Optimisation of Reaction Parameters of Fructose Dehydration into 5-Hydroxymethylfurfural Using Lewis Acid Hydrogel Catalysts: A Response Surface Methodology Approach

Recent discoveries shed light on 2,5-dimethylfuran (DMF) as a promising biofuel substitute for internal combustion engines. Hydrogenolysis can transform 5-hydroxymethylfurfural (5-HMF) into DMF, and 5-HMF is regarded as a platform chemical in biofuels and petrochemicals. Fructose, being more reactive, is the preferred precursor for 5-HMF synthesis using acid catalysts. While the PEGDA-3SMP-H Lewis acid hydrogel catalyst has been utilized for this conversion, statistical optimisation of reaction parameters remained. The present study aims to rectify this by employing response surface methodology and optimising key reaction parameters. A deep eutectic solvent (DES) medium was used for conducting the reaction, while high-performance liquid chromatography (HPLC) was used to analyse samples. The critical variables influencing 5-HMF yield from fructose dehydration by PEGDA-3SMP-H include reaction time, temperature, and fructose:catalyst ratio. Statistical techniques confirmed through a normal probability plot indicating a linear distribution of data points. Design-Expert software generates 3D surface and contour plots, illustrating the impact of reaction parameters on fructose conversion. Elevated temperature aids the reaction, but excessive time results in 5-HMF rehydration and the formation of side products. A low fructose:catalyst ratio favours 5-HMF production, while high ratios yield lower 5-HMF due to insufficient catalysts. Numerical optimisation pinpoints ideal parameters - temperature (125 °C), time (4.3 h), and fructose:catalyst ratio (2.7)—predicting a 56.91% 5-HMF yield. Experimental verification closely aligns with the model’s predictions, yielding 59.01%, affirming its robustness. This study enhances understanding of how key reaction parameters influence the yield of 5-HMF from fructose with the PEGDA-3SMP-H catalyst, providing valuable insights for biofuel synthesis.