Koji Ukegawa

Mechanism of lower oxidizability of eicosapentaenoate than linoleate in aqueous micelles

The aerobic oxidation kinetics of methyl eicosapentaenoate (20:5n-3) and methyl linoleate (18:2n-6) were compared in homogeneous chlorobenzene solution and in Triton X-100 aqueous micelles at 37°C. The rate of disappearance of 20:5n-3 was two times faster than that of 18:2n-6 in chlorobenzene, while the former was five times slower than the latter in aqueous micelles. It was also observed that ΔO2=Δ18:2n-6 and ΔO2=2Δ20:5n-3 in aqueous micelles. In the oxidation of a 1∶1 mixture of 20:5n-3 and 18:2n-6 in micelles, the rate of disappearance of 20:5n-3 was 3.6 times faster than that of 18:2n-6, and the rate of total substrate disappearance was reduced by a factor of 5 as compared with 18:2n-6 oxidation. These data suggest that the peroxyl radical derived from 20:5n-3 is more polar than that from 18:2n-6, and the former is likely to diffuse from the core to the micelle surface. This lowers the oxidizability for 20:5n-3 in aqueous micelles by enhancing the termination reaction rate for peroxyl radicals and by reducing the rate of propagation since there may be more 20:5n-3 peroxyl radicals at the surface than in the micelle core.

Mechanism of lower oxidizability of eicosapentaenoate than linoleate in aqueous micelles. II. Effect of antioxidants

We have reported that the peroxyl radicals derived from methyl eicosapentaenoate (20:5n-3) are more polar than those from methyl linoleate (18:2n-6) since the former peroxyl radicals have at least two molecules of oxygen in a molecule while the latter peroxyl radical has one. This lowers the oxidizability for 20:5n-3 in aqueous Triton X-100 micelles by enhancing the termination reaction rate for peroxyl radicals and by reducing the rate of propagation since there may be more polar peroxyl radicals derived from 20:5n-3 at the surface than within the micelle core. In this study, we measured the effect of three antioxidants, di-tert-butyl-4-methylphenol (BHT), 2,2,5,7,8-pentamethyl-6-chromanol (PMC) and 2-carboxy-2,5,7,8-tetramethyl-6-chromanol (Trolox), on the oxidation of lipids in aqueous micelle. Antioxidants give a clear induction period during oxidation of 18:2n-6 initiated with a water-soluble radical initiator, and its induction length decreases in the order of BHT>PMC>Trolox. This is consistent with the proposed location of three antioxidants: being in the core of micelle, at the surface, or in aqueous phase, respectively. However, BHT does not inhibit the oxidation of 20:5n-3 efficiently, and its rate of oxidation is slower than that observed in the oxidation of 18:2n-6, supporting the idea that polar peroxyl radicals derived from 20:5n-3 are preferentially located at the surface of the micelle. Similar results were obtained when oxidation was initiated with a lipid-soluble radical initiator except antioxidants had lesser effect on the oxidation rate of 20:5n-3.

Solvent extraction of nitrogen compounds from coal liquids

Abstract Nitrogen compounds were separated efficiently from coal liquids by solvent extraction with methanol and water. Middle distillates of Wandoan and Battle River coal liquid and a mixture of model compounds were employed as feed oils. This paper reports the experimental conditions for the effective separation of nitrogen compounds, such as quinoline and indole. In particular, the effects of extraction solvents on extraction yield and selectivities of nitrogen compounds were investigated.

Catalytic activity for synthesis of isomerized products from benzene over platinum-supported sulfated zirconia

Abstract The catalytic activity of Pt/SO 4 2− /ZrO 2 in the benzene hydrogenation and isomerization reaction at 250°C is superior to that of other Pt/conventional solid acid catalysts such as Pt/HY-zeolite and Pt/H-mordenite. The catalytic activity of SO 4 2− /ZrO 2 for cyclohexane isomerization to methylcyclopentane at 250°C is higher than that of HY-zeolite and H-mordenite. SO 4 2− /ZrO 2 and HM10 have more Bronsted acid sites of the highest strength and show a higher percentage of isomerization conversion. In contrast, ZrO 2 , which contains almost no Bronsted acid sites, and HY5.6, which contains almost no Bronsted acid sites of the highest strength, show a lower conversion percentage. Consequently, Bronsted acid sites of the highest strength are active sites responsible for cyclohexane isomerization. However, the isomerization conversion percentage does not completely correlate with the number of highest-strength Bronsted acid sites, suggesting that not all of these sites contribute to the reaction nor do only Bronsted acid sites influence cyclohexane isomerization. Neither the total number nor the number of highest-strength Lewis acid sites correlates with the isomerization conversion rate, indicating that Lewis acid sites are not responsible for cyclohexane isomerization.

