1-bütil-3-metilimidazolyum katyonlu iyonik sıvıların saf halde ve metal-oksit destekler üzerindeki kısa ve uzun dönemli ısıl dayanıklılık limitlerini belirleyen yapısal faktörler

Ionic liquids (ILs) are the first choice in many applications such as synthesis, electrochemistry, and especially in catalysis because of their tunable physicochemical properties. In catalysis field, determination of thermal stability limits of metal-oxide supported ILs is crucial for proper choice of ILs at application conditions because determined stability limits of pure ILs are not applicable for these systems. Because, ILs directly interact with metal-oxides and these interactions influence thermal stability of ILs significantly. In the first part of this study, structural factors determining thermal stability of ILs with 1-n-butyl-3-methylimidazolium, [BMIM]+, cation on SiO2, TiO2, γ-Al2O3, and MgO were determined. Results show that thermal stability limits of ILs increase with decreasing inter-ionic interaction strength. Stability limits of ILs linearly increase with increasing acidity of C2 proton on imidazolium ring, controlling inter-ionic interaction strength. Moreover, anion size significantly influences stability limits. Presence of metal-oxide lowers stability limits significantly as surface acidity decreases with increasing point of zero charge (PZC) of metal-oxide. Based on these findings a model was developed as a function of PZC and ν(C2H) to estimate stability limits of [BMIM]+-based metal-oxide-supported ILs. Finally, γ-Al2O3-supported ILs' long-term thermal stabilities were determined by isothermal TGA measurements based on 1 % mass loss after 6 h treatments. Long-term stability limits were lower more than 60 °C from short-term stability limits. Furthermore, activation energy Ea required for decomposition were determined from the results of isothermal treatments. This study was the first step of the studies on catalysts with the IL-coated supported metal complexes.