Petroleum Chemistry最新文献

The extractive desulfurization of the light vacuum gas oil has been investigated in a mini-channel reactor. The influence of operating and geometrical parameters of mini-channel on the flow pattern of two immiscible phases and efficiency of a sulfur extraction from a petroleum product has been studied. Using N-methyl-2-pyrrolidone as a solvent, it was possible to remove up to 50% of sulfur from light vacuum gas oil in a mini-channel within 20–50 s. The extraction efficiency of benzo- and dibenzothiophene homologues from petroleum feedstock was investigated in mini-channels of various internal diameter (0.5, 1, and 1.6 mm) and length (from 10 to 300 сm) within the range of total flow velocities of 0.01–0.1 m/s. Different flow configurations (slug, slug-drop, annular, wavy annular) were observed in the mini-channel. It was shown that the values of a sulfur extraction efficiency for the slug and annular flow regimes were close for the same retention time. However, compared to the slug flow, the volumetric mass transfer coefficient for the annular flow regime decreased significantly as the mini-channel length (retention time) increased. In total, 75% of sulfur compounds can be extracted from light vacuum gas oil by a multi-stage extraction in a mini-channel.

The paper investigates the effects of the salinity and pH of an aqueous phase, as well as the influence of asphaltene content in crude oil, on emulsification—specifically on the formation of an interfacial layer and the stability of emulsion. The oil–water interfacial tension, water droplet size, and emulsion stability were characterized using the bottle test method. The oil–distilled water interfacial tension in emulsions varies widely. Compared to distilled water, emulsions with high-salinity reservoir waters are distinguished by high stability and a lower interfacial tension. Asphaltenes that are concentrated in the interfacial layer of an emulsion with high-salinity reservoir water have a higher molecular weight than asphaltenes of crude oils and of emulsions with distilled water. Elemental analysis and IR spectroscopy show an increase in sulfur content in asphaltenes adsorbing at the oil–distilled water interface, and an increase in oxygen content in asphaltenes from emulsion with high-salinity-waters.

The study describes an esterification process for the synthesis of ethylene glycol (EG) monoesters of synthetic petroleum acids (SPAs) in the presence of a heterogeneous catalyst based on a commercial coarse-dispersed anatase TiO₂. The proposed method provides selective synthesis of monoesters in 89 wt % yield without the need for additional treatment of the desired product. The monoester was tested as a plasticizer for cellulose acetate butyrate (CAB) and as an antioxidant additive for diesel fuels. It is shown that the plasticizing properties of this monoester are comparable to those of a commercial dibutyl sebacate commonly used for CAB plasticization. Moreover, in terms of specific impact toughness of CAB at subfreezing temperatures, the synthesized monoester exceeds the commercial plasticizer by more than 35%. Introducing 0.004 wt % of this monoester into a hydrotreated diesel fuel enhances the thermo-oxidative stability of the fuel by a factor of over ten.

A series of catalysts were obtained by dealumination of an HZSM-5 zeolite followed by modification with neodymium and/or boron. These samples were tested in the conversion of methanol to hydrocarbons to enhance selectivity towards C₂–C₄ olefins, and especially towards propylene. X-ray diffraction analysis, low-temperature nitrogen adsorption, and ammonia temperature-programmed desorption were employed to characterize the acidic properties and microporous structure of the modified catalysts. The methanol conversion was carried out in a plug-flow fixed-bed reactor at atmospheric pressure and temperatures of 250–550°C in a nitrogen flow. It is shown that dealumination and bimetal modification significantly increase the mesopore volume, facilitate the dispersion of the modifier’s particles on the external surface and in the pores of the zeolite, and markedly reduce the density of strong acid sites. The highest selectivity towards C₂–C₄ olefins (82.3%) and the highest propylene selectivity (52.4%) were achieved at 500°C in the presence of the bimetal-modified dealuminated catalyst (4%Nd-4%B-DHZSM-5). The high selectivity towards light olefins and propylene are attributed to the fact that dealumination and bimetal modification provide a significant increase in the ratio of mesopore volume to total pore volume and a reduction in the density of strong acid sites.

The catalytic performance (activity and selectivity) of a FAU-type hierarchical NaY_h zeolite, as well as of a series of modified samples, was investigated in the homocondensation of acetone. The modified samples were prepared from NaY_h by ion exchange of Na⁺ for cations of alkali (Li⁺, K⁺), alkaline-earth (Ca²⁺, Mg²⁺), transition (Co²⁺, Ni²⁺), and rare-earth (La³⁺) metals, as well as by decationation (H-NaY_h, HY_h). The predominantly acidic zeolites (Ca-NaY_h, Mg-NaY_h, Co-NaY_h, Ni-NaY_h, La-NaY_h, H-NaY_h, and HY_h) promoted the formation of acetic acid and mesitylene even at 250°C. The zeolites that contained alkali metal cations (Na⁺, Li⁺, and K⁺) exhibited activity only when the temperature was elevated. Starting from 350°C, NaY_h and Li-NaY_h promoted the formation of acetic acid. In contrast, the performance of K-NaY_h under heating was characterized by the absence of acetic acid formation and a smooth increase in the selectivity towards isophorone (up to 23%) and mesitylene (up to 18%). Over the range of 400–450°C, in the presence of K-NaY_h, secondary isophorone transformations were intensified, resulting in the formation of 3,5-xylenol as the main product with a selectivity of 32%.