Methanol-mediated extraction process for the separation of phenolic compounds from coal liquids

Abstract Phenolic compounds in a naphtha distillate of coal liquid were efficiently extracted into water by using methanol as a mediator for the extraction. The effects of extraction solvents on extraction yields and selectivities of phenolic compounds were examined.

Catalysis of iron sulfates on hydroconversion of 1-methylnaphthalene

Abstract In order to develop suitable catalyst for hydroconversion of heavy hydrocarbon materials, possibility of high quality catalyst production from iron sulfates was pursued on the hydroconversion of 1-methylnaphthalene (1-MN). Catalytic activities of iron sulfates were very low in the absence of sulfur (S). Hydrogenation activity of ferrous sulfate dramatically increased with addition of S. Activity of ferric sulfate, however, did not increase with addition of S. From XRD analysis of catalysts recovered after the reaction, it indicated that ferrous sulfate was transformed to pyrrhotites Fe 1− x S above 350°C in the presence of enough S. But ferric sulfate was not transformed to pyrrhotites easily. Effect of reaction temperature and additive effects of S, presulfiding temperature and sulfuric acid to the activity, selectivity and structure of iron sulfates were investigated in detail. From results of 1-MN hydroconversion, ferrous sulfate is revealed one of useful catalyst precursors for hydrogenation of aromatic hydrocarbon.

Methanol-mediated extraction for coal liquid (2) — the effect of phase separation caused by methanol on naphtha fraction derived from Wyoming coal

Abstract Methanol-mediated extraction, which the authors have developed, was conducted on the naphtha fraction derived from Wyoming coal. When 0.4–1.5 times methanol was added to the feed oil, the mixture formed a two-phase system. The extraction yield of phenol ranged from 86.3% to 99.2% and that of oil fraction ranged from 65.5% to 91.0%. This indicates that the extraction of phenol by methanol only was ineffective. Two extraction methods, extraction with water regardless of the presence of phase separation (method A), and that after separating the formed phase (method B), were conducted to compare the effect of phase separation on the extraction yield and selectivity of phenol. They had no significant differences between two extraction methods. From these results, we concluded that method A is applicable even if phase separation may occur by adding methanol.

Free radicals formed in hydrotreated coal liquid and influence of oxygen

The behavior of radicals formed in hydrotreated coal liquid with heat treatment and the influence of oxygen have been investigated by electron spin resonance (E.S.R.) spectroscopy. A set of E.S.R. spectral lines identified as phenalenyl radical appears from 50/sup 0/C as the oil is heated in argon atmosphere. The radical concentration is enhanced with temperature, reaches a maximum between 130 and 150/sup 0/C and then decreases at higher temperatures. The radical is very stable even at 200/sup 0/C for the sample hydrotreated under mild condition, whereas the radical in the sample treated under severe conditions disappears drastically from 150/sup 0/C. When oxygen is introduced in the oil, the radical is converted into semiquinone and/or aryloxy radicals and stable molecules. The treatment in the presence of oxygen at higher temperatures is considered to accompany the formation of other aryloxy radicals by the reaction of aromatic hydrocarbons and oxygen.

Autoxidation of Phosphatidylethanolamine Induced by Copper (II) Ions in Aqueous Dispersions

The kinetics of the aerobic oxidation of phosphatidylethanolamine (PE) induced by copper (II) ions was studied in Tween 20 micelles at 37°C. The kinetic order with respect to concentrations of PE hydroperoxides was 0.3, indicating the oxidation to be initiated by decomposition of the hydroperoxides catalyzed by copper (II) ions. The copper (II) ion-induced oxidation of PE+phosphatidylcholine (PC) in Tween 20 micelles was carried out, and the oxidation rate was noted to increase with the PE/PC mole ratio, possibly due to formation of a PE-copper (II) ion complex.

An attempt to separate nitrogen compounds

Abstract Coal liquids contain large amounts of nitrogen and oxygen compounds which make the processing of these into fuel uneconomical compared with petroleum. This paper investigates a method of separating the nitrogen compounds as sediments to provide valuable chemicals and clean fuel. Indole contained in coal liquids was photo-oxidized in carbon tetrachloride. The presence of galvinoxyl in the photo-oxidation process affected the formation of sediments in such a way as to suggest a radical reaction process. Whilst increased indole concentration led to increased sediment formation, the percentage yield was lower due to increased solubility of the sediment in highly polar solution. An optimum concentration is therefore indicated.