Acetic acid esterification by application of immobilized brønsted acidic ionic liquids, synthesis, characterization, and kinetic investigation

This study presents the synthesis and characterization of two ionic liquids, namely 1‐sulfobutyl‐3‐methylimidazolium hydrosulfate (IL-1) and 1‐butyl‐3‐ methylimidazoliumhy drosulfate (IL-2), followed by the development of task-specific immobilized ionic liquid catalysts (SIL-1 and SIL-2) through their immobilization onto SBA-15-SO3H using the impregnation method. Comprehensive characterization of these catalysts was performed employing various physicochemical techniques such as TEM, FTIR, BET, and DSC-TGA. The catalytic performance of SIL-1 and SIL-2 was evaluated in the synthesis of polyol ester via the esterification of acetic acid with trimethylolpropane. The impact of operating parameters including temperatures (ranging from 70 to 110 °C), molar ratio of acetic acid to TMP (ranging from 1:1 to 5:1), and catalyst loading (ranging from 1% to 9% by weight) was systematically investigated over a fixed reaction time of 8 hours. Analysis of the resulting products was conducted using FTIR and GC techniques. SIL-1 exhibited superior catalytic activity compared to SIL-2, achieving a total conversion rate of 92.10% under optimal reaction conditions. Trimethylolpropane diacetate yielded 35.47% of the products, contributing to a total yield of trimethylolpropane mono-, di and triacetate, which reached 72.6%. The supported ionic liquids maintained consistent catalytic performance over five consecutive runs with minimal activity decline. Additionally, a mathematical model elucidating the chemical kinetics of the esterification reaction was explored, encompassing three reversible series-parallel reaction mechanisms. The integration of experimental findings with theoretically forecasted values was achieved using the Lingo program, demonstrating the feasibility of the proposed kinetic model.