Reaction calorimetric and spectroscopic studies of an ionic liquid synthesis

Ionic Liquids are becoming increasingly interesting as solvents for multiphase and other applications. However, their synthesis in continuous mode at production scale is still challenging, especially for the solvent-free non-catalysed amine quaternisations. The synthesis of 1-ethyl-3-methylimidazolium ethylsulfate by alkylation of N-methylimidazol with diethylsulfate was studied as a representative for reactions with high heat output, strongly changing physical properties and sensitivity towards precise control of process conditions. In order to characterise the reaction thermodynamics, reaction calorimetric experiments were conducted in semi-batch and fed-batch mode. It could be demonstrated that the non-ideality of the reaction system is prohibitive for the application of a simple thermodynamic model neglecting enthalpy contributions from reaction-related changes in mixture composition. Experimentally the latter could not be separated from the dosing-induced enthalpy changes and the reaction enthalpy under ideal conditions due to the reactivity of the system already at room temperature. The reaction enthalpies obtained with the simplified model showed systematic variations over the covered concentration range of up to 40% of the absolute values. ATR (attenuated total reflectance) based fibre optic mid-infrared spectroscopy has been evaluated for reaction monitoring of the presented reaction, but suffered significantly from the non-ideality of the mixture obvious from the overrepresentation of diethylsulfate in the infrared spectra. Monitoring of the continuous flow synthesis of 1-ethyl-3-methylimidazolium ethylsulfate was therefore performed successfully by offline NMR spectroscopic analysis of quenched reaction mixtures. As a benchmark for the integration of the fibre optic sensors into microfluidic reaction setups, the residence time behaviour of these reactors was characterised. Step-change experiments were performed using a marker-solvent combination of 2-octanone and n-octane. The beneficial influence of the coiled geometry of the capillary reactors was unambiguously proven. Depending on the flow rate of the fluid a reduction of the axial dispersion predicted by the Taylor-Aris theory by a factor of 4 is possible.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2009

Author dc:creator

• Minnich, Clemens B.

Contributors dc:contributor

• Liauw, Marcel

• info:eu-repo/classification/ddc/660
• Ionische Flüssigkeit
• Kalorimetrie
• Infrarotspektroskopie
• Verweilzeitverteilung
• Chemometrie
• Mikroreaktor
• Technische Chemie
• Reaktionskalorimetrie
• faseroptische Sensorik
• Ionic Liquid
• Reaction calorimetry
• Chemometrics
• residence time distribution
• structured reactor
• micro reactor
• fibre optical sensor
• hard modelling

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-113532%22

OAI record oai:identifier

https://publications.rwth-aachen.de/oai2d?verb=GetRecord&metadataPrefix=oai_dc&identifier=oai%3Apublications.rwth-aachen.de%3A51220