Novel lactam-cation-based Brønsted acid ionic liquids (ILs) were prepared through a simple and atom-economic neutralization reaction between a lactam, such as caprolactam and butyrolactam, and a Brønsted acid, HX, where X is BF4-, CF3COO-, phCOO-, ClCH2COO-, NO3-, or H2PO4-. The density, viscosity, acidic scale, electrochemical window, temperature dependency of ionic conductivity, and thermal property of these ILs were measured and investigated in detail. The results show that protonated caprolactam tetrafluoroborate (CPBF) has a relatively strong acidity with -0.22 of Hammett acidic scale H0 and caprolactam trifluoroacetate (CPTFA) and pyrrolidonium trifluoroacetate (PYTFA) ILs possess very low viscosities, that is, 28 cP and 11 cP, respectively. An investigation of thermal property showed that a wide liquid range (up to -90 degrees C), moderate thermal stability (up to 249 degrees C for 10% of decomposition), and complex polymorphism were observed in these ILs. In comparison to imidazolium-cation-based ILs, the lactam-cation-based Brønsted acid ILs have a relatively lower cost, lower toxicity, and comparable ion conductivity and heat storage density (more than 200 MJ/m3). They have wide applicable perspectives for fuel cell devices, thermal transfer fluids, and acid-catalyzed reaction media and catalysts as replacements of conventional inorganic acids.

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Refined methyl, ethyl, propyl, 1-butyl, and 2-butyl biodiesels as well as unrefined methyl biodiesels containing glycerides were prepared, and their solvent power was evaluated by measuring the kauri-butanol value. By analysis of the kauri-butanol values of biodiesels with different fatty acid profiles and different alcohol types, some interesting results were obtained. The pure methyl esters have larger kauri-butanol values than those containing glycerides. The unsaturated fatty acid esters have larger kauri-butanol values than saturated fatty acid esters, while the number of double bonds of the unsaturated fatty acid has little effect on the value. The shorter the carbon chain of the fatty acid group or alcohol group, the larger the kauributanol value of biodiesel. Biodiesel with straight chains has a larger kauri-butanol value than that with branched chains.