Synthesis of ZIF-8 tubular membrane via solvent evaporation seeding coupled with microwave assisted heating method for separation of small molecule gases.

In this work, we systematically study the performance of tubular ZIF-8 membranes in the separation of small molecules including H2, CO2, N2 and CH4. The tubular ZIF-8 membranes were synthesized on α-alumina support via novel dual approach known as solvent evaporation seeding coupled with microwave assisted growth. The durations for the growth of the seed layer through solvent evaporation and membrane layer via microwave heating were varied. The crystallinity and morphology of the resultant membranes were evaluated by using XRD, SEM and IFM analyses. The performance of the resultant tubular ZIF-8 membranes was assessed for small molecule gases permeation at various pressures and temperatures. Highest flux ranging from 0.02 to 0.61 mol/m2s were obtained for gases CO2, CH4, N2, and H2 at feed pressure of 10 bar, whereas highest ideal selectivity of 12.4, 9.3 and 6.9 were obtained for H2/CH4, CO2/CH4, N2/CH4, respectively, at feed pressure of 10 bar and temperature of 30 °C. This work reveals that the tubular ZIF-8 membrane can be synthesized via a feasible and reproducible solvent evaporation seeding coupled with microwave assisted growth method, which can be further explored for the upscaling of the ZIF-8 tubular membrane in pilot scale for gas separation application.

Enrichment of biogas through composite membrane of PEBA-1657/ hierarchical T-type zeolite.

Presently, composite membranes emerged as a promising approach to overcome the limitations of polymeric and inorganic membranes particularly in acid gas separation. In the present work, composites membranes were fabricated by combining hierarchical T-Type (h-zeolite T) zeolite and PEBA-1657 at different filler composition that ranging from 5 wt% - 30 wt% for the CO2/CH4 separation. The physicochemical properties of the resultant inorganic filler and membranes were investigated by using Brunauer-Emmett- Teller (BET), field emission scanning electron microscopy (FESEM), Fourier Transform infra-red (FTIR), x-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). FESEM and EDX analysis revealed that the formation of voids and agglomeration of particles is pronounced as the fillers loading was increased up to 30 wt%. The single gas permeation test demonstrated that amalgamation of h-zeolite T particles into PEBA-1657 has resulted in the improvement of CO2 permeability up to 122% and CO2/CH4 selectivity up to 31%. Hybrid membrane encapsulated with 25 wt% of h-zeolite T displayed a maximum separation efficiency with the highest CO2 permeability of 164.83 Barrer and CO2/CH4 selectivity of 19.37. However, further increment of fillers composition up to 30 wt% resulted in a sharp reduction of CO2/CH4 selectivity to 15.80 due to the particles sedimentation and agglomeration. Overall, the favorable gas transport behavior of PEBA-1657/h-zeolite T composite membrane indicates its promising prospect for CO2/CH4 separation especially in biogas and natural gas purification application. Future research efforts are directed on the optimization of the fabrication parameters and performance investigation at different operating condition to further enhance the CO2 separation and extend its operability under various environment.

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.

Development of Amine-Functionalized Metal-Organic Frameworks Hollow Fiber Mixed Matrix Membranes for CO2 and CH4 Separation: A Review.

CO2 separation from raw natural gas can be achieved through the use of the promising membrane-based technology. Polymeric membranes are a known method for separating CO2 but suffer from trade-offs between its permeability and selectivity. Therefore, through the use of mixed matrix membranes (MMMs) which utilizes inorganic or hybrid fillers such as metal-organic frameworks (MOFs) in polymeric matrix, the permeability and selectivity trade-off can be overcome and possibly surpass the Robeson Upper Bounds. In this study, various types of MOFs are explored in terms of its structure and properties such as thermal and chemical stability. Next, the use of amine and non-amine functionalized MOFs in MMMs development are compared in order to investigate the effects of amine functionalization on the membrane gas separation performance for flat sheet and hollow fiber configurations as reported in the literature. Moreover, the gas transport properties and various challenges faced by hollow fiber mixed matrix membranes (HFMMMs) are discussed. In addition, the utilization of amine functionalization MOF for mitigating the challenges faced is included. Finally, the future directions of amine-functionalized MOF HFMMMs are discussed for the fields of CO2 separation.

Tailoring CO2/CH4 Separation Performance of Mixed Matrix Membranes by Using ZIF-8 Particles Functionalized with Different Amine Groups.

CO2 separation from CH4 by using mixed matrix membranes has received great attention due to its higher separation performance compared to neat polymeric membrane. However, Robeson's trade-off between permeability and selectivity still remains a major challenge for mixed matrix membrane in CO2/CH4 separation. In this work, we report the preparation, characterization and CO2/CH4 gas separation properties of mixed matrix membranes containing 6FDA-durene polyimide and ZIF-8 particles functionalized with different types of amine groups. The purpose of introducing amino-functional groups into the filler is to improve the interaction between the filler and polymer, thus enhancing the CO2 /CH4 separation properties. ZIF-8 were functionalized with three differents amino-functional group including 3-(Trimethoxysilyl)propylamine (APTMS), N-[3-(Dimethoxymethylsilyl)propyl ethylenediamine (AAPTMS) and N1-(3-Trimethoxysilylpropyl) diethylenetriamine (AEPTMS). The structural and morphology properties of the resultant membranes were characterized by using different analytical tools. Subsequently, the permeability of CO2 and CH4 gases over the resultant membranes were measured. The results showed that the membrane containing 0.5 wt% AAPTMS-functionalized ZIF-8 in 6FDA- durene polymer matrix displayed highest CO2 permeability of 825 Barrer and CO2/CH4 ideal selectivity of 26.2, which successfully lies on Robeson upper bound limit.