Production of hydrocarbon from CO2-FT reaction over Fe-based catalysts: Effect of the promoter and bimetallic Fe-Metal carbide

Abstract

The present work evaluates the effect of two alkali promoters (K and Mg) over Fe-monometallic (Fe, Mo, and Re) and bimetallic Fe-metal carbides catalysts in the CO₂-FT reaction. Catalysts were characterized by N₂-sorption isotherm, XRD, TPR, and XPS techniques and evaluated at 350ºC, 20 bar, CO₂/H₂ ratio of 1:3, and GHSV of 2000 mL·g⁻¹ ·h⁻¹ . The most active catalysts were K-Mo₂C, which produced principally CO and C₄⁺ products, while the K-Re-Fe and Mg-Re-Fe catalysts were the most selective toward hydrocarbons. From the characterization results, Mg was shown to promote the formation of more reduced/carburized phases in all the systems, enhancing the RWGS and FTS. In contrast, K promotes the formation of smaller particles. An anti-synergistic effect was detected in the K-Fe-Mo catalyst and associated with forming a bimetallic FeMo phase that is less active in CO₂ conversion. In contrast, in the case of Re-Fe bimetallic systems, the catalytic results were associated with a synergistic effect between Fe and Re.