Protonic Ammonium Nitrate Ionic Liquids and Their Mixtures: Insights into Their Thermophysical Behavior

Abstract

This study is centered on the thermophysical characterization of different families of alkylammonium nitrate ionic liquids and their binary mixtures, namely the determination at atmospheric pressure of densities, electric conductivities and viscosities in the 288.15 < T/K < 353.15 range. First, measurements focusing on ethylammonium, propylammonium and butylammonium nitrate systems, and their binary mixtures, were determined. These were followed by studies involving binary mixtures composed of ethylammonium nitrate (with three hydrogen bond donor groups) and different homologous ionic liquids with differing numbers of hydrogen bond donor groups: diethylammonium nitrate (two hydrogen bond donors), triethylammonium nitrate (one hydrogen bond donor) and tetraethylammonium nitrate (no hydrogen bond donors). Finally, the behavior of mixtures with different numbers of equivalent carbon atoms in the alkylammonium cations was analyzed. The results show a quasi-ideal behavior for all monoalkylammonium nitrate mixtures. In contrast, the other mixtures show deviations from ideality, namely when the difference in the number of carbon atoms present in the cations increases or the number of hydrogen bond donors present in the cation decreases. Overall, the results clearly show that, besides the length and distribution of alkyl chains present in a cation such as alkylammonium, there are other structural and interaction parameters that influence the thermophysical properties of both pure compounds and their mixtures.

Influence of Small Quantities of Water on the Physical Properties of Alkylammonium Nitrate Ionic Liquids

“…In view of the results, it seems critical to control and determine the water content if an accurate characterization is to be made. For this reason, in this work we have proposed as an objective to study systematically the influence of the content of small quantities of water (from about 300 to 30,000 ppm) in EAN and PAN on the measurement of density, [15] (red squares), [23] (green dots), [24] (yellow dots), [27] (orange dots), [28] (cyan dots), [29] (red dots), [32] (pink dots), [36] (grey dots), [41] (dark green dots), [46] (brown dots), [48] (blue dots), [52] (dark red dots), [58] (purple dots), [60] (green squares), [65] (yellow squares), [67] (orange squares), [70] (cyan squares), [71] (pink squares), [75] (grey squares), [76] (dark green squares), [77] (brown squares), [81] (blue squares), [82] (dark red squares), [85] (purple squares), [86] (green rhombs), [87] (cyan rhombs) and [89] (orange rhombs).…”

“…Considering that a thorough and accurate characterization of these materials has a direct impact on the knowledge of their structure and in the design of their potential applications, we have performed an exhaustive compilation of some of the most relevant physical properties. Thus, we have reviewed the state of the art of density, viscosity, electrical conductivity, refractive index and surface tension for EAN and PAN at different temperatures [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 ,…”

Solid–liquid equilibria of binary mixtures of fluorinated ionic liquids

“…The literature related to ionic liquid mixtures is focused on their interactions,21–23 physical properties (such as densities,24,25 viscosities,24,26,27 excess volumes,24–28 surface tensions,2,29,30 diffusion coefficients31 and conductivities24,26) mutual miscibility32,33 and phase behaviour,20,32,34–36 among others. Several mixtures of simple ILs do not show a clear freezing point and never form a crystalline phase4 which leads to the difficult task of determining their complete phase diagrams 20,31,37.…”

Separation of azeotropic mixtures using protic ionic liquids as extraction solvents

“…Moreover, ILs can be easily tuned to obtain the appropriated properties for the chemical engineering needs in terms of efficiency and cost of the processes [5]. However, since conventional ILs (aprotic ILs) are expensive due to their complex synthesis procedures, the possibility of obtaining ILs from cheap precursors and simple synthesis processes, place the protic ionic liquids (PILs) as a great alternative to traditional ILs [6,7]. These PILs combine excellent properties, such as their high conductivity and exceptional electrochemical properties [7].…”

“…However, since conventional ILs (aprotic ILs) are expensive due to their complex synthesis procedures, the possibility of obtaining ILs from cheap precursors and simple synthesis processes, place the protic ionic liquids (PILs) as a great alternative to traditional ILs [6,7]. These PILs combine excellent properties, such as their high conductivity and exceptional electrochemical properties [7]. Moreover, these compounds present one or more labile hydrogen atoms (in the cationic species) that allow the presence the strong hydrogen bonding interactions.…”