Biodiesel production from waste cooking oil using calcined scallop shell as catalyst

• Calcined scallop shell was used as low-cost and effective catalyst for biodiesel production.
• BDF yield from waste cooking oil reached 86% at 65 °C with a catalyst loading amount of 5 wt%.
• Calcined scallop shell showed good reusability.
• Calcium glyceroxide played an important role on the reusability of calcined scallop shell.
• Water in the waste cooking oil had negative effect on the catalytic activity of calcined scallop shell.

Transesterification of waste cooking oil (WCO) and methanol by using calcined scallop shell (CSS) as catalyst was carried out in a closed system for biodiesel fuel (BDF) production. It is found that the optimum calcination temperature for the preparation of CSS was 1000 °C. The effects of transesterification temperature, reaction time, methanol/oil molar ratio and catalyst loading amount on the BDF yield were investigated. Compared with the commercial CaO, CSS showed higher catalytic activity and the BDF yield reached 86% at 65 °C with a catalyst loading amount of 5 wt% (WCO basis) and a reaction time of 2 h. The catalyst was reused for 5 cycles whilst the BDF yield decreased 23%. It is found that CaO in CSS was transferred to calcium glyceroxide after the transesterification reaction, and calcium glyceroxide also showed good catalytic activity and reusability. Furthermore, Water content in WCO had negative effect on BDF yield. It is found that BDF yield reduced 15% due to the occurring of saponification when the water content was increased from 0.64% to 2.48%. It is expected that CCS can be used as an alternative and cheap catalyst for the biodiesel production.

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