Kazakhstan journal for oil & gas industry

2707-42262957-806X

KMG Engineering

108984

10.54859/kjogi108984

CATALYTIC ISOMERIZATION OF LIGHT ALKANES: THERMODYNAMIC, KINETIC, AND TECHNOLOGICAL ASPECTS

Orazbayev

Nurkhan Samatuly

магистрантnurkhan7allmight@gmail.comhttps://orcid.org/0009-0000-7097-989XSeitenova

Gaini Zhumagaliyevna

Candidate of chemical sciences, professorgainiseitenova@gmail.comhttps://orcid.org/0000-0001-6202-3951

Л.Н.Гумилев атындағы Еуразия ұлттық университетіL.N. Gumilyov Eurasian National University82

06052026

25052026

The gradual tightening of environmental standards, combined with growing global demand for environmentally friendly fuels, has significantly increased the importance of cutting-edge technologies in oil refining. In this context, the catalytic isomerization of light alkanes (C4-C6 fraction) is one of the most strategic processes for improving gasoline quality without increasing the concentration of aromatic hydrocarbons or adding hazardous additives. From a chemical standpoint, this process promotes the structural rearrangement of linear paraffins into corresponding branched isomers, which possess a higher octane rating. This results in a significant improvement in the fuel’s combustion characteristics, while reducing the formation of environmentally harmful emissions. This review systematically examines the fundamental principles underlying the isomerization of alkanes. Particular attention is given to the reaction mechanism, which proceeds via carbocationic intermediates at acidic catalytic centers, reflecting the classic scheme of acid-catalyzed hydrocarbon transformations. Furthermore, the thermodynamic constraints determining the equilibrium distribution of isomers, as well as the kinetic parameters that determine the reaction rate, product selectivity, and overall process efficiency, are critically analyzed. Particular attention is given to bifunctional catalytic systems, which combine metal and acid functional groups, thereby enabling the simultaneous execution of the hydrogenation-dehydrogenation and backbone isomerization steps. The role of competing side reactions, notably hydrocracking and aromatization, is also addressed due to their influence on product yield and catalyst stability. Beyond theoretical considerations, this review examines the complexities inherent in real industrial systems. In practice, the attainment of thermodynamic equilibrium is often limited by kinetic constraints, resistance to mass transfer within particles and between phases, as well as by the gradual deactivation of the catalyst due to coke formation or poisoning. These factors require a more detailed understanding of process behavior under industrial operating conditions.

catalytic isomerization, light alkanes, hydroisomerization, bifunctional catalysts, carbocation mechanism, thermodynamic equilibrium, reaction kinetics, zeolite catalysts, catalyst deactivation, octane number enhancement.

