Petroleum Chemistry最新文献

A series of kerogen samples were isolated from Domanik oil shale before and after hydrothermal treatment in an autoclave (at 250–375°C, for 24 h). Than composition of the C₁–C₅ hydrocarbon gases generated in stepwise (300–800°C) pyrolysis of these kerogens was characterized by gas chromatography. According to the calculated EASY %Ro and Rock-Eval pyrolysis data, the highest maturity level of the organic matter reached by the hydrothermal treatment corresponded to the MC₄ stage. As the hydrothermal treatment temperature of the oil shale was elevated up to 325°C, the dry pyrolysis of residual kerogen led to the predominant generation of wet gases in which C₂₊ prevailed over methane; at temperatures above 325°C, methane was predominant. Based on the pattern of the generation curves plotted individually for C₁, C₂, C₃, C₂–C₅, and C₄–C₅ gases, methane was found to have additional sources in the kerogen structure, compared to C₂₊ gases. Ethane and ethylene are generated simultaneously via the free-radical decomposition of alkyl structures; moreover, at high pyrolysis temperatures, ethane and ethylene have some precursors other than those of C₃₊ gases.

The effect of low-frequency acoustic treatment and of constant and alternating electromagnetic fields on the reactivity of crude oil and resin–asphaltene components was studied. Irrespective of the kind of the wave treatment, the amount of asphaltenes and resins separated from the treated oil decreases owing the breakdown of aggregates of complex structural units with the release of hydrocarbons of various structures, occluded in the molecular complexes, into the liquid phase. The treatment involves cleavage of weak hydrogen bonds with the formation of additional reaction sites in paramagnetic asphaltenes and diamagnetic resins. The reactivity of both crude oil and the separated resin and asphaltene fractions significantly changes owing to the formation of new reactive structures in the physical fields. These structures differ not only in the size and structure but also in the antioxidant properties. The data obtained allow more detailed evaluation of the effect exerted by various kinds of wave treatment on the composition and structure of asphaltenes and resins of heavy high-viscosity crude.

An artificial neural network (ANN) model of a multilayer perceptron-type was developed to predict flash points of petroleum middle distillates. The ANN model was designed using 252 experimental data points taken from the literature. The properties of the distillates, namely, specific gravity and distillation temperatures, were the input parameters of the model. The training of the network was carried out using the Levenberg– Marquardt backpropagation algorithm and the early stopping technique. A comparison of the statistical parameters of different networks made it possible to determine the optimal number of neurons in the hidden layer with the best weight and bias values. The network containing nine hidden neurons was selected as the best predictive model. The ANN model as well as the Alqaheem–Riazi’s model was evaluated for the prediction of flash points by a statistical analysis based on the calculation of the mean square error, Pearson correlation coefficient, coefficient of determination, absolute percentage errors, and the mean absolute percentage error. The ANN model provided higher prediction accuracy over a wide distillation range than the Alqaheem–Riazi’s model. The developed ANN model is a reliable and fast tool for the low-cost estimation of flash points of petroleum middle distillates.

The effect of hydrothermal treatment of high-carbon low-permeability Domanik rock on the efficiency of recovering hydrocarbons from this rock by prolonged four-step extraction for 20, 68, 116, and 220 h with a mixture of organic solvents (chloroform, toluene, and isopropyl alcohol) was studied. As compared to the extraction from the untreated rock, the hydrothermal treatment at 300°С in a СО₂ medium allows recovery of a 6 times larger amount of the extract in the first step (in 20 h). In the second extraction step (68 h), the extract yield decreases by a factor of 8, but the relative content of saturated hydrocarbons in the extract increases by a factor of more than 3 compared to the first step, whereas the relative content of asphaltenes, resins, and aromatic compounds decreases. In the third extraction step (116 h), the extract yield is as low as 0.16%, the content of resins in it drastically decreases, whereas the content of asphaltenes increases to 52%. The extract of the fourth step (220 h) consists to 80.77% of asphaltenes. From the initial rock, the maximal yield of the extract enriched in saturated hydrocarbons with the minimal content of asphaltenes was observed after the second extraction step. In the course of prolonged extraction, the yield of petroleum fractions from the initial rock increases by a factor of almost 4, and in combination with the preliminary hydrothermal treatment, by a factor of 7. This fact demonstrates the possibility of generating an additional amount of hydrocarbons. Changes were revealed in the structural-group, hydrocarbon, elemental, and microelemental composition of petroleum fractions recovered from the low-permeability Domanik rock, depending on the extraction time and transformations of the organic matter of this rock in the course of hydrothermal treatment.

Clean fuel production with strict limit on toxic contaminants is one of the most important aims for petroleum refinery industry regarding the improvement of environmental conditions. In this study, oxidative desulfurization (ODS) process has been used to achieve such goal. For this purpose, a new and efficient synthetic composite mesoporous nano-catalyst has been designed by enhancing morphological and mechanical properties of gamma alumina (γ-Al₂O₃) on a carbon nano fiber (CNF) as multiple supports. Four different catalysts based on different amount of CNF have been designed. X-Ray diffraction (XRD), X-Ray fluorescence (XRF), crash strength test, thermal gravimetric examination (TGA), and surface area (BET) have been used to characterize the catalysts. The catalyst with 10% loading of CNF (CAT-3) has been found to increase the tensile strength by more than 200% compared to the CNF-free sample (CAT-4). Then, a series of experiments has been conducted in a batch ODS reactor with air as an oxidant and light gas oil (LGO) as a real feedstock to evaluate the effectiveness of the designed catalysts and the performance of the reactor. The new catalyst has been clearly shown to be a significant factor in sulfur removal resulting in a clean fuel.

