Solid-Acid Catalyzed Acylation of Bio-Based Furan to 2-Acetylfuran: Mechanistic Insights into Selectivity Loss and Catalyst Deactivation Kinetics

Abstract

Furan is an important biorefinery platform molecule, and its Friedel–Crafts acylation with acetic anhydride (Ac2O) to yield 2-acetylfuran (AF) is a commercially relevant transformation with applications in pharmaceuticals and flavoring. However, developing solid-acid catalysts for this reaction is challenging owing to the propensity for side reactions producing high-molecular-weight oligomeric by-products, which progressively deactivate the catalyst and erode AF selectivity. In this work, a series of inorganic and organic polymer-based solid-acid catalysts were screened for furan acylation, and Amberlyst 15 (A15) was identified as superior in terms of both activity and selectivity. Systematic batch kinetic studies were subsequently conducted to determine the influence of temperature, catalyst loading, and furan-to-Ac2O molar ratio on catalytic performance. Semi-batch experiments under optimized conditions revealed a significant drop in AF yield and selectivity, indicating that AF self-condensation and cross-condensation of furan with AF are the dominant side reactions responsible for byproduct formation. Continuous reaction studies confirmed a progressive decline in A15 catalytic activity (∼30% over 6 h) with increasing reaction time, consistent with catalyst deactivation caused by oligomer deposition on active acid sites. A detailed kinetic model incorporating Eley–Rideal rate expressions for the main acylation and side reactions, together with a Langmuir-type catalyst deactivation function, was developed and validated against the experimental data, with all model parameters obtained with well-defined statistical confidence.