Desorption process in room temperature ionic liquid based-mixtures under vacuum

Abstract

A desorption process of room temperature ionic liquids (RTILs) based-mixtures is examined by monitoring the mass transfer and temperature under vacuum. Cations of RTILs are N, N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium, [DEME], 1-ethyl-3-methylimidazolium, [C2mim], and 1-butyl-3-methylimidazolium, [C4mim]. Anions are tetrafluoroborate, [BF4], and bis(trifluoromethanesulfonyl)imide, [TFSI]. Additives for mixtures are H2O, D2O, CH3OH, C2H5OH, n-C3H7OH, i-C3H7OH, (CH3)2CO and C6H6. At the early stage of the desorption process under vacuum, transparent [DEME][TFSI]– and [C2mim][TFSI]–i-C3H7OH turned to be white homogeneously. Then, accompanying with drastic changes in the mass and temperature curves at the late stage, the mixtures become transparent again. At low-pressure, critical scattering as a precursor phenomenon of phase separation appeared only in [DEME][TFSI]– and [C2mim][TFSI]–i-C3H7OH. At room temperature and ambient pressure, different Raman spectra of a [TFSI] anion in [DEME][TFSI]–n-C3H7OH and –i-C3H7OH were observed in propanol-rich region. Therefore, the mixing states are drastically changed by respective propanol isomers.