CO2 Feed Concentration Research Articles

Constraining CO2 Coverage on Copper Promotes CO2 Electroreduction to Multi‐carbon Products in Strong Acid

Electrocatalytic CO2 reduction (CO2R) to multi‐carbon (C2+) products in strong acid presents a promising approach to mitigate the CO2 loss commonly encountered in alkaline and neutral systems. However, this process often suffers from low selectivity for C2+ products due to the competing C1 (e.g., CO and HCOOH) formation and complex C‐C coupling kinetics. In this work, we report a CO2 coverage constraining strategy by diluting CO2 reactant feed to modulate the intermediate distribution and C‐C coupling pathways for an enhanced electrosynthesis of C2+ products in strong acid. Lowering the CO2 feed concentration reduces CO2 coverage on copper catalyst, enriching the surface coverage and optimizing the adsorption configuration of the key CO intermediate for C‐C coupling. This approach efficiently suppresses the formation of undesired C1 products. By employing a 20% CO2 feed, we achieved a significant improvement in C2+ Faradaic efficiency, reaching 68% at 100 mA cm‐2, approximately 1.7 times higher than the 41% obtained using pure CO2. We demonstrated the direct electroreduction of a 30% CO2 feed – representative CO2 concentration of typical industrial flue gases – in a full electrolyzer, achieving a C2+ selectivity of 78% and an energy efficiency of 23% at 200 mA cm‐2.

Constraining CO2 Coverage on Copper Promotes CO2 Electroreduction to Multi-carbon Products in Strong Acid.

Electrocatalytic CO2 reduction (CO2R) to multi-carbon (C2+) products in strong acid presents a promising approach to mitigate the CO2 loss commonly encountered in alkaline and neutral systems. However, this process often suffers from low selectivity for C2+ products due to the competing C1 (e.g., CO and HCOOH) formation and complex C-C coupling kinetics. In this work, we report a CO2 coverage constraining strategy by diluting CO2 reactant feed to modulate the intermediate distribution and C-C coupling pathways for an enhanced electrosynthesis of C2+ products in strong acid. Lowering the CO2 feed concentration reduces CO2 coverage on copper catalyst, enriching the surface coverage and optimizing the adsorption configuration of the key CO intermediate for C-C coupling. This approach efficiently suppresses the formation of undesired C1 products. By employing a 20% CO2 feed, we achieved a significant improvement in C2+ Faradaic efficiency, reaching 68% at 100 mA cm-2, approximately 1.7 times higher than the 41% obtained using pure CO2. We demonstrated the direct electroreduction of a 30% CO2 feed - representative CO2 concentration of typical industrial flue gases - in a full electrolyzer, achieving a C2+ selectivity of 78% and an energy efficiency of 23% at 200 mA cm-2.

Modelling carbon capture from power plants with low energy and water consumption using a novel cryogenic technology

Global warming mitigation requires modern energy generation technology to integrate low-cost carbon capture techniques. Despite volumes of research on the latter, the significantly high unit energy (MWh) of capture and high water consumption, do not enable any current carbon capture techniques to be adopted at a scale. To address this problem, we theoretically explore a novel low-cost carbon capture technology (NLCCT). In this paper, a detailed thermodynamic analysis of the effects of the operating conditions and parameters of NLCCT, such as the initial feed gas concentration, compressor intercooler temperature, number of compressor stages, efficiencies of the compressors, and turbines, ambient temperatures on the energy consumption for CO2 capture (ECC) is carried out with a view to obtain costs much lower than current techniques. The study identifies the inlet feed concentration, turbine and compressor efficiencies, and compressor intercooler temperatures (heat transfer effectiveness) as the significant parameters. For a drop of 20 % efficiency, the ECC was found to increase by 40 %, and for an increase in inlet CO2 feed concentration from 4 % to 10 %, the ECC was found to decrease by 31 %. Considering the effect of intercooler temperatures, the ECC increases by 25 % when the intercooler temperature is raised by 6 K. The effect of ambient conditions was also analyzed and observed that for an increase of 27C in the ambient temperature, the ECC would rise by 15 %.

