Natural gas purification and olefin/paraffin separation using cross-linkable 6FDA-Durene/DABA co-polyimides grafted with α, β, and γ-cyclodextrin

Natural gas purification and olefin/paraffin separation using cross-linkable dual-layer hollow fiber membranes comprising β-Cyclodextrin

“…The main objective is to develop a novel approach that encompasses the synergistic advantages of the cross-linking and the membrane fabrication process for high performance gas separation applications. Indeed, this work can be regarded as an extension to our earlier studies [36][37] that reported the development of high performance dense flat sheet membranes. Attempts were made in this study to unravel the underlying mechanisms and engineering to scale up the flat dense membranes to dual-layer hollow fiber membranes with desirable features.…”

In situ regulation of micro-pore to design high performance polyimide membranes for pervaporation dehydration of isopropanol

“…Moreover, the intensity of characteristic peak of 1580-1600 cm À 1 (aromatic ring's C-C stretching vibrations) slightly increases when the membranes are thermally annealed at 400°C. This may be explained according to TGA-FTIR results that after decarboxylation the two radical DABA groups could form linkages as biphenyl [36,44,45]. These linkages are drawn as connecting lines between polymer chains in the evolutionary scheme of Fig.…”

“…Then, a stoichiometric amount of 6FDA was gradually added to the solution to obtain a total of 20 wt% solid in the solution. The purpose of adding 6FDA gradually is to prevent the reaction between water and 6FDA [36]. After 24 h polymerization reaction, a viscous polyamic acid with a high molecular weight was formed.…”

“…The as-casted membranes were first pretreated at 120°C to partially remove the moisture and solvents. Then, the membranes were heated from room temperature to 400°C near the decarboxylation temperature [36,44] and held there for 30 min followed by another increase to 800°C. Four distinguished regions of weight loss can be detected for the two membranes.…”

“…Therefore, first we synthesized the 6FDA-based polyimide comprising 4,4′-(hexafluoroisopropylidene) diphthalicanhydride (6FDA) and two types of diamine, 2,3,5,6-tetramethyl-1,4-phenylenediamine (Durene) and 3,5-diaminobenzoic acid (DABA) and optimized the membrane performance based on monomers selection [36]. This composition was chosen because high diffusion coefficients would be expected due to (1) the fluorine groups in 6FDA and (2) the branchy spatial structure of Durene.…”