This study investigates the use of ultra-microporous carbon hollow fibre membranes for the H-2 upgrading from syngas. The hollow fibres were spun from a P84 polyimide dope using the green solvent gamma-butyrolactone, thereby avoiding conventional dipolar aprotic solvents (e.g., NMP/DMF). Together with a simple water-based post-treatment and N-2 carbonisation, this approach reduces solvent hazards compared to traditional routes while yielding ultra-microporous, as confirmed by Sips isotherm fitting, carbon HFs with high selectivity. Their separation performance was examined through mixed-gas permeation experiments using binary (H-2/CO2, H-2/CO) and ternary (H-2/CO2/CO) gas mixtures over a range of feed compositions and temperatures. H-2 exhibited the highest permeance, increasing with its feed molar fraction, while CO2 and CO displayed progressively lower permeance due to competitive sorption and kinetic restrictions. For ternary gas mixtures feed, the membranes enriched H-2 from similar to 30 % to 57 % in the permeate, while reducing CO by 86 M%, demonstrating strong selectivity also in mixed gas conditions. Permeation data were incorporated into process simulations to investigate membrane configurations for H-2 upgrading from syngas. A two-stage configuration achieved up to 90 M% H-2 purity at 86 % recovery. Overall, the combination of green fabrication, tailored microporosity and promising process-level performance positions these carbon hollow fibre membranes as attractive candidates for H-2 purification, post-combustion CO2 capture and broader membrane-based gas separation applications.

Dimethyl ether (DME) is a clean and efficient alternative fuel and chemical intermediate, typically produced by methanol dehydration over solid acid catalysts. In this study, the catalytic performance of a gamma-Al2O3 membrane operated in a through-flow configuration was evaluated for DME production. The membrane exhibited high methanol conversion and complete DME selectivity (100 %) over the 260-300 degrees C temperature range, showing optimal performance at 280 degrees C and low WHSV (0.4 h- 1), where equilibrium conditions are approached. Comparative tests with gamma-Al2O3 pellets demonstrated the membrane superior selectivity and enhanced stability with the time-on-stream. A 30-hour time-on-stream experiment showed a good resistance of membrane to deactivation, with catalytic activity fully restored through a thermal regeneration step. The gamma-Al2O3 membrane was further benchmarked against literature-reported ZSM-5 and BEA zeolite membranes, showing better performance in the explored operating conditions.

To overcome water-induced deactivation in methanol-to-dimethyl ether (DME) conversion, bilayer ZSM-5 zeolite membranes were designed and prepared to improve the catalytic activity and water management. A siliceous high-Si/Al top layer and an aluminous low-Si/Al bottom layer were sequentially grown on a support, achieving a seamlessly intergrown ZSM-5 bilayer with no observable interfacial boundary. This architecture localizes active acid sites in the lower (high-Al) catalytic zone while a hydrophobic upper layer repels water and facilitates its removal. In methanol-to-DME catalytic membrane reactors, the bilayer membranes outperformed single-layer counterparts in water management and stability. The optimal bilayer (high-Si/Al top over low-Si/Al bottom) maintained a stable methanol conversion after 300 h on stream, whereas a conventional single-layer ZSM-5 membrane lost more than 80% of its activity in the same period. A reverse bilayer (low-Si/Al top over high-Si/Al bottom) exhibited higher initial conversion but suffered a similar to 32% decline by 300 h, underscoring the importance of layer ordering. These results demonstrate that spatially distributing acidity and hydrophobicity within a zeolite membrane markedly improves water management and catalyst longevity. The bilayer design offers a promising strategy to extend the lifetime of catalytic membrane reactors for DME synthesis.

