B-COPNA resin formation from ethylene tar light fractions: Process development and mechanical exploration by molecular simulation

Abstract

Efficient utilization strategy of ethylene tar (ET), the main by-product of ethylene cracking unit, is urgently required to meet demands for modern petrochemical industry. On the other hand, condensed polynuclear aromatic resin of moderate condensation degree (B-COPNA) is a widely used carbon material due to its superb processability, the production of which is however seriously limited by high cost of raw materials. Under such context, an interesting strategy was proposed in this study for producing B-COPNA resin using crosslinked light fractions of ethylene tar (ETLF, boiling point < 260 °C) facilitated by molecular simulation. 1,4-Benzenedimethanol (PXG) was first selected as the crosslinking agent according to the findings of molecular simulation. The effects of operating conditions, including reaction temperature, crosslinking agent and catalyst content, on the softening point and yield of B-COPNA resin products were then investigated to optimize the process. The reaction mechanism of resin production was studied by analyzing the molecular structure and transition state of ETLF and crosslinking agent. It was shown that PXG exhibited a superior capacity of withdrawing electrons and higher electrophilic reactivity than other crosslinking agents. In addition to the highest yield and greatest heat properties, PXG-prepared resin contained most condensed aromatics. The corresponding optimized conditions of resin preparation were 180 °C, 1:1.9 (PXG:ETLF) and 3% (mass) of catalyst content with a resin yield of 78.57%. It was the electrophilic substitution reaction occurred between the ETLF and crosslinking agent molecules that was responsible for the resin formation according to the experimental characterization and molecular simulation. Hence, it was confirmed that the proposed strategy and demonstrated process can achieve a clean and high value-added utilization of ETLF via B-COPNA resin preparation, bringing huge economic value to the current petrochemical industry.