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 H-1 NMR, C-13 NMR and FTIR. H-1 NMR and C-13 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 E-a, A and g(alpha) models of the materials were determined. The average activation energies (E-a) obtained from both models for the decomposition of phospholipids are 64.15 kJ/mot and 122.3 kJ/mol and the pre-exponential factors In(A) were 15.8 and 20.4 for stages I and II, respectively. The decomposition of phospholipids proceeds by two-dimensional diffusion (D-2) for stage I, followed by three-dimensional diffusion (D-5) for stage II. (C) 2013 Elsevier B.V. All rights reserved.