Kinetic Model for the Direct Conversion of CO<sub>2</sub>/CO into Light Olefins over an In<sub>2</sub>O<sub>3</sub>–ZrO<sub>2</sub>/SAPO-34 Tandem Catalyst
Ander Portillo, Onintze Parra, Andrés T. Aguayo, Javier Ereña, Javier Bilbao, Ainara Ateka
Abstract
High Resolution Image Download MS PowerPoint Slide An original kinetic model is proposed for the direct production of light olefins by hydrogenation of CO 2 /CO (CO x ) mixtures over an In 2 O 3 –ZrO 2 /SAPO-34 tandem catalyst, quantifying deactivation by coke. The reaction network comprises 12 individual reactions, and deactivation is quantified with expressions dependent on the concentration of methanol (as coke precursor) and H 2 O and H 2 (as agents attenuating coke formation). The experimental results were obtained in a fixed-bed reactor under the following conditions: In 2 O 3 –ZrO 2 /SAPO-34 mass ratio, 0/1–1/0; 350–425 °C; 20–50 bar; H 2 /CO x ratio, 1–3; CO 2 /CO x ratio, 0–1; space time, 0–10 g In2O3–ZrO2 h mol C –1, 0–20 g SAPO-34 h mol C –1; time, up to 500 h; H 2 O and CH 3 OH in the feed, up to 5% vol. The utility of the model for further scale-up studies is demonstrated by its application in optimizing the process variables (temperature, pressure, and CO 2 /CO x ratio). The model predicts an olefin yield higher than 7% (selectivity above 60%), a CO x conversion of 12% and a CO 2 conversion of 16% at 415 °C and 50 bar, for a CO 2 /CO x = 0.5 in the feed. Additionally, an analysis of the effect of In 2 O 3 –ZrO 2 and SAPO-34 loading in the configuration of the tandem catalyst is conducted, yielding 17% olefins and complete conversion of CO 2 under full water removal conditions.