Kinetics of thermal decomposition of phospholipids obtained from phosphate rock

The soluble organic matter in the phosphate rock was extracted with n-hexane. Its structure was analyzed by using 1H NMR, 13C NMR and FTIR. 1H NMR and 13C NMR studies indicated that it has rather aliphatic nature. FTIR results showed that the bands obtained from organic matter exhibit a phospholipids characteristic. The kinetics of thermal decomposition of phospholipids obtained from phosphate rock was studied by means of thermal analysis techniques (TG/DTG) in nitrogen atmosphere at heating rates of 2.5, 5, 10, and 20 K min− 1. TG and DTG measurements indicated that thermal behavior of phospholipids has two-stage degradation. Kinetic parameters were determined from the TG and DTG curves for the stages I and II by using two model-free methods, i.e. Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose. The kinetic triplets consisting of Ea, A and g(α) models of the materials were determined. The average activation energies (Ea) obtained from both models for the decomposition of phospholipids are 64.15 kJ/mol and 122.3 kJ/mol and the pre-exponential factors ln(A) were 15.8 and 20.4 for stages I and II, respectively. The decomposition of phospholipids proceeds by two-dimensional diffusion (D2) for stage I, followed by three-dimensional diffusion (D5) for stage II.