system similar to the schematic representation in
Two composite membranes were produced from the PB_LI solution, with higher permeability, using the misting method described in
The permeability (p—in Barrer) is determined from the change in pressure as a function of time in the permeate chamber of volume known through Eq. 1.
Where:
The permeance (in GPU) is calculated by Eq. 1 without multiplying by the thickness term and is applied in the calculation for composite membranes. Selectivity can be calculated as the ratio of the permeability of the more permeable gas i to the less permeable gas j, using Eq. 2. When the permeability of pure gases is employed, S is defined as optimal selectivity. When the permeabilities of gases in
mixtures are used, S represents the actual selectivity.
Where:
A flat dense membrane identified as PVAR_LI was manufactured as per
Then, propionic acid is added to adjust the pH up to 5 and a crosslinking agent, which can be glutaraldehyde, in a ratio of 0.1% w/w of the polymer mass in the solution. After 10 minutes of reaction, a protic ionic liquid (IL) based on N-methylethanolamine is added, in this case N-methyl-2-hydroxyethylammonium propionate ([m-2-HEA][Pr]) (1c), in a ratio of 80% w/w of the polymer mass in the solution. The pH is readjusted to 5 and stirring is maintained until the end of the reaction for 60 minutes. The synthesis of the pure membrane (called PVA) as the basis of comparison is carried out without the addition of the ionic liquid. The solutions produced are left to rest to remove air bubbles and poured onto a covered neutral base for slow evaporation of the solvent and formation of dense membranes (2).
Permeation tests were performed with pure gases CO2 and CH4 separately at a pressure of 6 bar. The membranes showed a permeability of about 55 barrer and optimal selectivity CO2/CH4 of 44, much higher than the transport properties of pure polymer (PVA), which did not show permeation for either gas (barrier properties) (
A flat dense membrane identified as PB_LI was manufactured as per
Then, a protic ionic liquid based on N-methylethanolamine, in this case [m-2-HEA][Pr](1c), is added in a ratio of 60% w/w of the polymer mass in the solution, and stirring is maintained for 60 minutes at room temperature. The synthesis of the pure membrane (called PB) as the basis of comparison is carried out without the addition of the ionic liquid. The solutions produced are left to rest to remove air bubbles and poured onto a covered neutral base for slow evaporation of the solvent and formation of dense membranes (2).
The permeation tests were performed with pure gases CO2 and CH4 separately at a pressure of 6 bar, in the system represented in
A flat composite membrane identified as DUR_PB_LI was manufactured as per
The misting conditions are as follows:
After final drying, a thin layer of silicone elastomer was applied to the membrane surface, to correct any defects present in the selective layer. The morphology of the composite membrane (8) is shown in
The permeation test was performed with pure gases at a pressure of 2 bar and with real mixtures of CH4/CO2 of composition 50/50% w/w, 70/30% w/w and 93/7% w/w in a high-pressure system (
The DUR_PB_LI membrane remained stable during cycles of permeation continuously applied daily at pressures of 10-40 bar of feed, for a mixture with CH4/CO2 of 70/30% w/w composition, over a period of 28 days (
A flat composite membrane identified as PVDF_PB_LI_1 was manufactured as per
The resulting polymeric solution was inserted in an ultrasound bath for 10 minutes and spread on a glass support with the aid of a 200 μm thick stainless steel extensometer (4). The glass support was immediately immersed in a pure water bath (5) for polymer precipitation. The resulting polymeric membrane (6) was dried and fixed on a support for coating by misting.
The generating solution of the PB_LI membrane was diluted in absolute ethanol up to 0.2% w/w polymer in solution. The solution is inserted into an ultrasound bath for 10 minutes and then into the airbrush (7) and misted onto the PVDF membrane. The misting conditions are as follows:
After final drying, a thin layer of silicone elastomer was applied to the membrane surface, to correct any defects present in the selective layer. The morphology of the composite membrane (8) is shown in
The permeation test was performed with pure gases at a pressure of 2 bar and with real mixtures of CH4/CO2 gases of composition 50/50% w/w and 70/30% w/w in a high-pressure system (
A test was performed with a flat commercial membrane under the same conditions as in examples 3 and 4. It should be noted that composite membranes containing ionic liquid showed superior performances compared to commercial membranes in all compositions of gas mixtures evaluated.
