Effective conversion of rapeseed oil to biodiesel fuel in the presence of basic activated carbon catalysts

The heterogeneous base-catalysed transesterification of rapeseed oil was performed in the presence of modified activated carbons to obtain biodiesel fuel. The basic strength of the initial carbon sample was enhanced through its treatment with different N-containing agents such as gaseous ammonia, aniline, melamine, benzene-1,4-diamine, aminosilane, or guanidine derivatives. The materials obtained were characterised using elemental and textural analysis, potentiometric titration, NMR, XPS, and DTG measurements. The transesterification of rapeseed oil was performed with methanol in a batch reactor under elevated pressure at 130 degrees C. The superior activities in the reaction were shown by carbons modified with ammonia and by samples obtained via immobilization of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (guanidine derivative) on the carbon surface. The most active materials showed high total basicity and were able to efficiently catalyse the reaction, giving fatty acid methyl ester (FAME) yields comparable to those obtained in the process with NaOH used as a homogeneous catalyst. Reusability tests were also conducted.