Synthesis of Novel Magnetic Carbon Microtube-Based Solid Acid and Its Catalytic Activities for Biodiesel Synthesis

Abstract

Novel magnetic carbon microtube-based solid acid was synthesized via the carbonization of FeCl3-doped willow catkin and benzenediazoniumsulfonate acid-based sulfonation. The biomass willow catkin provided the special microtube structure and the high surface area of 215 m2/g for the novel solid acid. The microtube structure was well conserved during the mild carbonization (400 °C) and sulfonation process. The large number of acidic sites (2.3 mmol/g) on the microtube surface was quite accessible to reactants. Its magnetic properties offered a simple separation process. The novel solid acid showed very high activity for biodiesel synthesis, using cooking oils as raw material, which gave a total yield of 99% and free fatty acid conversion of 98.7% under mild conditions (70 °C). The facile synthetic process, high activity, high stability, and high recovery simplicity were the main properties of the novel magnetic solid acid, which is one of the best choices for biodiesel synthesis.