Transesterification activity of modified biochars from spent malt rootlets using triacetin

Abstract

In this study, transesterification of triacetin was studied using biochar as a greener and environmentally friendly solid catalyst. Biochar and modified biochars were produced from spent malt rootlets with pyrolysis at 850 °C in limited oxygen atmosphere, treated with acid, base, or pure water, characterized with various physicochemical techniques, like N2 adsorption for the determination of Specific Surface Area, thermogravimetric analysis, Infra-Red spectroscopy, Xray powder diffraction and Potentiometric Mass Titration for the determination of acid-base behavior and tested for their transesterification activity. The physicochemical characterization of the biochars showed that the treatment had significant effect on the specific surface area, TGA curves and point of zero charge of the biochars. Treatment with NaOH results to a significant increase in point of zero charge of the biochar, removal of lignin and enrichment of Na on the surface of biochar. Treatment with H2SO4 increases the specific surface area and the microporosity, lowers the point of zero charge and removes almost completely the mineral deposits from the surface. It was found that the two most active biochars were the untreated and the treated with NaOH biochar. The transesterification activity is correlated well with the basicity of the samples. The activity of the biochars is similar to the activity obtained in homogenous catalysis and it is stable for at least 3 cycles. The results are promising and biochars from spent malt rootlets can be used in transesterification reaction for biofuels production.