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Publication Date: 2026
Membranes (20770375)16(1)
The biogas dry reforming reaction offers a promising route for syngas production while simultaneously mitigating greenhouse gas emissions. Membrane reactors have proven to be an excellent option for hydrogen production and separation in a single unit, where conversion and yield can be enhanced over conventional processes. In this study, a Pd/YSZ membrane integrated with a Ru/CeO2 catalyst was evaluated for biogas reaction under varying operating conditions. The selective removal of hydrogen through the palladium membrane improved reactant conversion and suppressed side reactions such as methanation and the reverse water–gas shift. Experiments were performed at temperatures ranging from 500 to 600 °C, pressures of 1–6 bar, and a gas hourly space velocity (GHSV) of 800 h−1. Maximum conversions of CH4 (43%) and CO2 (46.7%) were achieved at 600 °C and 2 bar, while the maximum hydrogen recovery of 78% was reached at 6 bar. The membrane reactor outperformed a conventional reactor, offering up to 10% higher CH4 conversion and improved hydrogen production and yield. Also, a comparative analysis between Ru/CeO2 and Ni/Al2O3 catalysts revealed that while the Ni-based catalyst provided higher CH4 conversion, it also promoted methane decomposition reaction and coke formation. In contrast, the Ru/CeO2 catalyst exhibited excellent resistance to coke formation, attributable to ceria’s redox properties and oxygen storage capacity. The combined system of Ru/CeO2 catalyst and Pd/YSZ membrane offers an effective and sustainable approach for hydrogen-rich syngas production from biogas, with improved performance and long-term stability. © 2026 by the authors.
Publication Date: 2025
Journal of Membrane Science (0376-7388)713
This study investigates the effects of various porous supports and the presence of additional gases in the feed on hydrogen permeation using an unsupported Pd82–Ag15–Y3 membrane. The pore sizes and thicknesses of metallic supports varied from 1 to 270 μm and 50–3000 μm, respectively. The membrane was unsupported, synthesized by cold-rolling, and characterized by a thickness of 38 μm. The tests were performed at 400 °C with pressures ranging from 1.4 to 3 bar. Results showed that the unsupported Pd82–Ag15–Y3 membrane reached 12 % and 267 % higher hydrogen permeation than the supported membrane by 1 μm pore size and 50 μm thick woven mesh, and 1 μm pore size and 3 mm thick of porous stainless steel (PSS), respectively. The unsupported Pd82–Ag15–Y3 membrane showed one of the highest hydrogen permeability in the literature (7.5 × 10−8 mol m−1 s−1.Pa−0.5 at 400 °C). However, the presence of porous supports used to enhance the mechanical stability of the membrane negatively affected the hydrogen permeation due to mass transfer limitation. In addition, the presence of supports induced an unreal ‘n’ value for the Pd-based membrane, where the ‘n’ value is the exponent of the driving force in the equation of hydrogen transport, varying between 0.5 and 1. In particular, for the unsupported membrane, the ‘n’ value was 0.6, but it increased to 0.7 and 0.8 when supports with 1 μm pore size and 50 μm thick and 5 μm and 80 μm thick were utilized. Binary hydrogen permeation tests were also performed in the presence of N2, CH4, CO2, and CO at 400 °C by using unsupported and supported membranes to investigate the reduction in hydrogen permeation flux due to the effect of the supports plus the effect of the presence of other gas. The results revealed that CO had the highest inhibition effect for all the unsupported and supported membranes tested due to competitive adsorption on the surface. No superficial adsorption on the membrane was observed for N2, CH4, and CO2 during permeation, and they inhibited hydrogen permeation mainly due to depletion, dilution, and concentration polarization. The PSS_1–3000 indicated the lowest hydrogen permeation between the gas mixture and the porous support, whereas the presence of 40 % of the binary gas mixture had lower hydrogen permeation than porous support except for the PSS. © 2024 Elsevier B.V.
