In summary, the novelty of this work are; 1) the influence of the molar ratio between resorcinol and sodium carbonate on the porosity of the catalyst is investigated; 2) it has been demonstrated that the sulfonation procedure is more effective if the carbon size is controlled;
3) not only the esterification reaction but also de transesterification reaction (biodiesel production) is performed more efficientlycontrolling the catalyst size; 4) The sulfonic group are strongly attached to the carbon being stable upon heating to 200 °C; 5) the sulfonation of
small porous carbonmicroparticles seems a suitablemethod to produce cheap and environmentally friendly heterogeneous acid catalysts combining a high surface area and an excellent catalytic performance (Scheme 1), thus making thismaterial a promising candidate for industrial scale production.