Mechanisms and characteristics of mesocarbon microbeads prepared by co-carbonization of coal tar pitch and direct coal liquefaction residue

Abstract

Abstract DCLR-P was prepared by direct coal liquefaction residue (DCLR) with ash removal. In the present experiments, mesocarbon microbeads (MCMBs) were prepared by co-carbonization of coal tar pitch (CTP) and DCLR-P. With the increase of DCLR-P content, the yield of MCMBs increased from 47.8% to 56.8%. At the same time, the particle sizes distribution of MCMBs was narrowed, resulting in the decrease of D90/D10 ratio from 154.88 to 6.53. The results showed that DCLR-P had a positive effect on the preparation of MCMBs. 1H-NMR, FTIR, SEM and XRD were used to analyze the mechanisms and characteristics of MCMBs prepared by co-carbonization of CTP and DCLR-P. The results showed that the Proton Donor Quality Index (PDQI) of DCLR-P was 13.32, significantly higher than that of CTP (0.83). This indicated that DCLR-P had more naphthenic structure than CTP, which leads to hydrogen transferring in polycondensation reaction. The aliphatic structure of DCLR-P can improve the solubility and fusibility of mesophase, thereby making the structure of MCMBs more structured. The microstructure of the graphitized MCMBs had a substantially parallel carbon layer useful for its electrical performance. The performance of graphitized MCMBs as a negative electrode material for Li-ion batteries was tested. The particle sizes, tap density, specific surface area and initial charge–discharge efficiency of graphitized MCMBs met the requirements of CMB-I in GB/T-24533-2009. However, the initial discharge capacity of graphitized MCMB was only 296.3 mA h g−1 due to the low degree of graphitization of MCMBs.

Keywords

• Mesocarbon microbeads
• Direct coal liquefaction residue
• Mechanisms
• Characteristics