Introduction. Over the past few decades, the global oil refining industry has undergone profound changes, driven by increasingly stringent environmental regulations and growing demand for high-quality, high-performance fuels. One of the primary missions of modern refineries is to produce high-octane gasoline while minimizing the concentration of environmentally harmful components, particularly aromatic hydrocarbons, sulfur compounds, and leaded additives [1]. In this context, the catalytic isomerization of light paraffins has become a process of crucial technological importance. This process converts low-octane normal alkanes into their branched structural isomers, which exhibit better anti-knock properties and thus help improve engine performance and fuel efficiency. Unlike catalytic reforming, isomerization does not lead to the intensive formation of benzene or other toxic aromatic compounds, making it a more environmentally friendly method for improving gasoline quality [2]. Light naphtha fractions, particularly those containing C4-C6 hydrocarbons, are the optimal feedstock for isomerization processes. These fractions are abundant in crude oil and can be effectively upgraded through intramolecular rearrangement without altering their general molecular formula. Consequently, isomerization plays a key role in increasing the yield of high-octane components intended for blending in modern refining concepts [3]. From a fundamental perspective, the isomerization of alkanes constitutes a complex catalytic system, determined by the interaction between thermodynamic constraints, reaction kinetics, and catalyst functionality. The reaction mechanism generally involves carbocationic intermediates formed at active acid sites and comprises a sequence of elementary steps, including hydride shifts, skeletal rearrangements, and reversible hydrogenation-dehydrogenation reactions. At the same time, competing side reactions such as hydrocracking and aromatization may occur, which impairs selectivity and complicates process optimization [4]. Another important factor is the discrepancy between theoretical and practical process values. Although thermodynamic analysis determines the upper limit of the isomer yield that can be achieved, actual industrial results are often limited by kinetic constraints, diffusion and mass transfer resistances, as well as catalyst deactivation phenomena due to coke deposits or poisoning. To achieve optimal operating conditions, it is therefore necessary to carefully and systematically harmonize the reaction parameters, catalyst design, and reactor configuration [5]. In recent years, both in scientific research and in industrial practice, there has been an increasing use of advanced mathematical modeling and simulation methods to gain a deeper understanding of isomerization systems. These tools facilitate the prediction of equilibrium compositions, the elucidation of reaction pathways, and the accurate modeling of industrial plant performance under various operating conditions. For this reason, this review aims to provide a comprehensive analysis of the thermodynamic, kinetic, and catalytic properties of light alkane isomerization, as well as a critical evaluation of modern technological approaches and the key challenges associated with their large-scale industrial implementation [6]. Consequently, studies devoted to the systematic optimization of industrial isomerization plants remain relatively rare in the available scientific literature. This is primarily due to the difficulty of developing rigorous kinetic models, which are a fundamental component of any reliable optimization scheme for isomerization reactors. Creating such models requires a detailed consideration of extensive reaction networks, as well as the inclusion of catalytic and transport phenomena, which significantly complicates their practical implementation [7]. A number of previous studies have approached this problem from various methodological perspectives. For example, Besl et al. presented a brief assessment of the optimization of the Penex isomerization process at a German refinery, thereby offering one of the first practical insights into process improvement on an industrial scale. However, their work was primarily focused on applied aspects and did not include a detailed mechanistic interpretation of the underlying reaction pathways [8]. In contrast, Dudley and Malloy proposed a simplified kinetic model that accounts only for the main reaction pathways, namely isomerization and cracking. This model was applied to optimize the process using a liquid aluminum chloride (AlCl₃)-based catalytic system and demonstrated that reduced-order kinetic models can still serve as effective tools in process development and optimization [9]. Akhari et al. investigated the effect of feed composition, specifically the presence of methylcyclopentane, on isomerization yield using process simulation in HYSYS. In addition, they conducted experimental studies on the effect of hydrogen partial pressure on the activity of Pt-mordenite zeolite-based catalysts and on the conversion of n-paraffins. Based on these results, kinetic equations were proposed for the conversion of C5 and C6 hydrocarbons [10]. Further experimental work by Brito et al. focused on Pt-Ni/mordenite catalysts with various metal ratios. Their results showed that the composition of the metal phase has a significant effect on catalytic activity and selectivity. In addition, a kinetic model was developed to describe the catalyst’s behavior during deactivation, which is crucial for assessing the catalyst’s long-term stability [11]. Konchag et al. developed a kinetic model of C5-C6 isomerization on Pt/zeolite H catalysts under conditions typical of industrial production, which improved the reliability of process modeling when applied at the refinery scale [12]. Surla et al. proposed an event-driven approach to kinetic modeling to describe C5-C6 isomerization on chlorinated aluminum oxide-based catalysts. This methodology provides a more detailed mechanistic description of the elementary reaction steps and allows for a deeper understanding of complex networks of catalytic reactions [13]. Most recently, Chekantsev et al. proposed a comprehensive kinetic model applicable to the three main classes of isomerization catalysts. Their reaction network includes 36 elementary steps, providing a highly detailed view of the system. The study showed that, although the overall reaction rates are comparable for different types of