Effects of catalyst particle size on methanol dehydration at different temperatures and weight hourly space velocities (original) (raw)
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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.
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 .
Chemical Engineering and Processing: Process Intensification, 2013
Most of the reaction rate equations for methanol dehydration are derived from the experiments conducted for crude methanol as feed and laboratory prepared catalysts, which are not exactly the same as industrial reactors conditions. In the present contribution, it is attempted to find suitable rate of reactions for pure methanol with no water as feed and commercial catalysts of HZSM-5 and ␥-alumina at industrial conditions in methanol dehydration process. In addition, a comparison between the performances of the catalysts is performed. It is found that HZSM-5 has superior performances compared to the ␥-alumina in terms of conversion. Modeling results are also indicated that the proposed rate of reaction predicts the behavior of the process, properly.
Methanol dehydration into dimethyl ether (DME) simulation in fixed bed reactor
THE 2ND INTERNATIONAL SYMPOSIUM OF INDONESIAN CHEMICAL ENGINEERING 2021: Enhancing Innovations and Applications of Chemical Engineering for Accelerating Sustainable Development Goals
Dimethyl ether (DME) production through methanol dehydration has a lot of advantages, such as high DME yield and easier optimization on the operating condition. Therefore, it is necessary to study the impact of reaction parameters such as feed conditions on the reaction. The process of methanol dehydration is naturally accompanied by several side reactions. Usage of γ-alumina catalyst as methanol dehydration catalyst could prevent the side reactions from happening because it is active and selective towards methanol dehydration. Based on the thermodynamic approach, the methanol equilibrium conversion will decrease as the feed temperature increases and feed purity decreases. The simulation of methanol dehydration reaction resulted in a methanol conversion and bed temperature profile along the reactor. Based on the simulation result, methanol conversion will increase as the temperature and feed concentration increase.
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.
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.
New Method for Synthesis Nano Size γ-Al2O3 Catalyst for Dehydration of Methanol to Dimethyl Ether
International Journal of Chemical Engineering and Applications, 2012
Nowadays the importance of nano-particles and their uses in different industries have attracted many researches. The materials in nano-scale show different characteristics in comparison with their bulk state. Nano-materials have potential applications in optoelectronics, catalysis, and membranes. In this paper Nano-size porous γ-alumina was successfully synthesized by precipitation method under ultrasonic vibration mixing. Sonochemistry help the nano particles to synthesis regular form. The synthesized catalyst was characterized by SEM, XRD, BET, and TPD techniques. The effect of two most important operating conditions (i.e. Temperature and WHSV) on performance of this catalyst was investigated for dehydration of methanol to dimethyl ether (DME). The optimum operating condition was at temperature of 320 º C and WHSV of 15 h-1 .
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.