Magnetically separable porous carbon nanospheres as solid acid catalysts

A novel solid acid material, magnetically separable and SO3H-functionalized porous carbon nanosphere, was facilely synthesized by a simple activation route. The SiO2 layer protected the magnetic core from dissolving during the process of activation with ZnCl2, and retained the highly magnetic property. The obtained materials were characterized by N2 adsorption–desorption technology and transmission electron microscopy, and the results indicated that this solid acid material possessed an excellent spherical morphology and a superior porosity with high surface area and large pore volume. The results of X-ray diffraction, fourier transform infrared spectra and energy dispersive X-ray spectra demonstrated the preservation of the magnetic core and the successful modification of –SO3H functional groups. The solid acid activated at a low temperature (400 °C) showed the highest acidity of 1.98 mmol H+ g−1, which was estimated by an indirect titration method. The high surface area, large pore volume and high acidity endued this solid acid material excellent catalytic performance for esterification and transesterification reaction. Besides, the solid acid catalyst possessed remarkable stability and recycling property.