A flat composite membrane identified as PVDF_PB_LI_2 was manufactured as per
The resulting polymeric solution was inserted in an ultrasound bath for 10 minutes and spread on a glass support with the aid of a 200 μm thick stainless steel extensometer (4). The glass support was immediately immersed in a pure water bath (5) for polymer precipitation. The resulting polymeric membrane (6) was dried and fixed on a support for coating by misting.
The generating solution of the PB_LI membrane was diluted in absolute ethanol up to 0.2% w/w polymer in solution. The solution is inserted into an ultrasound bath for 10 minutes and then into the airbrush (7) and misted onto the PVDF membrane. The misting conditions are as follows:
After final drying, a thin layer of silicone elastomer was applied to the membrane surface, to correct any defects present in the selective layer.
The permeation test was performed with pure gases at 2 bar and with real mixtures of CH4/CO2 gases of composition 50/50% w/w and 70/30% w/w in a high-pressure system (
The PVDF_PB_LI_2 membrane remained stable during cycles of permeation continuously applied daily at pressures of 10-40 bar of feed, for a mixture with CH4/CO2 of 70/30% w/w composition, over a period of 28 days (
A test was performed with a flat commercial membrane under the same conditions as in examples 3, 4 and 5. It should be noted that composite membranes containing ionic liquid showed superior performances compared to commercial membranes in all compositions of gas mixtures evaluated.
To obtain a dense PVA membrane containing ionic liquid (PVA_LI membrane), the method of the present invention was carried out as follows:
The membrane obtained comprises, as components, polyvinyl alcohol crosslinked with glutaraldehyde containing 80% polymer mass of the ionic liquid [m-2-HEA][Pr] impregnated in the polymeric matrix.
The characterization by Fourier transform infrared spectroscopy (FTIR) of the pure PVA membrane and the membrane PVA_LI containing ionic liquid, obtained by the process according to the present invention, can be seen in
The characterization of the membranes by FTIR confirms the incorporation of IL. The bands at the wavelength of ˜1600 cm−1 are associated with the combination of the C═O stretch and the N—H vibrations of the [m-2-HEA][Pr] and is also found in pure PVA, due to the non-hydrolyzed carbonyl groups in its synthesis. The increase in band intensity is then related to the presence of IL in the polymeric matrix, for the PVA_LI membrane, compared to the pure PVA membrane.
The presence of IL and the crosslinking reaction with glutaraldehyde is associated with a decrease and widening of the ˜3330 cm−1 band, which corresponds to the overlapping of the N—H stretches (secondary amine), C—H and O—H. The band at 1141 cm−1 of the C—O stretch referring to crystallinity in PV has a lower intensity for the PVA_LI membrane, an effect also associated with the addition of IL and the crosslinking reaction.
To obtain an amide/polyether copolymer membrane containing ionic liquid (PB_LI membrane), according to the process of the present invention, the following steps were carried out.
For comparison purposes, the pure amide/polyether copolymer membrane is produced following the steps 1, 2, and 4 described above.
The PB_LI membrane obtained comprises, as components, amide/polyether copolymer containing 60% polymer mass of the ionic liquid [m-2-HEA][Pr] impregnated in the polymeric matrix.
The characterization by Fourier transform infrared spectroscopy (FTIR) of the pure amide/polyether copolymer membrane and the membrane PB_LI containing ionic liquid, obtained by the process according to the present invention, can be seen in
As shown in
To obtain a composite membrane of PB_LI, according to the process of the present invention, the following steps were carried out.
The membrane obtained has the following components: commercial PVDF microfiltration membrane covered with an amide/polyether copolymer layer containing 60% by polymer mass of the ionic liquid [m-2-HEA][Pr] impregnated in the polymeric matrix, and an additional layer of silicone elastomer for the protection of the amide/polyether copolymer layer.
The membrane obtained has the following components: PVDF porous membrane covered with an amide/polyether copolymer layer containing 60% by polymer mass of the ionic liquid [m-2-HEA][Pr] impregnated in the polymeric matrix, and an additional layer of silicone elastomer for the protection of the amide/polyether copolymer layer.
Then, propionic acid is added to adjust the pH up to 5 and a crosslinking agent, which can be glutaraldehyde, in a ratio of 0.1% w/w of the polymer mass in the solution. After 10 minutes of reaction, a protic ionic liquid (IL) based on N-methylethanolamine is added, in this case N-methyl-2-hydroxyethylammonium propionate ([m-2-HEA][Pr]) (1c), in a ratio of 80% w/w of the polymer mass in the solution. The pH is readjusted to 5 and stirring is maintained until the end of the reaction for 60 minutes, under reflux conditions. The synthesis of the pure membrane (called PVA) as the basis of comparison is carried out without the addition of the ionic liquid.
