Gubkin Russian State University of Oil and Gas

The effect of cobalt acetylacetonate (Co(acac)2) on heavy oil oxidation under in-situ combustion (ISC) conditions was investigated using DSC, TG, XRD, and SEM analyses. The results show that the compound does not behave as an active catalyst at low temperature but instead undergoes thermal decomposition as temperature increases. Around 350 degrees C, close to the transition between low-temperature oxidation (LTO) and high-temperature oxidation (HTO), an oxide-based Co3O4 phase is formed. This change in state is reflected in the oxidation behavior. Only a limited variation is observed in the LTO region, where the peak shifts slightly toward higher temperature, while a much stronger effect appears in the HTO region. In this stage, the apparent activation energy decreases from 150.602 to 101.357 kJ/mol, indicating that the main catalytic contribution occurs at elevated temperatures. SEM observations show that the decomposition process leads to the formation of particles in the nanometer range, mostly between 40 and 80 nm. Although no direct correlation is established, such dimensions are generally associated with increased surface accessibility and may contribute to the observed enhancement in high-temperature oxidation. Overall, the results suggest that the catalytic effect is governed by the thermal evolution of the precursor rather than its initial form. This temperature-dependent activation results in a differential effect across oxidation stages, with limited influence on LTO and a more pronounced effect on HTO. This differential response is favorable for heat release and may improve combustion stability under ISC conditions. The study provides a basis for further investigation of oil-soluble precursors as controllable catalytic systems in thermal recovery processes.

The development of hierarchical SAPO-11 catalysts typically relies on expensive synthetic mesoporogens or post-synthetic treatment that compromise structural integrity. Herein, we present a novel, cost-effective mesoporogen-free strategy for synthesizing hierarchical SAPO-11 by exploiting halloysite nanotubes (HNTs) as a dual-function precursor, serving simultaneously as a source of silicon and aluminum and as a template for secondary porosity. Hydrothermal synthesis conditions (180-200 degrees C, 48-72 h) were optimized to leverage HNTs' inherent mesoporosity and chemical composition, yielding SAPO-11 with high crystallinity, moderate acidity and enhanced textural properties. Characterization by XRD, SEM, TEM, nitrogen sorption, Py-IR and NH3-TPD confirmed the hierarchical porosity (mesopore volume up to 54 %) and controlled acidity, attributed to pseudomorphic transformation of HNTs during synthesis. Pt-loaded catalyst supported on hierarchical SAPO-11 demonstrated higher platinum dispersion and catalytic efficiency, achieving a C16-isomers yield of 80 % under optimized conditions (380 degrees C, 3.5 MPa H2, LHSV 4 h-1, H2/feedstock volume ratio 500 nL & times; L-1), outperforming conventional SAPO-11 and other hierarchical counterparts. The hierarchical structure facilitated diffusion of multi-branched isomers, reducing cracking byproducts (cracking/isomerization ratio of 0.29 vs. 0.43 for conventional SAPO-11). Furthermore, stability tests over 500 h on stream confirmed the catalyst's resistance to deactivation, attributed to its hierarchical porosity, mild acidity, and optimal metal-acid balance. This mesoporogen-free approach offers a scalable, eco-friendly route to high-performance catalysts that provide activity, selectivity, and stability while leveraging abundant natural resources.

The hydroisomerization of long-chain paraffins, such as n-C16, is a key process for improving the low-temperature properties of diesel fuels. However, the understanding of how the zeolite pore structure and the balance between acid and metal sites determine the efficiency of this process remains incomplete. This work is dedicated to the synthesis and investigation of Pt/ZSM-23 and Pt/ZSM-48 catalysts in n-hexadecane isomerization and diesel fuel hydroisodewaxing. A kinetic investigation of the model feedstock hydroisomerization was conducted at low conversion levels, with a focus on product distribution and structure–property correlations. A detailed analysis was performed on the yield of mono- and multibranched isomers, cracking products and fuel quality indicators (e.g., CFPP, cetane index). Pt/ZSM-23 demonstrated higher isomer selectivity at lower temperatures and a greater degree of proximity between metal and acid sites, whereas Pt/ZSM-48 exhibited increased cracking at elevated temperatures, consistent with its acidity tending towards the stronger type and distinct pore architecture. The kinetic analysis accounted for competing reaction pathways proceeding via carbenium ion intermediates on acid sites and dehydrogenation/hydrogenation reactions on Pt, emphasizing the role of spatial constraints and acid site strength in governing the rates of elementary steps. The prepared catalysts ensured high yields of isomers in the diesel fuel range with significantly reduced cloud points and acceptable density/cetane index values, confirming the potential of using specially designed Pt/zeolite systems for improving diesel fuel quality. This work deepens the understanding of the hydroisomerization mechanism on one-dimensional zeolites and establishes a foundation for the development of catalysts for diesel fuels hydroisodewaxing.

New challenges are emerging for improving desulfurization technologies due to the introduction of heavy oil feedstock into fuel energy. In this work, catalysts based on Fe, Co, Mn and Bi molybdates are tested in the process of aerobic oxidation of sulfur-containing compounds of the thiophene series in an alkane medium. The catalysts are characterized by a set of physicochemical methods: XRD, FTIR, TGA, low-temperature nitrogen adsorption-desorption, SEM, TEM, NH3-TPD, H2-TPR, XPS. A comparative assessment of the catalytic activity of the obtained molybdates in the oxidation reaction of a model mixture of dibenzothiophene (DBT) in dodecane with air is carried out. It is shown that iron molybdate has the highest activity, in which an important role is played by excess molybdenum in the form of trioxide MoO3. In the presence of a biphasic catalyst, 100 % conversion of DBT is achieved in 15 min at 170 degrees C. The specific activity is 172 mmol*g-1*h-1 (170 degrees C, 10 min). A possible reaction mechanism based on the activation of O2 and the generation of active species in the presence of the Fe3+/Fe2+ redox couple, and the oxidation of the sulfur substrate at molybdenum sites has been proposed. The high efficiency of the catalyst is confirmed by the results of aerobic oxidative desulfurization of non-hydrotreated vacuum gas oil with a high sulfur content (18 000 ppm), achieving more than 85 % desulfurization degree.

We comprehensively analyzed the influence of nonlinear reservoir processes on well flowrate vs. drawdown for low permeability reservoirs with hard-to-recover (HTR) hydrocarbon reserves. New nonlinear relationships between the flowrate of low permeability reservoirs and reservoir drawdown (indicator curves) were identified. The nonlinearity of the indicator curves is due to the combined effects of nonlinear filtration, technogenic reservoir change, and the dependence of formation damage parameters on drawdown. The applied approach allowed us to find out qualitatively new regularities in the relationship between flowrate and drawdown in low permeability reservoirs. A well productivity analysis revealed hysteresis in the indicator curves and a shift in critical drawdown values when considering both formation damage and filtration nonlinearity. It has been found that the combined effects of nonlinear filtration and damage effects lead to an additional flowrate decline of 25-40%, as compared to separately considering each of these effects. The obtained results are of practical importance for optimizing the development of low permeability reservoirs with HTR reserves and for predicting their productivity.