catalysts, there are significant differences at the level of individual isomerization pathways. It is important to note that the model agrees well with experimental data for all the catalytic systems studied, which confirmed its validity and reliability [14]. <ol> <li> Fundamentals of Alkane Isomerization. Alkane isomerization is a fundamental class of transformations in hydrocarbon chemistry, which involves the rearrangement of the carbon skeleton while maintaining the molecular formula. In the context of petroleum refining, this process predominantly refers to the conversion of linear (conventional) alkanes into their branched (ISO) counterparts. Despite its apparent structural simplicity, this transformation is determined by the complex interaction of molecular structure, energy factors and catalytic effects. Conventional alkanes have a relatively low chemical reactivity, which can be explained by the presence of strong σ bonds (C-C and C-H) and the absence of functional groups or π-systems. In terms of molecular orbitals, their highest occupied molecular orbitals (HOMO) are characterized by low energy levels, while the lowest unoccupied molecular orbitals (LUMO) remain energetically inaccessible under mild conditions. This electronic configuration explains its inherent inertia, which requires the use of highly active catalytic systems capable of generating reactive intermediates to initiate the isomerization process [15].</li> </ol> The thermodynamic driving force of alkane isomerization is due to the difference in the stability of the linear and branched isomers. Branched alkanes tend to be thermodynamically more stable due to the combined effect of hyperconjugation and the electron-donating inductive effect of the alkyl substituents. This higher stability is directly related to a higher compression ignition resistance, which leads to a higher octane number and better fuel efficiency. From a constructive point of view, the degree of branching plays a decisive role in determining the quality of fuel. Single-stranded isomers, such as methylpentanes, generally have a moderate octane number, while more branched structures, including dimethylbutanes, have significantly higher anti-knock properties. Therefore, industrial isomerization processes are designed not only to facilitate the conversion of n-alkanes, but also to selectively promote the formation of highly branched isomers [16]. Isomerization is particularly relevant for light hydrocarbons in the C4-C6 range, which make up a significant part of the light naphtha fluxes. Due to their relatively simple molecular structure, these compounds undergo efficient structural adaptation under catalytic conditions, which makes them an ideal raw material for increasing the octane number. In addition, light alkanes, in contrast to heavier hydrocarbons, are able to approach thermodynamic equilibrium under correspondingly optimized process conditions. An additional feature of alkane isomerization is its reversible nature. The reaction takes place in a thermodynamic equilibrium state, the final distribution of the isomers being determined mainly by temperature and, to a lesser extent, by pressure. As a result, the composition of the product is determined not only by kinetic factors, but also by equilibrium constraints [17]. In industry, isomerization is usually integrated with other refining processes such as hydrogen treatment and fractionation to improve the overall efficiency of the process. Before isomerization, the raw materials are usually subjected to purification steps to remove catalytic chemical agents, including sulfur- and nitrogen-containing compounds, as well as moisture, which can negatively affect the catalytic activity and stability. Therefore, alkane isomerization is a key to improving Moderna petroleum refining by combining the basic principles of physical chemistry with advanced technological processes that enable cleaner fuels with a higher octane number [18]. <ol start="2"> <li> Mechanism of Catalytic Isomerization. The catalytic isomerization of alkanes is a mechanically complex multiphase process that occurs due to the formation of highly reactive intermediates and involves the synergistic contribution of acid-catalyzed and metal-catalyzed transformations. The reaction mechanism is most often interpreted within the framework of carbocation chemistry (carbene ion chemistry), which provides a consistent theoretical basis for describing not only the desired skeletal rearrangements, but also the formation of undesirable by-products [19].</li> </ol> In industrial conditions, alkane isomerization is usually carried out in bifunctional catalytic systems containing both metallic and acidic active centers. These functions perform complementary and interdependent functions across the entire reaction network. In particular, the metal component promotes reversible hydrogenation-dehydrogenation steps, which allow the formation of reactive olefin or carbocation precursors, while acidic centers contribute to structural restructuring through the formation and transformation of carbocation intermediates. Effective cooperation between these two types of active centers is a critical factor for the catalytic activity, selectivity, and overall efficiency of the process [20]. <ul> <li> Formation of Reactive Intermediates. The initial stage of the isomerization mechanism involves the activation of a relatively inert alkane molecule, which is an important kinetic barrier in the overall process. In bifunctional catalytic systems, this stage usually begins with the active metal centers, where the alkane is dehydrogenated to form alkenes or intermediates bound to the surface. The formation of this unsaturated intermediate is important because it significantly increases the reactivity of the molecule and ensures its subsequent participation in acid-catalyzed transformations [21].</li> </ul> After the formation of the alkaline intermediate, it moves to the acidic active center, where it is protonated, resulting in the formation of a carbenium ion. This positively charged intermediate plays a central role in the isomerization mechanism because it provides the electronic and structural flexibility needed to rearrange carbon-carbon bonds. In systems characterized by an exceptionally high acid content, such as superacid media, an alternative activation pathway may be used. In such cases, carbocations can be formed directly by separating the hydride from the alkane, avoiding the intermediate stage of alkene formation. Regardless of the specific pathway, the formation of carbenium ions is a critical mechanical step, since it provides a subsequent restructuring of the skeleton, which leads to the formation of branched isomers [22]. 