CFD simulation for CO2 separation using diamond-structured thermally rearranged (TR) polymer membrane: Effect of CO2 feed concentration, feed pressure and temperature

Abstract CO2 separation in natural gas purification is important in improving the properties of natural gas such as energy content, volume and corrosivity. Membrane separation using TR-450 polymer membrane is a potential approach to remove CO2 from natural gas efficiently. The study of CO2/CH4 binary gas mixture separation was simulated using a thermally-rearranged (TR) HAB- 6FDA membrane at 450 °C with a partial part of Schwarz Diamond structure because it exhibits advanced mechanical properties with low stiffness for relatively high strength. TR-450 membrane exhibits excellent separation performance that has the potential to exceed the Robeson plot 1991. Computational fluid dynamics (CFD) was used to simulate the fluid behavior within the geometry created using CAD software. The effect of feed pressure, temperature and CO2 feed concentration on the separation performance of TR-450 membrane was also studied. The results indicated that an increase in feed pressure leads to a decrease in CO2 recovery, hence the lower separation performance. It was also found that increasing the feed temperature leads to an increase in CO2 recovery. Concerning the concentration of CO2 in the feed, elevated levels impact the performance of membrane separation. The enhanced membrane separation performance demonstrated by the TR-450 membrane under various conditions underscores the necessity for additional investigation to unveil its potential in industrial gas separation applications.

Unveil carbon dioxide recycling potential throughout distributor-type membrane reactor

With the cost of green hydrogen production decreasing year by year, methanation, a carbon dioxide hydrogenation reaction, is becoming a more critical technology for the realization of a carbon-neutral society. Here, we show the procedure of membrane preparation for a distributor-type membrane reactor that simultaneously captures and recycles CO2 together with experimental tests of the proposed reactor design. To decrease the temperature gradient in the reactor and to improve methane recovery from the inlet gas mixture, a three-dimensional computational fluid dynamics simulation of the reactor was conducted. The numerical results suggest that the distributed feed design results in a uniform distribution of carbon dioxide, preventing localized reactions at the reactor inlet. In addition, it reduces the temperature rise in the reactor by up to about 300 K compared to the case where the carbon dioxide and hydrogen gas mixture is fed from a single inlet. The effect of the feed CO2 concentration on reactivity is also discussed. Simulation results show that the membrane reactor with inlet concentration of about 15 %, such as those emitted from industrial boilers, is capable of recovering methane at concentrations about 1.5 times higher in comparison to 100 % CO2 concentration at the inlet in a classical reactor.

Optimizing carbon capture efficiency with direct capturing and amine: Insights from exegetic analysis

AbstractWith climate change concerns on the rise, finding efficient and sustainable ways to separate carbon dioxide from industrial gas mixtures has become increasingly important. Membrane‐based gas separation technologies offer a promising solution due to their low energy consumption, low emissions, and ease of operation. In this study, we dug deep into theoretical energy consumption and practical optimization strategies for CO2 separation using such technologies. Our results showed that CO2 separation can be achieved with relatively low specific energy consumption, ranging from 0.09 to 0.27 MJe/kg CO2, depending on feed CO2 concentration. By conducting process simulations, we determined the optimal feed gas pressure and membrane surface area required to achieve a CO2 absorption ratio of 90% (mol). We also analyzed the effects of CO2 permeation and selectivity on energy consumption and membrane area, revealing that increasing both can significantly reduce energy consumption, albeit with more membrane surface area required. Using seepage flow circulation was found to be a particularly effective way to improve feed CO2 concentration and reduce energy consumption. To optimize and improve the capturing process, we conducted exergy analysis in each of the five stages of optimization, reporting Cooling Utilities (MW), Heating Utilities (MW), and Total Utilities (MW) for each step. Our results showed that in the optimal mode, Total Utilities (MW) were reported as 228.1, highlighting the potential of membrane‐based CO2 separation for carbon capture and storage applications. This study provides valuable insights and practical strategies for achieving efficient and sustainable CO2 separation.

