Waste‐Derived Catalyst for Biodiesel Manufacturing in CO₂‐Free Manner: Preparation, Catalytic Activity, and Reuse Studies

Abstract Currently, CaO‐based catalysts for biodiesel manufacturing are produced by calcination of available limestone ore consisting of CaCO 3 . The production of 1 ton of CaO catalyst resulted in 0.89 tons of CO 2 emission, and every ton of the catalyst provided only 20 tons of biodiesel in nonreusable manner. In this study, a CaO‐based catalyst was obtained by calcination of Ca(OH) 2 , a large‐tonnage waste from acetylene manufacturing via calcium carbide route (carbide slag), producing H 2 O as a by‐product instead of CO 2 . Amazingly, carbide slag‐a waste material‐was active in catalytic transesterification of soybean oil skipping calcination or any pretreatment steps and provided biodiesel in 28% yield. Moreover, biodiesel was obtained in 98% yield after catalyst calcination at 600 °C for at least 4 times accompanying zero CO 2 emission. The obtained catalysts were characterized by XRD, XRF, FTIR, TGA, SEM‐EDX, and BET surface area analysis. The best conversion of soybean oil was achieved using 1 wt% CS 600 , MeOH:oil ratio of 12:1, by boiling at 65 °C for 2 h. The catalyst reuse was found out using two approaches: “catalyst isolation” (5 cycles with yield ≥ 80%) and “fresh start” (up to 7–10 cycles with yield ≥ 80%).