Crude Glycerol/Guishe Based Catalysts for Biodiesel Production: Conforming a Guishe Biorefinery

Biodiesel production imposes some challenges, such as the crude glycerol management and cleaning requirements of biodiesel produced by homogeneous transesterification. Heterogeneous catalysts based on residual biomass have been proposed to tackle these challenges; in addition, biomass revalorization is fundamental for biorefineries development. In this research, two organic wastes (crude glycerol and guise) are used to synthesize carbonaceous catalysts. Four catalysts, with different crude glycerol/guishe proportions, were prepared by pyrolysis at 800 and 900 °C, followed by a chemical functionalization with H2SO4. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and thermal gravimetric analysis (TGA) were used to characterize the catalysts. The performance of the catalysts was evaluated in a soybean oil transesterification reaction. The crude glycerol/guishe based catalysts lead to similar biodiesel yields than the obtained with a conventional homogeneous catalyst (CH3NaO). The catalyst identified as BS-25-8 (a mixture of 25% guishe and 75% crude glycerol, pyrolyzed at 800 °C and sulfonated), in a proportion of 1 wt%, achieved the highest fatty acid methyl esters (FAME) yield (99%) in the transesterification reaction, even surpassing the performance of the CH3NaO (yield of 93%).