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UBC Theses and Dissertations

Developing biochar-based catalyst for biodiesel production Dehkhoda, Amir Mehdi


A biochar-based catalyst was successfully prepared by sulfonation of pyrolysis char with fuming sulphuric acid. Prepared catalyst was studied for its ability to catalyze transesterification of vegetable oils (i.e., Canola Oil) and esterification of free fatty acids (i.e., oleic acid) using methanol. Thus far, biochar-based catalyst has shown significant activity, >90% conversion, in esterification of FFAs while indicating limited activity for transesterification of triglyceride-based oils such as Canola Oil. The first step in catalyst development approach was to increase the transesterification activity through employing a stronger sulfonation procedure. The total acid density of the biochar-based catalyst increased by ~90 times resulting in significantly increased transesterification yield (i.e., from being almost negligible to ~9%). Further investigations on the biochar-based catalyst were conducted to determine the effect of sulfonation time (5 and 15 h) and surface area on the transesterification reaction. Two established activation techniques (i.e., chemical activation with KOH and the silica template method) have been utilized to develop the surface area and porosity of the biochar supports. The surface area of the biochar support increased from a typical 0.2 m²/g to over 600 m²/g. In the chemical activation method with KOH, the effect of activation temperature on the transesterification yield has been investigated. Three biochar-based catalysts with activated supports at three different temperatures (450, 675 and 875C) were prepared and compared for transesterification activity. The sulfonated catalysts were characterized using the following analyses: BET surface area, elemental analysis, total acid density, Fourier Transform Infra-Red (FT-IR) spectroscopy, and X-Ray Diffraction iii (XRD) spectroscopy. The catalyst supported on biochar activated at 675C resulted the maximum transesterification yield (18.9%). The reaction yield was dependent on both catalyst surface area and total acid density. The catalytic activity of the biochar-based catalyst with activated support at 675C remained significantly high for esterification of FFAs (conversion>97%). The structural study of the catalysts prepared from activated biochars at three different temperatures suggest that the higher activation temperatures cause an increasing re-orientation of the biochar’s carbon sheets towards a more graphite-like structure, causing a decrease (> 60%) in total acid density despite of the increase in surface area.

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