Catalytic isomerization of light alkanes: thermodynamic, kinetic, and technological aspects

Nurkhan S. Orazbayev, Gaini Zh. Seitenova

2026

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DOI 10.54859/kjogi108984
Data confidence 70 medium
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Abstract

The gradual tightening of environmental standards, combined with growing global demand for environmentally friendly fuels, has significantly increased the importance of advanced 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 numbers. 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 sites, reflecting the well-established mechanism of acid-catalyzed hydrocarbon transformations. Furthermore, the thermodynamic constraints governing the equilibrium distribution of isomers, as well as the kinetic factors influencingreaction rate, product selectivity, and overall process efficiency, are critically analyzed. Special emphasis is placed on bifunctional catalytic systems combining metal and acid functions, enabling the simultaneous hydrogenation–dehydrogenation and skeletal 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 condition.