Catalytic Systems and Mechanistic Insights into Crotonaldehyde Synthesis from Acetaldehyde: A Comprehensive Review

This paper systematically reviews the recent advances in catalytic systems and reaction mechanisms for the synthesis of crotonaldehyde via aldol condensation using acetaldehyde as the feedstock. Firstly, the structural characteristics, reactivity, and important applications of crotonaldehyde in fine chemicals are outlined, with particular emphasis on the limitations of traditional homogeneous base-catalyzed processes, such as difficulty in separation and environmental pollution caused by waste streams. On this basis, heterogeneous catalytic systems are discussed in detail, focusing on the progress of metal oxides, aluminosilicate zeolites, and heteroatom zeolites in regulating acid–base properties, active site structures, and reaction pathways. Furthermore, the typical carbanion mechanism and direct condensation mechanism in aldol condensation are summarized, and the catalyst deactivation and by-product formation mechanisms are analyzed. Finally, perspectives on the construction of efficient and green catalytic systems and future research directions are proposed, aiming to provide theoretical guidance for process optimization and catalyst design in crotonaldehyde synthesis from acetaldehyde.