Modeling and kinetic analysis of CO2 hydrogenation using a Mn and K-promoted Fe catalyst in a fixed-bed reactor

• CO2 hydrogenation in different reactor environments is compared.
• Product yield was 49% higher in a fixed-bed reactor at low GHSV.
• Modeling and kinetic analysis determined FT reaction rate slower than the RWGS reaction rate.
• Model predicts water formation plays a role in CO2 conversion and product yield.

Hydrogenation of CO2 to hydrocarbons is investigated over γ-alumina-supported modified iron-based catalysts under fixed-bed reactor conditions to produce unsaturated hydrocarbons as feedstock chemicals for jet-fuel synthesis. The results are compared to those obtained in a continuously stirred tank/thermal reactor (CSTR) environment. It is shown that the maximum C2–C5+ yield obtained in the fixed-bed experiments is 49% higher than those obtained by CSTR at lower gas hourly space velocity (GHSV) of 0.000093 liters per second gram (L/s-g). However, at much higher GHSV (0.0015 L/s-g), C2–C5+ yield is reduced by 47% in the fixed-bed environment. Modeling and kinetic analysis of the data obtained under fixed-bed reactor conditions is expanded upon by including the formation of methane as a by-product and providing kinetic constants. The results show that our Fischer–Tropsch (FT) reaction rate is much slower than the reverse water gas shift (RWGS) reaction rate. Therefore the FT reaction becomes the rate-controlling step in overall conversion of CO2 to olefins. The model was further expanded to show the potential beneficial effects of water removal from the reactor on CO2 conversion and product yield.

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