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<p>This study explores the application of sulfate-impregnated ZSM-5, ZSM-5/H₂SO₄ as a solid acid catalyst for the epoxidation of castor oil using in situ generated peracetic acid. The catalyst was optimized using the one-factor-at-a-time (OFAT) method, with the best synthesis conditions determined to be an impregnation temperature of 25&#xa0;°C, sulfuric acid concentration of 0.3&#xa0;M, and calcination at 550&#xa0;°C. The sulfate-modified catalyst was prepared by wet impregnation of ZSM-5 with sulfuric acid, and its structure was confirmed via FTIR analysis, which showed a shift in the Si–O band from 1081 to 977&#xa0;cm⁻<sup>1</sup>, indicating successful incorporation of sulfate groups. The formation of a hierarchical porous structure enhanced reactant diffusion, leading to improved catalytic efficiency. XRD analysis confirmed that the crystalline framework of ZSM-5 remained intact after modification. Elemental analysis (EA) revealed a 3.35% increase in hydrogen content and a 0.78% reduction in carbon content compared to the initial composition, indicating the successful formation of Brønsted acid sites and effective pore activation through thermal treatment. These changes suggest that calcination not only promoted surface cleaning but also enhanced the accessibility of active sites, contributing to improved catalytic performance. Under the optimized reaction conditions of 65&#xa0;°C and a 1:1:1 molar ratio of castor oil, acetic acid, and hydrogen peroxide, the catalyst achieved a 61% conversion in 30&#xa0;min using 1 wt% of catalyst relative to castor oil. The catalyst retained approximately 50% of its initial activity after the first reuse cycle and further declined to around 22% by the fourth cycle. Despite the gradual drop in performance, these results are considered promising, especially given that no thermal regeneration was applied between cycles. This reuse strategy aligns with the principles of green chemistry and cleaner production by minimizing energy input, reducing waste, and simplifying the catalyst recovery process. Kinetic modeling using a hybrid approach that combines Particle Swarm Optimization (PSO) and Simulated Annealing (SA) demonstrated enhanced predictive accuracy, achieving a high coefficient of determination (<i>R</i><sup>2</sup> = 0.9537). This outperformed the use of PSO alone (<i>R</i><sup>2</sup> = 0.8485) and SA alone (<i>R</i><sup>2</sup> = 0.8459), indicating that the hybrid strategy offers a more reliable fit to the experimental data by effectively balancing global and local optimization capabilities. This work represents the first report on the use and detailed characterization of ZSM-5/H₂SO₄ for castor oil epoxidation, highlighting its potential as an efficient and recyclable solid acid catalyst.</p>

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Enhanced catalytic performance and recycling of sulfate-impregnated ZSM-5 in the epoxidation of castor oil

  • 期刊论文

  • 发表日期：

    2025年8月30日

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  • Mohammad Aathif Addli,
  • Mohd Jumain Jalil,
  • Maher M. Alrashed,
  • Intan Suhada Azmi,
  • Mohd Azmier Ahmad,
  • Siti Noor Hidayah Mustapha

摘要

This study explores the application of sulfate-impregnated ZSM-5, ZSM-5/H₂SO₄ as a solid acid catalyst for the epoxidation of castor oil using in situ generated peracetic acid. The catalyst was optimized using the one-factor-at-a-time (OFAT) method, with the best synthesis conditions determined to be an impregnation temperature of 25 °C, sulfuric acid concentration of 0.3 M, and calcination at 550 °C. The sulfate-modified catalyst was prepared by wet impregnation of ZSM-5 with sulfuric acid, and its structure was confirmed via FTIR analysis, which showed a shift in the Si–O band from 1081 to 977 cm⁻1, indicating successful incorporation of sulfate groups. The formation of a hierarchical porous structure enhanced reactant diffusion, leading to improved catalytic efficiency. XRD analysis confirmed that the crystalline framework of ZSM-5 remained intact after modification. Elemental analysis (EA) revealed a 3.35% increase in hydrogen content and a 0.78% reduction in carbon content compared to the initial composition, indicating the successful formation of Brønsted acid sites and effective pore activation through thermal treatment. These changes suggest that calcination not only promoted surface cleaning but also enhanced the accessibility of active sites, contributing to improved catalytic performance. Under the optimized reaction conditions of 65 °C and a 1:1:1 molar ratio of castor oil, acetic acid, and hydrogen peroxide, the catalyst achieved a 61% conversion in 30 min using 1 wt% of catalyst relative to castor oil. The catalyst retained approximately 50% of its initial activity after the first reuse cycle and further declined to around 22% by the fourth cycle. Despite the gradual drop in performance, these results are considered promising, especially given that no thermal regeneration was applied between cycles. This reuse strategy aligns with the principles of green chemistry and cleaner production by minimizing energy input, reducing waste, and simplifying the catalyst recovery process. Kinetic modeling using a hybrid approach that combines Particle Swarm Optimization (PSO) and Simulated Annealing (SA) demonstrated enhanced predictive accuracy, achieving a high coefficient of determination (R2 = 0.9537). This outperformed the use of PSO alone (R2 = 0.8485) and SA alone (R2 = 0.8459), indicating that the hybrid strategy offers a more reliable fit to the experimental data by effectively balancing global and local optimization capabilities. This work represents the first report on the use and detailed characterization of ZSM-5/H₂SO₄ for castor oil epoxidation, highlighting its potential as an efficient and recyclable solid acid catalyst.