CO2 Physisorption over an Industrial Molecular Sieve Zeolite: An Experimental and Theoretical Approach.

The present work studies the adsorption of CO2 using a zeolitic industrial molecular sieve (IMS) with a high surface area. The effect of the CO2 feed concentration and the adsorption temperature in conjunction with multiple adsorption-desorption cycles was experimentally investigated. To assess the validity of the experimental results, theoretical calculations based on well-established equations were employed and the values of equilibrium, kinetic, and thermodynamic parameters are presented. Three additional column kinetic models were applied to the data obtained experimentally, in order to predict the breakthrough curves and thus facilitate process design. Results showed a negative correlation between temperature and adsorption capacity, indicating that physical adsorption takes place. Theoretical calculations revealed that the Langmuir isotherm, the Bangham kinetic model (i.e., pore diffusion is the rate-determining step), and the Thomas and Yoon-Nelson models were suitable to describe the CO2 adsorption process by the IMS. The IMS adsorbent material maintained its high CO2 adsorption capacity (>200 mg g-1) after multiple adsorption-desorption cycles, showing excellent regenerability and requiring only a mild desorption treatment (200 °C for 15 min) for regeneration.

Zeolite-coated fin–coil heat exchanger for CO2 recovery from simulated dry flue gas via low-temperature-heat-driven TSA

Adsorbent-coated heat exchangers are expected to achieve not only high adsorption and desorption rates based on the rapid heat transfer in their adsorbent layers but also a low pressure drop owing to their structured adsorbent layers. In this study, a CaA-zeolite-coated adsorber was experimentally investigated to improve the CO2 capture performance of low-temperature-heat-driven temperature swing adsorption (TSA) from dry flue gas, a major source of greenhouse gas emissions. At a feed CO2 concentration of approximately 10 vol%, a flow rate of 1 L-STP/min, and a temperature swing range of 20 °C–80 °C, the performance of the coated adsorbent was first compared with that of a heat exchanger of a similar volume packed with CaA zeolite pellets. Due to the enhancement in heat transfer of the coated adsorbent, almost the same CO2 concentration and a higher CO2 recovery ratio as those of the packed adsorbent were obtained at an appropriate cycle time despite that the amount of coated adsorbent was only one-third that of the packed adsorbent. Therefore, the accelerated heat transfer in the adsorbent layer significantly affected the increased mass transfer rate in or around the coated adsorbent. Next, the effect of the space velocity (SV) was investigated using a coated heat exchanger that had a three-times-longer length in the gas flow direction and approximately the same thickness of the adsorbent coating layer as the above coated heat exchanger. Although a separate discussion on the larger adsorber size is necessary, the CO2 recovery concentration was over 50% and the recovery ratio exceeded 80% as the SV was reduced by one-third. Furthermore, the fin pitch of the heat exchanger was doubled and the thickness of the adsorbent coating was doubled while maintaining the same volume of the heat exchanger and the same amount of adsorbent coating. This was done to reduce the heat capacity of the heat exchanger, which is a factor in heat loss in TSA, by reducing the number of fins used. The doubled adsorbent coating layer thickness and halved contact area with the gas flow resulted in a decrease in CO2 capture. Thus, the effects of an increased adsorbent layer thickness and a reduced contact area should be determined to further increase the effectiveness of the adsorbent-coated heat exchangers.

Liquid-liquid equilibrium of CO2/bitumen and CO2/bitumen/ethyl acetate systems with application to diluted bitumen transportation

