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- Author or Editor: M. M. Barbooti x
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The thermal transitions of Na2S2O8 and K2S2O8 have been studied by means of a derivatograph in the presence of CuO or ZnO at various molar mixtures. A slight shift in the DTG peak of the first decomposition stage (persulfate into pyrosulfate) to higher temperature was noticed as the amount of oxide increases.
A rapid method for the characterization of some Iraqi crude oils is described, based on thermogravimetric data obtained using a selected heating program.
Five heavy crude oil samples from the Quayarah field were thermally evaluated using two modes of thermogravimetry (TG): dynamic and programmed TG with heating and hold-up periods at 350 and 550°. The light and medium volatility fraction (L+M) appeared directly proportional to the metal content. In contrast, the heavy fraction (H) (350–550°) was inversely proportional to the metal content. This contradiction was attributed to the autocatalytic degradation of some of the heavy fraction into lighter species, which upgrades the crude with respect to the (L+M) fraction at the expense of the heavy fraction. The crudes were identical with regard to the ratio (L+M) to (H+R), whereR=residue, as a consequence of their identical API gravity and sulphur contents.
Thermoanalytical investigations of the V2O5-K2S2O8 system have revealed that, in the presence of excess amounts of V2O5, the initial decomposition temperature is lowered compared to that of the pure salt. An explanation for this lowering is based on the interaction between V2O5 and the peroxo group of the persulfate ion. The reaction however, is, not unimolecular. The presence of an unknown potassium sulfate complex of V(V) with a catalytic character is indicated by XRD patterns obtained for samples heated up to 410°. It has been found that the formation of K3VO8, KV(SO4)2, K3V5O14 and K4V10O27 depends on whether V2O5 or K2SO4 is present in excess during thermal decomposition.