The effects of temperature gradient on the formation, composition, and strength of oil deposits were investigated. As the crude oil temperature and the wall surface temperature were lowered, the concentrations of the oil fraction and low-molecular-weight paraffins in the deposits increased; simultaneously, the amounts of resins and asphaltenes declined. In the asphalt–resin–paraffin deposits formed in an asphaltene-free oil sample, cooling led to a rise in the content of resins and a decline in the content of the oil fraction. Model experiments demonstrated that the highest inhibitory capacity with respect to paraffin wax deposition was achieved in the case of 0.5–1.0 wt % asphaltenes being added. This can be attributed to the steric effect of aromatic rings manifested in their ability to disrupt the nucleation of paraffin networks. Therefore, the model wax deposits formed after adding asphaltenes exhibited a lower strength than the samples obtained with the addition of benzene resins and alcohol–benzene resins.

High-wax crude oil was treated with ultrasound (sample weight 50 g, frequency 22 kHz, field intensity 8 W/cm²) for 10 min. The ultrasonic treatment led to an increase in the crude oil viscosity, viscous flow activation energy, specific energy of the break of the disperse system, congealing point, pour point, and precipitate amount and to changes in the precipitate structure. The oil fraction of the crude oil, precipitates, and raffinates was analyzed by IR spectroscopy and chromatography–mass spectrometry. The content of high-molecular-mass n-alkanes in oils from the precipitate of the ultrasonically treated crude oil considerably decreases.

–CoMo sulfide catalysts supported on aluminosilicate halloysite nanotubes (CoMoS/HNT) and on dealuminated halloysite nanotubes (CoMoS/HNT(deAl)) were synthesized by incipient wetness impregnation using pseudoboehmite as a binder. Both the supports and related catalysts were characterized by low-temperature nitrogen adsorption, energy dispersive X-ray fluorescence analysis, temperature-programmed reduction by hydrogen, FTIR spectroscopy of adsorbed pyridine, transmission electron microscopy, and X-ray photoelectron spectroscopy. The catalyst samples were further tested in hydrotreating of diesel feedstocks. Dealumination of halloysite was found to increase the area of Si-enriched surface segments, thus weakening interaction between the sulfide phase and the support and, hence, increasing the content of highly active sulfide particles. In the case of a mixed feedstock, CoMoS/HNT(deAl) + Al₂O₃ achieved a reaction rate constant of 0.605 ppm S^–0.4/g(L^–0.4 h) compared to 0.429 ppm S^–0.4/g(L^–0.4 h) for an alumina-supported sample.

The instability of asphaltenes in crude oils, manifested in their precipitation, is a major production issue that may arise both during the recovery and processing of petroleum feedstocks. The purpose of this study was to investigate the molecular structure of asphaltenes in order to shed light on the causes of their precipitation. To this end, the molecular structures of stable (remaining in the solution) and unstable (precipitated) asphaltenes were characterized by EPR, NMR, and IR spectroscopy. Using crude oil asphaltenes and air-blown asphalt as objects for the study, only weak increasing and decreasing trends were observed in the content of aromatics and oxygenates, respectively, in the unstable asphaltene fraction. The stable and unstable asphaltenes were found to differ in adsorption capacity. It was shown that the species adsorbed on asphaltenes are rich in moieties of aromatic acid esters, and that removing these species further eliminates the structural-group composition differences between stable and unstable asphaltenes. The study findings suggest that the stability of asphaltenes in crude oils can be controlled by introducing synthetic aromatic acid esters structurally similar to natural surfactants.

Comparative studies on transformation of the organic matter (OM) of high-carbon carbonate–siliceous–clay rock with С_оrg 7.07% and low-carbon carbonate rock with С_оrg 0.33% from Domanik deposits in Tatarstan in sub- (SBW) and supercritical (SCW) water were performed. The potential of the carbonate rock is utilized virtually completely in SBW at 320°С. From the high-carbon Domanik rock, SBW allows only more complete extraction of free hydrocarbons, asphaltene compounds, and solid n-alkanes without significantly altering the kerogen structures. The kerogen degradation occurs most intensely in SCW and is accompanied by a decrease in the generation potential and by an increase productive capacity of the rock. In the oil extracted from the high-carbon rock with SCW at 374°С, the content of saturated and aromatic fractions increases by a factor of more than 2, the content of asphaltenes and resins decreases, and carbenes/carboids are formed. At 420°С, the oil yield and the content of carbenes/carboids decrease. In the extraction from the carbonate rock, on the contrary, at 374°С the content of light oil fractions decreases, and the fraction of resins increases by a factor of more than 1.5; at 420°С, the content of asphaltenes increases by a factor of more than 2. Irrespective of the lithological composition of the rocks, with an increase in the SCW temperature, the yield of the gas phase and the content of alkanes, phenanthrenes, and dibenzothiophenes in the oil fractions increase, whereas the content of alkyltrimethylbenzenes, naphthalenes, and dibenzothiophenes decreases. The extent of utilizing the generation potential of OM of Domanik rocks depends on the content and composition of kerogen and high-molecular mass components and on their thermal stability in sub- and supercritical water.