Constant growth of industry demand for rare earth elements (REE) makes it urgent to develop more efficient approaches to their production not only from mineral ores, but also from secondary sources. Thus, promising alternative sources of REE are their aqueous solutions, such as, for example, wastewater from hydrometallurgy, leaching solutions of metallurgical slags, acidic effluents of mine drainage, acidic solutions formed during recovery of valuable elements from microelectronic boards and magnets. Membrane methods of separation of liquid media allow both concentration of the sum of REEs and, most importantly, isolation of individual REEs. This review focuses on a variety of membrane methods applicable to REE recovery. It includes a brief description of the principle of each type of membrane separation and summarizes information on the use of each specific method for solving REE extraction problems. In addition, the review considers some methods of modeling of REE membrane separation, which is important due to the presence of dozens of parameters on which the final efficiency of the developed membranes depends.

Ultrasonic treatment (UST) of a 30 wt % heavy oil emulsion of distilled water was shown to depress the water droplet dispersion, emulsion viscosity, and the specific fracture energy of the dispersed system. The interfacial layer extracted from the sonicated emulsion had a lower content of resins and a higher content of asphaltenes than the interfacial layer of the initial emulsion. After the UST, the resins of the interfacial layer exhibited a higher concentration of oxygenated moieties, and the average asphaltene molecule had a lower number of sulfur, oxygen, and carbon atoms in its aliphatic moieties.

A series of tandem catalysts based on indium, zinc, and gallium oxides were synthesized, with a CHA-type silicoaluminophosphate and an MFI-type zeolite as acidic components. These catalysts were tested in the conversion of carbon dioxide to olefins at 380°C and 27 bar, with the component arrangement being varied. The physicochemical properties of the catalysts and their components were characterized by low-temperature nitrogen adsorption, X-ray diffraction analysis (XRD), X-ray fluorescence spectrometry (XRF), scanning electron microscopy (SEM), and temperature-programmed desorption of ammonia (NH₃-TPD). It is shown that the optimal arrangement of the hydrogenating and acidic components in the reactor depends on the type of the hydrogenating component. The best catalytic performance (33% CO₂ conversion and 5.6% yield of hydrocarbons) was achieved in the presence of a ZnGa₂O₄/MFI catalyst with the components being mechanically mixed.

This study is related to the preparation of an environmentally friendly ZSM-5 zeolite catalyst from waste materials for the process of diesel desulfurization. This material was tested for catalytic performance under different conditions including variations in the temperature, initial sulfur concentration (IC), and reaction time. The optimized synthesis at a temperature of 170°C and crystallization time of 96 h yielded ZSM-5 zeolite with a high BET (Brunauer, Emmett, and Teller) surface area and excellent thermal stability. The SnO₂ addition further enhanced the catalyst performance without changing its structure. Desulfurization experiments were performed using a green oxidizer, hydrogen peroxide (H₂O₂), at four different temperatures, namely, 25, 50, 75, and 100°C, and at three sulfur concentrations (300, 450, and 600 ppm). The obtaned results showed that sulfur removal efficiency increased as the temperature, IC, and reaction time increased, reaching the maximum (93.33%) at 100°C, IC equal to 600 ppm, and reaction time of 100 min. Thus, SnO₂-modified ZSM-5 was shown to be an environmentally friendly and highly active catalyst for the diesel desulfurization processes under adjusted precise reaction conditions.

Single-atom catalysts (SACs) are the latest generation of nanoheterogeneous catalysts. They consist of active metal sites dispersed into single atoms on the surface of a solid support and, thus, exhibit unique catalytic performance including enhanced activity and high selectivity. Semiconductor materials are used to prepare single-atom photocatalysts designed for photo-driven chemical processes, generally without external heating. Photoinduced low-temperature methane conversion over SAC-based photocatalysts offers new prospects for methane chemistry. This review summarizes, systematizes, and analyzes recent publications on dry reforming of methane (DRM) and nonoxidative coupling of methane (NOCM) in the presence of single-atom photocatalysts. Despite the unfavorable thermodynamics of these types of reactions over wide ranges of low and high temperatures, they can be carried out at room temperature under photocatalytic conditions. The review discusses the performance of SACs in photoinduced DRM and NOCM compared to heterogeneous nanocatalysts. It further provides a comparative assessment of the SAC behaviors in DRM and NOCM under photocatalytic and conventional thermocatalytic conditions.