The EU HydroMine project investigates waste valorisation, carbon capture, and the reuse of legacy mine infrastructure to produce hydrogen (targeting 90–99.99% purity) from refuse-derived fuel (RDF). RDF is non-recyclable municipal waste in the sense of circular economy, but currently applied in, i.e., thermal recycling in cement plants or deposited on landfills. Hence, reduction of overall RDF volumes is central to address the main challenges of urban waste management and decarbonisation of energy systems. In this course, HydroMine supports circular economy developments in mining regions in transition and advances sustainable hydrogen production strategies by repurposing existing mining infrastructure for RDF beneficiation. Techno-economic modelling was carried out in the project to quantify the economics of this technology by means of a dedicated, dynamic and modular simulation framework. It employs surrogate models using response functions and tables as well as empirical data correlations developed within the project, and was validated for regional operational scenarios at a Polish study area. For that purpose, the complete process chain from RDF pre-processing through gasification for synthesis gas production and cleaning, hydrogen as well as carbon monoxide and dioxide separation by membrane systems [1] and pressure-swing adsorption (PSA) is taken into account. Further unit stages comprise treatment of tail gases by plasma technologies and final product gas compression. All simulations integrate mass and energy balances with cost calculations at unit scale. Sensitivity analyses were embedded into the workflow to establish a comprehensive assessment of influential parameters. The established models are supporting the project in developing commercially viable waste-to-hydrogen strategies for stakeholders, investors, policymakers, and operators to accelerate the adoption of sustainable hydrogen production in the decarbonising energy transition landscape. [1] Avruscio, E., Marsico, L., Brunetti, A., Theodorakopoulos, G. V., Karousos, D. S., Kempka, T., ... & Barbieri, G. (2026). Syngas hydrogen upgrading using green-based ultra-microporous carbon hollow fibre membranes. International Journal of Hydrogen Energy, 198, 152598. https://doi.org/10.1016/j.ijhydene.2025.152598. The present study has received funding from the EU RFCS - 2022, under grant agreement No. 101112629 (HydroMine).

This work presents the design of a membrane-integrated process for biogas valorisation and renewable hydrogen storage via CO2-to-methanol conversion. The process maximizes CO2 utilisation by incorporating H-2 from renewable sources, while simultaneously separating methane from biogas to produce a stream suitable for direct injection into the natural gas grid. Membrane units are integrated upstream and downstream of the methanol synthesis reactor: upstream membranes allow to obtain a CO2-rich stream for methanol production and a CH4-rich stream compliant with grid specifications, while downstream membranes recover unreacted CO2 and H-2 for recycling, minimizing emissions and hydrogen losses. The system is analysed in a step/stage configuration using performance maps from a validated one-dimensional model, accounting for the selectivity and permeance of a polyimide membrane. Results show that biogas can be fully valorised, achieving 98.5% CH4 recovery with molar purity >= 97.5% and similar to 97% CO2 conversion to methanol, with nearly complete utilisation of renewable hydrogen. This membrane-integrated approach provides an effective strategy for coupling biogas upgrading with renewable hydrogen storage, enabling sustainable energy storage in the form of methanol e-fuels and contributing to carbon-neutral energy pathways.

The present review aims to underline the inherent gas separation potential of pristine Pebax-1657, without any chemical modification, nor addition of filler material, by referring to a number of selected outstanding literature results. These results underscore the adequacy of pristine Pebax-1657 membranes in achieving excellent CO2 gas separation performances, within or close to the target area of commercial applicability in terms of technoeconomic competitiveness when compared to alternative CO2 separation/capture technologies. These achievements are facilitated by the utilization and combination of cutting-edge membrane preparation techniques. Additionally, the current review provides detailed information regarding material and gas separation properties based on experimental data, which are handpicked from literature and statistically presented to highlight significant differences in reported values. Basic empirical correlations emerging from these data are formulated, in order to provide a guideline for future membrane design, along with clarifications on important claims and points that are often encountered in relevant literature.

In this work, we focused on a membrane gas separation system aimed at enhancing the efficiency of a process for CO2 valorisation into synthetic methane production via hydrogenation of a biogas stream. This system is designed for separating and recycling unreacted CO2 and H2 downstream of a methanation reactor. The inlet stream of the membrane separation system consists of unconverted CO2 and H2, apart from the CH4 from biogas and that produced by CO2 conversion. The membrane separation is analysed by using performance maps based a 1D mathematical model, already developed and validated, considering the selectivity and permeance properties of a polyimide membrane. The outcomes of the membrane system, constituted by two steps operated at 20 bar, show that the proposed integrated process allows a quantitative CO2 conversion into methane. The integration of the multi-step membrane process leads to a final retentate stream suitable for direct injection into the gas grid with CH4 >= 97.5 % molar, and CO2 and H2 within the targets of Italian regulation, CH4 yields up to 0.987 confirmed a nearly complete CO2 valorisation into CH4 and a near-zero emissions process.

