Design of an ionic liquid purification process

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Journal Title

Journal ISSN

Volume Title

Kemian tekniikan korkeakoulu | Master's thesis

Date

2022-08-23

Department

Major/Subject

Chemical and Process Engineering

Mcode

CHEM3043

Degree programme

Master's Programme in Chemical, Biochemical and Materials Engineering

Language

en

Pages

100 + 16

Series

Abstract

Increasing consumption of textiles and environmental awareness demanded for new approaches to produce more environmentally sustainable fibres. The Ioncell process was developed as a solution, produces high quality fibres from renewable cellulosic feedstocks as a closed loop. However, the process generates by-products and impurities that have detrimental effects on the solvent dissolution capability. Therefore, the effectiveness of the solvent purification process is of paramount importance. Additionally, ionic liquids are utilised as the solvent, which are expensive due to the cost of the superbases that make up the ionic liquid. Ensuring a high recovery rate and effective removal of the impurities from the solvent is necessitated for an economically sustainable process. This thesis aims to determine the most suitable distillation method for the various ionic liquids, considering economic sustainability and removal of recently discovered impurities. The distillation studies were performed for five different ionic liquids, [DBUH][OAc], [DBNH][OAc], [mTBDH][OAc], [mTBDH][Lactate], [mTBDH][Levulinate] and were operated at low-pressure between 0.4 – 1.5 mbar. The purification process performance was characterised and analysed using nuclear magnetic resonance spectrometry (NMR), liquid chromatography-mass spectrometry (LC-MS), and Karl Fischer (KF) titration. Simulation of the impurity removal for short path distillation using Aspen model was performed although there were challenges reproducing the experiment results. Limitations with the impurity data were identified to have affected the Aspen model. The results indicates that removal of the recently discovered impurities were possible, even at 1 wt-% in the ionic liquid. Short path distillation was observed to give a high recovery rate of 87 % for the ionic liquid while batch distillation was more effective with the removal of impurities. Short path distillation was concluded to be the most suitable method for [DBNH][OAc], [mTBDH][OAc], and [mTBDH][Levulinate]. It was also concluded that [mTBDH][Lactate] was not suitable with any distillation method due to polymerisation reactions.

Description

Supervisor

Alopaeus, Ville

Thesis advisor

Uusi-Kyyny, Petri
Pitkänen, Leena

Keywords

ionic liquid, short path distillation, vacuum, Ioncell, [mTBDH], [DBUH]

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