Study of the activity and stability of sulfonated carbon catalyst from agroindustrial waste in biodiesel production: Influence of pyrolysis temperature on functionalization

Abstract

The influence of pyrolysis temperature on the activity and catalytic stability of sulfonated biochar, from the agro-industrial residue murumuru kernel shell, was evaluated in the esterification reaction. Carbonaceous materials were synthesized by direct pyrolysis at 450, 600 and 750 °C and functionalized with sulfuric acid at 200 °C for a 4 h period. The materials were characterized by density of sulfonic groups, SEM, EDS, Elementary Analysis, ATR-FTIR, Raman Spectroscopy, TG and XPS analysis. The data obtained showed that the functionalization occurred directly in the carbon chain of biochar, evidencing that higher carbonization temperatures resulted in carbonaceous catalysts of more stable polycondensed nature. The catalyst synthesized at 750 °C achieved conversion of 98.35% ± 1.105 and maintained in the third reaction cycle conversion of 89.35% ± 1.197. This catalyst also showed the highest content of sulfur groups, even after reuse processes. The increment of temperature and time in the reaction medium was able to improve the reuse capacity of relatively low stability catalysts. Thus, the results obtained show the impact of pyrolysis temperature on obtaining catalysts with greater activity and catalytic stability in esterification reactions, and in this way provide very important subsidies for the development of new heterogeneous sulfonated carbon-based catalysts, applied in the biodiesel production process.