Membranes Targeting Industrial O2 Production from Air – A Short Review

Abstract: Some of the most promising membranes for O2/N2 gas separation (air separation) mentioned in literature so far are selected, in terms of meeting a O2-gas-production breakeven cost that is lower than that of competing air separation unit (ASU) technologies, based on latest reported technoeconomic studies. An overview regarding most important applications of O2 and N2 gases is first given, in respect with the demanded purity limits for each case, since the purity parameter is crucial in defining the minimum breakeven cost. Keywords: oxygen production; air separation technologies; membrane technology; industrial O2 production processes

Hydrogen technologies and policies for sustainable future: a review

Hydrogen has recently attracted considerable attention as a promising alternative for addressing energy and environmental issues. Hydrogen is a flexible and clean energy carrier that can be used in various industries, including transportation, manufacturing, and power generation, without emitting harmful emissions. This study provides a detailed review of hydrogen technologies and policies in the context of a hydrogen economy. Hydrogen production is examined with its cost analysis and current technological challenges, in addition to the key aspects of hydrogen storage, transportation and applications. This review also provides a critical discussion of global policies and roadmaps that have been proposed or implemented to achieve a hydrogen-based future economy. These policies include funding for R&D, financial incentives, tax credits, and frameworks. Finally, two key areas that can be exploited to expedite global hydrogen adoption are proposed. First, technological challenges can be addressed by employing an integrated system approach to produce hydrogen for various applications, along with vigorous investment in research on material development in handling/storing hydrogen. Second, policies to accelerate hydrogen adoption should focus on public–private partnerships, media awareness campaigns, and the introduction of green credit scores

CO₂/CH₄ and CO₂/CO Selective Pebax-1657 Based Composite Hollow Fiber Membranes Prepared by a Novel Dip-Coating Technique

A novel and innovative method was developed to fabricate defect-free composite hollow fiber (HF) membranes using drop-casting under continuous flow. The synthesized Pebax-1657—based membranes were examined for gas separation processes, focusing on the separation of CO2 from CH4 and CO gases. The separation performance of the membranes was rigorously assessed under realistic binary gas mixture conditions to evaluate their selectivity and performance. The effect of pressure on separation performance was systematically investigated, with transmembrane pressures up to 10 bar being applied at a temperature of 298 K. Remarkable CO2/CH4 selectivities of up to 110 and CO2/CO selectivities of up to 48 were achieved, demonstrating the robustness and effectiveness of these composite HF membranes, suggesting their suitability for high-performance gas separation processes under varying operational conditions. Overall, this study introduces a novel approach for scaling up the fabrication of HF membranes and provides valuable insights into their application in CO2 separation technologies, offering the potential for advancements in areas such as natural gas processing and carbon capture from CO-containing streams

Green chemistry-based fabrication of hollow fiber and flat sheet polyimide membranes for CO2/CH4 separation

In this work, the successful fabrication of polymeric hollow fiber (HF) and flat sheet (FS) membranes was examined by employing γ-butyrolactone (GBL)-a green and environmentally friendly solvent- for the polymer's dissolution following the principles of green chemistry and sustainability regarding the membrane preparation. In addition, the ternary phase diagram of the P84/GBL/water was constructed and the viscosity of dope solution was measured for different concentrations and temperatures. Their morphological characteristics of the prepared polyimide membranes were investigated through SEM analysis. CO2/CH4 separation measurements under continuous flow were performed to evaluate the efficiency of the membranes for a binary 10/90 vol.% CO2/CH4 gas mixture. The developed green HF and FS membranes exhibited comparable, and in some cases even superior, performance compared to membranes prepared using the conventional and highly toxic NMP solvent, making them highly promising candidates for CO2/CH4 separation, with a real mixture separation factor of ∼58

The Optimization of Dispersion and Application Techniques for Nanocarbon-Doped Mixed Matrix Gas Separation Membranes

In this work, supported cellulose acetate (CA) mixed matrix membranes (MMMs) were prepared and studied concerning their gas separation behaviors. The dispersion of carbon nanotube fillers were studied as a factor of polymer and filler concentrations using the mixing methods of the rotor–stator system (RS) and the three-roll-mill system (TRM). Compared to the dispersion quality achieved by RS, samples prepared using the TRM seem to have slightly bigger, but fewer and more homogenously distributed, agglomerates. The green γ-butyrolactone (GBL) was chosen as a polyimide (PI) polymer-solvent, whereas diacetone alcohol (DAA) was used for preparing the CA solutions. The coating of the thin CA separation layer was applied using a spin coater. For coating on the PP carriers, a short parameter study was conducted regarding the plasma treatment to affect the wettability, the coating speed, and the volume of dispersion that was applied to the carrier. As predicted by the parameter study, the amount of dispersion that remained on the carriers decreased with an increasing rotational speed during the spin coating process. The dry separation layer thickness was varied between about 1.4 and 4.7 μm. Electrically conductive additives in a non-conductive matrix showed a steeply increasing electrical conductivity after passing the so-called percolation threshold. This was used to evaluate the agglomeration behavior in suspension and in the applied layer. Gas permeation tests were performed using a constant volume apparatus at feed pressures of 5, 10, and 15 bar. The highest calculated CO2/N2 selectivity (ideal), 21, was achieved for the CA membrane and corresponded to a CO2 permeability of 49.6 Barrer.</jats:p