Tuning the hydrogenation of CO2 to lower olefins: Impact of Pt in K–doped Fe–Mn catalysts

Fe-based catalysts are promising for the hydrogenation of CO 2 to olefins, contributing to the mitigation of CO 2 emissions. Low-pressure conditions (∼1 MPa) are preferred for the selective synthesis of lower olefin because these conditions suppress carbon chain growth and olefin re-absorption which leads to hydrogenation of olefins to paraffins. In this study, K-doped Fe–Mn–Pt/Al 2 O 3 catalysts that could react at 1 MPa were prepared, with a focus on the role and position of Pt active sites. K–Fe 17 Mn 2 /Pt 1 /Al 2 O 3 was prepared by first supporting Pt on Al 2 O 3 followed by Fe–Mn oxide; it exhibited the highest C 2–5 olefin selectivity of 28 %. Pt promoted the reverse water-gas shift reaction, and in combination with Mn, facilitated iron oxide reduction and Fe 5 C 2 formation, enhancing the C 2–5 olefin selectivity. Compared with the Pt active sites in K–Pt 1 /Fe 17 Mn 2 /Al 2 O 3 , which was prepared by first supporting Fe–Mn oxide on Al 2 O 3 followed by Pt, those in K–Fe 17 Mn 2 /Pt 1 /Al 2 O 3 existed around the Fe–Mn active sites. Pt continued to contribute to the Fe species reduction and the stable supply of CO, leading to improved C 2–5 olefin selectivity. ● K-doped Fe–Mn–Pt catalysts which function under 1 MPa conditions were developed for CO 2 hydrogenation to C 2–5 olefins. ● K–Fe 17 Mn 2 /Pt 1 /Al 2 O 3 , in which Pt was supported first, achieved the best C 2–5 olefin selectivity (28 %). ● Pt promoted the reverse water-gas shift reaction, and in combination with Mn, facilitated iron oxide reduction and Fe 5 C 2 formation. ● K–Pt 1 /Fe 17 Mn 2 /Al 2 O 3 , in which Pt was supported later, showed lower C 2–5 olefin selectivity (19 %) than K–Fe 17 Mn 2 /Pt 1 /Al 2 O 3 .