Kinetic modeling of CO2 + CO hydrogenation to DME over a CuO-ZnO-ZrO2@SAPO-11 core-shell catalyst

Abstract

A kinetic model for the CO2 + CO hydrogenation to dimethyl ether (DME) in a single step over an original core-shell structured CuO-ZnO-ZrO2@SAPO-11 bifunctional catalyst (metallic in the core and acid in shell) has been established. The catalytic runs have been carried out in an isothermal fixed bed reactor under the following conditions: 250-320 ºC; 10-50 bar; space time, 1.25-15 gcat·h·molC-1; H2/COx molar fraction in the feed, 2.5-4, and CO2/COx, 0-1. The catalyst has a high activity and stability as a result of the separation of reactions in the two functions.The model describes the effect of the operating conditions (temperature, pressure and feed composition) over the evolution of product distribution with time on stream. For this, the individual reactions (CO2 and CO hydrogenation to methanol, its dehydration to DME, the WGS reaction and the side reaction of hydrocarbons formation) are considered together with catalyst deactivation. Using the model, simulation studies allow for establishing suitable operating conditions (305 ºC,70 bar, CO2/COx of 0.75 and H2/COx of 3) to attain a good compromise between DME yield and CO2 conversion, reaching a value of 23 % for both objectives.