Simulation of Reactors under Different Thermal Regimes and Study of the Internal Diffusional Limitation in a Fixed-Bed Reactor for the Direct Synthesis of Dimethyl Ether from a CO₂-Rich Input Mixture and H₂

Abstract

This paper presents the simulation of reactors under different thermal regimes using the most used kinetic models for the simulation of the direct synthesis of DME with the objective of optimizing the coupling between heat and mass transfer. A pseudo-homogeneous and a heterogeneous plug-flow model are developed to simulate isothermal, adiabatic, and isoperibolic fixed-bed (shell-and-tube) reactors for the direct synthesis of DME from CO 2 and H 2 , enabling the analysis of the limitations by the internal mass transfer. Concentrations, reaction rates, and temperature gradients within the catalyst are assessed. Catalytic efficiency factors are calculated and represented along the reactor tube. The results show that the choice of the kinetic model is crucial for optimal coupling of these functions since it strongly influences the design and sizing of the reactor for synthesis of DME from CO 2 -rich feedstocks. Therefore, this analysis demonstrates that the direct synthesis of DME can be limited by internal mass transfer, which promotes the DME synthesis at low conversions, therefore requiring particular attention for future reactor optimization.

Kinetic Modeling of the Direct Dimethyl Ether (DME) Synthesis over Hybrid Multi-Site Catalysts

“…It is important to note that the kinetic expressions of reaction rates (present in Equation ( 15)) incorporate temperature-dependent equilibrium, kinetic, and adsorption constants. While the former can be derived from the existing literature, being only subject to the thermodynamics of the reactions involved (see Table 1) [48], the latter two constants are specific to the developed catalyst and require experimental data regression for determination. More precisely, the Arrhenius and Van 't Hoff equations express their temperature dependence and were reparametrized (see Equations ( 18) and ( 19)) to improve numerical stability in fitting and decrease numerical correlation between estimated parameters [49,50]:…”

CO2 to dimethyl ether (DME): structural and functional insights of hybrid catalysts

“…Although the formation of catalyst particles >1 mm can avoid high-pressure drops, the limitations of inter-particle mass transfer and heat transport are preventable. 175 As a result, the preferential circulation of gases around the reactor wall results in concentration and temperature gradients and plug-flow deviations. Furthermore, the formation of longitudinal temperature profiles leads to the sintering of catalyst particles and hotspot phenomena.…”

Prospect of Direct Dimethyl Ether Production from CO2: Reactor Design Development

“…The methanol synthesis takes place in the first reactor where syngas, H2 will react with CO and CO2 in the appearance of a copper-based catalyst according to the stoichiometric reaction (Eq (1) and Eq (2)) to form methanol. Due to the existence of H2O in the second reaction, the water gas shift (WGS) reaction is also involved if CO2 [9].…”

“…By integrating the selective membrane in the catalytic reactor, the system is known as catalytic membrane reactor. Figure 9 shows the reactor configuration for catalytic membrane reactor where a H2O permselective membrane is used to facilitate the removal of water with the assistance of sweep gas [9]. Generally, the location of membrane and catalyst are placed co-axially and in a packed bed, respectively.…”