Effects of Reaction Atmospheres on Hydrogenation Selectivity of Bicyclic Aromatics on NiMoS Active Sites—Combining DFT Calculation and Experiments

During the pre-hydrotreatment process, the hydrogen sulfide and ammonia present in the reaction atmosphere affect the conversion rate of bicyclic aromatics and the retention rate of monocyclic aromatic hydrocarbons (RRMA). In this study, 1-Methylnaphthalene (1-MN) is used to investigate hydrogenation behavior on Ni-Mo-S active sites. The results indicate that at low conversion rates, 1-MN is preferentially converted to 5-methyltetrahydronaphthalene (5-MTHN) on the S-edge, and can be simultaneously converted to 1-methyltetrahydronaphthalene (1-MTHN) and 5- MTHN on the Mo-edge. Additionally, the H2S in the reaction atmosphere significantly competes with 1-MN for adsorption on the S-edge, limiting the hydrogenation selectivity of 5-MTHN, whereas NH3 preferentially competes with 1-MN on the Mo-edge. At a high1-MN conversion rate, the competitive adsorption of 1-MN and MTHN is concentrated on the S-edge. Conversely, at a low bicyclic aromatic conversion rate, H2S increases the RRMA, whereas NH3 significantly lowers it.