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Biodiesel from waste oil under mild conditions by a combination of calcium‐strontium oxide nanocatalyst and ultrasonic waves

The transesterification of waste oils to biodiesel was carried out in the presence and absence of ultrasound. A new nanocatalyst of the calcium‐strontium oxide was applied with high catalytic activity. The innovation of this work is an environmentally friendly synthesized nanocatalyst with ultrasound at low temperatures. After synthesis, the nanocatalyst was characterized with FESEM, FT‐IR, and CO2‐TPD, NH3‐TPD. It was mesoporous and showed great basicity by the CO2‐TPD method. The highest conversion of biodiesel was 99.2% under optimal reaction conditions (2.5 wt% nanocatalyst, oil to methanol molar ratio 1:6, time 40 minutes, temperature 35°C, and 42% amplitude of ultrasound). 1HNMR, FTIR, and GC‐FID tracked the characterization of biodiesel. The physical and fuel properties of biodiesel were evaluated according to the ASTM standardized method. Based on a kinetic study, the activation energy in the mechanical agitation method was about twice as high as in the ultrasonic method. A high turnover frequency and low environmental factors indicate that biodiesel synthesis from waste oil with this nanocatalyst is fast, efficient, and effective in the environment. Biodiesel was synthesized using calcium‐strontium oxide nanocatalyst, waste oil, and ultrasonic in a green and eco‐friendly process with time and cost savings.