Investigation of Thermal Properties for some Ionic Liquids containing Urea and Acetamide

    Characterization of some room temperature ionic liquids (RTILs) as candidates for thermal storage media and heat transfer fluids in thermal applications were investigated. Five ionic liquids prepared from ammonium alum [NH4Al(SO4)2.12HO] pronounced S, as inorganic salt with urea [NH2CONH22] pronounced U, or acetamide [CH 3CONH ] pronounced A, as organic compounds, and  aluminum nitrate [Al(NO 3)32.9HO] pronounced N with urea or acetamide compounds in different mole ratios were investigated alone and with addition of some improving materials to study their synergetic effect using thermo-gravimetric analysis (TGA), Differential Scanning Calorimetery (DSC), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy and conductivity measurements. Thermo-physical properties such as enthalpy ∆H, heat capacity Cp2 and thermal energy storage capacity were determined. It was found that hydrated aluminum nitrate:acetamide (1:22 mole ratio, AN2IL) alone and hydrated ammonium aluminum sulfate:urea (1:5 mole ratio, USIL) alone or with addition of some materials characterized with high density, chemical stability, heat capacity, thermal energy storage capacity and wide temperature range. The results indicated that ionic liquids alone or with addition of some materials could be considered as a promising candidate for liquid thermal storage media and heat transfer fluids. Studying the synergetic effect by addition of some alkali metal hydroxide (NaOH) with hydrated aluminum nitrate:urea (1:1.2 mole ratio, UNIL)  and KOH with hydrated ammonium aluminum sulfate:urea (1:5 mole ratio, USIL)ionic liquids increased thermal energy storage capacity of these ionic liquids,while the addition of NaOH to hydrated aluminum nitrate:acetamide (1:22mole ratio, AN2IL) gave less thermal stability and storage capacity of ionic liquid. Also addition of alkaline earth metal oxide MgO, CaO to hydrated ammonium aluminum sulfate:urea (1:5 mole ratio, USIL) and BaO to hydrated aluminum nitrate:urea (1:1.2 mole ratio, UNIL) decreased thermal stability, heat capacity and thermal energy storage capacity than ionic liquid alone. Moreover, addition of transition metal oxide (VOSO 4.5HO, CuO and ZnO)to hydrated ammonium aluminum sulfate:urea (1:5 mole ratio, USIL)increased thermal stability and storage capacity of hydrated ammonium aluminum sulfate:urea (1:5 mole ratio, USIL), while the addition of NiO to hydrated ammonium aluminum sulfate:urea (1:5 mole ratio, USIL) only improve thermal stability of ionic liquid.