Synthesis of magnetic carbonaceous acids derived from hydrolysates of Jatropha hulls for catalytic biodiesel production

Abstract

A series of magnetic carbonaceous acids (JHC-T₁–T₂-SO₃H@Fe/Fe₃O₄) were synthesized by the assembly of nano-Fe₃O₄ magnetic cores (particle size < 20 nm) and carbon coatings derived from hydrolysates of Jatropha hulls. A magnetic JHC-12-600-SO₃H@Fe/Fe₃O₄ catalyst with a total acid content of 2.69 mmol g⁻¹ and a magnetic saturation of 40.3 A m² kg⁻¹ was successfully prepared via a sequence of hydrothermal precipitation, pyrolytic carbonization, and finally sulfonation with H₂SO₄. The catalyst was directly used for the production of biodiesel from Jatropha crude oil with an acid value (AV) of 17.2 mg KOH per g, and the optimized conditions (180 °C for 7.5 h with a molar ratio of methanol/oil of 18/1 and a catalyst loading of 7.5 wt%) were determined by single-factor tests. An average biodiesel yield of 95.9% was achieved with a recovery rate of 94.3% after 5 reaction cycles in a 5 L batch reactor for testing the feasibility of the catalyst for large-scale use. This study demonstrates an alternative green approach to fully utilizing waste biomass from energy plants in the catalytic synthesis of Jatropha biodiesel with high efficiency.