Abstract: Against the dual backdrop of the transformation from oil refining to chemical engineering and the sustained growth in demand for high-purity benzene, the disproportionation process technology for producing more benzene from toluene has attracted attention. To explore the differences between the pure toluene disproportionation process and the toluene shape-selective disproportionation process, process simulation and optimization were carried out, and their impacts on downstream units were analyzed. The results show that the energy consumption of the pure toluene disproportionation process is 41% lower than that of the toluene shape-selective disproportionation process, and the energy consumption of the product separation unit accounts for as high as 85% of the total energy consumption. A heat-integration scheme with a dividing wall column was adopted to optimize the BTX product separation process, reducing the total heat load and total cooling load by 30.8% and 32.8%, respectively. When applied to the entire toluene disproportionation process, this optimization scheme reduced utility consumption, and the operating cost could be decreased by 10%—15%. Finally, based on the same toluene feed processing capacity, the impacts of mixed xylene products with different paraxylene (PX) concentrations produced by the two disproportionation technology routes on the downstream PX separation unit were compared. The results indicate that the energy consumption of the combined process with toluene shape-selective disproportionation is approximately 9% lower than that of the combined process with pure toluene disproportionation.

Key words: pure toluene disproportionation, toluene shape-selective disproportionation, dividing-wall column, heat integration, energy consumption