Publication Date: 2025
Chemical Engineering Journal (1385-8947)523
This study examines hydrogen gas production from biogas dry reforming in a Pd/YSZ membrane reactor (MR) packed with a Ni-based catalyst. The MR performance was investigated in terms of hydrogen permeation, methane and carbon dioxide conversion, hydrogen recovery, and hydrogen yield with a temperature range of 500–600 °C and pressures between 1 and 5 bar. At 600 °C, the Pd/YSZ membrane demonstrated a hydrogen permeance of 1.8 × 10−6 mol·m−2·s−1·Pa−1 and an apparent activation energy of 11.9 kJ/mol. Increasing the temperature from 500 °C to 550 °C at 5 bar resulted in CH4 and CO2 conversions increasing by 26 % and 6 %, respectively, while hydrogen recovery and yield improved by 6 % and 24 %. Our results showed higher CH4 conversion than other membrane reactors and conventional reactors under the same operating conditions. Experimental results indicate that methane decomposition occurs simultaneously with biogas reforming, contributing significantly to coke formation, particularly at elevated temperatures. Introducing small amounts of oxygen into the feed effectively reduced carbon deposition from 1.0 g to 0.65 g at 550 °C and 5 bar by oxidizing deposited carbon. However, this also led to a reduction in CO2 conversion from 22 % to 6 %, due to the consumption of CO2 during carbon oxidation reactions. Importantly, the addition of O2 did not negatively impact membrane and catalyst activity, and hydrogen recovery and yield remained stable. Additionally, steam regeneration was shown to effectively remove carbon deposits from both the catalyst and membrane, while simultaneously generating hydrogen via gas–solid reactions. So far, no research study has evaluated the effect of steam for coke removal on Pd-based membrane reactors. The MR exhibited stable hydrogen permeation flux and maintained complete selectivity over 800 h of continuous operation. Up to now, no Pd-based membrane has been resisted for this period under dry reforming reaction. Thus, Pd-YSZ MR demonstrates strong long-term operational stability and viability for low-carbon hydrogen production from renewable biogas. © 2025 Elsevier B.V.
Publication Date: 2025
ChemCatChem (18673880)17(3)
The modern world's major challenges, such as global warming, air pollution, and increasing energy demands, escalate the importance of sustainable development and transition toward renewables using innovative and environmentally friendly solutions, such as intensifying chemical processes, to reduce carbon footprints effectively. Aiming to enhance the process toward negative carbon emissions, this perspective explores the intensified membrane reactors for reducing the energy intensity of converting biogas into methanol, a versatile chemical feedstock, and renewable liquid fuel. Syngas and methanol synthesis processes, catalysts, and membranes were explored, and novel reactor designs were proposed. Introduction of selective membranes into the catalytic reaction zone to combine synthesis separation steps could enhance the system efficiency and intensify the process by recycling energy and materials, besides reducing costs and required energy for the separation process: the continuous harnessing of products shifts reactions toward desired species while recycling energy and materials enhances the process efficiency, and separating water from methanol reduces the required energy and costs of extra processes for methanol separation. The successful implementation of this technology holds significant promise for sustainable developments in producing chemicals and renewable fuel from renewable biogas and reducing methane and carbon dioxide emissions toward achieving carbon-negative technologies. © 2024 The Author(s). ChemCatChem published by Wiley-VCH GmbH.
Publication Date: 2024
pp. 51-79
Hydrogen is considered the energy carrier of the future since it produces only water when it is fed to polymer electrolyte membrane fuel cells. Currently, hydrogen is mainly produced by methane steam reforming, which is an energy-intensive process emitting approximately 9kg-CO2/kg-H2-produced. However, using alcohols from biofeedstock could reduce the CO2 emission. In addition, green hydrogen could be produced if a membrane reactor (MR) is used. The MR has the main benefit to intensify the process in terms of energy and efficiency since hydrogen is produced and simultaneously separated from the CO2 by a membrane. In this chapter, the relevant progress in topics of alcohol reforming via MR technology and the effect of operating conditions on the reforming reaction in MRs are reviewed and discussed. Moreover, mathematical models used for modeling reforming processes in MRs are discussed. © 2025 Elsevier Inc. All rights reserved.
