Design and scale-up of a Cr-free Fe-Al-Cu catalyst for hydrogen production from waste-derived synthesis gas

Herein, we have prepared a series of Cr-free Fe-Al-Cu catalysts by the homogeneous one-step co-precipitation method and examined their ability to promote the water gas shift (WGS) reaction and thus facilitate the production of hydrogen from waste-derived synthesis gas. The prepared catalysts are confirmed to possess γ-Fe₂O₃, which can be more easily transformed into Fe₃O₄ than α-Fe₂O₃. The surface area, Fe₃O₄ crystallite size, reducibility, and Cu dispersion of these catalysts significantly depend on the concentrations of metal precursor. The catalysts effectively promote the WGS reaction without facilitating undesirable side reactions, achieving efficient hydrogen production and high CO conversion. The characteristics of the best-performing sample are preserved when the production is scaled up by a factor of 40 and thus obtained large-scale Fe-Al-Cu catalyst exhibits excellent reducibility and high CO conversion. Both commercial Fe-Cr and large-scale Fe-Al-Cu catalysts achieve close-to-equilibrium CO conversions at a gas hourly space velocity (GHSV) of 3000 mL g⁻¹ h⁻¹, but the latter showed a higher conversion than the former at a GHSV of 40,057 mL g⁻¹ h⁻¹ owing to the promotional effect of Cu on the easier reducibility of Fe species and the formation of additional Cu active sites. Thus, we demonstrate the possibility of finding Cr-free alternatives and show that the reducibility, Fe₃O₄ crystallite size, and Cu dispersion of the best-performing catalyst could be maintained upon upscaling, which made this catalyst well suited for converting waste-derived synthesis gas into H₂.