Cinder supported K2CO3 as catalyst for biodiesel production

Abstract This study aims to explore cheap macroporous solid base catalyst with high transesterification efficiency. Cinder, as solid waste from coal burning industry, with natural macroporous structure and alkalinity, was served as the support for K 2 CO 3 to prepare solid base catalyst for biodiesel production. In the present paper, catalysts prepared in different conditions were characterized by base strength, BET surface area, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and the triglyceride (TG) conversion from the transesterification catalyzed by each catalyst was determined using high performance liquid chromatography (HPLC). The effects of various parameters such as concentration of K 2 CO 3 impregnating solution, catalyst loading, molar ratio of methanol to oil and reaction time on the activity of catalysts were investigated. A maximum TG conversion of 99.5% was obtained under the optimal conditions as catalyst amount of 17.4%, methanol/oil of 12:1 and reaction time of 1 h, which was catalyzed by the catalyst prepared with 0.50 g mL −1  K 2 CO 3 impregnating solution. The results indicated that K 2 CO 3 was decomposed into K 2 O by the catalysis of metal oxides in cinder or transformed into Al–O–K compounds through reaction with cinder. The formation of K 2 O and Al–O–K compounds should be the main reason for the catalytic activity. Continuous use of the catalyst in a tubular reactor showed high TG conversion (>90%) maintained 9 h. The deactivation of the catalyst after 9 h use was mainly caused by potassium leaching to the glycerol phase.