Publication Date: 2024
International Journal of Hydrogen Energy (03603199)51pp. 624-636
Material characterization, hydrogen permeation, and separation properties of a novel ternary Pd82Ag15Y3 membrane were evaluated by feeding single gases and several mixtures at temperature and pressure ranges of 300–600 °C and 1.0–3.0 bar (abs), respectively. The Pd82–Ag15–Y3 membrane was prepared by cold rolling and was characterized by ∼38 μm of thickness. When exposed to air at different temperature and constant pressure of 1 bar, the membrane showed good thermal and chemical stability. In particular, its surface area increased from 615 μm2 at 25 °C to 685 μm2 at 500 °C indicating a potential improvement of hydrogen permeation. However, several agglomerates consisting of metal oxides were formed on the surface at the highest temperature. The temperature was -then- kept constant at 400 °C and the pressure was varied to analyze the effects of singles gases and several mixtures on the hydrogen permeation characteristics. When exposed to pure gases, such as H2 and N2, the membrane showed an H2 permeability of 9.1 × 10−11 mol m−1 s−1.Pa−0.9 and “n” value of 0.9 due to the presence of Y, while no N2 was detected in the permeate stream, respectively. So, the membrane was considered to be completely selective towards H2 permeation. When mixtures were used, the hydrogen permeation decreased by its original value due to the presence of other gases, such as N2, CH4, CO2 and CO. The presence of CO particularly affected the H2 permeating flux due to the competitive adsorption of both gases on the Pd-alloy surface. Finally, the Scanning Electron Microscope (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), Atomic Force Microscope (AFM) and X-ray diffraction (XRD) analysis were performed to observe any changes in the surface and structure of pristine and used membrane. © 2023 Hydrogen Energy Publications LLC
Publication Date: 2024
Energy and Fuels (08870624)38(21)pp. 19992-20014
The emission of greenhouse gases (GHGs) has escalated to unprecedented levels due to the extensive use of fossil fuels for industrial development and population growth. Consequently, the transition to clean and renewable energy sources is critical for mitigating climate change. Hydrogen is considered a promising energy carrier that can be produced from both conventional (fossil fuels) and renewable resources (biofuels and water). Among renewable sources, ethanol is favored over other bioalcohols because it has a high energy content and is less toxic than hydrocarbon fuels. In addition, ethanol reforming represents a viable method of efficiently producing renewable hydrogen. To enhance this process, innovative technologies have been developed, particularly through the use of a membrane reactor (MR) technology. In MRs, the reaction and separation processes occur simultaneously, which improves the selectivity and yield while reducing operating conditions and preventing coke formation. This study aims to highlight recent advancements in ethanol reforming reactions─including steam reforming, partial oxidation, and autothermal reforming reactions─to produce renewable, low-carbon hydrogen using MR technology. In particular, the central focus is to provide a comprehensive analysis of the performance of different MRs, shedding light on their efficacy, scalability, and potential limitations in the context of renewable hydrogen production from ethanol reforming. By exploring these aspects, this study attempts to inform strategic decisions and advancements in sustainable energy technologies, facilitating the transition toward a greener, more resilient energy landscape. © 2024 American Chemical Society.
Publication Date: 2023
Chemical Engineering and Processing - Process Intensification (02552701)189
The development of sustainable and new technologies based on renewable energy sources is mandatory due to the anthropogenic climate changes and the depletion of fossil fuels. Hydrogen is considered a clean alternative able to produce only water and energy when consumed in fuel cell. However, the main issue for large-scale hydrogen commercialization is its storage and transportation. One way to solve this problem is to use energy carriers, such as methanol, which is liquid at ambient conditions, low reforming temperature, holds relatively highly H/C ratio and can be produced by biomass. So, hydrogen can be later produced on-demand by methanol steam reforming reaction. In order to produce carbon-low hydrogen alternative technologies are considered. In particular, membrane reactors are raising attention. The use of membrane reactor enables to increase the process selectivity, lower the temperature of the reaction while avoiding the formation of coke, and obtain a high pure hydrogen stream. This review provides an overview of the recent progress to produce hydrogen from methanol reforming in convectional and membrane reactors. © 2023
Publication Date: 2023
pp. 67-94
Ammonia is currently considered as an energy carrier because it allows for hydrogen storage in liquid-phase under mild conditions. Although ammonia can be directly employed for energy application, its use in proton-exchange membrane fuel cells (PEMFC) requires two steps: decomposition into hydrogen and nitrogen, and separation of hydrogen. The combination of ammonia decomposition and in situ separation of hydrogen via membrane reactor (MR) can lead to relax the thermodynamic constraints, reduce the footprint of this technology, and intensify the process. Indeed, in the field of hydrogen production and separation, the use of MR induces the selective hydrogen removal from the reaction zone through the membrane enabling a higher conversion and hydrogen yield compared to the conventional reactor. In this chapter, the relevant progress achieved so far, the most relevant topics of ammonia decomposition via MR technology and the effects of the most important parameters affecting the reaction in MRs are described and critically reviewed. In addition, an overview on the mathematical models used for simulating ammonia decomposition in MR is also presented and discussed. © 2024 Elsevier Inc. All rights reserved.
Publication Date: 2022
pp. 424-426
Hydrogen permeation and separation properties of a ternary Pd-alloy are evaluated at temperature and pressure range of 300 °C and 600 °C and 2-5 bar (abs), respectively. The membrane Pd82-Ag15-Y3 is unsupported, prepared by cold rolling and it is characterized by ~ 35 μm of thickness. The membrane shows good thermal and chemical stability when exposed to air and at different temperature. In particular, its surface area increases by 2.5x from room temperature to 600 °C indicating a potential improvement of hydrogen permeation. The permeation characteristics of the membrane and the effects of the other gases on hydrogen permeation will be investigated by varying temperature and pressure evaluating the effects of dilution, depletion, concentration polarization, and competitive adsorption on the H2 permeating flux. © 2022 Proceedings of WHEC 2022 - 23rd World Hydrogen Energy Conference: Bridging Continents by H2. All rights reserved.