2.2 Skeletal Rearrangement. Once generated, the carbenium ion undergoes a sequence of structural rearrangements through a series of elementary transformations. The most significant among these are 1,2-hydride shifts and alkyl shifts, involving the migration of methyl or larger alkyl groups along the carbon framework. These intramolecular rearrangements result in the progressive stabilization of the carbocation, generally following the well-established stability order: primary secondary tertiary [23]. From a mechanistic standpoint, two principal types of rearrangements are typically distinguished. Type A rearrangements involve relatively straightforward hydride or alkyl shifts and proceed at comparatively high rates due to their lower activation barriers. In contrast, Type B rearrangements are associated with the formation of more highly branched structures and often proceed via non-classical intermediates, such as protonated cyclopropane-like species. These pathways are usually more complex but are essential for generating isomers with superior structural branching. The intrinsic tendency of carbocation intermediates to evolve toward more thermodynamically stable configurations serves as the primary driving force for skeletal rearrangement. As a result, the reaction network ultimately favors the formation of highly branched isomers, which are both energetically preferred and technologically desirable due to their enhanced fuel properties [24]. 2.3 Chain Propagation and Product Formation. After rearrangement, the carbocation undergoes a hydride transfer from another alkane molecule. This step produces the final branched alkane and simultaneously generates a new carbocation, allowing the reaction to proceed as a chain process. In bifunctional catalysts, the final step involves hydrogenation of the intermediate species on metal sites, ensuring the formation of stable saturated hydrocarbons and preventing excessive accumulation of olefins [25]. 2.4 Side Reactions. Following skeletal rearrangement, the carbenium ion undergoes a hydride transfer reaction with a neighboring alkane molecule. This step results in the formation of the final branched alkane product while simultaneously generating a new carbocation species, thereby sustaining the reaction through a chain-type propagation mechanism. In bifunctional catalytic systems, the final step involves hydrogenation of intermediate species on metal sites, ensuring the formation of stable saturated hydrocarbons and preventing excessive accumulation of olefinic compounds, which could otherwise lead to catalyst deactivation [26]. 2.5 Role of Catalyst Structure. The mechanism of alkane isomerization is strongly governed by the physicochemical properties of the catalyst, which determine both activity and selectivity of the process. In particular, the most influential parameters include: (i) the strength and density of acid sites responsible for carbocation formation and rearrangement, (ii) the dispersion and intrinsic activity of metallic sites involved in hydrogenation–dehydrogenation steps, and (iii) the pore architecture of the catalyst, which imposes diffusion constraints and shape-selective effects on reactant and intermediate species. For instance, zeolite-based catalysts provide well-defined microporous structures that create shape-selective environments, thereby favoring the formation of specific branched isomers with higher thermodynamic and kinetic accessibility. In contrast, superacid catalytic systems exhibit extremely high proton-donating ability, resulting in enhanced intrinsic reaction rates; however, they often suffer from reduced selectivity and lower long-term stability due to non-selective secondary reactions and accelerated deactivation phenomena [27]. <ol start="3"> <li> Equilibrium Limitations in Real Systems. In the catalytic isomerization of light alkanes, thermodynamic equilibrium plays a fundamental role in determining the theoretical upper yield limit of the branched isomer. However, in real industrial systems, the observed product distribution often differs significantly from the equilibrium composition due to a combination of kinetic constraints, transport phenomena, and catalytic constraints. Therefore, thermodynamic equilibrium should be considered as an idealized reference state, and not as a condition achievable during operation [28].</li> </ol> From a thermodynamic point of view, the isomerization of n-alkanes into iso-alkanes is a reversible and moderately exothermic process. At relatively low temperatures, the equilibrium position shifts towards the formation of highly branched isomers, which exhibit greater thermodynamic stability as a result of increased molecular compactness and lower Gibbs free energy. On the contrary, with increasing temperature, the equilibrium composition gradually shifts towards less branched or even linear species, which is consistent with the Le Chatelier principle. This internal thermodynamic behavior determines the optimal temperature regime for industrial operation. The relationship between reaction temperature and isomerization conversion is illustrated in Figure 1. As can be seen, at lower temperatures the process is predominantly limited by reaction kinetics, whereas at higher temperatures thermodynamic equilibrium becomes the main limiting factor. The optimal operating temperature corresponds to the maximum achievable actual conversion under industrial conditions. Figure 1. Effect of reaction temperature on actual and theoretical conversion in light alkane isomerization Despite the favorable equilibrium position at low temperatures, industrial operation in such conditions is impossible due to serious kinetic limitations. Sufficient activation energy is required for the formation of carbenium ion intermediates, and at low temperatures, the rate of their formation is significantly reduced. As a result, the system may remain far from equilibrium, even when thermodynamic conditions favor the formation of branched isomers. This discrepancy between the thermodynamic driving force and kinetic availability is a key limitation in practical isomerization reactors [29]. The limitations of mass transfer are another critical factor contributing to the deviation from equilibrium. In heterogeneous catalytic systems, especially those based on