Optimization of biodiesel production using sulfonated carbon-based catalyst from an amazon agro-industrial waste

Murumuru kernel shell, an agro-industrial waste, was used as the precursor biomass in the synthesis of an acid biochar that was employed as a catalyst in the production of biodiesel originated from jupati oil. The response-surface methodology was based on a 2³ central composite design and it was used to obtain the best reaction conditions. The catalyst was synthesized from the carbonization of murumuru kernel shell, followed by sulfonation in concentrated sulfuric acid. It was characterized by an acid-base titration in order to determine total acid density, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), fourier transform infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TG). The best reaction conditions obtained in the optimization of temperature, catalyst concentration, and methanol/oil molar ratio in jupati biodiesel production were 135 °C, 6% and 30:1, respectively. It also reached an ester content of 91.8%. The chlorophyll present in jupati oil negatively influenced catalyst reuse because this bioactive deactivated the catalyst studied. This issue was solved by using an adsorbent from murumuru kernel shell to remove the chlorophyll, achieving a removal rate of 92.5%. Thus, proposing the acid solid from the murumuru kernel shell as a bifunctional material in the removal of chlorophyll from vegetable oils and acid catalysis for biodiesel production. Reusing the catalyst with purified jupati oil maintained the catalytic activity around 80% of ester content until the fourth reaction cycle. The progressive loss was little in the catalytic activity due to the leaching of acid sites. The reusing and ester content results found in this study showed the viability of using the agro-industrial waste of murumuru kernel shell as a precursor for the sustainable production of an efficient sulfonated-carbon catalyst for biodiesel production.