Characterization of mesocarbon microbeads and their derivatives by IR, SEM and Roman spectroscopy

Two kinds of mesocarbon microbeads (indicated MCMB-A and -B), prepared from different coal tar pitch, as well as their derivatives obtained by butylation and solvent extraction subjected to ultrasonic irradiation, were investigated by infrared (IR) spectroscopy, scanning electron microscopy (SEM) and Raman spectroscopy. For IR spectroscopic analysis of these samples, MCMB-B and its derivatives both showed electron transition absorptions at near-IR region and aromaticities at C-H stretching region, stronger than those of MCMB-A and its derivatives. SEM observation suggested that MCMB-B seemed to be rich in free carbon, more than MCMB-A. These results indicated the difference in structural characteristics between two MCMB samples: it could be presumed that MCMB-B would have degree of condensation and graphitization higher than those of MCMB-A. This could account for the experimental results previously reported that MCMB-B is inferior to MCMB-A regarding catalytic reactivity in butylation and solvent extraction. SEM images also indicated that MCMB had a surface layer of about 1-1.5 μm. Raman spectra of the MCMB, before and after solvent extraction, suggested that MCMB had a graphitized carbon layer on the surface, higher than the inner carbon.