From laboratory experiments to simulation studies of methanol dehydration to produce dimethyl ether reaction—Part II: Simulation and cost estimation (original) (raw)
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Catalytic and kinetic study of methanol dehydration to dimethyl ether
Chemical Engineering Research and Design, 2012
Dimethyl ether (DME), as a solution to environmental pollution and diminishing energy supplies, can be synthesized more efficiently, compared to conventional methods, using a catalytic distillation column for methanol dehydration to DME over an active and selective catalyst. In current work, using an autoclave batch reactor, a variety of commercial catalysts are investigated to find a proper catalyst for this reaction at 110-135 °C and 900 kPa. Among the γ-Alumina, Zeolites (HY, HZSM-5 and HM) and ion exchange resins (Amberlyst 15, Amberlyst 35, Amberlyst 36 and Amberlyst 70), Amberlyst 35 and 36 demonstrate good activity for the studied reaction at the desired temperature and pressure. Then, the kinetics of the reaction over Amberlyst 35 is determined. The experimental data are described well by Langmuir-Hinshelwood kinetic expression, for which the surface reaction is the rate determining step. The calculated apparent activation energy for this study is 98 kJ/mol.
2019
A research on the production of dimethyl ether (DME) at lower pressure has been conducted in related to the national program on partial substitution of LPG with DME in the near future (RUEN 2017). DME may be liquefied at a pressure of about 6 atm (25 o C), or a temperature of-25 o C (1 bar). Burning of DME may produce a cleaner flue gas than LPG. Experiments on dehydration of methanol to produce DME were carried out at a atmospheric pressure (1 bar) and a temperature of 240 o C. The experiment was conducted in a tubular reactor with a diameter of 20 mm. and three types of catalyst, i.e. -Al2O3 (from our laboratory), and two commercial catalysts namely catalyst A and catalyst B. The γ-Al2O3 catalyst had a surface area of 194.4 m 2 /gram, an average pore diameter of 11.2 nm, and a total pore volume of 0.546 mL/gram. Methanol concentration in the influent of the reactor were 0.02 mol/L, 0.05 or 0.07 mol/L. It was found that -Al2O3 catalyst had a better activity than the two commercial catalysts. A stable conversion of methanol of 72% was obtained on -Al2O3 catalyst for on stream time of 6 to 10 hour. Kinetics of dehydration of methanol to DME on γ-Al2O3 catalyst could be represented as a first order reaction with an activation energy Ea of 256.6 kJ/mol and a frequency factor ko of 8·10 +28 .
Fuel, 2008
Catalytic dehydration of methanol to dimethyl ether (DME) is performed in an adiabatic fixed bed heterogeneous reactor by using acidic c-alumina. By changing the mean average temperature of the catalyst bed (or operating temperature of the reactor) from 233 up to 303°C, changes in methanol conversion were monitored. The results showed that the conversion of methanol strongly depended on the reactor operating temperature. Also, conversion of pure methanol and mixture of methanol and water versus time were studied and the effect of water on deactivation of the catalyst was investigated. The results revealed that when pure methanol was used as the process feed, the catalyst deactivation occurred very slowly. But, by adding water to the feed methanol, the deactivation of the c-alumina was increased very rapidly; so much that, by increasing water content to 20 weight percent by weight, the catalyst lost its activity by about 12.5 folds more than in the process with pure methanol. Finally, a temperature dependent model developed to predict pure methanol conversion to DME correlates reasonably well with experimental data.
Effect of precursor on the performance of alumina for the dehydration of methanol to dimethyl ether
Dimethyl ether (DME) is amongst one of the most promising alternative, renewable and clean fuels being considered as a future energy carrier. In this study, the comparative catalytic performance of-Al 2 O 3 prepared from two common precursors (aluminum nitrate (AN) and aluminum chloride (AC)) is presented. The impact of calcination temperature was evaluated in order to optimize both the precursor and pre-treatment conditions for the production of DME from methanol in a fixed bed reactor. The catalysts were characterized by TGA, XRD, BET and TPD-pyridine. Under reaction conditions where the temperature ranged from 180 • C to 300 • C with a WHSV = 12.1 h −1 it was found that all the catalysts prepared from AN(-Al 2 O 3) showed higher activity, at all calcination temperatures, than those prepared from AC(-Al 2 O 3). In this study the optimum catalyst was produced from AN and calcined at 550 • C. This catalyst showed a high degree of stability and had double the activity of the commercial-Al 2 O 3 or 87% of the activity of commercial ZSM-5(80) at 250 • C.
