Kinetics, Mass Transfer, and Reactor Scaling Up in Production of Direct Dimethyl Ether

Abstract

A two-phase model was developed for scaling up bubbling fluidized bed reactors for dimethyl ether production. Kinetic model correlations for the reactions were developed from fixed-bed experimental data. In addition, the mass transfer coefficient between the bubble and emulsion phases in a bubbling fluidized bed was estimated from experimental data, and the Sherwood number correlation was reported. Finally, scaling up of a bubbling fluidized bed reactor from laboratory to industrial scale was carried out using three similarity criteria: hydrodynamic, residence time, and performance. The hydrodynamic similarity criterion was shown to be inadequate due to low mass transfer and residence time on a large scale. The criteria of similarities in performance and residence time provide the same dimethyl ether yield in all scales. The two-phase models, combined with correlations developed for kinetic and mass transfer parameters, are useful for analysis of laboratory and industrial-scale reactors, and provide information on scaling up.

Present and Future Perspectives of Liquid-Phase Slurry Processes Involved in Methanol and Dimethyl Ether Synthesis Using Biomass-Derived Syngas

“…Although it is advantageous to have some CO 2 in the feed gas to minimize selectivity toward carbonaceous side products and to enhance the conversion of syngas to methanol, CO 2 removal is necessary to prevent poor reaction kinetics and subsequent equilibrium conversion and lead toward faster catalyst deactivation as a result of enhanced sintering processes. 62,63 Hence, excess CO 2 is removed to achieve an optimum stoichiometric number (SN) of ≥2 and a carbon/oxide ratio (COR), a ratio between CO 2 and CO, below 0.6 in the syngas feed by implementing different separation technologies, i.e., absorption, membranes, adsorption, cryogenic distillation, etc. The overall methanol production from syngas is an exothermic reaction, and it becomes difficult to keep the catalyst active and functional at such a high pressure (∼10 MPa) and temperature (∼450 °C).…”

Kinetic Measurement and Modeling of a Slow-Rate Diazo Coupling Reaction

“…The reaction rate of the diazo coupling between 2-naphthol and HNSD is quite slow compared to the other diazo coupling reactions. Despite the high chemical activity of diazo ions, this reaction needs to be carried out at temperatures higher than 303 K in industry; therefore, the decomposition of the diazo salt should be taken into consideration for the production of such type dyes, and the kinetic study is of great importance for achieving the best balance point between production efficiency and product selectivity. − …”