Kinetic studies for dimethyl ether and diethyl ether production

Varışlı, Dilek
Fast depletion of oil reserves necessitates the development of novel alternative motor vehicle fuels. Global warming problems also initiated new research to develop new fuels creating less CO2 emission. Nowadays, dimethyl ether (DME) and diethyl ether (DEE) are considered as important alternative clean energy sources. These valuable ethers are produced by the dehydration reaction of methanol and ethanol, respectively, in the presence of acidic catalysts. Besides DEE, ethylene which is very important in petrochemical industry, can also be produced by ethanol dehydration reaction. In the first part of this study, the catalytic activity of tungstophosphoric acid (TPA), silicotungstic acid (STA) and molybdophosphoric acid (MPA), which are well-known heteropolyacids were tested in ethanol dehydration reaction. The activities of other solid acid catalysts, such as Nafion and mesoporous aluminosilicate, were also tested in the dehydration reaction of ethanol. In the case of DME production by dehydration of methanol, activities of STA, TPA and aluminosilicate catalysts were tested. Among the heteropolyacid catalysts, STA showed the highest activity in both ethanol and methanol dehydration reactions. With an increase of temperature from 180oC to 250oC, Ethylene selectivities increased while DEE selectivities decreased. Ethylene yield values over 0.70 were obtained at 250oC. The presence of water in the feed stream caused some reduction in the activity of TPA catalyst. Very high DME yields were obtained using mesoporous aluminosilicate catalyst at about 450oC. The surface area of heteropolyacids are very low and they are soluble in polar solvents such as water and alcohols. Considering these drawbacks of heteropolyacid catalysts, novel mesoporous STA based high surface area catalysts were synthesized following a hydrothermal synthesis route. These novel catalysts were highly stable and they did not dissolve in polar solvents. The catalysts containing W/Si ratios of 0.19 (STA62(550)) and 0.34 (STA82(550)) have BJH surface area values of 481 m2/g and 210 m2/g, respectively, with pore size distributions ranging in between 2-15 nm. These catalysts were characterized by XRD, EDS, SEM, TGA, DTA, DSC, FTIR and Nitrogen Adsorption techniques and their activities were tested in ethanol dehydration reaction. Calcination temperature of the catalysts was shown to be a very important parameter for the activities of these catalysts. Considering the partial decomposition and proton lost of the catalysts over 375oC, they are calcined at 350oC and 550oC before testing them in ethanol dehydration reaction. The catalysts calcined at 350oC showed much higher activity at temperature as low as 180oC. However, the catalysts calcined at 550oC showed activity over 280oC. Ethylene yield values approaching to 0.90 were obtained at about 350oC with catalysts calcined at 350oC. DEE yield past through a maximum with an increase in temperature indicating its decomposition to Ethylene at higher temperatures. However, at lower temperatures (<300oC) Ethylene and DEE were concluded to be formed through parallel routes. Formation of some acetaldehyde at lower temperatures indicated a possible reaction path through acetaldehyde in the formation of DEE. DRIFTS results also proved the presence of ethoxy, acetate and ethyl like species in addition to adsorbed ethanol molecules on the


Direct synthesis of dimethyl ether (dme) from synthesis gas using novel catalysts
Arınan, Ayça; Varışlı, Dilek; Department of Chemical Engineering (2010)
Increasing prices of crude oil derived transportation fuels ascended the researches on seeking alternative fuels, in last decades. Moreover, the increasing rate of global warming, because of high greenhouse gas emissions initiated new research for environment-friendly clean alternative fuels. Due to its low NOx emission, good burning characteristics and high cetane number, dimethyl ether (DME) attracted major attention as a transportation fuel alternative. Two possible pathways have been proposed for DME pr...
Nanocomposite nafion and heteropolyacid incorporated mesoporous catalysts for dimethyl ether synthesis from methanol
Çiftçi, Ayşegül; Doğu, Timur; Department of Chemical Engineering (2009)
The need for alternative transportation fuels is rising with the rapid depletion of oil reserves and the simultaneous growth of the world’s population. Production of dimethyl ether, a non-petroleum derived attractive fuel-alternate for the future, is a challenging research area. Different routes and various solid-acid catalysts are being developed in order to achieve the most efficient way of synthesizing this potential diesel alternative fuel. The focus of heterogeneous catalysis is to convert renewable fe...
Synthesis of some metalophthalocyanines and their effects on the performance of pem fuel cells
Erkan, Serdar; Eroğlu, İnci; Department of Chemical Engineering (2005)
Importance of clean, sustainable and renewable energy sources are increasing gradually because of either being environmental friendly or being alternative for fossil fuels. Hydrogen energy system will let the utilization of alternative energy sources. Fuel cells are the most suitable energy conversion devices while passing through the hydrogen economy. The cost of the fuel cell systems need to be reduced in order to achieve commercialization of these systems. One of the most important cost items is platinum...
Steam reforming of ethanol for hydrogen production using Cu-MCM41 and Ni-MCM41 type mesoporous catalytic materials
Özdoğan, Ekin; Doğu, Timur; Department of Chemical Engineering (2007)
The world’s being alerted to the global warming danger and the depletion of fossil fuel resources, has increased the importance of the clean and renewable hydrogen energy. Bioethanol has high potential to be used as a resource of hydrogen since it is a non-petroleum feedstock and it is able to produce hydrogen rich mixture by steam reforming reactions. Discovery of mesoporous MCM-41 type high surface area silicate-structured materials with narrow pore size distributions (20-100 Å) and high surface areas (up...
Sorption enhanced ethanol reforming over cobalt, nickel incorporated mcm-41 for hydrogen production
Gündüz, Seval; Doğu, Timur; Department of Chemical Engineering (2011)
The interest in hydrogen as a clean energy source has increased due to depletion of limited fossil resources and environmental impact related to CO2 emissions. Hydrogen production from bio-ethanol, which already contains large amount of water, by steam reforming reaction, has shown excellent potential with CO2 neutrality. However, steam reforming of ethanol reaction is a highly complex process including many side reactions which decrease hydrogen yield and have a negative effect on process economy. Also, th...
Citation Formats
D. Varışlı, “Kinetic studies for dimethyl ether and diethyl ether production,” Ph.D. - Doctoral Program, Middle East Technical University, 2007.