Dehydration of methanol to dimethyl ether (DME): Performance of three types of catalyst at atmospheric pressure

Abstract

A research on the production of dimethyl ether (DME) at lower pressure has been conducted in related to the national program on the partial substitution of LPG with DME in the near future (RUEN 2017). DME may be liquefied at a pressure of about 6 atm (25°C), or a temperature of -25°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°C. The experiment was conducted in a tubular reactor with a diameter of 20 mm. and three types of catalyst, i.e. g-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 m2/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 was 0.02 mol/L, 0.05 or 0.07 mol/L. It was found that g-Al2O3 catalyst had a better activity than the two commercial catalysts. A stable conversion of methanol of 72% was obtained on g-Al2O3 catalyst for the 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.