To prepare the PB_LI membrane, 3% w/w of Pebax® MH 1657 (amide/polyether copolymer) (1b) is added to a two-neck flask (ii) containing the solvent (mixture of pure water 30% w/w and absolute ethanol 70% w/w), which is heated under magnetic stirring with the aid of the magnetic bar (iii) and the heating and magnetic stirring plate (iv) until the polymer is completely dissolved. The flask is dipped in a glycerol bath (v) for temperature homogenization. This dissolution occurs under reflux, with the aid of the reflux condenser (i), to prevent evaporation and loss of the solvent to the environment.
Then, a protic ionic liquid based on N-methylethanolamine, in this case [m-2-HEA][Pr](1c), is added in a ratio of 60% w/w of the polymer mass in the solution, and stirring is maintained for 60 minutes at room temperature. The synthesis of the pure membrane (called PB) as the basis of comparison is carried out without the addition of the ionic liquid.
To produce both dense membranes PVA_LI and PB_LI, after the completion of the preparation of the solutions, they are kept at rest for a certain time to remove air bubbles, and poured under a coated neutral base for slow evaporation of the solvent and formation of the dense membranes. These procedures are represented by images 1.2 and 1.3 in
Finally, the dense membranes are submitted to permeation experiments with pure gases to evaluate their performance, in the system represented by the flowchart depicted in image 1.4 of
The pure gas is fed into the upper compartment of the permeation cell at a constant pressure and room temperature, and the lower compartment is sealed under room pressure. As the gas permeates the membrane and becomes confined, the pressure in the lower compartment increases, and the variation over time is recorded by a pressure transducer. Data acquisition is performed by a computer. The experiments were carried out under a feed pressure of 6 bar.
To perform the stability tests, the gases CO2 or CH4 were continuously applied at a pressure of 6 bar for a period of 1 month, in cycles of about 12 h of permeation for each gas. The permeate accumulated in the lower part of the cell was continuously discarded into the environment.
The apparatuses and materials used are described below:
Composite membranes PVDF_PB_LI_1 and PVDF_PB_LI_2 are produced in a similar manner; however, the porous polymeric membrane used as a support is produced in the laboratory. Thus,
For the preparation of the DUR_PB_LI composite membrane, the polymeric solution produced according to the methodology described in
The membrane that acts as a support (item 6 of
To prepare the composite membranes PVDF_PB_LI_1 and PVDF_PB_LI_2, the porous membrane used as a support was first prepared. The porous membrane is produced by the phase inversion technique. This technique consists of inducing phase separation in a homogeneous polymeric solution, which is promoted by immersing the polymeric solution in a non-solvent bath, to modify the equilibrium condition of the polymer/solvent system through its destabilization.
A KYNAR 500® PVDF polymeric solution is prepared with a PVDF concentration of 20% w/w in n-methyl-2-pyrrolidone (NMP) solvent at 75% w/w, and with the addition of adipic acid as an additive, at a concentration of 5% w/w. The reagents are mixed together under magnetic stirring and heating at 60° C., until homogenization of the polymeric solution (item 3 of
The porous membrane is then fixed to a glass plate, acting as a support (item 6 of
For the PVDF_PB_LI_1 membrane, the airbrush is pressurized to 30 psi and the solution is misted at a distance of about 10 cm from the porous support. Then, the assembly is left to rest in the environment for 10 minutes, to dry the selective layer. This procedure is repeated for another 5 times. For the PVDF_PB_LI_2 membrane, the airbrush is pressurized to 20 psi and the solution is misted at a distance of about 10 cm from the porous support. Then, the assembly is left to rest in the environment for 10 minutes, to dry the selective layer. This procedure is repeated for another 6 times.
At the end of the last misting cycle, both membranes are dried in an oven at 60° C. for a period of 1 hour, and then in a fume hood at room temperature, to ensure the evaporation of the remaining solvent, for 12 h.
