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Kinetic Modeling of the Direct Dimethyl Ether (DME) Synthesis over Hybrid Multi-Site Catalysts
oleh: Antonio D’Ambrosio, Alice Bertino, Serena Todaro, Mariarita Santoro, Catia Cannilla, Francesco Frusteri, Giuseppe Bonura, Leone Mazzeo, Vincenzo Piemonte
Format: | Article |
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Diterbitkan: | MDPI AG 2024-01-01 |
Deskripsi
This paper deals with the proposition of a kinetic model for the direct synthesis of DME via CO<sub>2</sub> hydrogenation in view of the necessary optimization of the catalytic system, reactor design, and process strategy. Despite the fact that DME synthesis is typically treated as a mere combination of two separated catalytic steps (i.e., methanol synthesis and methanol dehydration), the model analysis is now proposed by taking into account the improvements related to the process running over a hybrid catalyst in a rational integration of the two catalytic steps, with boundary conditions properly assumed from the thermodynamics of direct DME synthesis. Specifically, the CO<sub>2</sub> activation step at the metal–oxide interface in the presence of ZrO<sub>2</sub> has been described for the first time through the introduction of an ad hoc mechanism based on solid assumptions from inherent studies in the literature. The kinetic modeling was investigated in a tubular fixed-bed reactor operating from 200 to 260 °C between 1 and 50 bar as a function of a gas hourly space velocity ranging from 2500 to 60,000 NL/kg<sub>cat</sub>/h, in a stoichiometric CO<sub>2</sub>/H<sub>2</sub> feed mixture of 1:3 <i>v</i>/<i>v</i>. A well-detailed elementary mechanism was used to predict the CO<sub>2</sub> conversion rate and identify the key reaction pathways, starting with the analysis of the implicated reactions and corresponding kinetic mechanisms and expressions, and finally estimating the main parameters based on an appropriate modeling of test conditions.