Petroleum Chemistry最新文献

This study investigates the effects of modifying ZSM-5 zeolites with iron and manganese via ion exchange. It focuses on how this modification alters the physicochemical properties of the zeolites and influences the conversion pathway of a n-dodecane/2-methylthiophene (5000 ppm S) feedstock in catalytic cracking. For all modified zeolites, which had SiO₂/Al₂O₃ ratios of 23 and 80 and metal loadings up to 1.94 wt %, the decrease in micropore volume and specific surface area did not exceed the margin of error. The modification of ZSM-5 with either Fe or Mn led to significant improvements, with the SiO₂/Al₂O₃ playing a key role. Acidity, confirmed by NH₃-TPD measurements and quantum-chemical (DFT) simulations, increased in concentration (by 89%) and strength for the zeolite with SiO₂/Al₂O₃ = 23. Catalytic performance was enhanced with both modifier metals and for both zeolites, but more profoundly for the SiO₂/Al₂O₃ = 23 variant: the yield of light olefins increased by 45% (compared to 26% for the SiO₂/Al₂O₃ = 80 zeolite), while the sulfur content in liquid products was reduced by 46% (compared to 33%).

A series of mesoporous Cu-incorporated Al₂O₃-based catalysts were synthesized via the sol–gel method using dodecylamine (DDA) and polyethyleneimine (PEI) as templates. The catalysts were characterized using low-temperature N₂ adsorption–desorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), H₂ temperature-programmed reduction (H₂-TPR), and NH₃ temperature-programmed desorption (NH₃-TPD). A CuO/Al₂O₃ catalyst prepared by wetness impregnation of commercial Al₂O₃ was used as a reference sample. All the samples were reduced and tested in the vapor-phase reductive alkylation of nitrobenzene with methanol (RANM) using a flow-type reactor. With polyethylenimine as a template, the synthesized catalyst possessed ordered cylindrical pores and a specific surface area up to 260 m²/g, whereas the catalyst prepared using dodecylamine had slit pores and a specific surface area of 270 m²/g. The catalytic activity of mesoporous Cu/Al₂O₃ catalysts in RANM was found to strongly depend not only on the Cu loading but also on the shape and volume of the support’s pores.

A series of additives based on an iron-modified MFI zeolite were investigated for their ability to reduce NO_x in cracking catalyst regeneration flue gases. Their efficiency was dependent on the iron loading, the zeolite SiO₂/Al₂O₃ ratio, and the initial cationic form used for modification. The Fe/MFI additives prepared from an NH₄-form zeolite with a low SiO₂/Al₂O₃ ratio (23) demonstrated excellent performance. Under industrially relevant catalyst regeneration conditions, the additive with an optimized iron oxide content (within a tested range of 0.5 to 2.5 wt %) reached a NO_x reduction efficiency of 45.4%.

The effects of two different synthetic dispersants were characterized using two independent optical methods. The study examined their impact on both the aggregation of asphaltenes (isolated from various crude oils using a standard procedure) and the stability of model asphaltene-containing dispersions. In the model n-heptane/toluene medium, the two dispersants had markedly different effects on asphaltene aggregation and dispersion stability. One dispersant failed to disperse asphaltenes because it self-associated into large micelles (≥100 nm in radius) in the n-heptane medium, thereby destabilizing the system. Consequently, a key design criterion for future dispersants and stabilizers should be a molecular structure that minimizes self-association in nonpolar media while maximizing affinity for asphaltenes.

This paper reports on the determination of a stability threshold for an 0.1 g/L asphaltene solution in toluene with the addition of heptane as a precipitant. For this purpose, ultramicroscopy as well as dynamic and static light scattering methods were employed. Ultramicroscopy has never previously been used to determine stability thresholds in petroleum systems. Using the abovementioned experimental methods, an asphaltene aggregation onset point was identified for the tested asphaltene solution, and a time-dependent trend in mean aggregate size was revealed once the stability threshold was exceeded. The study results show that ultramicroscopy enables rapid onset point determination in model petroleum systems of this type and provides higher sensitivity than dynamic or static light scattering; specifically, it can detect lower concentrations of asphaltene aggregates. A single, bulk addition of heptane above the onset point resulted in diffusion-limited aggregation. In contrast, gradual titration past the stability threshold led to a slower process in which the mean aggregate size increased linearly with time.

The equations of viscosity and acid spending capacity characterize the performance of wellhead solvents and fluids, such as gasoil-water wellhead base fluids, and the types of wettability-altering solvents. This study evaluates the properties and interactions in the reservoir layers by deriving the viscosity equations for both oil and water layers. The results from these equations were then applied for the acid spending capacity and overburden pressure equations to demonstrate their role in the damage calculations (water block type) for different rock types. Focusing on the overburden pressure and water block effects, the study investigates the role of viscous and non-viscous chemicals and fluids in both causing and removing damages in various mineral compositions of the porous media. Finally, introducing these new equations, the study outlines key approaches for analyzing and calculating chemical characteristics and behavior in porous media under high-temperature and high-pressure conditions using field and experimental data as the example.

