Hydrogen production via biogas reforming reaction in tubular Pd/YSZ membrane reactor

Abstract

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.