Catalytic Epoxidation of Castor Oil Using Sulfate‐Impregnated ZSM ‐5 for Enhanced Oxirane Formation

This study investigates the reaction kinetics of castor oil epoxidation using sulfate‐impregnated ZSM‐5 as a heterogeneous catalyst, focusing on the effects of sulfuric acid concentration, impregnation temperature, and calcination temperature. Unlike most seed oils, castor oil is predominantly composed of ricinoleic acid‐rich triglycerides, which contain both an epoxidizable carbon–carbon double bond and a native hydroxyl group, providing a uniquely functional feedstock for producing hydroxyl‐bearing epoxides. A series of catalysts were synthesized via wet impregnation at varying temperatures (25°C, 45°C, and 65°C) and treated with different concentrations of sulfuric acid (0.3, 0.6, and 0.9 M), followed by calcination at 350°C, 450°C, and 550°C. The kinetics of the epoxidation reaction were studied using a pseudo‐first‐order model and validated through MATLAB‐based numerical modeling coupled with Simulated Annealing optimization. The optimal impregnation temperature was 25°C, achieving a rate constant of 0.014 min −1 and a conversion value, ln[1/(1 − X )], of 0.39. Despite a slightly higher coefficient of determination ( R 2 = 0.9958) at 45°C, the overall conversion was lower. The highest reaction rate ( k = 0.033 min −1 ) was observed at a sulfuric acid concentration of 0.6 M; however, the catalyst prepared using 0.3 M sulfuric acid exhibited the highest conversion, indicating better catalyst stability and performance. Regarding calcination, although 450°C yielded the fastest reaction ( k = 0.016 min −1 ), the highest conversion was recorded at 550°C, with an ln[1/(1 − X )] value of 0.41. MATLAB modeling further validated the system, demonstrating a strong correlation ( R 2 = 0.9447), with kinetic constants of k 1 = 0.0236, k 2 = 0.00293, k 3 = 0.01006, and k 4 = 0.0474 that adequately represented the experimental behavior. The concentration profiles confirmed the sequential conversion of reactants into intermediates and products. This study provides critical insights into the preparation–structure–performance relationship of sulfate‐impregnated ZSM‐5 catalysts for sustainable epoxidation processes.