Bitumen transportation by pipelines requires dilution with solvents. These diluents are often expensive. Therefore, the utilization of liquid CO2 as a diluent to reduce or eliminate diluent consumption is of interest. However, there is limited data in the literature on the liquid-liquid equilibrium (LLE) of CO2 and bitumen. In this work, we report a new set of LLE data for MacKay River bitumen and liquid CO2 at ambient temperature. First, the LLE of bitumen/CO2 at various CO2 feed concentrations was studied. The density of light and heavy liquid phases, the viscosity of the heavy phase, and the heavy phase volume fraction were measured. It was shown that a CO2 feed concentration of 30 wt% is optimum for achieving maximum dissolution of CO2 in bitumen. Then, the effect of pressure on the LLE of bitumen/CO2 at a 30 wt% CO2 concentration was studied. The results revealed a significant reduction in bitumen viscosity from 300,000–1250 cP could be achieved at 21 °C. The results suggest that liquid CO2 can be utilized to reduce diluent consumption in pipeline transportation. The role of ethyl acetate (EA) as a co-solvent with CO2 was also examined. It was shown that the addition of EA to a mixture of bitumen/CO2 could further reduce the bitumen viscosity to satisfy the pipeline transportation criterion. The results reveal that CO2-assisted bitumen transportation in Canada can lead to the utilization of 0.16 Mt of CO2 daily, which is equivalent to a utilization potential of about 80 kg CO2/bbl of raw bitumen. The results also suggest a 73% reduction in fossil-based diluent usage, equivalent to ∼0.5 million barrels of crude oil.

Effective CO2 capture by using poly (acrylonitrile) nanofibers based on the radiation grafting procedure in fixed-bed adsorption column

In this study, a new adsorbent was investigated for CO2 adsorption in the fixed-bed column. Poly (acrylonitrile) nanofibers were prepared by electrospinning, then grafting under gamma irradiation with glycidyl methacrylate (GMA). Then, the nanofibers were modified with ethanolamine (EA), diethylamine (DEA) and triethylamine (TEA) to adsorb carbon dioxide molecules. Dynamic adsorption experiments were performed with a mixture of CH4, CO2 in a constant bed column at ambient pressure and temperature and CO2 feed concentration (5%). The maximum adsorption capacity is 2.84 mmol/g for samples with 172.26% degree of grafting (DG) in 10 kGy. Also, the degree of amination with ethanolamine was achieved equal to 170.83%. In addition, the reduction of the regeneration temperature and the stability of this adsorbent after four cycles indicated the high performance of this adsorbent for CO2 adsorption.

Toward a Stackable CO2-to-CO Electrolyzer Cell Design─Impact of Media Flow Optimization

Aqueous CO2-to-CO electrolysis is a promising technology for closing the carbon cycle and defossilizing industrial processes. Considering the technological readiness, consensus has been achieved about using silver as a stable and selective electrocatalyst for the CO2-to-CO reduction reaction in aqueous electrolyte. On the other hand, challenges such as media flow management, component stability, and force distribution are still associated with improving the process performance and developing a stackable cell concept to meet industrially relevant levels. We therefore report on a promising stack concept with continuous flowcells operated with gas diffusion electrodes (GDEs). To enhance the CO2-to-CO conversion efficiency, dedicated media flow chambers were developed on two levels. In the gas chamber, which touches the GDE from the far side of the anode, the feed gas flow and distribution over the GDE were controlled by introducing various gas path architectures in a modular flowcell. In addition, an ionically conductive spacer was implemented in the catholyte chamber, which is adjacent to the opposite side of the GDE. The effect of these modifications on the cell voltage, selectivity, and overall conversion was investigated at 100 mA/cm2 with varying CO2 feed gas flow and concentration. Noteworthy, an optimized feed gas distribution generated an increase of the Faraday efficiency for CO under reduced CO2 supply. Furthermore, the implementation of the spacer enhanced the process stability by suppressing gas-bubble-induced noise in the cell voltage measurements. By functioning as support structures to the GDE, the combined modifications provided the cell with mechanical integrity and allowed an ionic and electric contact over the full active cell area, which is required for both stacking and upscaling of the cell. The corresponding performance was demonstrated by a two-cell short-stack.

