Multifunctionalized Ordered Mesoporous Carbon as an Efficient and Stable Solid Acid Catalyst for Biodiesel Preparation

The hydrophobic surface of ordered mesoporous carbon (OMC) via a hard-template route is difficult to sulfonate, which limits its practical applications in solid acid catalysis. Here, we reported an OMC solid acid catalyst with large surface area and ordered mesostructure, as well as high acidity. The pretreatment of hard-template prepared OMC with H2O2 brought numerous hydrophilic groups onto the carbon surface, which are favorable for the modification of -SO3H groups by a followed sulfonation treating with sulfuric acid. The results of X-ray diffraction, N-2 adsorption-desorption, and transmission electron microscopy demonstrated the preservation of large surface area and ordered mesostructure. Infrared spectra indicated the successful modification of -SO3H groups and in the meantime suggested the existence of hydrophilic groups (-COOH and -OH). The acidity of catalyst estimated by an indirect titration method and the modified amount of -SO3H groups examined by energy dispersive spectra were 2.09 mmol H+ g(-1) and 1.86 mmol -SO3H g(-1), respectively. Such multifunctionalized OMC material with hydrophilic groups (-SO3H, -COOH, -OH) and the hydrophobic framework (polycyclic aromatic carbon) showed evidently improved catalytic activities for biodiesel production. Furthermore, its excellent stability and recycling property were demonstrated by five consecutive cycles.