After the final drying of the three composite membranes DUR_PB_LI, PVDF_PB_LI_1 and PVDF_PB_LI_2 described, a thin layer of silicone elastomer is applied to the surface of the membranes with an airbrush (item 7 of
It is possible to observe the porous support containing a thin dense layer on its surface, which is the selective dense layer produced by the misting procedure. It is observed in the cross-section at a magnification of approximately 15,000×in
It is possible to observe the porous support containing a thin dense layer on its surface, which is the selective dense layer produced by the misting procedure. The cross-section is observed at a magnification of approximately 15,000×in
The apparatuses and materials used were listed in the image, and are described below:
The high pressure system works in a similar way to the benchtop system described in
However, the permeate outlet in the membrane containing cell of the high-pressure system is directly connected to a mass spectrometer. The equipment performs the analysis of the permeate composition. From the partial pressure of each gas in the feed and in the composition obtained by the mass spectrometer, it is possible to determine the (real) selectivity of the tested membrane for the mixture.
Different gas mixtures were used in the feed in the experiments. Mixtures containing 50% CO2/50% CH4 w/w and 30% CO2/70% CH4 w/w were used. The feed pressures ranged from 10 to 40 bar.
The graph in
The PVAR_LI membrane showed a permeability of about 55 barrer and optimal selectivity CO2/CH4 of 44, much higher than the transport properties of pure polymer PVA, which did not show permeation for either gas (permeability =0 barrer; barrier properties).
The PB_LI membrane showed a permeability of about 143 barrer and optimal selectivity CO2/CH4 of 32, much higher than the transport properties of pure polymer (PB), whose permeability was 87 and optimal selectivity CO2/CH4 of 27. The addition of IL generated a 64% increase in permeability and a 19% increase in pure polymer selectivity.
The results described show that the addition of IL to the polymers resulted in a substantial increase in the permeability to CO2 compared to pure polymers, without sacrificing selectivity, which proves the beneficial effect of the additive.
The DUR_PB_LI membrane showed permeances of 78, 52, 64 and 60 GPU and selectivities of 18, 10, 9 (real) and 16 (ideal) for the amount of CO2 in the feed of 7, 30, 50 (mixtures) and 100% w/w (pure gas), respectively. The PVDF_PB_LI_1 membrane showed permeances of 44, 49 and 63 GPU and selectivities of 17, 16 (real) and 33 (ideal) for the amount of CO2 in the feed of 30, 50 (mixtures) and 100% w/w (pure gas), respectively. The PVDF_PB_LI_2 membrane showed permeances of 49, 59 and 73 GPU and selectivities of 11, 10 (real) and 27 (ideal) for the amount of CO2 in the feed of 30, 50 (mixtures) and 100% w/w (pure gas), respectively.
It is possible to observe that all the composite membranes produced presented permeances higher than those of the commercial membrane in the experiments with gas mixtures, for all the compositions evaluated. In an experiment containing a high concentration of CH4 (7% of CO2), the DUR_PB_LI membrane showed a tendency to increased permeance, with a much higher result than that of the commercial membrane. The results show that there is a tendency to increase the permeance of CO2 in the compositions between 50 and 100% as the amount of CO2 in the mixture increases, a behavior also observed for the commercial membrane.
These results indicate that the polymeric solutions developed and the techniques used were both efficient for the production of composite membranes with competitive performance in the separation of mixtures of CO2/CH4. Both the production of composite membranes from a commercial support (DUR_PB_LI) and those made from a produced support (PVDF_PB_LI_1 and 2) presented competitive performances.
Changing the parameters allows to generate membranes with slightly different performances. The PVDF_PB_LI_1 membrane showed permeances closer to that of the commercial membrane and lower than that of the other two membranes produced, but exhibited superior selectivities. The results demonstrate the efficiency of the misting technique in the production of composite membranes, as well as its flexibility, since it is possible to obtain competitive performances with different supports and misting parameters.
In these experiments, the mixture CO2/CH4 with a ratio of 70/30% w/w was fed at a continuous pressure of 10 bar. In some periods, the pressure was increased to 40 bar, in order to obtain data for measuring the actual permeance and selectivity. At the end of the data acquisition, the feed pressure was again lowered to 10 bar. During the continuous permeation time, there was no accumulation of permeate or concentrate in the system, and both were released into the environment.
It is possible to observe in the graphs that, during the period evaluated, the results of actual permeance and selectivity showed little variation, which is probably the result of the intrinsic standard deviation of the analysis itself. The performance of both membranes remained practically similar to that exhibited in the initial experiments.