In this study, a Pd-Ag membrane reactor (MR) integrated with a lab-synthesized ruthenium catalyst supported on La2Ce2O7 was used for the efficient production and recovery of highly-pure hydrogen from ammonia decomposition. The catalyst was synthesized using solution combustion techniques, and its structure-activity relationship was thoroughly investigated through a range of advanced characterization methods, including N2 physisorption, X-ray diffraction (XRD), hydrogen temperature-programmed reduction (H2-TPR), and transmission electron microscopy (TEM). The performance of the membrane reactor was evaluated by varying the feed pressure and flow rate, using either single ammonia or a simulated outlet stream from a conventional reactor with ammonia conversions ranging from 20 % to 50 %. This configuration was designed to assess the MR ability to mitigate or prevent hydrogen back-permeation, as well as optimize membrane performance. The MR achieved ammonia conversions of up to 85 %, surpassing the thermodynamic limits typical of traditional reactors (TR). Hydrogen recovery rates reached 97 %, with purity consistently exceeding 90 %. Notably, the MR demonstrated up to 3.6 times higher ammonia conversion compared to conventional TR, highlighting its significant advantages for ammonia decomposition applications.

Biogas represents an important renewable source alternative to fossil fuels, which can significantly contribute to the reduction of global warming and the gradual decarbonisation. In this work, the purification of CH4 and CO2 from a biogas mixture was investigated using DD3R zeolite membrane modules, as a possible solution to replace the traditional techniques at higher environmental impact (i.e., solvent absorption and cryogenic distillation). Multistage membrane configurations operating at 25°C and 30bar were proposed and explored to get highly pure biomethane (concentration of 98%) and carbon dioxide (concentration of 99.5%), imposing a recovery of both the species higher than 90%. Then, an economic analysis was carried out, evaluating the economic potential of each configuration as a function of several parameters, such as membrane module cost, biomethane selling price, CO2 permeance, CO2/CH4 selectivity, feed flow rate and pressure. The multistage schemes were found to be promising in a wide range of zeolite membrane module cost (i.e., up to 2000 $/m2), providing positive values of the economic potential, due to the good recovery of both the components, which produced high revenues. The increment of the CO2 permeance and, especially, of the feed flow rate (i.e., plant size) allowed for a more profitable process. In particular, if feed flow rate increased from 100 to 1000 Nm3/h, the economic potential would grow of about 12 times, from 113 to 1370 thousand dollars per year. Hence, this preliminary economic assessment showed that zeolite membranes can be successfully used in biogas treatment to get pure CH4 and CO2. Such an analysis can be applied to any membrane materials, once permeance and selectivity are fixed.

Biomass gasification is a viable solution for generating H-2; however, the syngas produced must be upgraded to make H-2-containing streams suitable for other applications, such as renewable methanol production, by adjusting the H-2/CO ratio. In this study, for the first time in the literature, the separation properties of carbon hollow fiber membranes in binary and quaternary H-2-containing mixtures with varying compositions were systematically explored. It was found that the developed carbon membranes exhibit relatively good selectivity for (H-2+CO2) in mixtures with other gases such as N-2 and CO, which are commonly present in syngas. A CO permeance of 0.8-1 GPU and a H-2/CO selectivity of 30 were achieved for the first time through both single gas and mixed gas permeation testing. Furthermore, in the context of using these membranes for syngas upgrading, such as in an integrated biomass-to-biofuel (methanol) process for hydrogen enrichment or carbon capture and conversion, a technical feasibility analysis based on the separation performance of the carbon membrane system for syngas ratio adjustment and N-2 removal was carried out. The results indicate that the prepared carbon membranes have the potential to adjust the H-2/CO ratio to 1-3 if a N-2 removal ranging from 80 to 90% is acceptable.