Numerical analysis on the geometrical design of liquid cooling based carbon capture by adsorption for higher thermal efficiency

Thermal design and management is important to improve the CO2 capture by adsorption's efficiency, but current studies only consider geometric designs of a specific size. This paper develops a 2D multi-physics model to study how the spacing between two fluid pipes in the adsorbent bed affects the desorption performance, which couples the species transport, fluid dynamics, and heat transfer modules. Specifically, the model involves sandwiching the adsorbent bed between two fluid pipes, which will be parametrically studied in terms of the CO2 desorption performance, with indicators being the thermal efficiency, and the speed of CO2 desorption. Results reveal that a trade-off exists where the desorption speed decreased from 0.9 to 0.05 mol/(m3 s) when the bed height changes from 1 cm to 10 cm, but the thermal efficiency will correspondingly increase from 0.52 to 0.85. Furthermore, a sensitivity analysis on this trade-off situation is conducted by varying the thermal conductivity, regeneration temperature, CO2 feed concentration, and applying thermally conductive fins. Results reveal that increasing the thermal conductivity provides the most reasonable performance improvement characteristics as it halved the desorption time while the specific energy consumption for CO2 capture remains largely unaffected.

Biogas upgrading to natural gas pipeline quality using pressure swing adsorption for CO2 separation over UiO-66: Experimental and dynamic modelling assessment

Biogas upgrading (CO2 removal) is an important process to produce biomethane that meets the fuel quality standards or pipelines injection specifications. Assessment of microporous UiO-66 as a potential adsorbent for CO2 removal from biogas was performed to gauge the viability of the media for methane purification and CO2 removal in pressure swing adsorption under non-isothermal conditions. UiO-66 was synthesized and characterized using various analysis tools such as SEM, BET, FTIR, XRD, TGA, particle size distribution, and TPD. A dynamic model for the proposed PSA system was built to study the effects of some parameters i.e., outside temperature, length/diameter ratio, and CO2 feed concentration on the purity and recovery of the product gases. The developed model was validated by comparing the simulation and experimental data from CH4 and CO2 breakthrough curves under similar operating conditions and adsorption bed geometry. A central composite design method was employed to optimize and examine the interaction effects of the studied parameters on the PSA system. The results confirmed the high separation performance of the PSA system using UiO-66 adsorbent with bioCH4 purity of 98.2 % and recovery of 94.68 %. The RSM model showed that the studied parameters possessed significant effects on PSA performance. The optimized parameters for achieving maximum purity and recovery were operating temperature of 290 K, length/diameter ratio of 5.6 and CO2 concentration of 39 %. Under those optimized conditions, the PSA cycle over UiO-66 recorded a purity of 99.99 %, recovery of 99.99 %, and system productivity of 8.57 mol/kg.hr.

Capture of CO2 from Steam Reformer Flue Gases Using Monoethanolamine: Pilot Plant Validation and Process Design for Partial Capture

Carbon dioxide (CO2) capture from a slipstream of steam reformer flue gas (18–20 vol %wet CO2) using 30 wt % aqueous monoethanolamine was performed for ∼500 h in a mobile test unit (∼120 kg CO2/h). Specific reboiler duties (SRDs) of 3.6–3.8 MJ/kg CO2 were achieved at 90% capture. The pilot data validate the modeling of off-design partial capture, that is, operation at lower CO2 capture rates (at constant gas flow) than the absorption column was designed to achieve. This paper demonstrates that off-design partial capture enables significant energy savings (SRD, cooling) relative to on-design capture. The accrued savings depend on the column design (packing height, flooding approach) and the feed CO2 concentration. Finally, a concept for stepwise deployment of carbon capture and storage in industries with high-CO2 concentration sources (e.g., steel and cement manufacturing and refining) is introduced. Thanks to its inherent full-capture-ready design, the initial energy-efficient, off-design partial capture operation can be extended to full capture over time.

Effect of Hydrothermal Carbonization Parameters and Performance of Carbon Dioxide Adsorption on Pineapple Peel Waste Biochar

AbstractLow‐cost biochar adsorbents were prepared from pineapple peel waste (PPW) via hydrothermal carbonization (HTC) for CO2 capture. The effects of hydrothermal carbonization temperature, retention time, and heating rate were studied. The hydrochar samples were further carbonized to produce pineapple peel biochar adsorbents. The effects of CO2 concentration in the feed, adsorption temperature, and feed flow rate on adsorption capacity were investigated in a fixed‐bed column adsorption system. The experimental data were analyzed using pseudo‐first‐order and pseudo‐second‐order kinetics, and the Avrami equation. The CO2 adsorption capacity of this system was improved with increasing CO2 feed concentration and decreased with rising temperature and feed flow rate. The Avrami kinetics model was best fitted to the experimental data. The CO2 adsorption performance of PPW biochar (PPW‐BC) in a fixed‐bed column was successfully predicted by the Thomas and Yoon‐Nelson models. The prepared PPW‐BC adsorbents could be a viable option for CO2 capture because they were synthesized from a low‐cost biomass source and are environmentally benign.

