Ionic Liquid@Amphiphilic Silica Nanoparticles: Novel Catalysts for Converting Waste Cooking Oil to Biodiesel

The conversion of waste cooking oil (WCO) to biodiesel is promising in the green energy and sustainable development sector. In this study, ionic liquid@amphiphilic silica nanoparticles (IASNPs) combining the aspects of amphiphilic Pickering emulsions and acidic ionic liquids (ILs) were developed for green biodiesel production from the transesterification of WCO and methanol. Based on the interesting principle of interfacial catalysis in a Pickering emulsion, this novel catalyst could effectively promote the catalytic reaction occurring at the three-phase interface by constructing water-in-oil microdroplets (with each microdroplet being considered a microreactor) without any surfactant additives, considerably overcoming the disadvantage of limited mass-transfer ability in heterogeneous catalysis. This synergistic effect between the amphiphilic nature and IL acidic catalysis was well optimized during the construction of IASNPs, and the Box-Behnken response surface methodology was used to optimize the operating conditions of biodiesel production. The results showed that an ultrahigh biodiesel yield of 91.45% was obtained under optimum conditions, even without mechanical stirring. Furthermore, there was little loss of biodiesel yield after six cycles via simple centrifugation, validating its ease of recovery, robust catalytic stability, and low cost. Our work provides an important methodology and catalyst design tool for the green and sustainable reutilization of WCO.