This work analysed the permeation of binary and ternary H2-containing mixtures through a SAPO-34 membrane, aiming at investigating how hydrogen influences and its permeation is influenced by the presence of the other gaseous species, such as CO2 and CH4. We considered the behaviour of various gas mixtures in terms of permeability and selectivity at various temperatures (25-300 degrees C), feed pressures (400-1000 kPa) and compositions by means of an already validated mass transport model, which is based on surface and gas translation diffusion. We found that the presence of CO2 and CH4 in the H2-containing mixtures influences in a similar way the H2 permeation, reducing its permeability of about 80% compared to the single-gas value because of their stronger adsorption. On the other hand, H2 promotes the permeation of CO2 and CH4, causing an increment of their permeability with respect to those as single gases. These combined effects reflected in interesting selectivity values in binary mixture (e.g., CO2/H2 about 11 at 25 degrees C, H2/CH4 about 9 at 180 degrees C), which showed the potential of SAPO-34 membranes in treating of H2 -con-taining mixtures.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

This work focuses on the utilization of a two stages inorganic membrane-based system to generate and recover decarbonized hydrogen in order to meet the targets set by the European Clean Hydrogen Partnership under the Strategic Research & Innovation Agenda 2021-2027. In the first stage, a CH4:CO2 = 60:40 mixture simulating a biogas stream is used to generate a COx-free hydrogen via steam reforming reaction carried out in a tubular Pd-Ag membrane reformer, packed with a novel non-commercial 7 wt%Ni-0.5 wt%Ru/La0.3Y0.3Zr0.4Ox catalyst, prepared by solution combustion method. The catalyst was characterized by XRD, TPR and TEM techniques. The analyses reveal well-distributed active metal particles interacting differently with the support (weakly and strongly). In particular, the XRD pattern shows the formation of perovskite and nickel oxide in addition to the pyrochlore phase. This behaviour indicates a low solubility of Ni in the pyrochlore structure. Reaction mea-surements were carried out at a temperature of 673 K, in the total pressure range between 250 kPa divided by 350 kPa, weight hourly space velocity (WHSV) of 0.2 h-1, H2O/CH4 feed molar ratio between 1.5 and 2, feeding N2-sweep gas in the permeated side. As best results of Stage 1, CH4 conversion equal to 99% (@ H2O/CH4 feed molar ratio = 2 and feed pressure of 250 kPa) and a COx-free H2 recovery of 40% were reached. In the second stage, the unpermeated stream of Stage 1 rich in hydrogen was fed to a supported Pd/Al2O3 membrane separator to further recover high grade hydrogen at the same temperature and total pressure set in Stage 1. The maximum hydrogen recovery equal to 67% was reached at 673 K and 350 kPa, with a purity of the recovered stream equal to 99.9%. The total hydrogen recovered in the permeate streams of Stage 1 and Stage 2 was equal to 80% of the total hydrogen produced during the steam reforming reaction, showing an average purity equal to 99.99%, which allowed to meet the established targets. The work further analized and discussed the experimental results of the integrated system by means of performance indexes.

In this work, the concentration and purification of hydrogen from multicomponent gas mixtures, such as syngas and H2:CH4 blends, were investigated by simulations of multi-stage membrane configurations. In particular, the separation performance of carbon, polymeric and Pd-alloy membranes were analyzed for obtaining a final H2 stream completely pure with a recovery higher than 90%. Carbon and polymer membranes in multistage configuration confirmed their suitability to be used as concentration units able to increase the hydrogen content in the gas mixture. A further purification of these pre-concentrated streams was carried out adding Pd-alloy membranes that were able to recover more than 90% of hydrogen fully pure. The use of an integrated process constituted of a concentration stage based on polymer/carbon membranes followed by a purification stage based on a Pd-alloy membrane allowed to drastically reduce the operating pressure and, moreover, save Pd-alloy membrane area.

The fast growing of membrane systems in industrial applications suggests the dissemination of last results, particularly in the areas of strategic interest. In this contribution, the role of membrane engineering for more sustainable industrial cycles, following the Process Intensification strategy, is reported. The development of Membrane Crystallizers (MCr) with specific focus on their application to the treatment of brines is presented, together with the use of molecular dynamic simulation to help in the selection of the most appropriate membrane material. The potential of membrane reactors for CO2 valorization through new designs is also highlighted. Moreover, tools like exergy analyses and new metrics to compare the performance of membrane operations to conventional ones in the logic of Process Intensification are discussed.

