Analysis of the competitive reaction rates of dibenzothiophene and naphthalene in the hydrodenitrogenation of 1,2,3,4-tetrahydroquinoline over Pt-based catalysts

In hydrofining processes, the competitive interactions among sulfur-containing compounds, aromatic hydrocarbons, and nitrogen-containing intermediates fundamentally govern catalytic performance. Nevertheless, the complex kinetic relationships within hydrodenitrogenation (HDN) systems have remained unclear and insufficiently investigated. This research comprehensively and systematically examined the competitive reaction kinetics of naphthalene (an aromatic model) and dibenzothiophene (a sulfur-based model) during the HDN of 1,2,3,4 - tetrahydroquinoline over Pt-based catalysts. Through systematic analysis of conversion rates and product distributions across various reaction conditions, it demonstrated that both dibenzothiophene and naphthalene exert distinct inhibitory effects on HDN through mechanistically differentiated pathways. Quantitative evaluation revealed a pronounced temperature dependence in mitigating these inhibitory effects, whereas pressure variations exhibited negligible influence. These findings collectively demonstrate that surface adsorption competition, rather than hydrogen availability, dictates the reaction kinetics. Rigorous kinetic calculations and rate constant fittings identified the hydrogenation of 1,2,3,4-tetrahydroquinoline to decahydroquinoline as the rate-limiting step susceptible to competitive inhibition. This phenomenon predominantly arises from the tripartite competitive adsorption among naphthalene, dibenzothiophene, and 1,2,3,4-tetrahydroquinoline at catalytic active sites, as corroborated by theoretical adsorption energy calculations. Notably, the two inhibitors manifest divergent interaction mechanisms: H + ions generated during H 2 S formation in dibenzothiophene desulfurization facilitate C–N bond cleavage, whereas naphthalene directly suppresses this critical step. Furthermore, atomic-layer-deposited TiO 2 on Pt/Al 2 O 3 engineered the catalyst surface through three synergistic effects: enhanced nitrogen adsorption capacity, optimized hydrogen spillover pathways, and generation of additional C–N bond cleavage sites. This multi-effect strategy effectively reduces the negative impacts of competitive adsorption, emphasizing the crucial role of competitive reaction kinetics in designing sulfur/aromatic-resistant HDN catalysts.