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 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 used condition for 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%. During catalyst reuse tests based on crude jupati oil, an abrupt drop in its catalytic activity was observed: around 65% for the second reaction cycle, when compared to the first cycle. We chose to use the same industrial waste as raw material and as an alternative adsorbent to remove the chlorophyll contaminant from crude jupati oil in order to synthesize sulfonated biochar from murumuru kernel shell biochar. With the synthesized material, it was possible to remove about 92.5% of the initial chlorophyll present (12.4 ppm). The results of the study on catalytic reuse for purified jupati oil showed that catalyst deactivation after the first reaction cycle occurred due to the high chlorophyll concentration of crude jupati oil. The catalyst achieved catalytic activity at around 80% in terms of ester content for the fourth cycle using the purified oil. 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. Additionally, successive reactions were performed with buriti oil, which has low chlorophyll concentration (close to 0.1 ppm). Thus, we could attest that the deactivation of sulfonated biochar occurs by means of chlorophyll adsorption during the first reaction cycle. The values of ester content for the study of catalyst reuse with buriti oil prove that no deactivation of the heterogeneous acid catalyst can be found in successive esterification-transesterification reactions using an oil source with low chlorophyll content since it maintains a performance and catalytic stability very similar to that found for the purified jupati oil investigated in this study. The catalytic activity of catalyst gradually decreases with reuse, maintained the catalytic activity around 80% of ester content until the fourth reaction cycle using purified jupati oil and buriti oil. This catalytic activity reduction is mainly attributed to the leaching of active sites (-SO₃H). The reusing and ester content results found in this study showed that the chlorophyll content plays a decisive role in the choice of lipid matrices for the biodiesel production, because this bioactive can deactivate catalytic sites by adsorption resulting in blocking of active sites, impairing the catalytic performance in successive reaction cycles for this type of catalyst (BASTOS et al., 2020).

BASTOS, R. R. C. et al. Optimization of biodiesel production using sulfonated carbon-based catalyst from an amazon agro-industrial waste. Energy Conversion and Management, v. 205, n. October 2019, p. 112457, 2020.