Synthesis of 4-aminobenzenesulfonic acid functionalized carbon catalyst through diazonium salt reduction for biodiesel production

•Coal carbon catalysts are synthesized through diazonium salt reduction.•Carbon catalyst gains developed microstructure under chemical activation effect.•The maximum esterificaiton efficiency achieves 95.04%.•Carbon catalyst gains 4-sulfophenyl group density of 0.97 mmol g−1.•Active sites leaching accounts for the main reason for catalyst deactivation. A series of carbon catalysts are synthesized through the arylation diazonium salt reduction approach from coal to catalyze esterification of oleic acid with methanol for biodiesel production. Under the activated carbon preparation temperature of 900 °C, mass ratio of 4-aminobenzenesulfonic acid to activated carbon of 6 and arylation temperature of 45 °C, the synthesized carbon catalyst gains the surface area and pore volume of 629.3 m2 g−1 and 0.29 cm−3 g−1, respectively. Besides, the carbon catalyst possesses abundant and strong active sites with the 4-sulfophenyl group density of 0.97 mmol g−1 and acid strength of 0.8