TGA-MS Study of the Decomposition of Phosphorus-containing Ionic Liquids -Trihexyl(tetradecyl)phosphonium Decanoate and Trihexyltetradecylphosphoniumbis(trifluoromethyl)sulfonyl Amide

摘要

The phosphorus-containing ionic liquids (IL) decompose where ion pairs fall apart. Trihexyl(tetradecyl)phosphonium Decanoate, sold as Cyphos IL 103, and Trihexyltetradecylphosphonium bis[(trifluoromethyl)sulfonyl] Amide, sold as Cyphos IL 109, decompose in 200° to 475°C range in air and the fragments containing organophosphorus are found here among other major fragments of hydrocarbon arms. Black residues are found after heating in air to 740°C in TGA in 5.0% and 0.6% for Cyphos IL 103 and 109 respectively. They were presumably containing P2O5 after oxidation. Not all the phosphorus can be counted for at 740°C and falls short of calculated values of 10.9% and 9.3%, if residues contain nothing else but P2O5. Among the fragments we found in MS the organophosphorus fragments from decomposition of the cationic C32 H68 P+ including P with 3-4 hydrocarbon attached as well as the major fragments of linear hydrocarbon arms. Water evolves early at lower temperature and continues to 740°C. CO_2 comes from oxidation of carbon at high temperatures. The SO, SO2, CF3, CF2CF2 evolve in sulfur and fluorine containing anion in Cyphos IL 109. H3PO4 is detected, which is most likely from the reaction product of P2O5 and water. No P2O5 was found. ICP examines the P content in the ashes after burning in air to 700°C and found 3200 ppm (or 0.62 wt%) and 30 ppm (0.003%) in Cyphos IL 103 and 109 respectively.