Differences between deoiled asphalt and oxidized asphalt
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The softening point of the residue obtained through solvent deasphalting is 105; what is the difference between this and the asphalt produced by oxidation processes? Please ask the experts for guidance
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There’s a big difference between the two! Deoiled asphalt is a product of solvent deasphalting units; it is obtained by using butane as a solvent to remove the wax components from residual oil, with the remaining heavier fraction constituting the deoiled asphalt. In the case of oxidized pitch production, the raw material used is different from that in the conventional vacuum distillation process; moreover, oxidation treatment is carried out by blowing air at high temperatures. As a result, oxidative polymerization reactions occur in coal pitch, and the aromatic compounds contained in it undergo oxidative cross-linking reactions with oxygen. Oxygen becomes incorporated into the molecular structure of the aromatic compounds in coal pitch, thereby changing its molecular composition. The O/C atom ratio of the medium-temperature pitch used as raw material is 0.014, meaning that there is approximately 1 oxygen atom for every 100 carbon atoms. In contrast, the O/C atom ratio of the oxidized pitch ranges from 0.041 to 0.048, meaning that there are approximately 4–5 oxygen atoms for every 100 carbon atoms. The thermal oxidation process significantly promotes the polycondensation of coal pitch molecules, thereby increasing the coking residue value of coal pitch. As the oxidative polymerization proceeds, the hydrogen content of coal tar pitch gradually decreases. The hydrogen content of the raw medium-temperature pitch is approximately 4%, while that of the oxidized pitch is around 2% – a reduction of half in hydrogen content. The H/C atom ratio of the raw medium-temperature pitch is 0.477, whereas it drops to 0.238–0.324 in the oxidized pitch. This indicates that significant dehydrogenation and polycondensation reactions occur during the oxidative thermal polymerization of coal tar pitch, thereby promoting the cross-linking and polycondensation of its molecular structure and endowing the oxidized pitch product with coking-resistant properties
Are there any industrial plants for the oxidation of coal tar pitch in operation?