Equilibrium calculations for direct synthesis of dimethyl ether from syngas

Abstract

Thermodynamic analysis of single-step synthesis of dimethyl ether (DME) from syngas over a bi-functional catalyst (BFC) in a slurry bed reactor has been investigated as a function of temperature (200-240 • C), pressure (20-50 bar), and composition feed ratio (H 2 /CO: 1-2). The BFC was prepared by physical mixing of CuO/ZnO/Al 2 O 3 as a methanol synthesis catalyst and H-ZSM-5 as a methanol dehydration catalyst. The three reactions including methanol synthesis from CO and H 2 , methanol dehydration to DME and water-gas shift reaction were chosen as the independent reactions. The equilibrium thermodynamic analysis includes a theoretical model predicting the behaviour and a comparison to experimental results. Theoretical model calculations of thermodynamic equilibrium constants of the reactions and equilibrium composition of all components at different reaction temperature, pressure, and H 2 /CO ratio in feed are in good accordance with experimental values.L'analyse thermodynamique de la synthèse en uneétape du méthoxyméthane du gaz de synthèse sur un catalyseur bifonctionnel dans un réacteur a lit bouillonnant aétéétudiée comme une fonction de température (200à 240 •C), de pression (20à 50 bars) et de rapport d'alimentation compositionnel (H2/CO: 1-2). Le catalyseur bifonctionnelétait préparé par un mélange physique de CuO/ZnO/Al2O3 comme un catalyseur de synthèse de méthanol et de H-ZSM-5 comme un catalyseur de déshydratation du méthanol. Les trois réactions, soit la synthèse du méthanol du CO et du H2, la déshydratation du méthanol en méthoxyméthane et la conversion catalytique, ontété choisies comme réactions indépendantes. L'analyse thermodynamique de l'équilibre comprend un modèle théorique qui prédit le comportement et une comparaison par rapport aux résultats expérimentaux. Les calculs du modèle théorique des constantes de l'équilibre thermodynamique des réactions et la composition d'équilibre de tous les composantsà différentes températures de réaction, différentes pressions et un différent rapport H2/CO dans l'alimentation cadrent bien avec les valeurs expérimentales.

Direct dimethyl ether synthesis from syngas on copper–zeolite hybrid catalysts with a wide range of zeolite particle sizes

“…This indicates much slower methanol dehydration on the catalysts 6 containing larger zeolite particles which probably arises due to the mass transfer limitations. 7 Our results suggest that in addition to the size for individual zeolite crystallites, the presence 8 of zeolite agglomerates may also significantly affect the rate of catalysts reactions in 9 bifunctional catalysts. Indeed, the rate of diffusion seems to be limited not by individual 10 zeolite crystallite sizes but by the diameter of zeolite intergrown agglomerates.…”

“…7) and constant temperature (70 ˚C). The 7 suspension was continuously stirred and kept at the desired pH by adjustment of the relative 8 flow rates of the two solutions. The final suspension was aged under stirring at 70 ˚C for 1 h. 9…”

Semicontinuous separation of dimethyl ether (DME) produced from biomass

“…[3][4][5] The versatility of DME makes it a highly competitive alternative fuel. [12,13] In the direct synthesis method, methanol synthesis and dehydration occur simultaneously over bi-functional catalysts in one reactor. [1] Since biomass has a low energy density and is distributed in nature, large-scale production facilities require collection over a large area, increasing transportation costs.…”

“…[11] Typically, DME is produced via the indirect method, which consists of methanol synthesis from syngas followed by methanol dehydration to form DME. [12,13] In the direct synthesis method, methanol synthesis and dehydration occur simultaneously over bi-functional catalysts in one reactor. This lessens the thermodynamic limitations of the methanol synthesis step alone, achieving higher conversion efficiency than the indirect process in addition to lower investment costs.…”

Modeling of Slurry Bubble‐Column Reactors with Emphasis on the Importance of Bubble Size Estimation

“…9. A higher H 2 /CO ratio is not favored for the water‐gas shift reaction, but since the reaction order for the methanol synthesis is 2 and for water gas shift is 1 75, by increasing the H 2 /CO ratio from 1 to 2, methanol synthesis reaction is accelerated and higher CO conversion is achieved.…”