Controlled Preparation Of Large-Size Spherical Mesoporous Carbons And Their Applications

Due to the developed pore structure and rich surface chemistry, mesoporous carbons have good application prospects in the fields of adsorption, catalysis et al. With the ability of controlling the mesoporous structure, it can accurately tailor the mesopore for the specific application requirements. And compared to materials with other macroscopic shape, spherical materials have specific advantages such as high-fill capability, high flowability, high wear resistance and high strength, which are more favorable for commercial applications. Therefore, the study on preparation of spherical mesoporous carbons (SMCs) with controlled pore structure is of great significant.In this work, SMCs were prepared by a combined method of inverse suspension polymerization and hard template method using resorcinol (R)-formaldehyde (F) as carbon precursors and commercial colloidal silica sol as structural directing regents. The mixtures of RF sol and colloidal silica sol were inversely suspended in the liquid paraffin to form the hybrid hydrogel spheres. Then the spheres were directly dried at the ambient conditions, followed by the carbonization and the silica removal. The effects of process conditions such as the pre-polymerization time, the stirring speed and the precursor compositions such as the mass ratio of silica/RF were investigated. It was found that the particle sizes of SMCs can be tailored in the range of0.3-2mm, and it generally increased with the increase of pre-reactive time and decrease with the stirring speed. The specific surface areas (SBET), total pore volumes (Vt) increase with the increase of amounts of colloidal silica in the precursor. The silica sol nanoparticles with large particle size can result in large pore size and wide pore size distribution for the resulting SMCs. The SBET, Vt and average pore sizes of SMCs can be adjusted in the range of706-1031m2/g,1.56-3.89cm3/g,10-20nm respectively. The addition of melamine into the RF precursor can introduce0-7.22wt.%. nitrogen atoms onto the framework of the SMCs.The tannic acid (TA) adsorption behavior on SMCs was investigated. The results showed that the mesopore structure plays an important role in the adsorption process. TA adsorption capacity increase with the increase of SBET, Vt and nitrogen doping content of SMCs. The adsorption rate of TA was strongly depended on the particle size, showing an increasing tread with the decrease of particle size.The ammonia adsorption behavior on copper sulfate loaded SMCs was also investigated. The results showed that the SMCs had a limit adsorption capacity for ammonia themselves and the copper sulfate was the active component with several specific adsorption sites. Ammonia adsorption capacity increased with the increases of copper sulfate loading and reached the maximum at the loading of50%, then decreased while the loading further increased. Compared to the NaOH etching to remove the silica nanoparticles, the HF etching was more efficient. Furthermore, nitrogen doing was found to be unfavourable for ammonia adsorption.