AIR OXIDATION OF TURKISH BEYPAZARI LIGNITE .1. CHANGE OF STRUCTURAL CHARACTERISTICS IN OXIDATION REACTIONS AT 150-DEGREES-C

The oxidation of Beypazari lignite was carried out in air at 150-degre es-C for up to 168 h. Oxidized samples were withdrawn from a ventilate d oven at different periods of time and characterized by elemental ana lysis, diffuse reflectance Fourier transform infrared (DRIFT), solid-s tate C-13 CP/MAS/TOSS NMR, and pyrolysis mass (Py-MS) spectroscopies. It was found that oxidation influenced the organic structure and the i norganics at different periods of the oxidation. Iron(II) sulfate was formed in 24 h, during which time there was almost no change of alipha tic CH2 and CH3 groups. After the formation of iron(II) sulfate, aliph atic CH2 and CH3 groups started to oxidize. Thus, the formation of iro n(II) sulfate apparently prevented the oxidation of organic structure of Beypazari lignite during the first 24 h. The van Krevelen diagram ( H/C vs O/C), the change of the O/H atomic ratio, and the rate of loss of aliphatic CH2 and CH3 groups showed the organic structure of Beypaz ari lignite to have continued in three stages. Aromatics seemed to be more stable than aliphatics during the oxidation process. The function al groups produced by the oxidation included ketones, carboxyls, and a nhydrides but the major oxidation products were aryl esters. The abund ance of CO2+, CO+, CH3COOH+, and SO2+ molecular ions increased in the pyrolysate of the oxidized sample whereas the molecular ions alkylphen ols, dihydroxybenzenes, and alklynaphthalenes decreased after the oxid ation.