Synergistic effect on co-hydrogenation of coal-petroleum co-processing oil and washing oil from coal tar distillate

Hydrogenation of coal-petroleum co-processing oil (CPCO) and washing oil (WO) from coal tar distillate were performed separately, and the underlying synergistic effect for cyclanes formation during co-hydrogenation was examined. The results show that higher temperatures at 320–380 °C boosted cyclanes production by hydrogenation of polycyclic aromatic hydrocarbons (PAHs) in WO due to the enhanced formation of intermediate products (partially hydrogenated aromatics) that are difficult to proceed at lower temperatures (ΔG > 0). The cyclanes content in the co-hydrogenation product was higher than the theoretical value, verifying the synergistic effect in cyclanes formation during co-hydrogenation. The synergy was most prominent for co-hydrogenation at 340 °C and CPCO/WO ratio of 1:2. Similar to the case in the hydrogenation of WO, the cyclanes content increased with rising temperatures and reached 13 % (maximum values) at 380 °C during co-hydrogenation with CPCO/WO ratio of 1:2. Addition of hydrogen donor solvent further increased the cyclanes content to 16.8 % during co-hydrogenation, suggesting the hydrogenation of PAHs to cyclanes. Composition analysis of cyclanes from the hydrogenation products reveals the reason for the synergism, i.e., the H transfer from CPCO to WO promoted hydrogenation of PAHs into cyclanes thus rising cyclanes content in the co-hydrogenated products.