RESUMO
Understanding the chemistry of iron-based metal-organic precursor solutions for spray-flame synthesis is a key step to developing inexpensive and large scale applications for gas-phase synthesized, nano-sized iron oxide particles. Owing to the large variety of available organic solvents and iron compounds, the choice of a suitable precursor-solvent pair is challenging. Systematic investigations of the precursor chemistry of iron-based systems are currently not available. This work aims at filling this gap by providing a detailed spectroscopic analysis of mixtures containing iron(iii) nitrate nonahydrate and alkyl alcohols (C2-4). Moreover, the impact of adding 2-ethylhexanoic acid is explored. The FTIR spectra reveal the formation of carboxylates and allow deriving information about the coordination of the metal-carboxylate complexes. The stability of the precursor solutions is investigated by monitoring precipitation phenomena and turbidity. Furthermore, gas chromatography is employed to provide additional information on oxidation products and esters as well as to aid the interpretation of the FTIR data. It is found that the formation of esters has an enhancing effect on iron sorption and, thus, it promotes precursor stability.
RESUMO
The isobaric vapor liquid equilibria (VLE) of different binary mixtures of the ionic liquid (IL) 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (C2mimTfO) with the n-alkyl alcohols, methanol, ethanol, propan-1-ol, and butan-1-ol, are studied at the pressures of p = 500, 700, and 1000 mbar, covering a composition range 0.25-0.35 ≤ x(solvent) ≤ 1.0. Complementarily, the experimental results are compared with calculations by the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state (EoS). For deriving suitable PC-SAFT parameters, experimental liquid densities were determined for the neat IL C2mimTfO and its longer homologues, 1-butyl-3-methylimidazolium trifluoromethanesulfonate (C4mimTfO) and 1-hexyl-3-methylimidazolium trifluoromethanesulfonate (C6mimTfO), in a temperature range of 288.15 K ≤ T ≤ 363.15 K (C2mimTfO) and 293.15 K ≤ T ≤ 363.15 K (C4mimTfO and C6mimTfO), respectively. The PC-SAFT EoS is found to be suitable for describing the VLEs under study with good accuracy (AARDVLE ≤ 0.4%).
