Intensification of epoxidation of vegetable oils using oscillatory baffled reactors and 3D printing

Abstract

Epoxidised vegetable oils (EVOs) are widely used as plasticisers, stabilisers, and precursors for polyol synthesis in the polymer sector and other industries. Currently, the epoxidation is carried out in a semi-batch or batch reactor using peracids (peracetic or performic acid). The process is very exothermic, necessitating slow addition of hydrogen peroxide (HOOH) (usually over two hours) at a moderate temperature (60°C) to avoid thermal runaway. In practise, this leads to reaction times of eight hours or longer. In this study, rapeseed oil was epoxidised in a mesoscale oscillatory baffled reactor (“meso-OBR”), operating in continuous mode to determine the feasibility of this reactor design, as it will reduce the mass and heat transfer limitations. Whereas, 3D printing was used for rapid development of the meso-OBR design to further improve the performance. Batch epoxidation of rapeseed oil was initially performed and screened in a three necked jacketed reactor. The determination of iodine value (IV), iodine value changes (conversion) and epoxide formation (yield) were performed using standard titrimetric analysis. A rapid method was developed using Fourier Transform Infrared (FTIR) spectroscopy and validated using Nuclear Magnetic Resonance (NMR) spectroscopy. The FTIR method was shown to be rapid and straightforward for monitoring rapeseed oil epoxidation reactions. The batch reaction for the epoxidation of rapeseed oil was then converted into a continuous process using jacketed meso-OBRs. A higher molar ratio of acetic acid and HOOH to oil could be used because of the enhanced heat transfer characteristics of the reactor and higher surface area per unit volume of this type of reactor. The HPOBR was then shown to operate as passive jacketed reactor. Developments of the meso-OBR design were fabricated using 3D printing to investigate the influence of the baffle separation distance under various oscillation conditions (frequency and amplitude). The 3D-printed meso-OBR design also exhibited the reactor’s ability to operate continuously at a higher molar ratio of acetic acid and HOOH to oil at higher operating temperature (80°C) with a shorter hydraulic residence time (10 min). Due to the reduction in residence time and removal of the various inherent inefficiencies of the batch cycle, an OBR operating at the same production rate as the commercial batch reactor would be approximately 144 times smaller.