Exploring the impact of cobalt and H₂ to CO ratios on catalytic performance of FeKAl and FeCoKAl catalysts in CO hydrogenation to light olefins

Abstract

This study explores the CO hydrogenation to light olefins over FeKAl catalysts, examining how varying H₂ to CO ratios (from 1:1 to 7:1) and the introduction of cobalt (Co) influence catalytic performance. Our investigation reveals that Co addition significantly enhances the reducibility of iron oxide species and increases sites favorable for moderate hydrogen adsorption and weak to moderate basicity. We discovered that without Co (FeKAl), increasing the H₂ to CO ratio progressively lowers CO₂ space–time yield (STY), shifting the reaction's preference from the water–gas shift reaction towards hydrogenation. The STY of light olefins reaches a peak at an H₂ to CO ratio of 3:1, indicating optimal conditions for their production before decreasing at higher ratios. Incorporation of Co (FeCoKAl) maintains this trend but with marked improvements in CO conversion and olefin STY, especially notable at a ratio of 1:1 due to enhanced hydrocarbon product desorption. The findings underscore the critical role of Co and H₂ to CO ratios in modulating catalyst stability and activity, with specific ratios significantly reducing catalyst deactivation through diminished wax and carbon fiber formation, and Co presence aiding in the maintenance of steady CO₂, hydrocarbon, and light olefin yields by preventing the excessive transformation of iron carbide to Fe₃O₄.