The upgrading of ethanol into gasoline-range biofuels relies critically on efficient carbon–carbon coupling strategies, among which the Guerbet reaction and ethylene oligomerization pathways play central and complementary roles. This review focuses on these two mechanistic platforms as core routes for controlled carbon chain growth from ethanol-derived intermediates. The Guerbet reaction proceeds via a redox-neutral hydrogen-borrowing mechanism involving ethanol dehydrogenation, aldol condensation, dehydration, and subsequent hydrogenation to form higher alcohols such as n-butanol. Its bifunctional catalytic requirements—metal sites for reversible hydrogen transfer and basic sites for C–C coupling—enable atom-economical chain extension with minimized external hydrogen demand. Catalyst design principles emphasizing metal–base interfacial proximity, balanced basicity, and hydrothermal stability are discussed, alongside process intensification strategies including tandem reactor systems and water management. In contrast, ethylene oligomerization—following ethanol dehydration—proceeds predominantly through carbocation-mediated chain propagation within acidic porous frameworks, offering a petrochemically mature pathway to C5–C12 olefins and paraffins. The roles of Brønsted acidity, pore confinement, branching control, and coke suppression are analyzed in relation to gasoline selectivity. Together, these two upgrading paradigms illustrate how rational catalyst engineering and reaction network control can transform renewable ethanol into infrastructure-compatible hydrocarbon fuels.
Shaoji Xie (Fri,) studied this question.