Due to the water pollution problems created by MTBE, significant research
was focused on the production of alternative oxygenates, such as ethyl tert-butyl
ether (ETBE), tert-amyl-methyl-ether (TAME) and tert-amyl-ethyl-ether (TAEE)
as octane enhancing gasoline blending components. These oxygenates are
expected to improve the burning characteristics of gasoline and reduce exhaust
emissions of CO and hydrocarbons. Generally, macroreticular acidic resin
catalysts (Amberlyst-15) are used for the etherification reactions between C5
iso-olefins (2M1B/2M2B) and alcohols (ethanol/methanol). But in recent years,
heteropoly acid compounds are being used in the production of tert-ethers to
replace those macroreticular acidic resin catalysts. HPAs are known to be active
catalysts for many of homogeneous and heterogeneous acid catalyzed reactions.These compounds have high acidity, high catalytic activity but they are highly
soluble in polar solvents such as water,alcohol when they are used in bulk form.
In this research, applicability of bulk heteropoly acid (HPA) and its
supported form, to the gas-phase etherification reaction of iso-olefin (2-methyl-
2-butene) with ethyl alcohol in a continuous differential reactor was investigated.
The heteropoly acid (H3PW12O40.xH2O) was supported on activated carbon, at
two different loading levels, by aqueous impregnation technique. After catalyst
characterization, kinetic experiments were done in a temperature range between
80° / C-97° / C with a feed concentration of 30 vol.%2M2B+70 vol.% ethanol.
Supported HPA catalysts yielded lower conversion and rate of reaction than the
bulk HPA. After that, to make a comparison, same experiments have been
carried out with Amberlyst-15 and a different HPA (H3PMo12O40.xH2O) at 90oC.
The results showed that, at this temperature, bulk tungstophosphoric acid
(H3PW12O40.xH2O) was highly active among the other catalysts. Moreover, the
deactivation of bulk and supported HPA were investigated and found that partial
deactivation occurred when they were reused, without any treatment. In the
final part of the study, the activity of alcohol-treated supported HPA catalyst and
formation of side products, dimethyl or diethyl ether, at 90° / C were investigated.
When the supported catalyst was treated with alcohol, before utilizing in the
experiments, lower conversion was obtained with respect to the conversion
value obtained in the presence of fresh catalyst. The studies done on the
formation of side product showed that, no side product was formed at this
working temperature.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/1134923/index.pdf |
| Date | 01 September 2003 |
| Creators | Obali, Zeynep |
| Contributors | Dogu, Timur |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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