RSM Modeling and Optimization of CO2 Separation from High CO2 Feed Concentration over Functionalized Membrane.

The challenges in developing high CO2 gas fields are governed by several factors such as reservoir condition, feed gas composition, operational pressure and temperature, and selection of appropriate technologies for bulk CO2 separation. Thus, in this work, we report an optimization study on the separation of CO2 from CH4 at high CO2 feed concentration over a functionalized mixed matrix membrane using a statistical tool, response surface methodology (RSM) statistical coupled with central composite design (CCD). The functionalized mixed matrix membrane containing NH2-MIL-125 (Ti) and 6FDA-durene, fabricated in our previous study, was used to perform the separation performance under three operational parameters, namely, feed pressure, temperature, and CO2 feed concentration, ranging from 3.5–12.5 bar, 30.0–50.0 °C and 15–70 mol%, respectively. The CO2 permeability and CO2/CH4 separation factor obtained from the experimental work were varied from 293.2–794.4 Barrer and 5.3–13.0, respectively. In addition, the optimum operational parameters were found at a feed pressure of 12.5 bar, a temperature of 34.7 °C, and a CO2 feed concentration of 70 mol%, which yielded the highest CO2 permeability of 609.3 Barrer and a CO2/CH4 separation factor of 11.6. The average errors between the experimental data and data predicted by the model for CO2 permeability and CO2/CH4 separation factor were 5.1% and 3.3%, respectively, confirming the validity of the proposed model. Overall, the findings of this work provide insights into the future utilization of NH2-MIL-125 (Ti)/6FDA-based mixed matrix membranes in real natural gas purification applications.

Potential of enhanced weathering of calcite in packed bubble columns with seawater for carbon dioxide removal

Enhanced weathering of minerals is one option being considered for removing CO2 from the atmosphere to help combat climate change. In this work, we consider the weathering of calcite with seawater in a reactor using air enriched with CO2. A mathematical model of the packed bubble column reactor was constructed with the key mass transfer and chemical reaction components validated with experimental data. The modelling results for a continuous process reveal the performance in terms of the specific energy consumption and the CO2 capture rate, which are affected by parameters including particle size, superficial velocities of gas and liquid, reactor bed height and feed CO2 concentration. The major energy requirements are for pumping liquid and compressing gas, and for CO2 enrichment; energy needed for supplying solid particles (mining operations, transport and comminution) was found to be comparatively minor. A trade-off was possible between ground area requirement (determined by CO2 capture rate) and energy requirement. To capture 1 tonne of CO2 at the reactor, optimal designs were predicted to consume 2.1–2.3 GJ of electricity and occupy 1.8–5.2 m2 year of space, depending on the feed CO2 concentration. These would increase to 5.7–8.2 GJ and 7.1–13.1 m2 year per tonne of CO2 captured, after allowing for degassing of the weathering product in the ocean. This increased energy intensity is still within the range of the CO2 removal options previously reported, while the space requirement quantification provides essential information for future feasibility assessment of this scheme.