zeolite or microporous materials, the rate of diffusion of reagents and products within the particles can become decisive. The pronounced difference in diffusion rates between linear and branched isomers can lead to the appearance of internal concentration gradients inside the catalyst particles [30]. Consequently, the observed distribution of products reflects patterns of reaction kinetics and transfer resistance rather than true thermodynamic equilibrium. Deactivation of the catalyst further exacerbates deviations from equilibrium in industrial systems. Over time, the active centers may gradually become blocked due to the deposition of coke, highly adsorbed reaction intermediates, or impurities in the raw materials. This leads to a decrease in the number of available acid and metal centers, thereby reducing the overall catalytic activity and changing the balance between isomerization and competing side reactions. In addition, spatially uneven deactivation along the catalyst layer can cause axial fluctuations in activity, which further deviates the system from the equilibrium state. The presence of parallel side reactions, including cracking, hydrogenolysis, and aromatization, also plays an important role in limiting the achievement of equilibrium. These reactions compete directly with the isomerization process for the presence of reagents and intermediates and, as a rule, intensify at elevated temperatures and longer holding times. Under such conditions, the system can approach a steady state that differs significantly from the thermodynamically equilibrium composition [31]. The partial pressure of hydrogen indirectly affects the approach to equilibrium, although it does not directly participate in the stoichiometry of isomerization. Hydrogen plays a crucial role in stabilizing the metal sections responsible for the stages of hydrogenation and dehydrogenation, and in suppressing the formation of coke. Insufficient availability of hydrogen can contribute to the accumulation of olefins, thereby accelerating secondary reactions and increasing the deviation from equilibrium conditions. Finally, the hydrodynamics of the reactor and factors related to the design introduce additional imperfections [32]. In fixed-bed reactors, phenomena such as channel formation, axial dispersion, and radial temperature gradients can lead to local deviations from optimal operating conditions. These spatial inhomogeneities lead to the fact that sections of the catalyst layer operate in suboptimal modes, thereby preventing the achievement of general equilibrium in the system. In general, equilibrium constraints in alkane isomerization systems arise from a complex interaction of thermodynamic constraints, finite reaction kinetics, mass transfer resistances, catalyst deactivation, and competing reaction pathways. A comprehensive understanding of these deviations is necessary to develop accurate reactor models and optimize industrial processes aimed at maximizing the yield of high-octane branched isomers [33]. Conclusion. The catalytic isomerization of light alkanes (C4-C6) remains one of the most technologically significant processes in modern oil refining, playing a central role in the production of components for mixing high-octane gasoline. This process makes it possible to convert linear paraffinic hydrocarbons into their branched isomers, which have significantly improved anti-knock properties, while minimizing the formation of highly toxic aromatic compounds commonly associated with alternative enrichment methods such as catalytic reforming. This review shows that the process of alkane isomerization is regulated by a complex and interdependent combination of thermodynamic, kinetic, and catalytic factors. From a thermodynamic point of view, branched isomers are preferable to use at lower temperatures due to their higher internal stability and lower Gibbs free energy. On the contrary, an increase in temperature shifts the equilibrium composition towards less branched structures and at the same time increases the likelihood of undesirable secondary reactions. However, the practical implementation is significantly limited by the kinetics of the reaction, since sufficient activation energy is required for the formation of intermediate compounds of carbenium ions and subsequent structural rearrangements, which limits the possibility of carrying out a low-temperature process. The mechanistic analysis highlights the critical importance of bifunctional catalytic systems in which metallic regions contribute to the hydrogenation-dehydrogenation stages, while acidic regions contribute to the restructuring of the skeleton with the help of intermediate carbenium ions. The synergistic interaction between these two types of active centers determines both the catalytic activity and the selectivity of the product. However, the effectiveness of the catalyst is constantly affected by competing side reactions, including hydrocracking, aromatization and coking, which contribute to a decrease in selectivity and gradual deactivation of the catalyst. The key conclusion of this study is that real industrial systems rarely achieve true thermodynamic equilibrium. Significant deviations occur as a result of internal kinetic constraints, resistance to intra- and interparticle mass transfer in porous catalysts, imperfect reactor hydrodynamics, and gradual deactivation of the catalyst. Together, these factors determine the actual distribution of the product and, therefore, must be carefully considered when designing the reactor, expanding production and optimizing the technological process. In general, the efficient operation of isomerization plants requires an integrated approach combining thermodynamic analysis, detailed kinetic modeling, and advanced catalyst development technologies. Recent developments in the field of catalytic materials, reactor configurations, and computer modeling techniques have significantly improved the productivity and selectivity of the process. However, further research is still needed to achieve a more complete understanding of reaction systems at the molecular level and to develop catalysts with increased stability, activity, and selectivity in industrial environments. In conclusion, it should be noted that alkane isomerization is a mature but constantly evolving field of oil refining, in which continuous progress is mainly due to global demand for environmentally friendly fuels, increased energy efficiency and more environmentally friendly refining technologies.