Thermogravimetric analysis (TGA) and differential thermogravimetry (DTG) at varying heating rates revealed distinct kinetic trends for the high-molecular-weight components of a heavy crude oil. The oil was extracted from a Permian reservoir rock sample from the Ashalchinskoye field, and the trends were characterized for both low-temperature (200–350°C) and high–temperature (350–600°C) oxidation regions. The oxidation patterns of a heavy crude oil and its resin–asphaltene components were compared, for the first time, after hydrothermal pretreatment of the rock at 300°C in a carbon dioxide atmosphere in the presence of a composite catalyst based on transition metals. The effects of adding the catalyst to the heavy-crude-oil-containing reaction system on the physicochemical properties of the heavy oil and on the oxidation rate of its components were identified. For resins, the thermo-oxidative effect was pronounced most strongly in the low-temperature oxidation range, whereas for asphaltenes the most significant alterations and mass losses were observed in the high-temperature oxidation region. Based on the kinetics obtained, the activation energies were calculated both for the hydrothermal and catalytic treatment.

Flexible pavements become significant structural elements, which are really vulnerable to the probable damage resulting from various traffic loads and an aggressive environment. In order to bolster the structural strength and prolong the life of pavements, reinforcement layers have been included in the design of most roads and highways. In this research, which is based on numerical simulations, the behavior of flexible pavement with respect to varying loads and with different reinforcement layers will be analyzed. The main objectives of this article are to develop a pavement layers model by utilizing finite element software, which is ABAQUS software package, evaluate the influence of different geogrid properties, location on the induced deformation, stresses, and strains into pavement layers and evaluate the influence of different loading values considering low, medium, and high traffic axle loads. The study reveals that stress on flexible pavements is directly proportional to load force, with stresses reaching 777 KPa at 44 KN and 1390 KPa at 80 kN. Deformations vary, with values ranging from 0.00307 mm at 44 KN to 0.00946 mm at 133 kN.

This study compares the kinetics of key non-catalytic processes—thermal pyrolysis, partial oxidation, steam reforming, and dry reforming—for methane and C₂₊ hydrocarbon conversion at 1400–1800 K, highlighting both common and distinct behavioral trends. The first oxidative conversion step differs markedly between methane and its heavier homologues. Methane conversion is primarily driven by its reaction with oxygen, with both reactants being consumed synchronously. In contrast, even in the presence of oxygen, C₂₊ hydrocarbons initially undergo thermal pyrolysis—a more rapid process under these conditions—before participating in slower oxidative reactions with O₂, H₂O, or CO₂. The main oxidation reactant is ethylene, a compound produced through thermal pyrolysis of C₂₊ hydrocarbons: it reacts with O₂ to form CO and H₂O. All C₂₊ hydrocarbons show comparable O₂ conversion rates during non-catalytic partial oxidation—significantly higher than those observed for methane. Once oxygen has been fully consumed, further hydrocarbon conversion proceeds with slower reactions, primarily involving CO, C₂H₂, and CH₄. In this reaction zone, H₂O serves as the primary conversion agent, along with CO₂ when present. These reactions substantially boost the H₂ content in the syngas.

The paper reports the ¹H NMR characterization results for the products of rac-Et(2-MeInd)₂ZrMe₂ activation by diisobutylaluminum aryloxide 2,6-^tBu₂PhO-)AlⁱBu₂ (hereinafter referred to as AlⁱBu₂(OAr)), with and without olefins (1-hexene/ethylene/propylene). The olefin-free reaction between the catalyst and AlⁱBu₂(OAr) caused the decomposition of dimethylated zirconocene with liberation of methane and isobutene, likely due to the formation of a cationic complex [rac-Et(2-MeInd)₂ZrMe]⁺[MeAlⁱBu₂(OAr)]^–, unstable at room temperature. In the presence of 1-hexene, rac-Et(2-MeInd)₂ZrMe₂ was effectively activated by diisobutylaluminum aryloxide to generate a catalytically active intermediate with a growing polymer chain—[rac-Et(2-MeInd)₂ZrCH₂CH(ⁱBu)Pol]⁺· [MeAlⁱBu₂(OAr)]^–—and to form polyhexene. After complete depletion of hexene-1, the working catalyst was deactivated with the formation of rac-Et(2-MeInd)₂Zr(H)CH₂CH(ⁱBu)Pol, MeAlⁱBu(OAr), and isobutene. In the presence of ethylene and propylene, the ¹H NMR signals of the olefins weakened over time, and insoluble polymer particles accumulated on the tube walls. A reaction mechanism was proposed for the rac-Et(2-MeInd)₂ZrMe₂/AlⁱBu₂(OAr) system, accounting for pathways both with and without olefins.