Highly Compatible Hydroxyl-Functionalized Microporous Polyimide-ZIF-8 Mixed Matrix Membranes for Energy Efficient Propylene/Propane Separation

Abstract

Mixed-matrix membranes composed of mechanically strong, solution-processable polymers and highly selective ultramicroporous fillers (pore size < 7 Å) are superior candidate membrane materials for a variety of energy-intensive gas separation applications because of their structural tunability to achieve enhanced gas permeability and gas-pair selectivity. However, their industrial implementation has been severely hindered because inefficient compatibility of the polymer matrices and crystalline fillers results in poorly performing membranes with low filler capacity and interfacial defects. Herein, we report for the first time a unique strategy to fabricate highly propylene/propane selective mixed-matrix membranes (MMMs) composed of a hydroxyl-functionalized microporous polyimide (PIM-6FDA-OH) and an ultramicroporous, strongly size-sieving zeolitic imidazolate framework (ZIF-8). Excellent compatibility between PIM-6FDA-OH and ZIF-8 with selective filler loading up to 65 wt% resulted from N…O-H induced hydrogen bonding as evidenced by Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The newly developed MMMs demonstrated unprecedented mixed-gas performance for C 3 H 6 /C 3 H 8 separation and outstanding plasticization resistance of up to at least 7 bar feed pressure. The reported fabrication concept is expected to be applicable to a wide variety of OH functionalized polymers and alternative tailor-made imidazolate framework materials designed for MMMs to achieve optimal gas separation performance.

Modeling Permeation through Mixed-Matrix Membranes: A Review

“…Table 2), corresponding to the low-density limit of non-interacting dispersed spheres, have remain popular as reference in practical applications. However, this model has also been commonly shown to under-predict experimental MMM permeation data [45,51,81,145]. For concentrated composites, a number of analytical expressions have been proposed, including those corresponding to the Chiew-Glandt, Lewis-Nielsen, Higuchi (cf.…”

“…While these simulation studies considered Finally, while RMA is much less popular for describing permeation in MMMs. With the introduction of nano-flake [181][182][183] and nanotube [184][185][186] based MMMs, models such as those of Cussler [51] and KJN [48] have become more popular as reference to compare with experimental [76,114,187] or simulation-based permeation data [171,172]. Amongst these works, Wang et al [171,172] performed simulations of 3D MMMs comprising ideal platelet and tubular particles, and compared simulation predictions to the Cussler and KJN models (cf.…”

“…Furthermore, we compare predictions of popular permeation models against available experimental and simulation-based permeation data, and discuss the suitability of these models for predicting MMM permeability under typical operating conditions. Thus, much effort has been devoted to the optimization of MMMs synthesis [34,42,[45][46][47][48]; with a number of works even reporting fabrication of defect-free MMMs [37,[49][50][51].Ideally, a mixed-matrix membrane (MMM) consists of a selective inorganic filler phase embedded to continuous polymer matrix [21,35]. In this way, an MMM combines high intrinsic permeability and separation efficiency of advanced molecular sieving materials (e.g., zeolites, carbons, metal-organic frameworks) or nanoscale materials (e.g., carbon nanosheets or nanotubes) with robust processing capabilities and mechanical properties of glassy polymers [23,52].…”

“…Furthermore, we compare predictions of popular permeation models against available experimental and simulation-based permeation data, and discuss the suitability of these models for predicting MMM permeability under typical operating conditions. Thus, much effort has been devoted to the optimization of MMMs synthesis [34,42,[45][46][47][48]; with a number of works even reporting fabrication of defect-free MMMs [37,[49][50][51].…”

Propylene - propane separation using Zeolitic-Imidazolate Framework (ZIF-8) membranes: Process techno-commercial evaluation

“…ZIF-8) / polymeric membrane incompatibility is the major limitation that hinders the industrial implementation of Mixed Matrix Membranes (MMMs). In a recent work [56], excellent compatibility was observed between the ZIF-8 filler and the 6FDA polymeric matrix, when the latter is being functionalized with hydroxyl groups; loading capacities as high as 65% were recorded [56].…”