Novel utilization of pyrolysis products produced from waste printed circuit boards: catalytic cracking and synthesis of graphite carbon

Debromination pyrolysis technology can decompose organics and remove bromide of waste printed circuit boards (WPCBs). However, the pyrolysis products which contain biphenyl, phenol and its homologues, benzene and furan are typical hazardous wastes. In order to support the promotion of pyrolysis technology, it is necessary to carry out harmless disposal and comprehensive utilization of pyrolysis products. In this study, catalytic cracking technique was utilized to refine pyrolysis products of WPCBs. Furthermore, the residual char absorbed on zeolites was used to prepare coated graphite carbon zeolites (CGCZ). The results showed that the compositions of cracking products were less 30 species. Besides, the yield of simple alkane and alkene (SAA) and phenols significantly increased at the optimal conditions (mass ratio of NMMs and zeolites of 1.0:2.0, reaction temperature of 750 degrees C, reaction time of 10 min and Ar flow rate of 15 mL/min). Moreover, the fused ring compounds in pyrolysis products could be adsorbed by zeolites and formed graphite carbon. The graphite carbon had interplanar spacing with 0.3657 nm and thickness of microcrystal with 1.61 nm, which indicated that the regular and ordered graphite structure was formed. Finally, the mechanism for catalytic cracking and forming CGCZ can be proposed as adsorption, catalytic and secondary cracking, cross-linking and polycondensation and the removal of hydrogen and hydroxy. This study provides an effective and sustainable method to utilize pyrolysis products, which broadens the way of rational utilization of complex organics. (C) 2019 Elsevier Ltd. All rights reserved.