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Aschauer, Stephan Josef ; Schilder, Lisa ; Pöhlmann, Ferdinand ; Moos, Ralf ; Schönauer-Kamin, Daniela ; Jess, Andreas:
Solubility of 1-olefins, 2-olefins, n-paraffins and iso-paraffins in Lewis acidic chloroaluminate ionic liquids (BMIM-AlCl4).
2011
Veranstaltung: ECCE 2011 : 8th European Congress of Chemical Engineering
, 25. - 29.09.2011
, Berlin.
(Veranstaltungsbeitrag: Kongress/Konferenz/Symposium/Tagung
,
Poster
)
Abstract
In the alkylation process of light olefins with isobutane, the solubility of the feedolefins in the acid catalyst is one of the most crucial physical properties. The reaction, which is technically established since 1940, is carried out with HF or H2SO4 as catalyst. A high olefin solubility in the catalyst phase compared to isobutane leads to oligimerisation and consecutive cracking reactions. Therefore, the isobutane/olefin ratio has to be kept high (15-20:1) to guarantee a good gasoline product (major C8- TMP) and to avoid undesired heavy components (C9+). Due to several disadvantages of the industrial catalysts like toxicity (HF), volatility and corrosiveness, or high consumption during the process (H2SO4) many attempts have been made to replace both acids.
One very promising alternative is to use highly Lewis-acidic ionic liquids. But in contrast to HF/H2SO4-systems, the solubility of the feed-olefins and the products in Lewis-acidic ionic liquids have not been reported in literature yet. In order to understand product-distributions of batch and continuous alkylation and to describe reaction kinetics, the solubility of 1-olefins (C5-C8,C12), 2-olefins (C5-C8), nparaffins (C5-C12) and iso-paraffins (2,2,4-Trimethylpentane, Isopentane, Isohexane) were measured in the ionic liquid 1-butyl-3-methylimidazolium-tetrachloroaluminte ([BMIM][AlCl4]) with different Lewis-acidity by extraction/re-extraction technique. To explain the measured values and to correlate them with the chainlength of the alkyl sidechain, the static dielectric constant and the viscosity of both reaction system components (catalyst and hydrocarbon) are measured. While the static dielectric constant is proven to describe the solution behaviour in a wide range of polar and non-polar solvents, this has been not completely accepted for ionic liquids. Because of the enormous number of possible ionic liquids by varying the cations and anions it is unlikely to describe the solubility just by one parameter. Therefore, the measured solubility is explained by the frequency dependent dielectric constant and the viscosity of the catalysts and hydrocarbons.