Waste carbide slag as a solid base catalyst for effective synthesis of biodiesel via transesterification of soybean oil with methanol

•Calcined carbide slag showed good activity in transesterification of soybean oil.•91.3% FAME yield was achieved with TOF of 182.6 gFAME gcat− 1 h− 1.•Strong basicity was responsible for the high catalytic activity.•Waste carbide slag has promising application in biodiesel production.

A highly efficient solid base catalyst was prepared from waste carbide slag and tested for biodiesel production from soybean oil with methanol. The effect of calcination temperature for carbide slag and various reaction parameters on the catalytic performances was systematically investigated. The carbide slag waste calcined at 650 °C (CS-650) exhibited 91.3% yield of fatty acid methyl esters (FAME) at reaction temperature of 65 °C, methanol/oil molar ratio of 9, catalyst/oil mass ratio of 1.0 wt.% within a short reaction time of 30 min, which was much higher than that of commercial CaO. Furthermore, the relationship between the surface basicity and activity indicated that stronger basicity was responsible for the higher catalytic activity. The merits of high catalytic activity, low cost, and abundant storage make the waste carbide slag a promising catalyst in the production of biodiesel.

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