ABSTRACT
KINETIC STUDIES FOR THE PRODUCTION OF TERTIARY ETHERS USED AS GASOLINE ADDITIVES
Boz, Nezahat
Ph. D., Department of Chemical Engineering
Supervisor: Prof. Dr. Timur Dogu
Co-supervisor: Prof. Dr. Gü / lSen Dogu
June 2004, 174 pages
In the present study, the kinetics studies for etherification reactions were investigated in detail.
In the first phase of present study, different acidic resin catalysts were prepared by the heat treatment of Amberlyst-15 catalysts at 220° / C at different durations of time and also by the synthesis of sulfonated styrene divinylbenzene cross-linked resins at different conditions. A linear dependence of reaction rate on hydrogen ion-exchange capacity was in 2M2B+ethanol reaction. However, in the case of 2M1B+ethanol reaction hydrogen ion-exchange capacities over 2.8 meq.H+/g did not cause further increase in reaction rate, which was concluded to be majorly due to significance of diffusional resistances.
DRIFTS experiments carried out with alcohols, isobutylene, isoamylenes and TAME (tert-amyl-methyl-ether) in a temperature range of 333-353 K supported a Langmuir-Hinshelwood type reaction mechanism involving adsorbed isoolefins molecules forming a bridged structure between &ndash / SO3H sites of the catalyst and adsorbed alcohol molecules. A rate expression derived basing on the mechanism proposed from the DRIFTS results gave good agreement with the published data. Reaction rate was found to give a sharp maximum at ethanol activity of around 0.1.
The third phase of this work included evaluation of effective diffusivities and adsorption equilibrium constants of methanol, ethanol and 2M2B, in Amberlyst-15 from moment analysis of batch adsorber dynamic results. Models proposed for monodisperse and bidisperse pore structures were used for the evaluation of effective diffusivities. It was shown that surface diffusion contribution was quite significant.
In the last phase of the work, a batch Reflux-Recycle-Reactor (RRR) was proposed, modeled and constructed to achieve high yields and selectivities in equilibrium limited reactions.
The batch reflux recycle reactor was modeled by assuming plug flow in the reactor section, perfect mixing in the reboiler and vapor-liquid equilibria between the liquid in the reboiler and reactor inlet stream. In this system conversion values of isoamylenes reaching to 0.91 were achieved at 82° / C with almost 100% selectivity. Such conversion values were shown to be much higher than the corresponding equilibrium values that could be obtained in vapor phase fixed bed reactors. The activation energies evaluated in this system were found to be much less than the activation energies evaluated in the fixed bed reactor studies. This was concluded to be majorly due to the significance of transport resistant in the batch Reflux-Recycle-Reactor in which catalyst particles are partially wet.
As a result of catalyst development, characterization, kinetic and reactor development studies carried out in this study, it was concluded that tert-amyl-ethyl-ether (TAEE) could be effectively produced and used as a gasoline blending oxygenate.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12605039/index.pdf |
| Date | 01 June 2004 |
| Creators | Boz, Nezahat |
| Contributors | Dogu, Timur |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | Ph.D. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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