(699g) Simulated Biogas Dry Reforming for Synthesis Gas Production in Ternary Pd-Ag-Y Membrane Reactor with Ru/CeO2 Catalyst

Biogas dry reforming (BDR) reaction has attracted attention due to the utilization of CH₄ and CO₂ to produce synthesis gas (H₂ and CO). The BDR reaction is an endothermic reaction that is performed at a high temperature of 800-1000 °C and pressure of 15-30 bar to avoid the formation and deposition of coke [1,2]. The main reaction is reported to be as:

CH₄ + CO₂ <=> 2CO + 2H₂ ΔH°₂₉₈ = 247 kJ mol⁻¹ (methane dry reforming) (1)

However, several side reactions take place in the reactor resulting in a reduction of the reaction performance in terms of conversion and yield. The side reactions include reverse water gas shift (RWGS), methanation, and coke formation via methane decomposition and Boudouard reactions [1,2] and they are reported below

Unwanted reaction:

CO₂ + H₂ <=>CO + H₂O ΔH°₂₉₈ = 41.4 kJ mol⁻¹ (reverse water gas shift reaction) (2)

CH₄ + H₂O <=> CO + 3H₂ ΔH°₂₉₈ = 206 kJ mol⁻¹ (methane steam reforming) (3)

CO₂ + 4H₂ <=> CH₄ + 2H₂O ΔH°₂₉₈ = -165 kJ mol⁻¹ (methanation reaction) (4)

Carbon formation reaction:

CH₄ <=> 2H₂ + C ΔH°₂₉₈ = 75 kJ mol⁻¹ (methane decomposition) (5)

CO <=> CO₂ + C ΔH°₂₉₈ = -173 kJ mol⁻¹ (Bouduard reaction) (6)

Alternatively, to a conventional reactor, the BDR reaction could be performed in a membrane reactor (MR) where reaction and separation occur simultaneously. This alternative technology allows for the removal of hydrogen from the reaction zone by shifting the reaction towards more products formation and avoiding the side reactions. Among different types of membranes, palladium MRs are an excellent option for hydrogen production and separation because of their complete selectivity towards hydrogen permeation. Nevertheless, pure Pd membranes suffer from drawbacks such as embrittlement, and low thermal and chemical resistance. The addition of some metals, such as Ag, Cu, Au, and Y can enhance their properties. For instance, the addition of Ag and Y to pure Pd membranes has shown enhancement in permeability, stability, and resistivity [3,4]. The Pd-Ag-Y membrane showed one of the highest hydrogen permeability in our previous work. A Ru catalyst is selected to perform the BDR reaction due to its higher activity towards reactants than the Ni catalyst. Moreover, the CeO₂ support helps to inhibit the coke formation [1,5].

In this work, the performance of the Pd-Ag-Y MR will be investigated by performing the BRD reaction at different temperatures (500-600 °C) and pressures (2-5 bar). A simulated mixture of biogas will be produced in the lab with a composition of 70% CH₄, and 25% CO₂ balanced in N₂ [6]. In addition, the effect of a small amount of air on the MR performance in terms of conversion, hydrogen production, recovery, and long-term stability will be analyzed. Finally, the pristine and used membrane will be characterized by Scanning Electron Microscope (SEM), Energy Dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD).

References

[1] Y. Gao, J. Jiang, Y. Meng, F. Yan, A. Aihemaiti, A review of recent developments in hydrogen production via biogas dry reforming, Energy Convers Manag 171 (2018) 133–155. https://doi.org/10.1016/j.enconman.2018.05.083.

[2] A. Nishimura, T. Takada, S. Ohata, M.L. Kolhe, Biogas Dry Reforming for Hydrogen through Membrane Reactor Utilizing Negative Pressure, Fuels 2 (2021) 194–209. https://doi.org/10.3390/fuels2020012.

[3] 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.

[4] F. Gallucci, S. Tosti, A. Basile, Pd-Ag tubular membrane reactors for methane dry reforming: A reactive method for CO2 consumption and H2 production, J Memb Sci 317 (2008) 96–105. https://doi.org/10.1016/j.memsci.2007.03.058.

[5] N.A.K. Aramouni, J.G. Touma, B.A. Tarboush, J. Zeaiter, M.N. Ahmad, Catalyst design for dry reforming of methane: Analysis review, Renewable and Sustainable Energy Reviews 82 (2018) 2570–2585. https://doi.org/https://doi.org/10.1016/j.rser.2017.09.076.

[6] Y. Li, C.P. Alaimo, M. Kim, N.Y. Kado, J. Peppers, J. Xue, C. Wan, P.G. Green, R. Zhang, B.M. Jenkins, C.F.A. Vogel, S. Wuertz, T.M. Young, M.J. Kleeman, Composition and Toxicity of Biogas Produced from Different Feedstocks in California, Environ Sci Technol 53 (2019) 11569–11579. https://doi.org/10.1021/acs.est.9b03003.