Highly Selective and Hydrocarbon-Resistant Polyimide Hollow Fiber Membranes for Helium Recovery from Natural Gas

Abstract

The recovery of helium from natural gas using membranes has attracted substantial attention, while very limited polymers were spun into hollow fibers and evaluated for realistic helium recovery. This work demonstrates the successful preparation of asymmetric and highly helium-selective hollow fiber membranes for the enrichment of helium from natural gas. A novel, aromatic copolyimide was designed and fabricated into hollow fiber membranes (HFMs) via the dry-jet/wet-quench spinning approach. The as-prepared HFMs display a He permeance of 85 GPU and high He-related gas selectivities of 140, 204, 448, and 609 for He/N2, He/CH4, He/C2H6, and He/C3H8 gas pairs, respectively. Particularly, ternary and quaternary mixed-gas permeation results reveal excellent light and heavy hydrocarbon resistance due to the competition between plasticization and gas sorption. The HFMs also demonstrated superior low-temperature gas separation performance and outstanding membrane gas separation stability, rendering them attractive for helium recovery.

Precise Helium Sieving from Hydrogen Using Fluorine‐Decorated Carbon Hollow Fiber Membranes

“…We employ scalable polyimide hollow fibers, specifically 6FDA 0.9 -ODPA 0.1 -mPDA (as shown in Figure S1, Supporting Information), which has a skin layer thickness of approximately 360 nm and a He permeance of 85 gas permeation units (GPUs, 1 GPU = 3.348×10 À 10 mol m À 2 s À 1 Pa À 1 ) at 35 °C. These hollow fibers were previously fabricated in-house (SI) and thoroughly characterized before serving as the precursor materials for the CMS membranes, which we referred to as HFM-P. [21] The CMS membranes were created through the pyrolysis of the asymmetric polyimide hollow fibers at various temperatures under controlled conditions (SI), allowing us to regulate the rigidity of aromatic/carbon strands and atomic composition. [22] The deconvoluted C1s X-ray photoelectron spectroscopy (XPS, Figure S2) and Raman spectra (Figure S3) confirm that the sp 2 /sp 3 ratio increases with increasing pyrolysis temperature within the range of 250-800 °C.…”

Copolyimide asymmetric hollow fiber membranes for high‐pressure natural gas purification

“…Additionally, most of the membranes reported in literature are characterized and tested using simple dense‐film geometry (i.e., planar geometry). For large‐scale industrial membrane‐based application of gas separation, in particular, asymmetric or composite hollow fiber (i.e., tubular geometry) is often preferred, owing to its high packing density, resistance to high transmembrane pressures, and the ability to create ultra‐thin selective layers 24–29 . While synthesizing fibers with minimal defects is a challenging task, it is important to assess gas separation membrane performance under industrially relevant conditions to support commercialization efforts 30–34 …”

“…For large-scale industrial membrane-based application of gas separation, in particular, asymmetric or composite hollow fiber (i.e., tubular geometry) is often preferred, owing to its high packing density, resistance to high transmembrane pressures, and the ability to create ultra-thin selective layers. [24][25][26][27][28][29] While synthesizing fibers with minimal defects is a challenging task, it is important to assess gas separation membrane performance under industrially relevant conditions to support commercialization efforts. [30][31][32][33][34] Herein, we report the pure-and sweet mixed-gas permeation properties of block copolyimide 6FDA-Durene/6FDA-CARDO (5000:5000) fabricated in an integrally skinned asymmetric hollow fiber membrane.…”

Process Design and Techno-Economic Analysis of Membrane-Mediated Helium Recovery from Low-Grade Natural Gas

“…Helium has been playing an irreplaceable role in various applications, including cryogenic superconductors, shielding gas, welding, electronic and optical fiber manufacturing, etc., because of its unique physicochemical characteristics such as high ionization energy, lightweight, and low boiling temperature. − Currently, almost all industrial He is produced from either natural gas (NG) reservoirs or nitrogen removal units in liquefied NG plants using the cryogenic technique, in which crude He (60–90%) is obtained first from liquefied NG and high-purity He (99.995%) is obtained by further purification through pressure swing adsorption or cryogenic distillation in different stages . In view of the whole He separation process, enrichment of the crude He (60–90%) from the low-concentration natural gas plays a critical role.…”