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 CaCO3. The production of 1 ton of CaO catalyst resulted in 0.89 tons of CO2 emission, and every ton of the catalyst provided only 20 tons of biodiesel in non‐reusable manner. In this work, 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 H­2O as a by‐product instead of CO2. Amazingly, carbide slag – a waste – 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 CO2 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% CS600, 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%).