This experiment demonstrates that, during a total time of 1 month, the composite membranes produced by the misting technique on two different supports with the PB_LI solution showed stability compared to the use in the separation of a gas mixture with a ratio of 70/30 CH4/CO2, at pressures ranging from 10 to 40 bar. This result is extremely important, since it demonstrates a trend towards a long membrane lifespan, essential to enable its use in industrial systems.
In some examples, the present disclosure may involve one or more of the following clauses:
Clause 1. A process for the preparation of a flat dense polymeric membrane containing one or more ionic liquids and their derivatives for sequestration of CO2 from natural gas by gaseous permeation, comprising the steps of:
Clause 2. A process for the preparation of a polymeric, asymmetric flat composite membrane containing one or more ionic liquids and their derivatives for sequestration of CO2 from natural gas by gaseous permeation, comprising the steps of:
Clause 3. The process according to clause 1, further comprising step (b′) after the addition of the protic ionic liquid (1c), in which one or more additives are added to promote the crosslinking reaction of the polymer (1a).
Clause 4. The process according to clause 1, wherein the polymer (1a) is selected from polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), or their derivatives, and wherein the polymer (1a) is aggregated with glutaraldehyde.
Clause 5. The process according to clause 1, wherein the polymer (1b) is selected from amide/polyether copolymers (PEBA) or their derivatives.
Clause 6. The process according to clause 1, wherein in step (a), the solvent used is in the range of 3-7% w/w.
Clause 7. The process according to clause 1, wherein the NMEA-based protic ionic liquid is N-methyl-2-hydroxyethylammonium propionate ([m-2-HEA][Pr]).
Clause 8. The process according to clause 1, wherein in step (b), the protic ionic liquid (IL) (1c) based on NMEA is added in an amount ranging from 60 to 80% w/w of the polymer mass in the solution.
Clause 9. The process according to clause 2, further comprising step (b′) after the addition of the protic ionic liquid (1c), in which one or more additives are added to promote the crosslinking reaction of the polymer (1a).
Clause 10. The process according to clause 2, wherein the polymer (1a) is selected from polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), or their derivatives, and wherein the polymer (1a) is aggregated with glutaraldehyde.
Clause 11. The process according to clause 2, wherein the polymer (1b) is selected from amide/polyether copolymers (PEBA) or their derivatives.
Clause 12. The process according to clause 2, wherein in step (a), the solvent used is in the range of 3-7% w/w.
Clause 13. The process according to clause 2, wherein the NMEA-based protic ionic liquid is N-methyl-2-hydroxyethylammonium propionate ([m-2-HEA][Pr]).
Clause 14. The process according to clause 2, wherein in step (b), the protic ionic liquid (IL) (1c) based on NMEA is added in an amount ranging from 60 to 80% w/w of the polymer mass in the solution.
Clause 15. A polymeric membrane obtained by the process as defined in clause 1, wherein the polymeric membrane is a flat dense membrane comprising glutaraldehyde-cross-linked polyvinyl alcohol, and wherein the membrane contains the ionic liquid [m-2-HEA][Pr] in an amount of 80% of polymer mass impregnated in the polymer matrix.
Clause 16. A polymeric membrane obtained by the process as defined in clause 1, wherein the polymeric membrane is a flat dense membrane comprising amide/polyether copolymer, and wherein the membrane contains the ionic liquid [m-2-HEA][Pr] in an amount of 60% of polymer mass impregnated in the polymeric matrix.
Clause 17. A polymeric membrane obtained by the process as defined in clause 2, wherein the polymeric membrane is an asymmetric flat composite membrane comprising a commercial microfiltration PVDF membrane coated with an amide/polyether copolymer layer, and wherein the membrane contains the ionic liquid [m-2-HEA][Pr] in an amount of 60% of polymer mass impregnated in the polymeric matrix, and an additional layer of silicone elastomer for the protection of the amide/polyether copolymer layer.
Clause 18. A polymeric membrane obtained by the process as defined in clause 2, wherein the polymeric membrane is an asymmetric flat composite membrane comprising a PVDF porous membrane coated with an amide/polyether copolymer layer, wherein the membrane contains the ionic liquid [m-2-HEA][Pr] impregnated in an amount of 60% of polymer mass in the polymeric matrix, and an additional layer of silicone elastomer for the protection of the amide/polyether copolymer layer.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1020230256597 | Dec 2023 | BR | national |
