Study On Analysis Of Unstable Compositions And Improving Its Stability In Diesel Oil

Generally the straight-run distillate fuel, which is of good stability, contains less content of heteroatom compounds. However, Fluid Catalytically-Cracked diesel tends to degrade because of containing higher content of heteroatom compounds. In course of storage, these compounds will make FCC diesel generate more gum and sediment in diesel oil.In the paper, the types of diesel stabilizer are investigated, and it is indicated that diesel stabilizer is composed of Mannich condensation, amine and ether etc. Furthermore, the characteristics and mechanism of diesel stabilizers are introduced in detail. Additionally, the current situation and future development of diesel stabilizers are also reviewed.Stability of middle distillate fuel is closely related to its chemical composition. Identification of unstable chemical compositions plays an important role in studying stability of diesel oil. After -10 FCC diesel oil is extracted, it is found that, (1) the alcohol extract contains nitrogen compounds such as indene, indole and carbazole;aromatic hydrocarbon such as substituted benzene, naphthalene, anthracene, phenanthrene and biphenyl;phenol and substituted phenol;sulfur compound such as thiophene. (2)caustic extract comprises mainly of phenol by means of elementary analysis, IR, GC/MS and LC/MS. It is inferred that oxygen compound-phenol can exacerbate the degradation of diesel oil, specially combining with nitrogen compounds.We select several typical stabilizers to stabilize diesel oil, such as Mannich condensation, aliphatic amine, Nitro-oxy free radical and phenyl diamante, etc. Stability of-10~# FCC diesel oil and extracted oils by ethanol and alkali liquor are studied by adding stabilizers. It is found that sediment of extracted oil (II) is 0.3mg/100ml, its stability is best among several oils and is not influenced by additives. But diesel oil extracted by ethanol can be improved by the stabilizers. Therefore, we advise that extracted oil (I) canbe used combining with additive and extracted oil (II) can be used directly. Generally, the oxidation of diesel oil follows radical chemistry mechanism. Experiments show fuels with kinds of additive form sediment of the same structure. We infer stabilizers cannot affect formation mechanism of sediment. During storage, acidity of-10 FCC diesel oil decreases, which show that gum precipitates. But extracted fuel (I) and (II) with additives not. We presume that stabilizers X and product of stabilizers bind to materials of -10#FCC diesel oil, and stability of extracted fuel (I) can be improved because of nitro-Oxygen radical capturing hydrocarbon radical and peroxide radical , however extracted fuel (II) can contain a small amount of inorganic sodium salt and water, which effect presence of additive so that stabilizers doesn't act.