Korean Journal of Chemical Engineering, 2010
The kinetic behavior of a commercial γ-Al 2 O 3 catalyst for the methanol to dimethyl ether (DME) dehydration reaction has been investigated using a differential fixed bed reactor at the pressure range 1-16 barg within a temperature range of 260-380 o C. The experimental runs were performed in a wide range of feed to water ratios. The experiments were designed by general full factorial design (GEFD) and a novel rate equation has been developed which exhibited the best fitting with our experimental data. Based on the analysis of variance (ANOVA), the following order of importance for operating conditions was obtained when the objective function is the yield of DME: Temperature>Water % in feed>Pressure. In addition, the optimum operating conditions for the maximum yield of DME, were found at T= 380 o C, P=16 barg and zero wt% of water in the feed.
Catalytic dehydration of methanol to dimethyl ether (DME) over Al-HMS catalysts
Journal of Industrial and Engineering Chemistry, 2014
A series of Al-HMS with different Si/Al ratio was used as a solid acid catalyst for methanol dehydration to dimethyl ether (DME). The effect of temperature, feed composition, space velocity, and the catalyst Si/Al ratio on the catalytic dehydration of methanol was investigated. By decreasing Si/Al, the temperature required to reach equilibrium conversion of methanol decreased due to the increased number of acidic sites. Compared to commercial g-Al 2 O 3 , Al-HMS-5 and Al-HMS-10, catalysts exhibited a high yield of DME. Among all Al-HMS catalysts, Al-HMS-10 exhibited an optimum yield of 89% with 100% selectivity and excellent stability for methanol dehydration to DME.
Energy Sources, Part A: Recovery, Utilization, and Environmental Effects
In this research a one-dimensional mathematical model was developed to investigate the effects of inlet temperature, pressure, and feed flow rate on an adiabatic fixed bed reactor over Na-HZSM5 catalyst for dehydration of methanol to dimethyl ether. Results indicated that temperature profile and methanol conversion are mostly affected by inlet temperature. The pressure has no significant effect on methanol conversion. Since the reaction is reversible and exothermic, increasing of inlet temperature shifts equilibrium conversion to low values. Methanol conversion predicted by this model is in good agreement with experimental data.
Kinetic Study of Methanol Dehydration to Dimethyl Ether in Catalytic Packed Bed Reactor over Resin
Journal of Materials Science and Chemical Engineering, 2022
Dimethyl ether (DME) is considered as a significant fuel alternative with a critical manufacturing process. Only a few authors have presented the kinetic analysis of attractive and alternative catalysts to Al 2 O 3 and/or zeolite in DME production, despite the fact that there is a large library of kinetic studies for these commercial catalysts. The purpose of this research was to contribute to this direction by conducting a catalytic test to determine kinetic parameters for methanol dehydration over sulfonic acid catalysts (resin). However, due to the relevance of the mathematical description of this process in the industry was also studied, a study of kinetics parameters and mathematical modeling of methanol dehydration in an atmospheric gas phase in a fixed bed reactor with a temperature range (90˚C-120˚C) was examined. The Langmuir-Hinshelwood (L-H) model provides the best fit to experimental data, with an excellent R 2 = 0.9997, and the experimental results were compared to those predicted by these models with very small deviations. The kinetic parameters were found to be in good agreement with the Arrhenius equation, with acceptable straight-line graphs. The activation energy E was computed and found to be 27.66 kJ/mole, with an average variation of 0.32 percent between the predicted and calculated results. Simple mathematical continuum models (plug flow reactor PFR) showed an acceptable agreement with the experimental data.