Vol 58, No 8 (2018)

The structural and thermal properties of petroleum asphalt and its components have been analyzed using temperature-modulated differential scanning calorimetry (DSC). This technique makes it possible to distinguish processes, such as “order–disorder” and glass transition, ensuring identification of structural- phase transitions that are undetectable or overlapping on conventional DSC curves. The analysis of thermal effects for macro- and microcrystalline paraffins; mono-, bi-, and polycyclic aromatic hydrocarbons; asphaltenes; and benzene and alcohol–benzene resins allows identifying and interpreting effects on DSC thermograms of test asphalts.

A mixture of lower dialkyl disulfides (R = C₁–C₂) obtained by the demercaptanization of petrochemicals is converted to alkanethiols and dialkyl sulfides under the action of solid acid catalysts. In a helium medium, the main reaction products are methanethiol and ethanethiol; the total dialkyl sulfide selectivity is less than 20%. In a mixture of disulfides with methanol, the main reaction products are dimethyl, methyl ethyl, and diethyl sulfides; the total selectivity for these products achieves 98%.

The process of asphaltene precipitation has a substantial effect on oil production in petroleum industry. In this work, a series of experiments was carried to determine the asphaltene precipitation of crude oil during solvent titration condition with Iranian crude oil sample using experimental set up. The precipitants such as pentane, heptanes, hexane, nonane and decane with varying volumes were used. Also, a developed thermodynamic model based on micellization and PC-SAFT (perturbed chain modification Statistical Associating Fluid Theory) has been proposed to account asphaltene precipitation during solvent titration conditions and the proposed model was verified using experimental data obtained in this work and also with those reported in the literature. In the proposed micellization model the PC-SAFT EOS (cubic equations of state) is applied to predict the onset point and to perform flash calculations. In order to compare the performance of the proposed micellization model, the asphaltene precipitation experimental data were correlated using existing micellization model and the proposed micellization model. The results show that the proposed micellization model predicts more accurately the asphaltene precipitation experimental data and is in agreement with the experimental data of reported in this work and with those reported in the literature with a mean square error of 0.9%. Therefore the predictions obtained from this proposed model, resulted in a good agreement with experimental data which shows a significant improvement in comparison to the previous micellization model in the available literature.

The paper is devoted to the investigation of the catalytic properties of nickel-promoted molybdenum disulfide nanoparticles in the hydroconversion process. The formation of Mo and Ni compounds under hydroconversion conditions has been studied using chemical thermodynamics methods. Quantum-chemical calculations in the cluster approximation have confirmed the catalytic activity of Mo_nNi_mS_p nanoparticles in the reactions of hydrogen activation and aromatic-ring hydrogenation. It has been shown that the main role in the activation of hydrogen and the hydrogenation of aromatic rings is played by Mo- and Ni-containing active sites of the catalyst, respectively. To confirm theoretical assumptions, the yield of products of fuel oil hydroconversion on nanosized particles of the catalyst, nickel-promoted and in situ formed molybdenum disulfide, has been investigated. It has been shown that the promotion with nickel enhances the hydrogenating functions of the molybdenum-containing catalyst and lowers coke formation during hydroconversion.

Nickel–tungsten sulfide catalysts synthesized by two methods—conventional supporting of active components and in situ synthesis in the reaction medium—have been characterized by a complex of physicochemical analysis methods. The catalysts have been compared with respect to their activity in the hydrocracking of vacuum gas oil (VGO) in a batch mode under conditions of varying temperature (380–400°C), reaction time (3–10 h), and zeolite (4–8 wt %) and NiW content (0.85–1.7 wt %). It has been shown that the in situ synthesized catalyst is superior in the hydrocracking and hydrodesulfurization of VGO owing to the accessibility of active catalyst sites.

The effect of the polymer molecular weight on the catalytic properties of cobalt composites based on polyacrylonitrile (PAN) in the carbon monoxide hydrogenation reaction has been studied. It has been found that the CO conversion tends to 100% in the presence of any of the systems. It has been revealed that for the system based on PAN with a higher molecular weight, a quantitative CO conversion is observed at a lower temperature. It has been assumed that during the synthesis of the composite materials, the active phases undergo encapsulation differently. X-ray diffraction (XRD) analysis has revealed that the formation of metallic cobalt particles occurs regardless of molecular weight.

The effect of ultrasonication on the efficiency of ion exchange in a binder-free pelleted NaX zeolite (the molar ratio Si/Al = 1.34) has been studied using successive treatments with calcium, lanthanum, and ammonium nitrate solutions at 80°C with intermediate calcining after each ion exchange step in comparison with the ion exchange performed under identical conditions without sonication. It has been found that the ultrasonic treatment (a current of 2.6 A) at 80°C in a solution makes it possible to achieve a deep exchange of sodium cations in the zeolite framework (less than 0.3 wt % residual sodium oxide). The comparison of the physicochemical and catalytic properties of the catalyst samples obtained of shows a substantial advantage of the method of ultrasound-assisted ion exchange due to the almost complete exchange of sodium for the multicharged cations.

A series of diesters on the basis of 5,7-dimethyl-1,3-adamantanediol and 5,7-dimethyl-1,3- bis(hydroxymethyl)adamantane and C₃–C₁₀ aliphatic acids have been synthesized and their physicochemical and thermo-oxidative properties have been studied. The properties of the esters obtained have been compared to those of trimethylolpropane and neopentyl glycol esters.

The aim of this study is to investigate the production of biodiesel from two kinds of microalgae Chlorella sp. and Spirulina platensis. Various items such as culture, lipid extraction and the production of biodiesel have been studied. The results showed that the rapid growth of Chlorella sp. from 0.2 to 0.5 gr per liter productivity biomass of cultivation is more suitable than Spirulina microalgae with slow growth of 0.1 to 0.3 gr per liter for the productivity biomass of culture. In comparison to 26.2% lipid content of microalgae Chlorella sp., Spirulina microalgae lipid content and the amount of 14.3 indicate a significant difference. Biodiesel output value was 28.2% by direct transesterification method. According to the results, it could be argued that microalgae Chlorella sp. features make the most suitable microalgae species for biodiesel production. These features include: rapid growth and high productivity, biomass and suitable lipid contents, environmentally easier cultivation rather than other species, suitable fatty acid profiles, having the most common fatty acids compounds (as C14:0, C16:0 and C18:0) in biodiesel. Extraction method had the best performance of extraction by the biomass Bligh and Dyer method.

A new rapid method for analytical control of sulfur compounds in hydrocarbon media using test agents has been developed. The method is based on the interaction of an indicator (solid-phase reagent) with sulfur-containing compounds and the subsequent detection of the product by linear-colorimetric and spectrophotometric means. A new rapid method with spectrophotometric and colorimetric detection has also been developed for quantitative determination of sulfur- and nitrogen-containing substances simultaneously present in hydrocarbon media.

A series of complex was synthesized using phenyl hydroxamic acid and metallic chloride, and used for catalytic aquathermolysis of heavy oil at low temperatures for the first time. The effects of water content and catalyst concentration on aquathermolysis were investigated. And then a tri-component coupling aquathermolysis of water-heavy oil-methanol was designed and the reaction conditions were investigated. With the catalyst and methanol, the reaction occurred at temperatures as low as 180°C. The viscosity of the product was also substantially reduced by the decomposition of the large hydrocarbon molecules.