Iranian Journal of Chemical Engineering (IJChE)

Abstract Ability and compatibility of the membrane processes for gas separation are evaluated by their membranes’ permeability and selectivity where both have been tried to enhance in promising membrane generation of mixed matrix membranes (MMMs). In the current study, two- and three-dimensional models were constructed for MMMs, and the Fick's first law was solved numerically in them by using the Finite Element Method (FEM) and Computational Fluid Dynamic (CFD) tools. The effects of different MMMs structural parameters such as the volume fraction, size and mode of packing, i.e., regular or random, of the filler particles were investigated on the effective permeability of the pure gaseous penetrants through the MMMs. Furthermore, the interfacial equilibrium constant of the penetrants and their diffusivity ratios were also evaluated in view point of their impacts on the MMMs’ separation performance. Some well-known established models including Maxwell, Bruggeman, Lewis - Nielsen, Pal, and Chiew - Glandt were applied in the modeling. Deviation of the simulation results from the experimentally measured ones were low enough, however, at higher loadings of the filler particles the simulation deviation became greater. Simulated results through PSF - MCM-41 MMMs were compared with those of experimentally measured ones and AAREs of 31.0 (The lowest deviation), 42.7, and 41.0 % obtained for CO2, O2, and N2, respectively.

Abstract The Mixed Matrix Membrane (MMM) concept consists of incorporating suitable polymers with inorganic or organic fillers. The majority of polymeric membranes maintain a trade-off between permeation and selectivity, which restricts their development in separation applications. In this paper, less reviewed challenges on development of MMMs, such as the preparation of mix-matrix resistant membranes for industrial gas separation applications, as well as the use of appropriate and compatible fillers for different types of polymers were discussed. The MMMs comprising Metal Organic Framework (MOF) fillers were extensively studied. The importance of MOFs includes finely tunable structures, excellent compatibility with polymer matrices, and molecular sieve action. MMMs are considered promising structures that combines the advantages of polymeric and inorganic membranes. They exhibit the potential to upgrade the separation performance of pure polymer membranes using filler materials, whereas the cost remains relatively lower than that of pure inorganic membranes. The development of novel filler materials makes a substantial contribution in terms of role-playing.

Abstract The polysulfone mixed matrix membranes (MMM) with different concentrations of graphene oxide (0, 0.25, 0.5 wt % of the polymer) are fabricated by a phase separation method. The cross-sectional structures and their upper surface were assessed by the (SEM) surface roughness of the membranes assessed by (AFM). The mechanical and thermal stability of the fabricated membranes were evaluated as well. The separation of Carbon dioxide, nitrogen and methane from natural gas was considered. Also, by increasing the concentration of graphene oxide in the polymer matrix, the thickness of the spongy structure increases and the holes of the finger-like membranes are also destroyed. From the cross-sectional images of the outer surface of the MMM, it was concluded that an active selector layer was created on the lower surface of the membrane. The membrane tensile strength and the length of the membrane at fracture point increased slightly with an increase in the concentration of graphene oxide. Transition Glass temperature of the membrane increased by the addition of graphene oxide to the structure. From TGA analysis, in the presence of graphene oxide, the thermal stability improved. From the gas permeation test, by the addition of 0.25 % of graphene oxide to the polymer, CO₂ permeability was increased from 61.22 GPU to 76.04 GPU, while the addition of 0.5 wt % resulted in a lower permeability (69.55 GPU). The Nitrogen gas permeation flux of membranes decreased from 10.93 GPU to 3.91 GPU by the addition of 0.50 wt % of graphene oxide. The Methane gas permeation flux is reduced from 11.31 GPU to 6.95 GPU and 4.92 GPU by the addition of 0.25 % and 0.50 % of graphene oxide respectively. In conclusion, an increase in the concentration of graphene oxide increased the carbon dioxide selectivity.

Abstract A new method is developed to enhance the gas separation properties of mixed matrix membranes (MMMs) by interior modification of an inorganic nano-porous particle. Ship-in-a-bottle (SIB), as a novel synthesis strategy, is considered to encapsulate a polyaza macrocyclic Ag-ligand complex into the zeolite Y, which is resulted in a new host-guest nano-composite. It is consequently incorporated into a glassy polymer matrix to fabricate a novel MMM for CO2 separation. Accordingly, cellulose acetate (CA) with relatively low gas permeability is selected as the membrane polymeric matrix to provide an appropriate opportunity for better tracking the effect of incorporating the new synthesized nano-porous hybrids. The results showed a promising increase in both the CO2 permeability (45.71%) and CO2/N2 selectivity (40.28%) of the prepared MMM over its pristine CA membrane. It can be concluded that the proposed method makes it possible to fabricate novel MMMs with significant intensification in performance of the current MMMs.

Abstract TiO2 nanoparticles were pretreated with ethelendiamine (EDA) to synthesize amine-functionalized TiO2. The mixed matrix membranes (MMM) comprised of amin-functionalized TiO2 inside polysulfone (PSf) matrix were fabricated and characterized for gas separation. The effects of the amin-functionalized TiO2 loading on the gas permeation properties of the MMM were investigated by varying the amin-functionalized TiO2 loading in the PSf matrix from 0ñ10 wt%. The fabricated amin-functionalized TiO2/PSf MMM were characterized by scanning electron microscopy (SEM), Fourier Transform Infrared spectroscopy (FT/IR) and pure gas permeation test. Gas permeation measurement showed that MMMs embedded with different amount of amin-functionalized TiO2 exhibited different separation performances. For example, in MMMs containing 10 wt% amin-functionalized TiO2, the permeability of N2, CH4, CO2 and O2 increased up to 0.69, 0.8, 3.5 and 1.1 GPU respectively. Due to the higher interaction of amine groups on F-nano TiO2 with polar gases, amin-functionalized TiO2 possessed better performances in terms of permeability and selectivity in comparison to pure TiO2. The results revealed that the functionalization of TiO2 has improved the gas permeability of prepared membranes.

Abstract Analytical gas-permeation models for predicting the separation process across  membranes (exit compositions and area requirement) constitutes an important and necessary step in understanding the overall performance of  membrane modules. But, the exact (numerical) solution methods suffer from the complexity of the solution. Therefore, solutions of nonlinear ordinary differential equations that govern the performance of the membrane modules for gas separations by approximate and asymptotic methods are useful in the design and comparison of processes. In this work, the asymptotic methods were applied for predicting the performance of nanometric tubular ceramic membranes in the separation of binary gas mixtures with cocurrent and countercurrent flow patterns. Also, the exact (numerical) solutions of the governing equations using the fourth order Rung-Kutta technique were proposed. The comparison of the results showed a good agreement between the exact solution and asymptotic analysis methods over the whole range of selectivities (). Because, the asymptotic curves into the former () and latter () boundaries had a suitable overlap with each other to cover the whole range of selectivities. The accuracy of this method was verified by a comparison of the predicted results with different literature experimental data and mathematical models. This result suggests the use of the asymptotic analysis method to provide excellent shortcut, preliminary design information.