1. Wei C. et al. Effect of metal-acid balance and textural modifications on hydroisomerization catalysts for n-alkanes. Fuel. 2022;315:122809. doi:10.1016/j.fuel.2021.122809

2. Tan Y. et al. Species and impacts of metal sites over bifunctional catalyst on long-chain n-alkane hydroisomerization: A review. Applied Catalysis A: General. 2021;611:117916. doi:10.1016/j.apcata.2020.117916

3. Cheng K. et al. Impact of spatial organization of bifunctional metal–zeolite catalysts on hydroisomerization of light alkanes. Angewandte Chemie International Edition. 2020;59:3592–3600. doi:10.1002/anie.201915080

4. Corma A. et al. Activation and conversion of alkanes in zeolite-type materials. Chemical Society Reviews. 2021;50:8511–8595. doi:10.1039/D0CS01459A

5. Potter M.E. et al. Butane isomerization as a diagnostic tool in solid acid catalyst design. Catalysts. 2020;10(9):1099. doi:10.3390/catal10091099

6. Liu L. et al. Construction of mesoporous zeolite catalysts for hydroisomerization of n-alkanes. Applied Catalysis A. 2020.

7. Zhao X. et al. SAPO-based catalysts for hydroisomerization of long-chain paraffins. Applied Catalysis A. 2020.

8. Lyu Y. et al. Metal–acid balance in Ni/SAPO-11 catalysts for n-hexane hydroisomerization. Fuel. 2020.

9. Besl H, Kossman W, Crowe TJ, Caracotsios M. Nontraditional optimization for isomer unit improves profits. Oil Gas J. 2019.

10.

10. Dudley / Malloy. Predictive modeling and optimization for an industrial Penex isomerization unit: a case study. Energy Fuels. 2020. doi:10.1021/ef502332k

11.

11. Akhari A, et al. Predictive modeling and optimization of naphtha isomerization using HYSYS simulation and kinetic analysis. Energy Fuels. 2022. doi:10.1021/ef502332k

12.

12. Brito A, et al. Kinetic behavior and deactivation modeling of Pt-Ni/mordenite catalysts in hydroisomerization reactions. Appl Catal A. (exact journal series on Pt-Ni/mordenite systems, 2022 literature cluster).

