Microwave-assisted carbon-based sulphonated melon seed peel catalyst development for the optimization of neem seed oil epoxidation using response surface methodology

Abstract

Pure neem seed oil (NSO) was epoxidized via in situ conventional method using hydrogen peroxide and acetic acid in the presence of a microwave-assisted carbon-based sulphonated melon seed peel catalyst (MACSMSPC). The MACSMSPC was prepared via a two-step process (carbonization and sulphonation) using a microwave. The characterization results from Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Micrograph (SEM), X-Ray Diffraction (XRD), Brunauer-Emmet-Teller (BET) and X-ray fluorescence analysis (XRF) confirms the successful -SO3H group attachment to the solid catalyst. The modelling and optimization studies of the epoxidation process of NSO were performed using Box Behnken design implementing Response Surface Methodology (RSM) with catalyst concentration, time and temperature as the independent factors and oxirane value as the dependent factor. The ANOVA showed a second-order polynomial model with an R2 value of 0.9901, Adj R2 of 0.9774 and Pred R2 of 0.8415, indicating the significant correlation between the experimental values and predicted responses. The 3D plots showed that the process parameters significantly impacted the oxirane value. The optimal oxirane value of 9.816% was obtained at a catalyst concentration of 0.6, reaction time of 4 h, reaction temperature of 50 °C with a desirability of 1.000. also, characterizations result via FT-IR and GCMS on the epoxy NSO indicate the oxirane ring's successful attachment on the NSO.