The growing freshwater scarcity has caused increased use of membrane desalination of seawater as a relatively sustainable technology that promises to provide long-term solution for the increasingly water-stressed world. However, the currently used membranes for desalination on an industrial scale are inevitably prone to fouling that results in decreased flux and necessity for periodic chemical cleaning, and incur unacceptably high energy cost while also leaving an environmental footprint with unforeseeable long-term consequences. This extant problem requires an immediate shift to smart separation approaches with self-cleaning capability for enhanced efficiency and prolonged operational lifetime. Here, we describe a conceptually innovative approach to the design of smart membranes where a dynamic functionality is added to the surface layer of otherwise static membranes by incorporating stimuli-responsive organic crystals. We demonstrate a gating effect in the resulting smart dynamic membranes, whereby mechanical instability caused by rapid mechanical response of the crystals to heating slightly above room temperature activates the membrane and effectively removes the foulants, thereby increasing the mass transfer and extending its operational lifetime. The approach proposed here sets a platform for the development of a variety of energy-efficient hybrid membranes for water desalination and other separation processes that are devoid of fouling issues and circumvents the necessity of chemical cleaning operations.

Membrane-based gas separation processes are currently being implemented at different scales for several industrial applications. The optimal design of such processes, which is of key importance for their large-scale commercial deployment, has been extensively studied through parametric analyses and optimisation procedures. Nevertheless, the applicability of such design methodologies is generally limited by the large computational time and effort they require. In this work, surrogate models based on artificial neural networks are developed to circumvent the lengthy optimisation of a one-stage and two-stage cascade membrane-based gas separation process. In 200 ms, the surrogate model generates a Pareto front that describes the optimal trade-off between the process specific electricity consumption and productivity based on given input data, i.e., membrane material properties, feed composition and separation target. Whereas the surrogate model is applicable to any binary gas mixture, here its features are illustrated by creating process performance maps for post-combustion CO2 capture. Such maps provide valuable insights on: (i) attainable gas separation regions in term of CO2 recovery and CO2 purity, and (ii) the impact of membrane material, feed composition and separation target on the Pareto fronts and the optimal operating conditions.

Polymeric hollow fiber membranes (HFMs) are in high demand for gas separation due to their superior processability and cost-effectiveness, despite exhibiting high vulnerability to plasticization. In this study, we present a new dip-coating technique for fabricating defect-free and plasticization-resistant polyimide HFMs on a crosslinked polyimide/polysilsesquioxane hollow fiber support. This is achieved through an in situ process involving thermal imidization and cross-linking of a polyamic acid (PAA) precursor solution. The use of a thermally stable cross-linked nanoporous hollow fiber support ensures the coating of various glassy PAA solutions prepared by different dianhydrides and diamine monomers without disturbing its internal pore structure. The resulting polyimide hollow fiber membranes enhanced CO2/CH4 separation performance compared to assynthesized polyimide solution-coated counterpart. It is because in situ thermal imidization and cross-linking of PAA solutions induced the formation of more imine linkages, possibly generating larger free volume elements due to the disturbance of intersegmental chain packing while maintaining sufficient chain rigidity. Additionally, the membrane's practical applicability was confirmed as the hollow fibers demonstrated resistance to plasticization when subjected to an equimolar CO2/CH4 mixed feed of approximately 50 bar. Our simple but versatile dip-coating approach allows for the formation of highly plasticization-resistant polyimide HFMs.

The transformation of matter (feedstocks, ores) and energy has constantly been at the core of human societies. For a long time a very limited number of final products was produced (metals, salts, textiles), with renewable energy as the only possibility (biomass and, to a lesser extent, windmill). With the advent of the Industrial Revolution in the late 18th century, a radical transformation occurred, especially thanks to the use of fossil energy (coal first, and oil and gas later on). The so-called Industrial Revolution first took place in the mining and metallurgical sector. It gradually spread all over industrial sectors, with a strong impact on chemical production and transportation, among others. Today, the chemical production system (usually referred to as CPI for Chemical Process Industries) consumes 10% of world oil production, leading to thousands of different molecules, materials, and products. The petrochemical industry remains a key activity, draining all types of applications (agriculture, buildings, health, energy, materials, house care, textiles, transportation, communications, etc.). CPI are considered as playing a central role in today's society, as an "industry of industries." It is important to note that CPI showed a significant evolution of their priorities through the ages. A simplified list of targets by decades has been proposed. With the risk of oil shortage and the increasing threat of global warming, a shift to a circular economy is commonly considered an absolute and urgent necessity.