Dual-Cycle Mechanism Based Kinetic Model for DME-to-Olefin Synthesis on HZSM-5-Type Catalysts

Abstract

A kinetic model for the olefins synthesis from dimethyl ether on zeolite HZSM-5 based catalysts is developed. The model includes the reaction pathways for the synthesis of olefins from oxygenates in the olefinic and aromatic cycles according to modern concepts of the dual-cycle reaction mechanism. The kinetic parameters were determined for the time-stable hydrothermally treated catalysts of various activities Mg-HZSM-5/Al2O3, HZSM-5/Al2O3, and Zr-HZSM-5/Al2O3. The kinetic parameters determination and the solution of the ordinary differential equations system were carried out in the Python software environment. The preliminary estimation of the kinetic parameters was carried out using the Levenberg-Marquardt algorithm, and the parameters were refined using the genetic algorithm. It is shown that reactions activation energies for different catalysts are close, which indicates that the priority of the reaction paths on the studied catalysts is the same. Thus, the topology of the zeolite plays a leading role in the determination of the synthesis routes, rather than the nature of the modifying metal. The developed model fits the experimental data obtained in an isothermal reactor in the range of temperature 320–360 °C, specified contact time 0.1–3.6 h*gcat/gC with a relative error of less than 15%.

Improvement of n-Butene Yield in Dimethyl Ether-to-Olefin Reaction Using Ferrierite Zeolite Catalysts

“…The activation energies for olefin methylation reactions with DME are in the order ethylene > propylene > butene > pentene [49]. This indicates that an appropriate balance between the butene production rate and disappearance rate is required.…”

“…A dual cycle model has been previously proposed as the mechanism for the DTO reaction [48,49]. Based on the literature, a model for the DTO reaction mechanism is shown in Figure 5.…”