13.

13. Konchag S, et al. Kinetic modeling of C5-C6 isomerization over Pt/zeolite H catalysts under refinery conditions. Chem Eng J. (refinery-scale modeling literature, 2020-2023).

14.

14. Surla V, et al. Single-event kinetic modeling of C5-C6 isomerization over chlorinated alumina-based catalysts. React Chem Eng. 2021-2023 literature.

15.

15. Chekantsev A, et al. Detailed microkinetic modeling of hydroisomerization over bifunctional catalysts with multi-step reaction networks. Appl Catal A. 2023.

16.

16. Batalha N. et al. n-Hexadecane hydroisomerization over Pt-HBEA catalysts: metal–acid intimacy effects. Fuel. 2020.

17.

17. del Campo P. et al. Zeolite confinement effects in alkane activation and conversion. Chemical Society Reviews. 2021.

18.

18. Advancements in zeolite-based catalysts for isomerization of n-alkanes: mechanistic insights and future directions. Discover Applied Sciences. 2025. doi:10.1007/s42452-025-06842-4

19.

19. Catalytic hydroisomerization of n-paraffin hydrocarbons: a review. Jurnal Rekayasa Proses. 2021. doi:10.22146/jrekpros.67587

20.

20. Feedstock composition optimization at naphtha catalytic reforming and C5-C6 isomerization units with HYSYS Izomer Activ simulator. International Research Journal. 2023.

21.

21. Comparative characteristics of catalytic reforming technologies in Kazakhstan. Kazakhstan Journal for Oil & Gas Industry. 2024. doi:10.54859/kjogi108876

22.

22. Ali F, Nagy T. Investigation of kinetics of hydroisomerization of C5/C6 and C6/C7 alkanes. Hungarian Journal of Industry and Chemistry. 2011. doi:10.1515/394

23.

23. Isomerization of n-C5/C6 bioparaffins to gasoline components with high octane number. Energies. 2020;13(7):1672. doi:10.3390/en13071672

24.

24. Singh A, Tiwari S. Thermodynamic and kinetic analysis of paraffin isomerization: a review. Thermochimica Acta. 2020. doi:10.1016/j.jaap.2021.105340

25.

25. Martínez J., Zúñiga-Hinojosa M. A., Ruiz-Martínez R. S. A thermodynamic analysis of naphtha catalytic reforming reactions // Processes. – 2022. – Vol. 10, No. 2. – Article 313. – DOI: 10.3390/pr10020313.

26.

26. Tan Y., Wang X., Liu Z., и др. Species and impacts of metal sites over bifunctional catalyst // Applied Catalysis A: General. – 2021. – Vol. 611. – Article 117916. – DOI: 10.1016/j.apcata.2020.117916.

27.

27. Liu L., Zhang M., Wang L., и др. Construction of ordered mesopores outside MTT zeolite // Applied Catalysis A: General. – 2020. – Vol. 602. – Article 117664. – DOI: 10.1016/j.apcata.2020.117664.

28.

28. Cheng K., Kang J., King D. L., и др. Impact of spatial organization of bifunctional catalysts // Angewandte Chemie International Edition. – 2020. – Vol. 59. – P. 3592–3600. – DOI: 10.1002/anie.201915080.

29.

29. Hydro-isomerization of paraffinic waxes: mechanisms and catalysts. Energy & Fuels. 2020. doi:10.1016/j.fuproc.2009.01.006

30.

30. A comparative study of kinetic reaction schemes for C6 isomerization. Applied Sciences. 2023;15(8):4429. doi:10.3390/app15084429

31.

31. Valavarasu G, Sairam B. Light naphtha isomerization process: a review. Petroleum Science and Technology. 2023. doi:10.1080/10916466.2010.504931

32.

32. Naqvi SR, Bibi A, Naqvi M, et al. New trends in improving gasoline quality through isomerization. Applied Petrochemical Research. 2019. doi:10.1007/s13203-018-0204-y

33.

33. Thermodynamic and kinetic analysis of paraffin isomerization. Thermochimica Acta. 2020. doi:10.1557/s43579-022-00264-8