Computational fluid dynamics simulation for dual‐phase membrane module for CO 2 capture: Effect of membrane thickness, temperature and CO 2 feed concentration

CO2 capture and natural gas purification are of paramount significance in power plant applications nowadays. Dual-phase membrane is an effective approach for the enhancement of CO2/CH4 separation efficiency. In this study, CO2/CH4 binary gas mixture separation was simulated by using hydroxide/ceramic dual-phase (HCDP) membranes incorporated in the industrial-scaled tubular membrane module. Computational fluid dynamics (CFD) was utilized as the approach to model the fluid flow within the membrane module. Utilizing the CFD modeling of membrane module, the effects of tubular membrane thickness, operating temperature and CO2 feed concentration on the separation performance of HCDP membrane had been investigated. The results showed that membrane thickness affected the effective surface area of the membrane and CO2 permeance. The greater the membrane thickness, the lower was the membrane separation efficiency. The highest CO2 recovery obtained was 90.12% at 1 mm tubular membrane thickness, with the membrane stage cut ratio of 0.1950. Operating temperature imposed a notable influence on the gas permeance as well. By increasing the operating temperature, CO2 permeances were improved and hence, the separation performance of HCDP membrane was enhanced simultaneously. As for the effect of CO2 feed concentration on the membrane performance, it was found that the overall membrane performance and separation efficiency were better when the CO2 feed concentration was low, due to the higher availability of the adsorption sites on the membrane surface. In conformity with the membrane technology as a cost-effective CO2 sequestration technique, the dual-phase membrane has demonstrated a remarkable potential to be adopted for industrial applications.

Effect of process parameters over carbon-based ZIF-62 nano-rooted membrane for environmental pollutants separation

The paper evaluates the routes towards the evaluation of membranes using ZIF-62 metal organic framework (MOF) nano-hybrid dots for environmental remediation. Optimization of interaction of operating parameters over the rooted membrane is challenging issue. Subsequently, the interaction of operating parameters including temperature, pressure and CO2 gas concentration over the resultant rooted membranes are evaluated and optimized using response surface methodology for environmental remediation. In addition, the stability and effect of hydrocarbons on the performance of the resulting membrane during the gas mixture separation are evaluated at optimum conditions to meet the industrial requirements. The characterization results verified the fabrication of the ZIF-62 MOF rooted composite membrane. The permeation results demonstrated that the CO2 permeability and CO2/CH4 selectivity of the composite membrane was increased from 15.8 to 84.8 Barrer and 12.2 to 35.3 upon integration of ZIF-62 nano-glass into cellulose acetate (CA) polymer. Subsequently, the optimum conditions have been found at a temperature of 30 °C, the pressure of 12.6 bar and CO2 feed concentration of 53.3 vol%. These optimum conditions revealed the highest CO2 permeability, CH4 permeability and CO2/CH4 separation factor of 47.9 Barrer, 0.2 Barrer and 26.8. The presence of hydrocarbons in gas mixture dropped the CO2 permeability of 56.5% and separation factor of 46.4% during 206 h of testing. The separation performance of the composite membrane remained stable without the presence of hydrocarbons for 206 h.

Fabrication of multilayer composite hollow fiber membrane comprising NH2-MIL-125 (Ti) for CO2 removal from CH4

The presence of CO2 has created significant challenges in natural gas processing in order to meet consumer’s specifications and pipeline transportation. Membrane separation is among the most effective approaches in CO2 separation from natural gas mainly to its energy efficiency. This study investigates the alternate technique for enhancing the performance of hollow fiber membrane in CO2 removal from CH4. A new type of composite hollow fiber membrane is fabricated by dip-coating of polymer solution comprising various loadings of NH2-MIL-125 (Ti) in PEBAX onto PDMS coated-polysulfone (PSf) hollow fiber. The morphology and elemental mapping analysis of the resultant membranes were characterized via scanning electron microscope (SEM) and energy dispersive X-ray (EDX), respectively. SEM images showed that no major voids or clusters were observed between the two phases of polymer and filler. Improved CO2 and CH4 gas permeance were found for composite membranes, as compared to PSf membrane coated only by PDMS and PEBAX solutions. Besides, highest improvement of CO2/CH4 ideal selectivity was obtained for composite membrane loaded with 10 wt% of filler. High porosity and high CO2 affinity of NH2-MIL- 125 (Ti) are the main reasons for the enhancement of CO2 removal from CH4. Hence, further research work is necessary to explore the performance of this membrane at various operating conditions such as temperature, flow rate, and CO2 feed concentration.