(671a) Intensifying Blue Hydrogen Production from Bio-Ethanol Steam Reforming Via Pd-Ag-Y Membrane Reactor

The greenhouse gases (GHGs) emissions have increased to unprecedented levels due to rapid industrial development and population growth. Consequently, transitioning from fossil fuels to clean and renewable energy sources is essential for mitigating climate change. Hydrogen is one of the promising energy carriers that can be generated from both conventional (fossil fuels) and renewable resources (bio-fuels and water). Currently, H₂ is mainly produced by methane steam reforming, which is an energy-intensive process that emits approximately 9 kg CO₂/kg H₂ produced [1]. Therefore, it is necessary to transition to renewable sources for hydrogen production by steam reforming. Among bio-fuel sources, bioethanol is favored because it has a high energy content and is less toxic than hydrocarbon fuels. Another benefit of bioethanol is that it can be obtained from food and material wastes. Additionally, bioethanol steam reforming (BESR) is a viable method for efficiently producing renewable hydrogen. However, BESR includes side reactions that produce coke and unwanted products [2,3]. The reactions include:

C₂H₅OH + 3H₂O <=> 2CO₂ + 6H₂ ΔH°₂₉₈ = 157 kJ.mol⁻¹ (Complete steam reforming)

Side reactions:

C₂H₅OH <=> CH₃CHO + H₂ ΔH°₂₉₈ = 68.9 kJ.mol⁻¹ (Dehydrogenation)

C₂H₅OH <=> C₂H₄ + H₂O ΔH°₂₉₈ = 45.5 kJ.mol⁻¹ (Dehydration)

2C₂H₅OH <=> (C₂H₅)₂O + H₂O ΔH°₂₉₈ = -24 kJ.mol⁻¹ (Diethyl ether formation)

C₂H₄O <=> CH₄ + CO ΔH°₂₉₈ = -164.8 kJ.mol⁻¹ (Acetaldehyde decomposition)

2C₂H₅OH <=> CH₃COCH₃ + CO + 6H₂ ΔH°₂₉₈ = 4.1 kJ.mol^-1 (Acetone formation)

CO₂ + H₂ <=> CO + H₂O ΔH°₂₉₈ = 41.4 kJ.mol⁻¹ (Reverse water gas shift reaction)

Coke formation reactions:

CH₄ <=> C + 2H₂ ΔH°₂₉₈ = 74.9 kJ.mol⁻¹ (Methane decomposition)

2CO <=> CO₂ + C ΔH°₂₉₈ = -172.6 kJ.mol⁻¹ (Boudouard reaction)

C₂H₄ <=> C + 2H₂ ΔH°₂₉₈ = -52.3 kJ.mol⁻¹ (Coke formation)

In contrast to conventional reactors, the BESR reaction can be efficiently carried out in a membrane reactor (MR), integrating reaction and separation within a single unit. This approach enables the in situ removal of hydrogen, shifting the reaction equilibrium toward higher conversion while mitigating undesirable side reactions and operating conditions. Among various membrane materials, palladium-based MRs are particularly advantageous due to their complete hydrogen selectivity. However, pure Pd membranes are susceptible to embrittlement and exhibit limited thermal and chemical stability [1,4]. Alloying Pd with metals such as Ag, Cu, Au, and Y has been investigated to enhance its performance. Specifically, the addition of Ag and Y has been shown to improve hydrogen permeability, structural stability, and resistance to degradation, making Pd-based alloys more viable for long-term operation in hydrogen separation and catalytic processes. In our previous study, the Pd-Ag-Y membrane showed one of the highest hydrogen permeability among other Pd-alloy membranes [5,6].

In this work, the performance of the Pd-Ag-Y MR will be investigated by performing the BESR reaction at different temperatures (300-500 °C) and pressures (2-5 bar). Both non-noble and noble catalysts, such as Co/CeO₂ and Ru/CeO₂ will be selected to be packed in the MR. The CeO₂ support is selected for both catalysts to inhibit coke formation reactions. A simulated bioethanol mixture will be used for the reaction. In addition, the effect of different catalysts and several operating conditions will be analyzed in terms of conversion, hydrogen yield, recovery, and long-term stability. Finally, the pristine and used membranes will be characterized by a Scanning Electron Microscope (SEM), Energy Dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD).

References

[1] O. Jazani, J. Bennett, S. Liguori, Carbon-low, renewable hydrogen production from methanol steam reforming in membrane reactors – a review, Chemical Engineering and Processing - Process Intensification (2023) 109382. https://doi.org/10.1016/j.cep.2023.109382.

[2] O. Jazani, M. Adejumo, S. Liguori, Chapter 3 - Alcohol reforming processes in membrane reactors, in: A. Basile, K. Ghasemzadeh (Eds.), Current Trends and Future Developments on (Bio-) Membranes, Elsevier, 2025: pp. 51–79.https://doi.org/10.1016/B978-0-443-13876-8.00008-2.

[3] O. Jazani, M. Adejumo, M.A. Elharati, S. Liguori, Low-Carbon Hydrogen Production via Ethanol Reforming Reactions in Membrane Reactors: Recent Advances and Future Directions, Energy & Fuels 38 (2024) 19992–20014. https://doi.org/10.1021/acs.energyfuels.4c02755.

[4] A. Yoosefdoost, O. Jazani, S. Liguori, A. Das, R.M. Santos, Toward Carbon-Negative Methanol Production from Biogas: Intensified Membrane Reactor, ChemCatChem n/a (2024) e202400698. https://doi.org/10.1002/cctc.202400698.

[5] O. Jazani, M.A. Elharati, S. Liguori, Effects of porous supports and binary gases on hydrogen permeation in Pd–Ag–Y alloy membrane, J Memb Sci 713 (2025) 123327. https://doi.org/10.1016/j.memsci.2024.123327.

[6] O. Jazani, J. Bennett, S. Liguori, Effect of temperature, air exposure and gas mixture on Pd82–Ag15–Y3 membrane for hydrogen separation, Int J Hydrogen Energy (2023). https://doi.org/10.1016/j.ijhydene.2023.08.152