Vol 57, No 10 (2017)

Published data on the influence of sulfur and its compounds on the ecological properties and performance characteristics of diesel fuels have been analyzed. The main characteristics of depressant, antiwear, and antioxidant additives to modern hydrotreated diesel fuels with low and ultralow sulfur content have been considered. A special emphasis is made on the additives based on synthetic and natural high-molecularweight compounds, including complex multifunctional broad-spectrum additives for clean diesel fuels, conforming to the European requirements and quality standards.

Eleven crude oils from the Gulf of Suez and Western Desert of Egypt have been used for the geochemical study. They have been analyzed for their metals, nitrogen and sulfur contents. Application of geochemical markers based upon these constituents has shown that crude oils could be correlated or differentiated according to their geologic age. The V/Ni, Ni/S, V/N, Ni/N, and S/N markers were almost uniform in Miocene oils, revealing the same origin, yet showing marked differences in Cretaceous crude oils reflecting varying degrees of their maturity, source materials, depositional environment and migrational history. The significance of analyzing the non-hydrocarbon constituents of the heavy petroleum fractions were extended to protecting the catalyst used in cracking processes. The results showed that trace metals and nitrogen contents are within the permissible limits in gas and diesel oils yet they are much beyond those limits in the heavier fractions.

The features of the distribution of vanadium and nickel between asphaltenes and resins have been revealed using heavy oils from Tatarstan and Samara oblast oilfields as an example. It has been shown that depending on the V and Ni content in asphaltenes and resins, heavy oils of different productive plays are divided into two separate groups. An increase in the V or Ni content of heavy oils is accompanied by an increase in the concentration of the respective metal in asphaltenes and resins. The intervals of variation in the V and Ni content of asphaltenes and resins of the oils attributed to each group have been determined. As the V concentration in asphaltenes increases, the V/Ni ratio also increases, a feature that is not characteristic of resins.

Comparative analysis of heterogeneous catalysts for the peroxide oxidation of thiophene is conducted. The catalysts are imidazole ionic liquids (ILs) containing anions of phosphomolybdic and phosphotungstic acids immobilized on mineral supports. Immobilization is implemented by the covalent bonding of an IL fragment to a silica surface or by adsorption on alumina. The catalysts are active not only in the model oxidation of thiophene in isooctane, but also in the desulfurization of a straight-run diesel fraction and the “synthetic crude oil” derived from oil shale.

Several methods have been used to reduce problems caused by wax precipitation during the production and/or transportation of waxy crude oil. Polymers are used to improve pour point and rheological behavior of waxy crude oils. In this work, the influence of the polymer inhibitors such as methacrylate polymers, as wax inhibitor, with different range of molecular weight and alkyl side chain carbons on the rheological behavior and pour point of two Iranian waxy crude oils were evaluated. Two Iranian waxy crude oils were selected on the basis of wax and asphaltene contents. The rheological behavior of these crude oils in absence and in presence of methacrylate polymer was studied. The rheological data cover the temperature range of–1 to 12°C. The results indicated that the performance of methacrylate polymer was dependent on the molecular weight, alkyl side chain carbons and the asphaltene content of crude oil. Methacrylate polymers with longer alkyl side chains than 18 carbons would perform best as wax inhibitors in two cases. Also, for crude oil with low asphaltene, higher molecular weight methacrylate polymer is the best flow improver and lower molecular weight methacrylate polymer showed good efficiency for crude oil with high asphaltene content.

The synthesis of gasoline from methanol and methanol/water mixture, the products of the partial oxidation of methane, in the presence of pilot samples of zeolite catalysts with the MFI structure has been investigated. It has been shown that the presence of a significant amount of water, 1.5–2 times that of methanol by mass in the mixture, leads to increased gas formation. It has been found that formaldehyde and formic acid impurities reduce methanol conversion and selectivity for gasoline.

Solutions of 5-vinyl-2-norbornene (VNB, 5-vinylbicyclo[2.2.1]hept-2-ene) and the related compounds 5-ethylidene-2-norbornene (ENB, 5-ethylidenbicyclo[2.2.1]hept-2-ene) and 2-vinyl-2-norbornane (VNN, 2-vinylbicyclo[2.2.1]heptane) in cyclohexane have been irradiated with γ-rays at 40°C. The initial radiation-chemical yields G₀ for the consumption of the solutes and the formation of final products of γ-radiolysis of the solvent cyclohexane have been determined. It has been shown that solute consumption and molecular hydrogen formation yields G₀(−RH) and G₀(H₂), respectively, are linearly related to the first vertical ionization potential of the solute. The G₀ values of molecular hydrogen, cyclopentadiene (CPD), butadiene, and methylallene, minor products of γ-radiolysis (40°C) of liquid VNB, ENB, and dicyclopentadiene (tricyclo[5.2.1.0^2.6]decadiene-3.8), have been determined. It has been shown that the G₀ values of CPD formation linearly depend on the first vertical ionization potentials of γ-irradiated bicyclic dienes. It is concluded that the γ-irradiation of cyclohexane generates two kinds of radical cations, which differ in mobility and reactivity.

It has been shown that the most appropriate and simple process for desulfurization of motor fuels is the direct oxidation of sulfur compounds with atmospheric oxygen on heterogeneous catalysts based on transition metal oxides. The feasibility of oxidation of thiophene with atmospheric oxygen in a model mixture with dodecane over vanadium–molybdenum catalysts has been shown, as well as that of oxidative desulfurization of actual straight-run diesel fraction. The activity of a number of samples of oxidative of desulfurization catalysts has been examined, the composition of the most effective catalyst has been determined, and optimum process conditions have been found.